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Posted to dev@flink.apache.org by Piotr Nowojski <pi...@ververica.com> on 2019/05/28 09:28:32 UTC
Re: [DISCUSS] FLIP-33: Standardize connector metrics
Hi,
Thanks for the proposal and driving the effort here Becket :) I’ve read through the FLIP-33 [1], and here are couple of my thoughts.
Big +1 for standardising the metric names between connectors, it will definitely help us and users a lot.
Issues/questions/things to discuss that I’ve thought of:
1a. If we are about to duplicate some metrics, can this become a performance issue?
1b. Generally speaking, we should make sure that collecting those metrics is as non intrusive as possible, especially that they will need to be updated once per record. (They might be collected more rarely with some overhead, but the hot path of updating it per record will need to be as quick as possible). That includes both avoiding heavy computation on per record path: histograms?, measuring time for time based metrics (per second) (System.currentTimeMillis() depending on the implementation can invoke a system call)
2. It would be nice to have metrics, that allow us to check the cause of back pressure:
a) for sources, length of input queue (in bytes? Or boolean hasSomethingl/isEmpty)
b) for sinks, length of output queue (in bytes? Or boolean hasSomething/isEmpty)
a) is useful in a scenario when we are processing backlog of records, all of the internal Flink’s input/output network buffers are empty, and we want to check whether the external source system is the bottleneck (source’s input queue will be empty), or if the Flink’s connector is the bottleneck (source’s input queues will be full).
b) similar story. Backlog of records, but this time all of the internal Flink’s input/ouput network buffers are full, and we want o check whether the external sink system is the bottleneck (sink output queues are full), or if the Flink’s connector is the bottleneck (sink’s output queues will be empty)
It might be sometimes difficult to provide those metrics, so they could be optional, but if we could provide them, it would be really helpful.
Piotrek
[1] https://cwiki.apache.org/confluence/display/FLINK/FLIP-33:+Standardize+Connector+Metrics <https://cwiki.apache.org/confluence/display/FLINK/FLIP-33:+Standardize+Connector+Metrics>
> On 24 Apr 2019, at 13:28, Stephan Ewen <se...@apache.org> wrote:
>
> I think this sounds reasonable.
>
> Let's keep the "reconfiguration without stopping the job" out of this,
> because that would be a super big effort and if we approach that, then in
> more generic way rather than specific to connector metrics.
>
> I would suggest to look at the following things before starting with any
> implementation work:
>
> - Try and find a committer to support this, otherwise it will be hard to
> make progress
> - Start with defining a smaller set of "core metrics" and extend the set
> later. I think that is easier than now blocking on reaching consensus on a
> large group of metrics.
> - Find a solution to the problem Chesnay mentioned, that the "records in"
> metric is somehow overloaded and exists already in the IO Metric group.
>
>
> On Mon, Mar 25, 2019 at 7:16 AM Becket Qin <be...@gmail.com> wrote:
>
>> Hi Stephan,
>>
>> Thanks a lot for the feedback. All makes sense.
>>
>> It is a good suggestion to simply have an onRecord(numBytes, eventTime)
>> method for connector writers. It should meet most of the requirements,
>> individual
>>
>> The configurable metrics feature is something really useful, especially if
>> we can somehow make it dynamically configurable without stopping the jobs.
>> It might be better to make it a separate discussion because it is a more
>> generic feature instead of only for connectors.
>>
>> So in order to make some progress, in this FLIP we can limit the discussion
>> scope to the connector related items:
>>
>> - the standard connector metric names and types.
>> - the abstract ConnectorMetricHandler interface
>>
>> I'll start a separate thread to discuss other general metric related
>> enhancement items including:
>>
>> - optional metrics
>> - dynamic metric configuration
>> - potential combination with rate limiter
>>
>> Does this plan sound reasonable?
>>
>> Thanks,
>>
>> Jiangjie (Becket) Qin
>>
>> On Sat, Mar 23, 2019 at 5:53 AM Stephan Ewen <se...@apache.org> wrote:
>>
>>> Ignoring for a moment implementation details, this connector metrics work
>>> is a really good thing to do, in my opinion
>>>
>>> The questions "oh, my job seems to be doing nothing, I am looking at the
>> UI
>>> and the 'records in' value is still zero" is in the top three support
>>> questions I have been asked personally.
>>> Introspection into "how far is the consumer lagging behind" (event time
>>> fetch latency) came up many times as well.
>>>
>>> So big +1 to solving this problem.
>>>
>>> About the exact design - I would try to go for the following properties:
>>>
>>> - keep complexity of of connectors. Ideally the metrics handler has a
>>> single onRecord(numBytes, eventTime) method or so, and everything else is
>>> internal to the handler. That makes it dead simple for the connector. We
>>> can also think of an extensive scheme for connector specific metrics.
>>>
>>> - make it configurable on the job it cluster level which metrics the
>>> handler internally creates when that method is invoked.
>>>
>>> What do you think?
>>>
>>> Best,
>>> Stephan
>>>
>>>
>>> On Thu, Mar 21, 2019 at 10:42 AM Chesnay Schepler <ch...@apache.org>
>>> wrote:
>>>
>>>> As I said before, I believe this to be over-engineered and have no
>>>> interest in this implementation.
>>>>
>>>> There are conceptual issues like defining a duplicate
>> numBytesIn(PerSec)
>>>> metric that already exists for each operator.
>>>>
>>>> On 21.03.2019 06:13, Becket Qin wrote:
>>>>> A few updates to the thread. I uploaded a patch[1] as a complete
>>>>> example of how users can use the metrics in the future.
>>>>>
>>>>> Some thoughts below after taking a look at the AbstractMetricGroup
>> and
>>>>> its subclasses.
>>>>>
>>>>> This patch intends to provide convenience for Flink connector
>>>>> implementations to follow metrics standards proposed in FLIP-33. It
>>>>> also try to enhance the metric management in general way to help
>> users
>>>>> with:
>>>>>
>>>>> 1. metric definition
>>>>> 2. metric dependencies check
>>>>> 3. metric validation
>>>>> 4. metric control (turn on / off particular metrics)
>>>>>
>>>>> This patch wraps |MetricGroup| to extend the functionality of
>>>>> |AbstractMetricGroup| and its subclasses. The
>>>>> |AbstractMetricGroup| mainly focus on the metric group hierarchy, but
>>>>> does not really manage the metrics other than keeping them in a Map.
>>>>>
>>>>> Ideally we should only have one entry point for the metrics.
>>>>>
>>>>> Right now the entry point is |AbstractMetricGroup|. However, besides
>>>>> the missing functionality mentioned above, |AbstractMetricGroup|
>> seems
>>>>> deeply rooted in Flink runtime. We could extract it out to
>>>>> flink-metrics in order to use it for generic purpose. There will be
>>>>> some work, though.
>>>>>
>>>>> Another approach is to make |AbstractMetrics| in this patch as the
>>>>> metric entry point. It wraps metric group and provides the missing
>>>>> functionalities. Then we can roll out this pattern to runtime
>>>>> components gradually as well.
>>>>>
>>>>> My first thought is that the latter approach gives a more smooth
>>>>> migration. But I am also OK with doing a refactoring on the
>>>>> |AbstractMetricGroup| family.
>>>>>
>>>>>
>>>>> Thanks,
>>>>>
>>>>> Jiangjie (Becket) Qin
>>>>>
>>>>> [1] https://github.com/becketqin/flink/pull/1
>>>>>
>>>>> On Mon, Feb 25, 2019 at 2:32 PM Becket Qin <becket.qin@gmail.com
>>>>> <ma...@gmail.com>> wrote:
>>>>>
>>>>> Hi Chesnay,
>>>>>
>>>>> It might be easier to discuss some implementation details in the
>>>>> PR review instead of in the FLIP discussion thread. I have a
>> patch
>>>>> for Kafka connectors ready but haven't submitted the PR yet.
>>>>> Hopefully that will help explain a bit more.
>>>>>
>>>>> ** Re: metric type binding
>>>>> This is a valid point that worths discussing. If I understand
>>>>> correctly, there are two points:
>>>>>
>>>>> 1. Metric type / interface does not matter as long as the metric
>>>>> semantic is clearly defined.
>>>>> Conceptually speaking, I agree that as long as the metric
>> semantic
>>>>> is defined, metric type does not matter. To some extent, Gauge /
>>>>> Counter / Meter / Histogram themselves can be think of as some
>>>>> well-recognized semantics, if you wish. In Flink, these metric
>>>>> semantics have their associated interface classes. In practice,
>>>>> such semantic to interface binding seems necessary for different
>>>>> components to communicate. Simply standardize the semantic of
>> the
>>>>> connector metrics seems not sufficient for people to build
>>>>> ecosystem on top of. At the end of the day, we still need to have
>>>>> some embodiment of the metric semantics that people can program
>>>>> against.
>>>>>
>>>>> 2. Sometimes the same metric semantic can be exposed using
>>>>> different metric types / interfaces.
>>>>> This is a good point. Counter and Gauge-as-a-Counter are pretty
>>>>> much interchangeable. This is more of a trade-off between the
>> user
>>>>> experience of metric producers and consumers. The metric
>> producers
>>>>> want to use Counter or Gauge depending on whether the counter is
>>>>> already tracked in code, while ideally the metric consumers only
>>>>> want to see a single metric type for each metric. I am leaning
>>>>> towards to make the metric producers happy, i.e. allow Gauge /
>>>>> Counter metric type, and the the metric consumers handle the type
>>>>> variation. The reason is that in practice, there might be more
>>>>> connector implementations than metric reporter implementations.
>> We
>>>>> could also provide some helper method to facilitate reading from
>>>>> such variable metric type.
>>>>>
>>>>>
>>>>> Just some quick replies to the comments around implementation
>>>> details.
>>>>>
>>>>> 4) single place where metrics are registered except
>>>>> connector-specific
>>>>> ones (which we can't really avoid).
>>>>>
>>>>> Register connector specific ones in a single place is actually
>>>>> something that I want to achieve.
>>>>>
>>>>> 2) I'm talking about time-series databases like Prometheus.
>> We
>>>>> would
>>>>> only have a gauge metric exposing the last fetchTime/emitTime
>>>>> that is
>>>>> regularly reported to the backend (Prometheus), where a user
>>>>> could build
>>>>> a histogram of his choosing when/if he wants it.
>>>>>
>>>>> Not sure if such downsampling works. As an example, if a user
>>>>> complains that there are some intermittent latency spikes (maybe
>> a
>>>>> few records in 10 seconds) in their processing system. Having a
>>>>> Gauge sampling instantaneous latency seems unlikely useful.
>>>>> However by looking at actual 99.9 percentile latency might help.
>>>>>
>>>>> Thanks,
>>>>>
>>>>> Jiangjie (Becket) Qin
>>>>>
>>>>>
>>>>> On Fri, Feb 22, 2019 at 9:30 PM Chesnay Schepler
>>>>> <chesnay@apache.org <ma...@apache.org>> wrote:
>>>>>
>>>>> Re: over complication of implementation.
>>>>>
>>>>> I think I get understand better know what you're shooting
>> for,
>>>>> effectively something like the OperatorIOMetricGroup.
>>>>> But still, re-define setupConnectorMetrics() to accept a set
>>>>> of flags
>>>>> for counters/meters(ans _possibly_ histograms) along with a
>>>>> set of
>>>>> well-defined Optional<Gauge<?>>, and return the group.
>>>>>
>>>>> Solves all issues as far as i can tell:
>>>>> 1) no metrics must be created manually (except Gauges, which
>>> are
>>>>> effectively just Suppliers and you can't get around this),
>>>>> 2) additional metrics can be registered on the returned
>> group,
>>>>> 3) see 1),
>>>>> 4) single place where metrics are registered except
>>>>> connector-specific
>>>>> ones (which we can't really avoid).
>>>>>
>>>>> Re: Histogram
>>>>>
>>>>> 1) As an example, whether "numRecordsIn" is exposed as a
>>>>> Counter or a
>>>>> Gauge should be irrelevant. So far we're using the metric
>> type
>>>>> that is
>>>>> the most convenient at exposing a given value. If there is
>>>>> some backing
>>>>> data-structure that we want to expose some data from we
>>>>> typically opt
>>>>> for a Gauge, as otherwise we're just mucking around with the
>>>>> Meter/Counter API to get it to match. Similarly, if we want
>> to
>>>>> count
>>>>> something but no current count exists we typically added a
>>>>> Counter.
>>>>> That's why attaching semantics to metric types makes little
>>>>> sense (but
>>>>> unfortunately several reporters already do it); for
>>>>> counters/meters
>>>>> certainly, but the majority of metrics are gauges.
>>>>>
>>>>> 2) I'm talking about time-series databases like Prometheus.
>> We
>>>>> would
>>>>> only have a gauge metric exposing the last fetchTime/emitTime
>>>>> that is
>>>>> regularly reported to the backend (Prometheus), where a user
>>>>> could build
>>>>> a histogram of his choosing when/if he wants it.
>>>>>
>>>>> On 22.02.2019 13:57, Becket Qin wrote:
>>>>>> Hi Chesnay,
>>>>>>
>>>>>> Thanks for the explanation.
>>>>>>
>>>>>> ** Re: FLIP
>>>>>> I might have misunderstood this, but it seems that "major
>>>>> changes" are well
>>>>>> defined in FLIP. The full contents is following:
>>>>>> What is considered a "major change" that needs a FLIP?
>>>>>>
>>>>>> Any of the following should be considered a major change:
>>>>>>
>>>>>> - Any major new feature, subsystem, or piece of
>>>>> functionality
>>>>>> - *Any change that impacts the public interfaces of the
>>>>> project*
>>>>>>
>>>>>> What are the "public interfaces" of the project?
>>>>>>
>>>>>>
>>>>>>
>>>>>> *All of the following are public interfaces *that people
>>>>> build around:
>>>>>>
>>>>>> - DataStream and DataSet API, including classes related
>>>>> to that, such as
>>>>>> StreamExecutionEnvironment
>>>>>>
>>>>>>
>>>>>> - Classes marked with the @Public annotation
>>>>>>
>>>>>>
>>>>>> - On-disk binary formats, such as
>> checkpoints/savepoints
>>>>>>
>>>>>>
>>>>>> - User-facing scripts/command-line tools, i.e.
>>>>> bin/flink, Yarn scripts,
>>>>>> Mesos scripts
>>>>>>
>>>>>>
>>>>>> - Configuration settings
>>>>>>
>>>>>>
>>>>>> - *Exposed monitoring information*
>>>>>>
>>>>>>
>>>>>> So any monitoring information change is considered as
>> public
>>>>> interface, and
>>>>>> any public interface change is considered as a "major
>>> change".
>>>>>>
>>>>>>
>>>>>> ** Re: over complication of implementation.
>>>>>>
>>>>>> Although this is more of implementation details that is not
>>>>> covered by the
>>>>>> FLIP. But it may be worth discussing.
>>>>>>
>>>>>> First of all, I completely agree that we should use the
>>>>> simplest way to
>>>>>> achieve our goal. To me the goal is the following:
>>>>>> 1. Clear connector conventions and interfaces.
>>>>>> 2. The easiness of creating a connector.
>>>>>>
>>>>>> Both of them are important to the prosperity of the
>>>>> connector ecosystem. So
>>>>>> I'd rather abstract as much as possible on our side to make
>>>>> the connector
>>>>>> developer's work lighter. Given this goal, a static util
>>>>> method approach
>>>>>> might have a few drawbacks:
>>>>>> 1. Users still have to construct the metrics by themselves.
>>>>> (And note that
>>>>>> this might be erroneous by itself. For example, a customer
>>>>> wrapper around
>>>>>> dropwizard meter maybe used instead of MeterView).
>>>>>> 2. When connector specific metrics are added, it is
>>>>> difficult to enforce
>>>>>> the scope to be the same as standard metrics.
>>>>>> 3. It seems that a method proliferation is inevitable if we
>>>>> want to apply
>>>>>> sanity checks. e.g. The metric of numBytesIn was not
>>>>> registered for a meter.
>>>>>> 4. Metrics are still defined in random places and hard to
>>>> track.
>>>>>>
>>>>>> The current PR I had was inspired by the Config system in
>>>>> Kafka, which I
>>>>>> found pretty handy. In fact it is not only used by Kafka
>>>>> itself but even
>>>>>> some other projects that depend on Kafka. I am not saying
>>>>> this approach is
>>>>>> perfect. But I think it worths to save the work for
>>>>> connector writers and
>>>>>> encourage more systematic implementation. That being said,
>> I
>>>>> am fully open
>>>>>> to suggestions.
>>>>>>
>>>>>>
>>>>>> Re: Histogram
>>>>>> I think there are two orthogonal questions around those
>>>> metrics:
>>>>>>
>>>>>> 1. Regardless of the metric type, by just looking at the
>>>>> meaning of a
>>>>>> metric, is generic to all connectors? If the answer is yes,
>>>>> we should
>>>>>> include the metric into the convention. No matter whether
>> we
>>>>> include it
>>>>>> into the convention or not, some connector implementations
>>>>> will emit such
>>>>>> metric. It is better to have a convention than letting each
>>>>> connector do
>>>>>> random things.
>>>>>>
>>>>>> 2. If a standard metric is a histogram, what should we do?
>>>>>> I agree that we should make it clear that using histograms
>>>>> will have
>>>>>> performance risk. But I do see histogram is useful in some
>>>>> fine-granularity
>>>>>> debugging where one do not have the luxury to stop the
>>>>> system and inject
>>>>>> more inspection code. So the workaround I am thinking is to
>>>>> provide some
>>>>>> implementation suggestions. Assume later on we have a
>>>>> mechanism of
>>>>>> selective metrics. In the abstract metrics class we can
>>>>> disable those
>>>>>> metrics by default individual connector writers does not
>>>>> have to do
>>>>>> anything (this is another advantage of having an
>>>>> AbstractMetrics instead of
>>>>>> static util methods.)
>>>>>>
>>>>>> I am not sure I fully understand the histogram in the
>>>>> backend approach. Can
>>>>>> you explain a bit more? Do you mean emitting the raw data,
>>>>> e.g. fetchTime
>>>>>> and emitTime with each record and let the histogram
>>>>> computation happen in
>>>>>> the background? Or let the processing thread putting the
>>>>> values into a
>>>>>> queue and have a separate thread polling from the queue and
>>>>> add them into
>>>>>> the histogram?
>>>>>>
>>>>>> Thanks,
>>>>>>
>>>>>> Jiangjie (Becket) Qin
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>> On Fri, Feb 22, 2019 at 4:34 PM Chesnay Schepler
>>>>> <chesnay@apache.org <ma...@apache.org>> wrote:
>>>>>>
>>>>>>> Re: Flip
>>>>>>> The very first line under both the main header and Purpose
>>>>> section
>>>>>>> describe Flips as "major changes", which this isn't.
>>>>>>>
>>>>>>> Re: complication
>>>>>>> I'm not arguing against standardization, but again an
>>>>> over-complicated
>>>>>>> implementation when a static utility method would be
>>>>> sufficient.
>>>>>>>
>>>>>>> public static void setupConnectorMetrics(
>>>>>>> MetricGroup operatorMetricGroup,
>>>>>>> String connectorName,
>>>>>>> Optional<Gauge<Long>> numRecordsIn,
>>>>>>> ...)
>>>>>>>
>>>>>>> This gives you all you need:
>>>>>>> * a well-defined set of metrics for a connector to opt-in
>>>>>>> * standardized naming schemes for scope and individual
>>> metrics
>>>>>>> * standardize metric types (although personally I'm not
>>>>> interested in that
>>>>>>> since metric types should be considered syntactic sugar)
>>>>>>>
>>>>>>> Re: Configurable Histogram
>>>>>>> If anything they _must_ be turned off by default, but the
>>>>> metric system is
>>>>>>> already exposing so many options that I'm not too keen on
>>>>> adding even more.
>>>>>>> You have also only addressed my first argument against
>>>>> histograms
>>>>>>> (performance), the second one still stands (calculate
>>>>> histogram in metric
>>>>>>> backends instead).
>>>>>>>
>>>>>>> On 21.02.2019 16:27, Becket Qin wrote:
>>>>>>>> Hi Chesnay,
>>>>>>>>
>>>>>>>> Thanks for the comments. I think this is worthy of a FLIP
>>>>> because it is
>>>>>>>> public API. According to the FLIP description a FlIP is
>>>>> required in case
>>>>>>> of:
>>>>>>>> - Any change that impacts the public interfaces of
>>>>> the project
>>>>>>>>
>>>>>>>> and the following entry is found in the definition of
>>>>> "public interface".
>>>>>>>>
>>>>>>>> - Exposed monitoring information
>>>>>>>>
>>>>>>>> Metrics are critical to any production system. So a clear
>>>>> metric
>>>>>>> definition
>>>>>>>> is important for any serious users. For an organization
>>>>> with large Flink
>>>>>>>> installation, change in metrics means great amount of
>>>>> work. So such
>>>>>>> changes
>>>>>>>> do need to be fully discussed and documented.
>>>>>>>>
>>>>>>>> ** Re: Histogram.
>>>>>>>> We can discuss whether there is a better way to expose
>>>>> metrics that are
>>>>>>>> suitable for histograms. My micro-benchmark on various
>>>>> histogram
>>>>>>>> implementations also indicates that they are
>> significantly
>>>>> slower than
>>>>>>>> other metric types. But I don't think that means never
>> use
>>>>> histogram, but
>>>>>>>> means use it with caution. For example, we can suggest
>> the
>>>>>>> implementations
>>>>>>>> to turn them off by default and only turn it on for a
>>>>> small amount of
>>>>>>> time
>>>>>>>> when performing some micro-debugging.
>>>>>>>>
>>>>>>>> ** Re: complication:
>>>>>>>> Connector conventions are essential for Flink ecosystem.
>>>>> Flink connectors
>>>>>>>> pool is probably the most important part of Flink, just
>>>>> like any other
>>>>>>> data
>>>>>>>> system. Clear conventions of connectors will help build
>>>>> Flink ecosystem
>>>>>>> in
>>>>>>>> a more organic way.
>>>>>>>> Take the metrics convention as an example, imagine
>> someone
>>>>> has developed
>>>>>>> a
>>>>>>>> Flink connector for System foo, and another developer may
>>>>> have developed
>>>>>>> a
>>>>>>>> monitoring and diagnostic framework for Flink which
>>>>> analyzes the Flink
>>>>>>> job
>>>>>>>> performance based on metrics. With a clear metric
>>>>> convention, those two
>>>>>>>> projects could be developed independently. Once users put
>>>>> them together,
>>>>>>>> it would work without additional modifications. This
>>>>> cannot be easily
>>>>>>>> achieved by just defining a few constants.
>>>>>>>>
>>>>>>>> ** Re: selective metrics:
>>>>>>>> Sure, we can discuss that in a separate thread.
>>>>>>>>
>>>>>>>> @Dawid
>>>>>>>>
>>>>>>>> ** Re: latency / fetchedLatency
>>>>>>>> The primary purpose of establish such a convention is to
>>>>> help developers
>>>>>>>> write connectors in a more compatible way. The convention
>>>>> is supposed to
>>>>>>> be
>>>>>>>> defined more proactively. So when look at the convention,
>>>>> it seems more
>>>>>>>> important to see if the concept is applicable to
>>>>> connectors in general.
>>>>>>> It
>>>>>>>> might be true so far only Kafka connector reports
>> latency.
>>>>> But there
>>>>>>> might
>>>>>>>> be hundreds of other connector implementations in the
>>>>> Flink ecosystem,
>>>>>>>> though not in the Flink repo, and some of them also emits
>>>>> latency. I
>>>>>>> think
>>>>>>>> a lot of other sources actually also has an append
>>>>> timestamp. e.g.
>>>>>>> database
>>>>>>>> bin logs and some K-V stores. So I wouldn't be surprised
>>>>> if some database
>>>>>>>> connector can also emit latency metrics.
>>>>>>>>
>>>>>>>> Thanks,
>>>>>>>>
>>>>>>>> Jiangjie (Becket) Qin
>>>>>>>>
>>>>>>>>
>>>>>>>> On Thu, Feb 21, 2019 at 10:14 PM Chesnay Schepler
>>>>> <chesnay@apache.org <ma...@apache.org>>
>>>>>>>> wrote:
>>>>>>>>
>>>>>>>>> Regarding 2) It doesn't make sense to investigate this
>> as
>>>>> part of this
>>>>>>>>> FLIP. This is something that could be of interest for
>> the
>>>>> entire metric
>>>>>>>>> system, and should be designed for as such.
>>>>>>>>>
>>>>>>>>> Regarding the proposal as a whole:
>>>>>>>>>
>>>>>>>>> Histogram metrics shall not be added to the core of
>>>>> Flink. They are
>>>>>>>>> significantly more expensive than other metrics, and
>>>>> calculating
>>>>>>>>> histograms in the application is regarded as an
>>>>> anti-pattern by several
>>>>>>>>> metric backends, who instead recommend to expose the raw
>>>>> data and
>>>>>>>>> calculate the histogram in the backend.
>>>>>>>>>
>>>>>>>>> Second, this seems overly complicated. Given that we
>>>>> already established
>>>>>>>>> that not all connectors will export all metrics we are
>>>>> effectively
>>>>>>>>> reducing this down to a consistent naming scheme. We
>>>>> don't need anything
>>>>>>>>> sophisticated for that; basically just a few constants
>>>>> that all
>>>>>>>>> connectors use.
>>>>>>>>>
>>>>>>>>> I'm not convinced that this is worthy of a FLIP.
>>>>>>>>>
>>>>>>>>> On 21.02.2019 14:26, Dawid Wysakowicz wrote:
>>>>>>>>>> Hi,
>>>>>>>>>>
>>>>>>>>>> Ad 1. In general I undestand and I agree. But those
>>>>> particular metrics
>>>>>>>>>> (latency, fetchLatency), right now would only be
>>>>> reported if user uses
>>>>>>>>>> KafkaConsumer with internal timestampAssigner with
>>>>> StreamCharacteristic
>>>>>>>>>> set to EventTime, right? That sounds like a very
>>>>> specific case. I am
>>>>>>> not
>>>>>>>>>> sure if we should introduce a generic metric that will
>> be
>>>>>>>>>> disabled/absent for most of implementations.
>>>>>>>>>>
>>>>>>>>>> Ad.2 That sounds like an orthogonal issue, that might
>>>>> make sense to
>>>>>>>>>> investigate in the future.
>>>>>>>>>>
>>>>>>>>>> Best,
>>>>>>>>>>
>>>>>>>>>> Dawid
>>>>>>>>>>
>>>>>>>>>> On 21/02/2019 13:20, Becket Qin wrote:
>>>>>>>>>>> Hi Dawid,
>>>>>>>>>>>
>>>>>>>>>>> Thanks for the feedback. That makes sense to me. There
>>>>> are two cases
>>>>>>> to
>>>>>>>>> be
>>>>>>>>>>> addressed.
>>>>>>>>>>>
>>>>>>>>>>> 1. The metrics are supposed to be a guidance. It is
>>>>> likely that a
>>>>>>>>> connector
>>>>>>>>>>> only supports some but not all of the metrics. In that
>>>>> case, each
>>>>>>>>> connector
>>>>>>>>>>> implementation should have the freedom to decide which
>>>>> metrics are
>>>>>>>>>>> reported. For the metrics that are supported, the
>>>>> guidance should be
>>>>>>>>>>> followed.
>>>>>>>>>>>
>>>>>>>>>>> 2. Sometimes users may want to disable certain metrics
>>>>> for some reason
>>>>>>>>>>> (e.g. performance / reprocessing of data). A generic
>>>>> mechanism should
>>>>>>> be
>>>>>>>>>>> provided to allow user choose which metrics are
>>>>> reported. This
>>>>>>> mechanism
>>>>>>>>>>> should also be honored by the connector
>> implementations.
>>>>>>>>>>>
>>>>>>>>>>> Does this sound reasonable to you?
>>>>>>>>>>>
>>>>>>>>>>> Thanks,
>>>>>>>>>>>
>>>>>>>>>>> Jiangjie (Becket) Qin
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>> On Thu, Feb 21, 2019 at 4:22 PM Dawid Wysakowicz <
>>>>>>>>> dwysakowicz@apache.org <ma...@apache.org>>
>>>>>>>>>>> wrote:
>>>>>>>>>>>
>>>>>>>>>>>> Hi,
>>>>>>>>>>>>
>>>>>>>>>>>> Generally I like the idea of having a unified,
>>>>> standard set of
>>>>>>> metrics
>>>>>>>>> for
>>>>>>>>>>>> all connectors. I have some slight concerns about
>>>>> fetchLatency and
>>>>>>>>>>>> latency though. They are computed based on EventTime
>>>>> which is not a
>>>>>>>>> purely
>>>>>>>>>>>> technical feature. It depends often on some business
>>>>> logic, might be
>>>>>>>>> absent
>>>>>>>>>>>> or defined after source. Those metrics could also
>>>>> behave in a weird
>>>>>>>>> way in
>>>>>>>>>>>> case of replaying backlog. Therefore I am not sure if
>>>>> we should
>>>>>>> include
>>>>>>>>>>>> those metrics by default. Maybe we could at least
>>>>> introduce a feature
>>>>>>>>>>>> switch for them? What do you think?
>>>>>>>>>>>>
>>>>>>>>>>>> Best,
>>>>>>>>>>>>
>>>>>>>>>>>> Dawid
>>>>>>>>>>>> On 21/02/2019 03:13, Becket Qin wrote:
>>>>>>>>>>>>
>>>>>>>>>>>> Bump. If there is no objections to the proposed
>>>>> metrics. I'll start a
>>>>>>>>>>>> voting thread later toady.
>>>>>>>>>>>>
>>>>>>>>>>>> Thanks,
>>>>>>>>>>>>
>>>>>>>>>>>> Jiangjie (Becket) Qin
>>>>>>>>>>>>
>>>>>>>>>>>> On Mon, Feb 11, 2019 at 8:17 PM Becket Qin
>>>>> <becket.qin@gmail.com <ma...@gmail.com>> <
>>>>>>>>> becket.qin@gmail.com <ma...@gmail.com>>
>>> wrote:
>>>>>>>>>>>> Hi folks,
>>>>>>>>>>>>
>>>>>>>>>>>> I would like to start the FLIP discussion thread
>> about
>>>>> standardize
>>>>>>> the
>>>>>>>>>>>> connector metrics.
>>>>>>>>>>>>
>>>>>>>>>>>> In short, we would like to provide a convention of
>>>>> Flink connector
>>>>>>>>>>>> metrics. It will help simplify the monitoring and
>>>>> alerting on Flink
>>>>>>>>> jobs.
>>>>>>>>>>>> The FLIP link is following:
>>>>>>>>>>>>
>>>>>>>>>>>>
>>>>>>>
>>>>>
>>>>
>>>
>> https://cwiki.apache.org/confluence/display/FLINK/FLIP-33%3A+Standardize+Connector+Metrics
>>>>>>>>>>>> Thanks,
>>>>>>>>>>>>
>>>>>>>>>>>> Jiangjie (Becket) Qin
>>>>>>>>>>>>
>>>>>>>>>>>>
>>>>>>>>>>>>
>>>>>>>
>>>>>
>>>>
>>>>
>>>
>>
Re: [DISCUSS] FLIP-33: Standardize connector metrics
Posted by Konstantin Knauf <kn...@apache.org>.
+1 from my side
On Fri, Sep 18, 2020 at 4:54 PM Stephan Ewen <st...@ververica.com> wrote:
> Having the watermark lag metric was the important part from my side.
>
> So +1 to go ahead.
>
> On Fri, Sep 18, 2020 at 4:11 PM Becket Qin <be...@gmail.com> wrote:
>
> > Hey Stephan,
> >
> > Thanks for the quick reply. I actually forgot to mention that I also
> added
> > a "watermarkLag" metric to the Source metrics in addition to the
> > "currentFetchEventTimeLag" and "currentEmitEventTimeLag".
> > So in the current proposal, both XXEventTimeLag will be based on event
> > timestamps, while the watermarkLag is based on watermark. And all the
> lags
> > are defined against the wall clock time. Does this cover what you are
> > proposing?
> >
> > Thanks,
> >
> > Jiangjie (Becket) Qin
> >
> > On Fri, Sep 18, 2020 at 6:08 PM Stephan Ewen <st...@ververica.com>
> > wrote:
> >
> >> Hi Becket!
> >>
> >> I am wondering if it makes sense to do the following small change:
> >>
> >> - Have "currentFetchEventTimeLag" be defined on event timestamps
> >> (optionally, if the source system exposes it) <== this is like in your
> >> proposal
> >> this helps understand how long the records were in the source
> before
> >>
> >> - BUT change "currentEmitEventTimeLag" to be
> >> "currentSourceWatermarkLag" instead.
> >> That way, users can see how far behind the wall-clock-time the
> source
> >> progress is all in all.
> >> It is also a more well defined metric as it does not oscillate with
> >> out-of-order events.
> >>
> >> What do you think?
> >>
> >> Best,
> >> Stephan
> >>
> >>
> >>
> >> On Fri, Sep 18, 2020 at 12:02 PM Becket Qin <be...@gmail.com>
> wrote:
> >>
> >>> Hi folks,
> >>>
> >>> Thanks for all the great feedback. I have just updated FLIP-33 wiki
> with
> >>> the following changes:
> >>>
> >>> 1. Renaming. "currentFetchLatency" to "currentFetchEventTimeLag",
> >>> "currentLatency" to "currentEmitEventTimeLag".
> >>> 2. Added the public interface code change required for the new metrics.
> >>> 3. Added description of whether a metric is predefined or optional, and
> >>> which component is expected to update the metric.
> >>>
> >>> Please let me know if you have any questions. I'll start a vote in two
> >>> days if there are no further concerns.
> >>>
> >>> Thanks,
> >>>
> >>> Jiangjie (Becket) Qin
> >>>
> >>> On Wed, Sep 9, 2020 at 9:56 AM Becket Qin <be...@gmail.com>
> wrote:
> >>>
> >>>> Hi Stephan,
> >>>>
> >>>> Thanks for the input. Just a few more clarifications / questions.
> >>>>
> >>>> *Num Bytes / Records Metrics*
> >>>>
> >>>> 1. At this point, the *numRecordsIn(Rate)* metrics exist in both
> >>>> OperatorIOMetricGroup and TaskIOMetricGroup. I did not find
> >>>> *numRecordsIn(Rate)* in the TaskIOMetricGroup updated anywhere other
> >>>> than in the unit tests. Am I missing something?
> >>>>
> >>>> 2. *numBytesIn(Rate)* metrics only exist in TaskIOMetricGroup. At this
> >>>> point, the SourceReaders only has access to a SourceReaderContext
> which
> >>>> provides an OperatorMetricGroup. So it seems that the connector
> developers
> >>>> are not able to update the *numBytesIn(Rate). *With the multiple
> >>>> Source chaining support, it is possible that there are multiple
> Sources are
> >>>> in the same task. So it looks that we need to add *numBytesIn(Rate)*
> >>>> to the operator metrics as well.
> >>>>
> >>>>
> >>>> *Current (Fetch) Latency*
> >>>>
> >>>> *currentFetchLatency* helps clearly tell whether the latency is caused
> >>>> by Flink or not. Backpressure is not the only reason that we see fetch
> >>>> latency. Even if there is no back pressure, the records may have
> passed a
> >>>> long pipeline before they entered Flink. For example, say the
> *currentLatency
> >>>> *is 10 seconds and there is no backpressure. Does that mean the record
> >>>> spent 10 seconds in the Source operator? If not, how much did Flink
> >>>> contribute to that 10 seconds of latency? These questions are
> frequently
> >>>> asked and hard to tell without the fetch latency.
> >>>>
> >>>> For "currentFetchLatency", we would need to understand timestamps
> >>>>> before the records are decoded. That is only possible for some
> sources,
> >>>>> where the client gives us the records in a (partially) decoded from
> already
> >>>>> (like Kafka). Then, some work has been done between the fetch time
> and the
> >>>>> time we update the metric already, so it is already a bit closer to
> the
> >>>>> "currentFetchLatency". I think following this train of thought,
> there is
> >>>>> diminished benefit from that specific metric.
> >>>>
> >>>>
> >>>> We may not have to report the fetch latency before records are
> decoded.
> >>>> One solution is to remember the* FetchTime* when the encoded records
> >>>> are fetched, and report the fetch latency after the records are
> decoded by
> >>>> computing (*FetchTime - EventTime*). An approximate implementation
> >>>> would be adding a *FetchTime *field to the *RecordsWithSplitIds*
> assuming
> >>>> that all the records in that data structure are fetched at the same
> time.
> >>>>
> >>>> Thoughts?
> >>>>
> >>>> Thanks,
> >>>>
> >>>> Jiangjie (Becket) Qin
> >>>>
> >>>> On Wed, Sep 9, 2020 at 12:42 AM Stephan Ewen <st...@ververica.com>
> >>>> wrote:
> >>>>
> >>>>> Thanks for reviving this, Becket!
> >>>>>
> >>>>> I think Konstantin's comments are great. I'd add these points:
> >>>>>
> >>>>> *Num Bytes / Records Metrics*
> >>>>>
> >>>>> For "numBytesIn" and "numRecordsIn", we should reuse the
> >>>>> OperatorIOMetric group, then it also gets reported to the overview
> page in
> >>>>> the Web UI.
> >>>>>
> >>>>> The "numBytesInPerSecond" and "numRecordsInPerSecond" are
> >>>>> automatically derived metrics, no need to do anything once we
> populate the
> >>>>> above two metrics
> >>>>>
> >>>>>
> >>>>> *Current (Fetch) Latency*
> >>>>>
> >>>>> I would really go for "eventTimeLag" rather than "fetchLatency". I
> >>>>> think "eventTimeLag" is a term that has some adoption in the Flink
> >>>>> community and beyond.
> >>>>>
> >>>>> I am not so sure that I see the benefit between "currentLatency" and
> >>>>> "currentFetchLatency", (or event time lag before/after) as this only
> is
> >>>>> different by the time it takes to emit a batch.
> >>>>> - In a non-backpressured case, these should be virtually
> >>>>> identical (and both dominated by watermark lag, not the actual time
> it
> >>>>> takes the fetch to be emitted)
> >>>>> - In a backpressured case, why do you care about when data was
> >>>>> fetched, as opposed to emitted? Emitted time is relevant for
> application
> >>>>> semantics and checkpoints. Fetch time seems to be an implementation
> detail
> >>>>> (how much does the source buffer).
> >>>>>
> >>>>> The "currentLatency" (eventTimeLagAfter) can be computed
> >>>>> out-of-the-box, independent of a source implementation, so that is
> also a
> >>>>> good argument to make it the main metric.
> >>>>> We know timestamps and watermarks in the source. Except for cases
> >>>>> where no watermarks have been defined at all (batch jobs or pure
> processing
> >>>>> time jobs), in which case this metric should probably be "Infinite".
> >>>>>
> >>>>> For "currentFetchLatency", we would need to understand timestamps
> >>>>> before the records are decoded. That is only possible for some
> sources,
> >>>>> where the client gives us the records in a (partially) decoded from
> already
> >>>>> (like Kafka). Then, some work has been done between the fetch time
> and the
> >>>>> time we update the metric already, so it is already a bit closer to
> the
> >>>>> "currentFetchLatency". I think following this train of thought,
> there is
> >>>>> diminished benefit from that specific metric.
> >>>>>
> >>>>>
> >>>>> *Idle Time*
> >>>>>
> >>>>> I agree, it would be great to rename this. Maybe to "sourceWaitTime"
> >>>>> or "sourceIdleTime" so to make clear that this is not exactly the
> time that
> >>>>> Flink's processing pipeline is idle, but the time where the source
> does not
> >>>>> have new data.
> >>>>>
> >>>>> This is not an easy metric to collect, though (except maybe for the
> >>>>> sources that are only idle while they have no split assigned, like
> >>>>> continuous file source).
> >>>>>
> >>>>> *Source Specific Metrics*
> >>>>>
> >>>>> I believe source-specific would only be "sourceIdleTime",
> >>>>> "numRecordsInErrors", "pendingBytes", and "pendingRecords".
> >>>>>
> >>>>>
> >>>>> *Conclusion*
> >>>>>
> >>>>> We can probably add "numBytesIn" and "numRecordsIn" and
> "eventTimeLag"
> >>>>> right away, with little complexity.
> >>>>> I'd suggest to start with these right away.
> >>>>>
> >>>>> Best,
> >>>>> Stephan
> >>>>>
> >>>>>
> >>>>> On Tue, Sep 8, 2020 at 3:25 PM Becket Qin <be...@gmail.com>
> >>>>> wrote:
> >>>>>
> >>>>>> Hey Konstantin,
> >>>>>>
> >>>>>> Thanks for the feedback and suggestions. Please see the reply below.
> >>>>>>
> >>>>>> * idleTime: In the meantime, a similar metric "idleTimeMsPerSecond"
> >>>>>>> has
> >>>>>>> been introduced in
> https://issues.apache.org/jira/browse/FLINK-16864.
> >>>>>>> They
> >>>>>>> have a similar name, but different definitions of idleness,
> >>>>>>> e.g. "idleTimeMsPerSecond" considers the SourceTask idle, when it
> is
> >>>>>>> backpressured. Can we make it clearer that these two metrics mean
> >>>>>>> different
> >>>>>>> things?
> >>>>>>
> >>>>>>
> >>>>>> That is a good point. I did not notice this metric earlier. It seems
> >>>>>> that both metrics are useful to the users. One tells them how busy
> the
> >>>>>> source is and how much more throughput the source can handle. The
> other
> >>>>>> tells the users how long since the source has seen the last record,
> which
> >>>>>> is useful for debugging. I'll update the FLIP to make it clear.
> >>>>>>
> >>>>>> * "current(Fetch)Latency" I am wondering if
> >>>>>>> "eventTimeLag(Before|After)"
> >>>>>>> is more descriptive/clear. What do others think?
> >>>>>>
> >>>>>>
> >>>>>> I am quite open to the ideas on these names. In fact I also feel
> >>>>>> "current(Fetch)Latency" are not super intuitive. So it would be
> great if we
> >>>>>> can have better names.
> >>>>>>
> >>>>>> * Current(Fetch)Latency implies that the timestamps are directly
> >>>>>>> extracted in the source connector, right? Will this be the default
> >>>>>>> for
> >>>>>>> FLIP-27 sources anyway?
> >>>>>>
> >>>>>>
> >>>>>> The "currentFetchLatency" will probably be reported by each source
> >>>>>> implementation, because the data fetching is done by SplitReaders
> and there
> >>>>>> is no base implementation. The "currentLatency", on the other hand,
> can be
> >>>>>> reported by the SourceReader base implementation. However, since
> developers
> >>>>>> can actually implement their own source connector without using our
> base
> >>>>>> implementation, these metric guidance are still useful for the
> connector
> >>>>>> developers in that case.
> >>>>>>
> >>>>>> * Does FLIP-33 also include the implementation of these metrics (to
> >>>>>>> the
> >>>>>>> extent possible) for all connectors currently available in Apache
> >>>>>>> Flink or
> >>>>>>> is the "per-connector implementation" out-of-scope?
> >>>>>>
> >>>>>>
> >>>>>> FLIP-33 itself does not specify any implementation of those metrics.
> >>>>>> But the connectors we provide in Apache Flink will follow the
> guidance of
> >>>>>> FLIP-33 to emit those metrics when applicable. Maybe We can have
> some
> >>>>>> public static Strings defined for the metric names to help other
> connector
> >>>>>> developers follow the same guidance. I can also add that to the
> public
> >>>>>> interface section of the FLIP if we decide to do that.
> >>>>>>
> >>>>>> Thanks,
> >>>>>>
> >>>>>> Jiangjie (Becket) Qin
> >>>>>>
> >>>>>> On Tue, Sep 8, 2020 at 9:02 PM Becket Qin <be...@gmail.com>
> >>>>>> wrote:
> >>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>> On Tue, Sep 8, 2020 at 6:55 PM Konstantin Knauf <knaufk@apache.org
> >
> >>>>>>> wrote:
> >>>>>>>
> >>>>>>>> Hi Becket,
> >>>>>>>>
> >>>>>>>> Thank you for picking up this FLIP. I have a few questions:
> >>>>>>>>
> >>>>>>>> * two thoughts on naming:
> >>>>>>>> * idleTime: In the meantime, a similar metric
> >>>>>>>> "idleTimeMsPerSecond" has
> >>>>>>>> been introduced in
> >>>>>>>> https://issues.apache.org/jira/browse/FLINK-16864. They
> >>>>>>>> have a similar name, but different definitions of idleness,
> >>>>>>>> e.g. "idleTimeMsPerSecond" considers the SourceTask idle, when it
> is
> >>>>>>>> backpressured. Can we make it clearer that these two metrics mean
> >>>>>>>> different
> >>>>>>>> things?
> >>>>>>>>
> >>>>>>>> * "current(Fetch)Latency" I am wondering if
> >>>>>>>> "eventTimeLag(Before|After)"
> >>>>>>>> is more descriptive/clear. What do others think?
> >>>>>>>>
> >>>>>>>> * Current(Fetch)Latency implies that the timestamps are directly
> >>>>>>>> extracted in the source connector, right? Will this be the default
> >>>>>>>> for
> >>>>>>>> FLIP-27 sources anyway?
> >>>>>>>>
> >>>>>>>> * Does FLIP-33 also include the implementation of these metrics
> (to
> >>>>>>>> the
> >>>>>>>> extent possible) for all connectors currently available in Apache
> >>>>>>>> Flink or
> >>>>>>>> is the "per-connector implementation" out-of-scope?
> >>>>>>>>
> >>>>>>>> Thanks,
> >>>>>>>>
> >>>>>>>> Konstantin
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>> On Fri, Sep 4, 2020 at 4:56 PM Becket Qin <be...@gmail.com>
> >>>>>>>> wrote:
> >>>>>>>>
> >>>>>>>> > Hi all,
> >>>>>>>> >
> >>>>>>>> > To complete the Source refactoring work, I'd like to revive this
> >>>>>>>> > discussion. Since the mail thread has been dormant for more than
> >>>>>>>> a year,
> >>>>>>>> > just to recap the motivation of the FLIP:
> >>>>>>>> >
> >>>>>>>> > 1. The FLIP proposes to standardize the connector metrics by
> >>>>>>>> giving
> >>>>>>>> > guidance on the metric specifications, including the name, type
> >>>>>>>> and meaning
> >>>>>>>> > of the metrics.
> >>>>>>>> > 2. It is OK for a connector to not emit some of the metrics in
> >>>>>>>> the metric
> >>>>>>>> > guidance, but if a metric of the same semantic is emitted, the
> >>>>>>>> > implementation should follow the guidance.
> >>>>>>>> > 3. It is OK for a connector to emit more metrics than what are
> >>>>>>>> listed in
> >>>>>>>> > the FLIP. This includes having an alias for a metric specified
> in
> >>>>>>>> the FLIP.
> >>>>>>>> > 4. We will implement some of the metrics out of the box in the
> >>>>>>>> default
> >>>>>>>> > implementation of FLIP-27, as long as it is applicable.
> >>>>>>>> >
> >>>>>>>> > The FLIP wiki is following:
> >>>>>>>> > https://cwiki.apache.org/confluence/display/FLINK/FLIP-33
> >>>>>>>> > %3A+Standardize+Connector+Metrics
> >>>>>>>> >
> >>>>>>>> > Any thoughts?
> >>>>>>>> >
> >>>>>>>> > Thanks,
> >>>>>>>> >
> >>>>>>>> > Jiangjie (Becket) Qin
> >>>>>>>> >
> >>>>>>>> >
> >>>>>>>> > On Fri, Jun 14, 2019 at 2:29 PM Piotr Nowojski <
> >>>>>>>> piotr@ververica.com>
> >>>>>>>> > wrote:
> >>>>>>>> >
> >>>>>>>> > > > we will need to revisit the convention list and adjust them
> >>>>>>>> accordingly
> >>>>>>>> > > when FLIP-27 is ready
> >>>>>>>> > >
> >>>>>>>> > >
> >>>>>>>> > > Yes, this sounds good :)
> >>>>>>>> > >
> >>>>>>>> > > Piotrek
> >>>>>>>> > >
> >>>>>>>> > > > On 13 Jun 2019, at 13:35, Becket Qin <be...@gmail.com>
> >>>>>>>> wrote:
> >>>>>>>> > > >
> >>>>>>>> > > > Hi Piotr,
> >>>>>>>> > > >
> >>>>>>>> > > > That's great to know. Chances are that we will need to
> >>>>>>>> revisit the
> >>>>>>>> > > > convention list and adjust them accordingly when FLIP-27 is
> >>>>>>>> ready, At
> >>>>>>>> > > that
> >>>>>>>> > > > point we can mark some of the metrics as available by
> default
> >>>>>>>> for
> >>>>>>>> > > > connectors implementing the new interface.
> >>>>>>>> > > >
> >>>>>>>> > > > Thanks,
> >>>>>>>> > > >
> >>>>>>>> > > > Jiangjie (Becket) Qin
> >>>>>>>> > > >
> >>>>>>>> > > > On Thu, Jun 13, 2019 at 3:51 PM Piotr Nowojski <
> >>>>>>>> piotr@ververica.com>
> >>>>>>>> > > wrote:
> >>>>>>>> > > >
> >>>>>>>> > > >> Thanks for driving this. I’ve just noticed one small thing.
> >>>>>>>> With new
> >>>>>>>> > > >> SourceReader interface Flink will be able to provide
> >>>>>>>> `idleTime` metric
> >>>>>>>> > > >> automatically.
> >>>>>>>> > > >>
> >>>>>>>> > > >> Piotrek
> >>>>>>>> > > >>
> >>>>>>>> > > >>> On 13 Jun 2019, at 03:30, Becket Qin <
> becket.qin@gmail.com>
> >>>>>>>> wrote:
> >>>>>>>> > > >>>
> >>>>>>>> > > >>> Thanks all for the feedback and discussion.
> >>>>>>>> > > >>>
> >>>>>>>> > > >>> Since there wasn't any concern raised, I've started the
> >>>>>>>> voting thread
> >>>>>>>> > > for
> >>>>>>>> > > >>> this FLIP, but please feel free to continue the discussion
> >>>>>>>> here if
> >>>>>>>> > you
> >>>>>>>> > > >>> think something still needs to be addressed.
> >>>>>>>> > > >>>
> >>>>>>>> > > >>> Thanks,
> >>>>>>>> > > >>>
> >>>>>>>> > > >>> Jiangjie (Becket) Qin
> >>>>>>>> > > >>>
> >>>>>>>> > > >>>
> >>>>>>>> > > >>>
> >>>>>>>> > > >>> On Mon, Jun 10, 2019 at 9:10 AM Becket Qin <
> >>>>>>>> becket.qin@gmail.com>
> >>>>>>>> > > wrote:
> >>>>>>>> > > >>>
> >>>>>>>> > > >>>> Hi Piotr,
> >>>>>>>> > > >>>>
> >>>>>>>> > > >>>> Thanks for the comments. Yes, you are right. Users will
> >>>>>>>> have to look
> >>>>>>>> > > at
> >>>>>>>> > > >>>> other metrics to decide whether the pipeline is healthy
> or
> >>>>>>>> not in
> >>>>>>>> > the
> >>>>>>>> > > >> first
> >>>>>>>> > > >>>> place before they can use the time-based metric to fix
> the
> >>>>>>>> > bottleneck.
> >>>>>>>> > > >>>>
> >>>>>>>> > > >>>> I agree that once we have FLIP-27 ready, some of the
> >>>>>>>> metrics can
> >>>>>>>> > just
> >>>>>>>> > > be
> >>>>>>>> > > >>>> reported by the abstract implementation.
> >>>>>>>> > > >>>>
> >>>>>>>> > > >>>> I've updated FLIP-33 wiki page to add the pendingBytes
> and
> >>>>>>>> > > >> pendingRecords
> >>>>>>>> > > >>>> metric. Please let me know if you have any concern over
> >>>>>>>> the updated
> >>>>>>>> > > >> metric
> >>>>>>>> > > >>>> convention proposal.
> >>>>>>>> > > >>>>
> >>>>>>>> > > >>>> @Chesnay Schepler <ch...@apache.org> @Stephan Ewen
> >>>>>>>> > > >>>> <st...@ververica.com> will you also have time to take
> a
> >>>>>>>> look at
> >>>>>>>> > the
> >>>>>>>> > > >>>> proposed metric convention? If there is no further
> concern
> >>>>>>>> I'll
> >>>>>>>> > start
> >>>>>>>> > > a
> >>>>>>>> > > >>>> voting thread for this FLIP in two days.
> >>>>>>>> > > >>>>
> >>>>>>>> > > >>>> Thanks,
> >>>>>>>> > > >>>>
> >>>>>>>> > > >>>> Jiangjie (Becket) Qin
> >>>>>>>> > > >>>>
> >>>>>>>> > > >>>>
> >>>>>>>> > > >>>>
> >>>>>>>> > > >>>> On Wed, Jun 5, 2019 at 6:54 PM Piotr Nowojski <
> >>>>>>>> piotr@ververica.com>
> >>>>>>>> > > >> wrote:
> >>>>>>>> > > >>>>
> >>>>>>>> > > >>>>> Hi Becket,
> >>>>>>>> > > >>>>>
> >>>>>>>> > > >>>>> Thanks for the answer :)
> >>>>>>>> > > >>>>>
> >>>>>>>> > > >>>>>> By time-based metric, I meant the portion of time spent
> >>>>>>>> on
> >>>>>>>> > producing
> >>>>>>>> > > >> the
> >>>>>>>> > > >>>>>> record to downstream. For example, a source connector
> >>>>>>>> can report
> >>>>>>>> > > that
> >>>>>>>> > > >>>>> it's
> >>>>>>>> > > >>>>>> spending 80% of time to emit record to downstream
> >>>>>>>> processing
> >>>>>>>> > > pipeline.
> >>>>>>>> > > >>>>> In
> >>>>>>>> > > >>>>>> another case, a sink connector may report that its
> >>>>>>>> spending 30% of
> >>>>>>>> > > >> time
> >>>>>>>> > > >>>>>> producing the records to the external system.
> >>>>>>>> > > >>>>>>
> >>>>>>>> > > >>>>>> This is in some sense equivalent to the buffer usage
> >>>>>>>> metric:
> >>>>>>>> > > >>>>>
> >>>>>>>> > > >>>>>> - 80% of time spent on emitting records to downstream
> >>>>>>>> --->
> >>>>>>>> > > downstream
> >>>>>>>> > > >>>>>> node is bottleneck ---> output buffer is probably full.
> >>>>>>>> > > >>>>>> - 30% of time spent on emitting records to downstream
> >>>>>>>> --->
> >>>>>>>> > > downstream
> >>>>>>>> > > >>>>>> node is not bottleneck ---> output buffer is probably
> >>>>>>>> not full.
> >>>>>>>> > > >>>>>
> >>>>>>>> > > >>>>> If by “time spent on emitting records to downstream” you
> >>>>>>>> understand
> >>>>>>>> > > >>>>> “waiting on back pressure”, then I see your point. And I
> >>>>>>>> agree that
> >>>>>>>> > > >> some
> >>>>>>>> > > >>>>> kind of ratio/time based metric gives you more
> >>>>>>>> information. However
> >>>>>>>> > > >> under
> >>>>>>>> > > >>>>> “time spent on emitting records to downstream” might be
> >>>>>>>> hidden the
> >>>>>>>> > > >>>>> following (extreme) situation:
> >>>>>>>> > > >>>>>
> >>>>>>>> > > >>>>> 1. Job is barely able to handle influx of records, there
> >>>>>>>> is 99%
> >>>>>>>> > > >>>>> CPU/resource usage in the cluster, but nobody is
> >>>>>>>> > > >>>>> bottlenecked/backpressured, all output buffers are
> empty,
> >>>>>>>> everybody
> >>>>>>>> > > is
> >>>>>>>> > > >>>>> waiting in 1% of it’s time for more records to process.
> >>>>>>>> > > >>>>> 2. 80% time can still be spent on "down stream
> >>>>>>>> operators”, because
> >>>>>>>> > > they
> >>>>>>>> > > >>>>> are the CPU intensive operations, but this doesn’t mean
> >>>>>>>> that
> >>>>>>>> > > >> increasing the
> >>>>>>>> > > >>>>> parallelism down the stream will help with anything
> >>>>>>>> there. To the
> >>>>>>>> > > >> contrary,
> >>>>>>>> > > >>>>> increasing parallelism of the source operator might help
> >>>>>>>> to
> >>>>>>>> > increase
> >>>>>>>> > > >>>>> resource utilisation up to 100%.
> >>>>>>>> > > >>>>>
> >>>>>>>> > > >>>>> However, this “time based/ratio” approach can be
> extended
> >>>>>>>> to
> >>>>>>>> > > in/output
> >>>>>>>> > > >>>>> buffer usage. Besides collecting an information that
> >>>>>>>> input/output
> >>>>>>>> > > >> buffer is
> >>>>>>>> > > >>>>> full/empty, we can probe profile how often are buffer
> >>>>>>>> empty/full.
> >>>>>>>> > If
> >>>>>>>> > > >> output
> >>>>>>>> > > >>>>> buffer is full 1% of times, there is almost no back
> >>>>>>>> pressure. If
> >>>>>>>> > it’s
> >>>>>>>> > > >> full
> >>>>>>>> > > >>>>> 80% of times, there is some back pressure, if it’s full
> >>>>>>>> 99.9% of
> >>>>>>>> > > times,
> >>>>>>>> > > >>>>> there is huge back pressure.
> >>>>>>>> > > >>>>>
> >>>>>>>> > > >>>>> Now for autoscaling you could compare the input & output
> >>>>>>>> buffers
> >>>>>>>> > fill
> >>>>>>>> > > >>>>> ratio:
> >>>>>>>> > > >>>>>
> >>>>>>>> > > >>>>> 1. Both are high, the source of bottleneck is down the
> >>>>>>>> stream
> >>>>>>>> > > >>>>> 2. Output is low, input is high, this is the bottleneck
> >>>>>>>> and the
> >>>>>>>> > > higher
> >>>>>>>> > > >>>>> the difference, the bigger source of bottleneck is this
> is
> >>>>>>>> > > >> operator/task
> >>>>>>>> > > >>>>> 3. Output is high, input is low - there was some load
> >>>>>>>> spike that we
> >>>>>>>> > > are
> >>>>>>>> > > >>>>> currently finishing to process
> >>>>>>>> > > >>>>>
> >>>>>>>> > > >>>>>
> >>>>>>>> > > >>>>>
> >>>>>>>> > > >>>>> But long story short, we are probably diverging from the
> >>>>>>>> topic of
> >>>>>>>> > > this
> >>>>>>>> > > >>>>> discussion, and we can discuss this at some later point.
> >>>>>>>> > > >>>>>
> >>>>>>>> > > >>>>> For now, for sources:
> >>>>>>>> > > >>>>>
> >>>>>>>> > > >>>>> as I wrote before, +1 for:
> >>>>>>>> > > >>>>> - pending.bytes, Gauge
> >>>>>>>> > > >>>>> - pending.messages, Gauge
> >>>>>>>> > > >>>>>
> >>>>>>>> > > >>>>> When we will be developing/discussing SourceReader from
> >>>>>>>> FLIP-27 we
> >>>>>>>> > > >> might
> >>>>>>>> > > >>>>> then add:
> >>>>>>>> > > >>>>>
> >>>>>>>> > > >>>>> - in-memory.buffer.usage (0 - 100%)
> >>>>>>>> > > >>>>>
> >>>>>>>> > > >>>>> Which will be estimated automatically by Flink while
> user
> >>>>>>>> will be
> >>>>>>>> > > able
> >>>>>>>> > > >> to
> >>>>>>>> > > >>>>> override/provide better estimation.
> >>>>>>>> > > >>>>>
> >>>>>>>> > > >>>>> Piotrek
> >>>>>>>> > > >>>>>
> >>>>>>>> > > >>>>>> On 5 Jun 2019, at 05:42, Becket Qin <
> >>>>>>>> becket.qin@gmail.com> wrote:
> >>>>>>>> > > >>>>>>
> >>>>>>>> > > >>>>>> Hi Piotr,
> >>>>>>>> > > >>>>>>
> >>>>>>>> > > >>>>>> Thanks for the explanation. Please see some
> >>>>>>>> clarifications below.
> >>>>>>>> > > >>>>>>
> >>>>>>>> > > >>>>>> By time-based metric, I meant the portion of time spent
> >>>>>>>> on
> >>>>>>>> > producing
> >>>>>>>> > > >> the
> >>>>>>>> > > >>>>>> record to downstream. For example, a source connector
> >>>>>>>> can report
> >>>>>>>> > > that
> >>>>>>>> > > >>>>> it's
> >>>>>>>> > > >>>>>> spending 80% of time to emit record to downstream
> >>>>>>>> processing
> >>>>>>>> > > pipeline.
> >>>>>>>> > > >>>>> In
> >>>>>>>> > > >>>>>> another case, a sink connector may report that its
> >>>>>>>> spending 30% of
> >>>>>>>> > > >> time
> >>>>>>>> > > >>>>>> producing the records to the external system.
> >>>>>>>> > > >>>>>>
> >>>>>>>> > > >>>>>> This is in some sense equivalent to the buffer usage
> >>>>>>>> metric:
> >>>>>>>> > > >>>>>> - 80% of time spent on emitting records to downstream
> >>>>>>>> --->
> >>>>>>>> > > downstream
> >>>>>>>> > > >>>>>> node is bottleneck ---> output buffer is probably full.
> >>>>>>>> > > >>>>>> - 30% of time spent on emitting records to downstream
> >>>>>>>> --->
> >>>>>>>> > > downstream
> >>>>>>>> > > >>>>>> node is not bottleneck ---> output buffer is probably
> >>>>>>>> not full.
> >>>>>>>> > > >>>>>>
> >>>>>>>> > > >>>>>> However, the time-based metric has a few advantages
> that
> >>>>>>>> the
> >>>>>>>> > buffer
> >>>>>>>> > > >>>>> usage
> >>>>>>>> > > >>>>>> metric may not have.
> >>>>>>>> > > >>>>>>
> >>>>>>>> > > >>>>>> 1. Buffer usage metric may not be applicable to all
> the
> >>>>>>>> connector
> >>>>>>>> > > >>>>>> implementations, while reporting time-based metric are
> >>>>>>>> always
> >>>>>>>> > > doable.
> >>>>>>>> > > >>>>>> Some source connectors may not have any input buffer,
> or
> >>>>>>>> they may
> >>>>>>>> > > use
> >>>>>>>> > > >>>>> some
> >>>>>>>> > > >>>>>> third party library that does not expose the input
> >>>>>>>> buffer at all.
> >>>>>>>> > > >>>>>> Similarly, for sink connectors, the implementation may
> >>>>>>>> not have
> >>>>>>>> > any
> >>>>>>>> > > >>>>> output
> >>>>>>>> > > >>>>>> buffer, or the third party library does not expose such
> >>>>>>>> buffer.
> >>>>>>>> > > >>>>>>
> >>>>>>>> > > >>>>>> 2. Although both type of metrics can detect bottleneck,
> >>>>>>>> time-based
> >>>>>>>> > > >>>>> metrics
> >>>>>>>> > > >>>>>> can be used to generate a more informed action to
> remove
> >>>>>>>> the
> >>>>>>>> > > >> bottleneck.
> >>>>>>>> > > >>>>>> For example, when the downstream is bottleneck, the
> >>>>>>>> output buffer
> >>>>>>>> > > >> usage
> >>>>>>>> > > >>>>>> metric is likely to be 100%, and the input buffer usage
> >>>>>>>> might be
> >>>>>>>> > 0%.
> >>>>>>>> > > >>>>> That
> >>>>>>>> > > >>>>>> means we don't know what is the suitable parallelism to
> >>>>>>>> lift the
> >>>>>>>> > > >>>>>> bottleneck. The time-based metric, on the other hand,
> >>>>>>>> would give
> >>>>>>>> > > >> useful
> >>>>>>>> > > >>>>>> information, e.g. if 80% of time was spent on emitting
> >>>>>>>> records, we
> >>>>>>>> > > can
> >>>>>>>> > > >>>>>> roughly increase the downstream node parallelism by 4
> >>>>>>>> times.
> >>>>>>>> > > >>>>>>
> >>>>>>>> > > >>>>>> Admittedly, the time-based metrics are more expensive
> >>>>>>>> than buffer
> >>>>>>>> > > >>>>> usage. So
> >>>>>>>> > > >>>>>> we may have to do some sampling to reduce the cost. But
> >>>>>>>> in
> >>>>>>>> > general,
> >>>>>>>> > > >>>>> using
> >>>>>>>> > > >>>>>> time-based metrics seems worth adding.
> >>>>>>>> > > >>>>>>
> >>>>>>>> > > >>>>>> That being said, I don't think buffer usage metric and
> >>>>>>>> time-based
> >>>>>>>> > > >>>>> metrics
> >>>>>>>> > > >>>>>> are mutually exclusive. We can probably have both. It
> is
> >>>>>>>> just that
> >>>>>>>> > > in
> >>>>>>>> > > >>>>>> practice, features like auto-scaling might prefer
> >>>>>>>> time-based
> >>>>>>>> > metrics
> >>>>>>>> > > >> for
> >>>>>>>> > > >>>>>> the reason stated above.
> >>>>>>>> > > >>>>>>
> >>>>>>>> > > >>>>>>> 1. Define the metrics that would allow us to manually
> >>>>>>>> detect
> >>>>>>>> > > >>>>> bottlenecks.
> >>>>>>>> > > >>>>>> As I wrote, we already have them in most of the places,
> >>>>>>>> except of
> >>>>>>>> > > >>>>>> sources/sinks.
> >>>>>>>> > > >>>>>>> 2. Use those metrics, to automatically detect
> >>>>>>>> bottlenecks.
> >>>>>>>> > > Currently
> >>>>>>>> > > >> we
> >>>>>>>> > > >>>>>> are only automatically detecting back pressure and
> >>>>>>>> reporting it to
> >>>>>>>> > > the
> >>>>>>>> > > >>>>> user
> >>>>>>>> > > >>>>>> in web UI (is it exposed as a metric at all?).
> Detecting
> >>>>>>>> the root
> >>>>>>>> > > >> cause
> >>>>>>>> > > >>>>> of
> >>>>>>>> > > >>>>>> the back pressure (bottleneck) is one step further.
> >>>>>>>> > > >>>>>>> 3. Use the knowledge about where exactly the
> bottleneck
> >>>>>>>> is
> >>>>>>>> > located,
> >>>>>>>> > > >> to
> >>>>>>>> > > >>>>>> try to do something with it.
> >>>>>>>> > > >>>>>>
> >>>>>>>> > > >>>>>> As explained above, I think time-based metric also
> >>>>>>>> addresses item
> >>>>>>>> > 1
> >>>>>>>> > > >> and
> >>>>>>>> > > >>>>>> item 2.
> >>>>>>>> > > >>>>>>
> >>>>>>>> > > >>>>>> Any thoughts？
> >>>>>>>> > > >>>>>>
> >>>>>>>> > > >>>>>> Thanks,
> >>>>>>>> > > >>>>>>
> >>>>>>>> > > >>>>>> Jiangjie (Becket) Qin
> >>>>>>>> > > >>>>>>
> >>>>>>>> > > >>>>>>
> >>>>>>>> > > >>>>>>
> >>>>>>>> > > >>>>>> On Mon, Jun 3, 2019 at 4:14 PM Piotr Nowojski <
> >>>>>>>> > piotr@ververica.com>
> >>>>>>>> > > >>>>> wrote:
> >>>>>>>> > > >>>>>>
> >>>>>>>> > > >>>>>>> Hi again :)
> >>>>>>>> > > >>>>>>>
> >>>>>>>> > > >>>>>>>> - pending.bytes, Gauge
> >>>>>>>> > > >>>>>>>> - pending.messages, Gauge
> >>>>>>>> > > >>>>>>>
> >>>>>>>> > > >>>>>>>
> >>>>>>>> > > >>>>>>> +1
> >>>>>>>> > > >>>>>>>
> >>>>>>>> > > >>>>>>> And true, instead of overloading one of the metric it
> >>>>>>>> is better
> >>>>>>>> > > when
> >>>>>>>> > > >>>>> user
> >>>>>>>> > > >>>>>>> can choose to provide only one of them.
> >>>>>>>> > > >>>>>>>
> >>>>>>>> > > >>>>>>> Re 2:
> >>>>>>>> > > >>>>>>>
> >>>>>>>> > > >>>>>>>> If I understand correctly, this metric along with the
> >>>>>>>> pending
> >>>>>>>> > > >> mesages
> >>>>>>>> > > >>>>> /
> >>>>>>>> > > >>>>>>>> bytes would answer the questions of:
> >>>>>>>> > > >>>>>>>
> >>>>>>>> > > >>>>>>>> - Does the connector consume fast enough? Lagging
> >>>>>>>> behind + empty
> >>>>>>>> > > >>>>> buffer
> >>>>>>>> > > >>>>>>> =
> >>>>>>>> > > >>>>>>>> cannot consume fast enough.
> >>>>>>>> > > >>>>>>>> - Does the connector emit fast enough? Lagging behind
> >>>>>>>> + full
> >>>>>>>> > > buffer
> >>>>>>>> > > >> =
> >>>>>>>> > > >>>>>>>> cannot emit fast enough, i.e. the Flink pipeline is
> >>>>>>>> slow.
> >>>>>>>> > > >>>>>>>
> >>>>>>>> > > >>>>>>> Yes, exactly. This can also be used to support
> >>>>>>>> decisions like
> >>>>>>>> > > >> changing
> >>>>>>>> > > >>>>> the
> >>>>>>>> > > >>>>>>> parallelism of the sources and/or down stream
> operators.
> >>>>>>>> > > >>>>>>>
> >>>>>>>> > > >>>>>>> I’m not sure if I understand your proposal with time
> >>>>>>>> based
> >>>>>>>> > > >>>>> measurements.
> >>>>>>>> > > >>>>>>> Maybe I’m missing something, but I do not see how
> >>>>>>>> measuring time
> >>>>>>>> > > >> alone
> >>>>>>>> > > >>>>>>> could answer the problem: where is the bottleneck.
> Time
> >>>>>>>> spent on
> >>>>>>>> > > the
> >>>>>>>> > > >>>>>>> next/emit might be short or long (depending on how
> >>>>>>>> heavy to
> >>>>>>>> > process
> >>>>>>>> > > >> the
> >>>>>>>> > > >>>>>>> record is) and the source can still be
> bottlenecked/back
> >>>>>>>> > pressured
> >>>>>>>> > > or
> >>>>>>>> > > >>>>> not.
> >>>>>>>> > > >>>>>>> Usually the easiest and the most reliable way how to
> >>>>>>>> detect
> >>>>>>>> > > >>>>> bottlenecks is
> >>>>>>>> > > >>>>>>> by checking usage of input & output buffers, since
> when
> >>>>>>>> input
> >>>>>>>> > > buffer
> >>>>>>>> > > >> is
> >>>>>>>> > > >>>>>>> full while output buffer is empty, that’s the
> >>>>>>>> definition of a
> >>>>>>>> > > >>>>> bottleneck.
> >>>>>>>> > > >>>>>>> Also this is usually very easy and cheap to measure
> (it
> >>>>>>>> works
> >>>>>>>> > > >>>>> effectively
> >>>>>>>> > > >>>>>>> the same way as current’s Flink back pressure
> >>>>>>>> monitoring, but
> >>>>>>>> > more
> >>>>>>>> > > >>>>> cleanly,
> >>>>>>>> > > >>>>>>> without probing thread’s stack traces).
> >>>>>>>> > > >>>>>>>
> >>>>>>>> > > >>>>>>> Also keep in mind that we are already using the buffer
> >>>>>>>> usage
> >>>>>>>> > > metrics
> >>>>>>>> > > >>>>> for
> >>>>>>>> > > >>>>>>> detecting the bottlenecks in Flink’s internal network
> >>>>>>>> exchanges
> >>>>>>>> > > >> (manual
> >>>>>>>> > > >>>>>>> work). That’s the reason why I wanted to extend this
> to
> >>>>>>>> > > >> sources/sinks,
> >>>>>>>> > > >>>>>>> since they are currently our blind spot.
> >>>>>>>> > > >>>>>>>
> >>>>>>>> > > >>>>>>>> One feature we are currently working on to scale
> Flink
> >>>>>>>> > > automatically
> >>>>>>>> > > >>>>>>> relies
> >>>>>>>> > > >>>>>>>> on some metrics answering the same question
> >>>>>>>> > > >>>>>>>
> >>>>>>>> > > >>>>>>> That would be very helpful feature. I think in order
> to
> >>>>>>>> achieve
> >>>>>>>> > > that
> >>>>>>>> > > >> we
> >>>>>>>> > > >>>>>>> would need to:
> >>>>>>>> > > >>>>>>> 1. Define the metrics that would allow us to manually
> >>>>>>>> detect
> >>>>>>>> > > >>>>> bottlenecks.
> >>>>>>>> > > >>>>>>> As I wrote, we already have them in most of the
> places,
> >>>>>>>> except of
> >>>>>>>> > > >>>>>>> sources/sinks.
> >>>>>>>> > > >>>>>>> 2. Use those metrics, to automatically detect
> >>>>>>>> bottlenecks.
> >>>>>>>> > > Currently
> >>>>>>>> > > >> we
> >>>>>>>> > > >>>>>>> are only automatically detecting back pressure and
> >>>>>>>> reporting it
> >>>>>>>> > to
> >>>>>>>> > > >> the
> >>>>>>>> > > >>>>> user
> >>>>>>>> > > >>>>>>> in web UI (is it exposed as a metric at all?).
> >>>>>>>> Detecting the root
> >>>>>>>> > > >>>>> cause of
> >>>>>>>> > > >>>>>>> the back pressure (bottleneck) is one step further.
> >>>>>>>> > > >>>>>>> 3. Use the knowledge about where exactly the
> bottleneck
> >>>>>>>> is
> >>>>>>>> > located,
> >>>>>>>> > > >> to
> >>>>>>>> > > >>>>> try
> >>>>>>>> > > >>>>>>> to do something with it.
> >>>>>>>> > > >>>>>>>
> >>>>>>>> > > >>>>>>> I think you are aiming for point 3., but before we
> >>>>>>>> reach it, we
> >>>>>>>> > are
> >>>>>>>> > > >>>>> still
> >>>>>>>> > > >>>>>>> missing 1. & 2. Also even if we have 3., there is a
> >>>>>>>> value in 1 &
> >>>>>>>> > 2
> >>>>>>>> > > >> for
> >>>>>>>> > > >>>>>>> manual analysis/dashboards.
> >>>>>>>> > > >>>>>>>
> >>>>>>>> > > >>>>>>> However, having the knowledge of where the bottleneck
> >>>>>>>> is, doesn’t
> >>>>>>>> > > >>>>>>> necessarily mean that we know what we can do about it.
> >>>>>>>> For
> >>>>>>>> > example
> >>>>>>>> > > >>>>>>> increasing parallelism might or might not help with
> >>>>>>>> anything
> >>>>>>>> > (data
> >>>>>>>> > > >>>>> skew,
> >>>>>>>> > > >>>>>>> bottleneck on some resource that does not scale), but
> >>>>>>>> this remark
> >>>>>>>> > > >>>>> applies
> >>>>>>>> > > >>>>>>> always, regardless of the way how did we detect the
> >>>>>>>> bottleneck.
> >>>>>>>> > > >>>>>>>
> >>>>>>>> > > >>>>>>> Piotrek
> >>>>>>>> > > >>>>>>>
> >>>>>>>> > > >>>>>>>> On 3 Jun 2019, at 06:16, Becket Qin <
> >>>>>>>> becket.qin@gmail.com>
> >>>>>>>> > wrote:
> >>>>>>>> > > >>>>>>>>
> >>>>>>>> > > >>>>>>>> Hi Piotr,
> >>>>>>>> > > >>>>>>>>
> >>>>>>>> > > >>>>>>>> Thanks for the suggestion. Some thoughts below:
> >>>>>>>> > > >>>>>>>>
> >>>>>>>> > > >>>>>>>> Re 1: The pending messages / bytes.
> >>>>>>>> > > >>>>>>>> I completely agree these are very useful metrics and
> >>>>>>>> we should
> >>>>>>>> > > >> expect
> >>>>>>>> > > >>>>> the
> >>>>>>>> > > >>>>>>>> connector to report. WRT the way to expose them, it
> >>>>>>>> seems more
> >>>>>>>> > > >>>>> consistent
> >>>>>>>> > > >>>>>>>> to add two metrics instead of adding a method (unless
> >>>>>>>> there are
> >>>>>>>> > > >> other
> >>>>>>>> > > >>>>> use
> >>>>>>>> > > >>>>>>>> cases other than metric reporting). So we can add the
> >>>>>>>> following
> >>>>>>>> > > two
> >>>>>>>> > > >>>>>>> metrics.
> >>>>>>>> > > >>>>>>>> - pending.bytes, Gauge
> >>>>>>>> > > >>>>>>>> - pending.messages, Gauge
> >>>>>>>> > > >>>>>>>> Applicable connectors can choose to report them.
> These
> >>>>>>>> two
> >>>>>>>> > metrics
> >>>>>>>> > > >>>>> along
> >>>>>>>> > > >>>>>>>> with latency should be sufficient for users to
> >>>>>>>> understand the
> >>>>>>>> > > >> progress
> >>>>>>>> > > >>>>>>> of a
> >>>>>>>> > > >>>>>>>> connector.
> >>>>>>>> > > >>>>>>>>
> >>>>>>>> > > >>>>>>>>
> >>>>>>>> > > >>>>>>>> Re 2: Number of buffered data in-memory of the
> >>>>>>>> connector
> >>>>>>>> > > >>>>>>>> If I understand correctly, this metric along with the
> >>>>>>>> pending
> >>>>>>>> > > >> mesages
> >>>>>>>> > > >>>>> /
> >>>>>>>> > > >>>>>>>> bytes would answer the questions of:
> >>>>>>>> > > >>>>>>>> - Does the connector consume fast enough? Lagging
> >>>>>>>> behind + empty
> >>>>>>>> > > >>>>> buffer
> >>>>>>>> > > >>>>>>> =
> >>>>>>>> > > >>>>>>>> cannot consume fast enough.
> >>>>>>>> > > >>>>>>>> - Does the connector emit fast enough? Lagging behind
> >>>>>>>> + full
> >>>>>>>> > > buffer
> >>>>>>>> > > >> =
> >>>>>>>> > > >>>>>>>> cannot emit fast enough, i.e. the Flink pipeline is
> >>>>>>>> slow.
> >>>>>>>> > > >>>>>>>>
> >>>>>>>> > > >>>>>>>> One feature we are currently working on to scale
> Flink
> >>>>>>>> > > automatically
> >>>>>>>> > > >>>>>>> relies
> >>>>>>>> > > >>>>>>>> on some metrics answering the same question, more
> >>>>>>>> specifically,
> >>>>>>>> > we
> >>>>>>>> > > >> are
> >>>>>>>> > > >>>>>>>> profiling the time spent on .next() method (time to
> >>>>>>>> consume) and
> >>>>>>>> > > the
> >>>>>>>> > > >>>>> time
> >>>>>>>> > > >>>>>>>> spent on .collect() method (time to emit / process).
> >>>>>>>> One
> >>>>>>>> > advantage
> >>>>>>>> > > >> of
> >>>>>>>> > > >>>>>>> such
> >>>>>>>> > > >>>>>>>> method level time cost allows us to calculate the
> >>>>>>>> parallelism
> >>>>>>>> > > >>>>> required to
> >>>>>>>> > > >>>>>>>> keep up in case their is a lag.
> >>>>>>>> > > >>>>>>>>
> >>>>>>>> > > >>>>>>>> However, one concern I have regarding such metric is
> >>>>>>>> that they
> >>>>>>>> > are
> >>>>>>>> > > >>>>>>>> implementation specific. Either profiling on the
> >>>>>>>> method time, or
> >>>>>>>> > > >>>>>>> reporting
> >>>>>>>> > > >>>>>>>> buffer usage assumes the connector are implemented in
> >>>>>>>> such a
> >>>>>>>> > way.
> >>>>>>>> > > A
> >>>>>>>> > > >>>>>>>> slightly better solution might be have the following
> >>>>>>>> metric:
> >>>>>>>> > > >>>>>>>>
> >>>>>>>> > > >>>>>>>> - EmitTimeRatio (or FetchTimeRatio): The time spent
> >>>>>>>> on emitting
> >>>>>>>> > > >>>>>>>> records / Total time elapsed.
> >>>>>>>> > > >>>>>>>>
> >>>>>>>> > > >>>>>>>> This assumes that the source connectors have to emit
> >>>>>>>> the records
> >>>>>>>> > > to
> >>>>>>>> > > >>>>> the
> >>>>>>>> > > >>>>>>>> downstream at some point. The emission may take some
> >>>>>>>> time ( e.g.
> >>>>>>>> > > go
> >>>>>>>> > > >>>>>>> through
> >>>>>>>> > > >>>>>>>> chained operators). And the rest of the time are
> spent
> >>>>>>>> to
> >>>>>>>> > prepare
> >>>>>>>> > > >> the
> >>>>>>>> > > >>>>>>>> record to emit, including time for consuming and
> format
> >>>>>>>> > > conversion,
> >>>>>>>> > > >>>>> etc.
> >>>>>>>> > > >>>>>>>> Ideally, we'd like to see the time spent on record
> >>>>>>>> fetch and
> >>>>>>>> > emit
> >>>>>>>> > > to
> >>>>>>>> > > >>>>> be
> >>>>>>>> > > >>>>>>>> about the same, so no one is bottleneck for the
> other.
> >>>>>>>> > > >>>>>>>>
> >>>>>>>> > > >>>>>>>> The downside of these time based metrics is
> additional
> >>>>>>>> overhead
> >>>>>>>> > to
> >>>>>>>> > > >> get
> >>>>>>>> > > >>>>>>> the
> >>>>>>>> > > >>>>>>>> time, therefore sampling might be needed. But in
> >>>>>>>> practice I feel
> >>>>>>>> > > >> such
> >>>>>>>> > > >>>>>>> time
> >>>>>>>> > > >>>>>>>> based metric might be more useful if we want to take
> >>>>>>>> action.
> >>>>>>>> > > >>>>>>>>
> >>>>>>>> > > >>>>>>>>
> >>>>>>>> > > >>>>>>>> I think we should absolutely add metrics in (1) to
> the
> >>>>>>>> metric
> >>>>>>>> > > >>>>> convention.
> >>>>>>>> > > >>>>>>>> We could also add the metrics mentioned in (2) if we
> >>>>>>>> reach
> >>>>>>>> > > consensus
> >>>>>>>> > > >>>>> on
> >>>>>>>> > > >>>>>>>> that. What do you think?
> >>>>>>>> > > >>>>>>>>
> >>>>>>>> > > >>>>>>>> Thanks,
> >>>>>>>> > > >>>>>>>>
> >>>>>>>> > > >>>>>>>> Jiangjie (Becket) Qin
> >>>>>>>> > > >>>>>>>>
> >>>>>>>> > > >>>>>>>>
> >>>>>>>> > > >>>>>>>> On Fri, May 31, 2019 at 4:26 PM Piotr Nowojski <
> >>>>>>>> > > piotr@ververica.com
> >>>>>>>> > > >>>
> >>>>>>>> > > >>>>>>> wrote:
> >>>>>>>> > > >>>>>>>>
> >>>>>>>> > > >>>>>>>>> Hey Becket,
> >>>>>>>> > > >>>>>>>>>
> >>>>>>>> > > >>>>>>>>> Re 1a) and 1b) +1 from my side.
> >>>>>>>> > > >>>>>>>>>
> >>>>>>>> > > >>>>>>>>> I’ve discussed this issue:
> >>>>>>>> > > >>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>> 2. It would be nice to have metrics, that allow
> us
> >>>>>>>> to check
> >>>>>>>> > > the
> >>>>>>>> > > >>>>> cause
> >>>>>>>> > > >>>>>>>>> of
> >>>>>>>> > > >>>>>>>>>>>> back pressure:
> >>>>>>>> > > >>>>>>>>>>>> a) for sources, length of input queue (in bytes?
> >>>>>>>> Or boolean
> >>>>>>>> > > >>>>>>>>>>>> hasSomethingl/isEmpty)
> >>>>>>>> > > >>>>>>>>>>>> b) for sinks, length of output queue (in bytes?
> Or
> >>>>>>>> boolean
> >>>>>>>> > > >>>>>>>>>>>> hasSomething/isEmpty)
> >>>>>>>> > > >>>>>>>>>
> >>>>>>>> > > >>>>>>>>> With Nico at some lengths and he also saw the
> >>>>>>>> benefits of them.
> >>>>>>>> > > We
> >>>>>>>> > > >>>>> also
> >>>>>>>> > > >>>>>>>>> have more concrete proposal for that.
> >>>>>>>> > > >>>>>>>>>
> >>>>>>>> > > >>>>>>>>> Actually there are two really useful metrics, that
> we
> >>>>>>>> are
> >>>>>>>> > missing
> >>>>>>>> > > >>>>>>>>> currently:
> >>>>>>>> > > >>>>>>>>>
> >>>>>>>> > > >>>>>>>>> 1. Number of data/records/bytes in the backlog to
> >>>>>>>> process. For
> >>>>>>>> > > >>>>> example
> >>>>>>>> > > >>>>>>>>> remaining number of bytes in unread files. Or
> pending
> >>>>>>>> data in
> >>>>>>>> > > Kafka
> >>>>>>>> > > >>>>>>> topics.
> >>>>>>>> > > >>>>>>>>> 2. Number of buffered data in-memory of the
> >>>>>>>> connector, that are
> >>>>>>>> > > >>>>> waiting
> >>>>>>>> > > >>>>>>> to
> >>>>>>>> > > >>>>>>>>> be processed pushed to Flink pipeline.
> >>>>>>>> > > >>>>>>>>>
> >>>>>>>> > > >>>>>>>>> Re 1:
> >>>>>>>> > > >>>>>>>>> This would have to be a metric provided directly by
> a
> >>>>>>>> > connector.
> >>>>>>>> > > It
> >>>>>>>> > > >>>>>>> could
> >>>>>>>> > > >>>>>>>>> be an undefined `int`:
> >>>>>>>> > > >>>>>>>>>
> >>>>>>>> > > >>>>>>>>> `int backlog` - estimate of pending work.
> >>>>>>>> > > >>>>>>>>>
> >>>>>>>> > > >>>>>>>>> “Undefined” meaning that it would be up to a
> >>>>>>>> connector to
> >>>>>>>> > decided
> >>>>>>>> > > >>>>>>> whether
> >>>>>>>> > > >>>>>>>>> it’s measured in bytes, records, pending files or
> >>>>>>>> whatever it
> >>>>>>>> > is
> >>>>>>>> > > >>>>>>> possible
> >>>>>>>> > > >>>>>>>>> to provide by the connector. This is because I
> assume
> >>>>>>>> not every
> >>>>>>>> > > >>>>>>> connector
> >>>>>>>> > > >>>>>>>>> can provide exact number and for some of them it
> >>>>>>>> might be
> >>>>>>>> > > >> impossible
> >>>>>>>> > > >>>>> to
> >>>>>>>> > > >>>>>>>>> provide records number of bytes count.
> >>>>>>>> > > >>>>>>>>>
> >>>>>>>> > > >>>>>>>>> Re 2:
> >>>>>>>> > > >>>>>>>>> This metric could be either provided by a connector,
> >>>>>>>> or
> >>>>>>>> > > calculated
> >>>>>>>> > > >>>>>>> crudely
> >>>>>>>> > > >>>>>>>>> by Flink:
> >>>>>>>> > > >>>>>>>>>
> >>>>>>>> > > >>>>>>>>> `float bufferUsage` - value from [0.0, 1.0] range
> >>>>>>>> > > >>>>>>>>>
> >>>>>>>> > > >>>>>>>>> Percentage of used in memory buffers, like in
> Kafka’s
> >>>>>>>> handover.
> >>>>>>>> > > >>>>>>>>>
> >>>>>>>> > > >>>>>>>>> It could be crudely implemented by Flink with
> FLIP-27
> >>>>>>>> > > >>>>>>>>> SourceReader#isAvailable. If SourceReader is not
> >>>>>>>> available
> >>>>>>>> > > reported
> >>>>>>>> > > >>>>>>>>> `bufferUsage` could be 0.0. If it is available, it
> >>>>>>>> could be
> >>>>>>>> > 1.0.
> >>>>>>>> > > I
> >>>>>>>> > > >>>>> think
> >>>>>>>> > > >>>>>>>>> this would be a good enough estimation for most of
> >>>>>>>> the use
> >>>>>>>> > cases
> >>>>>>>> > > >>>>> (that
> >>>>>>>> > > >>>>>>>>> could be overloaded and implemented better if
> >>>>>>>> desired).
> >>>>>>>> > > Especially
> >>>>>>>> > > >>>>>>> since we
> >>>>>>>> > > >>>>>>>>> are reporting only probed values: if probed values
> >>>>>>>> are almost
> >>>>>>>> > > >> always
> >>>>>>>> > > >>>>>>> “1.0”,
> >>>>>>>> > > >>>>>>>>> it would mean that we have a back pressure. If they
> >>>>>>>> are almost
> >>>>>>>> > > >> always
> >>>>>>>> > > >>>>>>>>> “0.0”, there is probably no back pressure at the
> >>>>>>>> sources.
> >>>>>>>> > > >>>>>>>>>
> >>>>>>>> > > >>>>>>>>> What do you think about this?
> >>>>>>>> > > >>>>>>>>>
> >>>>>>>> > > >>>>>>>>> Piotrek
> >>>>>>>> > > >>>>>>>>>
> >>>>>>>> > > >>>>>>>>>> On 30 May 2019, at 11:41, Becket Qin <
> >>>>>>>> becket.qin@gmail.com>
> >>>>>>>> > > >> wrote:
> >>>>>>>> > > >>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>> Hi all,
> >>>>>>>> > > >>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>> Thanks a lot for all the feedback and comments. I'd
> >>>>>>>> like to
> >>>>>>>> > > >> continue
> >>>>>>>> > > >>>>>>> the
> >>>>>>>> > > >>>>>>>>>> discussion on this FLIP.
> >>>>>>>> > > >>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>> I updated the FLIP-33 wiki to remove all the
> >>>>>>>> histogram metrics
> >>>>>>>> > > >> from
> >>>>>>>> > > >>>>> the
> >>>>>>>> > > >>>>>>>>>> first version of metric convention due to the
> >>>>>>>> performance
> >>>>>>>> > > concern.
> >>>>>>>> > > >>>>> The
> >>>>>>>> > > >>>>>>>>> plan
> >>>>>>>> > > >>>>>>>>>> is to introduce them later when we have a mechanism
> >>>>>>>> to opt
> >>>>>>>> > > in/out
> >>>>>>>> > > >>>>>>>>> metrics.
> >>>>>>>> > > >>>>>>>>>> At that point, users can decide whether they want
> to
> >>>>>>>> pay the
> >>>>>>>> > > cost
> >>>>>>>> > > >> to
> >>>>>>>> > > >>>>>>> get
> >>>>>>>> > > >>>>>>>>>> the metric or not.
> >>>>>>>> > > >>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>> As Stephan suggested, for this FLIP, let's first
> try
> >>>>>>>> to agree
> >>>>>>>> > on
> >>>>>>>> > > >> the
> >>>>>>>> > > >>>>>>>>> small
> >>>>>>>> > > >>>>>>>>>> list of conventional metrics that connectors should
> >>>>>>>> follow.
> >>>>>>>> > > >>>>>>>>>> Just to be clear, the purpose of the convention is
> >>>>>>>> not to
> >>>>>>>> > > enforce
> >>>>>>>> > > >>>>> every
> >>>>>>>> > > >>>>>>>>>> connector to report all these metrics, but to
> >>>>>>>> provide a
> >>>>>>>> > guidance
> >>>>>>>> > > >> in
> >>>>>>>> > > >>>>>>> case
> >>>>>>>> > > >>>>>>>>>> these metrics are reported by some connectors.
> >>>>>>>> > > >>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>> @ Stephan & Chesnay,
> >>>>>>>> > > >>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>> Regarding the duplication of `RecordsIn` metric in
> >>>>>>>> operator /
> >>>>>>>> > > task
> >>>>>>>> > > >>>>>>>>>> IOMetricGroups, from what I understand, for source
> >>>>>>>> operator,
> >>>>>>>> > it
> >>>>>>>> > > is
> >>>>>>>> > > >>>>>>>>> actually
> >>>>>>>> > > >>>>>>>>>> the SourceFunction that reports the operator level
> >>>>>>>> > > >>>>>>>>>> RecordsIn/RecordsInPerSecond metric. So they are
> >>>>>>>> essentially
> >>>>>>>> > the
> >>>>>>>> > > >>>>> same
> >>>>>>>> > > >>>>>>>>>> metric in the operator level IOMetricGroup.
> >>>>>>>> Similarly for the
> >>>>>>>> > > Sink
> >>>>>>>> > > >>>>>>>>>> operator, the operator level
> >>>>>>>> RecordsOut/RecordsOutPerSecond
> >>>>>>>> > > >> metrics
> >>>>>>>> > > >>>>> are
> >>>>>>>> > > >>>>>>>>>> also reported by the Sink function. I marked them
> as
> >>>>>>>> existing
> >>>>>>>> > in
> >>>>>>>> > > >> the
> >>>>>>>> > > >>>>>>>>>> FLIP-33 wiki page. Please let me know if I
> >>>>>>>> misunderstood.
> >>>>>>>> > > >>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>> Thanks,
> >>>>>>>> > > >>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>> Jiangjie (Becket) Qin
> >>>>>>>> > > >>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>> On Thu, May 30, 2019 at 5:16 PM Becket Qin <
> >>>>>>>> > > becket.qin@gmail.com>
> >>>>>>>> > > >>>>>>> wrote:
> >>>>>>>> > > >>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>> Hi Piotr,
> >>>>>>>> > > >>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>> Thanks a lot for the feedback.
> >>>>>>>> > > >>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>> 1a) I guess you are referring to the part that
> >>>>>>>> "original
> >>>>>>>> > system
> >>>>>>>> > > >>>>>>> specific
> >>>>>>>> > > >>>>>>>>>>> metrics should also be reported". The performance
> >>>>>>>> impact
> >>>>>>>> > > depends
> >>>>>>>> > > >> on
> >>>>>>>> > > >>>>>>> the
> >>>>>>>> > > >>>>>>>>>>> implementation. An efficient implementation would
> >>>>>>>> only record
> >>>>>>>> > > the
> >>>>>>>> > > >>>>>>> metric
> >>>>>>>> > > >>>>>>>>>>> once, but report them with two different metric
> >>>>>>>> names. This
> >>>>>>>> > is
> >>>>>>>> > > >>>>>>> unlikely
> >>>>>>>> > > >>>>>>>>> to
> >>>>>>>> > > >>>>>>>>>>> hurt performance.
> >>>>>>>> > > >>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>> 1b) Yes, I agree that we should avoid adding
> >>>>>>>> overhead to the
> >>>>>>>> > > >>>>> critical
> >>>>>>>> > > >>>>>>>>> path
> >>>>>>>> > > >>>>>>>>>>> by all means. This is sometimes a tradeoff,
> running
> >>>>>>>> blindly
> >>>>>>>> > > >> without
> >>>>>>>> > > >>>>>>> any
> >>>>>>>> > > >>>>>>>>>>> metric gives best performance, but sometimes might
> >>>>>>>> be
> >>>>>>>> > > frustrating
> >>>>>>>> > > >>>>> when
> >>>>>>>> > > >>>>>>>>> we
> >>>>>>>> > > >>>>>>>>>>> debug some issues.
> >>>>>>>> > > >>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>> 2. The metrics are indeed very useful. Are they
> >>>>>>>> supposed to
> >>>>>>>> > be
> >>>>>>>> > > >>>>>>> reported
> >>>>>>>> > > >>>>>>>>> by
> >>>>>>>> > > >>>>>>>>>>> the connectors or Flink itself? At this point
> >>>>>>>> FLIP-33 is more
> >>>>>>>> > > >>>>> focused
> >>>>>>>> > > >>>>>>> on
> >>>>>>>> > > >>>>>>>>>>> provide a guidance to the connector authors on the
> >>>>>>>> metrics
> >>>>>>>> > > >>>>> reporting.
> >>>>>>>> > > >>>>>>>>> That
> >>>>>>>> > > >>>>>>>>>>> said, after FLIP-27, I think we should absolutely
> >>>>>>>> report
> >>>>>>>> > these
> >>>>>>>> > > >>>>> metrics
> >>>>>>>> > > >>>>>>>>> in
> >>>>>>>> > > >>>>>>>>>>> the abstract implementation. In any case, the
> metric
> >>>>>>>> > convention
> >>>>>>>> > > >> in
> >>>>>>>> > > >>>>>>> this
> >>>>>>>> > > >>>>>>>>>>> list are expected to evolve over time.
> >>>>>>>> > > >>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>> Thanks,
> >>>>>>>> > > >>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>> Jiangjie (Becket) Qin
> >>>>>>>> > > >>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>> On Tue, May 28, 2019 at 6:24 PM Piotr Nowojski <
> >>>>>>>> > > >>>>> piotr@ververica.com>
> >>>>>>>> > > >>>>>>>>>>> wrote:
> >>>>>>>> > > >>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>> Hi,
> >>>>>>>> > > >>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>> Thanks for the proposal and driving the effort
> >>>>>>>> here Becket
> >>>>>>>> > :)
> >>>>>>>> > > >> I’ve
> >>>>>>>> > > >>>>>>> read
> >>>>>>>> > > >>>>>>>>>>>> through the FLIP-33 [1], and here are couple of
> my
> >>>>>>>> thoughts.
> >>>>>>>> > > >>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>> Big +1 for standardising the metric names between
> >>>>>>>> > connectors,
> >>>>>>>> > > it
> >>>>>>>> > > >>>>> will
> >>>>>>>> > > >>>>>>>>>>>> definitely help us and users a lot.
> >>>>>>>> > > >>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>> Issues/questions/things to discuss that I’ve
> >>>>>>>> thought of:
> >>>>>>>> > > >>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>> 1a. If we are about to duplicate some metrics,
> can
> >>>>>>>> this
> >>>>>>>> > > become a
> >>>>>>>> > > >>>>>>>>>>>> performance issue?
> >>>>>>>> > > >>>>>>>>>>>> 1b. Generally speaking, we should make sure that
> >>>>>>>> collecting
> >>>>>>>> > > >> those
> >>>>>>>> > > >>>>>>>>> metrics
> >>>>>>>> > > >>>>>>>>>>>> is as non intrusive as possible, especially that
> >>>>>>>> they will
> >>>>>>>> > > need
> >>>>>>>> > > >>>>> to be
> >>>>>>>> > > >>>>>>>>>>>> updated once per record. (They might be collected
> >>>>>>>> more
> >>>>>>>> > rarely
> >>>>>>>> > > >> with
> >>>>>>>> > > >>>>>>> some
> >>>>>>>> > > >>>>>>>>>>>> overhead, but the hot path of updating it per
> >>>>>>>> record will
> >>>>>>>> > need
> >>>>>>>> > > >> to
> >>>>>>>> > > >>>>> be
> >>>>>>>> > > >>>>>>> as
> >>>>>>>> > > >>>>>>>>>>>> quick as possible). That includes both avoiding
> >>>>>>>> heavy
> >>>>>>>> > > >> computation
> >>>>>>>> > > >>>>> on
> >>>>>>>> > > >>>>>>>>> per
> >>>>>>>> > > >>>>>>>>>>>> record path: histograms?, measuring time for time
> >>>>>>>> based
> >>>>>>>> > > metrics
> >>>>>>>> > > >>>>> (per
> >>>>>>>> > > >>>>>>>>>>>> second) (System.currentTimeMillis() depending on
> >>>>>>>> the
> >>>>>>>> > > >>>>> implementation
> >>>>>>>> > > >>>>>>> can
> >>>>>>>> > > >>>>>>>>>>>> invoke a system call)
> >>>>>>>> > > >>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>> 2. It would be nice to have metrics, that allow
> us
> >>>>>>>> to check
> >>>>>>>> > > the
> >>>>>>>> > > >>>>> cause
> >>>>>>>> > > >>>>>>>>> of
> >>>>>>>> > > >>>>>>>>>>>> back pressure:
> >>>>>>>> > > >>>>>>>>>>>> a) for sources, length of input queue (in bytes?
> >>>>>>>> Or boolean
> >>>>>>>> > > >>>>>>>>>>>> hasSomethingl/isEmpty)
> >>>>>>>> > > >>>>>>>>>>>> b) for sinks, length of output queue (in bytes?
> Or
> >>>>>>>> boolean
> >>>>>>>> > > >>>>>>>>>>>> hasSomething/isEmpty)
> >>>>>>>> > > >>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>> a) is useful in a scenario when we are processing
> >>>>>>>> backlog of
> >>>>>>>> > > >>>>> records,
> >>>>>>>> > > >>>>>>>>> all
> >>>>>>>> > > >>>>>>>>>>>> of the internal Flink’s input/output network
> >>>>>>>> buffers are
> >>>>>>>> > > empty,
> >>>>>>>> > > >>>>> and
> >>>>>>>> > > >>>>>>> we
> >>>>>>>> > > >>>>>>>>> want
> >>>>>>>> > > >>>>>>>>>>>> to check whether the external source system is
> the
> >>>>>>>> > bottleneck
> >>>>>>>> > > >>>>>>> (source’s
> >>>>>>>> > > >>>>>>>>>>>> input queue will be empty), or if the Flink’s
> >>>>>>>> connector is
> >>>>>>>> > the
> >>>>>>>> > > >>>>>>>>> bottleneck
> >>>>>>>> > > >>>>>>>>>>>> (source’s input queues will be full).
> >>>>>>>> > > >>>>>>>>>>>> b) similar story. Backlog of records, but this
> >>>>>>>> time all of
> >>>>>>>> > the
> >>>>>>>> > > >>>>>>> internal
> >>>>>>>> > > >>>>>>>>>>>> Flink’s input/ouput network buffers are full, and
> >>>>>>>> we want o
> >>>>>>>> > > >> check
> >>>>>>>> > > >>>>>>>>> whether
> >>>>>>>> > > >>>>>>>>>>>> the external sink system is the bottleneck (sink
> >>>>>>>> output
> >>>>>>>> > queues
> >>>>>>>> > > >> are
> >>>>>>>> > > >>>>>>>>> full),
> >>>>>>>> > > >>>>>>>>>>>> or if the Flink’s connector is the bottleneck
> >>>>>>>> (sink’s output
> >>>>>>>> > > >>>>> queues
> >>>>>>>> > > >>>>>>>>> will be
> >>>>>>>> > > >>>>>>>>>>>> empty)
> >>>>>>>> > > >>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>> It might be sometimes difficult to provide those
> >>>>>>>> metrics, so
> >>>>>>>> > > >> they
> >>>>>>>> > > >>>>>>> could
> >>>>>>>> > > >>>>>>>>>>>> be optional, but if we could provide them, it
> >>>>>>>> would be
> >>>>>>>> > really
> >>>>>>>> > > >>>>>>> helpful.
> >>>>>>>> > > >>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>> Piotrek
> >>>>>>>> > > >>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>> [1]
> >>>>>>>> > > >>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>
> >>>>>>>> > > >>>>>>>
> >>>>>>>> > > >>>>>
> >>>>>>>> > > >>
> >>>>>>>> > >
> >>>>>>>> >
> >>>>>>>>
> https://cwiki.apache.org/confluence/display/FLINK/FLIP-33:+Standardize+Connector+Metrics
> >>>>>>>> > > >>>>>>>>>>>> <
> >>>>>>>> > > >>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>
> >>>>>>>> > > >>>>>>>
> >>>>>>>> > > >>>>>
> >>>>>>>> > > >>
> >>>>>>>> > >
> >>>>>>>> >
> >>>>>>>>
> https://cwiki.apache.org/confluence/display/FLINK/FLIP-33:+Standardize+Connector+Metrics
> >>>>>>>> > > >>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>> On 24 Apr 2019, at 13:28, Stephan Ewen <
> >>>>>>>> sewen@apache.org>
> >>>>>>>> > > >> wrote:
> >>>>>>>> > > >>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>> I think this sounds reasonable.
> >>>>>>>> > > >>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>> Let's keep the "reconfiguration without stopping
> >>>>>>>> the job"
> >>>>>>>> > out
> >>>>>>>> > > >> of
> >>>>>>>> > > >>>>>>> this,
> >>>>>>>> > > >>>>>>>>>>>>> because that would be a super big effort and if
> >>>>>>>> we approach
> >>>>>>>> > > >> that,
> >>>>>>>> > > >>>>>>> then
> >>>>>>>> > > >>>>>>>>>>>> in
> >>>>>>>> > > >>>>>>>>>>>>> more generic way rather than specific to
> >>>>>>>> connector metrics.
> >>>>>>>> > > >>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>> I would suggest to look at the following things
> >>>>>>>> before
> >>>>>>>> > > starting
> >>>>>>>> > > >>>>> with
> >>>>>>>> > > >>>>>>>>> any
> >>>>>>>> > > >>>>>>>>>>>>> implementation work:
> >>>>>>>> > > >>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>> - Try and find a committer to support this,
> >>>>>>>> otherwise it
> >>>>>>>> > will
> >>>>>>>> > > >> be
> >>>>>>>> > > >>>>>>> hard
> >>>>>>>> > > >>>>>>>>>>>> to
> >>>>>>>> > > >>>>>>>>>>>>> make progress
> >>>>>>>> > > >>>>>>>>>>>>> - Start with defining a smaller set of "core
> >>>>>>>> metrics" and
> >>>>>>>> > > >> extend
> >>>>>>>> > > >>>>> the
> >>>>>>>> > > >>>>>>>>>>>> set
> >>>>>>>> > > >>>>>>>>>>>>> later. I think that is easier than now blocking
> >>>>>>>> on reaching
> >>>>>>>> > > >>>>>>> consensus
> >>>>>>>> > > >>>>>>>>>>>> on a
> >>>>>>>> > > >>>>>>>>>>>>> large group of metrics.
> >>>>>>>> > > >>>>>>>>>>>>> - Find a solution to the problem Chesnay
> >>>>>>>> mentioned, that
> >>>>>>>> > the
> >>>>>>>> > > >>>>>>> "records
> >>>>>>>> > > >>>>>>>>>>>> in"
> >>>>>>>> > > >>>>>>>>>>>>> metric is somehow overloaded and exists already
> >>>>>>>> in the IO
> >>>>>>>> > > >> Metric
> >>>>>>>> > > >>>>>>>>> group.
> >>>>>>>> > > >>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>> On Mon, Mar 25, 2019 at 7:16 AM Becket Qin <
> >>>>>>>> > > >> becket.qin@gmail.com
> >>>>>>>> > > >>>>>>
> >>>>>>>> > > >>>>>>>>>>>> wrote:
> >>>>>>>> > > >>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>> Hi Stephan,
> >>>>>>>> > > >>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>> Thanks a lot for the feedback. All makes sense.
> >>>>>>>> > > >>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>> It is a good suggestion to simply have an
> >>>>>>>> > onRecord(numBytes,
> >>>>>>>> > > >>>>>>>>> eventTime)
> >>>>>>>> > > >>>>>>>>>>>>>> method for connector writers. It should meet
> >>>>>>>> most of the
> >>>>>>>> > > >>>>>>>>> requirements,
> >>>>>>>> > > >>>>>>>>>>>>>> individual
> >>>>>>>> > > >>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>> The configurable metrics feature is something
> >>>>>>>> really
> >>>>>>>> > useful,
> >>>>>>>> > > >>>>>>>>>>>> especially if
> >>>>>>>> > > >>>>>>>>>>>>>> we can somehow make it dynamically configurable
> >>>>>>>> without
> >>>>>>>> > > >> stopping
> >>>>>>>> > > >>>>>>> the
> >>>>>>>> > > >>>>>>>>>>>> jobs.
> >>>>>>>> > > >>>>>>>>>>>>>> It might be better to make it a separate
> >>>>>>>> discussion
> >>>>>>>> > because
> >>>>>>>> > > it
> >>>>>>>> > > >>>>> is a
> >>>>>>>> > > >>>>>>>>>>>> more
> >>>>>>>> > > >>>>>>>>>>>>>> generic feature instead of only for connectors.
> >>>>>>>> > > >>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>> So in order to make some progress, in this FLIP
> >>>>>>>> we can
> >>>>>>>> > limit
> >>>>>>>> > > >> the
> >>>>>>>> > > >>>>>>>>>>>> discussion
> >>>>>>>> > > >>>>>>>>>>>>>> scope to the connector related items:
> >>>>>>>> > > >>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>> - the standard connector metric names and
> types.
> >>>>>>>> > > >>>>>>>>>>>>>> - the abstract ConnectorMetricHandler interface
> >>>>>>>> > > >>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>> I'll start a separate thread to discuss other
> >>>>>>>> general
> >>>>>>>> > metric
> >>>>>>>> > > >>>>>>> related
> >>>>>>>> > > >>>>>>>>>>>>>> enhancement items including:
> >>>>>>>> > > >>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>> - optional metrics
> >>>>>>>> > > >>>>>>>>>>>>>> - dynamic metric configuration
> >>>>>>>> > > >>>>>>>>>>>>>> - potential combination with rate limiter
> >>>>>>>> > > >>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>> Does this plan sound reasonable?
> >>>>>>>> > > >>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>> Thanks,
> >>>>>>>> > > >>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>> Jiangjie (Becket) Qin
> >>>>>>>> > > >>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>> On Sat, Mar 23, 2019 at 5:53 AM Stephan Ewen <
> >>>>>>>> > > >> sewen@apache.org>
> >>>>>>>> > > >>>>>>>>> wrote:
> >>>>>>>> > > >>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>> Ignoring for a moment implementation details,
> >>>>>>>> this
> >>>>>>>> > > connector
> >>>>>>>> > > >>>>>>> metrics
> >>>>>>>> > > >>>>>>>>>>>> work
> >>>>>>>> > > >>>>>>>>>>>>>>> is a really good thing to do, in my opinion
> >>>>>>>> > > >>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>> The questions "oh, my job seems to be doing
> >>>>>>>> nothing, I am
> >>>>>>>> > > >>>>> looking
> >>>>>>>> > > >>>>>>> at
> >>>>>>>> > > >>>>>>>>>>>> the
> >>>>>>>> > > >>>>>>>>>>>>>> UI
> >>>>>>>> > > >>>>>>>>>>>>>>> and the 'records in' value is still zero" is
> in
> >>>>>>>> the top
> >>>>>>>> > > three
> >>>>>>>> > > >>>>>>>>> support
> >>>>>>>> > > >>>>>>>>>>>>>>> questions I have been asked personally.
> >>>>>>>> > > >>>>>>>>>>>>>>> Introspection into "how far is the consumer
> >>>>>>>> lagging
> >>>>>>>> > behind"
> >>>>>>>> > > >>>>> (event
> >>>>>>>> > > >>>>>>>>>>>> time
> >>>>>>>> > > >>>>>>>>>>>>>>> fetch latency) came up many times as well.
> >>>>>>>> > > >>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>> So big +1 to solving this problem.
> >>>>>>>> > > >>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>> About the exact design - I would try to go for
> >>>>>>>> the
> >>>>>>>> > > following
> >>>>>>>> > > >>>>>>>>>>>> properties:
> >>>>>>>> > > >>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>> - keep complexity of of connectors. Ideally
> the
> >>>>>>>> metrics
> >>>>>>>> > > >> handler
> >>>>>>>> > > >>>>>>> has
> >>>>>>>> > > >>>>>>>>> a
> >>>>>>>> > > >>>>>>>>>>>>>>> single onRecord(numBytes, eventTime) method or
> >>>>>>>> so, and
> >>>>>>>> > > >>>>> everything
> >>>>>>>> > > >>>>>>>>>>>> else is
> >>>>>>>> > > >>>>>>>>>>>>>>> internal to the handler. That makes it dead
> >>>>>>>> simple for
> >>>>>>>> > the
> >>>>>>>> > > >>>>>>>>> connector.
> >>>>>>>> > > >>>>>>>>>>>> We
> >>>>>>>> > > >>>>>>>>>>>>>>> can also think of an extensive scheme for
> >>>>>>>> connector
> >>>>>>>> > > specific
> >>>>>>>> > > >>>>>>>>> metrics.
> >>>>>>>> > > >>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>> - make it configurable on the job it cluster
> >>>>>>>> level which
> >>>>>>>> > > >>>>> metrics
> >>>>>>>> > > >>>>>>> the
> >>>>>>>> > > >>>>>>>>>>>>>>> handler internally creates when that method is
> >>>>>>>> invoked.
> >>>>>>>> > > >>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>> What do you think?
> >>>>>>>> > > >>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>> Best,
> >>>>>>>> > > >>>>>>>>>>>>>>> Stephan
> >>>>>>>> > > >>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>> On Thu, Mar 21, 2019 at 10:42 AM Chesnay
> >>>>>>>> Schepler <
> >>>>>>>> > > >>>>>>>>> chesnay@apache.org
> >>>>>>>> > > >>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>> wrote:
> >>>>>>>> > > >>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>> As I said before, I believe this to be
> >>>>>>>> over-engineered
> >>>>>>>> > and
> >>>>>>>> > > >>>>> have
> >>>>>>>> > > >>>>>>> no
> >>>>>>>> > > >>>>>>>>>>>>>>>> interest in this implementation.
> >>>>>>>> > > >>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>> There are conceptual issues like defining a
> >>>>>>>> duplicate
> >>>>>>>> > > >>>>>>>>>>>>>> numBytesIn(PerSec)
> >>>>>>>> > > >>>>>>>>>>>>>>>> metric that already exists for each operator.
> >>>>>>>> > > >>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>> On 21.03.2019 06:13, Becket Qin wrote:
> >>>>>>>> > > >>>>>>>>>>>>>>>>> A few updates to the thread. I uploaded a
> >>>>>>>> patch[1] as a
> >>>>>>>> > > >>>>> complete
> >>>>>>>> > > >>>>>>>>>>>>>>>>> example of how users can use the metrics in
> >>>>>>>> the future.
> >>>>>>>> > > >>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>> Some thoughts below after taking a look at
> the
> >>>>>>>> > > >>>>>>> AbstractMetricGroup
> >>>>>>>> > > >>>>>>>>>>>>>> and
> >>>>>>>> > > >>>>>>>>>>>>>>>>> its subclasses.
> >>>>>>>> > > >>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>> This patch intends to provide convenience
> for
> >>>>>>>> Flink
> >>>>>>>> > > >> connector
> >>>>>>>> > > >>>>>>>>>>>>>>>>> implementations to follow metrics standards
> >>>>>>>> proposed in
> >>>>>>>> > > >>>>> FLIP-33.
> >>>>>>>> > > >>>>>>>>> It
> >>>>>>>> > > >>>>>>>>>>>>>>>>> also try to enhance the metric management in
> >>>>>>>> general
> >>>>>>>> > way
> >>>>>>>> > > to
> >>>>>>>> > > >>>>> help
> >>>>>>>> > > >>>>>>>>>>>>>> users
> >>>>>>>> > > >>>>>>>>>>>>>>>>> with:
> >>>>>>>> > > >>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>> 1. metric definition
> >>>>>>>> > > >>>>>>>>>>>>>>>>> 2. metric dependencies check
> >>>>>>>> > > >>>>>>>>>>>>>>>>> 3. metric validation
> >>>>>>>> > > >>>>>>>>>>>>>>>>> 4. metric control (turn on / off particular
> >>>>>>>> metrics)
> >>>>>>>> > > >>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>> This patch wraps |MetricGroup| to extend the
> >>>>>>>> > > functionality
> >>>>>>>> > > >> of
> >>>>>>>> > > >>>>>>>>>>>>>>>>> |AbstractMetricGroup| and its subclasses.
> The
> >>>>>>>> > > >>>>>>>>>>>>>>>>> |AbstractMetricGroup| mainly focus on the
> >>>>>>>> metric group
> >>>>>>>> > > >>>>>>> hierarchy,
> >>>>>>>> > > >>>>>>>>>>>> but
> >>>>>>>> > > >>>>>>>>>>>>>>>>> does not really manage the metrics other
> than
> >>>>>>>> keeping
> >>>>>>>> > > them
> >>>>>>>> > > >>>>> in a
> >>>>>>>> > > >>>>>>>>> Map.
> >>>>>>>> > > >>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>> Ideally we should only have one entry point
> >>>>>>>> for the
> >>>>>>>> > > >> metrics.
> >>>>>>>> > > >>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>> Right now the entry point is
> >>>>>>>> |AbstractMetricGroup|.
> >>>>>>>> > > >> However,
> >>>>>>>> > > >>>>>>>>> besides
> >>>>>>>> > > >>>>>>>>>>>>>>>>> the missing functionality mentioned above,
> >>>>>>>> > > >>>>> |AbstractMetricGroup|
> >>>>>>>> > > >>>>>>>>>>>>>> seems
> >>>>>>>> > > >>>>>>>>>>>>>>>>> deeply rooted in Flink runtime. We could
> >>>>>>>> extract it out
> >>>>>>>> > > to
> >>>>>>>> > > >>>>>>>>>>>>>>>>> flink-metrics in order to use it for generic
> >>>>>>>> purpose.
> >>>>>>>> > > There
> >>>>>>>> > > >>>>> will
> >>>>>>>> > > >>>>>>>>> be
> >>>>>>>> > > >>>>>>>>>>>>>>>>> some work, though.
> >>>>>>>> > > >>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>> Another approach is to make
> |AbstractMetrics|
> >>>>>>>> in this
> >>>>>>>> > > patch
> >>>>>>>> > > >>>>> as
> >>>>>>>> > > >>>>>>> the
> >>>>>>>> > > >>>>>>>>>>>>>>>>> metric entry point. It wraps metric group
> and
> >>>>>>>> provides
> >>>>>>>> > > the
> >>>>>>>> > > >>>>>>> missing
> >>>>>>>> > > >>>>>>>>>>>>>>>>> functionalities. Then we can roll out this
> >>>>>>>> pattern to
> >>>>>>>> > > >> runtime
> >>>>>>>> > > >>>>>>>>>>>>>>>>> components gradually as well.
> >>>>>>>> > > >>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>> My first thought is that the latter approach
> >>>>>>>> gives a
> >>>>>>>> > more
> >>>>>>>> > > >>>>> smooth
> >>>>>>>> > > >>>>>>>>>>>>>>>>> migration. But I am also OK with doing a
> >>>>>>>> refactoring on
> >>>>>>>> > > the
> >>>>>>>> > > >>>>>>>>>>>>>>>>> |AbstractMetricGroup| family.
> >>>>>>>> > > >>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>> Thanks,
> >>>>>>>> > > >>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>> Jiangjie (Becket) Qin
> >>>>>>>> > > >>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>> [1]
> https://github.com/becketqin/flink/pull/1
> >>>>>>>> > > >>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>> On Mon, Feb 25, 2019 at 2:32 PM Becket Qin <
> >>>>>>>> > > >>>>>>> becket.qin@gmail.com
> >>>>>>>> > > >>>>>>>>>>>>>>>>> <ma...@gmail.com>> wrote:
> >>>>>>>> > > >>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>> Hi Chesnay,
> >>>>>>>> > > >>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>> It might be easier to discuss some
> >>>>>>>> implementation
> >>>>>>>> > details
> >>>>>>>> > > >> in
> >>>>>>>> > > >>>>>>> the
> >>>>>>>> > > >>>>>>>>>>>>>>>>> PR review instead of in the FLIP discussion
> >>>>>>>> thread. I
> >>>>>>>> > > have
> >>>>>>>> > > >> a
> >>>>>>>> > > >>>>>>>>>>>>>> patch
> >>>>>>>> > > >>>>>>>>>>>>>>>>> for Kafka connectors ready but haven't
> >>>>>>>> submitted the PR
> >>>>>>>> > > >> yet.
> >>>>>>>> > > >>>>>>>>>>>>>>>>> Hopefully that will help explain a bit more.
> >>>>>>>> > > >>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>> ** Re: metric type binding
> >>>>>>>> > > >>>>>>>>>>>>>>>>> This is a valid point that worths
> discussing.
> >>>>>>>> If I
> >>>>>>>> > > >> understand
> >>>>>>>> > > >>>>>>>>>>>>>>>>> correctly, there are two points:
> >>>>>>>> > > >>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>> 1. Metric type / interface does not matter
> as
> >>>>>>>> long as
> >>>>>>>> > the
> >>>>>>>> > > >>>>>>> metric
> >>>>>>>> > > >>>>>>>>>>>>>>>>> semantic is clearly defined.
> >>>>>>>> > > >>>>>>>>>>>>>>>>> Conceptually speaking, I agree that as long
> >>>>>>>> as the
> >>>>>>>> > metric
> >>>>>>>> > > >>>>>>>>>>>>>> semantic
> >>>>>>>> > > >>>>>>>>>>>>>>>>> is defined, metric type does not matter. To
> >>>>>>>> some
> >>>>>>>> > extent,
> >>>>>>>> > > >>>>> Gauge
> >>>>>>>> > > >>>>>>> /
> >>>>>>>> > > >>>>>>>>>>>>>>>>> Counter / Meter / Histogram themselves can
> be
> >>>>>>>> think of
> >>>>>>>> > as
> >>>>>>>> > > >>>>> some
> >>>>>>>> > > >>>>>>>>>>>>>>>>> well-recognized semantics, if you wish. In
> >>>>>>>> Flink, these
> >>>>>>>> > > >>>>> metric
> >>>>>>>> > > >>>>>>>>>>>>>>>>> semantics have their associated interface
> >>>>>>>> classes. In
> >>>>>>>> > > >>>>> practice,
> >>>>>>>> > > >>>>>>>>>>>>>>>>> such semantic to interface binding seems
> >>>>>>>> necessary for
> >>>>>>>> > > >>>>>>> different
> >>>>>>>> > > >>>>>>>>>>>>>>>>> components to communicate. Simply
> >>>>>>>> standardize the
> >>>>>>>> > > semantic
> >>>>>>>> > > >>>>> of
> >>>>>>>> > > >>>>>>>>>>>>>> the
> >>>>>>>> > > >>>>>>>>>>>>>>>>> connector metrics seems not sufficient for
> >>>>>>>> people to
> >>>>>>>> > > build
> >>>>>>>> > > >>>>>>>>>>>>>>>>> ecosystem on top of. At the end of the day,
> >>>>>>>> we still
> >>>>>>>> > need
> >>>>>>>> > > >> to
> >>>>>>>> > > >>>>>>>>> have
> >>>>>>>> > > >>>>>>>>>>>>>>>>> some embodiment of the metric semantics that
> >>>>>>>> people can
> >>>>>>>> > > >>>>> program
> >>>>>>>> > > >>>>>>>>>>>>>>>>> against.
> >>>>>>>> > > >>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>> 2. Sometimes the same metric semantic can be
> >>>>>>>> exposed
> >>>>>>>> > > using
> >>>>>>>> > > >>>>>>>>>>>>>>>>> different metric types / interfaces.
> >>>>>>>> > > >>>>>>>>>>>>>>>>> This is a good point. Counter and
> >>>>>>>> Gauge-as-a-Counter
> >>>>>>>> > are
> >>>>>>>> > > >>>>> pretty
> >>>>>>>> > > >>>>>>>>>>>>>>>>> much interchangeable. This is more of a
> >>>>>>>> trade-off
> >>>>>>>> > between
> >>>>>>>> > > >> the
> >>>>>>>> > > >>>>>>>>>>>>>> user
> >>>>>>>> > > >>>>>>>>>>>>>>>>> experience of metric producers and
> consumers.
> >>>>>>>> The
> >>>>>>>> > metric
> >>>>>>>> > > >>>>>>>>>>>>>> producers
> >>>>>>>> > > >>>>>>>>>>>>>>>>> want to use Counter or Gauge depending on
> >>>>>>>> whether the
> >>>>>>>> > > >> counter
> >>>>>>>> > > >>>>>>> is
> >>>>>>>> > > >>>>>>>>>>>>>>>>> already tracked in code, while ideally the
> >>>>>>>> metric
> >>>>>>>> > > consumers
> >>>>>>>> > > >>>>>>> only
> >>>>>>>> > > >>>>>>>>>>>>>>>>> want to see a single metric type for each
> >>>>>>>> metric. I am
> >>>>>>>> > > >>>>> leaning
> >>>>>>>> > > >>>>>>>>>>>>>>>>> towards to make the metric producers happy,
> >>>>>>>> i.e. allow
> >>>>>>>> > > >> Gauge
> >>>>>>>> > > >>>>> /
> >>>>>>>> > > >>>>>>>>>>>>>>>>> Counter metric type, and the the metric
> >>>>>>>> consumers
> >>>>>>>> > handle
> >>>>>>>> > > >> the
> >>>>>>>> > > >>>>>>>>> type
> >>>>>>>> > > >>>>>>>>>>>>>>>>> variation. The reason is that in practice,
> >>>>>>>> there might
> >>>>>>>> > be
> >>>>>>>> > > >>>>> more
> >>>>>>>> > > >>>>>>>>>>>>>>>>> connector implementations than metric
> reporter
> >>>>>>>> > > >>>>> implementations.
> >>>>>>>> > > >>>>>>>>>>>>>> We
> >>>>>>>> > > >>>>>>>>>>>>>>>>> could also provide some helper method to
> >>>>>>>> facilitate
> >>>>>>>> > > reading
> >>>>>>>> > > >>>>>>> from
> >>>>>>>> > > >>>>>>>>>>>>>>>>> such variable metric type.
> >>>>>>>> > > >>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>> Just some quick replies to the comments
> around
> >>>>>>>> > > >> implementation
> >>>>>>>> > > >>>>>>>>>>>>>>>> details.
> >>>>>>>> > > >>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>> 4) single place where metrics are
> >>>>>>>> registered except
> >>>>>>>> > > >>>>>>>>>>>>>>>>> connector-specific
> >>>>>>>> > > >>>>>>>>>>>>>>>>> ones (which we can't really avoid).
> >>>>>>>> > > >>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>> Register connector specific ones in a single
> >>>>>>>> place is
> >>>>>>>> > > >>>>> actually
> >>>>>>>> > > >>>>>>>>>>>>>>>>> something that I want to achieve.
> >>>>>>>> > > >>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>> 2) I'm talking about time-series databases
> >>>>>>>> like
> >>>>>>>> > > >>>>> Prometheus.
> >>>>>>>> > > >>>>>>>>>>>>>> We
> >>>>>>>> > > >>>>>>>>>>>>>>>>> would
> >>>>>>>> > > >>>>>>>>>>>>>>>>> only have a gauge metric exposing the last
> >>>>>>>> > > >>>>>>>>> fetchTime/emitTime
> >>>>>>>> > > >>>>>>>>>>>>>>>>> that is
> >>>>>>>> > > >>>>>>>>>>>>>>>>> regularly reported to the backend
> >>>>>>>> (Prometheus),
> >>>>>>>> > where a
> >>>>>>>> > > >>>>>>> user
> >>>>>>>> > > >>>>>>>>>>>>>>>>> could build
> >>>>>>>> > > >>>>>>>>>>>>>>>>> a histogram of his choosing when/if he
> >>>>>>>> wants it.
> >>>>>>>> > > >>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>> Not sure if such downsampling works. As an
> >>>>>>>> example, if
> >>>>>>>> > a
> >>>>>>>> > > >> user
> >>>>>>>> > > >>>>>>>>>>>>>>>>> complains that there are some intermittent
> >>>>>>>> latency
> >>>>>>>> > spikes
> >>>>>>>> > > >>>>>>> (maybe
> >>>>>>>> > > >>>>>>>>>>>>>> a
> >>>>>>>> > > >>>>>>>>>>>>>>>>> few records in 10 seconds) in their
> >>>>>>>> processing system.
> >>>>>>>> > > >>>>> Having a
> >>>>>>>> > > >>>>>>>>>>>>>>>>> Gauge sampling instantaneous latency seems
> >>>>>>>> unlikely
> >>>>>>>> > > useful.
> >>>>>>>> > > >>>>>>>>>>>>>>>>> However by looking at actual 99.9 percentile
> >>>>>>>> latency
> >>>>>>>> > > might
> >>>>>>>> > > >>>>>>> help.
> >>>>>>>> > > >>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>> Thanks,
> >>>>>>>> > > >>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>> Jiangjie (Becket) Qin
> >>>>>>>> > > >>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>> On Fri, Feb 22, 2019 at 9:30 PM Chesnay
> >>>>>>>> Schepler
> >>>>>>>> > > >>>>>>>>>>>>>>>>> <chesnay@apache.org <mailto:
> >>>>>>>> chesnay@apache.org>>
> >>>>>>>> > wrote:
> >>>>>>>> > > >>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>> Re: over complication of implementation.
> >>>>>>>> > > >>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>> I think I get understand better know what
> >>>>>>>> you're
> >>>>>>>> > > >> shooting
> >>>>>>>> > > >>>>>>>>>>>>>> for,
> >>>>>>>> > > >>>>>>>>>>>>>>>>> effectively something like the
> >>>>>>>> OperatorIOMetricGroup.
> >>>>>>>> > > >>>>>>>>>>>>>>>>> But still, re-define
> >>>>>>>> setupConnectorMetrics() to
> >>>>>>>> > accept
> >>>>>>>> > > a
> >>>>>>>> > > >>>>>>> set
> >>>>>>>> > > >>>>>>>>>>>>>>>>> of flags
> >>>>>>>> > > >>>>>>>>>>>>>>>>> for counters/meters(ans _possibly_
> >>>>>>>> histograms) along
> >>>>>>>> > > >>>>> with a
> >>>>>>>> > > >>>>>>>>>>>>>>>>> set of
> >>>>>>>> > > >>>>>>>>>>>>>>>>> well-defined Optional<Gauge<?>>, and
> return
> >>>>>>>> the
> >>>>>>>> > group.
> >>>>>>>> > > >>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>> Solves all issues as far as i can tell:
> >>>>>>>> > > >>>>>>>>>>>>>>>>> 1) no metrics must be created manually
> >>>>>>>> (except
> >>>>>>>> > Gauges,
> >>>>>>>> > > >>>>>>> which
> >>>>>>>> > > >>>>>>>>>>>>>>> are
> >>>>>>>> > > >>>>>>>>>>>>>>>>> effectively just Suppliers and you can't
> >>>>>>>> get around
> >>>>>>>> > > >>>>> this),
> >>>>>>>> > > >>>>>>>>>>>>>>>>> 2) additional metrics can be registered on
> >>>>>>>> the
> >>>>>>>> > returned
> >>>>>>>> > > >>>>>>>>>>>>>> group,
> >>>>>>>> > > >>>>>>>>>>>>>>>>> 3) see 1),
> >>>>>>>> > > >>>>>>>>>>>>>>>>> 4) single place where metrics are
> >>>>>>>> registered except
> >>>>>>>> > > >>>>>>>>>>>>>>>>> connector-specific
> >>>>>>>> > > >>>>>>>>>>>>>>>>> ones (which we can't really avoid).
> >>>>>>>> > > >>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>> Re: Histogram
> >>>>>>>> > > >>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>> 1) As an example, whether "numRecordsIn"
> is
> >>>>>>>> exposed
> >>>>>>>> > as
> >>>>>>>> > > a
> >>>>>>>> > > >>>>>>>>>>>>>>>>> Counter or a
> >>>>>>>> > > >>>>>>>>>>>>>>>>> Gauge should be irrelevant. So far we're
> >>>>>>>> using the
> >>>>>>>> > > >> metric
> >>>>>>>> > > >>>>>>>>>>>>>> type
> >>>>>>>> > > >>>>>>>>>>>>>>>>> that is
> >>>>>>>> > > >>>>>>>>>>>>>>>>> the most convenient at exposing a given
> >>>>>>>> value. If
> >>>>>>>> > there
> >>>>>>>> > > >>>>> is
> >>>>>>>> > > >>>>>>>>>>>>>>>>> some backing
> >>>>>>>> > > >>>>>>>>>>>>>>>>> data-structure that we want to expose some
> >>>>>>>> data from
> >>>>>>>> > we
> >>>>>>>> > > >>>>>>>>>>>>>>>>> typically opt
> >>>>>>>> > > >>>>>>>>>>>>>>>>> for a Gauge, as otherwise we're just
> >>>>>>>> mucking around
> >>>>>>>> > > with
> >>>>>>>> > > >>>>>>> the
> >>>>>>>> > > >>>>>>>>>>>>>>>>> Meter/Counter API to get it to match.
> >>>>>>>> Similarly, if
> >>>>>>>> > we
> >>>>>>>> > > >>>>> want
> >>>>>>>> > > >>>>>>>>>>>>>> to
> >>>>>>>> > > >>>>>>>>>>>>>>>>> count
> >>>>>>>> > > >>>>>>>>>>>>>>>>> something but no current count exists we
> >>>>>>>> typically
> >>>>>>>> > > added
> >>>>>>>> > > >>>>> a
> >>>>>>>> > > >>>>>>>>>>>>>>>>> Counter.
> >>>>>>>> > > >>>>>>>>>>>>>>>>> That's why attaching semantics to metric
> >>>>>>>> types makes
> >>>>>>>> > > >>>>> little
> >>>>>>>> > > >>>>>>>>>>>>>>>>> sense (but
> >>>>>>>> > > >>>>>>>>>>>>>>>>> unfortunately several reporters already do
> >>>>>>>> it); for
> >>>>>>>> > > >>>>>>>>>>>>>>>>> counters/meters
> >>>>>>>> > > >>>>>>>>>>>>>>>>> certainly, but the majority of metrics are
> >>>>>>>> gauges.
> >>>>>>>> > > >>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>> 2) I'm talking about time-series databases
> >>>>>>>> like
> >>>>>>>> > > >>>>> Prometheus.
> >>>>>>>> > > >>>>>>>>>>>>>> We
> >>>>>>>> > > >>>>>>>>>>>>>>>>> would
> >>>>>>>> > > >>>>>>>>>>>>>>>>> only have a gauge metric exposing the last
> >>>>>>>> > > >>>>>>>>> fetchTime/emitTime
> >>>>>>>> > > >>>>>>>>>>>>>>>>> that is
> >>>>>>>> > > >>>>>>>>>>>>>>>>> regularly reported to the backend
> >>>>>>>> (Prometheus),
> >>>>>>>> > where a
> >>>>>>>> > > >>>>>>> user
> >>>>>>>> > > >>>>>>>>>>>>>>>>> could build
> >>>>>>>> > > >>>>>>>>>>>>>>>>> a histogram of his choosing when/if he
> >>>>>>>> wants it.
> >>>>>>>> > > >>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>> On 22.02.2019 13:57, Becket Qin wrote:
> >>>>>>>> > > >>>>>>>>>>>>>>>>>> Hi Chesnay,
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>>> Thanks for the explanation.
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>>> ** Re: FLIP
> >>>>>>>> > > >>>>>>>>>>>>>>>>>> I might have misunderstood this, but it
> >>>>>>>> seems that
> >>>>>>>> > > "major
> >>>>>>>> > > >>>>>>>>>>>>>>>>> changes" are well
> >>>>>>>> > > >>>>>>>>>>>>>>>>>> defined in FLIP. The full contents is
> >>>>>>>> following:
> >>>>>>>> > > >>>>>>>>>>>>>>>>>> What is considered a "major change" that
> >>>>>>>> needs a FLIP?
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>>> Any of the following should be considered a
> >>>>>>>> major
> >>>>>>>> > > change:
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>>> - Any major new feature, subsystem, or
> piece
> >>>>>>>> of
> >>>>>>>> > > >>>>>>>>>>>>>>>>> functionality
> >>>>>>>> > > >>>>>>>>>>>>>>>>>> - *Any change that impacts the public
> >>>>>>>> interfaces of
> >>>>>>>> > the
> >>>>>>>> > > >>>>>>>>>>>>>>>>> project*
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>>> What are the "public interfaces" of the
> >>>>>>>> project?
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>>> *All of the following are public interfaces
> >>>>>>>> *that
> >>>>>>>> > people
> >>>>>>>> > > >>>>>>>>>>>>>>>>> build around:
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>>> - DataStream and DataSet API, including
> >>>>>>>> classes
> >>>>>>>> > related
> >>>>>>>> > > >>>>>>>>>>>>>>>>> to that, such as
> >>>>>>>> > > >>>>>>>>>>>>>>>>>> StreamExecutionEnvironment
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>>> - Classes marked with the @Public
> annotation
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>>> - On-disk binary formats, such as
> >>>>>>>> > > >>>>>>>>>>>>>> checkpoints/savepoints
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>>> - User-facing scripts/command-line tools,
> >>>>>>>> i.e.
> >>>>>>>> > > >>>>>>>>>>>>>>>>> bin/flink, Yarn scripts,
> >>>>>>>> > > >>>>>>>>>>>>>>>>>> Mesos scripts
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>>> - Configuration settings
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>>> - *Exposed monitoring information*
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>>> So any monitoring information change is
> >>>>>>>> considered as
> >>>>>>>> > > >>>>>>>>>>>>>> public
> >>>>>>>> > > >>>>>>>>>>>>>>>>> interface, and
> >>>>>>>> > > >>>>>>>>>>>>>>>>>> any public interface change is considered
> as
> >>>>>>>> a "major
> >>>>>>>> > > >>>>>>>>>>>>>>> change".
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>>> ** Re: over complication of implementation.
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>>> Although this is more of implementation
> >>>>>>>> details that
> >>>>>>>> > is
> >>>>>>>> > > >> not
> >>>>>>>> > > >>>>>>>>>>>>>>>>> covered by the
> >>>>>>>> > > >>>>>>>>>>>>>>>>>> FLIP. But it may be worth discussing.
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>>> First of all, I completely agree that we
> >>>>>>>> should use
> >>>>>>>> > the
> >>>>>>>> > > >>>>>>>>>>>>>>>>> simplest way to
> >>>>>>>> > > >>>>>>>>>>>>>>>>>> achieve our goal. To me the goal is the
> >>>>>>>> following:
> >>>>>>>> > > >>>>>>>>>>>>>>>>>> 1. Clear connector conventions and
> >>>>>>>> interfaces.
> >>>>>>>> > > >>>>>>>>>>>>>>>>>> 2. The easiness of creating a connector.
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>>> Both of them are important to the
> prosperity
> >>>>>>>> of the
> >>>>>>>> > > >>>>>>>>>>>>>>>>> connector ecosystem. So
> >>>>>>>> > > >>>>>>>>>>>>>>>>>> I'd rather abstract as much as possible on
> >>>>>>>> our side to
> >>>>>>>> > > >> make
> >>>>>>>> > > >>>>>>>>>>>>>>>>> the connector
> >>>>>>>> > > >>>>>>>>>>>>>>>>>> developer's work lighter. Given this goal,
> a
> >>>>>>>> static
> >>>>>>>> > util
> >>>>>>>> > > >>>>>>>>>>>>>>>>> method approach
> >>>>>>>> > > >>>>>>>>>>>>>>>>>> might have a few drawbacks:
> >>>>>>>> > > >>>>>>>>>>>>>>>>>> 1. Users still have to construct the
> metrics
> >>>>>>>> by
> >>>>>>>> > > >> themselves.
> >>>>>>>> > > >>>>>>>>>>>>>>>>> (And note that
> >>>>>>>> > > >>>>>>>>>>>>>>>>>> this might be erroneous by itself. For
> >>>>>>>> example, a
> >>>>>>>> > > customer
> >>>>>>>> > > >>>>>>>>>>>>>>>>> wrapper around
> >>>>>>>> > > >>>>>>>>>>>>>>>>>> dropwizard meter maybe used instead of
> >>>>>>>> MeterView).
> >>>>>>>> > > >>>>>>>>>>>>>>>>>> 2. When connector specific metrics are
> >>>>>>>> added, it is
> >>>>>>>> > > >>>>>>>>>>>>>>>>> difficult to enforce
> >>>>>>>> > > >>>>>>>>>>>>>>>>>> the scope to be the same as standard
> metrics.
> >>>>>>>> > > >>>>>>>>>>>>>>>>>> 3. It seems that a method proliferation is
> >>>>>>>> inevitable
> >>>>>>>> > if
> >>>>>>>> > > >> we
> >>>>>>>> > > >>>>>>>>>>>>>>>>> want to apply
> >>>>>>>> > > >>>>>>>>>>>>>>>>>> sanity checks. e.g. The metric of
> numBytesIn
> >>>>>>>> was not
> >>>>>>>> > > >>>>>>>>>>>>>>>>> registered for a meter.
> >>>>>>>> > > >>>>>>>>>>>>>>>>>> 4. Metrics are still defined in random
> >>>>>>>> places and hard
> >>>>>>>> > > to
> >>>>>>>> > > >>>>>>>>>>>>>>>> track.
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>>> The current PR I had was inspired by the
> >>>>>>>> Config system
> >>>>>>>> > > in
> >>>>>>>> > > >>>>>>>>>>>>>>>>> Kafka, which I
> >>>>>>>> > > >>>>>>>>>>>>>>>>>> found pretty handy. In fact it is not only
> >>>>>>>> used by
> >>>>>>>> > Kafka
> >>>>>>>> > > >>>>>>>>>>>>>>>>> itself but even
> >>>>>>>> > > >>>>>>>>>>>>>>>>>> some other projects that depend on Kafka. I
> >>>>>>>> am not
> >>>>>>>> > > saying
> >>>>>>>> > > >>>>>>>>>>>>>>>>> this approach is
> >>>>>>>> > > >>>>>>>>>>>>>>>>>> perfect. But I think it worths to save the
> >>>>>>>> work for
> >>>>>>>> > > >>>>>>>>>>>>>>>>> connector writers and
> >>>>>>>> > > >>>>>>>>>>>>>>>>>> encourage more systematic implementation.
> >>>>>>>> That being
> >>>>>>>> > > said,
> >>>>>>>> > > >>>>>>>>>>>>>> I
> >>>>>>>> > > >>>>>>>>>>>>>>>>> am fully open
> >>>>>>>> > > >>>>>>>>>>>>>>>>>> to suggestions.
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>>> Re: Histogram
> >>>>>>>> > > >>>>>>>>>>>>>>>>>> I think there are two orthogonal questions
> >>>>>>>> around
> >>>>>>>> > those
> >>>>>>>> > > >>>>>>>>>>>>>>>> metrics:
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>>> 1. Regardless of the metric type, by just
> >>>>>>>> looking at
> >>>>>>>> > the
> >>>>>>>> > > >>>>>>>>>>>>>>>>> meaning of a
> >>>>>>>> > > >>>>>>>>>>>>>>>>>> metric, is generic to all connectors? If
> the
> >>>>>>>> answer is
> >>>>>>>> > > >> yes,
> >>>>>>>> > > >>>>>>>>>>>>>>>>> we should
> >>>>>>>> > > >>>>>>>>>>>>>>>>>> include the metric into the convention. No
> >>>>>>>> matter
> >>>>>>>> > > whether
> >>>>>>>> > > >>>>>>>>>>>>>> we
> >>>>>>>> > > >>>>>>>>>>>>>>>>> include it
> >>>>>>>> > > >>>>>>>>>>>>>>>>>> into the convention or not, some connector
> >>>>>>>> > > implementations
> >>>>>>>> > > >>>>>>>>>>>>>>>>> will emit such
> >>>>>>>> > > >>>>>>>>>>>>>>>>>> metric. It is better to have a convention
> >>>>>>>> than letting
> >>>>>>>> > > >> each
> >>>>>>>> > > >>>>>>>>>>>>>>>>> connector do
> >>>>>>>> > > >>>>>>>>>>>>>>>>>> random things.
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>>> 2. If a standard metric is a histogram,
> what
> >>>>>>>> should we
> >>>>>>>> > > do?
> >>>>>>>> > > >>>>>>>>>>>>>>>>>> I agree that we should make it clear that
> >>>>>>>> using
> >>>>>>>> > > histograms
> >>>>>>>> > > >>>>>>>>>>>>>>>>> will have
> >>>>>>>> > > >>>>>>>>>>>>>>>>>> performance risk. But I do see histogram is
> >>>>>>>> useful in
> >>>>>>>> > > some
> >>>>>>>> > > >>>>>>>>>>>>>>>>> fine-granularity
> >>>>>>>> > > >>>>>>>>>>>>>>>>>> debugging where one do not have the luxury
> >>>>>>>> to stop the
> >>>>>>>> > > >>>>>>>>>>>>>>>>> system and inject
> >>>>>>>> > > >>>>>>>>>>>>>>>>>> more inspection code. So the workaround I
> am
> >>>>>>>> thinking
> >>>>>>>> > is
> >>>>>>>> > > >> to
> >>>>>>>> > > >>>>>>>>>>>>>>>>> provide some
> >>>>>>>> > > >>>>>>>>>>>>>>>>>> implementation suggestions. Assume later on
> >>>>>>>> we have a
> >>>>>>>> > > >>>>>>>>>>>>>>>>> mechanism of
> >>>>>>>> > > >>>>>>>>>>>>>>>>>> selective metrics. In the abstract metrics
> >>>>>>>> class we
> >>>>>>>> > can
> >>>>>>>> > > >>>>>>>>>>>>>>>>> disable those
> >>>>>>>> > > >>>>>>>>>>>>>>>>>> metrics by default individual connector
> >>>>>>>> writers does
> >>>>>>>> > not
> >>>>>>>> > > >>>>>>>>>>>>>>>>> have to do
> >>>>>>>> > > >>>>>>>>>>>>>>>>>> anything (this is another advantage of
> >>>>>>>> having an
> >>>>>>>> > > >>>>>>>>>>>>>>>>> AbstractMetrics instead of
> >>>>>>>> > > >>>>>>>>>>>>>>>>>> static util methods.)
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>>> I am not sure I fully understand the
> >>>>>>>> histogram in the
> >>>>>>>> > > >>>>>>>>>>>>>>>>> backend approach. Can
> >>>>>>>> > > >>>>>>>>>>>>>>>>>> you explain a bit more? Do you mean
> emitting
> >>>>>>>> the raw
> >>>>>>>> > > data,
> >>>>>>>> > > >>>>>>>>>>>>>>>>> e.g. fetchTime
> >>>>>>>> > > >>>>>>>>>>>>>>>>>> and emitTime with each record and let the
> >>>>>>>> histogram
> >>>>>>>> > > >>>>>>>>>>>>>>>>> computation happen in
> >>>>>>>> > > >>>>>>>>>>>>>>>>>> the background? Or let the processing
> thread
> >>>>>>>> putting
> >>>>>>>> > the
> >>>>>>>> > > >>>>>>>>>>>>>>>>> values into a
> >>>>>>>> > > >>>>>>>>>>>>>>>>>> queue and have a separate thread polling
> >>>>>>>> from the
> >>>>>>>> > queue
> >>>>>>>> > > >> and
> >>>>>>>> > > >>>>>>>>>>>>>>>>> add them into
> >>>>>>>> > > >>>>>>>>>>>>>>>>>> the histogram?
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>>> Thanks,
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>>> Jiangjie (Becket) Qin
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>>> On Fri, Feb 22, 2019 at 4:34 PM Chesnay
> >>>>>>>> Schepler
> >>>>>>>> > > >>>>>>>>>>>>>>>>> <chesnay@apache.org <mailto:
> >>>>>>>> chesnay@apache.org>>
> >>>>>>>> > > wrote:
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>> Re: Flip
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>> The very first line under both the main
> >>>>>>>> header and
> >>>>>>>> > > >> Purpose
> >>>>>>>> > > >>>>>>>>>>>>>>>>> section
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>> describe Flips as "major changes", which
> >>>>>>>> this isn't.
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>> Re: complication
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>> I'm not arguing against standardization,
> >>>>>>>> but again an
> >>>>>>>> > > >>>>>>>>>>>>>>>>> over-complicated
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>> implementation when a static utility
> method
> >>>>>>>> would be
> >>>>>>>> > > >>>>>>>>>>>>>>>>> sufficient.
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>> public static void setupConnectorMetrics(
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>> MetricGroup operatorMetricGroup,
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>> String connectorName,
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>> Optional<Gauge<Long>> numRecordsIn,
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>> ...)
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>> This gives you all you need:
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>> * a well-defined set of metrics for a
> >>>>>>>> connector to
> >>>>>>>> > > opt-in
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>> * standardized naming schemes for scope
> and
> >>>>>>>> > individual
> >>>>>>>> > > >>>>>>>>>>>>>>> metrics
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>> * standardize metric types (although
> >>>>>>>> personally I'm
> >>>>>>>> > not
> >>>>>>>> > > >>>>>>>>>>>>>>>>> interested in that
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>> since metric types should be considered
> >>>>>>>> syntactic
> >>>>>>>> > > sugar)
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>> Re: Configurable Histogram
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>> If anything they _must_ be turned off by
> >>>>>>>> default, but
> >>>>>>>> > > the
> >>>>>>>> > > >>>>>>>>>>>>>>>>> metric system is
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>> already exposing so many options that I'm
> >>>>>>>> not too
> >>>>>>>> > keen
> >>>>>>>> > > on
> >>>>>>>> > > >>>>>>>>>>>>>>>>> adding even more.
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>> You have also only addressed my first
> >>>>>>>> argument
> >>>>>>>> > against
> >>>>>>>> > > >>>>>>>>>>>>>>>>> histograms
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>> (performance), the second one still stands
> >>>>>>>> (calculate
> >>>>>>>> > > >>>>>>>>>>>>>>>>> histogram in metric
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>> backends instead).
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>> On 21.02.2019 16:27, Becket Qin wrote:
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>> Hi Chesnay,
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>> Thanks for the comments. I think this is
> >>>>>>>> worthy of a
> >>>>>>>> > > >> FLIP
> >>>>>>>> > > >>>>>>>>>>>>>>>>> because it is
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>> public API. According to the FLIP
> >>>>>>>> description a FlIP
> >>>>>>>> > > is
> >>>>>>>> > > >>>>>>>>>>>>>>>>> required in case
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>> of:
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>> - Any change that impacts the public
> >>>>>>>> interfaces of
> >>>>>>>> > > >>>>>>>>>>>>>>>>> the project
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>> and the following entry is found in the
> >>>>>>>> definition
> >>>>>>>> > of
> >>>>>>>> > > >>>>>>>>>>>>>>>>> "public interface".
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>> - Exposed monitoring information
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>> Metrics are critical to any production
> >>>>>>>> system. So a
> >>>>>>>> > > >> clear
> >>>>>>>> > > >>>>>>>>>>>>>>>>> metric
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>> definition
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>> is important for any serious users. For
> an
> >>>>>>>> > > organization
> >>>>>>>> > > >>>>>>>>>>>>>>>>> with large Flink
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>> installation, change in metrics means
> >>>>>>>> great amount
> >>>>>>>> > of
> >>>>>>>> > > >>>>>>>>>>>>>>>>> work. So such
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>> changes
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>> do need to be fully discussed and
> >>>>>>>> documented.
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>> ** Re: Histogram.
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>> We can discuss whether there is a better
> >>>>>>>> way to
> >>>>>>>> > expose
> >>>>>>>> > > >>>>>>>>>>>>>>>>> metrics that are
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>> suitable for histograms. My
> >>>>>>>> micro-benchmark on
> >>>>>>>> > various
> >>>>>>>> > > >>>>>>>>>>>>>>>>> histogram
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>> implementations also indicates that they
> >>>>>>>> are
> >>>>>>>> > > >>>>>>>>>>>>>> significantly
> >>>>>>>> > > >>>>>>>>>>>>>>>>> slower than
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>> other metric types. But I don't think
> that
> >>>>>>>> means
> >>>>>>>> > never
> >>>>>>>> > > >>>>>>>>>>>>>> use
> >>>>>>>> > > >>>>>>>>>>>>>>>>> histogram, but
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>> means use it with caution. For example,
> we
> >>>>>>>> can
> >>>>>>>> > suggest
> >>>>>>>> > > >>>>>>>>>>>>>> the
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>> implementations
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>> to turn them off by default and only turn
> >>>>>>>> it on for
> >>>>>>>> > a
> >>>>>>>> > > >>>>>>>>>>>>>>>>> small amount of
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>> time
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>> when performing some micro-debugging.
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>> ** Re: complication:
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>> Connector conventions are essential for
> >>>>>>>> Flink
> >>>>>>>> > > ecosystem.
> >>>>>>>> > > >>>>>>>>>>>>>>>>> Flink connectors
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>> pool is probably the most important part
> >>>>>>>> of Flink,
> >>>>>>>> > > just
> >>>>>>>> > > >>>>>>>>>>>>>>>>> like any other
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>> data
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>> system. Clear conventions of connectors
> >>>>>>>> will help
> >>>>>>>> > > build
> >>>>>>>> > > >>>>>>>>>>>>>>>>> Flink ecosystem
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>> in
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>> a more organic way.
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>> Take the metrics convention as an
> example,
> >>>>>>>> imagine
> >>>>>>>> > > >>>>>>>>>>>>>> someone
> >>>>>>>> > > >>>>>>>>>>>>>>>>> has developed
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>> a
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>> Flink connector for System foo, and
> another
> >>>>>>>> > developer
> >>>>>>>> > > >> may
> >>>>>>>> > > >>>>>>>>>>>>>>>>> have developed
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>> a
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>> monitoring and diagnostic framework for
> >>>>>>>> Flink which
> >>>>>>>> > > >>>>>>>>>>>>>>>>> analyzes the Flink
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>> job
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>> performance based on metrics. With a
> clear
> >>>>>>>> metric
> >>>>>>>> > > >>>>>>>>>>>>>>>>> convention, those two
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>> projects could be developed
> independently.
> >>>>>>>> Once
> >>>>>>>> > users
> >>>>>>>> > > >> put
> >>>>>>>> > > >>>>>>>>>>>>>>>>> them together,
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>> it would work without additional
> >>>>>>>> modifications. This
> >>>>>>>> > > >>>>>>>>>>>>>>>>> cannot be easily
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>> achieved by just defining a few
> constants.
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>> ** Re: selective metrics:
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>> Sure, we can discuss that in a separate
> >>>>>>>> thread.
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>> @Dawid
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>> ** Re: latency / fetchedLatency
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>> The primary purpose of establish such a
> >>>>>>>> convention
> >>>>>>>> > is
> >>>>>>>> > > to
> >>>>>>>> > > >>>>>>>>>>>>>>>>> help developers
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>> write connectors in a more compatible
> way.
> >>>>>>>> The
> >>>>>>>> > > >> convention
> >>>>>>>> > > >>>>>>>>>>>>>>>>> is supposed to
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>> be
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>> defined more proactively. So when look at
> >>>>>>>> the
> >>>>>>>> > > >> convention,
> >>>>>>>> > > >>>>>>>>>>>>>>>>> it seems more
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>> important to see if the concept is
> >>>>>>>> applicable to
> >>>>>>>> > > >>>>>>>>>>>>>>>>> connectors in general.
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>> It
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>> might be true so far only Kafka connector
> >>>>>>>> reports
> >>>>>>>> > > >>>>>>>>>>>>>> latency.
> >>>>>>>> > > >>>>>>>>>>>>>>>>> But there
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>> might
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>> be hundreds of other connector
> >>>>>>>> implementations in
> >>>>>>>> > the
> >>>>>>>> > > >>>>>>>>>>>>>>>>> Flink ecosystem,
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>> though not in the Flink repo, and some of
> >>>>>>>> them also
> >>>>>>>> > > >> emits
> >>>>>>>> > > >>>>>>>>>>>>>>>>> latency. I
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>> think
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>> a lot of other sources actually also has
> >>>>>>>> an append
> >>>>>>>> > > >>>>>>>>>>>>>>>>> timestamp. e.g.
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>> database
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>> bin logs and some K-V stores. So I
> >>>>>>>> wouldn't be
> >>>>>>>> > > surprised
> >>>>>>>> > > >>>>>>>>>>>>>>>>> if some database
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>> connector can also emit latency metrics.
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>> Thanks,
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>> Jiangjie (Becket) Qin
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>> On Thu, Feb 21, 2019 at 10:14 PM Chesnay
> >>>>>>>> Schepler
> >>>>>>>> > > >>>>>>>>>>>>>>>>> <chesnay@apache.org <mailto:
> >>>>>>>> chesnay@apache.org>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>> wrote:
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>> Regarding 2) It doesn't make sense to
> >>>>>>>> investigate
> >>>>>>>> > > this
> >>>>>>>> > > >>>>>>>>>>>>>> as
> >>>>>>>> > > >>>>>>>>>>>>>>>>> part of this
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>> FLIP. This is something that could be of
> >>>>>>>> interest
> >>>>>>>> > for
> >>>>>>>> > > >>>>>>>>>>>>>> the
> >>>>>>>> > > >>>>>>>>>>>>>>>>> entire metric
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>> system, and should be designed for as
> >>>>>>>> such.
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>> Regarding the proposal as a whole:
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>> Histogram metrics shall not be added to
> >>>>>>>> the core of
> >>>>>>>> > > >>>>>>>>>>>>>>>>> Flink. They are
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>> significantly more expensive than other
> >>>>>>>> metrics,
> >>>>>>>> > and
> >>>>>>>> > > >>>>>>>>>>>>>>>>> calculating
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>> histograms in the application is
> regarded
> >>>>>>>> as an
> >>>>>>>> > > >>>>>>>>>>>>>>>>> anti-pattern by several
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>> metric backends, who instead recommend
> to
> >>>>>>>> expose
> >>>>>>>> > the
> >>>>>>>> > > >> raw
> >>>>>>>> > > >>>>>>>>>>>>>>>>> data and
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>> calculate the histogram in the backend.
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>> Second, this seems overly complicated.
> >>>>>>>> Given that
> >>>>>>>> > we
> >>>>>>>> > > >>>>>>>>>>>>>>>>> already established
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>> that not all connectors will export all
> >>>>>>>> metrics we
> >>>>>>>> > > are
> >>>>>>>> > > >>>>>>>>>>>>>>>>> effectively
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>> reducing this down to a consistent
> naming
> >>>>>>>> scheme.
> >>>>>>>> > We
> >>>>>>>> > > >>>>>>>>>>>>>>>>> don't need anything
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>> sophisticated for that; basically just a
> >>>>>>>> few
> >>>>>>>> > > constants
> >>>>>>>> > > >>>>>>>>>>>>>>>>> that all
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>> connectors use.
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>> I'm not convinced that this is worthy of
> >>>>>>>> a FLIP.
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>> On 21.02.2019 14:26, Dawid Wysakowicz
> >>>>>>>> wrote:
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>> Hi,
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>> Ad 1. In general I undestand and I
> >>>>>>>> agree. But
> >>>>>>>> > those
> >>>>>>>> > > >>>>>>>>>>>>>>>>> particular metrics
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>> (latency, fetchLatency), right now
> would
> >>>>>>>> only be
> >>>>>>>> > > >>>>>>>>>>>>>>>>> reported if user uses
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>> KafkaConsumer with internal
> >>>>>>>> timestampAssigner with
> >>>>>>>> > > >>>>>>>>>>>>>>>>> StreamCharacteristic
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>> set to EventTime, right? That sounds
> >>>>>>>> like a very
> >>>>>>>> > > >>>>>>>>>>>>>>>>> specific case. I am
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>> not
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>> sure if we should introduce a generic
> >>>>>>>> metric that
> >>>>>>>> > > will
> >>>>>>>> > > >>>>>>>>>>>>>> be
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>> disabled/absent for most of
> >>>>>>>> implementations.
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>> Ad.2 That sounds like an orthogonal
> >>>>>>>> issue, that
> >>>>>>>> > > might
> >>>>>>>> > > >>>>>>>>>>>>>>>>> make sense to
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>> investigate in the future.
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>> Best,
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>> Dawid
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>> On 21/02/2019 13:20, Becket Qin wrote:
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>> Hi Dawid,
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>> Thanks for the feedback. That makes
> >>>>>>>> sense to me.
> >>>>>>>> > > >> There
> >>>>>>>> > > >>>>>>>>>>>>>>>>> are two cases
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>> to
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>> be
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>> addressed.
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>> 1. The metrics are supposed to be a
> >>>>>>>> guidance. It
> >>>>>>>> > is
> >>>>>>>> > > >>>>>>>>>>>>>>>>> likely that a
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>> connector
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>> only supports some but not all of the
> >>>>>>>> metrics. In
> >>>>>>>> > > >> that
> >>>>>>>> > > >>>>>>>>>>>>>>>>> case, each
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>> connector
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>> implementation should have the freedom
> >>>>>>>> to decide
> >>>>>>>> > > >> which
> >>>>>>>> > > >>>>>>>>>>>>>>>>> metrics are
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>> reported. For the metrics that are
> >>>>>>>> supported, the
> >>>>>>>> > > >>>>>>>>>>>>>>>>> guidance should be
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>> followed.
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>> 2. Sometimes users may want to disable
> >>>>>>>> certain
> >>>>>>>> > > >> metrics
> >>>>>>>> > > >>>>>>>>>>>>>>>>> for some reason
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>> (e.g. performance / reprocessing of
> >>>>>>>> data). A
> >>>>>>>> > > generic
> >>>>>>>> > > >>>>>>>>>>>>>>>>> mechanism should
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>> be
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>> provided to allow user choose which
> >>>>>>>> metrics are
> >>>>>>>> > > >>>>>>>>>>>>>>>>> reported. This
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>> mechanism
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>> should also be honored by the
> connector
> >>>>>>>> > > >>>>>>>>>>>>>> implementations.
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>> Does this sound reasonable to you?
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>> Thanks,
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>> Jiangjie (Becket) Qin
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>> On Thu, Feb 21, 2019 at 4:22 PM Dawid
> >>>>>>>> Wysakowicz
> >>>>>>>> > <
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>> dwysakowicz@apache.org <mailto:
> >>>>>>>> > > dwysakowicz@apache.org
> >>>>>>>> > > >>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>> wrote:
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> Hi,
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> Generally I like the idea of having a
> >>>>>>>> unified,
> >>>>>>>> > > >>>>>>>>>>>>>>>>> standard set of
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>> metrics
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>> for
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> all connectors. I have some slight
> >>>>>>>> concerns
> >>>>>>>> > about
> >>>>>>>> > > >>>>>>>>>>>>>>>>> fetchLatency and
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> latency though. They are computed
> >>>>>>>> based on
> >>>>>>>> > > EventTime
> >>>>>>>> > > >>>>>>>>>>>>>>>>> which is not a
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>> purely
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> technical feature. It depends often
> on
> >>>>>>>> some
> >>>>>>>> > > business
> >>>>>>>> > > >>>>>>>>>>>>>>>>> logic, might be
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>> absent
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> or defined after source. Those
> metrics
> >>>>>>>> could
> >>>>>>>> > also
> >>>>>>>> > > >>>>>>>>>>>>>>>>> behave in a weird
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>> way in
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> case of replaying backlog. Therefore
> I
> >>>>>>>> am not
> >>>>>>>> > sure
> >>>>>>>> > > >> if
> >>>>>>>> > > >>>>>>>>>>>>>>>>> we should
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>> include
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> those metrics by default. Maybe we
> >>>>>>>> could at
> >>>>>>>> > least
> >>>>>>>> > > >>>>>>>>>>>>>>>>> introduce a feature
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> switch for them? What do you think?
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> Best,
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> Dawid
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> On 21/02/2019 03:13, Becket Qin
> wrote:
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> Bump. If there is no objections to
> the
> >>>>>>>> proposed
> >>>>>>>> > > >>>>>>>>>>>>>>>>> metrics. I'll start a
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> voting thread later toady.
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> Thanks,
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> Jiangjie (Becket) Qin
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> On Mon, Feb 11, 2019 at 8:17 PM
> Becket
> >>>>>>>> Qin
> >>>>>>>> > > >>>>>>>>>>>>>>>>> <becket.qin@gmail.com <mailto:
> >>>>>>>> becket.qin@gmail.com>>
> >>>>>>>> > <
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>> becket.qin@gmail.com <mailto:
> >>>>>>>> becket.qin@gmail.com
> >>>>>>>> > >>
> >>>>>>>> > > >>>>>>>>>>>>>>> wrote:
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> Hi folks,
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> I would like to start the FLIP
> >>>>>>>> discussion thread
> >>>>>>>> > > >>>>>>>>>>>>>> about
> >>>>>>>> > > >>>>>>>>>>>>>>>>> standardize
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>> the
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> connector metrics.
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> In short, we would like to provide a
> >>>>>>>> convention
> >>>>>>>> > of
> >>>>>>>> > > >>>>>>>>>>>>>>>>> Flink connector
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> metrics. It will help simplify the
> >>>>>>>> monitoring
> >>>>>>>> > and
> >>>>>>>> > > >>>>>>>>>>>>>>>>> alerting on Flink
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>> jobs.
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> The FLIP link is following:
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>
> >>>>>>>> > > >>>>>>>
> >>>>>>>> > > >>>>>
> >>>>>>>> > > >>
> >>>>>>>> > >
> >>>>>>>> >
> >>>>>>>>
> https://cwiki.apache.org/confluence/display/FLINK/FLIP-33%3A+Standardize+Connector+Metrics
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> Thanks,
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> Jiangjie (Becket) Qin
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>>>>
> >>>>>>>> > > >>>>>>>>>
> >>>>>>>> > > >>>>>>>>>
> >>>>>>>> > > >>>>>>>>>
> >>>>>>>> > > >>>>>>>
> >>>>>>>> > > >>>>>>>
> >>>>>>>> > > >>>>>>>
> >>>>>>>> > > >>>>>
> >>>>>>>> > > >>>>>
> >>>>>>>> > > >>
> >>>>>>>> > > >>
> >>>>>>>> > >
> >>>>>>>> > >
> >>>>>>>> >
> >>>>>>>>
> >>>>>>>>
> >>>>>>>> --
> >>>>>>>>
> >>>>>>>> Konstantin Knauf
> >>>>>>>>
> >>>>>>>> https://twitter.com/snntrable
> >>>>>>>>
> >>>>>>>> https://github.com/knaufk
> >>>>>>>>
> >>>>>>>
>
--
Konstantin Knauf
https://twitter.com/snntrable
https://github.com/knaufk
Re: [DISCUSS] FLIP-33: Standardize connector metrics
Posted by Stephan Ewen <st...@ververica.com>.
Having the watermark lag metric was the important part from my side.
So +1 to go ahead.
On Fri, Sep 18, 2020 at 4:11 PM Becket Qin <be...@gmail.com> wrote:
> Hey Stephan,
>
> Thanks for the quick reply. I actually forgot to mention that I also added
> a "watermarkLag" metric to the Source metrics in addition to the
> "currentFetchEventTimeLag" and "currentEmitEventTimeLag".
> So in the current proposal, both XXEventTimeLag will be based on event
> timestamps, while the watermarkLag is based on watermark. And all the lags
> are defined against the wall clock time. Does this cover what you are
> proposing?
>
> Thanks,
>
> Jiangjie (Becket) Qin
>
> On Fri, Sep 18, 2020 at 6:08 PM Stephan Ewen <st...@ververica.com>
> wrote:
>
>> Hi Becket!
>>
>> I am wondering if it makes sense to do the following small change:
>>
>> - Have "currentFetchEventTimeLag" be defined on event timestamps
>> (optionally, if the source system exposes it) <== this is like in your
>> proposal
>> this helps understand how long the records were in the source before
>>
>> - BUT change "currentEmitEventTimeLag" to be
>> "currentSourceWatermarkLag" instead.
>> That way, users can see how far behind the wall-clock-time the source
>> progress is all in all.
>> It is also a more well defined metric as it does not oscillate with
>> out-of-order events.
>>
>> What do you think?
>>
>> Best,
>> Stephan
>>
>>
>>
>> On Fri, Sep 18, 2020 at 12:02 PM Becket Qin <be...@gmail.com> wrote:
>>
>>> Hi folks,
>>>
>>> Thanks for all the great feedback. I have just updated FLIP-33 wiki with
>>> the following changes:
>>>
>>> 1. Renaming. "currentFetchLatency" to "currentFetchEventTimeLag",
>>> "currentLatency" to "currentEmitEventTimeLag".
>>> 2. Added the public interface code change required for the new metrics.
>>> 3. Added description of whether a metric is predefined or optional, and
>>> which component is expected to update the metric.
>>>
>>> Please let me know if you have any questions. I'll start a vote in two
>>> days if there are no further concerns.
>>>
>>> Thanks,
>>>
>>> Jiangjie (Becket) Qin
>>>
>>> On Wed, Sep 9, 2020 at 9:56 AM Becket Qin <be...@gmail.com> wrote:
>>>
>>>> Hi Stephan,
>>>>
>>>> Thanks for the input. Just a few more clarifications / questions.
>>>>
>>>> *Num Bytes / Records Metrics*
>>>>
>>>> 1. At this point, the *numRecordsIn(Rate)* metrics exist in both
>>>> OperatorIOMetricGroup and TaskIOMetricGroup. I did not find
>>>> *numRecordsIn(Rate)* in the TaskIOMetricGroup updated anywhere other
>>>> than in the unit tests. Am I missing something?
>>>>
>>>> 2. *numBytesIn(Rate)* metrics only exist in TaskIOMetricGroup. At this
>>>> point, the SourceReaders only has access to a SourceReaderContext which
>>>> provides an OperatorMetricGroup. So it seems that the connector developers
>>>> are not able to update the *numBytesIn(Rate). *With the multiple
>>>> Source chaining support, it is possible that there are multiple Sources are
>>>> in the same task. So it looks that we need to add *numBytesIn(Rate)*
>>>> to the operator metrics as well.
>>>>
>>>>
>>>> *Current (Fetch) Latency*
>>>>
>>>> *currentFetchLatency* helps clearly tell whether the latency is caused
>>>> by Flink or not. Backpressure is not the only reason that we see fetch
>>>> latency. Even if there is no back pressure, the records may have passed a
>>>> long pipeline before they entered Flink. For example, say the *currentLatency
>>>> *is 10 seconds and there is no backpressure. Does that mean the record
>>>> spent 10 seconds in the Source operator? If not, how much did Flink
>>>> contribute to that 10 seconds of latency? These questions are frequently
>>>> asked and hard to tell without the fetch latency.
>>>>
>>>> For "currentFetchLatency", we would need to understand timestamps
>>>>> before the records are decoded. That is only possible for some sources,
>>>>> where the client gives us the records in a (partially) decoded from already
>>>>> (like Kafka). Then, some work has been done between the fetch time and the
>>>>> time we update the metric already, so it is already a bit closer to the
>>>>> "currentFetchLatency". I think following this train of thought, there is
>>>>> diminished benefit from that specific metric.
>>>>
>>>>
>>>> We may not have to report the fetch latency before records are decoded.
>>>> One solution is to remember the* FetchTime* when the encoded records
>>>> are fetched, and report the fetch latency after the records are decoded by
>>>> computing (*FetchTime - EventTime*). An approximate implementation
>>>> would be adding a *FetchTime *field to the *RecordsWithSplitIds* assuming
>>>> that all the records in that data structure are fetched at the same time.
>>>>
>>>> Thoughts?
>>>>
>>>> Thanks,
>>>>
>>>> Jiangjie (Becket) Qin
>>>>
>>>> On Wed, Sep 9, 2020 at 12:42 AM Stephan Ewen <st...@ververica.com>
>>>> wrote:
>>>>
>>>>> Thanks for reviving this, Becket!
>>>>>
>>>>> I think Konstantin's comments are great. I'd add these points:
>>>>>
>>>>> *Num Bytes / Records Metrics*
>>>>>
>>>>> For "numBytesIn" and "numRecordsIn", we should reuse the
>>>>> OperatorIOMetric group, then it also gets reported to the overview page in
>>>>> the Web UI.
>>>>>
>>>>> The "numBytesInPerSecond" and "numRecordsInPerSecond" are
>>>>> automatically derived metrics, no need to do anything once we populate the
>>>>> above two metrics
>>>>>
>>>>>
>>>>> *Current (Fetch) Latency*
>>>>>
>>>>> I would really go for "eventTimeLag" rather than "fetchLatency". I
>>>>> think "eventTimeLag" is a term that has some adoption in the Flink
>>>>> community and beyond.
>>>>>
>>>>> I am not so sure that I see the benefit between "currentLatency" and
>>>>> "currentFetchLatency", (or event time lag before/after) as this only is
>>>>> different by the time it takes to emit a batch.
>>>>> - In a non-backpressured case, these should be virtually
>>>>> identical (and both dominated by watermark lag, not the actual time it
>>>>> takes the fetch to be emitted)
>>>>> - In a backpressured case, why do you care about when data was
>>>>> fetched, as opposed to emitted? Emitted time is relevant for application
>>>>> semantics and checkpoints. Fetch time seems to be an implementation detail
>>>>> (how much does the source buffer).
>>>>>
>>>>> The "currentLatency" (eventTimeLagAfter) can be computed
>>>>> out-of-the-box, independent of a source implementation, so that is also a
>>>>> good argument to make it the main metric.
>>>>> We know timestamps and watermarks in the source. Except for cases
>>>>> where no watermarks have been defined at all (batch jobs or pure processing
>>>>> time jobs), in which case this metric should probably be "Infinite".
>>>>>
>>>>> For "currentFetchLatency", we would need to understand timestamps
>>>>> before the records are decoded. That is only possible for some sources,
>>>>> where the client gives us the records in a (partially) decoded from already
>>>>> (like Kafka). Then, some work has been done between the fetch time and the
>>>>> time we update the metric already, so it is already a bit closer to the
>>>>> "currentFetchLatency". I think following this train of thought, there is
>>>>> diminished benefit from that specific metric.
>>>>>
>>>>>
>>>>> *Idle Time*
>>>>>
>>>>> I agree, it would be great to rename this. Maybe to "sourceWaitTime"
>>>>> or "sourceIdleTime" so to make clear that this is not exactly the time that
>>>>> Flink's processing pipeline is idle, but the time where the source does not
>>>>> have new data.
>>>>>
>>>>> This is not an easy metric to collect, though (except maybe for the
>>>>> sources that are only idle while they have no split assigned, like
>>>>> continuous file source).
>>>>>
>>>>> *Source Specific Metrics*
>>>>>
>>>>> I believe source-specific would only be "sourceIdleTime",
>>>>> "numRecordsInErrors", "pendingBytes", and "pendingRecords".
>>>>>
>>>>>
>>>>> *Conclusion*
>>>>>
>>>>> We can probably add "numBytesIn" and "numRecordsIn" and "eventTimeLag"
>>>>> right away, with little complexity.
>>>>> I'd suggest to start with these right away.
>>>>>
>>>>> Best,
>>>>> Stephan
>>>>>
>>>>>
>>>>> On Tue, Sep 8, 2020 at 3:25 PM Becket Qin <be...@gmail.com>
>>>>> wrote:
>>>>>
>>>>>> Hey Konstantin,
>>>>>>
>>>>>> Thanks for the feedback and suggestions. Please see the reply below.
>>>>>>
>>>>>> * idleTime: In the meantime, a similar metric "idleTimeMsPerSecond"
>>>>>>> has
>>>>>>> been introduced in https://issues.apache.org/jira/browse/FLINK-16864.
>>>>>>> They
>>>>>>> have a similar name, but different definitions of idleness,
>>>>>>> e.g. "idleTimeMsPerSecond" considers the SourceTask idle, when it is
>>>>>>> backpressured. Can we make it clearer that these two metrics mean
>>>>>>> different
>>>>>>> things?
>>>>>>
>>>>>>
>>>>>> That is a good point. I did not notice this metric earlier. It seems
>>>>>> that both metrics are useful to the users. One tells them how busy the
>>>>>> source is and how much more throughput the source can handle. The other
>>>>>> tells the users how long since the source has seen the last record, which
>>>>>> is useful for debugging. I'll update the FLIP to make it clear.
>>>>>>
>>>>>> * "current(Fetch)Latency" I am wondering if
>>>>>>> "eventTimeLag(Before|After)"
>>>>>>> is more descriptive/clear. What do others think?
>>>>>>
>>>>>>
>>>>>> I am quite open to the ideas on these names. In fact I also feel
>>>>>> "current(Fetch)Latency" are not super intuitive. So it would be great if we
>>>>>> can have better names.
>>>>>>
>>>>>> * Current(Fetch)Latency implies that the timestamps are directly
>>>>>>> extracted in the source connector, right? Will this be the default
>>>>>>> for
>>>>>>> FLIP-27 sources anyway?
>>>>>>
>>>>>>
>>>>>> The "currentFetchLatency" will probably be reported by each source
>>>>>> implementation, because the data fetching is done by SplitReaders and there
>>>>>> is no base implementation. The "currentLatency", on the other hand, can be
>>>>>> reported by the SourceReader base implementation. However, since developers
>>>>>> can actually implement their own source connector without using our base
>>>>>> implementation, these metric guidance are still useful for the connector
>>>>>> developers in that case.
>>>>>>
>>>>>> * Does FLIP-33 also include the implementation of these metrics (to
>>>>>>> the
>>>>>>> extent possible) for all connectors currently available in Apache
>>>>>>> Flink or
>>>>>>> is the "per-connector implementation" out-of-scope?
>>>>>>
>>>>>>
>>>>>> FLIP-33 itself does not specify any implementation of those metrics.
>>>>>> But the connectors we provide in Apache Flink will follow the guidance of
>>>>>> FLIP-33 to emit those metrics when applicable. Maybe We can have some
>>>>>> public static Strings defined for the metric names to help other connector
>>>>>> developers follow the same guidance. I can also add that to the public
>>>>>> interface section of the FLIP if we decide to do that.
>>>>>>
>>>>>> Thanks,
>>>>>>
>>>>>> Jiangjie (Becket) Qin
>>>>>>
>>>>>> On Tue, Sep 8, 2020 at 9:02 PM Becket Qin <be...@gmail.com>
>>>>>> wrote:
>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> On Tue, Sep 8, 2020 at 6:55 PM Konstantin Knauf <kn...@apache.org>
>>>>>>> wrote:
>>>>>>>
>>>>>>>> Hi Becket,
>>>>>>>>
>>>>>>>> Thank you for picking up this FLIP. I have a few questions:
>>>>>>>>
>>>>>>>> * two thoughts on naming:
>>>>>>>> * idleTime: In the meantime, a similar metric
>>>>>>>> "idleTimeMsPerSecond" has
>>>>>>>> been introduced in
>>>>>>>> https://issues.apache.org/jira/browse/FLINK-16864. They
>>>>>>>> have a similar name, but different definitions of idleness,
>>>>>>>> e.g. "idleTimeMsPerSecond" considers the SourceTask idle, when it is
>>>>>>>> backpressured. Can we make it clearer that these two metrics mean
>>>>>>>> different
>>>>>>>> things?
>>>>>>>>
>>>>>>>> * "current(Fetch)Latency" I am wondering if
>>>>>>>> "eventTimeLag(Before|After)"
>>>>>>>> is more descriptive/clear. What do others think?
>>>>>>>>
>>>>>>>> * Current(Fetch)Latency implies that the timestamps are directly
>>>>>>>> extracted in the source connector, right? Will this be the default
>>>>>>>> for
>>>>>>>> FLIP-27 sources anyway?
>>>>>>>>
>>>>>>>> * Does FLIP-33 also include the implementation of these metrics (to
>>>>>>>> the
>>>>>>>> extent possible) for all connectors currently available in Apache
>>>>>>>> Flink or
>>>>>>>> is the "per-connector implementation" out-of-scope?
>>>>>>>>
>>>>>>>> Thanks,
>>>>>>>>
>>>>>>>> Konstantin
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>> On Fri, Sep 4, 2020 at 4:56 PM Becket Qin <be...@gmail.com>
>>>>>>>> wrote:
>>>>>>>>
>>>>>>>> > Hi all,
>>>>>>>> >
>>>>>>>> > To complete the Source refactoring work, I'd like to revive this
>>>>>>>> > discussion. Since the mail thread has been dormant for more than
>>>>>>>> a year,
>>>>>>>> > just to recap the motivation of the FLIP:
>>>>>>>> >
>>>>>>>> > 1. The FLIP proposes to standardize the connector metrics by
>>>>>>>> giving
>>>>>>>> > guidance on the metric specifications, including the name, type
>>>>>>>> and meaning
>>>>>>>> > of the metrics.
>>>>>>>> > 2. It is OK for a connector to not emit some of the metrics in
>>>>>>>> the metric
>>>>>>>> > guidance, but if a metric of the same semantic is emitted, the
>>>>>>>> > implementation should follow the guidance.
>>>>>>>> > 3. It is OK for a connector to emit more metrics than what are
>>>>>>>> listed in
>>>>>>>> > the FLIP. This includes having an alias for a metric specified in
>>>>>>>> the FLIP.
>>>>>>>> > 4. We will implement some of the metrics out of the box in the
>>>>>>>> default
>>>>>>>> > implementation of FLIP-27, as long as it is applicable.
>>>>>>>> >
>>>>>>>> > The FLIP wiki is following:
>>>>>>>> > https://cwiki.apache.org/confluence/display/FLINK/FLIP-33
>>>>>>>> > %3A+Standardize+Connector+Metrics
>>>>>>>> >
>>>>>>>> > Any thoughts?
>>>>>>>> >
>>>>>>>> > Thanks,
>>>>>>>> >
>>>>>>>> > Jiangjie (Becket) Qin
>>>>>>>> >
>>>>>>>> >
>>>>>>>> > On Fri, Jun 14, 2019 at 2:29 PM Piotr Nowojski <
>>>>>>>> piotr@ververica.com>
>>>>>>>> > wrote:
>>>>>>>> >
>>>>>>>> > > > we will need to revisit the convention list and adjust them
>>>>>>>> accordingly
>>>>>>>> > > when FLIP-27 is ready
>>>>>>>> > >
>>>>>>>> > >
>>>>>>>> > > Yes, this sounds good :)
>>>>>>>> > >
>>>>>>>> > > Piotrek
>>>>>>>> > >
>>>>>>>> > > > On 13 Jun 2019, at 13:35, Becket Qin <be...@gmail.com>
>>>>>>>> wrote:
>>>>>>>> > > >
>>>>>>>> > > > Hi Piotr,
>>>>>>>> > > >
>>>>>>>> > > > That's great to know. Chances are that we will need to
>>>>>>>> revisit the
>>>>>>>> > > > convention list and adjust them accordingly when FLIP-27 is
>>>>>>>> ready, At
>>>>>>>> > > that
>>>>>>>> > > > point we can mark some of the metrics as available by default
>>>>>>>> for
>>>>>>>> > > > connectors implementing the new interface.
>>>>>>>> > > >
>>>>>>>> > > > Thanks,
>>>>>>>> > > >
>>>>>>>> > > > Jiangjie (Becket) Qin
>>>>>>>> > > >
>>>>>>>> > > > On Thu, Jun 13, 2019 at 3:51 PM Piotr Nowojski <
>>>>>>>> piotr@ververica.com>
>>>>>>>> > > wrote:
>>>>>>>> > > >
>>>>>>>> > > >> Thanks for driving this. I’ve just noticed one small thing.
>>>>>>>> With new
>>>>>>>> > > >> SourceReader interface Flink will be able to provide
>>>>>>>> `idleTime` metric
>>>>>>>> > > >> automatically.
>>>>>>>> > > >>
>>>>>>>> > > >> Piotrek
>>>>>>>> > > >>
>>>>>>>> > > >>> On 13 Jun 2019, at 03:30, Becket Qin <be...@gmail.com>
>>>>>>>> wrote:
>>>>>>>> > > >>>
>>>>>>>> > > >>> Thanks all for the feedback and discussion.
>>>>>>>> > > >>>
>>>>>>>> > > >>> Since there wasn't any concern raised, I've started the
>>>>>>>> voting thread
>>>>>>>> > > for
>>>>>>>> > > >>> this FLIP, but please feel free to continue the discussion
>>>>>>>> here if
>>>>>>>> > you
>>>>>>>> > > >>> think something still needs to be addressed.
>>>>>>>> > > >>>
>>>>>>>> > > >>> Thanks,
>>>>>>>> > > >>>
>>>>>>>> > > >>> Jiangjie (Becket) Qin
>>>>>>>> > > >>>
>>>>>>>> > > >>>
>>>>>>>> > > >>>
>>>>>>>> > > >>> On Mon, Jun 10, 2019 at 9:10 AM Becket Qin <
>>>>>>>> becket.qin@gmail.com>
>>>>>>>> > > wrote:
>>>>>>>> > > >>>
>>>>>>>> > > >>>> Hi Piotr,
>>>>>>>> > > >>>>
>>>>>>>> > > >>>> Thanks for the comments. Yes, you are right. Users will
>>>>>>>> have to look
>>>>>>>> > > at
>>>>>>>> > > >>>> other metrics to decide whether the pipeline is healthy or
>>>>>>>> not in
>>>>>>>> > the
>>>>>>>> > > >> first
>>>>>>>> > > >>>> place before they can use the time-based metric to fix the
>>>>>>>> > bottleneck.
>>>>>>>> > > >>>>
>>>>>>>> > > >>>> I agree that once we have FLIP-27 ready, some of the
>>>>>>>> metrics can
>>>>>>>> > just
>>>>>>>> > > be
>>>>>>>> > > >>>> reported by the abstract implementation.
>>>>>>>> > > >>>>
>>>>>>>> > > >>>> I've updated FLIP-33 wiki page to add the pendingBytes and
>>>>>>>> > > >> pendingRecords
>>>>>>>> > > >>>> metric. Please let me know if you have any concern over
>>>>>>>> the updated
>>>>>>>> > > >> metric
>>>>>>>> > > >>>> convention proposal.
>>>>>>>> > > >>>>
>>>>>>>> > > >>>> @Chesnay Schepler <ch...@apache.org> @Stephan Ewen
>>>>>>>> > > >>>> <st...@ververica.com> will you also have time to take a
>>>>>>>> look at
>>>>>>>> > the
>>>>>>>> > > >>>> proposed metric convention? If there is no further concern
>>>>>>>> I'll
>>>>>>>> > start
>>>>>>>> > > a
>>>>>>>> > > >>>> voting thread for this FLIP in two days.
>>>>>>>> > > >>>>
>>>>>>>> > > >>>> Thanks,
>>>>>>>> > > >>>>
>>>>>>>> > > >>>> Jiangjie (Becket) Qin
>>>>>>>> > > >>>>
>>>>>>>> > > >>>>
>>>>>>>> > > >>>>
>>>>>>>> > > >>>> On Wed, Jun 5, 2019 at 6:54 PM Piotr Nowojski <
>>>>>>>> piotr@ververica.com>
>>>>>>>> > > >> wrote:
>>>>>>>> > > >>>>
>>>>>>>> > > >>>>> Hi Becket,
>>>>>>>> > > >>>>>
>>>>>>>> > > >>>>> Thanks for the answer :)
>>>>>>>> > > >>>>>
>>>>>>>> > > >>>>>> By time-based metric, I meant the portion of time spent
>>>>>>>> on
>>>>>>>> > producing
>>>>>>>> > > >> the
>>>>>>>> > > >>>>>> record to downstream. For example, a source connector
>>>>>>>> can report
>>>>>>>> > > that
>>>>>>>> > > >>>>> it's
>>>>>>>> > > >>>>>> spending 80% of time to emit record to downstream
>>>>>>>> processing
>>>>>>>> > > pipeline.
>>>>>>>> > > >>>>> In
>>>>>>>> > > >>>>>> another case, a sink connector may report that its
>>>>>>>> spending 30% of
>>>>>>>> > > >> time
>>>>>>>> > > >>>>>> producing the records to the external system.
>>>>>>>> > > >>>>>>
>>>>>>>> > > >>>>>> This is in some sense equivalent to the buffer usage
>>>>>>>> metric:
>>>>>>>> > > >>>>>
>>>>>>>> > > >>>>>> - 80% of time spent on emitting records to downstream
>>>>>>>> --->
>>>>>>>> > > downstream
>>>>>>>> > > >>>>>> node is bottleneck ---> output buffer is probably full.
>>>>>>>> > > >>>>>> - 30% of time spent on emitting records to downstream
>>>>>>>> --->
>>>>>>>> > > downstream
>>>>>>>> > > >>>>>> node is not bottleneck ---> output buffer is probably
>>>>>>>> not full.
>>>>>>>> > > >>>>>
>>>>>>>> > > >>>>> If by “time spent on emitting records to downstream” you
>>>>>>>> understand
>>>>>>>> > > >>>>> “waiting on back pressure”, then I see your point. And I
>>>>>>>> agree that
>>>>>>>> > > >> some
>>>>>>>> > > >>>>> kind of ratio/time based metric gives you more
>>>>>>>> information. However
>>>>>>>> > > >> under
>>>>>>>> > > >>>>> “time spent on emitting records to downstream” might be
>>>>>>>> hidden the
>>>>>>>> > > >>>>> following (extreme) situation:
>>>>>>>> > > >>>>>
>>>>>>>> > > >>>>> 1. Job is barely able to handle influx of records, there
>>>>>>>> is 99%
>>>>>>>> > > >>>>> CPU/resource usage in the cluster, but nobody is
>>>>>>>> > > >>>>> bottlenecked/backpressured, all output buffers are empty,
>>>>>>>> everybody
>>>>>>>> > > is
>>>>>>>> > > >>>>> waiting in 1% of it’s time for more records to process.
>>>>>>>> > > >>>>> 2. 80% time can still be spent on "down stream
>>>>>>>> operators”, because
>>>>>>>> > > they
>>>>>>>> > > >>>>> are the CPU intensive operations, but this doesn’t mean
>>>>>>>> that
>>>>>>>> > > >> increasing the
>>>>>>>> > > >>>>> parallelism down the stream will help with anything
>>>>>>>> there. To the
>>>>>>>> > > >> contrary,
>>>>>>>> > > >>>>> increasing parallelism of the source operator might help
>>>>>>>> to
>>>>>>>> > increase
>>>>>>>> > > >>>>> resource utilisation up to 100%.
>>>>>>>> > > >>>>>
>>>>>>>> > > >>>>> However, this “time based/ratio” approach can be extended
>>>>>>>> to
>>>>>>>> > > in/output
>>>>>>>> > > >>>>> buffer usage. Besides collecting an information that
>>>>>>>> input/output
>>>>>>>> > > >> buffer is
>>>>>>>> > > >>>>> full/empty, we can probe profile how often are buffer
>>>>>>>> empty/full.
>>>>>>>> > If
>>>>>>>> > > >> output
>>>>>>>> > > >>>>> buffer is full 1% of times, there is almost no back
>>>>>>>> pressure. If
>>>>>>>> > it’s
>>>>>>>> > > >> full
>>>>>>>> > > >>>>> 80% of times, there is some back pressure, if it’s full
>>>>>>>> 99.9% of
>>>>>>>> > > times,
>>>>>>>> > > >>>>> there is huge back pressure.
>>>>>>>> > > >>>>>
>>>>>>>> > > >>>>> Now for autoscaling you could compare the input & output
>>>>>>>> buffers
>>>>>>>> > fill
>>>>>>>> > > >>>>> ratio:
>>>>>>>> > > >>>>>
>>>>>>>> > > >>>>> 1. Both are high, the source of bottleneck is down the
>>>>>>>> stream
>>>>>>>> > > >>>>> 2. Output is low, input is high, this is the bottleneck
>>>>>>>> and the
>>>>>>>> > > higher
>>>>>>>> > > >>>>> the difference, the bigger source of bottleneck is this is
>>>>>>>> > > >> operator/task
>>>>>>>> > > >>>>> 3. Output is high, input is low - there was some load
>>>>>>>> spike that we
>>>>>>>> > > are
>>>>>>>> > > >>>>> currently finishing to process
>>>>>>>> > > >>>>>
>>>>>>>> > > >>>>>
>>>>>>>> > > >>>>>
>>>>>>>> > > >>>>> But long story short, we are probably diverging from the
>>>>>>>> topic of
>>>>>>>> > > this
>>>>>>>> > > >>>>> discussion, and we can discuss this at some later point.
>>>>>>>> > > >>>>>
>>>>>>>> > > >>>>> For now, for sources:
>>>>>>>> > > >>>>>
>>>>>>>> > > >>>>> as I wrote before, +1 for:
>>>>>>>> > > >>>>> - pending.bytes, Gauge
>>>>>>>> > > >>>>> - pending.messages, Gauge
>>>>>>>> > > >>>>>
>>>>>>>> > > >>>>> When we will be developing/discussing SourceReader from
>>>>>>>> FLIP-27 we
>>>>>>>> > > >> might
>>>>>>>> > > >>>>> then add:
>>>>>>>> > > >>>>>
>>>>>>>> > > >>>>> - in-memory.buffer.usage (0 - 100%)
>>>>>>>> > > >>>>>
>>>>>>>> > > >>>>> Which will be estimated automatically by Flink while user
>>>>>>>> will be
>>>>>>>> > > able
>>>>>>>> > > >> to
>>>>>>>> > > >>>>> override/provide better estimation.
>>>>>>>> > > >>>>>
>>>>>>>> > > >>>>> Piotrek
>>>>>>>> > > >>>>>
>>>>>>>> > > >>>>>> On 5 Jun 2019, at 05:42, Becket Qin <
>>>>>>>> becket.qin@gmail.com> wrote:
>>>>>>>> > > >>>>>>
>>>>>>>> > > >>>>>> Hi Piotr,
>>>>>>>> > > >>>>>>
>>>>>>>> > > >>>>>> Thanks for the explanation. Please see some
>>>>>>>> clarifications below.
>>>>>>>> > > >>>>>>
>>>>>>>> > > >>>>>> By time-based metric, I meant the portion of time spent
>>>>>>>> on
>>>>>>>> > producing
>>>>>>>> > > >> the
>>>>>>>> > > >>>>>> record to downstream. For example, a source connector
>>>>>>>> can report
>>>>>>>> > > that
>>>>>>>> > > >>>>> it's
>>>>>>>> > > >>>>>> spending 80% of time to emit record to downstream
>>>>>>>> processing
>>>>>>>> > > pipeline.
>>>>>>>> > > >>>>> In
>>>>>>>> > > >>>>>> another case, a sink connector may report that its
>>>>>>>> spending 30% of
>>>>>>>> > > >> time
>>>>>>>> > > >>>>>> producing the records to the external system.
>>>>>>>> > > >>>>>>
>>>>>>>> > > >>>>>> This is in some sense equivalent to the buffer usage
>>>>>>>> metric:
>>>>>>>> > > >>>>>> - 80% of time spent on emitting records to downstream
>>>>>>>> --->
>>>>>>>> > > downstream
>>>>>>>> > > >>>>>> node is bottleneck ---> output buffer is probably full.
>>>>>>>> > > >>>>>> - 30% of time spent on emitting records to downstream
>>>>>>>> --->
>>>>>>>> > > downstream
>>>>>>>> > > >>>>>> node is not bottleneck ---> output buffer is probably
>>>>>>>> not full.
>>>>>>>> > > >>>>>>
>>>>>>>> > > >>>>>> However, the time-based metric has a few advantages that
>>>>>>>> the
>>>>>>>> > buffer
>>>>>>>> > > >>>>> usage
>>>>>>>> > > >>>>>> metric may not have.
>>>>>>>> > > >>>>>>
>>>>>>>> > > >>>>>> 1. Buffer usage metric may not be applicable to all the
>>>>>>>> connector
>>>>>>>> > > >>>>>> implementations, while reporting time-based metric are
>>>>>>>> always
>>>>>>>> > > doable.
>>>>>>>> > > >>>>>> Some source connectors may not have any input buffer, or
>>>>>>>> they may
>>>>>>>> > > use
>>>>>>>> > > >>>>> some
>>>>>>>> > > >>>>>> third party library that does not expose the input
>>>>>>>> buffer at all.
>>>>>>>> > > >>>>>> Similarly, for sink connectors, the implementation may
>>>>>>>> not have
>>>>>>>> > any
>>>>>>>> > > >>>>> output
>>>>>>>> > > >>>>>> buffer, or the third party library does not expose such
>>>>>>>> buffer.
>>>>>>>> > > >>>>>>
>>>>>>>> > > >>>>>> 2. Although both type of metrics can detect bottleneck,
>>>>>>>> time-based
>>>>>>>> > > >>>>> metrics
>>>>>>>> > > >>>>>> can be used to generate a more informed action to remove
>>>>>>>> the
>>>>>>>> > > >> bottleneck.
>>>>>>>> > > >>>>>> For example, when the downstream is bottleneck, the
>>>>>>>> output buffer
>>>>>>>> > > >> usage
>>>>>>>> > > >>>>>> metric is likely to be 100%, and the input buffer usage
>>>>>>>> might be
>>>>>>>> > 0%.
>>>>>>>> > > >>>>> That
>>>>>>>> > > >>>>>> means we don't know what is the suitable parallelism to
>>>>>>>> lift the
>>>>>>>> > > >>>>>> bottleneck. The time-based metric, on the other hand,
>>>>>>>> would give
>>>>>>>> > > >> useful
>>>>>>>> > > >>>>>> information, e.g. if 80% of time was spent on emitting
>>>>>>>> records, we
>>>>>>>> > > can
>>>>>>>> > > >>>>>> roughly increase the downstream node parallelism by 4
>>>>>>>> times.
>>>>>>>> > > >>>>>>
>>>>>>>> > > >>>>>> Admittedly, the time-based metrics are more expensive
>>>>>>>> than buffer
>>>>>>>> > > >>>>> usage. So
>>>>>>>> > > >>>>>> we may have to do some sampling to reduce the cost. But
>>>>>>>> in
>>>>>>>> > general,
>>>>>>>> > > >>>>> using
>>>>>>>> > > >>>>>> time-based metrics seems worth adding.
>>>>>>>> > > >>>>>>
>>>>>>>> > > >>>>>> That being said, I don't think buffer usage metric and
>>>>>>>> time-based
>>>>>>>> > > >>>>> metrics
>>>>>>>> > > >>>>>> are mutually exclusive. We can probably have both. It is
>>>>>>>> just that
>>>>>>>> > > in
>>>>>>>> > > >>>>>> practice, features like auto-scaling might prefer
>>>>>>>> time-based
>>>>>>>> > metrics
>>>>>>>> > > >> for
>>>>>>>> > > >>>>>> the reason stated above.
>>>>>>>> > > >>>>>>
>>>>>>>> > > >>>>>>> 1. Define the metrics that would allow us to manually
>>>>>>>> detect
>>>>>>>> > > >>>>> bottlenecks.
>>>>>>>> > > >>>>>> As I wrote, we already have them in most of the places,
>>>>>>>> except of
>>>>>>>> > > >>>>>> sources/sinks.
>>>>>>>> > > >>>>>>> 2. Use those metrics, to automatically detect
>>>>>>>> bottlenecks.
>>>>>>>> > > Currently
>>>>>>>> > > >> we
>>>>>>>> > > >>>>>> are only automatically detecting back pressure and
>>>>>>>> reporting it to
>>>>>>>> > > the
>>>>>>>> > > >>>>> user
>>>>>>>> > > >>>>>> in web UI (is it exposed as a metric at all?). Detecting
>>>>>>>> the root
>>>>>>>> > > >> cause
>>>>>>>> > > >>>>> of
>>>>>>>> > > >>>>>> the back pressure (bottleneck) is one step further.
>>>>>>>> > > >>>>>>> 3. Use the knowledge about where exactly the bottleneck
>>>>>>>> is
>>>>>>>> > located,
>>>>>>>> > > >> to
>>>>>>>> > > >>>>>> try to do something with it.
>>>>>>>> > > >>>>>>
>>>>>>>> > > >>>>>> As explained above, I think time-based metric also
>>>>>>>> addresses item
>>>>>>>> > 1
>>>>>>>> > > >> and
>>>>>>>> > > >>>>>> item 2.
>>>>>>>> > > >>>>>>
>>>>>>>> > > >>>>>> Any thoughts？
>>>>>>>> > > >>>>>>
>>>>>>>> > > >>>>>> Thanks,
>>>>>>>> > > >>>>>>
>>>>>>>> > > >>>>>> Jiangjie (Becket) Qin
>>>>>>>> > > >>>>>>
>>>>>>>> > > >>>>>>
>>>>>>>> > > >>>>>>
>>>>>>>> > > >>>>>> On Mon, Jun 3, 2019 at 4:14 PM Piotr Nowojski <
>>>>>>>> > piotr@ververica.com>
>>>>>>>> > > >>>>> wrote:
>>>>>>>> > > >>>>>>
>>>>>>>> > > >>>>>>> Hi again :)
>>>>>>>> > > >>>>>>>
>>>>>>>> > > >>>>>>>> - pending.bytes, Gauge
>>>>>>>> > > >>>>>>>> - pending.messages, Gauge
>>>>>>>> > > >>>>>>>
>>>>>>>> > > >>>>>>>
>>>>>>>> > > >>>>>>> +1
>>>>>>>> > > >>>>>>>
>>>>>>>> > > >>>>>>> And true, instead of overloading one of the metric it
>>>>>>>> is better
>>>>>>>> > > when
>>>>>>>> > > >>>>> user
>>>>>>>> > > >>>>>>> can choose to provide only one of them.
>>>>>>>> > > >>>>>>>
>>>>>>>> > > >>>>>>> Re 2:
>>>>>>>> > > >>>>>>>
>>>>>>>> > > >>>>>>>> If I understand correctly, this metric along with the
>>>>>>>> pending
>>>>>>>> > > >> mesages
>>>>>>>> > > >>>>> /
>>>>>>>> > > >>>>>>>> bytes would answer the questions of:
>>>>>>>> > > >>>>>>>
>>>>>>>> > > >>>>>>>> - Does the connector consume fast enough? Lagging
>>>>>>>> behind + empty
>>>>>>>> > > >>>>> buffer
>>>>>>>> > > >>>>>>> =
>>>>>>>> > > >>>>>>>> cannot consume fast enough.
>>>>>>>> > > >>>>>>>> - Does the connector emit fast enough? Lagging behind
>>>>>>>> + full
>>>>>>>> > > buffer
>>>>>>>> > > >> =
>>>>>>>> > > >>>>>>>> cannot emit fast enough, i.e. the Flink pipeline is
>>>>>>>> slow.
>>>>>>>> > > >>>>>>>
>>>>>>>> > > >>>>>>> Yes, exactly. This can also be used to support
>>>>>>>> decisions like
>>>>>>>> > > >> changing
>>>>>>>> > > >>>>> the
>>>>>>>> > > >>>>>>> parallelism of the sources and/or down stream operators.
>>>>>>>> > > >>>>>>>
>>>>>>>> > > >>>>>>> I’m not sure if I understand your proposal with time
>>>>>>>> based
>>>>>>>> > > >>>>> measurements.
>>>>>>>> > > >>>>>>> Maybe I’m missing something, but I do not see how
>>>>>>>> measuring time
>>>>>>>> > > >> alone
>>>>>>>> > > >>>>>>> could answer the problem: where is the bottleneck. Time
>>>>>>>> spent on
>>>>>>>> > > the
>>>>>>>> > > >>>>>>> next/emit might be short or long (depending on how
>>>>>>>> heavy to
>>>>>>>> > process
>>>>>>>> > > >> the
>>>>>>>> > > >>>>>>> record is) and the source can still be bottlenecked/back
>>>>>>>> > pressured
>>>>>>>> > > or
>>>>>>>> > > >>>>> not.
>>>>>>>> > > >>>>>>> Usually the easiest and the most reliable way how to
>>>>>>>> detect
>>>>>>>> > > >>>>> bottlenecks is
>>>>>>>> > > >>>>>>> by checking usage of input & output buffers, since when
>>>>>>>> input
>>>>>>>> > > buffer
>>>>>>>> > > >> is
>>>>>>>> > > >>>>>>> full while output buffer is empty, that’s the
>>>>>>>> definition of a
>>>>>>>> > > >>>>> bottleneck.
>>>>>>>> > > >>>>>>> Also this is usually very easy and cheap to measure (it
>>>>>>>> works
>>>>>>>> > > >>>>> effectively
>>>>>>>> > > >>>>>>> the same way as current’s Flink back pressure
>>>>>>>> monitoring, but
>>>>>>>> > more
>>>>>>>> > > >>>>> cleanly,
>>>>>>>> > > >>>>>>> without probing thread’s stack traces).
>>>>>>>> > > >>>>>>>
>>>>>>>> > > >>>>>>> Also keep in mind that we are already using the buffer
>>>>>>>> usage
>>>>>>>> > > metrics
>>>>>>>> > > >>>>> for
>>>>>>>> > > >>>>>>> detecting the bottlenecks in Flink’s internal network
>>>>>>>> exchanges
>>>>>>>> > > >> (manual
>>>>>>>> > > >>>>>>> work). That’s the reason why I wanted to extend this to
>>>>>>>> > > >> sources/sinks,
>>>>>>>> > > >>>>>>> since they are currently our blind spot.
>>>>>>>> > > >>>>>>>
>>>>>>>> > > >>>>>>>> One feature we are currently working on to scale Flink
>>>>>>>> > > automatically
>>>>>>>> > > >>>>>>> relies
>>>>>>>> > > >>>>>>>> on some metrics answering the same question
>>>>>>>> > > >>>>>>>
>>>>>>>> > > >>>>>>> That would be very helpful feature. I think in order to
>>>>>>>> achieve
>>>>>>>> > > that
>>>>>>>> > > >> we
>>>>>>>> > > >>>>>>> would need to:
>>>>>>>> > > >>>>>>> 1. Define the metrics that would allow us to manually
>>>>>>>> detect
>>>>>>>> > > >>>>> bottlenecks.
>>>>>>>> > > >>>>>>> As I wrote, we already have them in most of the places,
>>>>>>>> except of
>>>>>>>> > > >>>>>>> sources/sinks.
>>>>>>>> > > >>>>>>> 2. Use those metrics, to automatically detect
>>>>>>>> bottlenecks.
>>>>>>>> > > Currently
>>>>>>>> > > >> we
>>>>>>>> > > >>>>>>> are only automatically detecting back pressure and
>>>>>>>> reporting it
>>>>>>>> > to
>>>>>>>> > > >> the
>>>>>>>> > > >>>>> user
>>>>>>>> > > >>>>>>> in web UI (is it exposed as a metric at all?).
>>>>>>>> Detecting the root
>>>>>>>> > > >>>>> cause of
>>>>>>>> > > >>>>>>> the back pressure (bottleneck) is one step further.
>>>>>>>> > > >>>>>>> 3. Use the knowledge about where exactly the bottleneck
>>>>>>>> is
>>>>>>>> > located,
>>>>>>>> > > >> to
>>>>>>>> > > >>>>> try
>>>>>>>> > > >>>>>>> to do something with it.
>>>>>>>> > > >>>>>>>
>>>>>>>> > > >>>>>>> I think you are aiming for point 3., but before we
>>>>>>>> reach it, we
>>>>>>>> > are
>>>>>>>> > > >>>>> still
>>>>>>>> > > >>>>>>> missing 1. & 2. Also even if we have 3., there is a
>>>>>>>> value in 1 &
>>>>>>>> > 2
>>>>>>>> > > >> for
>>>>>>>> > > >>>>>>> manual analysis/dashboards.
>>>>>>>> > > >>>>>>>
>>>>>>>> > > >>>>>>> However, having the knowledge of where the bottleneck
>>>>>>>> is, doesn’t
>>>>>>>> > > >>>>>>> necessarily mean that we know what we can do about it.
>>>>>>>> For
>>>>>>>> > example
>>>>>>>> > > >>>>>>> increasing parallelism might or might not help with
>>>>>>>> anything
>>>>>>>> > (data
>>>>>>>> > > >>>>> skew,
>>>>>>>> > > >>>>>>> bottleneck on some resource that does not scale), but
>>>>>>>> this remark
>>>>>>>> > > >>>>> applies
>>>>>>>> > > >>>>>>> always, regardless of the way how did we detect the
>>>>>>>> bottleneck.
>>>>>>>> > > >>>>>>>
>>>>>>>> > > >>>>>>> Piotrek
>>>>>>>> > > >>>>>>>
>>>>>>>> > > >>>>>>>> On 3 Jun 2019, at 06:16, Becket Qin <
>>>>>>>> becket.qin@gmail.com>
>>>>>>>> > wrote:
>>>>>>>> > > >>>>>>>>
>>>>>>>> > > >>>>>>>> Hi Piotr,
>>>>>>>> > > >>>>>>>>
>>>>>>>> > > >>>>>>>> Thanks for the suggestion. Some thoughts below:
>>>>>>>> > > >>>>>>>>
>>>>>>>> > > >>>>>>>> Re 1: The pending messages / bytes.
>>>>>>>> > > >>>>>>>> I completely agree these are very useful metrics and
>>>>>>>> we should
>>>>>>>> > > >> expect
>>>>>>>> > > >>>>> the
>>>>>>>> > > >>>>>>>> connector to report. WRT the way to expose them, it
>>>>>>>> seems more
>>>>>>>> > > >>>>> consistent
>>>>>>>> > > >>>>>>>> to add two metrics instead of adding a method (unless
>>>>>>>> there are
>>>>>>>> > > >> other
>>>>>>>> > > >>>>> use
>>>>>>>> > > >>>>>>>> cases other than metric reporting). So we can add the
>>>>>>>> following
>>>>>>>> > > two
>>>>>>>> > > >>>>>>> metrics.
>>>>>>>> > > >>>>>>>> - pending.bytes, Gauge
>>>>>>>> > > >>>>>>>> - pending.messages, Gauge
>>>>>>>> > > >>>>>>>> Applicable connectors can choose to report them. These
>>>>>>>> two
>>>>>>>> > metrics
>>>>>>>> > > >>>>> along
>>>>>>>> > > >>>>>>>> with latency should be sufficient for users to
>>>>>>>> understand the
>>>>>>>> > > >> progress
>>>>>>>> > > >>>>>>> of a
>>>>>>>> > > >>>>>>>> connector.
>>>>>>>> > > >>>>>>>>
>>>>>>>> > > >>>>>>>>
>>>>>>>> > > >>>>>>>> Re 2: Number of buffered data in-memory of the
>>>>>>>> connector
>>>>>>>> > > >>>>>>>> If I understand correctly, this metric along with the
>>>>>>>> pending
>>>>>>>> > > >> mesages
>>>>>>>> > > >>>>> /
>>>>>>>> > > >>>>>>>> bytes would answer the questions of:
>>>>>>>> > > >>>>>>>> - Does the connector consume fast enough? Lagging
>>>>>>>> behind + empty
>>>>>>>> > > >>>>> buffer
>>>>>>>> > > >>>>>>> =
>>>>>>>> > > >>>>>>>> cannot consume fast enough.
>>>>>>>> > > >>>>>>>> - Does the connector emit fast enough? Lagging behind
>>>>>>>> + full
>>>>>>>> > > buffer
>>>>>>>> > > >> =
>>>>>>>> > > >>>>>>>> cannot emit fast enough, i.e. the Flink pipeline is
>>>>>>>> slow.
>>>>>>>> > > >>>>>>>>
>>>>>>>> > > >>>>>>>> One feature we are currently working on to scale Flink
>>>>>>>> > > automatically
>>>>>>>> > > >>>>>>> relies
>>>>>>>> > > >>>>>>>> on some metrics answering the same question, more
>>>>>>>> specifically,
>>>>>>>> > we
>>>>>>>> > > >> are
>>>>>>>> > > >>>>>>>> profiling the time spent on .next() method (time to
>>>>>>>> consume) and
>>>>>>>> > > the
>>>>>>>> > > >>>>> time
>>>>>>>> > > >>>>>>>> spent on .collect() method (time to emit / process).
>>>>>>>> One
>>>>>>>> > advantage
>>>>>>>> > > >> of
>>>>>>>> > > >>>>>>> such
>>>>>>>> > > >>>>>>>> method level time cost allows us to calculate the
>>>>>>>> parallelism
>>>>>>>> > > >>>>> required to
>>>>>>>> > > >>>>>>>> keep up in case their is a lag.
>>>>>>>> > > >>>>>>>>
>>>>>>>> > > >>>>>>>> However, one concern I have regarding such metric is
>>>>>>>> that they
>>>>>>>> > are
>>>>>>>> > > >>>>>>>> implementation specific. Either profiling on the
>>>>>>>> method time, or
>>>>>>>> > > >>>>>>> reporting
>>>>>>>> > > >>>>>>>> buffer usage assumes the connector are implemented in
>>>>>>>> such a
>>>>>>>> > way.
>>>>>>>> > > A
>>>>>>>> > > >>>>>>>> slightly better solution might be have the following
>>>>>>>> metric:
>>>>>>>> > > >>>>>>>>
>>>>>>>> > > >>>>>>>> - EmitTimeRatio (or FetchTimeRatio): The time spent
>>>>>>>> on emitting
>>>>>>>> > > >>>>>>>> records / Total time elapsed.
>>>>>>>> > > >>>>>>>>
>>>>>>>> > > >>>>>>>> This assumes that the source connectors have to emit
>>>>>>>> the records
>>>>>>>> > > to
>>>>>>>> > > >>>>> the
>>>>>>>> > > >>>>>>>> downstream at some point. The emission may take some
>>>>>>>> time ( e.g.
>>>>>>>> > > go
>>>>>>>> > > >>>>>>> through
>>>>>>>> > > >>>>>>>> chained operators). And the rest of the time are spent
>>>>>>>> to
>>>>>>>> > prepare
>>>>>>>> > > >> the
>>>>>>>> > > >>>>>>>> record to emit, including time for consuming and format
>>>>>>>> > > conversion,
>>>>>>>> > > >>>>> etc.
>>>>>>>> > > >>>>>>>> Ideally, we'd like to see the time spent on record
>>>>>>>> fetch and
>>>>>>>> > emit
>>>>>>>> > > to
>>>>>>>> > > >>>>> be
>>>>>>>> > > >>>>>>>> about the same, so no one is bottleneck for the other.
>>>>>>>> > > >>>>>>>>
>>>>>>>> > > >>>>>>>> The downside of these time based metrics is additional
>>>>>>>> overhead
>>>>>>>> > to
>>>>>>>> > > >> get
>>>>>>>> > > >>>>>>> the
>>>>>>>> > > >>>>>>>> time, therefore sampling might be needed. But in
>>>>>>>> practice I feel
>>>>>>>> > > >> such
>>>>>>>> > > >>>>>>> time
>>>>>>>> > > >>>>>>>> based metric might be more useful if we want to take
>>>>>>>> action.
>>>>>>>> > > >>>>>>>>
>>>>>>>> > > >>>>>>>>
>>>>>>>> > > >>>>>>>> I think we should absolutely add metrics in (1) to the
>>>>>>>> metric
>>>>>>>> > > >>>>> convention.
>>>>>>>> > > >>>>>>>> We could also add the metrics mentioned in (2) if we
>>>>>>>> reach
>>>>>>>> > > consensus
>>>>>>>> > > >>>>> on
>>>>>>>> > > >>>>>>>> that. What do you think?
>>>>>>>> > > >>>>>>>>
>>>>>>>> > > >>>>>>>> Thanks,
>>>>>>>> > > >>>>>>>>
>>>>>>>> > > >>>>>>>> Jiangjie (Becket) Qin
>>>>>>>> > > >>>>>>>>
>>>>>>>> > > >>>>>>>>
>>>>>>>> > > >>>>>>>> On Fri, May 31, 2019 at 4:26 PM Piotr Nowojski <
>>>>>>>> > > piotr@ververica.com
>>>>>>>> > > >>>
>>>>>>>> > > >>>>>>> wrote:
>>>>>>>> > > >>>>>>>>
>>>>>>>> > > >>>>>>>>> Hey Becket,
>>>>>>>> > > >>>>>>>>>
>>>>>>>> > > >>>>>>>>> Re 1a) and 1b) +1 from my side.
>>>>>>>> > > >>>>>>>>>
>>>>>>>> > > >>>>>>>>> I’ve discussed this issue:
>>>>>>>> > > >>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>> 2. It would be nice to have metrics, that allow us
>>>>>>>> to check
>>>>>>>> > > the
>>>>>>>> > > >>>>> cause
>>>>>>>> > > >>>>>>>>> of
>>>>>>>> > > >>>>>>>>>>>> back pressure:
>>>>>>>> > > >>>>>>>>>>>> a) for sources, length of input queue (in bytes?
>>>>>>>> Or boolean
>>>>>>>> > > >>>>>>>>>>>> hasSomethingl/isEmpty)
>>>>>>>> > > >>>>>>>>>>>> b) for sinks, length of output queue (in bytes? Or
>>>>>>>> boolean
>>>>>>>> > > >>>>>>>>>>>> hasSomething/isEmpty)
>>>>>>>> > > >>>>>>>>>
>>>>>>>> > > >>>>>>>>> With Nico at some lengths and he also saw the
>>>>>>>> benefits of them.
>>>>>>>> > > We
>>>>>>>> > > >>>>> also
>>>>>>>> > > >>>>>>>>> have more concrete proposal for that.
>>>>>>>> > > >>>>>>>>>
>>>>>>>> > > >>>>>>>>> Actually there are two really useful metrics, that we
>>>>>>>> are
>>>>>>>> > missing
>>>>>>>> > > >>>>>>>>> currently:
>>>>>>>> > > >>>>>>>>>
>>>>>>>> > > >>>>>>>>> 1. Number of data/records/bytes in the backlog to
>>>>>>>> process. For
>>>>>>>> > > >>>>> example
>>>>>>>> > > >>>>>>>>> remaining number of bytes in unread files. Or pending
>>>>>>>> data in
>>>>>>>> > > Kafka
>>>>>>>> > > >>>>>>> topics.
>>>>>>>> > > >>>>>>>>> 2. Number of buffered data in-memory of the
>>>>>>>> connector, that are
>>>>>>>> > > >>>>> waiting
>>>>>>>> > > >>>>>>> to
>>>>>>>> > > >>>>>>>>> be processed pushed to Flink pipeline.
>>>>>>>> > > >>>>>>>>>
>>>>>>>> > > >>>>>>>>> Re 1:
>>>>>>>> > > >>>>>>>>> This would have to be a metric provided directly by a
>>>>>>>> > connector.
>>>>>>>> > > It
>>>>>>>> > > >>>>>>> could
>>>>>>>> > > >>>>>>>>> be an undefined `int`:
>>>>>>>> > > >>>>>>>>>
>>>>>>>> > > >>>>>>>>> `int backlog` - estimate of pending work.
>>>>>>>> > > >>>>>>>>>
>>>>>>>> > > >>>>>>>>> “Undefined” meaning that it would be up to a
>>>>>>>> connector to
>>>>>>>> > decided
>>>>>>>> > > >>>>>>> whether
>>>>>>>> > > >>>>>>>>> it’s measured in bytes, records, pending files or
>>>>>>>> whatever it
>>>>>>>> > is
>>>>>>>> > > >>>>>>> possible
>>>>>>>> > > >>>>>>>>> to provide by the connector. This is because I assume
>>>>>>>> not every
>>>>>>>> > > >>>>>>> connector
>>>>>>>> > > >>>>>>>>> can provide exact number and for some of them it
>>>>>>>> might be
>>>>>>>> > > >> impossible
>>>>>>>> > > >>>>> to
>>>>>>>> > > >>>>>>>>> provide records number of bytes count.
>>>>>>>> > > >>>>>>>>>
>>>>>>>> > > >>>>>>>>> Re 2:
>>>>>>>> > > >>>>>>>>> This metric could be either provided by a connector,
>>>>>>>> or
>>>>>>>> > > calculated
>>>>>>>> > > >>>>>>> crudely
>>>>>>>> > > >>>>>>>>> by Flink:
>>>>>>>> > > >>>>>>>>>
>>>>>>>> > > >>>>>>>>> `float bufferUsage` - value from [0.0, 1.0] range
>>>>>>>> > > >>>>>>>>>
>>>>>>>> > > >>>>>>>>> Percentage of used in memory buffers, like in Kafka’s
>>>>>>>> handover.
>>>>>>>> > > >>>>>>>>>
>>>>>>>> > > >>>>>>>>> It could be crudely implemented by Flink with FLIP-27
>>>>>>>> > > >>>>>>>>> SourceReader#isAvailable. If SourceReader is not
>>>>>>>> available
>>>>>>>> > > reported
>>>>>>>> > > >>>>>>>>> `bufferUsage` could be 0.0. If it is available, it
>>>>>>>> could be
>>>>>>>> > 1.0.
>>>>>>>> > > I
>>>>>>>> > > >>>>> think
>>>>>>>> > > >>>>>>>>> this would be a good enough estimation for most of
>>>>>>>> the use
>>>>>>>> > cases
>>>>>>>> > > >>>>> (that
>>>>>>>> > > >>>>>>>>> could be overloaded and implemented better if
>>>>>>>> desired).
>>>>>>>> > > Especially
>>>>>>>> > > >>>>>>> since we
>>>>>>>> > > >>>>>>>>> are reporting only probed values: if probed values
>>>>>>>> are almost
>>>>>>>> > > >> always
>>>>>>>> > > >>>>>>> “1.0”,
>>>>>>>> > > >>>>>>>>> it would mean that we have a back pressure. If they
>>>>>>>> are almost
>>>>>>>> > > >> always
>>>>>>>> > > >>>>>>>>> “0.0”, there is probably no back pressure at the
>>>>>>>> sources.
>>>>>>>> > > >>>>>>>>>
>>>>>>>> > > >>>>>>>>> What do you think about this?
>>>>>>>> > > >>>>>>>>>
>>>>>>>> > > >>>>>>>>> Piotrek
>>>>>>>> > > >>>>>>>>>
>>>>>>>> > > >>>>>>>>>> On 30 May 2019, at 11:41, Becket Qin <
>>>>>>>> becket.qin@gmail.com>
>>>>>>>> > > >> wrote:
>>>>>>>> > > >>>>>>>>>>
>>>>>>>> > > >>>>>>>>>> Hi all,
>>>>>>>> > > >>>>>>>>>>
>>>>>>>> > > >>>>>>>>>> Thanks a lot for all the feedback and comments. I'd
>>>>>>>> like to
>>>>>>>> > > >> continue
>>>>>>>> > > >>>>>>> the
>>>>>>>> > > >>>>>>>>>> discussion on this FLIP.
>>>>>>>> > > >>>>>>>>>>
>>>>>>>> > > >>>>>>>>>> I updated the FLIP-33 wiki to remove all the
>>>>>>>> histogram metrics
>>>>>>>> > > >> from
>>>>>>>> > > >>>>> the
>>>>>>>> > > >>>>>>>>>> first version of metric convention due to the
>>>>>>>> performance
>>>>>>>> > > concern.
>>>>>>>> > > >>>>> The
>>>>>>>> > > >>>>>>>>> plan
>>>>>>>> > > >>>>>>>>>> is to introduce them later when we have a mechanism
>>>>>>>> to opt
>>>>>>>> > > in/out
>>>>>>>> > > >>>>>>>>> metrics.
>>>>>>>> > > >>>>>>>>>> At that point, users can decide whether they want to
>>>>>>>> pay the
>>>>>>>> > > cost
>>>>>>>> > > >> to
>>>>>>>> > > >>>>>>> get
>>>>>>>> > > >>>>>>>>>> the metric or not.
>>>>>>>> > > >>>>>>>>>>
>>>>>>>> > > >>>>>>>>>> As Stephan suggested, for this FLIP, let's first try
>>>>>>>> to agree
>>>>>>>> > on
>>>>>>>> > > >> the
>>>>>>>> > > >>>>>>>>> small
>>>>>>>> > > >>>>>>>>>> list of conventional metrics that connectors should
>>>>>>>> follow.
>>>>>>>> > > >>>>>>>>>> Just to be clear, the purpose of the convention is
>>>>>>>> not to
>>>>>>>> > > enforce
>>>>>>>> > > >>>>> every
>>>>>>>> > > >>>>>>>>>> connector to report all these metrics, but to
>>>>>>>> provide a
>>>>>>>> > guidance
>>>>>>>> > > >> in
>>>>>>>> > > >>>>>>> case
>>>>>>>> > > >>>>>>>>>> these metrics are reported by some connectors.
>>>>>>>> > > >>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>
>>>>>>>> > > >>>>>>>>>> @ Stephan & Chesnay,
>>>>>>>> > > >>>>>>>>>>
>>>>>>>> > > >>>>>>>>>> Regarding the duplication of `RecordsIn` metric in
>>>>>>>> operator /
>>>>>>>> > > task
>>>>>>>> > > >>>>>>>>>> IOMetricGroups, from what I understand, for source
>>>>>>>> operator,
>>>>>>>> > it
>>>>>>>> > > is
>>>>>>>> > > >>>>>>>>> actually
>>>>>>>> > > >>>>>>>>>> the SourceFunction that reports the operator level
>>>>>>>> > > >>>>>>>>>> RecordsIn/RecordsInPerSecond metric. So they are
>>>>>>>> essentially
>>>>>>>> > the
>>>>>>>> > > >>>>> same
>>>>>>>> > > >>>>>>>>>> metric in the operator level IOMetricGroup.
>>>>>>>> Similarly for the
>>>>>>>> > > Sink
>>>>>>>> > > >>>>>>>>>> operator, the operator level
>>>>>>>> RecordsOut/RecordsOutPerSecond
>>>>>>>> > > >> metrics
>>>>>>>> > > >>>>> are
>>>>>>>> > > >>>>>>>>>> also reported by the Sink function. I marked them as
>>>>>>>> existing
>>>>>>>> > in
>>>>>>>> > > >> the
>>>>>>>> > > >>>>>>>>>> FLIP-33 wiki page. Please let me know if I
>>>>>>>> misunderstood.
>>>>>>>> > > >>>>>>>>>>
>>>>>>>> > > >>>>>>>>>> Thanks,
>>>>>>>> > > >>>>>>>>>>
>>>>>>>> > > >>>>>>>>>> Jiangjie (Becket) Qin
>>>>>>>> > > >>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>
>>>>>>>> > > >>>>>>>>>> On Thu, May 30, 2019 at 5:16 PM Becket Qin <
>>>>>>>> > > becket.qin@gmail.com>
>>>>>>>> > > >>>>>>> wrote:
>>>>>>>> > > >>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>> Hi Piotr,
>>>>>>>> > > >>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>> Thanks a lot for the feedback.
>>>>>>>> > > >>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>> 1a) I guess you are referring to the part that
>>>>>>>> "original
>>>>>>>> > system
>>>>>>>> > > >>>>>>> specific
>>>>>>>> > > >>>>>>>>>>> metrics should also be reported". The performance
>>>>>>>> impact
>>>>>>>> > > depends
>>>>>>>> > > >> on
>>>>>>>> > > >>>>>>> the
>>>>>>>> > > >>>>>>>>>>> implementation. An efficient implementation would
>>>>>>>> only record
>>>>>>>> > > the
>>>>>>>> > > >>>>>>> metric
>>>>>>>> > > >>>>>>>>>>> once, but report them with two different metric
>>>>>>>> names. This
>>>>>>>> > is
>>>>>>>> > > >>>>>>> unlikely
>>>>>>>> > > >>>>>>>>> to
>>>>>>>> > > >>>>>>>>>>> hurt performance.
>>>>>>>> > > >>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>> 1b) Yes, I agree that we should avoid adding
>>>>>>>> overhead to the
>>>>>>>> > > >>>>> critical
>>>>>>>> > > >>>>>>>>> path
>>>>>>>> > > >>>>>>>>>>> by all means. This is sometimes a tradeoff, running
>>>>>>>> blindly
>>>>>>>> > > >> without
>>>>>>>> > > >>>>>>> any
>>>>>>>> > > >>>>>>>>>>> metric gives best performance, but sometimes might
>>>>>>>> be
>>>>>>>> > > frustrating
>>>>>>>> > > >>>>> when
>>>>>>>> > > >>>>>>>>> we
>>>>>>>> > > >>>>>>>>>>> debug some issues.
>>>>>>>> > > >>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>> 2. The metrics are indeed very useful. Are they
>>>>>>>> supposed to
>>>>>>>> > be
>>>>>>>> > > >>>>>>> reported
>>>>>>>> > > >>>>>>>>> by
>>>>>>>> > > >>>>>>>>>>> the connectors or Flink itself? At this point
>>>>>>>> FLIP-33 is more
>>>>>>>> > > >>>>> focused
>>>>>>>> > > >>>>>>> on
>>>>>>>> > > >>>>>>>>>>> provide a guidance to the connector authors on the
>>>>>>>> metrics
>>>>>>>> > > >>>>> reporting.
>>>>>>>> > > >>>>>>>>> That
>>>>>>>> > > >>>>>>>>>>> said, after FLIP-27, I think we should absolutely
>>>>>>>> report
>>>>>>>> > these
>>>>>>>> > > >>>>> metrics
>>>>>>>> > > >>>>>>>>> in
>>>>>>>> > > >>>>>>>>>>> the abstract implementation. In any case, the metric
>>>>>>>> > convention
>>>>>>>> > > >> in
>>>>>>>> > > >>>>>>> this
>>>>>>>> > > >>>>>>>>>>> list are expected to evolve over time.
>>>>>>>> > > >>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>> Thanks,
>>>>>>>> > > >>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>> Jiangjie (Becket) Qin
>>>>>>>> > > >>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>> On Tue, May 28, 2019 at 6:24 PM Piotr Nowojski <
>>>>>>>> > > >>>>> piotr@ververica.com>
>>>>>>>> > > >>>>>>>>>>> wrote:
>>>>>>>> > > >>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>> Hi,
>>>>>>>> > > >>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>> Thanks for the proposal and driving the effort
>>>>>>>> here Becket
>>>>>>>> > :)
>>>>>>>> > > >> I’ve
>>>>>>>> > > >>>>>>> read
>>>>>>>> > > >>>>>>>>>>>> through the FLIP-33 [1], and here are couple of my
>>>>>>>> thoughts.
>>>>>>>> > > >>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>> Big +1 for standardising the metric names between
>>>>>>>> > connectors,
>>>>>>>> > > it
>>>>>>>> > > >>>>> will
>>>>>>>> > > >>>>>>>>>>>> definitely help us and users a lot.
>>>>>>>> > > >>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>> Issues/questions/things to discuss that I’ve
>>>>>>>> thought of:
>>>>>>>> > > >>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>> 1a. If we are about to duplicate some metrics, can
>>>>>>>> this
>>>>>>>> > > become a
>>>>>>>> > > >>>>>>>>>>>> performance issue?
>>>>>>>> > > >>>>>>>>>>>> 1b. Generally speaking, we should make sure that
>>>>>>>> collecting
>>>>>>>> > > >> those
>>>>>>>> > > >>>>>>>>> metrics
>>>>>>>> > > >>>>>>>>>>>> is as non intrusive as possible, especially that
>>>>>>>> they will
>>>>>>>> > > need
>>>>>>>> > > >>>>> to be
>>>>>>>> > > >>>>>>>>>>>> updated once per record. (They might be collected
>>>>>>>> more
>>>>>>>> > rarely
>>>>>>>> > > >> with
>>>>>>>> > > >>>>>>> some
>>>>>>>> > > >>>>>>>>>>>> overhead, but the hot path of updating it per
>>>>>>>> record will
>>>>>>>> > need
>>>>>>>> > > >> to
>>>>>>>> > > >>>>> be
>>>>>>>> > > >>>>>>> as
>>>>>>>> > > >>>>>>>>>>>> quick as possible). That includes both avoiding
>>>>>>>> heavy
>>>>>>>> > > >> computation
>>>>>>>> > > >>>>> on
>>>>>>>> > > >>>>>>>>> per
>>>>>>>> > > >>>>>>>>>>>> record path: histograms?, measuring time for time
>>>>>>>> based
>>>>>>>> > > metrics
>>>>>>>> > > >>>>> (per
>>>>>>>> > > >>>>>>>>>>>> second) (System.currentTimeMillis() depending on
>>>>>>>> the
>>>>>>>> > > >>>>> implementation
>>>>>>>> > > >>>>>>> can
>>>>>>>> > > >>>>>>>>>>>> invoke a system call)
>>>>>>>> > > >>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>> 2. It would be nice to have metrics, that allow us
>>>>>>>> to check
>>>>>>>> > > the
>>>>>>>> > > >>>>> cause
>>>>>>>> > > >>>>>>>>> of
>>>>>>>> > > >>>>>>>>>>>> back pressure:
>>>>>>>> > > >>>>>>>>>>>> a) for sources, length of input queue (in bytes?
>>>>>>>> Or boolean
>>>>>>>> > > >>>>>>>>>>>> hasSomethingl/isEmpty)
>>>>>>>> > > >>>>>>>>>>>> b) for sinks, length of output queue (in bytes? Or
>>>>>>>> boolean
>>>>>>>> > > >>>>>>>>>>>> hasSomething/isEmpty)
>>>>>>>> > > >>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>> a) is useful in a scenario when we are processing
>>>>>>>> backlog of
>>>>>>>> > > >>>>> records,
>>>>>>>> > > >>>>>>>>> all
>>>>>>>> > > >>>>>>>>>>>> of the internal Flink’s input/output network
>>>>>>>> buffers are
>>>>>>>> > > empty,
>>>>>>>> > > >>>>> and
>>>>>>>> > > >>>>>>> we
>>>>>>>> > > >>>>>>>>> want
>>>>>>>> > > >>>>>>>>>>>> to check whether the external source system is the
>>>>>>>> > bottleneck
>>>>>>>> > > >>>>>>> (source’s
>>>>>>>> > > >>>>>>>>>>>> input queue will be empty), or if the Flink’s
>>>>>>>> connector is
>>>>>>>> > the
>>>>>>>> > > >>>>>>>>> bottleneck
>>>>>>>> > > >>>>>>>>>>>> (source’s input queues will be full).
>>>>>>>> > > >>>>>>>>>>>> b) similar story. Backlog of records, but this
>>>>>>>> time all of
>>>>>>>> > the
>>>>>>>> > > >>>>>>> internal
>>>>>>>> > > >>>>>>>>>>>> Flink’s input/ouput network buffers are full, and
>>>>>>>> we want o
>>>>>>>> > > >> check
>>>>>>>> > > >>>>>>>>> whether
>>>>>>>> > > >>>>>>>>>>>> the external sink system is the bottleneck (sink
>>>>>>>> output
>>>>>>>> > queues
>>>>>>>> > > >> are
>>>>>>>> > > >>>>>>>>> full),
>>>>>>>> > > >>>>>>>>>>>> or if the Flink’s connector is the bottleneck
>>>>>>>> (sink’s output
>>>>>>>> > > >>>>> queues
>>>>>>>> > > >>>>>>>>> will be
>>>>>>>> > > >>>>>>>>>>>> empty)
>>>>>>>> > > >>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>> It might be sometimes difficult to provide those
>>>>>>>> metrics, so
>>>>>>>> > > >> they
>>>>>>>> > > >>>>>>> could
>>>>>>>> > > >>>>>>>>>>>> be optional, but if we could provide them, it
>>>>>>>> would be
>>>>>>>> > really
>>>>>>>> > > >>>>>>> helpful.
>>>>>>>> > > >>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>> Piotrek
>>>>>>>> > > >>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>> [1]
>>>>>>>> > > >>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>
>>>>>>>> > > >>>>>>>
>>>>>>>> > > >>>>>
>>>>>>>> > > >>
>>>>>>>> > >
>>>>>>>> >
>>>>>>>> https://cwiki.apache.org/confluence/display/FLINK/FLIP-33:+Standardize+Connector+Metrics
>>>>>>>> > > >>>>>>>>>>>> <
>>>>>>>> > > >>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>
>>>>>>>> > > >>>>>>>
>>>>>>>> > > >>>>>
>>>>>>>> > > >>
>>>>>>>> > >
>>>>>>>> >
>>>>>>>> https://cwiki.apache.org/confluence/display/FLINK/FLIP-33:+Standardize+Connector+Metrics
>>>>>>>> > > >>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>> On 24 Apr 2019, at 13:28, Stephan Ewen <
>>>>>>>> sewen@apache.org>
>>>>>>>> > > >> wrote:
>>>>>>>> > > >>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>> I think this sounds reasonable.
>>>>>>>> > > >>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>> Let's keep the "reconfiguration without stopping
>>>>>>>> the job"
>>>>>>>> > out
>>>>>>>> > > >> of
>>>>>>>> > > >>>>>>> this,
>>>>>>>> > > >>>>>>>>>>>>> because that would be a super big effort and if
>>>>>>>> we approach
>>>>>>>> > > >> that,
>>>>>>>> > > >>>>>>> then
>>>>>>>> > > >>>>>>>>>>>> in
>>>>>>>> > > >>>>>>>>>>>>> more generic way rather than specific to
>>>>>>>> connector metrics.
>>>>>>>> > > >>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>> I would suggest to look at the following things
>>>>>>>> before
>>>>>>>> > > starting
>>>>>>>> > > >>>>> with
>>>>>>>> > > >>>>>>>>> any
>>>>>>>> > > >>>>>>>>>>>>> implementation work:
>>>>>>>> > > >>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>> - Try and find a committer to support this,
>>>>>>>> otherwise it
>>>>>>>> > will
>>>>>>>> > > >> be
>>>>>>>> > > >>>>>>> hard
>>>>>>>> > > >>>>>>>>>>>> to
>>>>>>>> > > >>>>>>>>>>>>> make progress
>>>>>>>> > > >>>>>>>>>>>>> - Start with defining a smaller set of "core
>>>>>>>> metrics" and
>>>>>>>> > > >> extend
>>>>>>>> > > >>>>> the
>>>>>>>> > > >>>>>>>>>>>> set
>>>>>>>> > > >>>>>>>>>>>>> later. I think that is easier than now blocking
>>>>>>>> on reaching
>>>>>>>> > > >>>>>>> consensus
>>>>>>>> > > >>>>>>>>>>>> on a
>>>>>>>> > > >>>>>>>>>>>>> large group of metrics.
>>>>>>>> > > >>>>>>>>>>>>> - Find a solution to the problem Chesnay
>>>>>>>> mentioned, that
>>>>>>>> > the
>>>>>>>> > > >>>>>>> "records
>>>>>>>> > > >>>>>>>>>>>> in"
>>>>>>>> > > >>>>>>>>>>>>> metric is somehow overloaded and exists already
>>>>>>>> in the IO
>>>>>>>> > > >> Metric
>>>>>>>> > > >>>>>>>>> group.
>>>>>>>> > > >>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>> On Mon, Mar 25, 2019 at 7:16 AM Becket Qin <
>>>>>>>> > > >> becket.qin@gmail.com
>>>>>>>> > > >>>>>>
>>>>>>>> > > >>>>>>>>>>>> wrote:
>>>>>>>> > > >>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>> Hi Stephan,
>>>>>>>> > > >>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>> Thanks a lot for the feedback. All makes sense.
>>>>>>>> > > >>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>> It is a good suggestion to simply have an
>>>>>>>> > onRecord(numBytes,
>>>>>>>> > > >>>>>>>>> eventTime)
>>>>>>>> > > >>>>>>>>>>>>>> method for connector writers. It should meet
>>>>>>>> most of the
>>>>>>>> > > >>>>>>>>> requirements,
>>>>>>>> > > >>>>>>>>>>>>>> individual
>>>>>>>> > > >>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>> The configurable metrics feature is something
>>>>>>>> really
>>>>>>>> > useful,
>>>>>>>> > > >>>>>>>>>>>> especially if
>>>>>>>> > > >>>>>>>>>>>>>> we can somehow make it dynamically configurable
>>>>>>>> without
>>>>>>>> > > >> stopping
>>>>>>>> > > >>>>>>> the
>>>>>>>> > > >>>>>>>>>>>> jobs.
>>>>>>>> > > >>>>>>>>>>>>>> It might be better to make it a separate
>>>>>>>> discussion
>>>>>>>> > because
>>>>>>>> > > it
>>>>>>>> > > >>>>> is a
>>>>>>>> > > >>>>>>>>>>>> more
>>>>>>>> > > >>>>>>>>>>>>>> generic feature instead of only for connectors.
>>>>>>>> > > >>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>> So in order to make some progress, in this FLIP
>>>>>>>> we can
>>>>>>>> > limit
>>>>>>>> > > >> the
>>>>>>>> > > >>>>>>>>>>>> discussion
>>>>>>>> > > >>>>>>>>>>>>>> scope to the connector related items:
>>>>>>>> > > >>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>> - the standard connector metric names and types.
>>>>>>>> > > >>>>>>>>>>>>>> - the abstract ConnectorMetricHandler interface
>>>>>>>> > > >>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>> I'll start a separate thread to discuss other
>>>>>>>> general
>>>>>>>> > metric
>>>>>>>> > > >>>>>>> related
>>>>>>>> > > >>>>>>>>>>>>>> enhancement items including:
>>>>>>>> > > >>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>> - optional metrics
>>>>>>>> > > >>>>>>>>>>>>>> - dynamic metric configuration
>>>>>>>> > > >>>>>>>>>>>>>> - potential combination with rate limiter
>>>>>>>> > > >>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>> Does this plan sound reasonable?
>>>>>>>> > > >>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>> Thanks,
>>>>>>>> > > >>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>> Jiangjie (Becket) Qin
>>>>>>>> > > >>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>> On Sat, Mar 23, 2019 at 5:53 AM Stephan Ewen <
>>>>>>>> > > >> sewen@apache.org>
>>>>>>>> > > >>>>>>>>> wrote:
>>>>>>>> > > >>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>> Ignoring for a moment implementation details,
>>>>>>>> this
>>>>>>>> > > connector
>>>>>>>> > > >>>>>>> metrics
>>>>>>>> > > >>>>>>>>>>>> work
>>>>>>>> > > >>>>>>>>>>>>>>> is a really good thing to do, in my opinion
>>>>>>>> > > >>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>> The questions "oh, my job seems to be doing
>>>>>>>> nothing, I am
>>>>>>>> > > >>>>> looking
>>>>>>>> > > >>>>>>> at
>>>>>>>> > > >>>>>>>>>>>> the
>>>>>>>> > > >>>>>>>>>>>>>> UI
>>>>>>>> > > >>>>>>>>>>>>>>> and the 'records in' value is still zero" is in
>>>>>>>> the top
>>>>>>>> > > three
>>>>>>>> > > >>>>>>>>> support
>>>>>>>> > > >>>>>>>>>>>>>>> questions I have been asked personally.
>>>>>>>> > > >>>>>>>>>>>>>>> Introspection into "how far is the consumer
>>>>>>>> lagging
>>>>>>>> > behind"
>>>>>>>> > > >>>>> (event
>>>>>>>> > > >>>>>>>>>>>> time
>>>>>>>> > > >>>>>>>>>>>>>>> fetch latency) came up many times as well.
>>>>>>>> > > >>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>> So big +1 to solving this problem.
>>>>>>>> > > >>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>> About the exact design - I would try to go for
>>>>>>>> the
>>>>>>>> > > following
>>>>>>>> > > >>>>>>>>>>>> properties:
>>>>>>>> > > >>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>> - keep complexity of of connectors. Ideally the
>>>>>>>> metrics
>>>>>>>> > > >> handler
>>>>>>>> > > >>>>>>> has
>>>>>>>> > > >>>>>>>>> a
>>>>>>>> > > >>>>>>>>>>>>>>> single onRecord(numBytes, eventTime) method or
>>>>>>>> so, and
>>>>>>>> > > >>>>> everything
>>>>>>>> > > >>>>>>>>>>>> else is
>>>>>>>> > > >>>>>>>>>>>>>>> internal to the handler. That makes it dead
>>>>>>>> simple for
>>>>>>>> > the
>>>>>>>> > > >>>>>>>>> connector.
>>>>>>>> > > >>>>>>>>>>>> We
>>>>>>>> > > >>>>>>>>>>>>>>> can also think of an extensive scheme for
>>>>>>>> connector
>>>>>>>> > > specific
>>>>>>>> > > >>>>>>>>> metrics.
>>>>>>>> > > >>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>> - make it configurable on the job it cluster
>>>>>>>> level which
>>>>>>>> > > >>>>> metrics
>>>>>>>> > > >>>>>>> the
>>>>>>>> > > >>>>>>>>>>>>>>> handler internally creates when that method is
>>>>>>>> invoked.
>>>>>>>> > > >>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>> What do you think?
>>>>>>>> > > >>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>> Best,
>>>>>>>> > > >>>>>>>>>>>>>>> Stephan
>>>>>>>> > > >>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>> On Thu, Mar 21, 2019 at 10:42 AM Chesnay
>>>>>>>> Schepler <
>>>>>>>> > > >>>>>>>>> chesnay@apache.org
>>>>>>>> > > >>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>> wrote:
>>>>>>>> > > >>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>> As I said before, I believe this to be
>>>>>>>> over-engineered
>>>>>>>> > and
>>>>>>>> > > >>>>> have
>>>>>>>> > > >>>>>>> no
>>>>>>>> > > >>>>>>>>>>>>>>>> interest in this implementation.
>>>>>>>> > > >>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>> There are conceptual issues like defining a
>>>>>>>> duplicate
>>>>>>>> > > >>>>>>>>>>>>>> numBytesIn(PerSec)
>>>>>>>> > > >>>>>>>>>>>>>>>> metric that already exists for each operator.
>>>>>>>> > > >>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>> On 21.03.2019 06:13, Becket Qin wrote:
>>>>>>>> > > >>>>>>>>>>>>>>>>> A few updates to the thread. I uploaded a
>>>>>>>> patch[1] as a
>>>>>>>> > > >>>>> complete
>>>>>>>> > > >>>>>>>>>>>>>>>>> example of how users can use the metrics in
>>>>>>>> the future.
>>>>>>>> > > >>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>> Some thoughts below after taking a look at the
>>>>>>>> > > >>>>>>> AbstractMetricGroup
>>>>>>>> > > >>>>>>>>>>>>>> and
>>>>>>>> > > >>>>>>>>>>>>>>>>> its subclasses.
>>>>>>>> > > >>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>> This patch intends to provide convenience for
>>>>>>>> Flink
>>>>>>>> > > >> connector
>>>>>>>> > > >>>>>>>>>>>>>>>>> implementations to follow metrics standards
>>>>>>>> proposed in
>>>>>>>> > > >>>>> FLIP-33.
>>>>>>>> > > >>>>>>>>> It
>>>>>>>> > > >>>>>>>>>>>>>>>>> also try to enhance the metric management in
>>>>>>>> general
>>>>>>>> > way
>>>>>>>> > > to
>>>>>>>> > > >>>>> help
>>>>>>>> > > >>>>>>>>>>>>>> users
>>>>>>>> > > >>>>>>>>>>>>>>>>> with:
>>>>>>>> > > >>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>> 1. metric definition
>>>>>>>> > > >>>>>>>>>>>>>>>>> 2. metric dependencies check
>>>>>>>> > > >>>>>>>>>>>>>>>>> 3. metric validation
>>>>>>>> > > >>>>>>>>>>>>>>>>> 4. metric control (turn on / off particular
>>>>>>>> metrics)
>>>>>>>> > > >>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>> This patch wraps |MetricGroup| to extend the
>>>>>>>> > > functionality
>>>>>>>> > > >> of
>>>>>>>> > > >>>>>>>>>>>>>>>>> |AbstractMetricGroup| and its subclasses. The
>>>>>>>> > > >>>>>>>>>>>>>>>>> |AbstractMetricGroup| mainly focus on the
>>>>>>>> metric group
>>>>>>>> > > >>>>>>> hierarchy,
>>>>>>>> > > >>>>>>>>>>>> but
>>>>>>>> > > >>>>>>>>>>>>>>>>> does not really manage the metrics other than
>>>>>>>> keeping
>>>>>>>> > > them
>>>>>>>> > > >>>>> in a
>>>>>>>> > > >>>>>>>>> Map.
>>>>>>>> > > >>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>> Ideally we should only have one entry point
>>>>>>>> for the
>>>>>>>> > > >> metrics.
>>>>>>>> > > >>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>> Right now the entry point is
>>>>>>>> |AbstractMetricGroup|.
>>>>>>>> > > >> However,
>>>>>>>> > > >>>>>>>>> besides
>>>>>>>> > > >>>>>>>>>>>>>>>>> the missing functionality mentioned above,
>>>>>>>> > > >>>>> |AbstractMetricGroup|
>>>>>>>> > > >>>>>>>>>>>>>> seems
>>>>>>>> > > >>>>>>>>>>>>>>>>> deeply rooted in Flink runtime. We could
>>>>>>>> extract it out
>>>>>>>> > > to
>>>>>>>> > > >>>>>>>>>>>>>>>>> flink-metrics in order to use it for generic
>>>>>>>> purpose.
>>>>>>>> > > There
>>>>>>>> > > >>>>> will
>>>>>>>> > > >>>>>>>>> be
>>>>>>>> > > >>>>>>>>>>>>>>>>> some work, though.
>>>>>>>> > > >>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>> Another approach is to make |AbstractMetrics|
>>>>>>>> in this
>>>>>>>> > > patch
>>>>>>>> > > >>>>> as
>>>>>>>> > > >>>>>>> the
>>>>>>>> > > >>>>>>>>>>>>>>>>> metric entry point. It wraps metric group and
>>>>>>>> provides
>>>>>>>> > > the
>>>>>>>> > > >>>>>>> missing
>>>>>>>> > > >>>>>>>>>>>>>>>>> functionalities. Then we can roll out this
>>>>>>>> pattern to
>>>>>>>> > > >> runtime
>>>>>>>> > > >>>>>>>>>>>>>>>>> components gradually as well.
>>>>>>>> > > >>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>> My first thought is that the latter approach
>>>>>>>> gives a
>>>>>>>> > more
>>>>>>>> > > >>>>> smooth
>>>>>>>> > > >>>>>>>>>>>>>>>>> migration. But I am also OK with doing a
>>>>>>>> refactoring on
>>>>>>>> > > the
>>>>>>>> > > >>>>>>>>>>>>>>>>> |AbstractMetricGroup| family.
>>>>>>>> > > >>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>> Thanks,
>>>>>>>> > > >>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>> Jiangjie (Becket) Qin
>>>>>>>> > > >>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>> [1] https://github.com/becketqin/flink/pull/1
>>>>>>>> > > >>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>> On Mon, Feb 25, 2019 at 2:32 PM Becket Qin <
>>>>>>>> > > >>>>>>> becket.qin@gmail.com
>>>>>>>> > > >>>>>>>>>>>>>>>>> <ma...@gmail.com>> wrote:
>>>>>>>> > > >>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>> Hi Chesnay,
>>>>>>>> > > >>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>> It might be easier to discuss some
>>>>>>>> implementation
>>>>>>>> > details
>>>>>>>> > > >> in
>>>>>>>> > > >>>>>>> the
>>>>>>>> > > >>>>>>>>>>>>>>>>> PR review instead of in the FLIP discussion
>>>>>>>> thread. I
>>>>>>>> > > have
>>>>>>>> > > >> a
>>>>>>>> > > >>>>>>>>>>>>>> patch
>>>>>>>> > > >>>>>>>>>>>>>>>>> for Kafka connectors ready but haven't
>>>>>>>> submitted the PR
>>>>>>>> > > >> yet.
>>>>>>>> > > >>>>>>>>>>>>>>>>> Hopefully that will help explain a bit more.
>>>>>>>> > > >>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>> ** Re: metric type binding
>>>>>>>> > > >>>>>>>>>>>>>>>>> This is a valid point that worths discussing.
>>>>>>>> If I
>>>>>>>> > > >> understand
>>>>>>>> > > >>>>>>>>>>>>>>>>> correctly, there are two points:
>>>>>>>> > > >>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>> 1. Metric type / interface does not matter as
>>>>>>>> long as
>>>>>>>> > the
>>>>>>>> > > >>>>>>> metric
>>>>>>>> > > >>>>>>>>>>>>>>>>> semantic is clearly defined.
>>>>>>>> > > >>>>>>>>>>>>>>>>> Conceptually speaking, I agree that as long
>>>>>>>> as the
>>>>>>>> > metric
>>>>>>>> > > >>>>>>>>>>>>>> semantic
>>>>>>>> > > >>>>>>>>>>>>>>>>> is defined, metric type does not matter. To
>>>>>>>> some
>>>>>>>> > extent,
>>>>>>>> > > >>>>> Gauge
>>>>>>>> > > >>>>>>> /
>>>>>>>> > > >>>>>>>>>>>>>>>>> Counter / Meter / Histogram themselves can be
>>>>>>>> think of
>>>>>>>> > as
>>>>>>>> > > >>>>> some
>>>>>>>> > > >>>>>>>>>>>>>>>>> well-recognized semantics, if you wish. In
>>>>>>>> Flink, these
>>>>>>>> > > >>>>> metric
>>>>>>>> > > >>>>>>>>>>>>>>>>> semantics have their associated interface
>>>>>>>> classes. In
>>>>>>>> > > >>>>> practice,
>>>>>>>> > > >>>>>>>>>>>>>>>>> such semantic to interface binding seems
>>>>>>>> necessary for
>>>>>>>> > > >>>>>>> different
>>>>>>>> > > >>>>>>>>>>>>>>>>> components to communicate. Simply
>>>>>>>> standardize the
>>>>>>>> > > semantic
>>>>>>>> > > >>>>> of
>>>>>>>> > > >>>>>>>>>>>>>> the
>>>>>>>> > > >>>>>>>>>>>>>>>>> connector metrics seems not sufficient for
>>>>>>>> people to
>>>>>>>> > > build
>>>>>>>> > > >>>>>>>>>>>>>>>>> ecosystem on top of. At the end of the day,
>>>>>>>> we still
>>>>>>>> > need
>>>>>>>> > > >> to
>>>>>>>> > > >>>>>>>>> have
>>>>>>>> > > >>>>>>>>>>>>>>>>> some embodiment of the metric semantics that
>>>>>>>> people can
>>>>>>>> > > >>>>> program
>>>>>>>> > > >>>>>>>>>>>>>>>>> against.
>>>>>>>> > > >>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>> 2. Sometimes the same metric semantic can be
>>>>>>>> exposed
>>>>>>>> > > using
>>>>>>>> > > >>>>>>>>>>>>>>>>> different metric types / interfaces.
>>>>>>>> > > >>>>>>>>>>>>>>>>> This is a good point. Counter and
>>>>>>>> Gauge-as-a-Counter
>>>>>>>> > are
>>>>>>>> > > >>>>> pretty
>>>>>>>> > > >>>>>>>>>>>>>>>>> much interchangeable. This is more of a
>>>>>>>> trade-off
>>>>>>>> > between
>>>>>>>> > > >> the
>>>>>>>> > > >>>>>>>>>>>>>> user
>>>>>>>> > > >>>>>>>>>>>>>>>>> experience of metric producers and consumers.
>>>>>>>> The
>>>>>>>> > metric
>>>>>>>> > > >>>>>>>>>>>>>> producers
>>>>>>>> > > >>>>>>>>>>>>>>>>> want to use Counter or Gauge depending on
>>>>>>>> whether the
>>>>>>>> > > >> counter
>>>>>>>> > > >>>>>>> is
>>>>>>>> > > >>>>>>>>>>>>>>>>> already tracked in code, while ideally the
>>>>>>>> metric
>>>>>>>> > > consumers
>>>>>>>> > > >>>>>>> only
>>>>>>>> > > >>>>>>>>>>>>>>>>> want to see a single metric type for each
>>>>>>>> metric. I am
>>>>>>>> > > >>>>> leaning
>>>>>>>> > > >>>>>>>>>>>>>>>>> towards to make the metric producers happy,
>>>>>>>> i.e. allow
>>>>>>>> > > >> Gauge
>>>>>>>> > > >>>>> /
>>>>>>>> > > >>>>>>>>>>>>>>>>> Counter metric type, and the the metric
>>>>>>>> consumers
>>>>>>>> > handle
>>>>>>>> > > >> the
>>>>>>>> > > >>>>>>>>> type
>>>>>>>> > > >>>>>>>>>>>>>>>>> variation. The reason is that in practice,
>>>>>>>> there might
>>>>>>>> > be
>>>>>>>> > > >>>>> more
>>>>>>>> > > >>>>>>>>>>>>>>>>> connector implementations than metric reporter
>>>>>>>> > > >>>>> implementations.
>>>>>>>> > > >>>>>>>>>>>>>> We
>>>>>>>> > > >>>>>>>>>>>>>>>>> could also provide some helper method to
>>>>>>>> facilitate
>>>>>>>> > > reading
>>>>>>>> > > >>>>>>> from
>>>>>>>> > > >>>>>>>>>>>>>>>>> such variable metric type.
>>>>>>>> > > >>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>> Just some quick replies to the comments around
>>>>>>>> > > >> implementation
>>>>>>>> > > >>>>>>>>>>>>>>>> details.
>>>>>>>> > > >>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>> 4) single place where metrics are
>>>>>>>> registered except
>>>>>>>> > > >>>>>>>>>>>>>>>>> connector-specific
>>>>>>>> > > >>>>>>>>>>>>>>>>> ones (which we can't really avoid).
>>>>>>>> > > >>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>> Register connector specific ones in a single
>>>>>>>> place is
>>>>>>>> > > >>>>> actually
>>>>>>>> > > >>>>>>>>>>>>>>>>> something that I want to achieve.
>>>>>>>> > > >>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>> 2) I'm talking about time-series databases
>>>>>>>> like
>>>>>>>> > > >>>>> Prometheus.
>>>>>>>> > > >>>>>>>>>>>>>> We
>>>>>>>> > > >>>>>>>>>>>>>>>>> would
>>>>>>>> > > >>>>>>>>>>>>>>>>> only have a gauge metric exposing the last
>>>>>>>> > > >>>>>>>>> fetchTime/emitTime
>>>>>>>> > > >>>>>>>>>>>>>>>>> that is
>>>>>>>> > > >>>>>>>>>>>>>>>>> regularly reported to the backend
>>>>>>>> (Prometheus),
>>>>>>>> > where a
>>>>>>>> > > >>>>>>> user
>>>>>>>> > > >>>>>>>>>>>>>>>>> could build
>>>>>>>> > > >>>>>>>>>>>>>>>>> a histogram of his choosing when/if he
>>>>>>>> wants it.
>>>>>>>> > > >>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>> Not sure if such downsampling works. As an
>>>>>>>> example, if
>>>>>>>> > a
>>>>>>>> > > >> user
>>>>>>>> > > >>>>>>>>>>>>>>>>> complains that there are some intermittent
>>>>>>>> latency
>>>>>>>> > spikes
>>>>>>>> > > >>>>>>> (maybe
>>>>>>>> > > >>>>>>>>>>>>>> a
>>>>>>>> > > >>>>>>>>>>>>>>>>> few records in 10 seconds) in their
>>>>>>>> processing system.
>>>>>>>> > > >>>>> Having a
>>>>>>>> > > >>>>>>>>>>>>>>>>> Gauge sampling instantaneous latency seems
>>>>>>>> unlikely
>>>>>>>> > > useful.
>>>>>>>> > > >>>>>>>>>>>>>>>>> However by looking at actual 99.9 percentile
>>>>>>>> latency
>>>>>>>> > > might
>>>>>>>> > > >>>>>>> help.
>>>>>>>> > > >>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>> Thanks,
>>>>>>>> > > >>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>> Jiangjie (Becket) Qin
>>>>>>>> > > >>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>> On Fri, Feb 22, 2019 at 9:30 PM Chesnay
>>>>>>>> Schepler
>>>>>>>> > > >>>>>>>>>>>>>>>>> <chesnay@apache.org <mailto:
>>>>>>>> chesnay@apache.org>>
>>>>>>>> > wrote:
>>>>>>>> > > >>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>> Re: over complication of implementation.
>>>>>>>> > > >>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>> I think I get understand better know what
>>>>>>>> you're
>>>>>>>> > > >> shooting
>>>>>>>> > > >>>>>>>>>>>>>> for,
>>>>>>>> > > >>>>>>>>>>>>>>>>> effectively something like the
>>>>>>>> OperatorIOMetricGroup.
>>>>>>>> > > >>>>>>>>>>>>>>>>> But still, re-define
>>>>>>>> setupConnectorMetrics() to
>>>>>>>> > accept
>>>>>>>> > > a
>>>>>>>> > > >>>>>>> set
>>>>>>>> > > >>>>>>>>>>>>>>>>> of flags
>>>>>>>> > > >>>>>>>>>>>>>>>>> for counters/meters(ans _possibly_
>>>>>>>> histograms) along
>>>>>>>> > > >>>>> with a
>>>>>>>> > > >>>>>>>>>>>>>>>>> set of
>>>>>>>> > > >>>>>>>>>>>>>>>>> well-defined Optional<Gauge<?>>, and return
>>>>>>>> the
>>>>>>>> > group.
>>>>>>>> > > >>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>> Solves all issues as far as i can tell:
>>>>>>>> > > >>>>>>>>>>>>>>>>> 1) no metrics must be created manually
>>>>>>>> (except
>>>>>>>> > Gauges,
>>>>>>>> > > >>>>>>> which
>>>>>>>> > > >>>>>>>>>>>>>>> are
>>>>>>>> > > >>>>>>>>>>>>>>>>> effectively just Suppliers and you can't
>>>>>>>> get around
>>>>>>>> > > >>>>> this),
>>>>>>>> > > >>>>>>>>>>>>>>>>> 2) additional metrics can be registered on
>>>>>>>> the
>>>>>>>> > returned
>>>>>>>> > > >>>>>>>>>>>>>> group,
>>>>>>>> > > >>>>>>>>>>>>>>>>> 3) see 1),
>>>>>>>> > > >>>>>>>>>>>>>>>>> 4) single place where metrics are
>>>>>>>> registered except
>>>>>>>> > > >>>>>>>>>>>>>>>>> connector-specific
>>>>>>>> > > >>>>>>>>>>>>>>>>> ones (which we can't really avoid).
>>>>>>>> > > >>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>> Re: Histogram
>>>>>>>> > > >>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>> 1) As an example, whether "numRecordsIn" is
>>>>>>>> exposed
>>>>>>>> > as
>>>>>>>> > > a
>>>>>>>> > > >>>>>>>>>>>>>>>>> Counter or a
>>>>>>>> > > >>>>>>>>>>>>>>>>> Gauge should be irrelevant. So far we're
>>>>>>>> using the
>>>>>>>> > > >> metric
>>>>>>>> > > >>>>>>>>>>>>>> type
>>>>>>>> > > >>>>>>>>>>>>>>>>> that is
>>>>>>>> > > >>>>>>>>>>>>>>>>> the most convenient at exposing a given
>>>>>>>> value. If
>>>>>>>> > there
>>>>>>>> > > >>>>> is
>>>>>>>> > > >>>>>>>>>>>>>>>>> some backing
>>>>>>>> > > >>>>>>>>>>>>>>>>> data-structure that we want to expose some
>>>>>>>> data from
>>>>>>>> > we
>>>>>>>> > > >>>>>>>>>>>>>>>>> typically opt
>>>>>>>> > > >>>>>>>>>>>>>>>>> for a Gauge, as otherwise we're just
>>>>>>>> mucking around
>>>>>>>> > > with
>>>>>>>> > > >>>>>>> the
>>>>>>>> > > >>>>>>>>>>>>>>>>> Meter/Counter API to get it to match.
>>>>>>>> Similarly, if
>>>>>>>> > we
>>>>>>>> > > >>>>> want
>>>>>>>> > > >>>>>>>>>>>>>> to
>>>>>>>> > > >>>>>>>>>>>>>>>>> count
>>>>>>>> > > >>>>>>>>>>>>>>>>> something but no current count exists we
>>>>>>>> typically
>>>>>>>> > > added
>>>>>>>> > > >>>>> a
>>>>>>>> > > >>>>>>>>>>>>>>>>> Counter.
>>>>>>>> > > >>>>>>>>>>>>>>>>> That's why attaching semantics to metric
>>>>>>>> types makes
>>>>>>>> > > >>>>> little
>>>>>>>> > > >>>>>>>>>>>>>>>>> sense (but
>>>>>>>> > > >>>>>>>>>>>>>>>>> unfortunately several reporters already do
>>>>>>>> it); for
>>>>>>>> > > >>>>>>>>>>>>>>>>> counters/meters
>>>>>>>> > > >>>>>>>>>>>>>>>>> certainly, but the majority of metrics are
>>>>>>>> gauges.
>>>>>>>> > > >>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>> 2) I'm talking about time-series databases
>>>>>>>> like
>>>>>>>> > > >>>>> Prometheus.
>>>>>>>> > > >>>>>>>>>>>>>> We
>>>>>>>> > > >>>>>>>>>>>>>>>>> would
>>>>>>>> > > >>>>>>>>>>>>>>>>> only have a gauge metric exposing the last
>>>>>>>> > > >>>>>>>>> fetchTime/emitTime
>>>>>>>> > > >>>>>>>>>>>>>>>>> that is
>>>>>>>> > > >>>>>>>>>>>>>>>>> regularly reported to the backend
>>>>>>>> (Prometheus),
>>>>>>>> > where a
>>>>>>>> > > >>>>>>> user
>>>>>>>> > > >>>>>>>>>>>>>>>>> could build
>>>>>>>> > > >>>>>>>>>>>>>>>>> a histogram of his choosing when/if he
>>>>>>>> wants it.
>>>>>>>> > > >>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>> On 22.02.2019 13:57, Becket Qin wrote:
>>>>>>>> > > >>>>>>>>>>>>>>>>>> Hi Chesnay,
>>>>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>>> Thanks for the explanation.
>>>>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>>> ** Re: FLIP
>>>>>>>> > > >>>>>>>>>>>>>>>>>> I might have misunderstood this, but it
>>>>>>>> seems that
>>>>>>>> > > "major
>>>>>>>> > > >>>>>>>>>>>>>>>>> changes" are well
>>>>>>>> > > >>>>>>>>>>>>>>>>>> defined in FLIP. The full contents is
>>>>>>>> following:
>>>>>>>> > > >>>>>>>>>>>>>>>>>> What is considered a "major change" that
>>>>>>>> needs a FLIP?
>>>>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>>> Any of the following should be considered a
>>>>>>>> major
>>>>>>>> > > change:
>>>>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>>> - Any major new feature, subsystem, or piece
>>>>>>>> of
>>>>>>>> > > >>>>>>>>>>>>>>>>> functionality
>>>>>>>> > > >>>>>>>>>>>>>>>>>> - *Any change that impacts the public
>>>>>>>> interfaces of
>>>>>>>> > the
>>>>>>>> > > >>>>>>>>>>>>>>>>> project*
>>>>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>>> What are the "public interfaces" of the
>>>>>>>> project?
>>>>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>>> *All of the following are public interfaces
>>>>>>>> *that
>>>>>>>> > people
>>>>>>>> > > >>>>>>>>>>>>>>>>> build around:
>>>>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>>> - DataStream and DataSet API, including
>>>>>>>> classes
>>>>>>>> > related
>>>>>>>> > > >>>>>>>>>>>>>>>>> to that, such as
>>>>>>>> > > >>>>>>>>>>>>>>>>>> StreamExecutionEnvironment
>>>>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>>> - Classes marked with the @Public annotation
>>>>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>>> - On-disk binary formats, such as
>>>>>>>> > > >>>>>>>>>>>>>> checkpoints/savepoints
>>>>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>>> - User-facing scripts/command-line tools,
>>>>>>>> i.e.
>>>>>>>> > > >>>>>>>>>>>>>>>>> bin/flink, Yarn scripts,
>>>>>>>> > > >>>>>>>>>>>>>>>>>> Mesos scripts
>>>>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>>> - Configuration settings
>>>>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>>> - *Exposed monitoring information*
>>>>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>>> So any monitoring information change is
>>>>>>>> considered as
>>>>>>>> > > >>>>>>>>>>>>>> public
>>>>>>>> > > >>>>>>>>>>>>>>>>> interface, and
>>>>>>>> > > >>>>>>>>>>>>>>>>>> any public interface change is considered as
>>>>>>>> a "major
>>>>>>>> > > >>>>>>>>>>>>>>> change".
>>>>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>>> ** Re: over complication of implementation.
>>>>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>>> Although this is more of implementation
>>>>>>>> details that
>>>>>>>> > is
>>>>>>>> > > >> not
>>>>>>>> > > >>>>>>>>>>>>>>>>> covered by the
>>>>>>>> > > >>>>>>>>>>>>>>>>>> FLIP. But it may be worth discussing.
>>>>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>>> First of all, I completely agree that we
>>>>>>>> should use
>>>>>>>> > the
>>>>>>>> > > >>>>>>>>>>>>>>>>> simplest way to
>>>>>>>> > > >>>>>>>>>>>>>>>>>> achieve our goal. To me the goal is the
>>>>>>>> following:
>>>>>>>> > > >>>>>>>>>>>>>>>>>> 1. Clear connector conventions and
>>>>>>>> interfaces.
>>>>>>>> > > >>>>>>>>>>>>>>>>>> 2. The easiness of creating a connector.
>>>>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>>> Both of them are important to the prosperity
>>>>>>>> of the
>>>>>>>> > > >>>>>>>>>>>>>>>>> connector ecosystem. So
>>>>>>>> > > >>>>>>>>>>>>>>>>>> I'd rather abstract as much as possible on
>>>>>>>> our side to
>>>>>>>> > > >> make
>>>>>>>> > > >>>>>>>>>>>>>>>>> the connector
>>>>>>>> > > >>>>>>>>>>>>>>>>>> developer's work lighter. Given this goal, a
>>>>>>>> static
>>>>>>>> > util
>>>>>>>> > > >>>>>>>>>>>>>>>>> method approach
>>>>>>>> > > >>>>>>>>>>>>>>>>>> might have a few drawbacks:
>>>>>>>> > > >>>>>>>>>>>>>>>>>> 1. Users still have to construct the metrics
>>>>>>>> by
>>>>>>>> > > >> themselves.
>>>>>>>> > > >>>>>>>>>>>>>>>>> (And note that
>>>>>>>> > > >>>>>>>>>>>>>>>>>> this might be erroneous by itself. For
>>>>>>>> example, a
>>>>>>>> > > customer
>>>>>>>> > > >>>>>>>>>>>>>>>>> wrapper around
>>>>>>>> > > >>>>>>>>>>>>>>>>>> dropwizard meter maybe used instead of
>>>>>>>> MeterView).
>>>>>>>> > > >>>>>>>>>>>>>>>>>> 2. When connector specific metrics are
>>>>>>>> added, it is
>>>>>>>> > > >>>>>>>>>>>>>>>>> difficult to enforce
>>>>>>>> > > >>>>>>>>>>>>>>>>>> the scope to be the same as standard metrics.
>>>>>>>> > > >>>>>>>>>>>>>>>>>> 3. It seems that a method proliferation is
>>>>>>>> inevitable
>>>>>>>> > if
>>>>>>>> > > >> we
>>>>>>>> > > >>>>>>>>>>>>>>>>> want to apply
>>>>>>>> > > >>>>>>>>>>>>>>>>>> sanity checks. e.g. The metric of numBytesIn
>>>>>>>> was not
>>>>>>>> > > >>>>>>>>>>>>>>>>> registered for a meter.
>>>>>>>> > > >>>>>>>>>>>>>>>>>> 4. Metrics are still defined in random
>>>>>>>> places and hard
>>>>>>>> > > to
>>>>>>>> > > >>>>>>>>>>>>>>>> track.
>>>>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>>> The current PR I had was inspired by the
>>>>>>>> Config system
>>>>>>>> > > in
>>>>>>>> > > >>>>>>>>>>>>>>>>> Kafka, which I
>>>>>>>> > > >>>>>>>>>>>>>>>>>> found pretty handy. In fact it is not only
>>>>>>>> used by
>>>>>>>> > Kafka
>>>>>>>> > > >>>>>>>>>>>>>>>>> itself but even
>>>>>>>> > > >>>>>>>>>>>>>>>>>> some other projects that depend on Kafka. I
>>>>>>>> am not
>>>>>>>> > > saying
>>>>>>>> > > >>>>>>>>>>>>>>>>> this approach is
>>>>>>>> > > >>>>>>>>>>>>>>>>>> perfect. But I think it worths to save the
>>>>>>>> work for
>>>>>>>> > > >>>>>>>>>>>>>>>>> connector writers and
>>>>>>>> > > >>>>>>>>>>>>>>>>>> encourage more systematic implementation.
>>>>>>>> That being
>>>>>>>> > > said,
>>>>>>>> > > >>>>>>>>>>>>>> I
>>>>>>>> > > >>>>>>>>>>>>>>>>> am fully open
>>>>>>>> > > >>>>>>>>>>>>>>>>>> to suggestions.
>>>>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>>> Re: Histogram
>>>>>>>> > > >>>>>>>>>>>>>>>>>> I think there are two orthogonal questions
>>>>>>>> around
>>>>>>>> > those
>>>>>>>> > > >>>>>>>>>>>>>>>> metrics:
>>>>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>>> 1. Regardless of the metric type, by just
>>>>>>>> looking at
>>>>>>>> > the
>>>>>>>> > > >>>>>>>>>>>>>>>>> meaning of a
>>>>>>>> > > >>>>>>>>>>>>>>>>>> metric, is generic to all connectors? If the
>>>>>>>> answer is
>>>>>>>> > > >> yes,
>>>>>>>> > > >>>>>>>>>>>>>>>>> we should
>>>>>>>> > > >>>>>>>>>>>>>>>>>> include the metric into the convention. No
>>>>>>>> matter
>>>>>>>> > > whether
>>>>>>>> > > >>>>>>>>>>>>>> we
>>>>>>>> > > >>>>>>>>>>>>>>>>> include it
>>>>>>>> > > >>>>>>>>>>>>>>>>>> into the convention or not, some connector
>>>>>>>> > > implementations
>>>>>>>> > > >>>>>>>>>>>>>>>>> will emit such
>>>>>>>> > > >>>>>>>>>>>>>>>>>> metric. It is better to have a convention
>>>>>>>> than letting
>>>>>>>> > > >> each
>>>>>>>> > > >>>>>>>>>>>>>>>>> connector do
>>>>>>>> > > >>>>>>>>>>>>>>>>>> random things.
>>>>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>>> 2. If a standard metric is a histogram, what
>>>>>>>> should we
>>>>>>>> > > do?
>>>>>>>> > > >>>>>>>>>>>>>>>>>> I agree that we should make it clear that
>>>>>>>> using
>>>>>>>> > > histograms
>>>>>>>> > > >>>>>>>>>>>>>>>>> will have
>>>>>>>> > > >>>>>>>>>>>>>>>>>> performance risk. But I do see histogram is
>>>>>>>> useful in
>>>>>>>> > > some
>>>>>>>> > > >>>>>>>>>>>>>>>>> fine-granularity
>>>>>>>> > > >>>>>>>>>>>>>>>>>> debugging where one do not have the luxury
>>>>>>>> to stop the
>>>>>>>> > > >>>>>>>>>>>>>>>>> system and inject
>>>>>>>> > > >>>>>>>>>>>>>>>>>> more inspection code. So the workaround I am
>>>>>>>> thinking
>>>>>>>> > is
>>>>>>>> > > >> to
>>>>>>>> > > >>>>>>>>>>>>>>>>> provide some
>>>>>>>> > > >>>>>>>>>>>>>>>>>> implementation suggestions. Assume later on
>>>>>>>> we have a
>>>>>>>> > > >>>>>>>>>>>>>>>>> mechanism of
>>>>>>>> > > >>>>>>>>>>>>>>>>>> selective metrics. In the abstract metrics
>>>>>>>> class we
>>>>>>>> > can
>>>>>>>> > > >>>>>>>>>>>>>>>>> disable those
>>>>>>>> > > >>>>>>>>>>>>>>>>>> metrics by default individual connector
>>>>>>>> writers does
>>>>>>>> > not
>>>>>>>> > > >>>>>>>>>>>>>>>>> have to do
>>>>>>>> > > >>>>>>>>>>>>>>>>>> anything (this is another advantage of
>>>>>>>> having an
>>>>>>>> > > >>>>>>>>>>>>>>>>> AbstractMetrics instead of
>>>>>>>> > > >>>>>>>>>>>>>>>>>> static util methods.)
>>>>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>>> I am not sure I fully understand the
>>>>>>>> histogram in the
>>>>>>>> > > >>>>>>>>>>>>>>>>> backend approach. Can
>>>>>>>> > > >>>>>>>>>>>>>>>>>> you explain a bit more? Do you mean emitting
>>>>>>>> the raw
>>>>>>>> > > data,
>>>>>>>> > > >>>>>>>>>>>>>>>>> e.g. fetchTime
>>>>>>>> > > >>>>>>>>>>>>>>>>>> and emitTime with each record and let the
>>>>>>>> histogram
>>>>>>>> > > >>>>>>>>>>>>>>>>> computation happen in
>>>>>>>> > > >>>>>>>>>>>>>>>>>> the background? Or let the processing thread
>>>>>>>> putting
>>>>>>>> > the
>>>>>>>> > > >>>>>>>>>>>>>>>>> values into a
>>>>>>>> > > >>>>>>>>>>>>>>>>>> queue and have a separate thread polling
>>>>>>>> from the
>>>>>>>> > queue
>>>>>>>> > > >> and
>>>>>>>> > > >>>>>>>>>>>>>>>>> add them into
>>>>>>>> > > >>>>>>>>>>>>>>>>>> the histogram?
>>>>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>>> Thanks,
>>>>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>>> Jiangjie (Becket) Qin
>>>>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>>> On Fri, Feb 22, 2019 at 4:34 PM Chesnay
>>>>>>>> Schepler
>>>>>>>> > > >>>>>>>>>>>>>>>>> <chesnay@apache.org <mailto:
>>>>>>>> chesnay@apache.org>>
>>>>>>>> > > wrote:
>>>>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>>>> Re: Flip
>>>>>>>> > > >>>>>>>>>>>>>>>>>>> The very first line under both the main
>>>>>>>> header and
>>>>>>>> > > >> Purpose
>>>>>>>> > > >>>>>>>>>>>>>>>>> section
>>>>>>>> > > >>>>>>>>>>>>>>>>>>> describe Flips as "major changes", which
>>>>>>>> this isn't.
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>>>> Re: complication
>>>>>>>> > > >>>>>>>>>>>>>>>>>>> I'm not arguing against standardization,
>>>>>>>> but again an
>>>>>>>> > > >>>>>>>>>>>>>>>>> over-complicated
>>>>>>>> > > >>>>>>>>>>>>>>>>>>> implementation when a static utility method
>>>>>>>> would be
>>>>>>>> > > >>>>>>>>>>>>>>>>> sufficient.
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>>>> public static void setupConnectorMetrics(
>>>>>>>> > > >>>>>>>>>>>>>>>>>>> MetricGroup operatorMetricGroup,
>>>>>>>> > > >>>>>>>>>>>>>>>>>>> String connectorName,
>>>>>>>> > > >>>>>>>>>>>>>>>>>>> Optional<Gauge<Long>> numRecordsIn,
>>>>>>>> > > >>>>>>>>>>>>>>>>>>> ...)
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>>>> This gives you all you need:
>>>>>>>> > > >>>>>>>>>>>>>>>>>>> * a well-defined set of metrics for a
>>>>>>>> connector to
>>>>>>>> > > opt-in
>>>>>>>> > > >>>>>>>>>>>>>>>>>>> * standardized naming schemes for scope and
>>>>>>>> > individual
>>>>>>>> > > >>>>>>>>>>>>>>> metrics
>>>>>>>> > > >>>>>>>>>>>>>>>>>>> * standardize metric types (although
>>>>>>>> personally I'm
>>>>>>>> > not
>>>>>>>> > > >>>>>>>>>>>>>>>>> interested in that
>>>>>>>> > > >>>>>>>>>>>>>>>>>>> since metric types should be considered
>>>>>>>> syntactic
>>>>>>>> > > sugar)
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>>>> Re: Configurable Histogram
>>>>>>>> > > >>>>>>>>>>>>>>>>>>> If anything they _must_ be turned off by
>>>>>>>> default, but
>>>>>>>> > > the
>>>>>>>> > > >>>>>>>>>>>>>>>>> metric system is
>>>>>>>> > > >>>>>>>>>>>>>>>>>>> already exposing so many options that I'm
>>>>>>>> not too
>>>>>>>> > keen
>>>>>>>> > > on
>>>>>>>> > > >>>>>>>>>>>>>>>>> adding even more.
>>>>>>>> > > >>>>>>>>>>>>>>>>>>> You have also only addressed my first
>>>>>>>> argument
>>>>>>>> > against
>>>>>>>> > > >>>>>>>>>>>>>>>>> histograms
>>>>>>>> > > >>>>>>>>>>>>>>>>>>> (performance), the second one still stands
>>>>>>>> (calculate
>>>>>>>> > > >>>>>>>>>>>>>>>>> histogram in metric
>>>>>>>> > > >>>>>>>>>>>>>>>>>>> backends instead).
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>>>> On 21.02.2019 16:27, Becket Qin wrote:
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>> Hi Chesnay,
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>> Thanks for the comments. I think this is
>>>>>>>> worthy of a
>>>>>>>> > > >> FLIP
>>>>>>>> > > >>>>>>>>>>>>>>>>> because it is
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>> public API. According to the FLIP
>>>>>>>> description a FlIP
>>>>>>>> > > is
>>>>>>>> > > >>>>>>>>>>>>>>>>> required in case
>>>>>>>> > > >>>>>>>>>>>>>>>>>>> of:
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>> - Any change that impacts the public
>>>>>>>> interfaces of
>>>>>>>> > > >>>>>>>>>>>>>>>>> the project
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>> and the following entry is found in the
>>>>>>>> definition
>>>>>>>> > of
>>>>>>>> > > >>>>>>>>>>>>>>>>> "public interface".
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>> - Exposed monitoring information
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>> Metrics are critical to any production
>>>>>>>> system. So a
>>>>>>>> > > >> clear
>>>>>>>> > > >>>>>>>>>>>>>>>>> metric
>>>>>>>> > > >>>>>>>>>>>>>>>>>>> definition
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>> is important for any serious users. For an
>>>>>>>> > > organization
>>>>>>>> > > >>>>>>>>>>>>>>>>> with large Flink
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>> installation, change in metrics means
>>>>>>>> great amount
>>>>>>>> > of
>>>>>>>> > > >>>>>>>>>>>>>>>>> work. So such
>>>>>>>> > > >>>>>>>>>>>>>>>>>>> changes
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>> do need to be fully discussed and
>>>>>>>> documented.
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>> ** Re: Histogram.
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>> We can discuss whether there is a better
>>>>>>>> way to
>>>>>>>> > expose
>>>>>>>> > > >>>>>>>>>>>>>>>>> metrics that are
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>> suitable for histograms. My
>>>>>>>> micro-benchmark on
>>>>>>>> > various
>>>>>>>> > > >>>>>>>>>>>>>>>>> histogram
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>> implementations also indicates that they
>>>>>>>> are
>>>>>>>> > > >>>>>>>>>>>>>> significantly
>>>>>>>> > > >>>>>>>>>>>>>>>>> slower than
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>> other metric types. But I don't think that
>>>>>>>> means
>>>>>>>> > never
>>>>>>>> > > >>>>>>>>>>>>>> use
>>>>>>>> > > >>>>>>>>>>>>>>>>> histogram, but
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>> means use it with caution. For example, we
>>>>>>>> can
>>>>>>>> > suggest
>>>>>>>> > > >>>>>>>>>>>>>> the
>>>>>>>> > > >>>>>>>>>>>>>>>>>>> implementations
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>> to turn them off by default and only turn
>>>>>>>> it on for
>>>>>>>> > a
>>>>>>>> > > >>>>>>>>>>>>>>>>> small amount of
>>>>>>>> > > >>>>>>>>>>>>>>>>>>> time
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>> when performing some micro-debugging.
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>> ** Re: complication:
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>> Connector conventions are essential for
>>>>>>>> Flink
>>>>>>>> > > ecosystem.
>>>>>>>> > > >>>>>>>>>>>>>>>>> Flink connectors
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>> pool is probably the most important part
>>>>>>>> of Flink,
>>>>>>>> > > just
>>>>>>>> > > >>>>>>>>>>>>>>>>> like any other
>>>>>>>> > > >>>>>>>>>>>>>>>>>>> data
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>> system. Clear conventions of connectors
>>>>>>>> will help
>>>>>>>> > > build
>>>>>>>> > > >>>>>>>>>>>>>>>>> Flink ecosystem
>>>>>>>> > > >>>>>>>>>>>>>>>>>>> in
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>> a more organic way.
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>> Take the metrics convention as an example,
>>>>>>>> imagine
>>>>>>>> > > >>>>>>>>>>>>>> someone
>>>>>>>> > > >>>>>>>>>>>>>>>>> has developed
>>>>>>>> > > >>>>>>>>>>>>>>>>>>> a
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>> Flink connector for System foo, and another
>>>>>>>> > developer
>>>>>>>> > > >> may
>>>>>>>> > > >>>>>>>>>>>>>>>>> have developed
>>>>>>>> > > >>>>>>>>>>>>>>>>>>> a
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>> monitoring and diagnostic framework for
>>>>>>>> Flink which
>>>>>>>> > > >>>>>>>>>>>>>>>>> analyzes the Flink
>>>>>>>> > > >>>>>>>>>>>>>>>>>>> job
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>> performance based on metrics. With a clear
>>>>>>>> metric
>>>>>>>> > > >>>>>>>>>>>>>>>>> convention, those two
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>> projects could be developed independently.
>>>>>>>> Once
>>>>>>>> > users
>>>>>>>> > > >> put
>>>>>>>> > > >>>>>>>>>>>>>>>>> them together,
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>> it would work without additional
>>>>>>>> modifications. This
>>>>>>>> > > >>>>>>>>>>>>>>>>> cannot be easily
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>> achieved by just defining a few constants.
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>> ** Re: selective metrics:
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>> Sure, we can discuss that in a separate
>>>>>>>> thread.
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>> @Dawid
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>> ** Re: latency / fetchedLatency
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>> The primary purpose of establish such a
>>>>>>>> convention
>>>>>>>> > is
>>>>>>>> > > to
>>>>>>>> > > >>>>>>>>>>>>>>>>> help developers
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>> write connectors in a more compatible way.
>>>>>>>> The
>>>>>>>> > > >> convention
>>>>>>>> > > >>>>>>>>>>>>>>>>> is supposed to
>>>>>>>> > > >>>>>>>>>>>>>>>>>>> be
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>> defined more proactively. So when look at
>>>>>>>> the
>>>>>>>> > > >> convention,
>>>>>>>> > > >>>>>>>>>>>>>>>>> it seems more
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>> important to see if the concept is
>>>>>>>> applicable to
>>>>>>>> > > >>>>>>>>>>>>>>>>> connectors in general.
>>>>>>>> > > >>>>>>>>>>>>>>>>>>> It
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>> might be true so far only Kafka connector
>>>>>>>> reports
>>>>>>>> > > >>>>>>>>>>>>>> latency.
>>>>>>>> > > >>>>>>>>>>>>>>>>> But there
>>>>>>>> > > >>>>>>>>>>>>>>>>>>> might
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>> be hundreds of other connector
>>>>>>>> implementations in
>>>>>>>> > the
>>>>>>>> > > >>>>>>>>>>>>>>>>> Flink ecosystem,
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>> though not in the Flink repo, and some of
>>>>>>>> them also
>>>>>>>> > > >> emits
>>>>>>>> > > >>>>>>>>>>>>>>>>> latency. I
>>>>>>>> > > >>>>>>>>>>>>>>>>>>> think
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>> a lot of other sources actually also has
>>>>>>>> an append
>>>>>>>> > > >>>>>>>>>>>>>>>>> timestamp. e.g.
>>>>>>>> > > >>>>>>>>>>>>>>>>>>> database
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>> bin logs and some K-V stores. So I
>>>>>>>> wouldn't be
>>>>>>>> > > surprised
>>>>>>>> > > >>>>>>>>>>>>>>>>> if some database
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>> connector can also emit latency metrics.
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>> Thanks,
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>> Jiangjie (Becket) Qin
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>> On Thu, Feb 21, 2019 at 10:14 PM Chesnay
>>>>>>>> Schepler
>>>>>>>> > > >>>>>>>>>>>>>>>>> <chesnay@apache.org <mailto:
>>>>>>>> chesnay@apache.org>>
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>> wrote:
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>> Regarding 2) It doesn't make sense to
>>>>>>>> investigate
>>>>>>>> > > this
>>>>>>>> > > >>>>>>>>>>>>>> as
>>>>>>>> > > >>>>>>>>>>>>>>>>> part of this
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>> FLIP. This is something that could be of
>>>>>>>> interest
>>>>>>>> > for
>>>>>>>> > > >>>>>>>>>>>>>> the
>>>>>>>> > > >>>>>>>>>>>>>>>>> entire metric
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>> system, and should be designed for as
>>>>>>>> such.
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>> Regarding the proposal as a whole:
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>> Histogram metrics shall not be added to
>>>>>>>> the core of
>>>>>>>> > > >>>>>>>>>>>>>>>>> Flink. They are
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>> significantly more expensive than other
>>>>>>>> metrics,
>>>>>>>> > and
>>>>>>>> > > >>>>>>>>>>>>>>>>> calculating
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>> histograms in the application is regarded
>>>>>>>> as an
>>>>>>>> > > >>>>>>>>>>>>>>>>> anti-pattern by several
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>> metric backends, who instead recommend to
>>>>>>>> expose
>>>>>>>> > the
>>>>>>>> > > >> raw
>>>>>>>> > > >>>>>>>>>>>>>>>>> data and
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>> calculate the histogram in the backend.
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>> Second, this seems overly complicated.
>>>>>>>> Given that
>>>>>>>> > we
>>>>>>>> > > >>>>>>>>>>>>>>>>> already established
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>> that not all connectors will export all
>>>>>>>> metrics we
>>>>>>>> > > are
>>>>>>>> > > >>>>>>>>>>>>>>>>> effectively
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>> reducing this down to a consistent naming
>>>>>>>> scheme.
>>>>>>>> > We
>>>>>>>> > > >>>>>>>>>>>>>>>>> don't need anything
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>> sophisticated for that; basically just a
>>>>>>>> few
>>>>>>>> > > constants
>>>>>>>> > > >>>>>>>>>>>>>>>>> that all
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>> connectors use.
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>> I'm not convinced that this is worthy of
>>>>>>>> a FLIP.
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>> On 21.02.2019 14:26, Dawid Wysakowicz
>>>>>>>> wrote:
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>> Hi,
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>> Ad 1. In general I undestand and I
>>>>>>>> agree. But
>>>>>>>> > those
>>>>>>>> > > >>>>>>>>>>>>>>>>> particular metrics
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>> (latency, fetchLatency), right now would
>>>>>>>> only be
>>>>>>>> > > >>>>>>>>>>>>>>>>> reported if user uses
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>> KafkaConsumer with internal
>>>>>>>> timestampAssigner with
>>>>>>>> > > >>>>>>>>>>>>>>>>> StreamCharacteristic
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>> set to EventTime, right? That sounds
>>>>>>>> like a very
>>>>>>>> > > >>>>>>>>>>>>>>>>> specific case. I am
>>>>>>>> > > >>>>>>>>>>>>>>>>>>> not
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>> sure if we should introduce a generic
>>>>>>>> metric that
>>>>>>>> > > will
>>>>>>>> > > >>>>>>>>>>>>>> be
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>> disabled/absent for most of
>>>>>>>> implementations.
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>> Ad.2 That sounds like an orthogonal
>>>>>>>> issue, that
>>>>>>>> > > might
>>>>>>>> > > >>>>>>>>>>>>>>>>> make sense to
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>> investigate in the future.
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>> Best,
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>> Dawid
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>> On 21/02/2019 13:20, Becket Qin wrote:
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>> Hi Dawid,
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>> Thanks for the feedback. That makes
>>>>>>>> sense to me.
>>>>>>>> > > >> There
>>>>>>>> > > >>>>>>>>>>>>>>>>> are two cases
>>>>>>>> > > >>>>>>>>>>>>>>>>>>> to
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>> be
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>> addressed.
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>> 1. The metrics are supposed to be a
>>>>>>>> guidance. It
>>>>>>>> > is
>>>>>>>> > > >>>>>>>>>>>>>>>>> likely that a
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>> connector
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>> only supports some but not all of the
>>>>>>>> metrics. In
>>>>>>>> > > >> that
>>>>>>>> > > >>>>>>>>>>>>>>>>> case, each
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>> connector
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>> implementation should have the freedom
>>>>>>>> to decide
>>>>>>>> > > >> which
>>>>>>>> > > >>>>>>>>>>>>>>>>> metrics are
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>> reported. For the metrics that are
>>>>>>>> supported, the
>>>>>>>> > > >>>>>>>>>>>>>>>>> guidance should be
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>> followed.
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>> 2. Sometimes users may want to disable
>>>>>>>> certain
>>>>>>>> > > >> metrics
>>>>>>>> > > >>>>>>>>>>>>>>>>> for some reason
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>> (e.g. performance / reprocessing of
>>>>>>>> data). A
>>>>>>>> > > generic
>>>>>>>> > > >>>>>>>>>>>>>>>>> mechanism should
>>>>>>>> > > >>>>>>>>>>>>>>>>>>> be
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>> provided to allow user choose which
>>>>>>>> metrics are
>>>>>>>> > > >>>>>>>>>>>>>>>>> reported. This
>>>>>>>> > > >>>>>>>>>>>>>>>>>>> mechanism
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>> should also be honored by the connector
>>>>>>>> > > >>>>>>>>>>>>>> implementations.
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>> Does this sound reasonable to you?
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>> Thanks,
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>> Jiangjie (Becket) Qin
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>> On Thu, Feb 21, 2019 at 4:22 PM Dawid
>>>>>>>> Wysakowicz
>>>>>>>> > <
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>> dwysakowicz@apache.org <mailto:
>>>>>>>> > > dwysakowicz@apache.org
>>>>>>>> > > >>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>> wrote:
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> Hi,
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> Generally I like the idea of having a
>>>>>>>> unified,
>>>>>>>> > > >>>>>>>>>>>>>>>>> standard set of
>>>>>>>> > > >>>>>>>>>>>>>>>>>>> metrics
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>> for
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> all connectors. I have some slight
>>>>>>>> concerns
>>>>>>>> > about
>>>>>>>> > > >>>>>>>>>>>>>>>>> fetchLatency and
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> latency though. They are computed
>>>>>>>> based on
>>>>>>>> > > EventTime
>>>>>>>> > > >>>>>>>>>>>>>>>>> which is not a
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>> purely
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> technical feature. It depends often on
>>>>>>>> some
>>>>>>>> > > business
>>>>>>>> > > >>>>>>>>>>>>>>>>> logic, might be
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>> absent
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> or defined after source. Those metrics
>>>>>>>> could
>>>>>>>> > also
>>>>>>>> > > >>>>>>>>>>>>>>>>> behave in a weird
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>> way in
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> case of replaying backlog. Therefore I
>>>>>>>> am not
>>>>>>>> > sure
>>>>>>>> > > >> if
>>>>>>>> > > >>>>>>>>>>>>>>>>> we should
>>>>>>>> > > >>>>>>>>>>>>>>>>>>> include
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> those metrics by default. Maybe we
>>>>>>>> could at
>>>>>>>> > least
>>>>>>>> > > >>>>>>>>>>>>>>>>> introduce a feature
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> switch for them? What do you think?
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> Best,
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> Dawid
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> On 21/02/2019 03:13, Becket Qin wrote:
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> Bump. If there is no objections to the
>>>>>>>> proposed
>>>>>>>> > > >>>>>>>>>>>>>>>>> metrics. I'll start a
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> voting thread later toady.
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> Thanks,
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> Jiangjie (Becket) Qin
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> On Mon, Feb 11, 2019 at 8:17 PM Becket
>>>>>>>> Qin
>>>>>>>> > > >>>>>>>>>>>>>>>>> <becket.qin@gmail.com <mailto:
>>>>>>>> becket.qin@gmail.com>>
>>>>>>>> > <
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>> becket.qin@gmail.com <mailto:
>>>>>>>> becket.qin@gmail.com
>>>>>>>> > >>
>>>>>>>> > > >>>>>>>>>>>>>>> wrote:
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> Hi folks,
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> I would like to start the FLIP
>>>>>>>> discussion thread
>>>>>>>> > > >>>>>>>>>>>>>> about
>>>>>>>> > > >>>>>>>>>>>>>>>>> standardize
>>>>>>>> > > >>>>>>>>>>>>>>>>>>> the
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> connector metrics.
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> In short, we would like to provide a
>>>>>>>> convention
>>>>>>>> > of
>>>>>>>> > > >>>>>>>>>>>>>>>>> Flink connector
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> metrics. It will help simplify the
>>>>>>>> monitoring
>>>>>>>> > and
>>>>>>>> > > >>>>>>>>>>>>>>>>> alerting on Flink
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>> jobs.
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> The FLIP link is following:
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>
>>>>>>>> > > >>>>>>>
>>>>>>>> > > >>>>>
>>>>>>>> > > >>
>>>>>>>> > >
>>>>>>>> >
>>>>>>>> https://cwiki.apache.org/confluence/display/FLINK/FLIP-33%3A+Standardize+Connector+Metrics
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> Thanks,
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> Jiangjie (Becket) Qin
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>>>>
>>>>>>>> > > >>>>>>>>>
>>>>>>>> > > >>>>>>>>>
>>>>>>>> > > >>>>>>>>>
>>>>>>>> > > >>>>>>>
>>>>>>>> > > >>>>>>>
>>>>>>>> > > >>>>>>>
>>>>>>>> > > >>>>>
>>>>>>>> > > >>>>>
>>>>>>>> > > >>
>>>>>>>> > > >>
>>>>>>>> > >
>>>>>>>> > >
>>>>>>>> >
>>>>>>>>
>>>>>>>>
>>>>>>>> --
>>>>>>>>
>>>>>>>> Konstantin Knauf
>>>>>>>>
>>>>>>>> https://twitter.com/snntrable
>>>>>>>>
>>>>>>>> https://github.com/knaufk
>>>>>>>>
>>>>>>>
Re: [DISCUSS] FLIP-33: Standardize connector metrics
Posted by Becket Qin <be...@gmail.com>.
Hey Stephan,
Thanks for the quick reply. I actually forgot to mention that I also added
a "watermarkLag" metric to the Source metrics in addition to the
"currentFetchEventTimeLag" and "currentEmitEventTimeLag".
So in the current proposal, both XXEventTimeLag will be based on event
timestamps, while the watermarkLag is based on watermark. And all the lags
are defined against the wall clock time. Does this cover what you are
proposing?
Thanks,
Jiangjie (Becket) Qin
On Fri, Sep 18, 2020 at 6:08 PM Stephan Ewen <st...@ververica.com> wrote:
> Hi Becket!
>
> I am wondering if it makes sense to do the following small change:
>
> - Have "currentFetchEventTimeLag" be defined on event timestamps
> (optionally, if the source system exposes it) <== this is like in your
> proposal
> this helps understand how long the records were in the source before
>
> - BUT change "currentEmitEventTimeLag" to be "currentSourceWatermarkLag"
> instead.
> That way, users can see how far behind the wall-clock-time the source
> progress is all in all.
> It is also a more well defined metric as it does not oscillate with
> out-of-order events.
>
> What do you think?
>
> Best,
> Stephan
>
>
>
> On Fri, Sep 18, 2020 at 12:02 PM Becket Qin <be...@gmail.com> wrote:
>
>> Hi folks,
>>
>> Thanks for all the great feedback. I have just updated FLIP-33 wiki with
>> the following changes:
>>
>> 1. Renaming. "currentFetchLatency" to "currentFetchEventTimeLag",
>> "currentLatency" to "currentEmitEventTimeLag".
>> 2. Added the public interface code change required for the new metrics.
>> 3. Added description of whether a metric is predefined or optional, and
>> which component is expected to update the metric.
>>
>> Please let me know if you have any questions. I'll start a vote in two
>> days if there are no further concerns.
>>
>> Thanks,
>>
>> Jiangjie (Becket) Qin
>>
>> On Wed, Sep 9, 2020 at 9:56 AM Becket Qin <be...@gmail.com> wrote:
>>
>>> Hi Stephan,
>>>
>>> Thanks for the input. Just a few more clarifications / questions.
>>>
>>> *Num Bytes / Records Metrics*
>>>
>>> 1. At this point, the *numRecordsIn(Rate)* metrics exist in both
>>> OperatorIOMetricGroup and TaskIOMetricGroup. I did not find
>>> *numRecordsIn(Rate)* in the TaskIOMetricGroup updated anywhere other
>>> than in the unit tests. Am I missing something?
>>>
>>> 2. *numBytesIn(Rate)* metrics only exist in TaskIOMetricGroup. At this
>>> point, the SourceReaders only has access to a SourceReaderContext which
>>> provides an OperatorMetricGroup. So it seems that the connector developers
>>> are not able to update the *numBytesIn(Rate). *With the multiple Source
>>> chaining support, it is possible that there are multiple Sources are in the
>>> same task. So it looks that we need to add *numBytesIn(Rate)* to the
>>> operator metrics as well.
>>>
>>>
>>> *Current (Fetch) Latency*
>>>
>>> *currentFetchLatency* helps clearly tell whether the latency is caused
>>> by Flink or not. Backpressure is not the only reason that we see fetch
>>> latency. Even if there is no back pressure, the records may have passed a
>>> long pipeline before they entered Flink. For example, say the *currentLatency
>>> *is 10 seconds and there is no backpressure. Does that mean the record
>>> spent 10 seconds in the Source operator? If not, how much did Flink
>>> contribute to that 10 seconds of latency? These questions are frequently
>>> asked and hard to tell without the fetch latency.
>>>
>>> For "currentFetchLatency", we would need to understand timestamps before
>>>> the records are decoded. That is only possible for some sources, where the
>>>> client gives us the records in a (partially) decoded from already (like
>>>> Kafka). Then, some work has been done between the fetch time and the time
>>>> we update the metric already, so it is already a bit closer to the
>>>> "currentFetchLatency". I think following this train of thought, there is
>>>> diminished benefit from that specific metric.
>>>
>>>
>>> We may not have to report the fetch latency before records are decoded.
>>> One solution is to remember the* FetchTime* when the encoded records
>>> are fetched, and report the fetch latency after the records are decoded by
>>> computing (*FetchTime - EventTime*). An approximate implementation
>>> would be adding a *FetchTime *field to the *RecordsWithSplitIds* assuming
>>> that all the records in that data structure are fetched at the same time.
>>>
>>> Thoughts?
>>>
>>> Thanks,
>>>
>>> Jiangjie (Becket) Qin
>>>
>>> On Wed, Sep 9, 2020 at 12:42 AM Stephan Ewen <st...@ververica.com>
>>> wrote:
>>>
>>>> Thanks for reviving this, Becket!
>>>>
>>>> I think Konstantin's comments are great. I'd add these points:
>>>>
>>>> *Num Bytes / Records Metrics*
>>>>
>>>> For "numBytesIn" and "numRecordsIn", we should reuse the
>>>> OperatorIOMetric group, then it also gets reported to the overview page in
>>>> the Web UI.
>>>>
>>>> The "numBytesInPerSecond" and "numRecordsInPerSecond" are automatically
>>>> derived metrics, no need to do anything once we populate the above two
>>>> metrics
>>>>
>>>>
>>>> *Current (Fetch) Latency*
>>>>
>>>> I would really go for "eventTimeLag" rather than "fetchLatency". I
>>>> think "eventTimeLag" is a term that has some adoption in the Flink
>>>> community and beyond.
>>>>
>>>> I am not so sure that I see the benefit between "currentLatency" and
>>>> "currentFetchLatency", (or event time lag before/after) as this only is
>>>> different by the time it takes to emit a batch.
>>>> - In a non-backpressured case, these should be virtually identical
>>>> (and both dominated by watermark lag, not the actual time it takes the
>>>> fetch to be emitted)
>>>> - In a backpressured case, why do you care about when data was
>>>> fetched, as opposed to emitted? Emitted time is relevant for application
>>>> semantics and checkpoints. Fetch time seems to be an implementation detail
>>>> (how much does the source buffer).
>>>>
>>>> The "currentLatency" (eventTimeLagAfter) can be computed
>>>> out-of-the-box, independent of a source implementation, so that is also a
>>>> good argument to make it the main metric.
>>>> We know timestamps and watermarks in the source. Except for cases where
>>>> no watermarks have been defined at all (batch jobs or pure processing time
>>>> jobs), in which case this metric should probably be "Infinite".
>>>>
>>>> For "currentFetchLatency", we would need to understand timestamps
>>>> before the records are decoded. That is only possible for some sources,
>>>> where the client gives us the records in a (partially) decoded from already
>>>> (like Kafka). Then, some work has been done between the fetch time and the
>>>> time we update the metric already, so it is already a bit closer to the
>>>> "currentFetchLatency". I think following this train of thought, there is
>>>> diminished benefit from that specific metric.
>>>>
>>>>
>>>> *Idle Time*
>>>>
>>>> I agree, it would be great to rename this. Maybe to "sourceWaitTime" or
>>>> "sourceIdleTime" so to make clear that this is not exactly the time that
>>>> Flink's processing pipeline is idle, but the time where the source does not
>>>> have new data.
>>>>
>>>> This is not an easy metric to collect, though (except maybe for the
>>>> sources that are only idle while they have no split assigned, like
>>>> continuous file source).
>>>>
>>>> *Source Specific Metrics*
>>>>
>>>> I believe source-specific would only be "sourceIdleTime",
>>>> "numRecordsInErrors", "pendingBytes", and "pendingRecords".
>>>>
>>>>
>>>> *Conclusion*
>>>>
>>>> We can probably add "numBytesIn" and "numRecordsIn" and "eventTimeLag"
>>>> right away, with little complexity.
>>>> I'd suggest to start with these right away.
>>>>
>>>> Best,
>>>> Stephan
>>>>
>>>>
>>>> On Tue, Sep 8, 2020 at 3:25 PM Becket Qin <be...@gmail.com> wrote:
>>>>
>>>>> Hey Konstantin,
>>>>>
>>>>> Thanks for the feedback and suggestions. Please see the reply below.
>>>>>
>>>>> * idleTime: In the meantime, a similar metric "idleTimeMsPerSecond" has
>>>>>> been introduced in https://issues.apache.org/jira/browse/FLINK-16864.
>>>>>> They
>>>>>> have a similar name, but different definitions of idleness,
>>>>>> e.g. "idleTimeMsPerSecond" considers the SourceTask idle, when it is
>>>>>> backpressured. Can we make it clearer that these two metrics mean
>>>>>> different
>>>>>> things?
>>>>>
>>>>>
>>>>> That is a good point. I did not notice this metric earlier. It seems
>>>>> that both metrics are useful to the users. One tells them how busy the
>>>>> source is and how much more throughput the source can handle. The other
>>>>> tells the users how long since the source has seen the last record, which
>>>>> is useful for debugging. I'll update the FLIP to make it clear.
>>>>>
>>>>> * "current(Fetch)Latency" I am wondering if
>>>>>> "eventTimeLag(Before|After)"
>>>>>> is more descriptive/clear. What do others think?
>>>>>
>>>>>
>>>>> I am quite open to the ideas on these names. In fact I also feel
>>>>> "current(Fetch)Latency" are not super intuitive. So it would be great if we
>>>>> can have better names.
>>>>>
>>>>> * Current(Fetch)Latency implies that the timestamps are directly
>>>>>> extracted in the source connector, right? Will this be the default for
>>>>>> FLIP-27 sources anyway?
>>>>>
>>>>>
>>>>> The "currentFetchLatency" will probably be reported by each source
>>>>> implementation, because the data fetching is done by SplitReaders and there
>>>>> is no base implementation. The "currentLatency", on the other hand, can be
>>>>> reported by the SourceReader base implementation. However, since developers
>>>>> can actually implement their own source connector without using our base
>>>>> implementation, these metric guidance are still useful for the connector
>>>>> developers in that case.
>>>>>
>>>>> * Does FLIP-33 also include the implementation of these metrics (to the
>>>>>> extent possible) for all connectors currently available in Apache
>>>>>> Flink or
>>>>>> is the "per-connector implementation" out-of-scope?
>>>>>
>>>>>
>>>>> FLIP-33 itself does not specify any implementation of those metrics.
>>>>> But the connectors we provide in Apache Flink will follow the guidance of
>>>>> FLIP-33 to emit those metrics when applicable. Maybe We can have some
>>>>> public static Strings defined for the metric names to help other connector
>>>>> developers follow the same guidance. I can also add that to the public
>>>>> interface section of the FLIP if we decide to do that.
>>>>>
>>>>> Thanks,
>>>>>
>>>>> Jiangjie (Becket) Qin
>>>>>
>>>>> On Tue, Sep 8, 2020 at 9:02 PM Becket Qin <be...@gmail.com>
>>>>> wrote:
>>>>>
>>>>>>
>>>>>>
>>>>>> On Tue, Sep 8, 2020 at 6:55 PM Konstantin Knauf <kn...@apache.org>
>>>>>> wrote:
>>>>>>
>>>>>>> Hi Becket,
>>>>>>>
>>>>>>> Thank you for picking up this FLIP. I have a few questions:
>>>>>>>
>>>>>>> * two thoughts on naming:
>>>>>>> * idleTime: In the meantime, a similar metric
>>>>>>> "idleTimeMsPerSecond" has
>>>>>>> been introduced in https://issues.apache.org/jira/browse/FLINK-16864.
>>>>>>> They
>>>>>>> have a similar name, but different definitions of idleness,
>>>>>>> e.g. "idleTimeMsPerSecond" considers the SourceTask idle, when it is
>>>>>>> backpressured. Can we make it clearer that these two metrics mean
>>>>>>> different
>>>>>>> things?
>>>>>>>
>>>>>>> * "current(Fetch)Latency" I am wondering if
>>>>>>> "eventTimeLag(Before|After)"
>>>>>>> is more descriptive/clear. What do others think?
>>>>>>>
>>>>>>> * Current(Fetch)Latency implies that the timestamps are directly
>>>>>>> extracted in the source connector, right? Will this be the default
>>>>>>> for
>>>>>>> FLIP-27 sources anyway?
>>>>>>>
>>>>>>> * Does FLIP-33 also include the implementation of these metrics (to
>>>>>>> the
>>>>>>> extent possible) for all connectors currently available in Apache
>>>>>>> Flink or
>>>>>>> is the "per-connector implementation" out-of-scope?
>>>>>>>
>>>>>>> Thanks,
>>>>>>>
>>>>>>> Konstantin
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> On Fri, Sep 4, 2020 at 4:56 PM Becket Qin <be...@gmail.com>
>>>>>>> wrote:
>>>>>>>
>>>>>>> > Hi all,
>>>>>>> >
>>>>>>> > To complete the Source refactoring work, I'd like to revive this
>>>>>>> > discussion. Since the mail thread has been dormant for more than a
>>>>>>> year,
>>>>>>> > just to recap the motivation of the FLIP:
>>>>>>> >
>>>>>>> > 1. The FLIP proposes to standardize the connector metrics by giving
>>>>>>> > guidance on the metric specifications, including the name, type
>>>>>>> and meaning
>>>>>>> > of the metrics.
>>>>>>> > 2. It is OK for a connector to not emit some of the metrics in the
>>>>>>> metric
>>>>>>> > guidance, but if a metric of the same semantic is emitted, the
>>>>>>> > implementation should follow the guidance.
>>>>>>> > 3. It is OK for a connector to emit more metrics than what are
>>>>>>> listed in
>>>>>>> > the FLIP. This includes having an alias for a metric specified in
>>>>>>> the FLIP.
>>>>>>> > 4. We will implement some of the metrics out of the box in the
>>>>>>> default
>>>>>>> > implementation of FLIP-27, as long as it is applicable.
>>>>>>> >
>>>>>>> > The FLIP wiki is following:
>>>>>>> > https://cwiki.apache.org/confluence/display/FLINK/FLIP-33
>>>>>>> > %3A+Standardize+Connector+Metrics
>>>>>>> >
>>>>>>> > Any thoughts?
>>>>>>> >
>>>>>>> > Thanks,
>>>>>>> >
>>>>>>> > Jiangjie (Becket) Qin
>>>>>>> >
>>>>>>> >
>>>>>>> > On Fri, Jun 14, 2019 at 2:29 PM Piotr Nowojski <
>>>>>>> piotr@ververica.com>
>>>>>>> > wrote:
>>>>>>> >
>>>>>>> > > > we will need to revisit the convention list and adjust them
>>>>>>> accordingly
>>>>>>> > > when FLIP-27 is ready
>>>>>>> > >
>>>>>>> > >
>>>>>>> > > Yes, this sounds good :)
>>>>>>> > >
>>>>>>> > > Piotrek
>>>>>>> > >
>>>>>>> > > > On 13 Jun 2019, at 13:35, Becket Qin <be...@gmail.com>
>>>>>>> wrote:
>>>>>>> > > >
>>>>>>> > > > Hi Piotr,
>>>>>>> > > >
>>>>>>> > > > That's great to know. Chances are that we will need to revisit
>>>>>>> the
>>>>>>> > > > convention list and adjust them accordingly when FLIP-27 is
>>>>>>> ready, At
>>>>>>> > > that
>>>>>>> > > > point we can mark some of the metrics as available by default
>>>>>>> for
>>>>>>> > > > connectors implementing the new interface.
>>>>>>> > > >
>>>>>>> > > > Thanks,
>>>>>>> > > >
>>>>>>> > > > Jiangjie (Becket) Qin
>>>>>>> > > >
>>>>>>> > > > On Thu, Jun 13, 2019 at 3:51 PM Piotr Nowojski <
>>>>>>> piotr@ververica.com>
>>>>>>> > > wrote:
>>>>>>> > > >
>>>>>>> > > >> Thanks for driving this. I’ve just noticed one small thing.
>>>>>>> With new
>>>>>>> > > >> SourceReader interface Flink will be able to provide
>>>>>>> `idleTime` metric
>>>>>>> > > >> automatically.
>>>>>>> > > >>
>>>>>>> > > >> Piotrek
>>>>>>> > > >>
>>>>>>> > > >>> On 13 Jun 2019, at 03:30, Becket Qin <be...@gmail.com>
>>>>>>> wrote:
>>>>>>> > > >>>
>>>>>>> > > >>> Thanks all for the feedback and discussion.
>>>>>>> > > >>>
>>>>>>> > > >>> Since there wasn't any concern raised, I've started the
>>>>>>> voting thread
>>>>>>> > > for
>>>>>>> > > >>> this FLIP, but please feel free to continue the discussion
>>>>>>> here if
>>>>>>> > you
>>>>>>> > > >>> think something still needs to be addressed.
>>>>>>> > > >>>
>>>>>>> > > >>> Thanks,
>>>>>>> > > >>>
>>>>>>> > > >>> Jiangjie (Becket) Qin
>>>>>>> > > >>>
>>>>>>> > > >>>
>>>>>>> > > >>>
>>>>>>> > > >>> On Mon, Jun 10, 2019 at 9:10 AM Becket Qin <
>>>>>>> becket.qin@gmail.com>
>>>>>>> > > wrote:
>>>>>>> > > >>>
>>>>>>> > > >>>> Hi Piotr,
>>>>>>> > > >>>>
>>>>>>> > > >>>> Thanks for the comments. Yes, you are right. Users will
>>>>>>> have to look
>>>>>>> > > at
>>>>>>> > > >>>> other metrics to decide whether the pipeline is healthy or
>>>>>>> not in
>>>>>>> > the
>>>>>>> > > >> first
>>>>>>> > > >>>> place before they can use the time-based metric to fix the
>>>>>>> > bottleneck.
>>>>>>> > > >>>>
>>>>>>> > > >>>> I agree that once we have FLIP-27 ready, some of the
>>>>>>> metrics can
>>>>>>> > just
>>>>>>> > > be
>>>>>>> > > >>>> reported by the abstract implementation.
>>>>>>> > > >>>>
>>>>>>> > > >>>> I've updated FLIP-33 wiki page to add the pendingBytes and
>>>>>>> > > >> pendingRecords
>>>>>>> > > >>>> metric. Please let me know if you have any concern over the
>>>>>>> updated
>>>>>>> > > >> metric
>>>>>>> > > >>>> convention proposal.
>>>>>>> > > >>>>
>>>>>>> > > >>>> @Chesnay Schepler <ch...@apache.org> @Stephan Ewen
>>>>>>> > > >>>> <st...@ververica.com> will you also have time to take a
>>>>>>> look at
>>>>>>> > the
>>>>>>> > > >>>> proposed metric convention? If there is no further concern
>>>>>>> I'll
>>>>>>> > start
>>>>>>> > > a
>>>>>>> > > >>>> voting thread for this FLIP in two days.
>>>>>>> > > >>>>
>>>>>>> > > >>>> Thanks,
>>>>>>> > > >>>>
>>>>>>> > > >>>> Jiangjie (Becket) Qin
>>>>>>> > > >>>>
>>>>>>> > > >>>>
>>>>>>> > > >>>>
>>>>>>> > > >>>> On Wed, Jun 5, 2019 at 6:54 PM Piotr Nowojski <
>>>>>>> piotr@ververica.com>
>>>>>>> > > >> wrote:
>>>>>>> > > >>>>
>>>>>>> > > >>>>> Hi Becket,
>>>>>>> > > >>>>>
>>>>>>> > > >>>>> Thanks for the answer :)
>>>>>>> > > >>>>>
>>>>>>> > > >>>>>> By time-based metric, I meant the portion of time spent on
>>>>>>> > producing
>>>>>>> > > >> the
>>>>>>> > > >>>>>> record to downstream. For example, a source connector can
>>>>>>> report
>>>>>>> > > that
>>>>>>> > > >>>>> it's
>>>>>>> > > >>>>>> spending 80% of time to emit record to downstream
>>>>>>> processing
>>>>>>> > > pipeline.
>>>>>>> > > >>>>> In
>>>>>>> > > >>>>>> another case, a sink connector may report that its
>>>>>>> spending 30% of
>>>>>>> > > >> time
>>>>>>> > > >>>>>> producing the records to the external system.
>>>>>>> > > >>>>>>
>>>>>>> > > >>>>>> This is in some sense equivalent to the buffer usage
>>>>>>> metric:
>>>>>>> > > >>>>>
>>>>>>> > > >>>>>> - 80% of time spent on emitting records to downstream --->
>>>>>>> > > downstream
>>>>>>> > > >>>>>> node is bottleneck ---> output buffer is probably full.
>>>>>>> > > >>>>>> - 30% of time spent on emitting records to downstream --->
>>>>>>> > > downstream
>>>>>>> > > >>>>>> node is not bottleneck ---> output buffer is probably not
>>>>>>> full.
>>>>>>> > > >>>>>
>>>>>>> > > >>>>> If by “time spent on emitting records to downstream” you
>>>>>>> understand
>>>>>>> > > >>>>> “waiting on back pressure”, then I see your point. And I
>>>>>>> agree that
>>>>>>> > > >> some
>>>>>>> > > >>>>> kind of ratio/time based metric gives you more
>>>>>>> information. However
>>>>>>> > > >> under
>>>>>>> > > >>>>> “time spent on emitting records to downstream” might be
>>>>>>> hidden the
>>>>>>> > > >>>>> following (extreme) situation:
>>>>>>> > > >>>>>
>>>>>>> > > >>>>> 1. Job is barely able to handle influx of records, there
>>>>>>> is 99%
>>>>>>> > > >>>>> CPU/resource usage in the cluster, but nobody is
>>>>>>> > > >>>>> bottlenecked/backpressured, all output buffers are empty,
>>>>>>> everybody
>>>>>>> > > is
>>>>>>> > > >>>>> waiting in 1% of it’s time for more records to process.
>>>>>>> > > >>>>> 2. 80% time can still be spent on "down stream operators”,
>>>>>>> because
>>>>>>> > > they
>>>>>>> > > >>>>> are the CPU intensive operations, but this doesn’t mean
>>>>>>> that
>>>>>>> > > >> increasing the
>>>>>>> > > >>>>> parallelism down the stream will help with anything there.
>>>>>>> To the
>>>>>>> > > >> contrary,
>>>>>>> > > >>>>> increasing parallelism of the source operator might help to
>>>>>>> > increase
>>>>>>> > > >>>>> resource utilisation up to 100%.
>>>>>>> > > >>>>>
>>>>>>> > > >>>>> However, this “time based/ratio” approach can be extended
>>>>>>> to
>>>>>>> > > in/output
>>>>>>> > > >>>>> buffer usage. Besides collecting an information that
>>>>>>> input/output
>>>>>>> > > >> buffer is
>>>>>>> > > >>>>> full/empty, we can probe profile how often are buffer
>>>>>>> empty/full.
>>>>>>> > If
>>>>>>> > > >> output
>>>>>>> > > >>>>> buffer is full 1% of times, there is almost no back
>>>>>>> pressure. If
>>>>>>> > it’s
>>>>>>> > > >> full
>>>>>>> > > >>>>> 80% of times, there is some back pressure, if it’s full
>>>>>>> 99.9% of
>>>>>>> > > times,
>>>>>>> > > >>>>> there is huge back pressure.
>>>>>>> > > >>>>>
>>>>>>> > > >>>>> Now for autoscaling you could compare the input & output
>>>>>>> buffers
>>>>>>> > fill
>>>>>>> > > >>>>> ratio:
>>>>>>> > > >>>>>
>>>>>>> > > >>>>> 1. Both are high, the source of bottleneck is down the
>>>>>>> stream
>>>>>>> > > >>>>> 2. Output is low, input is high, this is the bottleneck
>>>>>>> and the
>>>>>>> > > higher
>>>>>>> > > >>>>> the difference, the bigger source of bottleneck is this is
>>>>>>> > > >> operator/task
>>>>>>> > > >>>>> 3. Output is high, input is low - there was some load
>>>>>>> spike that we
>>>>>>> > > are
>>>>>>> > > >>>>> currently finishing to process
>>>>>>> > > >>>>>
>>>>>>> > > >>>>>
>>>>>>> > > >>>>>
>>>>>>> > > >>>>> But long story short, we are probably diverging from the
>>>>>>> topic of
>>>>>>> > > this
>>>>>>> > > >>>>> discussion, and we can discuss this at some later point.
>>>>>>> > > >>>>>
>>>>>>> > > >>>>> For now, for sources:
>>>>>>> > > >>>>>
>>>>>>> > > >>>>> as I wrote before, +1 for:
>>>>>>> > > >>>>> - pending.bytes, Gauge
>>>>>>> > > >>>>> - pending.messages, Gauge
>>>>>>> > > >>>>>
>>>>>>> > > >>>>> When we will be developing/discussing SourceReader from
>>>>>>> FLIP-27 we
>>>>>>> > > >> might
>>>>>>> > > >>>>> then add:
>>>>>>> > > >>>>>
>>>>>>> > > >>>>> - in-memory.buffer.usage (0 - 100%)
>>>>>>> > > >>>>>
>>>>>>> > > >>>>> Which will be estimated automatically by Flink while user
>>>>>>> will be
>>>>>>> > > able
>>>>>>> > > >> to
>>>>>>> > > >>>>> override/provide better estimation.
>>>>>>> > > >>>>>
>>>>>>> > > >>>>> Piotrek
>>>>>>> > > >>>>>
>>>>>>> > > >>>>>> On 5 Jun 2019, at 05:42, Becket Qin <be...@gmail.com>
>>>>>>> wrote:
>>>>>>> > > >>>>>>
>>>>>>> > > >>>>>> Hi Piotr,
>>>>>>> > > >>>>>>
>>>>>>> > > >>>>>> Thanks for the explanation. Please see some
>>>>>>> clarifications below.
>>>>>>> > > >>>>>>
>>>>>>> > > >>>>>> By time-based metric, I meant the portion of time spent on
>>>>>>> > producing
>>>>>>> > > >> the
>>>>>>> > > >>>>>> record to downstream. For example, a source connector can
>>>>>>> report
>>>>>>> > > that
>>>>>>> > > >>>>> it's
>>>>>>> > > >>>>>> spending 80% of time to emit record to downstream
>>>>>>> processing
>>>>>>> > > pipeline.
>>>>>>> > > >>>>> In
>>>>>>> > > >>>>>> another case, a sink connector may report that its
>>>>>>> spending 30% of
>>>>>>> > > >> time
>>>>>>> > > >>>>>> producing the records to the external system.
>>>>>>> > > >>>>>>
>>>>>>> > > >>>>>> This is in some sense equivalent to the buffer usage
>>>>>>> metric:
>>>>>>> > > >>>>>> - 80% of time spent on emitting records to downstream --->
>>>>>>> > > downstream
>>>>>>> > > >>>>>> node is bottleneck ---> output buffer is probably full.
>>>>>>> > > >>>>>> - 30% of time spent on emitting records to downstream --->
>>>>>>> > > downstream
>>>>>>> > > >>>>>> node is not bottleneck ---> output buffer is probably not
>>>>>>> full.
>>>>>>> > > >>>>>>
>>>>>>> > > >>>>>> However, the time-based metric has a few advantages that
>>>>>>> the
>>>>>>> > buffer
>>>>>>> > > >>>>> usage
>>>>>>> > > >>>>>> metric may not have.
>>>>>>> > > >>>>>>
>>>>>>> > > >>>>>> 1. Buffer usage metric may not be applicable to all the
>>>>>>> connector
>>>>>>> > > >>>>>> implementations, while reporting time-based metric are
>>>>>>> always
>>>>>>> > > doable.
>>>>>>> > > >>>>>> Some source connectors may not have any input buffer, or
>>>>>>> they may
>>>>>>> > > use
>>>>>>> > > >>>>> some
>>>>>>> > > >>>>>> third party library that does not expose the input buffer
>>>>>>> at all.
>>>>>>> > > >>>>>> Similarly, for sink connectors, the implementation may
>>>>>>> not have
>>>>>>> > any
>>>>>>> > > >>>>> output
>>>>>>> > > >>>>>> buffer, or the third party library does not expose such
>>>>>>> buffer.
>>>>>>> > > >>>>>>
>>>>>>> > > >>>>>> 2. Although both type of metrics can detect bottleneck,
>>>>>>> time-based
>>>>>>> > > >>>>> metrics
>>>>>>> > > >>>>>> can be used to generate a more informed action to remove
>>>>>>> the
>>>>>>> > > >> bottleneck.
>>>>>>> > > >>>>>> For example, when the downstream is bottleneck, the
>>>>>>> output buffer
>>>>>>> > > >> usage
>>>>>>> > > >>>>>> metric is likely to be 100%, and the input buffer usage
>>>>>>> might be
>>>>>>> > 0%.
>>>>>>> > > >>>>> That
>>>>>>> > > >>>>>> means we don't know what is the suitable parallelism to
>>>>>>> lift the
>>>>>>> > > >>>>>> bottleneck. The time-based metric, on the other hand,
>>>>>>> would give
>>>>>>> > > >> useful
>>>>>>> > > >>>>>> information, e.g. if 80% of time was spent on emitting
>>>>>>> records, we
>>>>>>> > > can
>>>>>>> > > >>>>>> roughly increase the downstream node parallelism by 4
>>>>>>> times.
>>>>>>> > > >>>>>>
>>>>>>> > > >>>>>> Admittedly, the time-based metrics are more expensive
>>>>>>> than buffer
>>>>>>> > > >>>>> usage. So
>>>>>>> > > >>>>>> we may have to do some sampling to reduce the cost. But in
>>>>>>> > general,
>>>>>>> > > >>>>> using
>>>>>>> > > >>>>>> time-based metrics seems worth adding.
>>>>>>> > > >>>>>>
>>>>>>> > > >>>>>> That being said, I don't think buffer usage metric and
>>>>>>> time-based
>>>>>>> > > >>>>> metrics
>>>>>>> > > >>>>>> are mutually exclusive. We can probably have both. It is
>>>>>>> just that
>>>>>>> > > in
>>>>>>> > > >>>>>> practice, features like auto-scaling might prefer
>>>>>>> time-based
>>>>>>> > metrics
>>>>>>> > > >> for
>>>>>>> > > >>>>>> the reason stated above.
>>>>>>> > > >>>>>>
>>>>>>> > > >>>>>>> 1. Define the metrics that would allow us to manually
>>>>>>> detect
>>>>>>> > > >>>>> bottlenecks.
>>>>>>> > > >>>>>> As I wrote, we already have them in most of the places,
>>>>>>> except of
>>>>>>> > > >>>>>> sources/sinks.
>>>>>>> > > >>>>>>> 2. Use those metrics, to automatically detect
>>>>>>> bottlenecks.
>>>>>>> > > Currently
>>>>>>> > > >> we
>>>>>>> > > >>>>>> are only automatically detecting back pressure and
>>>>>>> reporting it to
>>>>>>> > > the
>>>>>>> > > >>>>> user
>>>>>>> > > >>>>>> in web UI (is it exposed as a metric at all?). Detecting
>>>>>>> the root
>>>>>>> > > >> cause
>>>>>>> > > >>>>> of
>>>>>>> > > >>>>>> the back pressure (bottleneck) is one step further.
>>>>>>> > > >>>>>>> 3. Use the knowledge about where exactly the bottleneck
>>>>>>> is
>>>>>>> > located,
>>>>>>> > > >> to
>>>>>>> > > >>>>>> try to do something with it.
>>>>>>> > > >>>>>>
>>>>>>> > > >>>>>> As explained above, I think time-based metric also
>>>>>>> addresses item
>>>>>>> > 1
>>>>>>> > > >> and
>>>>>>> > > >>>>>> item 2.
>>>>>>> > > >>>>>>
>>>>>>> > > >>>>>> Any thoughts？
>>>>>>> > > >>>>>>
>>>>>>> > > >>>>>> Thanks,
>>>>>>> > > >>>>>>
>>>>>>> > > >>>>>> Jiangjie (Becket) Qin
>>>>>>> > > >>>>>>
>>>>>>> > > >>>>>>
>>>>>>> > > >>>>>>
>>>>>>> > > >>>>>> On Mon, Jun 3, 2019 at 4:14 PM Piotr Nowojski <
>>>>>>> > piotr@ververica.com>
>>>>>>> > > >>>>> wrote:
>>>>>>> > > >>>>>>
>>>>>>> > > >>>>>>> Hi again :)
>>>>>>> > > >>>>>>>
>>>>>>> > > >>>>>>>> - pending.bytes, Gauge
>>>>>>> > > >>>>>>>> - pending.messages, Gauge
>>>>>>> > > >>>>>>>
>>>>>>> > > >>>>>>>
>>>>>>> > > >>>>>>> +1
>>>>>>> > > >>>>>>>
>>>>>>> > > >>>>>>> And true, instead of overloading one of the metric it is
>>>>>>> better
>>>>>>> > > when
>>>>>>> > > >>>>> user
>>>>>>> > > >>>>>>> can choose to provide only one of them.
>>>>>>> > > >>>>>>>
>>>>>>> > > >>>>>>> Re 2:
>>>>>>> > > >>>>>>>
>>>>>>> > > >>>>>>>> If I understand correctly, this metric along with the
>>>>>>> pending
>>>>>>> > > >> mesages
>>>>>>> > > >>>>> /
>>>>>>> > > >>>>>>>> bytes would answer the questions of:
>>>>>>> > > >>>>>>>
>>>>>>> > > >>>>>>>> - Does the connector consume fast enough? Lagging
>>>>>>> behind + empty
>>>>>>> > > >>>>> buffer
>>>>>>> > > >>>>>>> =
>>>>>>> > > >>>>>>>> cannot consume fast enough.
>>>>>>> > > >>>>>>>> - Does the connector emit fast enough? Lagging behind +
>>>>>>> full
>>>>>>> > > buffer
>>>>>>> > > >> =
>>>>>>> > > >>>>>>>> cannot emit fast enough, i.e. the Flink pipeline is
>>>>>>> slow.
>>>>>>> > > >>>>>>>
>>>>>>> > > >>>>>>> Yes, exactly. This can also be used to support decisions
>>>>>>> like
>>>>>>> > > >> changing
>>>>>>> > > >>>>> the
>>>>>>> > > >>>>>>> parallelism of the sources and/or down stream operators.
>>>>>>> > > >>>>>>>
>>>>>>> > > >>>>>>> I’m not sure if I understand your proposal with time
>>>>>>> based
>>>>>>> > > >>>>> measurements.
>>>>>>> > > >>>>>>> Maybe I’m missing something, but I do not see how
>>>>>>> measuring time
>>>>>>> > > >> alone
>>>>>>> > > >>>>>>> could answer the problem: where is the bottleneck. Time
>>>>>>> spent on
>>>>>>> > > the
>>>>>>> > > >>>>>>> next/emit might be short or long (depending on how heavy
>>>>>>> to
>>>>>>> > process
>>>>>>> > > >> the
>>>>>>> > > >>>>>>> record is) and the source can still be bottlenecked/back
>>>>>>> > pressured
>>>>>>> > > or
>>>>>>> > > >>>>> not.
>>>>>>> > > >>>>>>> Usually the easiest and the most reliable way how to
>>>>>>> detect
>>>>>>> > > >>>>> bottlenecks is
>>>>>>> > > >>>>>>> by checking usage of input & output buffers, since when
>>>>>>> input
>>>>>>> > > buffer
>>>>>>> > > >> is
>>>>>>> > > >>>>>>> full while output buffer is empty, that’s the definition
>>>>>>> of a
>>>>>>> > > >>>>> bottleneck.
>>>>>>> > > >>>>>>> Also this is usually very easy and cheap to measure (it
>>>>>>> works
>>>>>>> > > >>>>> effectively
>>>>>>> > > >>>>>>> the same way as current’s Flink back pressure
>>>>>>> monitoring, but
>>>>>>> > more
>>>>>>> > > >>>>> cleanly,
>>>>>>> > > >>>>>>> without probing thread’s stack traces).
>>>>>>> > > >>>>>>>
>>>>>>> > > >>>>>>> Also keep in mind that we are already using the buffer
>>>>>>> usage
>>>>>>> > > metrics
>>>>>>> > > >>>>> for
>>>>>>> > > >>>>>>> detecting the bottlenecks in Flink’s internal network
>>>>>>> exchanges
>>>>>>> > > >> (manual
>>>>>>> > > >>>>>>> work). That’s the reason why I wanted to extend this to
>>>>>>> > > >> sources/sinks,
>>>>>>> > > >>>>>>> since they are currently our blind spot.
>>>>>>> > > >>>>>>>
>>>>>>> > > >>>>>>>> One feature we are currently working on to scale Flink
>>>>>>> > > automatically
>>>>>>> > > >>>>>>> relies
>>>>>>> > > >>>>>>>> on some metrics answering the same question
>>>>>>> > > >>>>>>>
>>>>>>> > > >>>>>>> That would be very helpful feature. I think in order to
>>>>>>> achieve
>>>>>>> > > that
>>>>>>> > > >> we
>>>>>>> > > >>>>>>> would need to:
>>>>>>> > > >>>>>>> 1. Define the metrics that would allow us to manually
>>>>>>> detect
>>>>>>> > > >>>>> bottlenecks.
>>>>>>> > > >>>>>>> As I wrote, we already have them in most of the places,
>>>>>>> except of
>>>>>>> > > >>>>>>> sources/sinks.
>>>>>>> > > >>>>>>> 2. Use those metrics, to automatically detect
>>>>>>> bottlenecks.
>>>>>>> > > Currently
>>>>>>> > > >> we
>>>>>>> > > >>>>>>> are only automatically detecting back pressure and
>>>>>>> reporting it
>>>>>>> > to
>>>>>>> > > >> the
>>>>>>> > > >>>>> user
>>>>>>> > > >>>>>>> in web UI (is it exposed as a metric at all?). Detecting
>>>>>>> the root
>>>>>>> > > >>>>> cause of
>>>>>>> > > >>>>>>> the back pressure (bottleneck) is one step further.
>>>>>>> > > >>>>>>> 3. Use the knowledge about where exactly the bottleneck
>>>>>>> is
>>>>>>> > located,
>>>>>>> > > >> to
>>>>>>> > > >>>>> try
>>>>>>> > > >>>>>>> to do something with it.
>>>>>>> > > >>>>>>>
>>>>>>> > > >>>>>>> I think you are aiming for point 3., but before we reach
>>>>>>> it, we
>>>>>>> > are
>>>>>>> > > >>>>> still
>>>>>>> > > >>>>>>> missing 1. & 2. Also even if we have 3., there is a
>>>>>>> value in 1 &
>>>>>>> > 2
>>>>>>> > > >> for
>>>>>>> > > >>>>>>> manual analysis/dashboards.
>>>>>>> > > >>>>>>>
>>>>>>> > > >>>>>>> However, having the knowledge of where the bottleneck
>>>>>>> is, doesn’t
>>>>>>> > > >>>>>>> necessarily mean that we know what we can do about it.
>>>>>>> For
>>>>>>> > example
>>>>>>> > > >>>>>>> increasing parallelism might or might not help with
>>>>>>> anything
>>>>>>> > (data
>>>>>>> > > >>>>> skew,
>>>>>>> > > >>>>>>> bottleneck on some resource that does not scale), but
>>>>>>> this remark
>>>>>>> > > >>>>> applies
>>>>>>> > > >>>>>>> always, regardless of the way how did we detect the
>>>>>>> bottleneck.
>>>>>>> > > >>>>>>>
>>>>>>> > > >>>>>>> Piotrek
>>>>>>> > > >>>>>>>
>>>>>>> > > >>>>>>>> On 3 Jun 2019, at 06:16, Becket Qin <
>>>>>>> becket.qin@gmail.com>
>>>>>>> > wrote:
>>>>>>> > > >>>>>>>>
>>>>>>> > > >>>>>>>> Hi Piotr,
>>>>>>> > > >>>>>>>>
>>>>>>> > > >>>>>>>> Thanks for the suggestion. Some thoughts below:
>>>>>>> > > >>>>>>>>
>>>>>>> > > >>>>>>>> Re 1: The pending messages / bytes.
>>>>>>> > > >>>>>>>> I completely agree these are very useful metrics and we
>>>>>>> should
>>>>>>> > > >> expect
>>>>>>> > > >>>>> the
>>>>>>> > > >>>>>>>> connector to report. WRT the way to expose them, it
>>>>>>> seems more
>>>>>>> > > >>>>> consistent
>>>>>>> > > >>>>>>>> to add two metrics instead of adding a method (unless
>>>>>>> there are
>>>>>>> > > >> other
>>>>>>> > > >>>>> use
>>>>>>> > > >>>>>>>> cases other than metric reporting). So we can add the
>>>>>>> following
>>>>>>> > > two
>>>>>>> > > >>>>>>> metrics.
>>>>>>> > > >>>>>>>> - pending.bytes, Gauge
>>>>>>> > > >>>>>>>> - pending.messages, Gauge
>>>>>>> > > >>>>>>>> Applicable connectors can choose to report them. These
>>>>>>> two
>>>>>>> > metrics
>>>>>>> > > >>>>> along
>>>>>>> > > >>>>>>>> with latency should be sufficient for users to
>>>>>>> understand the
>>>>>>> > > >> progress
>>>>>>> > > >>>>>>> of a
>>>>>>> > > >>>>>>>> connector.
>>>>>>> > > >>>>>>>>
>>>>>>> > > >>>>>>>>
>>>>>>> > > >>>>>>>> Re 2: Number of buffered data in-memory of the connector
>>>>>>> > > >>>>>>>> If I understand correctly, this metric along with the
>>>>>>> pending
>>>>>>> > > >> mesages
>>>>>>> > > >>>>> /
>>>>>>> > > >>>>>>>> bytes would answer the questions of:
>>>>>>> > > >>>>>>>> - Does the connector consume fast enough? Lagging
>>>>>>> behind + empty
>>>>>>> > > >>>>> buffer
>>>>>>> > > >>>>>>> =
>>>>>>> > > >>>>>>>> cannot consume fast enough.
>>>>>>> > > >>>>>>>> - Does the connector emit fast enough? Lagging behind +
>>>>>>> full
>>>>>>> > > buffer
>>>>>>> > > >> =
>>>>>>> > > >>>>>>>> cannot emit fast enough, i.e. the Flink pipeline is
>>>>>>> slow.
>>>>>>> > > >>>>>>>>
>>>>>>> > > >>>>>>>> One feature we are currently working on to scale Flink
>>>>>>> > > automatically
>>>>>>> > > >>>>>>> relies
>>>>>>> > > >>>>>>>> on some metrics answering the same question, more
>>>>>>> specifically,
>>>>>>> > we
>>>>>>> > > >> are
>>>>>>> > > >>>>>>>> profiling the time spent on .next() method (time to
>>>>>>> consume) and
>>>>>>> > > the
>>>>>>> > > >>>>> time
>>>>>>> > > >>>>>>>> spent on .collect() method (time to emit / process). One
>>>>>>> > advantage
>>>>>>> > > >> of
>>>>>>> > > >>>>>>> such
>>>>>>> > > >>>>>>>> method level time cost allows us to calculate the
>>>>>>> parallelism
>>>>>>> > > >>>>> required to
>>>>>>> > > >>>>>>>> keep up in case their is a lag.
>>>>>>> > > >>>>>>>>
>>>>>>> > > >>>>>>>> However, one concern I have regarding such metric is
>>>>>>> that they
>>>>>>> > are
>>>>>>> > > >>>>>>>> implementation specific. Either profiling on the method
>>>>>>> time, or
>>>>>>> > > >>>>>>> reporting
>>>>>>> > > >>>>>>>> buffer usage assumes the connector are implemented in
>>>>>>> such a
>>>>>>> > way.
>>>>>>> > > A
>>>>>>> > > >>>>>>>> slightly better solution might be have the following
>>>>>>> metric:
>>>>>>> > > >>>>>>>>
>>>>>>> > > >>>>>>>> - EmitTimeRatio (or FetchTimeRatio): The time spent on
>>>>>>> emitting
>>>>>>> > > >>>>>>>> records / Total time elapsed.
>>>>>>> > > >>>>>>>>
>>>>>>> > > >>>>>>>> This assumes that the source connectors have to emit
>>>>>>> the records
>>>>>>> > > to
>>>>>>> > > >>>>> the
>>>>>>> > > >>>>>>>> downstream at some point. The emission may take some
>>>>>>> time ( e.g.
>>>>>>> > > go
>>>>>>> > > >>>>>>> through
>>>>>>> > > >>>>>>>> chained operators). And the rest of the time are spent
>>>>>>> to
>>>>>>> > prepare
>>>>>>> > > >> the
>>>>>>> > > >>>>>>>> record to emit, including time for consuming and format
>>>>>>> > > conversion,
>>>>>>> > > >>>>> etc.
>>>>>>> > > >>>>>>>> Ideally, we'd like to see the time spent on record
>>>>>>> fetch and
>>>>>>> > emit
>>>>>>> > > to
>>>>>>> > > >>>>> be
>>>>>>> > > >>>>>>>> about the same, so no one is bottleneck for the other.
>>>>>>> > > >>>>>>>>
>>>>>>> > > >>>>>>>> The downside of these time based metrics is additional
>>>>>>> overhead
>>>>>>> > to
>>>>>>> > > >> get
>>>>>>> > > >>>>>>> the
>>>>>>> > > >>>>>>>> time, therefore sampling might be needed. But in
>>>>>>> practice I feel
>>>>>>> > > >> such
>>>>>>> > > >>>>>>> time
>>>>>>> > > >>>>>>>> based metric might be more useful if we want to take
>>>>>>> action.
>>>>>>> > > >>>>>>>>
>>>>>>> > > >>>>>>>>
>>>>>>> > > >>>>>>>> I think we should absolutely add metrics in (1) to the
>>>>>>> metric
>>>>>>> > > >>>>> convention.
>>>>>>> > > >>>>>>>> We could also add the metrics mentioned in (2) if we
>>>>>>> reach
>>>>>>> > > consensus
>>>>>>> > > >>>>> on
>>>>>>> > > >>>>>>>> that. What do you think?
>>>>>>> > > >>>>>>>>
>>>>>>> > > >>>>>>>> Thanks,
>>>>>>> > > >>>>>>>>
>>>>>>> > > >>>>>>>> Jiangjie (Becket) Qin
>>>>>>> > > >>>>>>>>
>>>>>>> > > >>>>>>>>
>>>>>>> > > >>>>>>>> On Fri, May 31, 2019 at 4:26 PM Piotr Nowojski <
>>>>>>> > > piotr@ververica.com
>>>>>>> > > >>>
>>>>>>> > > >>>>>>> wrote:
>>>>>>> > > >>>>>>>>
>>>>>>> > > >>>>>>>>> Hey Becket,
>>>>>>> > > >>>>>>>>>
>>>>>>> > > >>>>>>>>> Re 1a) and 1b) +1 from my side.
>>>>>>> > > >>>>>>>>>
>>>>>>> > > >>>>>>>>> I’ve discussed this issue:
>>>>>>> > > >>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>> 2. It would be nice to have metrics, that allow us
>>>>>>> to check
>>>>>>> > > the
>>>>>>> > > >>>>> cause
>>>>>>> > > >>>>>>>>> of
>>>>>>> > > >>>>>>>>>>>> back pressure:
>>>>>>> > > >>>>>>>>>>>> a) for sources, length of input queue (in bytes? Or
>>>>>>> boolean
>>>>>>> > > >>>>>>>>>>>> hasSomethingl/isEmpty)
>>>>>>> > > >>>>>>>>>>>> b) for sinks, length of output queue (in bytes? Or
>>>>>>> boolean
>>>>>>> > > >>>>>>>>>>>> hasSomething/isEmpty)
>>>>>>> > > >>>>>>>>>
>>>>>>> > > >>>>>>>>> With Nico at some lengths and he also saw the benefits
>>>>>>> of them.
>>>>>>> > > We
>>>>>>> > > >>>>> also
>>>>>>> > > >>>>>>>>> have more concrete proposal for that.
>>>>>>> > > >>>>>>>>>
>>>>>>> > > >>>>>>>>> Actually there are two really useful metrics, that we
>>>>>>> are
>>>>>>> > missing
>>>>>>> > > >>>>>>>>> currently:
>>>>>>> > > >>>>>>>>>
>>>>>>> > > >>>>>>>>> 1. Number of data/records/bytes in the backlog to
>>>>>>> process. For
>>>>>>> > > >>>>> example
>>>>>>> > > >>>>>>>>> remaining number of bytes in unread files. Or pending
>>>>>>> data in
>>>>>>> > > Kafka
>>>>>>> > > >>>>>>> topics.
>>>>>>> > > >>>>>>>>> 2. Number of buffered data in-memory of the connector,
>>>>>>> that are
>>>>>>> > > >>>>> waiting
>>>>>>> > > >>>>>>> to
>>>>>>> > > >>>>>>>>> be processed pushed to Flink pipeline.
>>>>>>> > > >>>>>>>>>
>>>>>>> > > >>>>>>>>> Re 1:
>>>>>>> > > >>>>>>>>> This would have to be a metric provided directly by a
>>>>>>> > connector.
>>>>>>> > > It
>>>>>>> > > >>>>>>> could
>>>>>>> > > >>>>>>>>> be an undefined `int`:
>>>>>>> > > >>>>>>>>>
>>>>>>> > > >>>>>>>>> `int backlog` - estimate of pending work.
>>>>>>> > > >>>>>>>>>
>>>>>>> > > >>>>>>>>> “Undefined” meaning that it would be up to a connector
>>>>>>> to
>>>>>>> > decided
>>>>>>> > > >>>>>>> whether
>>>>>>> > > >>>>>>>>> it’s measured in bytes, records, pending files or
>>>>>>> whatever it
>>>>>>> > is
>>>>>>> > > >>>>>>> possible
>>>>>>> > > >>>>>>>>> to provide by the connector. This is because I assume
>>>>>>> not every
>>>>>>> > > >>>>>>> connector
>>>>>>> > > >>>>>>>>> can provide exact number and for some of them it might
>>>>>>> be
>>>>>>> > > >> impossible
>>>>>>> > > >>>>> to
>>>>>>> > > >>>>>>>>> provide records number of bytes count.
>>>>>>> > > >>>>>>>>>
>>>>>>> > > >>>>>>>>> Re 2:
>>>>>>> > > >>>>>>>>> This metric could be either provided by a connector, or
>>>>>>> > > calculated
>>>>>>> > > >>>>>>> crudely
>>>>>>> > > >>>>>>>>> by Flink:
>>>>>>> > > >>>>>>>>>
>>>>>>> > > >>>>>>>>> `float bufferUsage` - value from [0.0, 1.0] range
>>>>>>> > > >>>>>>>>>
>>>>>>> > > >>>>>>>>> Percentage of used in memory buffers, like in Kafka’s
>>>>>>> handover.
>>>>>>> > > >>>>>>>>>
>>>>>>> > > >>>>>>>>> It could be crudely implemented by Flink with FLIP-27
>>>>>>> > > >>>>>>>>> SourceReader#isAvailable. If SourceReader is not
>>>>>>> available
>>>>>>> > > reported
>>>>>>> > > >>>>>>>>> `bufferUsage` could be 0.0. If it is available, it
>>>>>>> could be
>>>>>>> > 1.0.
>>>>>>> > > I
>>>>>>> > > >>>>> think
>>>>>>> > > >>>>>>>>> this would be a good enough estimation for most of the
>>>>>>> use
>>>>>>> > cases
>>>>>>> > > >>>>> (that
>>>>>>> > > >>>>>>>>> could be overloaded and implemented better if desired).
>>>>>>> > > Especially
>>>>>>> > > >>>>>>> since we
>>>>>>> > > >>>>>>>>> are reporting only probed values: if probed values are
>>>>>>> almost
>>>>>>> > > >> always
>>>>>>> > > >>>>>>> “1.0”,
>>>>>>> > > >>>>>>>>> it would mean that we have a back pressure. If they
>>>>>>> are almost
>>>>>>> > > >> always
>>>>>>> > > >>>>>>>>> “0.0”, there is probably no back pressure at the
>>>>>>> sources.
>>>>>>> > > >>>>>>>>>
>>>>>>> > > >>>>>>>>> What do you think about this?
>>>>>>> > > >>>>>>>>>
>>>>>>> > > >>>>>>>>> Piotrek
>>>>>>> > > >>>>>>>>>
>>>>>>> > > >>>>>>>>>> On 30 May 2019, at 11:41, Becket Qin <
>>>>>>> becket.qin@gmail.com>
>>>>>>> > > >> wrote:
>>>>>>> > > >>>>>>>>>>
>>>>>>> > > >>>>>>>>>> Hi all,
>>>>>>> > > >>>>>>>>>>
>>>>>>> > > >>>>>>>>>> Thanks a lot for all the feedback and comments. I'd
>>>>>>> like to
>>>>>>> > > >> continue
>>>>>>> > > >>>>>>> the
>>>>>>> > > >>>>>>>>>> discussion on this FLIP.
>>>>>>> > > >>>>>>>>>>
>>>>>>> > > >>>>>>>>>> I updated the FLIP-33 wiki to remove all the
>>>>>>> histogram metrics
>>>>>>> > > >> from
>>>>>>> > > >>>>> the
>>>>>>> > > >>>>>>>>>> first version of metric convention due to the
>>>>>>> performance
>>>>>>> > > concern.
>>>>>>> > > >>>>> The
>>>>>>> > > >>>>>>>>> plan
>>>>>>> > > >>>>>>>>>> is to introduce them later when we have a mechanism
>>>>>>> to opt
>>>>>>> > > in/out
>>>>>>> > > >>>>>>>>> metrics.
>>>>>>> > > >>>>>>>>>> At that point, users can decide whether they want to
>>>>>>> pay the
>>>>>>> > > cost
>>>>>>> > > >> to
>>>>>>> > > >>>>>>> get
>>>>>>> > > >>>>>>>>>> the metric or not.
>>>>>>> > > >>>>>>>>>>
>>>>>>> > > >>>>>>>>>> As Stephan suggested, for this FLIP, let's first try
>>>>>>> to agree
>>>>>>> > on
>>>>>>> > > >> the
>>>>>>> > > >>>>>>>>> small
>>>>>>> > > >>>>>>>>>> list of conventional metrics that connectors should
>>>>>>> follow.
>>>>>>> > > >>>>>>>>>> Just to be clear, the purpose of the convention is
>>>>>>> not to
>>>>>>> > > enforce
>>>>>>> > > >>>>> every
>>>>>>> > > >>>>>>>>>> connector to report all these metrics, but to provide
>>>>>>> a
>>>>>>> > guidance
>>>>>>> > > >> in
>>>>>>> > > >>>>>>> case
>>>>>>> > > >>>>>>>>>> these metrics are reported by some connectors.
>>>>>>> > > >>>>>>>>>>
>>>>>>> > > >>>>>>>>>>
>>>>>>> > > >>>>>>>>>> @ Stephan & Chesnay,
>>>>>>> > > >>>>>>>>>>
>>>>>>> > > >>>>>>>>>> Regarding the duplication of `RecordsIn` metric in
>>>>>>> operator /
>>>>>>> > > task
>>>>>>> > > >>>>>>>>>> IOMetricGroups, from what I understand, for source
>>>>>>> operator,
>>>>>>> > it
>>>>>>> > > is
>>>>>>> > > >>>>>>>>> actually
>>>>>>> > > >>>>>>>>>> the SourceFunction that reports the operator level
>>>>>>> > > >>>>>>>>>> RecordsIn/RecordsInPerSecond metric. So they are
>>>>>>> essentially
>>>>>>> > the
>>>>>>> > > >>>>> same
>>>>>>> > > >>>>>>>>>> metric in the operator level IOMetricGroup. Similarly
>>>>>>> for the
>>>>>>> > > Sink
>>>>>>> > > >>>>>>>>>> operator, the operator level
>>>>>>> RecordsOut/RecordsOutPerSecond
>>>>>>> > > >> metrics
>>>>>>> > > >>>>> are
>>>>>>> > > >>>>>>>>>> also reported by the Sink function. I marked them as
>>>>>>> existing
>>>>>>> > in
>>>>>>> > > >> the
>>>>>>> > > >>>>>>>>>> FLIP-33 wiki page. Please let me know if I
>>>>>>> misunderstood.
>>>>>>> > > >>>>>>>>>>
>>>>>>> > > >>>>>>>>>> Thanks,
>>>>>>> > > >>>>>>>>>>
>>>>>>> > > >>>>>>>>>> Jiangjie (Becket) Qin
>>>>>>> > > >>>>>>>>>>
>>>>>>> > > >>>>>>>>>>
>>>>>>> > > >>>>>>>>>> On Thu, May 30, 2019 at 5:16 PM Becket Qin <
>>>>>>> > > becket.qin@gmail.com>
>>>>>>> > > >>>>>>> wrote:
>>>>>>> > > >>>>>>>>>>
>>>>>>> > > >>>>>>>>>>> Hi Piotr,
>>>>>>> > > >>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>> Thanks a lot for the feedback.
>>>>>>> > > >>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>> 1a) I guess you are referring to the part that
>>>>>>> "original
>>>>>>> > system
>>>>>>> > > >>>>>>> specific
>>>>>>> > > >>>>>>>>>>> metrics should also be reported". The performance
>>>>>>> impact
>>>>>>> > > depends
>>>>>>> > > >> on
>>>>>>> > > >>>>>>> the
>>>>>>> > > >>>>>>>>>>> implementation. An efficient implementation would
>>>>>>> only record
>>>>>>> > > the
>>>>>>> > > >>>>>>> metric
>>>>>>> > > >>>>>>>>>>> once, but report them with two different metric
>>>>>>> names. This
>>>>>>> > is
>>>>>>> > > >>>>>>> unlikely
>>>>>>> > > >>>>>>>>> to
>>>>>>> > > >>>>>>>>>>> hurt performance.
>>>>>>> > > >>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>> 1b) Yes, I agree that we should avoid adding
>>>>>>> overhead to the
>>>>>>> > > >>>>> critical
>>>>>>> > > >>>>>>>>> path
>>>>>>> > > >>>>>>>>>>> by all means. This is sometimes a tradeoff, running
>>>>>>> blindly
>>>>>>> > > >> without
>>>>>>> > > >>>>>>> any
>>>>>>> > > >>>>>>>>>>> metric gives best performance, but sometimes might be
>>>>>>> > > frustrating
>>>>>>> > > >>>>> when
>>>>>>> > > >>>>>>>>> we
>>>>>>> > > >>>>>>>>>>> debug some issues.
>>>>>>> > > >>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>> 2. The metrics are indeed very useful. Are they
>>>>>>> supposed to
>>>>>>> > be
>>>>>>> > > >>>>>>> reported
>>>>>>> > > >>>>>>>>> by
>>>>>>> > > >>>>>>>>>>> the connectors or Flink itself? At this point
>>>>>>> FLIP-33 is more
>>>>>>> > > >>>>> focused
>>>>>>> > > >>>>>>> on
>>>>>>> > > >>>>>>>>>>> provide a guidance to the connector authors on the
>>>>>>> metrics
>>>>>>> > > >>>>> reporting.
>>>>>>> > > >>>>>>>>> That
>>>>>>> > > >>>>>>>>>>> said, after FLIP-27, I think we should absolutely
>>>>>>> report
>>>>>>> > these
>>>>>>> > > >>>>> metrics
>>>>>>> > > >>>>>>>>> in
>>>>>>> > > >>>>>>>>>>> the abstract implementation. In any case, the metric
>>>>>>> > convention
>>>>>>> > > >> in
>>>>>>> > > >>>>>>> this
>>>>>>> > > >>>>>>>>>>> list are expected to evolve over time.
>>>>>>> > > >>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>> Thanks,
>>>>>>> > > >>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>> Jiangjie (Becket) Qin
>>>>>>> > > >>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>> On Tue, May 28, 2019 at 6:24 PM Piotr Nowojski <
>>>>>>> > > >>>>> piotr@ververica.com>
>>>>>>> > > >>>>>>>>>>> wrote:
>>>>>>> > > >>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>> Hi,
>>>>>>> > > >>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>> Thanks for the proposal and driving the effort here
>>>>>>> Becket
>>>>>>> > :)
>>>>>>> > > >> I’ve
>>>>>>> > > >>>>>>> read
>>>>>>> > > >>>>>>>>>>>> through the FLIP-33 [1], and here are couple of my
>>>>>>> thoughts.
>>>>>>> > > >>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>> Big +1 for standardising the metric names between
>>>>>>> > connectors,
>>>>>>> > > it
>>>>>>> > > >>>>> will
>>>>>>> > > >>>>>>>>>>>> definitely help us and users a lot.
>>>>>>> > > >>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>> Issues/questions/things to discuss that I’ve
>>>>>>> thought of:
>>>>>>> > > >>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>> 1a. If we are about to duplicate some metrics, can
>>>>>>> this
>>>>>>> > > become a
>>>>>>> > > >>>>>>>>>>>> performance issue?
>>>>>>> > > >>>>>>>>>>>> 1b. Generally speaking, we should make sure that
>>>>>>> collecting
>>>>>>> > > >> those
>>>>>>> > > >>>>>>>>> metrics
>>>>>>> > > >>>>>>>>>>>> is as non intrusive as possible, especially that
>>>>>>> they will
>>>>>>> > > need
>>>>>>> > > >>>>> to be
>>>>>>> > > >>>>>>>>>>>> updated once per record. (They might be collected
>>>>>>> more
>>>>>>> > rarely
>>>>>>> > > >> with
>>>>>>> > > >>>>>>> some
>>>>>>> > > >>>>>>>>>>>> overhead, but the hot path of updating it per
>>>>>>> record will
>>>>>>> > need
>>>>>>> > > >> to
>>>>>>> > > >>>>> be
>>>>>>> > > >>>>>>> as
>>>>>>> > > >>>>>>>>>>>> quick as possible). That includes both avoiding
>>>>>>> heavy
>>>>>>> > > >> computation
>>>>>>> > > >>>>> on
>>>>>>> > > >>>>>>>>> per
>>>>>>> > > >>>>>>>>>>>> record path: histograms?, measuring time for time
>>>>>>> based
>>>>>>> > > metrics
>>>>>>> > > >>>>> (per
>>>>>>> > > >>>>>>>>>>>> second) (System.currentTimeMillis() depending on the
>>>>>>> > > >>>>> implementation
>>>>>>> > > >>>>>>> can
>>>>>>> > > >>>>>>>>>>>> invoke a system call)
>>>>>>> > > >>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>> 2. It would be nice to have metrics, that allow us
>>>>>>> to check
>>>>>>> > > the
>>>>>>> > > >>>>> cause
>>>>>>> > > >>>>>>>>> of
>>>>>>> > > >>>>>>>>>>>> back pressure:
>>>>>>> > > >>>>>>>>>>>> a) for sources, length of input queue (in bytes? Or
>>>>>>> boolean
>>>>>>> > > >>>>>>>>>>>> hasSomethingl/isEmpty)
>>>>>>> > > >>>>>>>>>>>> b) for sinks, length of output queue (in bytes? Or
>>>>>>> boolean
>>>>>>> > > >>>>>>>>>>>> hasSomething/isEmpty)
>>>>>>> > > >>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>> a) is useful in a scenario when we are processing
>>>>>>> backlog of
>>>>>>> > > >>>>> records,
>>>>>>> > > >>>>>>>>> all
>>>>>>> > > >>>>>>>>>>>> of the internal Flink’s input/output network
>>>>>>> buffers are
>>>>>>> > > empty,
>>>>>>> > > >>>>> and
>>>>>>> > > >>>>>>> we
>>>>>>> > > >>>>>>>>> want
>>>>>>> > > >>>>>>>>>>>> to check whether the external source system is the
>>>>>>> > bottleneck
>>>>>>> > > >>>>>>> (source’s
>>>>>>> > > >>>>>>>>>>>> input queue will be empty), or if the Flink’s
>>>>>>> connector is
>>>>>>> > the
>>>>>>> > > >>>>>>>>> bottleneck
>>>>>>> > > >>>>>>>>>>>> (source’s input queues will be full).
>>>>>>> > > >>>>>>>>>>>> b) similar story. Backlog of records, but this time
>>>>>>> all of
>>>>>>> > the
>>>>>>> > > >>>>>>> internal
>>>>>>> > > >>>>>>>>>>>> Flink’s input/ouput network buffers are full, and
>>>>>>> we want o
>>>>>>> > > >> check
>>>>>>> > > >>>>>>>>> whether
>>>>>>> > > >>>>>>>>>>>> the external sink system is the bottleneck (sink
>>>>>>> output
>>>>>>> > queues
>>>>>>> > > >> are
>>>>>>> > > >>>>>>>>> full),
>>>>>>> > > >>>>>>>>>>>> or if the Flink’s connector is the bottleneck
>>>>>>> (sink’s output
>>>>>>> > > >>>>> queues
>>>>>>> > > >>>>>>>>> will be
>>>>>>> > > >>>>>>>>>>>> empty)
>>>>>>> > > >>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>> It might be sometimes difficult to provide those
>>>>>>> metrics, so
>>>>>>> > > >> they
>>>>>>> > > >>>>>>> could
>>>>>>> > > >>>>>>>>>>>> be optional, but if we could provide them, it would
>>>>>>> be
>>>>>>> > really
>>>>>>> > > >>>>>>> helpful.
>>>>>>> > > >>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>> Piotrek
>>>>>>> > > >>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>> [1]
>>>>>>> > > >>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>
>>>>>>> > > >>>>>>>
>>>>>>> > > >>>>>
>>>>>>> > > >>
>>>>>>> > >
>>>>>>> >
>>>>>>> https://cwiki.apache.org/confluence/display/FLINK/FLIP-33:+Standardize+Connector+Metrics
>>>>>>> > > >>>>>>>>>>>> <
>>>>>>> > > >>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>
>>>>>>> > > >>>>>>>
>>>>>>> > > >>>>>
>>>>>>> > > >>
>>>>>>> > >
>>>>>>> >
>>>>>>> https://cwiki.apache.org/confluence/display/FLINK/FLIP-33:+Standardize+Connector+Metrics
>>>>>>> > > >>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>> On 24 Apr 2019, at 13:28, Stephan Ewen <
>>>>>>> sewen@apache.org>
>>>>>>> > > >> wrote:
>>>>>>> > > >>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>> I think this sounds reasonable.
>>>>>>> > > >>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>> Let's keep the "reconfiguration without stopping
>>>>>>> the job"
>>>>>>> > out
>>>>>>> > > >> of
>>>>>>> > > >>>>>>> this,
>>>>>>> > > >>>>>>>>>>>>> because that would be a super big effort and if we
>>>>>>> approach
>>>>>>> > > >> that,
>>>>>>> > > >>>>>>> then
>>>>>>> > > >>>>>>>>>>>> in
>>>>>>> > > >>>>>>>>>>>>> more generic way rather than specific to connector
>>>>>>> metrics.
>>>>>>> > > >>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>> I would suggest to look at the following things
>>>>>>> before
>>>>>>> > > starting
>>>>>>> > > >>>>> with
>>>>>>> > > >>>>>>>>> any
>>>>>>> > > >>>>>>>>>>>>> implementation work:
>>>>>>> > > >>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>> - Try and find a committer to support this,
>>>>>>> otherwise it
>>>>>>> > will
>>>>>>> > > >> be
>>>>>>> > > >>>>>>> hard
>>>>>>> > > >>>>>>>>>>>> to
>>>>>>> > > >>>>>>>>>>>>> make progress
>>>>>>> > > >>>>>>>>>>>>> - Start with defining a smaller set of "core
>>>>>>> metrics" and
>>>>>>> > > >> extend
>>>>>>> > > >>>>> the
>>>>>>> > > >>>>>>>>>>>> set
>>>>>>> > > >>>>>>>>>>>>> later. I think that is easier than now blocking on
>>>>>>> reaching
>>>>>>> > > >>>>>>> consensus
>>>>>>> > > >>>>>>>>>>>> on a
>>>>>>> > > >>>>>>>>>>>>> large group of metrics.
>>>>>>> > > >>>>>>>>>>>>> - Find a solution to the problem Chesnay
>>>>>>> mentioned, that
>>>>>>> > the
>>>>>>> > > >>>>>>> "records
>>>>>>> > > >>>>>>>>>>>> in"
>>>>>>> > > >>>>>>>>>>>>> metric is somehow overloaded and exists already in
>>>>>>> the IO
>>>>>>> > > >> Metric
>>>>>>> > > >>>>>>>>> group.
>>>>>>> > > >>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>> On Mon, Mar 25, 2019 at 7:16 AM Becket Qin <
>>>>>>> > > >> becket.qin@gmail.com
>>>>>>> > > >>>>>>
>>>>>>> > > >>>>>>>>>>>> wrote:
>>>>>>> > > >>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>> Hi Stephan,
>>>>>>> > > >>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>> Thanks a lot for the feedback. All makes sense.
>>>>>>> > > >>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>> It is a good suggestion to simply have an
>>>>>>> > onRecord(numBytes,
>>>>>>> > > >>>>>>>>> eventTime)
>>>>>>> > > >>>>>>>>>>>>>> method for connector writers. It should meet most
>>>>>>> of the
>>>>>>> > > >>>>>>>>> requirements,
>>>>>>> > > >>>>>>>>>>>>>> individual
>>>>>>> > > >>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>> The configurable metrics feature is something
>>>>>>> really
>>>>>>> > useful,
>>>>>>> > > >>>>>>>>>>>> especially if
>>>>>>> > > >>>>>>>>>>>>>> we can somehow make it dynamically configurable
>>>>>>> without
>>>>>>> > > >> stopping
>>>>>>> > > >>>>>>> the
>>>>>>> > > >>>>>>>>>>>> jobs.
>>>>>>> > > >>>>>>>>>>>>>> It might be better to make it a separate
>>>>>>> discussion
>>>>>>> > because
>>>>>>> > > it
>>>>>>> > > >>>>> is a
>>>>>>> > > >>>>>>>>>>>> more
>>>>>>> > > >>>>>>>>>>>>>> generic feature instead of only for connectors.
>>>>>>> > > >>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>> So in order to make some progress, in this FLIP
>>>>>>> we can
>>>>>>> > limit
>>>>>>> > > >> the
>>>>>>> > > >>>>>>>>>>>> discussion
>>>>>>> > > >>>>>>>>>>>>>> scope to the connector related items:
>>>>>>> > > >>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>> - the standard connector metric names and types.
>>>>>>> > > >>>>>>>>>>>>>> - the abstract ConnectorMetricHandler interface
>>>>>>> > > >>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>> I'll start a separate thread to discuss other
>>>>>>> general
>>>>>>> > metric
>>>>>>> > > >>>>>>> related
>>>>>>> > > >>>>>>>>>>>>>> enhancement items including:
>>>>>>> > > >>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>> - optional metrics
>>>>>>> > > >>>>>>>>>>>>>> - dynamic metric configuration
>>>>>>> > > >>>>>>>>>>>>>> - potential combination with rate limiter
>>>>>>> > > >>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>> Does this plan sound reasonable?
>>>>>>> > > >>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>> Thanks,
>>>>>>> > > >>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>> Jiangjie (Becket) Qin
>>>>>>> > > >>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>> On Sat, Mar 23, 2019 at 5:53 AM Stephan Ewen <
>>>>>>> > > >> sewen@apache.org>
>>>>>>> > > >>>>>>>>> wrote:
>>>>>>> > > >>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>> Ignoring for a moment implementation details,
>>>>>>> this
>>>>>>> > > connector
>>>>>>> > > >>>>>>> metrics
>>>>>>> > > >>>>>>>>>>>> work
>>>>>>> > > >>>>>>>>>>>>>>> is a really good thing to do, in my opinion
>>>>>>> > > >>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>> The questions "oh, my job seems to be doing
>>>>>>> nothing, I am
>>>>>>> > > >>>>> looking
>>>>>>> > > >>>>>>> at
>>>>>>> > > >>>>>>>>>>>> the
>>>>>>> > > >>>>>>>>>>>>>> UI
>>>>>>> > > >>>>>>>>>>>>>>> and the 'records in' value is still zero" is in
>>>>>>> the top
>>>>>>> > > three
>>>>>>> > > >>>>>>>>> support
>>>>>>> > > >>>>>>>>>>>>>>> questions I have been asked personally.
>>>>>>> > > >>>>>>>>>>>>>>> Introspection into "how far is the consumer
>>>>>>> lagging
>>>>>>> > behind"
>>>>>>> > > >>>>> (event
>>>>>>> > > >>>>>>>>>>>> time
>>>>>>> > > >>>>>>>>>>>>>>> fetch latency) came up many times as well.
>>>>>>> > > >>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>> So big +1 to solving this problem.
>>>>>>> > > >>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>> About the exact design - I would try to go for
>>>>>>> the
>>>>>>> > > following
>>>>>>> > > >>>>>>>>>>>> properties:
>>>>>>> > > >>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>> - keep complexity of of connectors. Ideally the
>>>>>>> metrics
>>>>>>> > > >> handler
>>>>>>> > > >>>>>>> has
>>>>>>> > > >>>>>>>>> a
>>>>>>> > > >>>>>>>>>>>>>>> single onRecord(numBytes, eventTime) method or
>>>>>>> so, and
>>>>>>> > > >>>>> everything
>>>>>>> > > >>>>>>>>>>>> else is
>>>>>>> > > >>>>>>>>>>>>>>> internal to the handler. That makes it dead
>>>>>>> simple for
>>>>>>> > the
>>>>>>> > > >>>>>>>>> connector.
>>>>>>> > > >>>>>>>>>>>> We
>>>>>>> > > >>>>>>>>>>>>>>> can also think of an extensive scheme for
>>>>>>> connector
>>>>>>> > > specific
>>>>>>> > > >>>>>>>>> metrics.
>>>>>>> > > >>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>> - make it configurable on the job it cluster
>>>>>>> level which
>>>>>>> > > >>>>> metrics
>>>>>>> > > >>>>>>> the
>>>>>>> > > >>>>>>>>>>>>>>> handler internally creates when that method is
>>>>>>> invoked.
>>>>>>> > > >>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>> What do you think?
>>>>>>> > > >>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>> Best,
>>>>>>> > > >>>>>>>>>>>>>>> Stephan
>>>>>>> > > >>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>> On Thu, Mar 21, 2019 at 10:42 AM Chesnay
>>>>>>> Schepler <
>>>>>>> > > >>>>>>>>> chesnay@apache.org
>>>>>>> > > >>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>> wrote:
>>>>>>> > > >>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>> As I said before, I believe this to be
>>>>>>> over-engineered
>>>>>>> > and
>>>>>>> > > >>>>> have
>>>>>>> > > >>>>>>> no
>>>>>>> > > >>>>>>>>>>>>>>>> interest in this implementation.
>>>>>>> > > >>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>> There are conceptual issues like defining a
>>>>>>> duplicate
>>>>>>> > > >>>>>>>>>>>>>> numBytesIn(PerSec)
>>>>>>> > > >>>>>>>>>>>>>>>> metric that already exists for each operator.
>>>>>>> > > >>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>> On 21.03.2019 06:13, Becket Qin wrote:
>>>>>>> > > >>>>>>>>>>>>>>>>> A few updates to the thread. I uploaded a
>>>>>>> patch[1] as a
>>>>>>> > > >>>>> complete
>>>>>>> > > >>>>>>>>>>>>>>>>> example of how users can use the metrics in
>>>>>>> the future.
>>>>>>> > > >>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>> Some thoughts below after taking a look at the
>>>>>>> > > >>>>>>> AbstractMetricGroup
>>>>>>> > > >>>>>>>>>>>>>> and
>>>>>>> > > >>>>>>>>>>>>>>>>> its subclasses.
>>>>>>> > > >>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>> This patch intends to provide convenience for
>>>>>>> Flink
>>>>>>> > > >> connector
>>>>>>> > > >>>>>>>>>>>>>>>>> implementations to follow metrics standards
>>>>>>> proposed in
>>>>>>> > > >>>>> FLIP-33.
>>>>>>> > > >>>>>>>>> It
>>>>>>> > > >>>>>>>>>>>>>>>>> also try to enhance the metric management in
>>>>>>> general
>>>>>>> > way
>>>>>>> > > to
>>>>>>> > > >>>>> help
>>>>>>> > > >>>>>>>>>>>>>> users
>>>>>>> > > >>>>>>>>>>>>>>>>> with:
>>>>>>> > > >>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>> 1. metric definition
>>>>>>> > > >>>>>>>>>>>>>>>>> 2. metric dependencies check
>>>>>>> > > >>>>>>>>>>>>>>>>> 3. metric validation
>>>>>>> > > >>>>>>>>>>>>>>>>> 4. metric control (turn on / off particular
>>>>>>> metrics)
>>>>>>> > > >>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>> This patch wraps |MetricGroup| to extend the
>>>>>>> > > functionality
>>>>>>> > > >> of
>>>>>>> > > >>>>>>>>>>>>>>>>> |AbstractMetricGroup| and its subclasses. The
>>>>>>> > > >>>>>>>>>>>>>>>>> |AbstractMetricGroup| mainly focus on the
>>>>>>> metric group
>>>>>>> > > >>>>>>> hierarchy,
>>>>>>> > > >>>>>>>>>>>> but
>>>>>>> > > >>>>>>>>>>>>>>>>> does not really manage the metrics other than
>>>>>>> keeping
>>>>>>> > > them
>>>>>>> > > >>>>> in a
>>>>>>> > > >>>>>>>>> Map.
>>>>>>> > > >>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>> Ideally we should only have one entry point
>>>>>>> for the
>>>>>>> > > >> metrics.
>>>>>>> > > >>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>> Right now the entry point is
>>>>>>> |AbstractMetricGroup|.
>>>>>>> > > >> However,
>>>>>>> > > >>>>>>>>> besides
>>>>>>> > > >>>>>>>>>>>>>>>>> the missing functionality mentioned above,
>>>>>>> > > >>>>> |AbstractMetricGroup|
>>>>>>> > > >>>>>>>>>>>>>> seems
>>>>>>> > > >>>>>>>>>>>>>>>>> deeply rooted in Flink runtime. We could
>>>>>>> extract it out
>>>>>>> > > to
>>>>>>> > > >>>>>>>>>>>>>>>>> flink-metrics in order to use it for generic
>>>>>>> purpose.
>>>>>>> > > There
>>>>>>> > > >>>>> will
>>>>>>> > > >>>>>>>>> be
>>>>>>> > > >>>>>>>>>>>>>>>>> some work, though.
>>>>>>> > > >>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>> Another approach is to make |AbstractMetrics|
>>>>>>> in this
>>>>>>> > > patch
>>>>>>> > > >>>>> as
>>>>>>> > > >>>>>>> the
>>>>>>> > > >>>>>>>>>>>>>>>>> metric entry point. It wraps metric group and
>>>>>>> provides
>>>>>>> > > the
>>>>>>> > > >>>>>>> missing
>>>>>>> > > >>>>>>>>>>>>>>>>> functionalities. Then we can roll out this
>>>>>>> pattern to
>>>>>>> > > >> runtime
>>>>>>> > > >>>>>>>>>>>>>>>>> components gradually as well.
>>>>>>> > > >>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>> My first thought is that the latter approach
>>>>>>> gives a
>>>>>>> > more
>>>>>>> > > >>>>> smooth
>>>>>>> > > >>>>>>>>>>>>>>>>> migration. But I am also OK with doing a
>>>>>>> refactoring on
>>>>>>> > > the
>>>>>>> > > >>>>>>>>>>>>>>>>> |AbstractMetricGroup| family.
>>>>>>> > > >>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>> Thanks,
>>>>>>> > > >>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>> Jiangjie (Becket) Qin
>>>>>>> > > >>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>> [1] https://github.com/becketqin/flink/pull/1
>>>>>>> > > >>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>> On Mon, Feb 25, 2019 at 2:32 PM Becket Qin <
>>>>>>> > > >>>>>>> becket.qin@gmail.com
>>>>>>> > > >>>>>>>>>>>>>>>>> <ma...@gmail.com>> wrote:
>>>>>>> > > >>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>> Hi Chesnay,
>>>>>>> > > >>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>> It might be easier to discuss some
>>>>>>> implementation
>>>>>>> > details
>>>>>>> > > >> in
>>>>>>> > > >>>>>>> the
>>>>>>> > > >>>>>>>>>>>>>>>>> PR review instead of in the FLIP discussion
>>>>>>> thread. I
>>>>>>> > > have
>>>>>>> > > >> a
>>>>>>> > > >>>>>>>>>>>>>> patch
>>>>>>> > > >>>>>>>>>>>>>>>>> for Kafka connectors ready but haven't
>>>>>>> submitted the PR
>>>>>>> > > >> yet.
>>>>>>> > > >>>>>>>>>>>>>>>>> Hopefully that will help explain a bit more.
>>>>>>> > > >>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>> ** Re: metric type binding
>>>>>>> > > >>>>>>>>>>>>>>>>> This is a valid point that worths discussing.
>>>>>>> If I
>>>>>>> > > >> understand
>>>>>>> > > >>>>>>>>>>>>>>>>> correctly, there are two points:
>>>>>>> > > >>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>> 1. Metric type / interface does not matter as
>>>>>>> long as
>>>>>>> > the
>>>>>>> > > >>>>>>> metric
>>>>>>> > > >>>>>>>>>>>>>>>>> semantic is clearly defined.
>>>>>>> > > >>>>>>>>>>>>>>>>> Conceptually speaking, I agree that as long as
>>>>>>> the
>>>>>>> > metric
>>>>>>> > > >>>>>>>>>>>>>> semantic
>>>>>>> > > >>>>>>>>>>>>>>>>> is defined, metric type does not matter. To
>>>>>>> some
>>>>>>> > extent,
>>>>>>> > > >>>>> Gauge
>>>>>>> > > >>>>>>> /
>>>>>>> > > >>>>>>>>>>>>>>>>> Counter / Meter / Histogram themselves can be
>>>>>>> think of
>>>>>>> > as
>>>>>>> > > >>>>> some
>>>>>>> > > >>>>>>>>>>>>>>>>> well-recognized semantics, if you wish. In
>>>>>>> Flink, these
>>>>>>> > > >>>>> metric
>>>>>>> > > >>>>>>>>>>>>>>>>> semantics have their associated interface
>>>>>>> classes. In
>>>>>>> > > >>>>> practice,
>>>>>>> > > >>>>>>>>>>>>>>>>> such semantic to interface binding seems
>>>>>>> necessary for
>>>>>>> > > >>>>>>> different
>>>>>>> > > >>>>>>>>>>>>>>>>> components to communicate. Simply standardize
>>>>>>> the
>>>>>>> > > semantic
>>>>>>> > > >>>>> of
>>>>>>> > > >>>>>>>>>>>>>> the
>>>>>>> > > >>>>>>>>>>>>>>>>> connector metrics seems not sufficient for
>>>>>>> people to
>>>>>>> > > build
>>>>>>> > > >>>>>>>>>>>>>>>>> ecosystem on top of. At the end of the day, we
>>>>>>> still
>>>>>>> > need
>>>>>>> > > >> to
>>>>>>> > > >>>>>>>>> have
>>>>>>> > > >>>>>>>>>>>>>>>>> some embodiment of the metric semantics that
>>>>>>> people can
>>>>>>> > > >>>>> program
>>>>>>> > > >>>>>>>>>>>>>>>>> against.
>>>>>>> > > >>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>> 2. Sometimes the same metric semantic can be
>>>>>>> exposed
>>>>>>> > > using
>>>>>>> > > >>>>>>>>>>>>>>>>> different metric types / interfaces.
>>>>>>> > > >>>>>>>>>>>>>>>>> This is a good point. Counter and
>>>>>>> Gauge-as-a-Counter
>>>>>>> > are
>>>>>>> > > >>>>> pretty
>>>>>>> > > >>>>>>>>>>>>>>>>> much interchangeable. This is more of a
>>>>>>> trade-off
>>>>>>> > between
>>>>>>> > > >> the
>>>>>>> > > >>>>>>>>>>>>>> user
>>>>>>> > > >>>>>>>>>>>>>>>>> experience of metric producers and consumers.
>>>>>>> The
>>>>>>> > metric
>>>>>>> > > >>>>>>>>>>>>>> producers
>>>>>>> > > >>>>>>>>>>>>>>>>> want to use Counter or Gauge depending on
>>>>>>> whether the
>>>>>>> > > >> counter
>>>>>>> > > >>>>>>> is
>>>>>>> > > >>>>>>>>>>>>>>>>> already tracked in code, while ideally the
>>>>>>> metric
>>>>>>> > > consumers
>>>>>>> > > >>>>>>> only
>>>>>>> > > >>>>>>>>>>>>>>>>> want to see a single metric type for each
>>>>>>> metric. I am
>>>>>>> > > >>>>> leaning
>>>>>>> > > >>>>>>>>>>>>>>>>> towards to make the metric producers happy,
>>>>>>> i.e. allow
>>>>>>> > > >> Gauge
>>>>>>> > > >>>>> /
>>>>>>> > > >>>>>>>>>>>>>>>>> Counter metric type, and the the metric
>>>>>>> consumers
>>>>>>> > handle
>>>>>>> > > >> the
>>>>>>> > > >>>>>>>>> type
>>>>>>> > > >>>>>>>>>>>>>>>>> variation. The reason is that in practice,
>>>>>>> there might
>>>>>>> > be
>>>>>>> > > >>>>> more
>>>>>>> > > >>>>>>>>>>>>>>>>> connector implementations than metric reporter
>>>>>>> > > >>>>> implementations.
>>>>>>> > > >>>>>>>>>>>>>> We
>>>>>>> > > >>>>>>>>>>>>>>>>> could also provide some helper method to
>>>>>>> facilitate
>>>>>>> > > reading
>>>>>>> > > >>>>>>> from
>>>>>>> > > >>>>>>>>>>>>>>>>> such variable metric type.
>>>>>>> > > >>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>> Just some quick replies to the comments around
>>>>>>> > > >> implementation
>>>>>>> > > >>>>>>>>>>>>>>>> details.
>>>>>>> > > >>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>> 4) single place where metrics are registered
>>>>>>> except
>>>>>>> > > >>>>>>>>>>>>>>>>> connector-specific
>>>>>>> > > >>>>>>>>>>>>>>>>> ones (which we can't really avoid).
>>>>>>> > > >>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>> Register connector specific ones in a single
>>>>>>> place is
>>>>>>> > > >>>>> actually
>>>>>>> > > >>>>>>>>>>>>>>>>> something that I want to achieve.
>>>>>>> > > >>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>> 2) I'm talking about time-series databases
>>>>>>> like
>>>>>>> > > >>>>> Prometheus.
>>>>>>> > > >>>>>>>>>>>>>> We
>>>>>>> > > >>>>>>>>>>>>>>>>> would
>>>>>>> > > >>>>>>>>>>>>>>>>> only have a gauge metric exposing the last
>>>>>>> > > >>>>>>>>> fetchTime/emitTime
>>>>>>> > > >>>>>>>>>>>>>>>>> that is
>>>>>>> > > >>>>>>>>>>>>>>>>> regularly reported to the backend
>>>>>>> (Prometheus),
>>>>>>> > where a
>>>>>>> > > >>>>>>> user
>>>>>>> > > >>>>>>>>>>>>>>>>> could build
>>>>>>> > > >>>>>>>>>>>>>>>>> a histogram of his choosing when/if he wants
>>>>>>> it.
>>>>>>> > > >>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>> Not sure if such downsampling works. As an
>>>>>>> example, if
>>>>>>> > a
>>>>>>> > > >> user
>>>>>>> > > >>>>>>>>>>>>>>>>> complains that there are some intermittent
>>>>>>> latency
>>>>>>> > spikes
>>>>>>> > > >>>>>>> (maybe
>>>>>>> > > >>>>>>>>>>>>>> a
>>>>>>> > > >>>>>>>>>>>>>>>>> few records in 10 seconds) in their processing
>>>>>>> system.
>>>>>>> > > >>>>> Having a
>>>>>>> > > >>>>>>>>>>>>>>>>> Gauge sampling instantaneous latency seems
>>>>>>> unlikely
>>>>>>> > > useful.
>>>>>>> > > >>>>>>>>>>>>>>>>> However by looking at actual 99.9 percentile
>>>>>>> latency
>>>>>>> > > might
>>>>>>> > > >>>>>>> help.
>>>>>>> > > >>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>> Thanks,
>>>>>>> > > >>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>> Jiangjie (Becket) Qin
>>>>>>> > > >>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>> On Fri, Feb 22, 2019 at 9:30 PM Chesnay
>>>>>>> Schepler
>>>>>>> > > >>>>>>>>>>>>>>>>> <chesnay@apache.org <mailto:chesnay@apache.org
>>>>>>> >>
>>>>>>> > wrote:
>>>>>>> > > >>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>> Re: over complication of implementation.
>>>>>>> > > >>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>> I think I get understand better know what
>>>>>>> you're
>>>>>>> > > >> shooting
>>>>>>> > > >>>>>>>>>>>>>> for,
>>>>>>> > > >>>>>>>>>>>>>>>>> effectively something like the
>>>>>>> OperatorIOMetricGroup.
>>>>>>> > > >>>>>>>>>>>>>>>>> But still, re-define setupConnectorMetrics()
>>>>>>> to
>>>>>>> > accept
>>>>>>> > > a
>>>>>>> > > >>>>>>> set
>>>>>>> > > >>>>>>>>>>>>>>>>> of flags
>>>>>>> > > >>>>>>>>>>>>>>>>> for counters/meters(ans _possibly_
>>>>>>> histograms) along
>>>>>>> > > >>>>> with a
>>>>>>> > > >>>>>>>>>>>>>>>>> set of
>>>>>>> > > >>>>>>>>>>>>>>>>> well-defined Optional<Gauge<?>>, and return
>>>>>>> the
>>>>>>> > group.
>>>>>>> > > >>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>> Solves all issues as far as i can tell:
>>>>>>> > > >>>>>>>>>>>>>>>>> 1) no metrics must be created manually
>>>>>>> (except
>>>>>>> > Gauges,
>>>>>>> > > >>>>>>> which
>>>>>>> > > >>>>>>>>>>>>>>> are
>>>>>>> > > >>>>>>>>>>>>>>>>> effectively just Suppliers and you can't get
>>>>>>> around
>>>>>>> > > >>>>> this),
>>>>>>> > > >>>>>>>>>>>>>>>>> 2) additional metrics can be registered on
>>>>>>> the
>>>>>>> > returned
>>>>>>> > > >>>>>>>>>>>>>> group,
>>>>>>> > > >>>>>>>>>>>>>>>>> 3) see 1),
>>>>>>> > > >>>>>>>>>>>>>>>>> 4) single place where metrics are registered
>>>>>>> except
>>>>>>> > > >>>>>>>>>>>>>>>>> connector-specific
>>>>>>> > > >>>>>>>>>>>>>>>>> ones (which we can't really avoid).
>>>>>>> > > >>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>> Re: Histogram
>>>>>>> > > >>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>> 1) As an example, whether "numRecordsIn" is
>>>>>>> exposed
>>>>>>> > as
>>>>>>> > > a
>>>>>>> > > >>>>>>>>>>>>>>>>> Counter or a
>>>>>>> > > >>>>>>>>>>>>>>>>> Gauge should be irrelevant. So far we're
>>>>>>> using the
>>>>>>> > > >> metric
>>>>>>> > > >>>>>>>>>>>>>> type
>>>>>>> > > >>>>>>>>>>>>>>>>> that is
>>>>>>> > > >>>>>>>>>>>>>>>>> the most convenient at exposing a given
>>>>>>> value. If
>>>>>>> > there
>>>>>>> > > >>>>> is
>>>>>>> > > >>>>>>>>>>>>>>>>> some backing
>>>>>>> > > >>>>>>>>>>>>>>>>> data-structure that we want to expose some
>>>>>>> data from
>>>>>>> > we
>>>>>>> > > >>>>>>>>>>>>>>>>> typically opt
>>>>>>> > > >>>>>>>>>>>>>>>>> for a Gauge, as otherwise we're just mucking
>>>>>>> around
>>>>>>> > > with
>>>>>>> > > >>>>>>> the
>>>>>>> > > >>>>>>>>>>>>>>>>> Meter/Counter API to get it to match.
>>>>>>> Similarly, if
>>>>>>> > we
>>>>>>> > > >>>>> want
>>>>>>> > > >>>>>>>>>>>>>> to
>>>>>>> > > >>>>>>>>>>>>>>>>> count
>>>>>>> > > >>>>>>>>>>>>>>>>> something but no current count exists we
>>>>>>> typically
>>>>>>> > > added
>>>>>>> > > >>>>> a
>>>>>>> > > >>>>>>>>>>>>>>>>> Counter.
>>>>>>> > > >>>>>>>>>>>>>>>>> That's why attaching semantics to metric
>>>>>>> types makes
>>>>>>> > > >>>>> little
>>>>>>> > > >>>>>>>>>>>>>>>>> sense (but
>>>>>>> > > >>>>>>>>>>>>>>>>> unfortunately several reporters already do
>>>>>>> it); for
>>>>>>> > > >>>>>>>>>>>>>>>>> counters/meters
>>>>>>> > > >>>>>>>>>>>>>>>>> certainly, but the majority of metrics are
>>>>>>> gauges.
>>>>>>> > > >>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>> 2) I'm talking about time-series databases
>>>>>>> like
>>>>>>> > > >>>>> Prometheus.
>>>>>>> > > >>>>>>>>>>>>>> We
>>>>>>> > > >>>>>>>>>>>>>>>>> would
>>>>>>> > > >>>>>>>>>>>>>>>>> only have a gauge metric exposing the last
>>>>>>> > > >>>>>>>>> fetchTime/emitTime
>>>>>>> > > >>>>>>>>>>>>>>>>> that is
>>>>>>> > > >>>>>>>>>>>>>>>>> regularly reported to the backend
>>>>>>> (Prometheus),
>>>>>>> > where a
>>>>>>> > > >>>>>>> user
>>>>>>> > > >>>>>>>>>>>>>>>>> could build
>>>>>>> > > >>>>>>>>>>>>>>>>> a histogram of his choosing when/if he wants
>>>>>>> it.
>>>>>>> > > >>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>> On 22.02.2019 13:57, Becket Qin wrote:
>>>>>>> > > >>>>>>>>>>>>>>>>>> Hi Chesnay,
>>>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>>> Thanks for the explanation.
>>>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>>> ** Re: FLIP
>>>>>>> > > >>>>>>>>>>>>>>>>>> I might have misunderstood this, but it seems
>>>>>>> that
>>>>>>> > > "major
>>>>>>> > > >>>>>>>>>>>>>>>>> changes" are well
>>>>>>> > > >>>>>>>>>>>>>>>>>> defined in FLIP. The full contents is
>>>>>>> following:
>>>>>>> > > >>>>>>>>>>>>>>>>>> What is considered a "major change" that
>>>>>>> needs a FLIP?
>>>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>>> Any of the following should be considered a
>>>>>>> major
>>>>>>> > > change:
>>>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>>> - Any major new feature, subsystem, or piece
>>>>>>> of
>>>>>>> > > >>>>>>>>>>>>>>>>> functionality
>>>>>>> > > >>>>>>>>>>>>>>>>>> - *Any change that impacts the public
>>>>>>> interfaces of
>>>>>>> > the
>>>>>>> > > >>>>>>>>>>>>>>>>> project*
>>>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>>> What are the "public interfaces" of the
>>>>>>> project?
>>>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>>> *All of the following are public interfaces
>>>>>>> *that
>>>>>>> > people
>>>>>>> > > >>>>>>>>>>>>>>>>> build around:
>>>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>>> - DataStream and DataSet API, including
>>>>>>> classes
>>>>>>> > related
>>>>>>> > > >>>>>>>>>>>>>>>>> to that, such as
>>>>>>> > > >>>>>>>>>>>>>>>>>> StreamExecutionEnvironment
>>>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>>> - Classes marked with the @Public annotation
>>>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>>> - On-disk binary formats, such as
>>>>>>> > > >>>>>>>>>>>>>> checkpoints/savepoints
>>>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>>> - User-facing scripts/command-line tools, i.e.
>>>>>>> > > >>>>>>>>>>>>>>>>> bin/flink, Yarn scripts,
>>>>>>> > > >>>>>>>>>>>>>>>>>> Mesos scripts
>>>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>>> - Configuration settings
>>>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>>> - *Exposed monitoring information*
>>>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>>> So any monitoring information change is
>>>>>>> considered as
>>>>>>> > > >>>>>>>>>>>>>> public
>>>>>>> > > >>>>>>>>>>>>>>>>> interface, and
>>>>>>> > > >>>>>>>>>>>>>>>>>> any public interface change is considered as
>>>>>>> a "major
>>>>>>> > > >>>>>>>>>>>>>>> change".
>>>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>>> ** Re: over complication of implementation.
>>>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>>> Although this is more of implementation
>>>>>>> details that
>>>>>>> > is
>>>>>>> > > >> not
>>>>>>> > > >>>>>>>>>>>>>>>>> covered by the
>>>>>>> > > >>>>>>>>>>>>>>>>>> FLIP. But it may be worth discussing.
>>>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>>> First of all, I completely agree that we
>>>>>>> should use
>>>>>>> > the
>>>>>>> > > >>>>>>>>>>>>>>>>> simplest way to
>>>>>>> > > >>>>>>>>>>>>>>>>>> achieve our goal. To me the goal is the
>>>>>>> following:
>>>>>>> > > >>>>>>>>>>>>>>>>>> 1. Clear connector conventions and interfaces.
>>>>>>> > > >>>>>>>>>>>>>>>>>> 2. The easiness of creating a connector.
>>>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>>> Both of them are important to the prosperity
>>>>>>> of the
>>>>>>> > > >>>>>>>>>>>>>>>>> connector ecosystem. So
>>>>>>> > > >>>>>>>>>>>>>>>>>> I'd rather abstract as much as possible on
>>>>>>> our side to
>>>>>>> > > >> make
>>>>>>> > > >>>>>>>>>>>>>>>>> the connector
>>>>>>> > > >>>>>>>>>>>>>>>>>> developer's work lighter. Given this goal, a
>>>>>>> static
>>>>>>> > util
>>>>>>> > > >>>>>>>>>>>>>>>>> method approach
>>>>>>> > > >>>>>>>>>>>>>>>>>> might have a few drawbacks:
>>>>>>> > > >>>>>>>>>>>>>>>>>> 1. Users still have to construct the metrics
>>>>>>> by
>>>>>>> > > >> themselves.
>>>>>>> > > >>>>>>>>>>>>>>>>> (And note that
>>>>>>> > > >>>>>>>>>>>>>>>>>> this might be erroneous by itself. For
>>>>>>> example, a
>>>>>>> > > customer
>>>>>>> > > >>>>>>>>>>>>>>>>> wrapper around
>>>>>>> > > >>>>>>>>>>>>>>>>>> dropwizard meter maybe used instead of
>>>>>>> MeterView).
>>>>>>> > > >>>>>>>>>>>>>>>>>> 2. When connector specific metrics are added,
>>>>>>> it is
>>>>>>> > > >>>>>>>>>>>>>>>>> difficult to enforce
>>>>>>> > > >>>>>>>>>>>>>>>>>> the scope to be the same as standard metrics.
>>>>>>> > > >>>>>>>>>>>>>>>>>> 3. It seems that a method proliferation is
>>>>>>> inevitable
>>>>>>> > if
>>>>>>> > > >> we
>>>>>>> > > >>>>>>>>>>>>>>>>> want to apply
>>>>>>> > > >>>>>>>>>>>>>>>>>> sanity checks. e.g. The metric of numBytesIn
>>>>>>> was not
>>>>>>> > > >>>>>>>>>>>>>>>>> registered for a meter.
>>>>>>> > > >>>>>>>>>>>>>>>>>> 4. Metrics are still defined in random places
>>>>>>> and hard
>>>>>>> > > to
>>>>>>> > > >>>>>>>>>>>>>>>> track.
>>>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>>> The current PR I had was inspired by the
>>>>>>> Config system
>>>>>>> > > in
>>>>>>> > > >>>>>>>>>>>>>>>>> Kafka, which I
>>>>>>> > > >>>>>>>>>>>>>>>>>> found pretty handy. In fact it is not only
>>>>>>> used by
>>>>>>> > Kafka
>>>>>>> > > >>>>>>>>>>>>>>>>> itself but even
>>>>>>> > > >>>>>>>>>>>>>>>>>> some other projects that depend on Kafka. I
>>>>>>> am not
>>>>>>> > > saying
>>>>>>> > > >>>>>>>>>>>>>>>>> this approach is
>>>>>>> > > >>>>>>>>>>>>>>>>>> perfect. But I think it worths to save the
>>>>>>> work for
>>>>>>> > > >>>>>>>>>>>>>>>>> connector writers and
>>>>>>> > > >>>>>>>>>>>>>>>>>> encourage more systematic implementation.
>>>>>>> That being
>>>>>>> > > said,
>>>>>>> > > >>>>>>>>>>>>>> I
>>>>>>> > > >>>>>>>>>>>>>>>>> am fully open
>>>>>>> > > >>>>>>>>>>>>>>>>>> to suggestions.
>>>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>>> Re: Histogram
>>>>>>> > > >>>>>>>>>>>>>>>>>> I think there are two orthogonal questions
>>>>>>> around
>>>>>>> > those
>>>>>>> > > >>>>>>>>>>>>>>>> metrics:
>>>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>>> 1. Regardless of the metric type, by just
>>>>>>> looking at
>>>>>>> > the
>>>>>>> > > >>>>>>>>>>>>>>>>> meaning of a
>>>>>>> > > >>>>>>>>>>>>>>>>>> metric, is generic to all connectors? If the
>>>>>>> answer is
>>>>>>> > > >> yes,
>>>>>>> > > >>>>>>>>>>>>>>>>> we should
>>>>>>> > > >>>>>>>>>>>>>>>>>> include the metric into the convention. No
>>>>>>> matter
>>>>>>> > > whether
>>>>>>> > > >>>>>>>>>>>>>> we
>>>>>>> > > >>>>>>>>>>>>>>>>> include it
>>>>>>> > > >>>>>>>>>>>>>>>>>> into the convention or not, some connector
>>>>>>> > > implementations
>>>>>>> > > >>>>>>>>>>>>>>>>> will emit such
>>>>>>> > > >>>>>>>>>>>>>>>>>> metric. It is better to have a convention
>>>>>>> than letting
>>>>>>> > > >> each
>>>>>>> > > >>>>>>>>>>>>>>>>> connector do
>>>>>>> > > >>>>>>>>>>>>>>>>>> random things.
>>>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>>> 2. If a standard metric is a histogram, what
>>>>>>> should we
>>>>>>> > > do?
>>>>>>> > > >>>>>>>>>>>>>>>>>> I agree that we should make it clear that
>>>>>>> using
>>>>>>> > > histograms
>>>>>>> > > >>>>>>>>>>>>>>>>> will have
>>>>>>> > > >>>>>>>>>>>>>>>>>> performance risk. But I do see histogram is
>>>>>>> useful in
>>>>>>> > > some
>>>>>>> > > >>>>>>>>>>>>>>>>> fine-granularity
>>>>>>> > > >>>>>>>>>>>>>>>>>> debugging where one do not have the luxury to
>>>>>>> stop the
>>>>>>> > > >>>>>>>>>>>>>>>>> system and inject
>>>>>>> > > >>>>>>>>>>>>>>>>>> more inspection code. So the workaround I am
>>>>>>> thinking
>>>>>>> > is
>>>>>>> > > >> to
>>>>>>> > > >>>>>>>>>>>>>>>>> provide some
>>>>>>> > > >>>>>>>>>>>>>>>>>> implementation suggestions. Assume later on
>>>>>>> we have a
>>>>>>> > > >>>>>>>>>>>>>>>>> mechanism of
>>>>>>> > > >>>>>>>>>>>>>>>>>> selective metrics. In the abstract metrics
>>>>>>> class we
>>>>>>> > can
>>>>>>> > > >>>>>>>>>>>>>>>>> disable those
>>>>>>> > > >>>>>>>>>>>>>>>>>> metrics by default individual connector
>>>>>>> writers does
>>>>>>> > not
>>>>>>> > > >>>>>>>>>>>>>>>>> have to do
>>>>>>> > > >>>>>>>>>>>>>>>>>> anything (this is another advantage of having
>>>>>>> an
>>>>>>> > > >>>>>>>>>>>>>>>>> AbstractMetrics instead of
>>>>>>> > > >>>>>>>>>>>>>>>>>> static util methods.)
>>>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>>> I am not sure I fully understand the
>>>>>>> histogram in the
>>>>>>> > > >>>>>>>>>>>>>>>>> backend approach. Can
>>>>>>> > > >>>>>>>>>>>>>>>>>> you explain a bit more? Do you mean emitting
>>>>>>> the raw
>>>>>>> > > data,
>>>>>>> > > >>>>>>>>>>>>>>>>> e.g. fetchTime
>>>>>>> > > >>>>>>>>>>>>>>>>>> and emitTime with each record and let the
>>>>>>> histogram
>>>>>>> > > >>>>>>>>>>>>>>>>> computation happen in
>>>>>>> > > >>>>>>>>>>>>>>>>>> the background? Or let the processing thread
>>>>>>> putting
>>>>>>> > the
>>>>>>> > > >>>>>>>>>>>>>>>>> values into a
>>>>>>> > > >>>>>>>>>>>>>>>>>> queue and have a separate thread polling from
>>>>>>> the
>>>>>>> > queue
>>>>>>> > > >> and
>>>>>>> > > >>>>>>>>>>>>>>>>> add them into
>>>>>>> > > >>>>>>>>>>>>>>>>>> the histogram?
>>>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>>> Thanks,
>>>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>>> Jiangjie (Becket) Qin
>>>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>>> On Fri, Feb 22, 2019 at 4:34 PM Chesnay
>>>>>>> Schepler
>>>>>>> > > >>>>>>>>>>>>>>>>> <chesnay@apache.org <mailto:
>>>>>>> chesnay@apache.org>>
>>>>>>> > > wrote:
>>>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>>>> Re: Flip
>>>>>>> > > >>>>>>>>>>>>>>>>>>> The very first line under both the main
>>>>>>> header and
>>>>>>> > > >> Purpose
>>>>>>> > > >>>>>>>>>>>>>>>>> section
>>>>>>> > > >>>>>>>>>>>>>>>>>>> describe Flips as "major changes", which
>>>>>>> this isn't.
>>>>>>> > > >>>>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>>>> Re: complication
>>>>>>> > > >>>>>>>>>>>>>>>>>>> I'm not arguing against standardization, but
>>>>>>> again an
>>>>>>> > > >>>>>>>>>>>>>>>>> over-complicated
>>>>>>> > > >>>>>>>>>>>>>>>>>>> implementation when a static utility method
>>>>>>> would be
>>>>>>> > > >>>>>>>>>>>>>>>>> sufficient.
>>>>>>> > > >>>>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>>>> public static void setupConnectorMetrics(
>>>>>>> > > >>>>>>>>>>>>>>>>>>> MetricGroup operatorMetricGroup,
>>>>>>> > > >>>>>>>>>>>>>>>>>>> String connectorName,
>>>>>>> > > >>>>>>>>>>>>>>>>>>> Optional<Gauge<Long>> numRecordsIn,
>>>>>>> > > >>>>>>>>>>>>>>>>>>> ...)
>>>>>>> > > >>>>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>>>> This gives you all you need:
>>>>>>> > > >>>>>>>>>>>>>>>>>>> * a well-defined set of metrics for a
>>>>>>> connector to
>>>>>>> > > opt-in
>>>>>>> > > >>>>>>>>>>>>>>>>>>> * standardized naming schemes for scope and
>>>>>>> > individual
>>>>>>> > > >>>>>>>>>>>>>>> metrics
>>>>>>> > > >>>>>>>>>>>>>>>>>>> * standardize metric types (although
>>>>>>> personally I'm
>>>>>>> > not
>>>>>>> > > >>>>>>>>>>>>>>>>> interested in that
>>>>>>> > > >>>>>>>>>>>>>>>>>>> since metric types should be considered
>>>>>>> syntactic
>>>>>>> > > sugar)
>>>>>>> > > >>>>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>>>> Re: Configurable Histogram
>>>>>>> > > >>>>>>>>>>>>>>>>>>> If anything they _must_ be turned off by
>>>>>>> default, but
>>>>>>> > > the
>>>>>>> > > >>>>>>>>>>>>>>>>> metric system is
>>>>>>> > > >>>>>>>>>>>>>>>>>>> already exposing so many options that I'm
>>>>>>> not too
>>>>>>> > keen
>>>>>>> > > on
>>>>>>> > > >>>>>>>>>>>>>>>>> adding even more.
>>>>>>> > > >>>>>>>>>>>>>>>>>>> You have also only addressed my first
>>>>>>> argument
>>>>>>> > against
>>>>>>> > > >>>>>>>>>>>>>>>>> histograms
>>>>>>> > > >>>>>>>>>>>>>>>>>>> (performance), the second one still stands
>>>>>>> (calculate
>>>>>>> > > >>>>>>>>>>>>>>>>> histogram in metric
>>>>>>> > > >>>>>>>>>>>>>>>>>>> backends instead).
>>>>>>> > > >>>>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>>>> On 21.02.2019 16:27, Becket Qin wrote:
>>>>>>> > > >>>>>>>>>>>>>>>>>>>> Hi Chesnay,
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>>>>> Thanks for the comments. I think this is
>>>>>>> worthy of a
>>>>>>> > > >> FLIP
>>>>>>> > > >>>>>>>>>>>>>>>>> because it is
>>>>>>> > > >>>>>>>>>>>>>>>>>>>> public API. According to the FLIP
>>>>>>> description a FlIP
>>>>>>> > > is
>>>>>>> > > >>>>>>>>>>>>>>>>> required in case
>>>>>>> > > >>>>>>>>>>>>>>>>>>> of:
>>>>>>> > > >>>>>>>>>>>>>>>>>>>> - Any change that impacts the public
>>>>>>> interfaces of
>>>>>>> > > >>>>>>>>>>>>>>>>> the project
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>>>>> and the following entry is found in the
>>>>>>> definition
>>>>>>> > of
>>>>>>> > > >>>>>>>>>>>>>>>>> "public interface".
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>>>>> - Exposed monitoring information
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>>>>> Metrics are critical to any production
>>>>>>> system. So a
>>>>>>> > > >> clear
>>>>>>> > > >>>>>>>>>>>>>>>>> metric
>>>>>>> > > >>>>>>>>>>>>>>>>>>> definition
>>>>>>> > > >>>>>>>>>>>>>>>>>>>> is important for any serious users. For an
>>>>>>> > > organization
>>>>>>> > > >>>>>>>>>>>>>>>>> with large Flink
>>>>>>> > > >>>>>>>>>>>>>>>>>>>> installation, change in metrics means great
>>>>>>> amount
>>>>>>> > of
>>>>>>> > > >>>>>>>>>>>>>>>>> work. So such
>>>>>>> > > >>>>>>>>>>>>>>>>>>> changes
>>>>>>> > > >>>>>>>>>>>>>>>>>>>> do need to be fully discussed and
>>>>>>> documented.
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>>>>> ** Re: Histogram.
>>>>>>> > > >>>>>>>>>>>>>>>>>>>> We can discuss whether there is a better
>>>>>>> way to
>>>>>>> > expose
>>>>>>> > > >>>>>>>>>>>>>>>>> metrics that are
>>>>>>> > > >>>>>>>>>>>>>>>>>>>> suitable for histograms. My micro-benchmark
>>>>>>> on
>>>>>>> > various
>>>>>>> > > >>>>>>>>>>>>>>>>> histogram
>>>>>>> > > >>>>>>>>>>>>>>>>>>>> implementations also indicates that they are
>>>>>>> > > >>>>>>>>>>>>>> significantly
>>>>>>> > > >>>>>>>>>>>>>>>>> slower than
>>>>>>> > > >>>>>>>>>>>>>>>>>>>> other metric types. But I don't think that
>>>>>>> means
>>>>>>> > never
>>>>>>> > > >>>>>>>>>>>>>> use
>>>>>>> > > >>>>>>>>>>>>>>>>> histogram, but
>>>>>>> > > >>>>>>>>>>>>>>>>>>>> means use it with caution. For example, we
>>>>>>> can
>>>>>>> > suggest
>>>>>>> > > >>>>>>>>>>>>>> the
>>>>>>> > > >>>>>>>>>>>>>>>>>>> implementations
>>>>>>> > > >>>>>>>>>>>>>>>>>>>> to turn them off by default and only turn
>>>>>>> it on for
>>>>>>> > a
>>>>>>> > > >>>>>>>>>>>>>>>>> small amount of
>>>>>>> > > >>>>>>>>>>>>>>>>>>> time
>>>>>>> > > >>>>>>>>>>>>>>>>>>>> when performing some micro-debugging.
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>>>>> ** Re: complication:
>>>>>>> > > >>>>>>>>>>>>>>>>>>>> Connector conventions are essential for
>>>>>>> Flink
>>>>>>> > > ecosystem.
>>>>>>> > > >>>>>>>>>>>>>>>>> Flink connectors
>>>>>>> > > >>>>>>>>>>>>>>>>>>>> pool is probably the most important part of
>>>>>>> Flink,
>>>>>>> > > just
>>>>>>> > > >>>>>>>>>>>>>>>>> like any other
>>>>>>> > > >>>>>>>>>>>>>>>>>>> data
>>>>>>> > > >>>>>>>>>>>>>>>>>>>> system. Clear conventions of connectors
>>>>>>> will help
>>>>>>> > > build
>>>>>>> > > >>>>>>>>>>>>>>>>> Flink ecosystem
>>>>>>> > > >>>>>>>>>>>>>>>>>>> in
>>>>>>> > > >>>>>>>>>>>>>>>>>>>> a more organic way.
>>>>>>> > > >>>>>>>>>>>>>>>>>>>> Take the metrics convention as an example,
>>>>>>> imagine
>>>>>>> > > >>>>>>>>>>>>>> someone
>>>>>>> > > >>>>>>>>>>>>>>>>> has developed
>>>>>>> > > >>>>>>>>>>>>>>>>>>> a
>>>>>>> > > >>>>>>>>>>>>>>>>>>>> Flink connector for System foo, and another
>>>>>>> > developer
>>>>>>> > > >> may
>>>>>>> > > >>>>>>>>>>>>>>>>> have developed
>>>>>>> > > >>>>>>>>>>>>>>>>>>> a
>>>>>>> > > >>>>>>>>>>>>>>>>>>>> monitoring and diagnostic framework for
>>>>>>> Flink which
>>>>>>> > > >>>>>>>>>>>>>>>>> analyzes the Flink
>>>>>>> > > >>>>>>>>>>>>>>>>>>> job
>>>>>>> > > >>>>>>>>>>>>>>>>>>>> performance based on metrics. With a clear
>>>>>>> metric
>>>>>>> > > >>>>>>>>>>>>>>>>> convention, those two
>>>>>>> > > >>>>>>>>>>>>>>>>>>>> projects could be developed independently.
>>>>>>> Once
>>>>>>> > users
>>>>>>> > > >> put
>>>>>>> > > >>>>>>>>>>>>>>>>> them together,
>>>>>>> > > >>>>>>>>>>>>>>>>>>>> it would work without additional
>>>>>>> modifications. This
>>>>>>> > > >>>>>>>>>>>>>>>>> cannot be easily
>>>>>>> > > >>>>>>>>>>>>>>>>>>>> achieved by just defining a few constants.
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>>>>> ** Re: selective metrics:
>>>>>>> > > >>>>>>>>>>>>>>>>>>>> Sure, we can discuss that in a separate
>>>>>>> thread.
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>>>>> @Dawid
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>>>>> ** Re: latency / fetchedLatency
>>>>>>> > > >>>>>>>>>>>>>>>>>>>> The primary purpose of establish such a
>>>>>>> convention
>>>>>>> > is
>>>>>>> > > to
>>>>>>> > > >>>>>>>>>>>>>>>>> help developers
>>>>>>> > > >>>>>>>>>>>>>>>>>>>> write connectors in a more compatible way.
>>>>>>> The
>>>>>>> > > >> convention
>>>>>>> > > >>>>>>>>>>>>>>>>> is supposed to
>>>>>>> > > >>>>>>>>>>>>>>>>>>> be
>>>>>>> > > >>>>>>>>>>>>>>>>>>>> defined more proactively. So when look at
>>>>>>> the
>>>>>>> > > >> convention,
>>>>>>> > > >>>>>>>>>>>>>>>>> it seems more
>>>>>>> > > >>>>>>>>>>>>>>>>>>>> important to see if the concept is
>>>>>>> applicable to
>>>>>>> > > >>>>>>>>>>>>>>>>> connectors in general.
>>>>>>> > > >>>>>>>>>>>>>>>>>>> It
>>>>>>> > > >>>>>>>>>>>>>>>>>>>> might be true so far only Kafka connector
>>>>>>> reports
>>>>>>> > > >>>>>>>>>>>>>> latency.
>>>>>>> > > >>>>>>>>>>>>>>>>> But there
>>>>>>> > > >>>>>>>>>>>>>>>>>>> might
>>>>>>> > > >>>>>>>>>>>>>>>>>>>> be hundreds of other connector
>>>>>>> implementations in
>>>>>>> > the
>>>>>>> > > >>>>>>>>>>>>>>>>> Flink ecosystem,
>>>>>>> > > >>>>>>>>>>>>>>>>>>>> though not in the Flink repo, and some of
>>>>>>> them also
>>>>>>> > > >> emits
>>>>>>> > > >>>>>>>>>>>>>>>>> latency. I
>>>>>>> > > >>>>>>>>>>>>>>>>>>> think
>>>>>>> > > >>>>>>>>>>>>>>>>>>>> a lot of other sources actually also has an
>>>>>>> append
>>>>>>> > > >>>>>>>>>>>>>>>>> timestamp. e.g.
>>>>>>> > > >>>>>>>>>>>>>>>>>>> database
>>>>>>> > > >>>>>>>>>>>>>>>>>>>> bin logs and some K-V stores. So I wouldn't
>>>>>>> be
>>>>>>> > > surprised
>>>>>>> > > >>>>>>>>>>>>>>>>> if some database
>>>>>>> > > >>>>>>>>>>>>>>>>>>>> connector can also emit latency metrics.
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>>>>> Thanks,
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>>>>> Jiangjie (Becket) Qin
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>>>>> On Thu, Feb 21, 2019 at 10:14 PM Chesnay
>>>>>>> Schepler
>>>>>>> > > >>>>>>>>>>>>>>>>> <chesnay@apache.org <mailto:
>>>>>>> chesnay@apache.org>>
>>>>>>> > > >>>>>>>>>>>>>>>>>>>> wrote:
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>> Regarding 2) It doesn't make sense to
>>>>>>> investigate
>>>>>>> > > this
>>>>>>> > > >>>>>>>>>>>>>> as
>>>>>>> > > >>>>>>>>>>>>>>>>> part of this
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>> FLIP. This is something that could be of
>>>>>>> interest
>>>>>>> > for
>>>>>>> > > >>>>>>>>>>>>>> the
>>>>>>> > > >>>>>>>>>>>>>>>>> entire metric
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>> system, and should be designed for as such.
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>> Regarding the proposal as a whole:
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>> Histogram metrics shall not be added to
>>>>>>> the core of
>>>>>>> > > >>>>>>>>>>>>>>>>> Flink. They are
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>> significantly more expensive than other
>>>>>>> metrics,
>>>>>>> > and
>>>>>>> > > >>>>>>>>>>>>>>>>> calculating
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>> histograms in the application is regarded
>>>>>>> as an
>>>>>>> > > >>>>>>>>>>>>>>>>> anti-pattern by several
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>> metric backends, who instead recommend to
>>>>>>> expose
>>>>>>> > the
>>>>>>> > > >> raw
>>>>>>> > > >>>>>>>>>>>>>>>>> data and
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>> calculate the histogram in the backend.
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>> Second, this seems overly complicated.
>>>>>>> Given that
>>>>>>> > we
>>>>>>> > > >>>>>>>>>>>>>>>>> already established
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>> that not all connectors will export all
>>>>>>> metrics we
>>>>>>> > > are
>>>>>>> > > >>>>>>>>>>>>>>>>> effectively
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>> reducing this down to a consistent naming
>>>>>>> scheme.
>>>>>>> > We
>>>>>>> > > >>>>>>>>>>>>>>>>> don't need anything
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>> sophisticated for that; basically just a
>>>>>>> few
>>>>>>> > > constants
>>>>>>> > > >>>>>>>>>>>>>>>>> that all
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>> connectors use.
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>> I'm not convinced that this is worthy of a
>>>>>>> FLIP.
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>> On 21.02.2019 14:26, Dawid Wysakowicz
>>>>>>> wrote:
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>> Hi,
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>> Ad 1. In general I undestand and I agree.
>>>>>>> But
>>>>>>> > those
>>>>>>> > > >>>>>>>>>>>>>>>>> particular metrics
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>> (latency, fetchLatency), right now would
>>>>>>> only be
>>>>>>> > > >>>>>>>>>>>>>>>>> reported if user uses
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>> KafkaConsumer with internal
>>>>>>> timestampAssigner with
>>>>>>> > > >>>>>>>>>>>>>>>>> StreamCharacteristic
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>> set to EventTime, right? That sounds like
>>>>>>> a very
>>>>>>> > > >>>>>>>>>>>>>>>>> specific case. I am
>>>>>>> > > >>>>>>>>>>>>>>>>>>> not
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>> sure if we should introduce a generic
>>>>>>> metric that
>>>>>>> > > will
>>>>>>> > > >>>>>>>>>>>>>> be
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>> disabled/absent for most of
>>>>>>> implementations.
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>> Ad.2 That sounds like an orthogonal
>>>>>>> issue, that
>>>>>>> > > might
>>>>>>> > > >>>>>>>>>>>>>>>>> make sense to
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>> investigate in the future.
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>> Best,
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>> Dawid
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>> On 21/02/2019 13:20, Becket Qin wrote:
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>> Hi Dawid,
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>> Thanks for the feedback. That makes
>>>>>>> sense to me.
>>>>>>> > > >> There
>>>>>>> > > >>>>>>>>>>>>>>>>> are two cases
>>>>>>> > > >>>>>>>>>>>>>>>>>>> to
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>> be
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>> addressed.
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>> 1. The metrics are supposed to be a
>>>>>>> guidance. It
>>>>>>> > is
>>>>>>> > > >>>>>>>>>>>>>>>>> likely that a
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>> connector
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>> only supports some but not all of the
>>>>>>> metrics. In
>>>>>>> > > >> that
>>>>>>> > > >>>>>>>>>>>>>>>>> case, each
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>> connector
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>> implementation should have the freedom
>>>>>>> to decide
>>>>>>> > > >> which
>>>>>>> > > >>>>>>>>>>>>>>>>> metrics are
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>> reported. For the metrics that are
>>>>>>> supported, the
>>>>>>> > > >>>>>>>>>>>>>>>>> guidance should be
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>> followed.
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>> 2. Sometimes users may want to disable
>>>>>>> certain
>>>>>>> > > >> metrics
>>>>>>> > > >>>>>>>>>>>>>>>>> for some reason
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>> (e.g. performance / reprocessing of
>>>>>>> data). A
>>>>>>> > > generic
>>>>>>> > > >>>>>>>>>>>>>>>>> mechanism should
>>>>>>> > > >>>>>>>>>>>>>>>>>>> be
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>> provided to allow user choose which
>>>>>>> metrics are
>>>>>>> > > >>>>>>>>>>>>>>>>> reported. This
>>>>>>> > > >>>>>>>>>>>>>>>>>>> mechanism
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>> should also be honored by the connector
>>>>>>> > > >>>>>>>>>>>>>> implementations.
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>> Does this sound reasonable to you?
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>> Thanks,
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>> Jiangjie (Becket) Qin
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>> On Thu, Feb 21, 2019 at 4:22 PM Dawid
>>>>>>> Wysakowicz
>>>>>>> > <
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>> dwysakowicz@apache.org <mailto:
>>>>>>> > > dwysakowicz@apache.org
>>>>>>> > > >>>>
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>> wrote:
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> Hi,
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> Generally I like the idea of having a
>>>>>>> unified,
>>>>>>> > > >>>>>>>>>>>>>>>>> standard set of
>>>>>>> > > >>>>>>>>>>>>>>>>>>> metrics
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>> for
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> all connectors. I have some slight
>>>>>>> concerns
>>>>>>> > about
>>>>>>> > > >>>>>>>>>>>>>>>>> fetchLatency and
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> latency though. They are computed based
>>>>>>> on
>>>>>>> > > EventTime
>>>>>>> > > >>>>>>>>>>>>>>>>> which is not a
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>> purely
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> technical feature. It depends often on
>>>>>>> some
>>>>>>> > > business
>>>>>>> > > >>>>>>>>>>>>>>>>> logic, might be
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>> absent
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> or defined after source. Those metrics
>>>>>>> could
>>>>>>> > also
>>>>>>> > > >>>>>>>>>>>>>>>>> behave in a weird
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>> way in
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> case of replaying backlog. Therefore I
>>>>>>> am not
>>>>>>> > sure
>>>>>>> > > >> if
>>>>>>> > > >>>>>>>>>>>>>>>>> we should
>>>>>>> > > >>>>>>>>>>>>>>>>>>> include
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> those metrics by default. Maybe we
>>>>>>> could at
>>>>>>> > least
>>>>>>> > > >>>>>>>>>>>>>>>>> introduce a feature
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> switch for them? What do you think?
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> Best,
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> Dawid
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> On 21/02/2019 03:13, Becket Qin wrote:
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> Bump. If there is no objections to the
>>>>>>> proposed
>>>>>>> > > >>>>>>>>>>>>>>>>> metrics. I'll start a
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> voting thread later toady.
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> Thanks,
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> Jiangjie (Becket) Qin
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> On Mon, Feb 11, 2019 at 8:17 PM Becket
>>>>>>> Qin
>>>>>>> > > >>>>>>>>>>>>>>>>> <becket.qin@gmail.com <mailto:
>>>>>>> becket.qin@gmail.com>>
>>>>>>> > <
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>> becket.qin@gmail.com <mailto:
>>>>>>> becket.qin@gmail.com
>>>>>>> > >>
>>>>>>> > > >>>>>>>>>>>>>>> wrote:
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> Hi folks,
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> I would like to start the FLIP
>>>>>>> discussion thread
>>>>>>> > > >>>>>>>>>>>>>> about
>>>>>>> > > >>>>>>>>>>>>>>>>> standardize
>>>>>>> > > >>>>>>>>>>>>>>>>>>> the
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> connector metrics.
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> In short, we would like to provide a
>>>>>>> convention
>>>>>>> > of
>>>>>>> > > >>>>>>>>>>>>>>>>> Flink connector
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> metrics. It will help simplify the
>>>>>>> monitoring
>>>>>>> > and
>>>>>>> > > >>>>>>>>>>>>>>>>> alerting on Flink
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>> jobs.
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> The FLIP link is following:
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>
>>>>>>> > > >>>>>>>
>>>>>>> > > >>>>>
>>>>>>> > > >>
>>>>>>> > >
>>>>>>> >
>>>>>>> https://cwiki.apache.org/confluence/display/FLINK/FLIP-33%3A+Standardize+Connector+Metrics
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> Thanks,
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> Jiangjie (Becket) Qin
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>>>>
>>>>>>> > > >>>>>>>>>
>>>>>>> > > >>>>>>>>>
>>>>>>> > > >>>>>>>>>
>>>>>>> > > >>>>>>>
>>>>>>> > > >>>>>>>
>>>>>>> > > >>>>>>>
>>>>>>> > > >>>>>
>>>>>>> > > >>>>>
>>>>>>> > > >>
>>>>>>> > > >>
>>>>>>> > >
>>>>>>> > >
>>>>>>> >
>>>>>>>
>>>>>>>
>>>>>>> --
>>>>>>>
>>>>>>> Konstantin Knauf
>>>>>>>
>>>>>>> https://twitter.com/snntrable
>>>>>>>
>>>>>>> https://github.com/knaufk
>>>>>>>
>>>>>>
Re: [DISCUSS] FLIP-33: Standardize connector metrics
Posted by Stephan Ewen <st...@ververica.com>.
Hi Becket!
I am wondering if it makes sense to do the following small change:
- Have "currentFetchEventTimeLag" be defined on event timestamps
(optionally, if the source system exposes it) <== this is like in your
proposal
this helps understand how long the records were in the source before
- BUT change "currentEmitEventTimeLag" to be "currentSourceWatermarkLag"
instead.
That way, users can see how far behind the wall-clock-time the source
progress is all in all.
It is also a more well defined metric as it does not oscillate with
out-of-order events.
What do you think?
Best,
Stephan
On Fri, Sep 18, 2020 at 12:02 PM Becket Qin <be...@gmail.com> wrote:
> Hi folks,
>
> Thanks for all the great feedback. I have just updated FLIP-33 wiki with
> the following changes:
>
> 1. Renaming. "currentFetchLatency" to "currentFetchEventTimeLag",
> "currentLatency" to "currentEmitEventTimeLag".
> 2. Added the public interface code change required for the new metrics.
> 3. Added description of whether a metric is predefined or optional, and
> which component is expected to update the metric.
>
> Please let me know if you have any questions. I'll start a vote in two
> days if there are no further concerns.
>
> Thanks,
>
> Jiangjie (Becket) Qin
>
> On Wed, Sep 9, 2020 at 9:56 AM Becket Qin <be...@gmail.com> wrote:
>
>> Hi Stephan,
>>
>> Thanks for the input. Just a few more clarifications / questions.
>>
>> *Num Bytes / Records Metrics*
>>
>> 1. At this point, the *numRecordsIn(Rate)* metrics exist in both
>> OperatorIOMetricGroup and TaskIOMetricGroup. I did not find
>> *numRecordsIn(Rate)* in the TaskIOMetricGroup updated anywhere other
>> than in the unit tests. Am I missing something?
>>
>> 2. *numBytesIn(Rate)* metrics only exist in TaskIOMetricGroup. At this
>> point, the SourceReaders only has access to a SourceReaderContext which
>> provides an OperatorMetricGroup. So it seems that the connector developers
>> are not able to update the *numBytesIn(Rate). *With the multiple Source
>> chaining support, it is possible that there are multiple Sources are in the
>> same task. So it looks that we need to add *numBytesIn(Rate)* to the
>> operator metrics as well.
>>
>>
>> *Current (Fetch) Latency*
>>
>> *currentFetchLatency* helps clearly tell whether the latency is caused
>> by Flink or not. Backpressure is not the only reason that we see fetch
>> latency. Even if there is no back pressure, the records may have passed a
>> long pipeline before they entered Flink. For example, say the *currentLatency
>> *is 10 seconds and there is no backpressure. Does that mean the record
>> spent 10 seconds in the Source operator? If not, how much did Flink
>> contribute to that 10 seconds of latency? These questions are frequently
>> asked and hard to tell without the fetch latency.
>>
>> For "currentFetchLatency", we would need to understand timestamps before
>>> the records are decoded. That is only possible for some sources, where the
>>> client gives us the records in a (partially) decoded from already (like
>>> Kafka). Then, some work has been done between the fetch time and the time
>>> we update the metric already, so it is already a bit closer to the
>>> "currentFetchLatency". I think following this train of thought, there is
>>> diminished benefit from that specific metric.
>>
>>
>> We may not have to report the fetch latency before records are decoded.
>> One solution is to remember the* FetchTime* when the encoded records are
>> fetched, and report the fetch latency after the records are decoded by
>> computing (*FetchTime - EventTime*). An approximate implementation would
>> be adding a *FetchTime *field to the *RecordsWithSplitIds* assuming that
>> all the records in that data structure are fetched at the same time.
>>
>> Thoughts?
>>
>> Thanks,
>>
>> Jiangjie (Becket) Qin
>>
>> On Wed, Sep 9, 2020 at 12:42 AM Stephan Ewen <st...@ververica.com>
>> wrote:
>>
>>> Thanks for reviving this, Becket!
>>>
>>> I think Konstantin's comments are great. I'd add these points:
>>>
>>> *Num Bytes / Records Metrics*
>>>
>>> For "numBytesIn" and "numRecordsIn", we should reuse the
>>> OperatorIOMetric group, then it also gets reported to the overview page in
>>> the Web UI.
>>>
>>> The "numBytesInPerSecond" and "numRecordsInPerSecond" are automatically
>>> derived metrics, no need to do anything once we populate the above two
>>> metrics
>>>
>>>
>>> *Current (Fetch) Latency*
>>>
>>> I would really go for "eventTimeLag" rather than "fetchLatency". I think
>>> "eventTimeLag" is a term that has some adoption in the Flink community and
>>> beyond.
>>>
>>> I am not so sure that I see the benefit between "currentLatency" and
>>> "currentFetchLatency", (or event time lag before/after) as this only is
>>> different by the time it takes to emit a batch.
>>> - In a non-backpressured case, these should be virtually identical
>>> (and both dominated by watermark lag, not the actual time it takes the
>>> fetch to be emitted)
>>> - In a backpressured case, why do you care about when data was
>>> fetched, as opposed to emitted? Emitted time is relevant for application
>>> semantics and checkpoints. Fetch time seems to be an implementation detail
>>> (how much does the source buffer).
>>>
>>> The "currentLatency" (eventTimeLagAfter) can be computed out-of-the-box,
>>> independent of a source implementation, so that is also a good argument to
>>> make it the main metric.
>>> We know timestamps and watermarks in the source. Except for cases where
>>> no watermarks have been defined at all (batch jobs or pure processing time
>>> jobs), in which case this metric should probably be "Infinite".
>>>
>>> For "currentFetchLatency", we would need to understand timestamps before
>>> the records are decoded. That is only possible for some sources, where the
>>> client gives us the records in a (partially) decoded from already (like
>>> Kafka). Then, some work has been done between the fetch time and the time
>>> we update the metric already, so it is already a bit closer to the
>>> "currentFetchLatency". I think following this train of thought, there is
>>> diminished benefit from that specific metric.
>>>
>>>
>>> *Idle Time*
>>>
>>> I agree, it would be great to rename this. Maybe to "sourceWaitTime" or
>>> "sourceIdleTime" so to make clear that this is not exactly the time that
>>> Flink's processing pipeline is idle, but the time where the source does not
>>> have new data.
>>>
>>> This is not an easy metric to collect, though (except maybe for the
>>> sources that are only idle while they have no split assigned, like
>>> continuous file source).
>>>
>>> *Source Specific Metrics*
>>>
>>> I believe source-specific would only be "sourceIdleTime",
>>> "numRecordsInErrors", "pendingBytes", and "pendingRecords".
>>>
>>>
>>> *Conclusion*
>>>
>>> We can probably add "numBytesIn" and "numRecordsIn" and "eventTimeLag"
>>> right away, with little complexity.
>>> I'd suggest to start with these right away.
>>>
>>> Best,
>>> Stephan
>>>
>>>
>>> On Tue, Sep 8, 2020 at 3:25 PM Becket Qin <be...@gmail.com> wrote:
>>>
>>>> Hey Konstantin,
>>>>
>>>> Thanks for the feedback and suggestions. Please see the reply below.
>>>>
>>>> * idleTime: In the meantime, a similar metric "idleTimeMsPerSecond" has
>>>>> been introduced in https://issues.apache.org/jira/browse/FLINK-16864.
>>>>> They
>>>>> have a similar name, but different definitions of idleness,
>>>>> e.g. "idleTimeMsPerSecond" considers the SourceTask idle, when it is
>>>>> backpressured. Can we make it clearer that these two metrics mean
>>>>> different
>>>>> things?
>>>>
>>>>
>>>> That is a good point. I did not notice this metric earlier. It seems
>>>> that both metrics are useful to the users. One tells them how busy the
>>>> source is and how much more throughput the source can handle. The other
>>>> tells the users how long since the source has seen the last record, which
>>>> is useful for debugging. I'll update the FLIP to make it clear.
>>>>
>>>> * "current(Fetch)Latency" I am wondering if
>>>>> "eventTimeLag(Before|After)"
>>>>> is more descriptive/clear. What do others think?
>>>>
>>>>
>>>> I am quite open to the ideas on these names. In fact I also feel
>>>> "current(Fetch)Latency" are not super intuitive. So it would be great if we
>>>> can have better names.
>>>>
>>>> * Current(Fetch)Latency implies that the timestamps are directly
>>>>> extracted in the source connector, right? Will this be the default for
>>>>> FLIP-27 sources anyway?
>>>>
>>>>
>>>> The "currentFetchLatency" will probably be reported by each source
>>>> implementation, because the data fetching is done by SplitReaders and there
>>>> is no base implementation. The "currentLatency", on the other hand, can be
>>>> reported by the SourceReader base implementation. However, since developers
>>>> can actually implement their own source connector without using our base
>>>> implementation, these metric guidance are still useful for the connector
>>>> developers in that case.
>>>>
>>>> * Does FLIP-33 also include the implementation of these metrics (to the
>>>>> extent possible) for all connectors currently available in Apache
>>>>> Flink or
>>>>> is the "per-connector implementation" out-of-scope?
>>>>
>>>>
>>>> FLIP-33 itself does not specify any implementation of those metrics.
>>>> But the connectors we provide in Apache Flink will follow the guidance of
>>>> FLIP-33 to emit those metrics when applicable. Maybe We can have some
>>>> public static Strings defined for the metric names to help other connector
>>>> developers follow the same guidance. I can also add that to the public
>>>> interface section of the FLIP if we decide to do that.
>>>>
>>>> Thanks,
>>>>
>>>> Jiangjie (Becket) Qin
>>>>
>>>> On Tue, Sep 8, 2020 at 9:02 PM Becket Qin <be...@gmail.com> wrote:
>>>>
>>>>>
>>>>>
>>>>> On Tue, Sep 8, 2020 at 6:55 PM Konstantin Knauf <kn...@apache.org>
>>>>> wrote:
>>>>>
>>>>>> Hi Becket,
>>>>>>
>>>>>> Thank you for picking up this FLIP. I have a few questions:
>>>>>>
>>>>>> * two thoughts on naming:
>>>>>> * idleTime: In the meantime, a similar metric
>>>>>> "idleTimeMsPerSecond" has
>>>>>> been introduced in https://issues.apache.org/jira/browse/FLINK-16864.
>>>>>> They
>>>>>> have a similar name, but different definitions of idleness,
>>>>>> e.g. "idleTimeMsPerSecond" considers the SourceTask idle, when it is
>>>>>> backpressured. Can we make it clearer that these two metrics mean
>>>>>> different
>>>>>> things?
>>>>>>
>>>>>> * "current(Fetch)Latency" I am wondering if
>>>>>> "eventTimeLag(Before|After)"
>>>>>> is more descriptive/clear. What do others think?
>>>>>>
>>>>>> * Current(Fetch)Latency implies that the timestamps are directly
>>>>>> extracted in the source connector, right? Will this be the default for
>>>>>> FLIP-27 sources anyway?
>>>>>>
>>>>>> * Does FLIP-33 also include the implementation of these metrics (to
>>>>>> the
>>>>>> extent possible) for all connectors currently available in Apache
>>>>>> Flink or
>>>>>> is the "per-connector implementation" out-of-scope?
>>>>>>
>>>>>> Thanks,
>>>>>>
>>>>>> Konstantin
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>> On Fri, Sep 4, 2020 at 4:56 PM Becket Qin <be...@gmail.com>
>>>>>> wrote:
>>>>>>
>>>>>> > Hi all,
>>>>>> >
>>>>>> > To complete the Source refactoring work, I'd like to revive this
>>>>>> > discussion. Since the mail thread has been dormant for more than a
>>>>>> year,
>>>>>> > just to recap the motivation of the FLIP:
>>>>>> >
>>>>>> > 1. The FLIP proposes to standardize the connector metrics by giving
>>>>>> > guidance on the metric specifications, including the name, type and
>>>>>> meaning
>>>>>> > of the metrics.
>>>>>> > 2. It is OK for a connector to not emit some of the metrics in the
>>>>>> metric
>>>>>> > guidance, but if a metric of the same semantic is emitted, the
>>>>>> > implementation should follow the guidance.
>>>>>> > 3. It is OK for a connector to emit more metrics than what are
>>>>>> listed in
>>>>>> > the FLIP. This includes having an alias for a metric specified in
>>>>>> the FLIP.
>>>>>> > 4. We will implement some of the metrics out of the box in the
>>>>>> default
>>>>>> > implementation of FLIP-27, as long as it is applicable.
>>>>>> >
>>>>>> > The FLIP wiki is following:
>>>>>> > https://cwiki.apache.org/confluence/display/FLINK/FLIP-33
>>>>>> > %3A+Standardize+Connector+Metrics
>>>>>> >
>>>>>> > Any thoughts?
>>>>>> >
>>>>>> > Thanks,
>>>>>> >
>>>>>> > Jiangjie (Becket) Qin
>>>>>> >
>>>>>> >
>>>>>> > On Fri, Jun 14, 2019 at 2:29 PM Piotr Nowojski <piotr@ververica.com
>>>>>> >
>>>>>> > wrote:
>>>>>> >
>>>>>> > > > we will need to revisit the convention list and adjust them
>>>>>> accordingly
>>>>>> > > when FLIP-27 is ready
>>>>>> > >
>>>>>> > >
>>>>>> > > Yes, this sounds good :)
>>>>>> > >
>>>>>> > > Piotrek
>>>>>> > >
>>>>>> > > > On 13 Jun 2019, at 13:35, Becket Qin <be...@gmail.com>
>>>>>> wrote:
>>>>>> > > >
>>>>>> > > > Hi Piotr,
>>>>>> > > >
>>>>>> > > > That's great to know. Chances are that we will need to revisit
>>>>>> the
>>>>>> > > > convention list and adjust them accordingly when FLIP-27 is
>>>>>> ready, At
>>>>>> > > that
>>>>>> > > > point we can mark some of the metrics as available by default
>>>>>> for
>>>>>> > > > connectors implementing the new interface.
>>>>>> > > >
>>>>>> > > > Thanks,
>>>>>> > > >
>>>>>> > > > Jiangjie (Becket) Qin
>>>>>> > > >
>>>>>> > > > On Thu, Jun 13, 2019 at 3:51 PM Piotr Nowojski <
>>>>>> piotr@ververica.com>
>>>>>> > > wrote:
>>>>>> > > >
>>>>>> > > >> Thanks for driving this. I’ve just noticed one small thing.
>>>>>> With new
>>>>>> > > >> SourceReader interface Flink will be able to provide
>>>>>> `idleTime` metric
>>>>>> > > >> automatically.
>>>>>> > > >>
>>>>>> > > >> Piotrek
>>>>>> > > >>
>>>>>> > > >>> On 13 Jun 2019, at 03:30, Becket Qin <be...@gmail.com>
>>>>>> wrote:
>>>>>> > > >>>
>>>>>> > > >>> Thanks all for the feedback and discussion.
>>>>>> > > >>>
>>>>>> > > >>> Since there wasn't any concern raised, I've started the
>>>>>> voting thread
>>>>>> > > for
>>>>>> > > >>> this FLIP, but please feel free to continue the discussion
>>>>>> here if
>>>>>> > you
>>>>>> > > >>> think something still needs to be addressed.
>>>>>> > > >>>
>>>>>> > > >>> Thanks,
>>>>>> > > >>>
>>>>>> > > >>> Jiangjie (Becket) Qin
>>>>>> > > >>>
>>>>>> > > >>>
>>>>>> > > >>>
>>>>>> > > >>> On Mon, Jun 10, 2019 at 9:10 AM Becket Qin <
>>>>>> becket.qin@gmail.com>
>>>>>> > > wrote:
>>>>>> > > >>>
>>>>>> > > >>>> Hi Piotr,
>>>>>> > > >>>>
>>>>>> > > >>>> Thanks for the comments. Yes, you are right. Users will have
>>>>>> to look
>>>>>> > > at
>>>>>> > > >>>> other metrics to decide whether the pipeline is healthy or
>>>>>> not in
>>>>>> > the
>>>>>> > > >> first
>>>>>> > > >>>> place before they can use the time-based metric to fix the
>>>>>> > bottleneck.
>>>>>> > > >>>>
>>>>>> > > >>>> I agree that once we have FLIP-27 ready, some of the metrics
>>>>>> can
>>>>>> > just
>>>>>> > > be
>>>>>> > > >>>> reported by the abstract implementation.
>>>>>> > > >>>>
>>>>>> > > >>>> I've updated FLIP-33 wiki page to add the pendingBytes and
>>>>>> > > >> pendingRecords
>>>>>> > > >>>> metric. Please let me know if you have any concern over the
>>>>>> updated
>>>>>> > > >> metric
>>>>>> > > >>>> convention proposal.
>>>>>> > > >>>>
>>>>>> > > >>>> @Chesnay Schepler <ch...@apache.org> @Stephan Ewen
>>>>>> > > >>>> <st...@ververica.com> will you also have time to take a
>>>>>> look at
>>>>>> > the
>>>>>> > > >>>> proposed metric convention? If there is no further concern
>>>>>> I'll
>>>>>> > start
>>>>>> > > a
>>>>>> > > >>>> voting thread for this FLIP in two days.
>>>>>> > > >>>>
>>>>>> > > >>>> Thanks,
>>>>>> > > >>>>
>>>>>> > > >>>> Jiangjie (Becket) Qin
>>>>>> > > >>>>
>>>>>> > > >>>>
>>>>>> > > >>>>
>>>>>> > > >>>> On Wed, Jun 5, 2019 at 6:54 PM Piotr Nowojski <
>>>>>> piotr@ververica.com>
>>>>>> > > >> wrote:
>>>>>> > > >>>>
>>>>>> > > >>>>> Hi Becket,
>>>>>> > > >>>>>
>>>>>> > > >>>>> Thanks for the answer :)
>>>>>> > > >>>>>
>>>>>> > > >>>>>> By time-based metric, I meant the portion of time spent on
>>>>>> > producing
>>>>>> > > >> the
>>>>>> > > >>>>>> record to downstream. For example, a source connector can
>>>>>> report
>>>>>> > > that
>>>>>> > > >>>>> it's
>>>>>> > > >>>>>> spending 80% of time to emit record to downstream
>>>>>> processing
>>>>>> > > pipeline.
>>>>>> > > >>>>> In
>>>>>> > > >>>>>> another case, a sink connector may report that its
>>>>>> spending 30% of
>>>>>> > > >> time
>>>>>> > > >>>>>> producing the records to the external system.
>>>>>> > > >>>>>>
>>>>>> > > >>>>>> This is in some sense equivalent to the buffer usage
>>>>>> metric:
>>>>>> > > >>>>>
>>>>>> > > >>>>>> - 80% of time spent on emitting records to downstream --->
>>>>>> > > downstream
>>>>>> > > >>>>>> node is bottleneck ---> output buffer is probably full.
>>>>>> > > >>>>>> - 30% of time spent on emitting records to downstream --->
>>>>>> > > downstream
>>>>>> > > >>>>>> node is not bottleneck ---> output buffer is probably not
>>>>>> full.
>>>>>> > > >>>>>
>>>>>> > > >>>>> If by “time spent on emitting records to downstream” you
>>>>>> understand
>>>>>> > > >>>>> “waiting on back pressure”, then I see your point. And I
>>>>>> agree that
>>>>>> > > >> some
>>>>>> > > >>>>> kind of ratio/time based metric gives you more information.
>>>>>> However
>>>>>> > > >> under
>>>>>> > > >>>>> “time spent on emitting records to downstream” might be
>>>>>> hidden the
>>>>>> > > >>>>> following (extreme) situation:
>>>>>> > > >>>>>
>>>>>> > > >>>>> 1. Job is barely able to handle influx of records, there is
>>>>>> 99%
>>>>>> > > >>>>> CPU/resource usage in the cluster, but nobody is
>>>>>> > > >>>>> bottlenecked/backpressured, all output buffers are empty,
>>>>>> everybody
>>>>>> > > is
>>>>>> > > >>>>> waiting in 1% of it’s time for more records to process.
>>>>>> > > >>>>> 2. 80% time can still be spent on "down stream operators”,
>>>>>> because
>>>>>> > > they
>>>>>> > > >>>>> are the CPU intensive operations, but this doesn’t mean that
>>>>>> > > >> increasing the
>>>>>> > > >>>>> parallelism down the stream will help with anything there.
>>>>>> To the
>>>>>> > > >> contrary,
>>>>>> > > >>>>> increasing parallelism of the source operator might help to
>>>>>> > increase
>>>>>> > > >>>>> resource utilisation up to 100%.
>>>>>> > > >>>>>
>>>>>> > > >>>>> However, this “time based/ratio” approach can be extended to
>>>>>> > > in/output
>>>>>> > > >>>>> buffer usage. Besides collecting an information that
>>>>>> input/output
>>>>>> > > >> buffer is
>>>>>> > > >>>>> full/empty, we can probe profile how often are buffer
>>>>>> empty/full.
>>>>>> > If
>>>>>> > > >> output
>>>>>> > > >>>>> buffer is full 1% of times, there is almost no back
>>>>>> pressure. If
>>>>>> > it’s
>>>>>> > > >> full
>>>>>> > > >>>>> 80% of times, there is some back pressure, if it’s full
>>>>>> 99.9% of
>>>>>> > > times,
>>>>>> > > >>>>> there is huge back pressure.
>>>>>> > > >>>>>
>>>>>> > > >>>>> Now for autoscaling you could compare the input & output
>>>>>> buffers
>>>>>> > fill
>>>>>> > > >>>>> ratio:
>>>>>> > > >>>>>
>>>>>> > > >>>>> 1. Both are high, the source of bottleneck is down the
>>>>>> stream
>>>>>> > > >>>>> 2. Output is low, input is high, this is the bottleneck and
>>>>>> the
>>>>>> > > higher
>>>>>> > > >>>>> the difference, the bigger source of bottleneck is this is
>>>>>> > > >> operator/task
>>>>>> > > >>>>> 3. Output is high, input is low - there was some load spike
>>>>>> that we
>>>>>> > > are
>>>>>> > > >>>>> currently finishing to process
>>>>>> > > >>>>>
>>>>>> > > >>>>>
>>>>>> > > >>>>>
>>>>>> > > >>>>> But long story short, we are probably diverging from the
>>>>>> topic of
>>>>>> > > this
>>>>>> > > >>>>> discussion, and we can discuss this at some later point.
>>>>>> > > >>>>>
>>>>>> > > >>>>> For now, for sources:
>>>>>> > > >>>>>
>>>>>> > > >>>>> as I wrote before, +1 for:
>>>>>> > > >>>>> - pending.bytes, Gauge
>>>>>> > > >>>>> - pending.messages, Gauge
>>>>>> > > >>>>>
>>>>>> > > >>>>> When we will be developing/discussing SourceReader from
>>>>>> FLIP-27 we
>>>>>> > > >> might
>>>>>> > > >>>>> then add:
>>>>>> > > >>>>>
>>>>>> > > >>>>> - in-memory.buffer.usage (0 - 100%)
>>>>>> > > >>>>>
>>>>>> > > >>>>> Which will be estimated automatically by Flink while user
>>>>>> will be
>>>>>> > > able
>>>>>> > > >> to
>>>>>> > > >>>>> override/provide better estimation.
>>>>>> > > >>>>>
>>>>>> > > >>>>> Piotrek
>>>>>> > > >>>>>
>>>>>> > > >>>>>> On 5 Jun 2019, at 05:42, Becket Qin <be...@gmail.com>
>>>>>> wrote:
>>>>>> > > >>>>>>
>>>>>> > > >>>>>> Hi Piotr,
>>>>>> > > >>>>>>
>>>>>> > > >>>>>> Thanks for the explanation. Please see some clarifications
>>>>>> below.
>>>>>> > > >>>>>>
>>>>>> > > >>>>>> By time-based metric, I meant the portion of time spent on
>>>>>> > producing
>>>>>> > > >> the
>>>>>> > > >>>>>> record to downstream. For example, a source connector can
>>>>>> report
>>>>>> > > that
>>>>>> > > >>>>> it's
>>>>>> > > >>>>>> spending 80% of time to emit record to downstream
>>>>>> processing
>>>>>> > > pipeline.
>>>>>> > > >>>>> In
>>>>>> > > >>>>>> another case, a sink connector may report that its
>>>>>> spending 30% of
>>>>>> > > >> time
>>>>>> > > >>>>>> producing the records to the external system.
>>>>>> > > >>>>>>
>>>>>> > > >>>>>> This is in some sense equivalent to the buffer usage
>>>>>> metric:
>>>>>> > > >>>>>> - 80% of time spent on emitting records to downstream --->
>>>>>> > > downstream
>>>>>> > > >>>>>> node is bottleneck ---> output buffer is probably full.
>>>>>> > > >>>>>> - 30% of time spent on emitting records to downstream --->
>>>>>> > > downstream
>>>>>> > > >>>>>> node is not bottleneck ---> output buffer is probably not
>>>>>> full.
>>>>>> > > >>>>>>
>>>>>> > > >>>>>> However, the time-based metric has a few advantages that
>>>>>> the
>>>>>> > buffer
>>>>>> > > >>>>> usage
>>>>>> > > >>>>>> metric may not have.
>>>>>> > > >>>>>>
>>>>>> > > >>>>>> 1. Buffer usage metric may not be applicable to all the
>>>>>> connector
>>>>>> > > >>>>>> implementations, while reporting time-based metric are
>>>>>> always
>>>>>> > > doable.
>>>>>> > > >>>>>> Some source connectors may not have any input buffer, or
>>>>>> they may
>>>>>> > > use
>>>>>> > > >>>>> some
>>>>>> > > >>>>>> third party library that does not expose the input buffer
>>>>>> at all.
>>>>>> > > >>>>>> Similarly, for sink connectors, the implementation may not
>>>>>> have
>>>>>> > any
>>>>>> > > >>>>> output
>>>>>> > > >>>>>> buffer, or the third party library does not expose such
>>>>>> buffer.
>>>>>> > > >>>>>>
>>>>>> > > >>>>>> 2. Although both type of metrics can detect bottleneck,
>>>>>> time-based
>>>>>> > > >>>>> metrics
>>>>>> > > >>>>>> can be used to generate a more informed action to remove
>>>>>> the
>>>>>> > > >> bottleneck.
>>>>>> > > >>>>>> For example, when the downstream is bottleneck, the output
>>>>>> buffer
>>>>>> > > >> usage
>>>>>> > > >>>>>> metric is likely to be 100%, and the input buffer usage
>>>>>> might be
>>>>>> > 0%.
>>>>>> > > >>>>> That
>>>>>> > > >>>>>> means we don't know what is the suitable parallelism to
>>>>>> lift the
>>>>>> > > >>>>>> bottleneck. The time-based metric, on the other hand,
>>>>>> would give
>>>>>> > > >> useful
>>>>>> > > >>>>>> information, e.g. if 80% of time was spent on emitting
>>>>>> records, we
>>>>>> > > can
>>>>>> > > >>>>>> roughly increase the downstream node parallelism by 4
>>>>>> times.
>>>>>> > > >>>>>>
>>>>>> > > >>>>>> Admittedly, the time-based metrics are more expensive than
>>>>>> buffer
>>>>>> > > >>>>> usage. So
>>>>>> > > >>>>>> we may have to do some sampling to reduce the cost. But in
>>>>>> > general,
>>>>>> > > >>>>> using
>>>>>> > > >>>>>> time-based metrics seems worth adding.
>>>>>> > > >>>>>>
>>>>>> > > >>>>>> That being said, I don't think buffer usage metric and
>>>>>> time-based
>>>>>> > > >>>>> metrics
>>>>>> > > >>>>>> are mutually exclusive. We can probably have both. It is
>>>>>> just that
>>>>>> > > in
>>>>>> > > >>>>>> practice, features like auto-scaling might prefer
>>>>>> time-based
>>>>>> > metrics
>>>>>> > > >> for
>>>>>> > > >>>>>> the reason stated above.
>>>>>> > > >>>>>>
>>>>>> > > >>>>>>> 1. Define the metrics that would allow us to manually
>>>>>> detect
>>>>>> > > >>>>> bottlenecks.
>>>>>> > > >>>>>> As I wrote, we already have them in most of the places,
>>>>>> except of
>>>>>> > > >>>>>> sources/sinks.
>>>>>> > > >>>>>>> 2. Use those metrics, to automatically detect bottlenecks.
>>>>>> > > Currently
>>>>>> > > >> we
>>>>>> > > >>>>>> are only automatically detecting back pressure and
>>>>>> reporting it to
>>>>>> > > the
>>>>>> > > >>>>> user
>>>>>> > > >>>>>> in web UI (is it exposed as a metric at all?). Detecting
>>>>>> the root
>>>>>> > > >> cause
>>>>>> > > >>>>> of
>>>>>> > > >>>>>> the back pressure (bottleneck) is one step further.
>>>>>> > > >>>>>>> 3. Use the knowledge about where exactly the bottleneck is
>>>>>> > located,
>>>>>> > > >> to
>>>>>> > > >>>>>> try to do something with it.
>>>>>> > > >>>>>>
>>>>>> > > >>>>>> As explained above, I think time-based metric also
>>>>>> addresses item
>>>>>> > 1
>>>>>> > > >> and
>>>>>> > > >>>>>> item 2.
>>>>>> > > >>>>>>
>>>>>> > > >>>>>> Any thoughts？
>>>>>> > > >>>>>>
>>>>>> > > >>>>>> Thanks,
>>>>>> > > >>>>>>
>>>>>> > > >>>>>> Jiangjie (Becket) Qin
>>>>>> > > >>>>>>
>>>>>> > > >>>>>>
>>>>>> > > >>>>>>
>>>>>> > > >>>>>> On Mon, Jun 3, 2019 at 4:14 PM Piotr Nowojski <
>>>>>> > piotr@ververica.com>
>>>>>> > > >>>>> wrote:
>>>>>> > > >>>>>>
>>>>>> > > >>>>>>> Hi again :)
>>>>>> > > >>>>>>>
>>>>>> > > >>>>>>>> - pending.bytes, Gauge
>>>>>> > > >>>>>>>> - pending.messages, Gauge
>>>>>> > > >>>>>>>
>>>>>> > > >>>>>>>
>>>>>> > > >>>>>>> +1
>>>>>> > > >>>>>>>
>>>>>> > > >>>>>>> And true, instead of overloading one of the metric it is
>>>>>> better
>>>>>> > > when
>>>>>> > > >>>>> user
>>>>>> > > >>>>>>> can choose to provide only one of them.
>>>>>> > > >>>>>>>
>>>>>> > > >>>>>>> Re 2:
>>>>>> > > >>>>>>>
>>>>>> > > >>>>>>>> If I understand correctly, this metric along with the
>>>>>> pending
>>>>>> > > >> mesages
>>>>>> > > >>>>> /
>>>>>> > > >>>>>>>> bytes would answer the questions of:
>>>>>> > > >>>>>>>
>>>>>> > > >>>>>>>> - Does the connector consume fast enough? Lagging behind
>>>>>> + empty
>>>>>> > > >>>>> buffer
>>>>>> > > >>>>>>> =
>>>>>> > > >>>>>>>> cannot consume fast enough.
>>>>>> > > >>>>>>>> - Does the connector emit fast enough? Lagging behind +
>>>>>> full
>>>>>> > > buffer
>>>>>> > > >> =
>>>>>> > > >>>>>>>> cannot emit fast enough, i.e. the Flink pipeline is slow.
>>>>>> > > >>>>>>>
>>>>>> > > >>>>>>> Yes, exactly. This can also be used to support decisions
>>>>>> like
>>>>>> > > >> changing
>>>>>> > > >>>>> the
>>>>>> > > >>>>>>> parallelism of the sources and/or down stream operators.
>>>>>> > > >>>>>>>
>>>>>> > > >>>>>>> I’m not sure if I understand your proposal with time based
>>>>>> > > >>>>> measurements.
>>>>>> > > >>>>>>> Maybe I’m missing something, but I do not see how
>>>>>> measuring time
>>>>>> > > >> alone
>>>>>> > > >>>>>>> could answer the problem: where is the bottleneck. Time
>>>>>> spent on
>>>>>> > > the
>>>>>> > > >>>>>>> next/emit might be short or long (depending on how heavy
>>>>>> to
>>>>>> > process
>>>>>> > > >> the
>>>>>> > > >>>>>>> record is) and the source can still be bottlenecked/back
>>>>>> > pressured
>>>>>> > > or
>>>>>> > > >>>>> not.
>>>>>> > > >>>>>>> Usually the easiest and the most reliable way how to
>>>>>> detect
>>>>>> > > >>>>> bottlenecks is
>>>>>> > > >>>>>>> by checking usage of input & output buffers, since when
>>>>>> input
>>>>>> > > buffer
>>>>>> > > >> is
>>>>>> > > >>>>>>> full while output buffer is empty, that’s the definition
>>>>>> of a
>>>>>> > > >>>>> bottleneck.
>>>>>> > > >>>>>>> Also this is usually very easy and cheap to measure (it
>>>>>> works
>>>>>> > > >>>>> effectively
>>>>>> > > >>>>>>> the same way as current’s Flink back pressure monitoring,
>>>>>> but
>>>>>> > more
>>>>>> > > >>>>> cleanly,
>>>>>> > > >>>>>>> without probing thread’s stack traces).
>>>>>> > > >>>>>>>
>>>>>> > > >>>>>>> Also keep in mind that we are already using the buffer
>>>>>> usage
>>>>>> > > metrics
>>>>>> > > >>>>> for
>>>>>> > > >>>>>>> detecting the bottlenecks in Flink’s internal network
>>>>>> exchanges
>>>>>> > > >> (manual
>>>>>> > > >>>>>>> work). That’s the reason why I wanted to extend this to
>>>>>> > > >> sources/sinks,
>>>>>> > > >>>>>>> since they are currently our blind spot.
>>>>>> > > >>>>>>>
>>>>>> > > >>>>>>>> One feature we are currently working on to scale Flink
>>>>>> > > automatically
>>>>>> > > >>>>>>> relies
>>>>>> > > >>>>>>>> on some metrics answering the same question
>>>>>> > > >>>>>>>
>>>>>> > > >>>>>>> That would be very helpful feature. I think in order to
>>>>>> achieve
>>>>>> > > that
>>>>>> > > >> we
>>>>>> > > >>>>>>> would need to:
>>>>>> > > >>>>>>> 1. Define the metrics that would allow us to manually
>>>>>> detect
>>>>>> > > >>>>> bottlenecks.
>>>>>> > > >>>>>>> As I wrote, we already have them in most of the places,
>>>>>> except of
>>>>>> > > >>>>>>> sources/sinks.
>>>>>> > > >>>>>>> 2. Use those metrics, to automatically detect bottlenecks.
>>>>>> > > Currently
>>>>>> > > >> we
>>>>>> > > >>>>>>> are only automatically detecting back pressure and
>>>>>> reporting it
>>>>>> > to
>>>>>> > > >> the
>>>>>> > > >>>>> user
>>>>>> > > >>>>>>> in web UI (is it exposed as a metric at all?). Detecting
>>>>>> the root
>>>>>> > > >>>>> cause of
>>>>>> > > >>>>>>> the back pressure (bottleneck) is one step further.
>>>>>> > > >>>>>>> 3. Use the knowledge about where exactly the bottleneck is
>>>>>> > located,
>>>>>> > > >> to
>>>>>> > > >>>>> try
>>>>>> > > >>>>>>> to do something with it.
>>>>>> > > >>>>>>>
>>>>>> > > >>>>>>> I think you are aiming for point 3., but before we reach
>>>>>> it, we
>>>>>> > are
>>>>>> > > >>>>> still
>>>>>> > > >>>>>>> missing 1. & 2. Also even if we have 3., there is a value
>>>>>> in 1 &
>>>>>> > 2
>>>>>> > > >> for
>>>>>> > > >>>>>>> manual analysis/dashboards.
>>>>>> > > >>>>>>>
>>>>>> > > >>>>>>> However, having the knowledge of where the bottleneck is,
>>>>>> doesn’t
>>>>>> > > >>>>>>> necessarily mean that we know what we can do about it. For
>>>>>> > example
>>>>>> > > >>>>>>> increasing parallelism might or might not help with
>>>>>> anything
>>>>>> > (data
>>>>>> > > >>>>> skew,
>>>>>> > > >>>>>>> bottleneck on some resource that does not scale), but
>>>>>> this remark
>>>>>> > > >>>>> applies
>>>>>> > > >>>>>>> always, regardless of the way how did we detect the
>>>>>> bottleneck.
>>>>>> > > >>>>>>>
>>>>>> > > >>>>>>> Piotrek
>>>>>> > > >>>>>>>
>>>>>> > > >>>>>>>> On 3 Jun 2019, at 06:16, Becket Qin <
>>>>>> becket.qin@gmail.com>
>>>>>> > wrote:
>>>>>> > > >>>>>>>>
>>>>>> > > >>>>>>>> Hi Piotr,
>>>>>> > > >>>>>>>>
>>>>>> > > >>>>>>>> Thanks for the suggestion. Some thoughts below:
>>>>>> > > >>>>>>>>
>>>>>> > > >>>>>>>> Re 1: The pending messages / bytes.
>>>>>> > > >>>>>>>> I completely agree these are very useful metrics and we
>>>>>> should
>>>>>> > > >> expect
>>>>>> > > >>>>> the
>>>>>> > > >>>>>>>> connector to report. WRT the way to expose them, it
>>>>>> seems more
>>>>>> > > >>>>> consistent
>>>>>> > > >>>>>>>> to add two metrics instead of adding a method (unless
>>>>>> there are
>>>>>> > > >> other
>>>>>> > > >>>>> use
>>>>>> > > >>>>>>>> cases other than metric reporting). So we can add the
>>>>>> following
>>>>>> > > two
>>>>>> > > >>>>>>> metrics.
>>>>>> > > >>>>>>>> - pending.bytes, Gauge
>>>>>> > > >>>>>>>> - pending.messages, Gauge
>>>>>> > > >>>>>>>> Applicable connectors can choose to report them. These
>>>>>> two
>>>>>> > metrics
>>>>>> > > >>>>> along
>>>>>> > > >>>>>>>> with latency should be sufficient for users to
>>>>>> understand the
>>>>>> > > >> progress
>>>>>> > > >>>>>>> of a
>>>>>> > > >>>>>>>> connector.
>>>>>> > > >>>>>>>>
>>>>>> > > >>>>>>>>
>>>>>> > > >>>>>>>> Re 2: Number of buffered data in-memory of the connector
>>>>>> > > >>>>>>>> If I understand correctly, this metric along with the
>>>>>> pending
>>>>>> > > >> mesages
>>>>>> > > >>>>> /
>>>>>> > > >>>>>>>> bytes would answer the questions of:
>>>>>> > > >>>>>>>> - Does the connector consume fast enough? Lagging behind
>>>>>> + empty
>>>>>> > > >>>>> buffer
>>>>>> > > >>>>>>> =
>>>>>> > > >>>>>>>> cannot consume fast enough.
>>>>>> > > >>>>>>>> - Does the connector emit fast enough? Lagging behind +
>>>>>> full
>>>>>> > > buffer
>>>>>> > > >> =
>>>>>> > > >>>>>>>> cannot emit fast enough, i.e. the Flink pipeline is slow.
>>>>>> > > >>>>>>>>
>>>>>> > > >>>>>>>> One feature we are currently working on to scale Flink
>>>>>> > > automatically
>>>>>> > > >>>>>>> relies
>>>>>> > > >>>>>>>> on some metrics answering the same question, more
>>>>>> specifically,
>>>>>> > we
>>>>>> > > >> are
>>>>>> > > >>>>>>>> profiling the time spent on .next() method (time to
>>>>>> consume) and
>>>>>> > > the
>>>>>> > > >>>>> time
>>>>>> > > >>>>>>>> spent on .collect() method (time to emit / process). One
>>>>>> > advantage
>>>>>> > > >> of
>>>>>> > > >>>>>>> such
>>>>>> > > >>>>>>>> method level time cost allows us to calculate the
>>>>>> parallelism
>>>>>> > > >>>>> required to
>>>>>> > > >>>>>>>> keep up in case their is a lag.
>>>>>> > > >>>>>>>>
>>>>>> > > >>>>>>>> However, one concern I have regarding such metric is
>>>>>> that they
>>>>>> > are
>>>>>> > > >>>>>>>> implementation specific. Either profiling on the method
>>>>>> time, or
>>>>>> > > >>>>>>> reporting
>>>>>> > > >>>>>>>> buffer usage assumes the connector are implemented in
>>>>>> such a
>>>>>> > way.
>>>>>> > > A
>>>>>> > > >>>>>>>> slightly better solution might be have the following
>>>>>> metric:
>>>>>> > > >>>>>>>>
>>>>>> > > >>>>>>>> - EmitTimeRatio (or FetchTimeRatio): The time spent on
>>>>>> emitting
>>>>>> > > >>>>>>>> records / Total time elapsed.
>>>>>> > > >>>>>>>>
>>>>>> > > >>>>>>>> This assumes that the source connectors have to emit the
>>>>>> records
>>>>>> > > to
>>>>>> > > >>>>> the
>>>>>> > > >>>>>>>> downstream at some point. The emission may take some
>>>>>> time ( e.g.
>>>>>> > > go
>>>>>> > > >>>>>>> through
>>>>>> > > >>>>>>>> chained operators). And the rest of the time are spent to
>>>>>> > prepare
>>>>>> > > >> the
>>>>>> > > >>>>>>>> record to emit, including time for consuming and format
>>>>>> > > conversion,
>>>>>> > > >>>>> etc.
>>>>>> > > >>>>>>>> Ideally, we'd like to see the time spent on record fetch
>>>>>> and
>>>>>> > emit
>>>>>> > > to
>>>>>> > > >>>>> be
>>>>>> > > >>>>>>>> about the same, so no one is bottleneck for the other.
>>>>>> > > >>>>>>>>
>>>>>> > > >>>>>>>> The downside of these time based metrics is additional
>>>>>> overhead
>>>>>> > to
>>>>>> > > >> get
>>>>>> > > >>>>>>> the
>>>>>> > > >>>>>>>> time, therefore sampling might be needed. But in
>>>>>> practice I feel
>>>>>> > > >> such
>>>>>> > > >>>>>>> time
>>>>>> > > >>>>>>>> based metric might be more useful if we want to take
>>>>>> action.
>>>>>> > > >>>>>>>>
>>>>>> > > >>>>>>>>
>>>>>> > > >>>>>>>> I think we should absolutely add metrics in (1) to the
>>>>>> metric
>>>>>> > > >>>>> convention.
>>>>>> > > >>>>>>>> We could also add the metrics mentioned in (2) if we
>>>>>> reach
>>>>>> > > consensus
>>>>>> > > >>>>> on
>>>>>> > > >>>>>>>> that. What do you think?
>>>>>> > > >>>>>>>>
>>>>>> > > >>>>>>>> Thanks,
>>>>>> > > >>>>>>>>
>>>>>> > > >>>>>>>> Jiangjie (Becket) Qin
>>>>>> > > >>>>>>>>
>>>>>> > > >>>>>>>>
>>>>>> > > >>>>>>>> On Fri, May 31, 2019 at 4:26 PM Piotr Nowojski <
>>>>>> > > piotr@ververica.com
>>>>>> > > >>>
>>>>>> > > >>>>>>> wrote:
>>>>>> > > >>>>>>>>
>>>>>> > > >>>>>>>>> Hey Becket,
>>>>>> > > >>>>>>>>>
>>>>>> > > >>>>>>>>> Re 1a) and 1b) +1 from my side.
>>>>>> > > >>>>>>>>>
>>>>>> > > >>>>>>>>> I’ve discussed this issue:
>>>>>> > > >>>>>>>>>
>>>>>> > > >>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>> 2. It would be nice to have metrics, that allow us
>>>>>> to check
>>>>>> > > the
>>>>>> > > >>>>> cause
>>>>>> > > >>>>>>>>> of
>>>>>> > > >>>>>>>>>>>> back pressure:
>>>>>> > > >>>>>>>>>>>> a) for sources, length of input queue (in bytes? Or
>>>>>> boolean
>>>>>> > > >>>>>>>>>>>> hasSomethingl/isEmpty)
>>>>>> > > >>>>>>>>>>>> b) for sinks, length of output queue (in bytes? Or
>>>>>> boolean
>>>>>> > > >>>>>>>>>>>> hasSomething/isEmpty)
>>>>>> > > >>>>>>>>>
>>>>>> > > >>>>>>>>> With Nico at some lengths and he also saw the benefits
>>>>>> of them.
>>>>>> > > We
>>>>>> > > >>>>> also
>>>>>> > > >>>>>>>>> have more concrete proposal for that.
>>>>>> > > >>>>>>>>>
>>>>>> > > >>>>>>>>> Actually there are two really useful metrics, that we
>>>>>> are
>>>>>> > missing
>>>>>> > > >>>>>>>>> currently:
>>>>>> > > >>>>>>>>>
>>>>>> > > >>>>>>>>> 1. Number of data/records/bytes in the backlog to
>>>>>> process. For
>>>>>> > > >>>>> example
>>>>>> > > >>>>>>>>> remaining number of bytes in unread files. Or pending
>>>>>> data in
>>>>>> > > Kafka
>>>>>> > > >>>>>>> topics.
>>>>>> > > >>>>>>>>> 2. Number of buffered data in-memory of the connector,
>>>>>> that are
>>>>>> > > >>>>> waiting
>>>>>> > > >>>>>>> to
>>>>>> > > >>>>>>>>> be processed pushed to Flink pipeline.
>>>>>> > > >>>>>>>>>
>>>>>> > > >>>>>>>>> Re 1:
>>>>>> > > >>>>>>>>> This would have to be a metric provided directly by a
>>>>>> > connector.
>>>>>> > > It
>>>>>> > > >>>>>>> could
>>>>>> > > >>>>>>>>> be an undefined `int`:
>>>>>> > > >>>>>>>>>
>>>>>> > > >>>>>>>>> `int backlog` - estimate of pending work.
>>>>>> > > >>>>>>>>>
>>>>>> > > >>>>>>>>> “Undefined” meaning that it would be up to a connector
>>>>>> to
>>>>>> > decided
>>>>>> > > >>>>>>> whether
>>>>>> > > >>>>>>>>> it’s measured in bytes, records, pending files or
>>>>>> whatever it
>>>>>> > is
>>>>>> > > >>>>>>> possible
>>>>>> > > >>>>>>>>> to provide by the connector. This is because I assume
>>>>>> not every
>>>>>> > > >>>>>>> connector
>>>>>> > > >>>>>>>>> can provide exact number and for some of them it might
>>>>>> be
>>>>>> > > >> impossible
>>>>>> > > >>>>> to
>>>>>> > > >>>>>>>>> provide records number of bytes count.
>>>>>> > > >>>>>>>>>
>>>>>> > > >>>>>>>>> Re 2:
>>>>>> > > >>>>>>>>> This metric could be either provided by a connector, or
>>>>>> > > calculated
>>>>>> > > >>>>>>> crudely
>>>>>> > > >>>>>>>>> by Flink:
>>>>>> > > >>>>>>>>>
>>>>>> > > >>>>>>>>> `float bufferUsage` - value from [0.0, 1.0] range
>>>>>> > > >>>>>>>>>
>>>>>> > > >>>>>>>>> Percentage of used in memory buffers, like in Kafka’s
>>>>>> handover.
>>>>>> > > >>>>>>>>>
>>>>>> > > >>>>>>>>> It could be crudely implemented by Flink with FLIP-27
>>>>>> > > >>>>>>>>> SourceReader#isAvailable. If SourceReader is not
>>>>>> available
>>>>>> > > reported
>>>>>> > > >>>>>>>>> `bufferUsage` could be 0.0. If it is available, it
>>>>>> could be
>>>>>> > 1.0.
>>>>>> > > I
>>>>>> > > >>>>> think
>>>>>> > > >>>>>>>>> this would be a good enough estimation for most of the
>>>>>> use
>>>>>> > cases
>>>>>> > > >>>>> (that
>>>>>> > > >>>>>>>>> could be overloaded and implemented better if desired).
>>>>>> > > Especially
>>>>>> > > >>>>>>> since we
>>>>>> > > >>>>>>>>> are reporting only probed values: if probed values are
>>>>>> almost
>>>>>> > > >> always
>>>>>> > > >>>>>>> “1.0”,
>>>>>> > > >>>>>>>>> it would mean that we have a back pressure. If they are
>>>>>> almost
>>>>>> > > >> always
>>>>>> > > >>>>>>>>> “0.0”, there is probably no back pressure at the
>>>>>> sources.
>>>>>> > > >>>>>>>>>
>>>>>> > > >>>>>>>>> What do you think about this?
>>>>>> > > >>>>>>>>>
>>>>>> > > >>>>>>>>> Piotrek
>>>>>> > > >>>>>>>>>
>>>>>> > > >>>>>>>>>> On 30 May 2019, at 11:41, Becket Qin <
>>>>>> becket.qin@gmail.com>
>>>>>> > > >> wrote:
>>>>>> > > >>>>>>>>>>
>>>>>> > > >>>>>>>>>> Hi all,
>>>>>> > > >>>>>>>>>>
>>>>>> > > >>>>>>>>>> Thanks a lot for all the feedback and comments. I'd
>>>>>> like to
>>>>>> > > >> continue
>>>>>> > > >>>>>>> the
>>>>>> > > >>>>>>>>>> discussion on this FLIP.
>>>>>> > > >>>>>>>>>>
>>>>>> > > >>>>>>>>>> I updated the FLIP-33 wiki to remove all the histogram
>>>>>> metrics
>>>>>> > > >> from
>>>>>> > > >>>>> the
>>>>>> > > >>>>>>>>>> first version of metric convention due to the
>>>>>> performance
>>>>>> > > concern.
>>>>>> > > >>>>> The
>>>>>> > > >>>>>>>>> plan
>>>>>> > > >>>>>>>>>> is to introduce them later when we have a mechanism to
>>>>>> opt
>>>>>> > > in/out
>>>>>> > > >>>>>>>>> metrics.
>>>>>> > > >>>>>>>>>> At that point, users can decide whether they want to
>>>>>> pay the
>>>>>> > > cost
>>>>>> > > >> to
>>>>>> > > >>>>>>> get
>>>>>> > > >>>>>>>>>> the metric or not.
>>>>>> > > >>>>>>>>>>
>>>>>> > > >>>>>>>>>> As Stephan suggested, for this FLIP, let's first try
>>>>>> to agree
>>>>>> > on
>>>>>> > > >> the
>>>>>> > > >>>>>>>>> small
>>>>>> > > >>>>>>>>>> list of conventional metrics that connectors should
>>>>>> follow.
>>>>>> > > >>>>>>>>>> Just to be clear, the purpose of the convention is not
>>>>>> to
>>>>>> > > enforce
>>>>>> > > >>>>> every
>>>>>> > > >>>>>>>>>> connector to report all these metrics, but to provide a
>>>>>> > guidance
>>>>>> > > >> in
>>>>>> > > >>>>>>> case
>>>>>> > > >>>>>>>>>> these metrics are reported by some connectors.
>>>>>> > > >>>>>>>>>>
>>>>>> > > >>>>>>>>>>
>>>>>> > > >>>>>>>>>> @ Stephan & Chesnay,
>>>>>> > > >>>>>>>>>>
>>>>>> > > >>>>>>>>>> Regarding the duplication of `RecordsIn` metric in
>>>>>> operator /
>>>>>> > > task
>>>>>> > > >>>>>>>>>> IOMetricGroups, from what I understand, for source
>>>>>> operator,
>>>>>> > it
>>>>>> > > is
>>>>>> > > >>>>>>>>> actually
>>>>>> > > >>>>>>>>>> the SourceFunction that reports the operator level
>>>>>> > > >>>>>>>>>> RecordsIn/RecordsInPerSecond metric. So they are
>>>>>> essentially
>>>>>> > the
>>>>>> > > >>>>> same
>>>>>> > > >>>>>>>>>> metric in the operator level IOMetricGroup. Similarly
>>>>>> for the
>>>>>> > > Sink
>>>>>> > > >>>>>>>>>> operator, the operator level
>>>>>> RecordsOut/RecordsOutPerSecond
>>>>>> > > >> metrics
>>>>>> > > >>>>> are
>>>>>> > > >>>>>>>>>> also reported by the Sink function. I marked them as
>>>>>> existing
>>>>>> > in
>>>>>> > > >> the
>>>>>> > > >>>>>>>>>> FLIP-33 wiki page. Please let me know if I
>>>>>> misunderstood.
>>>>>> > > >>>>>>>>>>
>>>>>> > > >>>>>>>>>> Thanks,
>>>>>> > > >>>>>>>>>>
>>>>>> > > >>>>>>>>>> Jiangjie (Becket) Qin
>>>>>> > > >>>>>>>>>>
>>>>>> > > >>>>>>>>>>
>>>>>> > > >>>>>>>>>> On Thu, May 30, 2019 at 5:16 PM Becket Qin <
>>>>>> > > becket.qin@gmail.com>
>>>>>> > > >>>>>>> wrote:
>>>>>> > > >>>>>>>>>>
>>>>>> > > >>>>>>>>>>> Hi Piotr,
>>>>>> > > >>>>>>>>>>>
>>>>>> > > >>>>>>>>>>> Thanks a lot for the feedback.
>>>>>> > > >>>>>>>>>>>
>>>>>> > > >>>>>>>>>>> 1a) I guess you are referring to the part that
>>>>>> "original
>>>>>> > system
>>>>>> > > >>>>>>> specific
>>>>>> > > >>>>>>>>>>> metrics should also be reported". The performance
>>>>>> impact
>>>>>> > > depends
>>>>>> > > >> on
>>>>>> > > >>>>>>> the
>>>>>> > > >>>>>>>>>>> implementation. An efficient implementation would
>>>>>> only record
>>>>>> > > the
>>>>>> > > >>>>>>> metric
>>>>>> > > >>>>>>>>>>> once, but report them with two different metric
>>>>>> names. This
>>>>>> > is
>>>>>> > > >>>>>>> unlikely
>>>>>> > > >>>>>>>>> to
>>>>>> > > >>>>>>>>>>> hurt performance.
>>>>>> > > >>>>>>>>>>>
>>>>>> > > >>>>>>>>>>> 1b) Yes, I agree that we should avoid adding overhead
>>>>>> to the
>>>>>> > > >>>>> critical
>>>>>> > > >>>>>>>>> path
>>>>>> > > >>>>>>>>>>> by all means. This is sometimes a tradeoff, running
>>>>>> blindly
>>>>>> > > >> without
>>>>>> > > >>>>>>> any
>>>>>> > > >>>>>>>>>>> metric gives best performance, but sometimes might be
>>>>>> > > frustrating
>>>>>> > > >>>>> when
>>>>>> > > >>>>>>>>> we
>>>>>> > > >>>>>>>>>>> debug some issues.
>>>>>> > > >>>>>>>>>>>
>>>>>> > > >>>>>>>>>>> 2. The metrics are indeed very useful. Are they
>>>>>> supposed to
>>>>>> > be
>>>>>> > > >>>>>>> reported
>>>>>> > > >>>>>>>>> by
>>>>>> > > >>>>>>>>>>> the connectors or Flink itself? At this point FLIP-33
>>>>>> is more
>>>>>> > > >>>>> focused
>>>>>> > > >>>>>>> on
>>>>>> > > >>>>>>>>>>> provide a guidance to the connector authors on the
>>>>>> metrics
>>>>>> > > >>>>> reporting.
>>>>>> > > >>>>>>>>> That
>>>>>> > > >>>>>>>>>>> said, after FLIP-27, I think we should absolutely
>>>>>> report
>>>>>> > these
>>>>>> > > >>>>> metrics
>>>>>> > > >>>>>>>>> in
>>>>>> > > >>>>>>>>>>> the abstract implementation. In any case, the metric
>>>>>> > convention
>>>>>> > > >> in
>>>>>> > > >>>>>>> this
>>>>>> > > >>>>>>>>>>> list are expected to evolve over time.
>>>>>> > > >>>>>>>>>>>
>>>>>> > > >>>>>>>>>>> Thanks,
>>>>>> > > >>>>>>>>>>>
>>>>>> > > >>>>>>>>>>> Jiangjie (Becket) Qin
>>>>>> > > >>>>>>>>>>>
>>>>>> > > >>>>>>>>>>> On Tue, May 28, 2019 at 6:24 PM Piotr Nowojski <
>>>>>> > > >>>>> piotr@ververica.com>
>>>>>> > > >>>>>>>>>>> wrote:
>>>>>> > > >>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>> Hi,
>>>>>> > > >>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>> Thanks for the proposal and driving the effort here
>>>>>> Becket
>>>>>> > :)
>>>>>> > > >> I’ve
>>>>>> > > >>>>>>> read
>>>>>> > > >>>>>>>>>>>> through the FLIP-33 [1], and here are couple of my
>>>>>> thoughts.
>>>>>> > > >>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>> Big +1 for standardising the metric names between
>>>>>> > connectors,
>>>>>> > > it
>>>>>> > > >>>>> will
>>>>>> > > >>>>>>>>>>>> definitely help us and users a lot.
>>>>>> > > >>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>> Issues/questions/things to discuss that I’ve thought
>>>>>> of:
>>>>>> > > >>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>> 1a. If we are about to duplicate some metrics, can
>>>>>> this
>>>>>> > > become a
>>>>>> > > >>>>>>>>>>>> performance issue?
>>>>>> > > >>>>>>>>>>>> 1b. Generally speaking, we should make sure that
>>>>>> collecting
>>>>>> > > >> those
>>>>>> > > >>>>>>>>> metrics
>>>>>> > > >>>>>>>>>>>> is as non intrusive as possible, especially that
>>>>>> they will
>>>>>> > > need
>>>>>> > > >>>>> to be
>>>>>> > > >>>>>>>>>>>> updated once per record. (They might be collected
>>>>>> more
>>>>>> > rarely
>>>>>> > > >> with
>>>>>> > > >>>>>>> some
>>>>>> > > >>>>>>>>>>>> overhead, but the hot path of updating it per record
>>>>>> will
>>>>>> > need
>>>>>> > > >> to
>>>>>> > > >>>>> be
>>>>>> > > >>>>>>> as
>>>>>> > > >>>>>>>>>>>> quick as possible). That includes both avoiding heavy
>>>>>> > > >> computation
>>>>>> > > >>>>> on
>>>>>> > > >>>>>>>>> per
>>>>>> > > >>>>>>>>>>>> record path: histograms?, measuring time for time
>>>>>> based
>>>>>> > > metrics
>>>>>> > > >>>>> (per
>>>>>> > > >>>>>>>>>>>> second) (System.currentTimeMillis() depending on the
>>>>>> > > >>>>> implementation
>>>>>> > > >>>>>>> can
>>>>>> > > >>>>>>>>>>>> invoke a system call)
>>>>>> > > >>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>> 2. It would be nice to have metrics, that allow us
>>>>>> to check
>>>>>> > > the
>>>>>> > > >>>>> cause
>>>>>> > > >>>>>>>>> of
>>>>>> > > >>>>>>>>>>>> back pressure:
>>>>>> > > >>>>>>>>>>>> a) for sources, length of input queue (in bytes? Or
>>>>>> boolean
>>>>>> > > >>>>>>>>>>>> hasSomethingl/isEmpty)
>>>>>> > > >>>>>>>>>>>> b) for sinks, length of output queue (in bytes? Or
>>>>>> boolean
>>>>>> > > >>>>>>>>>>>> hasSomething/isEmpty)
>>>>>> > > >>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>> a) is useful in a scenario when we are processing
>>>>>> backlog of
>>>>>> > > >>>>> records,
>>>>>> > > >>>>>>>>> all
>>>>>> > > >>>>>>>>>>>> of the internal Flink’s input/output network buffers
>>>>>> are
>>>>>> > > empty,
>>>>>> > > >>>>> and
>>>>>> > > >>>>>>> we
>>>>>> > > >>>>>>>>> want
>>>>>> > > >>>>>>>>>>>> to check whether the external source system is the
>>>>>> > bottleneck
>>>>>> > > >>>>>>> (source’s
>>>>>> > > >>>>>>>>>>>> input queue will be empty), or if the Flink’s
>>>>>> connector is
>>>>>> > the
>>>>>> > > >>>>>>>>> bottleneck
>>>>>> > > >>>>>>>>>>>> (source’s input queues will be full).
>>>>>> > > >>>>>>>>>>>> b) similar story. Backlog of records, but this time
>>>>>> all of
>>>>>> > the
>>>>>> > > >>>>>>> internal
>>>>>> > > >>>>>>>>>>>> Flink’s input/ouput network buffers are full, and we
>>>>>> want o
>>>>>> > > >> check
>>>>>> > > >>>>>>>>> whether
>>>>>> > > >>>>>>>>>>>> the external sink system is the bottleneck (sink
>>>>>> output
>>>>>> > queues
>>>>>> > > >> are
>>>>>> > > >>>>>>>>> full),
>>>>>> > > >>>>>>>>>>>> or if the Flink’s connector is the bottleneck
>>>>>> (sink’s output
>>>>>> > > >>>>> queues
>>>>>> > > >>>>>>>>> will be
>>>>>> > > >>>>>>>>>>>> empty)
>>>>>> > > >>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>> It might be sometimes difficult to provide those
>>>>>> metrics, so
>>>>>> > > >> they
>>>>>> > > >>>>>>> could
>>>>>> > > >>>>>>>>>>>> be optional, but if we could provide them, it would
>>>>>> be
>>>>>> > really
>>>>>> > > >>>>>>> helpful.
>>>>>> > > >>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>> Piotrek
>>>>>> > > >>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>> [1]
>>>>>> > > >>>>>>>>>>>>
>>>>>> > > >>>>>>>>>
>>>>>> > > >>>>>>>
>>>>>> > > >>>>>
>>>>>> > > >>
>>>>>> > >
>>>>>> >
>>>>>> https://cwiki.apache.org/confluence/display/FLINK/FLIP-33:+Standardize+Connector+Metrics
>>>>>> > > >>>>>>>>>>>> <
>>>>>> > > >>>>>>>>>>>>
>>>>>> > > >>>>>>>>>
>>>>>> > > >>>>>>>
>>>>>> > > >>>>>
>>>>>> > > >>
>>>>>> > >
>>>>>> >
>>>>>> https://cwiki.apache.org/confluence/display/FLINK/FLIP-33:+Standardize+Connector+Metrics
>>>>>> > > >>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>> On 24 Apr 2019, at 13:28, Stephan Ewen <
>>>>>> sewen@apache.org>
>>>>>> > > >> wrote:
>>>>>> > > >>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>> I think this sounds reasonable.
>>>>>> > > >>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>> Let's keep the "reconfiguration without stopping
>>>>>> the job"
>>>>>> > out
>>>>>> > > >> of
>>>>>> > > >>>>>>> this,
>>>>>> > > >>>>>>>>>>>>> because that would be a super big effort and if we
>>>>>> approach
>>>>>> > > >> that,
>>>>>> > > >>>>>>> then
>>>>>> > > >>>>>>>>>>>> in
>>>>>> > > >>>>>>>>>>>>> more generic way rather than specific to connector
>>>>>> metrics.
>>>>>> > > >>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>> I would suggest to look at the following things
>>>>>> before
>>>>>> > > starting
>>>>>> > > >>>>> with
>>>>>> > > >>>>>>>>> any
>>>>>> > > >>>>>>>>>>>>> implementation work:
>>>>>> > > >>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>> - Try and find a committer to support this,
>>>>>> otherwise it
>>>>>> > will
>>>>>> > > >> be
>>>>>> > > >>>>>>> hard
>>>>>> > > >>>>>>>>>>>> to
>>>>>> > > >>>>>>>>>>>>> make progress
>>>>>> > > >>>>>>>>>>>>> - Start with defining a smaller set of "core
>>>>>> metrics" and
>>>>>> > > >> extend
>>>>>> > > >>>>> the
>>>>>> > > >>>>>>>>>>>> set
>>>>>> > > >>>>>>>>>>>>> later. I think that is easier than now blocking on
>>>>>> reaching
>>>>>> > > >>>>>>> consensus
>>>>>> > > >>>>>>>>>>>> on a
>>>>>> > > >>>>>>>>>>>>> large group of metrics.
>>>>>> > > >>>>>>>>>>>>> - Find a solution to the problem Chesnay mentioned,
>>>>>> that
>>>>>> > the
>>>>>> > > >>>>>>> "records
>>>>>> > > >>>>>>>>>>>> in"
>>>>>> > > >>>>>>>>>>>>> metric is somehow overloaded and exists already in
>>>>>> the IO
>>>>>> > > >> Metric
>>>>>> > > >>>>>>>>> group.
>>>>>> > > >>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>> On Mon, Mar 25, 2019 at 7:16 AM Becket Qin <
>>>>>> > > >> becket.qin@gmail.com
>>>>>> > > >>>>>>
>>>>>> > > >>>>>>>>>>>> wrote:
>>>>>> > > >>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>> Hi Stephan,
>>>>>> > > >>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>> Thanks a lot for the feedback. All makes sense.
>>>>>> > > >>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>> It is a good suggestion to simply have an
>>>>>> > onRecord(numBytes,
>>>>>> > > >>>>>>>>> eventTime)
>>>>>> > > >>>>>>>>>>>>>> method for connector writers. It should meet most
>>>>>> of the
>>>>>> > > >>>>>>>>> requirements,
>>>>>> > > >>>>>>>>>>>>>> individual
>>>>>> > > >>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>> The configurable metrics feature is something
>>>>>> really
>>>>>> > useful,
>>>>>> > > >>>>>>>>>>>> especially if
>>>>>> > > >>>>>>>>>>>>>> we can somehow make it dynamically configurable
>>>>>> without
>>>>>> > > >> stopping
>>>>>> > > >>>>>>> the
>>>>>> > > >>>>>>>>>>>> jobs.
>>>>>> > > >>>>>>>>>>>>>> It might be better to make it a separate discussion
>>>>>> > because
>>>>>> > > it
>>>>>> > > >>>>> is a
>>>>>> > > >>>>>>>>>>>> more
>>>>>> > > >>>>>>>>>>>>>> generic feature instead of only for connectors.
>>>>>> > > >>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>> So in order to make some progress, in this FLIP we
>>>>>> can
>>>>>> > limit
>>>>>> > > >> the
>>>>>> > > >>>>>>>>>>>> discussion
>>>>>> > > >>>>>>>>>>>>>> scope to the connector related items:
>>>>>> > > >>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>> - the standard connector metric names and types.
>>>>>> > > >>>>>>>>>>>>>> - the abstract ConnectorMetricHandler interface
>>>>>> > > >>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>> I'll start a separate thread to discuss other
>>>>>> general
>>>>>> > metric
>>>>>> > > >>>>>>> related
>>>>>> > > >>>>>>>>>>>>>> enhancement items including:
>>>>>> > > >>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>> - optional metrics
>>>>>> > > >>>>>>>>>>>>>> - dynamic metric configuration
>>>>>> > > >>>>>>>>>>>>>> - potential combination with rate limiter
>>>>>> > > >>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>> Does this plan sound reasonable?
>>>>>> > > >>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>> Thanks,
>>>>>> > > >>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>> Jiangjie (Becket) Qin
>>>>>> > > >>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>> On Sat, Mar 23, 2019 at 5:53 AM Stephan Ewen <
>>>>>> > > >> sewen@apache.org>
>>>>>> > > >>>>>>>>> wrote:
>>>>>> > > >>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>> Ignoring for a moment implementation details, this
>>>>>> > > connector
>>>>>> > > >>>>>>> metrics
>>>>>> > > >>>>>>>>>>>> work
>>>>>> > > >>>>>>>>>>>>>>> is a really good thing to do, in my opinion
>>>>>> > > >>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>> The questions "oh, my job seems to be doing
>>>>>> nothing, I am
>>>>>> > > >>>>> looking
>>>>>> > > >>>>>>> at
>>>>>> > > >>>>>>>>>>>> the
>>>>>> > > >>>>>>>>>>>>>> UI
>>>>>> > > >>>>>>>>>>>>>>> and the 'records in' value is still zero" is in
>>>>>> the top
>>>>>> > > three
>>>>>> > > >>>>>>>>> support
>>>>>> > > >>>>>>>>>>>>>>> questions I have been asked personally.
>>>>>> > > >>>>>>>>>>>>>>> Introspection into "how far is the consumer
>>>>>> lagging
>>>>>> > behind"
>>>>>> > > >>>>> (event
>>>>>> > > >>>>>>>>>>>> time
>>>>>> > > >>>>>>>>>>>>>>> fetch latency) came up many times as well.
>>>>>> > > >>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>> So big +1 to solving this problem.
>>>>>> > > >>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>> About the exact design - I would try to go for the
>>>>>> > > following
>>>>>> > > >>>>>>>>>>>> properties:
>>>>>> > > >>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>> - keep complexity of of connectors. Ideally the
>>>>>> metrics
>>>>>> > > >> handler
>>>>>> > > >>>>>>> has
>>>>>> > > >>>>>>>>> a
>>>>>> > > >>>>>>>>>>>>>>> single onRecord(numBytes, eventTime) method or
>>>>>> so, and
>>>>>> > > >>>>> everything
>>>>>> > > >>>>>>>>>>>> else is
>>>>>> > > >>>>>>>>>>>>>>> internal to the handler. That makes it dead
>>>>>> simple for
>>>>>> > the
>>>>>> > > >>>>>>>>> connector.
>>>>>> > > >>>>>>>>>>>> We
>>>>>> > > >>>>>>>>>>>>>>> can also think of an extensive scheme for
>>>>>> connector
>>>>>> > > specific
>>>>>> > > >>>>>>>>> metrics.
>>>>>> > > >>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>> - make it configurable on the job it cluster
>>>>>> level which
>>>>>> > > >>>>> metrics
>>>>>> > > >>>>>>> the
>>>>>> > > >>>>>>>>>>>>>>> handler internally creates when that method is
>>>>>> invoked.
>>>>>> > > >>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>> What do you think?
>>>>>> > > >>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>> Best,
>>>>>> > > >>>>>>>>>>>>>>> Stephan
>>>>>> > > >>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>> On Thu, Mar 21, 2019 at 10:42 AM Chesnay Schepler
>>>>>> <
>>>>>> > > >>>>>>>>> chesnay@apache.org
>>>>>> > > >>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>> wrote:
>>>>>> > > >>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>> As I said before, I believe this to be
>>>>>> over-engineered
>>>>>> > and
>>>>>> > > >>>>> have
>>>>>> > > >>>>>>> no
>>>>>> > > >>>>>>>>>>>>>>>> interest in this implementation.
>>>>>> > > >>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>> There are conceptual issues like defining a
>>>>>> duplicate
>>>>>> > > >>>>>>>>>>>>>> numBytesIn(PerSec)
>>>>>> > > >>>>>>>>>>>>>>>> metric that already exists for each operator.
>>>>>> > > >>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>> On 21.03.2019 06:13, Becket Qin wrote:
>>>>>> > > >>>>>>>>>>>>>>>>> A few updates to the thread. I uploaded a
>>>>>> patch[1] as a
>>>>>> > > >>>>> complete
>>>>>> > > >>>>>>>>>>>>>>>>> example of how users can use the metrics in the
>>>>>> future.
>>>>>> > > >>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>> Some thoughts below after taking a look at the
>>>>>> > > >>>>>>> AbstractMetricGroup
>>>>>> > > >>>>>>>>>>>>>> and
>>>>>> > > >>>>>>>>>>>>>>>>> its subclasses.
>>>>>> > > >>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>> This patch intends to provide convenience for
>>>>>> Flink
>>>>>> > > >> connector
>>>>>> > > >>>>>>>>>>>>>>>>> implementations to follow metrics standards
>>>>>> proposed in
>>>>>> > > >>>>> FLIP-33.
>>>>>> > > >>>>>>>>> It
>>>>>> > > >>>>>>>>>>>>>>>>> also try to enhance the metric management in
>>>>>> general
>>>>>> > way
>>>>>> > > to
>>>>>> > > >>>>> help
>>>>>> > > >>>>>>>>>>>>>> users
>>>>>> > > >>>>>>>>>>>>>>>>> with:
>>>>>> > > >>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>> 1. metric definition
>>>>>> > > >>>>>>>>>>>>>>>>> 2. metric dependencies check
>>>>>> > > >>>>>>>>>>>>>>>>> 3. metric validation
>>>>>> > > >>>>>>>>>>>>>>>>> 4. metric control (turn on / off particular
>>>>>> metrics)
>>>>>> > > >>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>> This patch wraps |MetricGroup| to extend the
>>>>>> > > functionality
>>>>>> > > >> of
>>>>>> > > >>>>>>>>>>>>>>>>> |AbstractMetricGroup| and its subclasses. The
>>>>>> > > >>>>>>>>>>>>>>>>> |AbstractMetricGroup| mainly focus on the
>>>>>> metric group
>>>>>> > > >>>>>>> hierarchy,
>>>>>> > > >>>>>>>>>>>> but
>>>>>> > > >>>>>>>>>>>>>>>>> does not really manage the metrics other than
>>>>>> keeping
>>>>>> > > them
>>>>>> > > >>>>> in a
>>>>>> > > >>>>>>>>> Map.
>>>>>> > > >>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>> Ideally we should only have one entry point for
>>>>>> the
>>>>>> > > >> metrics.
>>>>>> > > >>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>> Right now the entry point is
>>>>>> |AbstractMetricGroup|.
>>>>>> > > >> However,
>>>>>> > > >>>>>>>>> besides
>>>>>> > > >>>>>>>>>>>>>>>>> the missing functionality mentioned above,
>>>>>> > > >>>>> |AbstractMetricGroup|
>>>>>> > > >>>>>>>>>>>>>> seems
>>>>>> > > >>>>>>>>>>>>>>>>> deeply rooted in Flink runtime. We could
>>>>>> extract it out
>>>>>> > > to
>>>>>> > > >>>>>>>>>>>>>>>>> flink-metrics in order to use it for generic
>>>>>> purpose.
>>>>>> > > There
>>>>>> > > >>>>> will
>>>>>> > > >>>>>>>>> be
>>>>>> > > >>>>>>>>>>>>>>>>> some work, though.
>>>>>> > > >>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>> Another approach is to make |AbstractMetrics|
>>>>>> in this
>>>>>> > > patch
>>>>>> > > >>>>> as
>>>>>> > > >>>>>>> the
>>>>>> > > >>>>>>>>>>>>>>>>> metric entry point. It wraps metric group and
>>>>>> provides
>>>>>> > > the
>>>>>> > > >>>>>>> missing
>>>>>> > > >>>>>>>>>>>>>>>>> functionalities. Then we can roll out this
>>>>>> pattern to
>>>>>> > > >> runtime
>>>>>> > > >>>>>>>>>>>>>>>>> components gradually as well.
>>>>>> > > >>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>> My first thought is that the latter approach
>>>>>> gives a
>>>>>> > more
>>>>>> > > >>>>> smooth
>>>>>> > > >>>>>>>>>>>>>>>>> migration. But I am also OK with doing a
>>>>>> refactoring on
>>>>>> > > the
>>>>>> > > >>>>>>>>>>>>>>>>> |AbstractMetricGroup| family.
>>>>>> > > >>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>> Thanks,
>>>>>> > > >>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>> Jiangjie (Becket) Qin
>>>>>> > > >>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>> [1] https://github.com/becketqin/flink/pull/1
>>>>>> > > >>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>> On Mon, Feb 25, 2019 at 2:32 PM Becket Qin <
>>>>>> > > >>>>>>> becket.qin@gmail.com
>>>>>> > > >>>>>>>>>>>>>>>>> <ma...@gmail.com>> wrote:
>>>>>> > > >>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>> Hi Chesnay,
>>>>>> > > >>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>> It might be easier to discuss some
>>>>>> implementation
>>>>>> > details
>>>>>> > > >> in
>>>>>> > > >>>>>>> the
>>>>>> > > >>>>>>>>>>>>>>>>> PR review instead of in the FLIP discussion
>>>>>> thread. I
>>>>>> > > have
>>>>>> > > >> a
>>>>>> > > >>>>>>>>>>>>>> patch
>>>>>> > > >>>>>>>>>>>>>>>>> for Kafka connectors ready but haven't
>>>>>> submitted the PR
>>>>>> > > >> yet.
>>>>>> > > >>>>>>>>>>>>>>>>> Hopefully that will help explain a bit more.
>>>>>> > > >>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>> ** Re: metric type binding
>>>>>> > > >>>>>>>>>>>>>>>>> This is a valid point that worths discussing.
>>>>>> If I
>>>>>> > > >> understand
>>>>>> > > >>>>>>>>>>>>>>>>> correctly, there are two points:
>>>>>> > > >>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>> 1. Metric type / interface does not matter as
>>>>>> long as
>>>>>> > the
>>>>>> > > >>>>>>> metric
>>>>>> > > >>>>>>>>>>>>>>>>> semantic is clearly defined.
>>>>>> > > >>>>>>>>>>>>>>>>> Conceptually speaking, I agree that as long as
>>>>>> the
>>>>>> > metric
>>>>>> > > >>>>>>>>>>>>>> semantic
>>>>>> > > >>>>>>>>>>>>>>>>> is defined, metric type does not matter. To some
>>>>>> > extent,
>>>>>> > > >>>>> Gauge
>>>>>> > > >>>>>>> /
>>>>>> > > >>>>>>>>>>>>>>>>> Counter / Meter / Histogram themselves can be
>>>>>> think of
>>>>>> > as
>>>>>> > > >>>>> some
>>>>>> > > >>>>>>>>>>>>>>>>> well-recognized semantics, if you wish. In
>>>>>> Flink, these
>>>>>> > > >>>>> metric
>>>>>> > > >>>>>>>>>>>>>>>>> semantics have their associated interface
>>>>>> classes. In
>>>>>> > > >>>>> practice,
>>>>>> > > >>>>>>>>>>>>>>>>> such semantic to interface binding seems
>>>>>> necessary for
>>>>>> > > >>>>>>> different
>>>>>> > > >>>>>>>>>>>>>>>>> components to communicate. Simply standardize
>>>>>> the
>>>>>> > > semantic
>>>>>> > > >>>>> of
>>>>>> > > >>>>>>>>>>>>>> the
>>>>>> > > >>>>>>>>>>>>>>>>> connector metrics seems not sufficient for
>>>>>> people to
>>>>>> > > build
>>>>>> > > >>>>>>>>>>>>>>>>> ecosystem on top of. At the end of the day, we
>>>>>> still
>>>>>> > need
>>>>>> > > >> to
>>>>>> > > >>>>>>>>> have
>>>>>> > > >>>>>>>>>>>>>>>>> some embodiment of the metric semantics that
>>>>>> people can
>>>>>> > > >>>>> program
>>>>>> > > >>>>>>>>>>>>>>>>> against.
>>>>>> > > >>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>> 2. Sometimes the same metric semantic can be
>>>>>> exposed
>>>>>> > > using
>>>>>> > > >>>>>>>>>>>>>>>>> different metric types / interfaces.
>>>>>> > > >>>>>>>>>>>>>>>>> This is a good point. Counter and
>>>>>> Gauge-as-a-Counter
>>>>>> > are
>>>>>> > > >>>>> pretty
>>>>>> > > >>>>>>>>>>>>>>>>> much interchangeable. This is more of a
>>>>>> trade-off
>>>>>> > between
>>>>>> > > >> the
>>>>>> > > >>>>>>>>>>>>>> user
>>>>>> > > >>>>>>>>>>>>>>>>> experience of metric producers and consumers.
>>>>>> The
>>>>>> > metric
>>>>>> > > >>>>>>>>>>>>>> producers
>>>>>> > > >>>>>>>>>>>>>>>>> want to use Counter or Gauge depending on
>>>>>> whether the
>>>>>> > > >> counter
>>>>>> > > >>>>>>> is
>>>>>> > > >>>>>>>>>>>>>>>>> already tracked in code, while ideally the
>>>>>> metric
>>>>>> > > consumers
>>>>>> > > >>>>>>> only
>>>>>> > > >>>>>>>>>>>>>>>>> want to see a single metric type for each
>>>>>> metric. I am
>>>>>> > > >>>>> leaning
>>>>>> > > >>>>>>>>>>>>>>>>> towards to make the metric producers happy,
>>>>>> i.e. allow
>>>>>> > > >> Gauge
>>>>>> > > >>>>> /
>>>>>> > > >>>>>>>>>>>>>>>>> Counter metric type, and the the metric
>>>>>> consumers
>>>>>> > handle
>>>>>> > > >> the
>>>>>> > > >>>>>>>>> type
>>>>>> > > >>>>>>>>>>>>>>>>> variation. The reason is that in practice,
>>>>>> there might
>>>>>> > be
>>>>>> > > >>>>> more
>>>>>> > > >>>>>>>>>>>>>>>>> connector implementations than metric reporter
>>>>>> > > >>>>> implementations.
>>>>>> > > >>>>>>>>>>>>>> We
>>>>>> > > >>>>>>>>>>>>>>>>> could also provide some helper method to
>>>>>> facilitate
>>>>>> > > reading
>>>>>> > > >>>>>>> from
>>>>>> > > >>>>>>>>>>>>>>>>> such variable metric type.
>>>>>> > > >>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>> Just some quick replies to the comments around
>>>>>> > > >> implementation
>>>>>> > > >>>>>>>>>>>>>>>> details.
>>>>>> > > >>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>> 4) single place where metrics are registered
>>>>>> except
>>>>>> > > >>>>>>>>>>>>>>>>> connector-specific
>>>>>> > > >>>>>>>>>>>>>>>>> ones (which we can't really avoid).
>>>>>> > > >>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>> Register connector specific ones in a single
>>>>>> place is
>>>>>> > > >>>>> actually
>>>>>> > > >>>>>>>>>>>>>>>>> something that I want to achieve.
>>>>>> > > >>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>> 2) I'm talking about time-series databases
>>>>>> like
>>>>>> > > >>>>> Prometheus.
>>>>>> > > >>>>>>>>>>>>>> We
>>>>>> > > >>>>>>>>>>>>>>>>> would
>>>>>> > > >>>>>>>>>>>>>>>>> only have a gauge metric exposing the last
>>>>>> > > >>>>>>>>> fetchTime/emitTime
>>>>>> > > >>>>>>>>>>>>>>>>> that is
>>>>>> > > >>>>>>>>>>>>>>>>> regularly reported to the backend
>>>>>> (Prometheus),
>>>>>> > where a
>>>>>> > > >>>>>>> user
>>>>>> > > >>>>>>>>>>>>>>>>> could build
>>>>>> > > >>>>>>>>>>>>>>>>> a histogram of his choosing when/if he wants
>>>>>> it.
>>>>>> > > >>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>> Not sure if such downsampling works. As an
>>>>>> example, if
>>>>>> > a
>>>>>> > > >> user
>>>>>> > > >>>>>>>>>>>>>>>>> complains that there are some intermittent
>>>>>> latency
>>>>>> > spikes
>>>>>> > > >>>>>>> (maybe
>>>>>> > > >>>>>>>>>>>>>> a
>>>>>> > > >>>>>>>>>>>>>>>>> few records in 10 seconds) in their processing
>>>>>> system.
>>>>>> > > >>>>> Having a
>>>>>> > > >>>>>>>>>>>>>>>>> Gauge sampling instantaneous latency seems
>>>>>> unlikely
>>>>>> > > useful.
>>>>>> > > >>>>>>>>>>>>>>>>> However by looking at actual 99.9 percentile
>>>>>> latency
>>>>>> > > might
>>>>>> > > >>>>>>> help.
>>>>>> > > >>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>> Thanks,
>>>>>> > > >>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>> Jiangjie (Becket) Qin
>>>>>> > > >>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>> On Fri, Feb 22, 2019 at 9:30 PM Chesnay Schepler
>>>>>> > > >>>>>>>>>>>>>>>>> <chesnay@apache.org <mailto:chesnay@apache.org
>>>>>> >>
>>>>>> > wrote:
>>>>>> > > >>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>> Re: over complication of implementation.
>>>>>> > > >>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>> I think I get understand better know what
>>>>>> you're
>>>>>> > > >> shooting
>>>>>> > > >>>>>>>>>>>>>> for,
>>>>>> > > >>>>>>>>>>>>>>>>> effectively something like the
>>>>>> OperatorIOMetricGroup.
>>>>>> > > >>>>>>>>>>>>>>>>> But still, re-define setupConnectorMetrics()
>>>>>> to
>>>>>> > accept
>>>>>> > > a
>>>>>> > > >>>>>>> set
>>>>>> > > >>>>>>>>>>>>>>>>> of flags
>>>>>> > > >>>>>>>>>>>>>>>>> for counters/meters(ans _possibly_
>>>>>> histograms) along
>>>>>> > > >>>>> with a
>>>>>> > > >>>>>>>>>>>>>>>>> set of
>>>>>> > > >>>>>>>>>>>>>>>>> well-defined Optional<Gauge<?>>, and return
>>>>>> the
>>>>>> > group.
>>>>>> > > >>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>> Solves all issues as far as i can tell:
>>>>>> > > >>>>>>>>>>>>>>>>> 1) no metrics must be created manually (except
>>>>>> > Gauges,
>>>>>> > > >>>>>>> which
>>>>>> > > >>>>>>>>>>>>>>> are
>>>>>> > > >>>>>>>>>>>>>>>>> effectively just Suppliers and you can't get
>>>>>> around
>>>>>> > > >>>>> this),
>>>>>> > > >>>>>>>>>>>>>>>>> 2) additional metrics can be registered on the
>>>>>> > returned
>>>>>> > > >>>>>>>>>>>>>> group,
>>>>>> > > >>>>>>>>>>>>>>>>> 3) see 1),
>>>>>> > > >>>>>>>>>>>>>>>>> 4) single place where metrics are registered
>>>>>> except
>>>>>> > > >>>>>>>>>>>>>>>>> connector-specific
>>>>>> > > >>>>>>>>>>>>>>>>> ones (which we can't really avoid).
>>>>>> > > >>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>> Re: Histogram
>>>>>> > > >>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>> 1) As an example, whether "numRecordsIn" is
>>>>>> exposed
>>>>>> > as
>>>>>> > > a
>>>>>> > > >>>>>>>>>>>>>>>>> Counter or a
>>>>>> > > >>>>>>>>>>>>>>>>> Gauge should be irrelevant. So far we're
>>>>>> using the
>>>>>> > > >> metric
>>>>>> > > >>>>>>>>>>>>>> type
>>>>>> > > >>>>>>>>>>>>>>>>> that is
>>>>>> > > >>>>>>>>>>>>>>>>> the most convenient at exposing a given
>>>>>> value. If
>>>>>> > there
>>>>>> > > >>>>> is
>>>>>> > > >>>>>>>>>>>>>>>>> some backing
>>>>>> > > >>>>>>>>>>>>>>>>> data-structure that we want to expose some
>>>>>> data from
>>>>>> > we
>>>>>> > > >>>>>>>>>>>>>>>>> typically opt
>>>>>> > > >>>>>>>>>>>>>>>>> for a Gauge, as otherwise we're just mucking
>>>>>> around
>>>>>> > > with
>>>>>> > > >>>>>>> the
>>>>>> > > >>>>>>>>>>>>>>>>> Meter/Counter API to get it to match.
>>>>>> Similarly, if
>>>>>> > we
>>>>>> > > >>>>> want
>>>>>> > > >>>>>>>>>>>>>> to
>>>>>> > > >>>>>>>>>>>>>>>>> count
>>>>>> > > >>>>>>>>>>>>>>>>> something but no current count exists we
>>>>>> typically
>>>>>> > > added
>>>>>> > > >>>>> a
>>>>>> > > >>>>>>>>>>>>>>>>> Counter.
>>>>>> > > >>>>>>>>>>>>>>>>> That's why attaching semantics to metric
>>>>>> types makes
>>>>>> > > >>>>> little
>>>>>> > > >>>>>>>>>>>>>>>>> sense (but
>>>>>> > > >>>>>>>>>>>>>>>>> unfortunately several reporters already do
>>>>>> it); for
>>>>>> > > >>>>>>>>>>>>>>>>> counters/meters
>>>>>> > > >>>>>>>>>>>>>>>>> certainly, but the majority of metrics are
>>>>>> gauges.
>>>>>> > > >>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>> 2) I'm talking about time-series databases
>>>>>> like
>>>>>> > > >>>>> Prometheus.
>>>>>> > > >>>>>>>>>>>>>> We
>>>>>> > > >>>>>>>>>>>>>>>>> would
>>>>>> > > >>>>>>>>>>>>>>>>> only have a gauge metric exposing the last
>>>>>> > > >>>>>>>>> fetchTime/emitTime
>>>>>> > > >>>>>>>>>>>>>>>>> that is
>>>>>> > > >>>>>>>>>>>>>>>>> regularly reported to the backend
>>>>>> (Prometheus),
>>>>>> > where a
>>>>>> > > >>>>>>> user
>>>>>> > > >>>>>>>>>>>>>>>>> could build
>>>>>> > > >>>>>>>>>>>>>>>>> a histogram of his choosing when/if he wants
>>>>>> it.
>>>>>> > > >>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>> On 22.02.2019 13:57, Becket Qin wrote:
>>>>>> > > >>>>>>>>>>>>>>>>>> Hi Chesnay,
>>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>>> Thanks for the explanation.
>>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>>> ** Re: FLIP
>>>>>> > > >>>>>>>>>>>>>>>>>> I might have misunderstood this, but it seems
>>>>>> that
>>>>>> > > "major
>>>>>> > > >>>>>>>>>>>>>>>>> changes" are well
>>>>>> > > >>>>>>>>>>>>>>>>>> defined in FLIP. The full contents is
>>>>>> following:
>>>>>> > > >>>>>>>>>>>>>>>>>> What is considered a "major change" that needs
>>>>>> a FLIP?
>>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>>> Any of the following should be considered a
>>>>>> major
>>>>>> > > change:
>>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>>> - Any major new feature, subsystem, or piece of
>>>>>> > > >>>>>>>>>>>>>>>>> functionality
>>>>>> > > >>>>>>>>>>>>>>>>>> - *Any change that impacts the public
>>>>>> interfaces of
>>>>>> > the
>>>>>> > > >>>>>>>>>>>>>>>>> project*
>>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>>> What are the "public interfaces" of the
>>>>>> project?
>>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>>> *All of the following are public interfaces
>>>>>> *that
>>>>>> > people
>>>>>> > > >>>>>>>>>>>>>>>>> build around:
>>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>>> - DataStream and DataSet API, including classes
>>>>>> > related
>>>>>> > > >>>>>>>>>>>>>>>>> to that, such as
>>>>>> > > >>>>>>>>>>>>>>>>>> StreamExecutionEnvironment
>>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>>> - Classes marked with the @Public annotation
>>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>>> - On-disk binary formats, such as
>>>>>> > > >>>>>>>>>>>>>> checkpoints/savepoints
>>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>>> - User-facing scripts/command-line tools, i.e.
>>>>>> > > >>>>>>>>>>>>>>>>> bin/flink, Yarn scripts,
>>>>>> > > >>>>>>>>>>>>>>>>>> Mesos scripts
>>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>>> - Configuration settings
>>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>>> - *Exposed monitoring information*
>>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>>> So any monitoring information change is
>>>>>> considered as
>>>>>> > > >>>>>>>>>>>>>> public
>>>>>> > > >>>>>>>>>>>>>>>>> interface, and
>>>>>> > > >>>>>>>>>>>>>>>>>> any public interface change is considered as a
>>>>>> "major
>>>>>> > > >>>>>>>>>>>>>>> change".
>>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>>> ** Re: over complication of implementation.
>>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>>> Although this is more of implementation
>>>>>> details that
>>>>>> > is
>>>>>> > > >> not
>>>>>> > > >>>>>>>>>>>>>>>>> covered by the
>>>>>> > > >>>>>>>>>>>>>>>>>> FLIP. But it may be worth discussing.
>>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>>> First of all, I completely agree that we
>>>>>> should use
>>>>>> > the
>>>>>> > > >>>>>>>>>>>>>>>>> simplest way to
>>>>>> > > >>>>>>>>>>>>>>>>>> achieve our goal. To me the goal is the
>>>>>> following:
>>>>>> > > >>>>>>>>>>>>>>>>>> 1. Clear connector conventions and interfaces.
>>>>>> > > >>>>>>>>>>>>>>>>>> 2. The easiness of creating a connector.
>>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>>> Both of them are important to the prosperity
>>>>>> of the
>>>>>> > > >>>>>>>>>>>>>>>>> connector ecosystem. So
>>>>>> > > >>>>>>>>>>>>>>>>>> I'd rather abstract as much as possible on our
>>>>>> side to
>>>>>> > > >> make
>>>>>> > > >>>>>>>>>>>>>>>>> the connector
>>>>>> > > >>>>>>>>>>>>>>>>>> developer's work lighter. Given this goal, a
>>>>>> static
>>>>>> > util
>>>>>> > > >>>>>>>>>>>>>>>>> method approach
>>>>>> > > >>>>>>>>>>>>>>>>>> might have a few drawbacks:
>>>>>> > > >>>>>>>>>>>>>>>>>> 1. Users still have to construct the metrics by
>>>>>> > > >> themselves.
>>>>>> > > >>>>>>>>>>>>>>>>> (And note that
>>>>>> > > >>>>>>>>>>>>>>>>>> this might be erroneous by itself. For
>>>>>> example, a
>>>>>> > > customer
>>>>>> > > >>>>>>>>>>>>>>>>> wrapper around
>>>>>> > > >>>>>>>>>>>>>>>>>> dropwizard meter maybe used instead of
>>>>>> MeterView).
>>>>>> > > >>>>>>>>>>>>>>>>>> 2. When connector specific metrics are added,
>>>>>> it is
>>>>>> > > >>>>>>>>>>>>>>>>> difficult to enforce
>>>>>> > > >>>>>>>>>>>>>>>>>> the scope to be the same as standard metrics.
>>>>>> > > >>>>>>>>>>>>>>>>>> 3. It seems that a method proliferation is
>>>>>> inevitable
>>>>>> > if
>>>>>> > > >> we
>>>>>> > > >>>>>>>>>>>>>>>>> want to apply
>>>>>> > > >>>>>>>>>>>>>>>>>> sanity checks. e.g. The metric of numBytesIn
>>>>>> was not
>>>>>> > > >>>>>>>>>>>>>>>>> registered for a meter.
>>>>>> > > >>>>>>>>>>>>>>>>>> 4. Metrics are still defined in random places
>>>>>> and hard
>>>>>> > > to
>>>>>> > > >>>>>>>>>>>>>>>> track.
>>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>>> The current PR I had was inspired by the
>>>>>> Config system
>>>>>> > > in
>>>>>> > > >>>>>>>>>>>>>>>>> Kafka, which I
>>>>>> > > >>>>>>>>>>>>>>>>>> found pretty handy. In fact it is not only
>>>>>> used by
>>>>>> > Kafka
>>>>>> > > >>>>>>>>>>>>>>>>> itself but even
>>>>>> > > >>>>>>>>>>>>>>>>>> some other projects that depend on Kafka. I am
>>>>>> not
>>>>>> > > saying
>>>>>> > > >>>>>>>>>>>>>>>>> this approach is
>>>>>> > > >>>>>>>>>>>>>>>>>> perfect. But I think it worths to save the
>>>>>> work for
>>>>>> > > >>>>>>>>>>>>>>>>> connector writers and
>>>>>> > > >>>>>>>>>>>>>>>>>> encourage more systematic implementation. That
>>>>>> being
>>>>>> > > said,
>>>>>> > > >>>>>>>>>>>>>> I
>>>>>> > > >>>>>>>>>>>>>>>>> am fully open
>>>>>> > > >>>>>>>>>>>>>>>>>> to suggestions.
>>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>>> Re: Histogram
>>>>>> > > >>>>>>>>>>>>>>>>>> I think there are two orthogonal questions
>>>>>> around
>>>>>> > those
>>>>>> > > >>>>>>>>>>>>>>>> metrics:
>>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>>> 1. Regardless of the metric type, by just
>>>>>> looking at
>>>>>> > the
>>>>>> > > >>>>>>>>>>>>>>>>> meaning of a
>>>>>> > > >>>>>>>>>>>>>>>>>> metric, is generic to all connectors? If the
>>>>>> answer is
>>>>>> > > >> yes,
>>>>>> > > >>>>>>>>>>>>>>>>> we should
>>>>>> > > >>>>>>>>>>>>>>>>>> include the metric into the convention. No
>>>>>> matter
>>>>>> > > whether
>>>>>> > > >>>>>>>>>>>>>> we
>>>>>> > > >>>>>>>>>>>>>>>>> include it
>>>>>> > > >>>>>>>>>>>>>>>>>> into the convention or not, some connector
>>>>>> > > implementations
>>>>>> > > >>>>>>>>>>>>>>>>> will emit such
>>>>>> > > >>>>>>>>>>>>>>>>>> metric. It is better to have a convention than
>>>>>> letting
>>>>>> > > >> each
>>>>>> > > >>>>>>>>>>>>>>>>> connector do
>>>>>> > > >>>>>>>>>>>>>>>>>> random things.
>>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>>> 2. If a standard metric is a histogram, what
>>>>>> should we
>>>>>> > > do?
>>>>>> > > >>>>>>>>>>>>>>>>>> I agree that we should make it clear that using
>>>>>> > > histograms
>>>>>> > > >>>>>>>>>>>>>>>>> will have
>>>>>> > > >>>>>>>>>>>>>>>>>> performance risk. But I do see histogram is
>>>>>> useful in
>>>>>> > > some
>>>>>> > > >>>>>>>>>>>>>>>>> fine-granularity
>>>>>> > > >>>>>>>>>>>>>>>>>> debugging where one do not have the luxury to
>>>>>> stop the
>>>>>> > > >>>>>>>>>>>>>>>>> system and inject
>>>>>> > > >>>>>>>>>>>>>>>>>> more inspection code. So the workaround I am
>>>>>> thinking
>>>>>> > is
>>>>>> > > >> to
>>>>>> > > >>>>>>>>>>>>>>>>> provide some
>>>>>> > > >>>>>>>>>>>>>>>>>> implementation suggestions. Assume later on we
>>>>>> have a
>>>>>> > > >>>>>>>>>>>>>>>>> mechanism of
>>>>>> > > >>>>>>>>>>>>>>>>>> selective metrics. In the abstract metrics
>>>>>> class we
>>>>>> > can
>>>>>> > > >>>>>>>>>>>>>>>>> disable those
>>>>>> > > >>>>>>>>>>>>>>>>>> metrics by default individual connector
>>>>>> writers does
>>>>>> > not
>>>>>> > > >>>>>>>>>>>>>>>>> have to do
>>>>>> > > >>>>>>>>>>>>>>>>>> anything (this is another advantage of having
>>>>>> an
>>>>>> > > >>>>>>>>>>>>>>>>> AbstractMetrics instead of
>>>>>> > > >>>>>>>>>>>>>>>>>> static util methods.)
>>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>>> I am not sure I fully understand the histogram
>>>>>> in the
>>>>>> > > >>>>>>>>>>>>>>>>> backend approach. Can
>>>>>> > > >>>>>>>>>>>>>>>>>> you explain a bit more? Do you mean emitting
>>>>>> the raw
>>>>>> > > data,
>>>>>> > > >>>>>>>>>>>>>>>>> e.g. fetchTime
>>>>>> > > >>>>>>>>>>>>>>>>>> and emitTime with each record and let the
>>>>>> histogram
>>>>>> > > >>>>>>>>>>>>>>>>> computation happen in
>>>>>> > > >>>>>>>>>>>>>>>>>> the background? Or let the processing thread
>>>>>> putting
>>>>>> > the
>>>>>> > > >>>>>>>>>>>>>>>>> values into a
>>>>>> > > >>>>>>>>>>>>>>>>>> queue and have a separate thread polling from
>>>>>> the
>>>>>> > queue
>>>>>> > > >> and
>>>>>> > > >>>>>>>>>>>>>>>>> add them into
>>>>>> > > >>>>>>>>>>>>>>>>>> the histogram?
>>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>>> Thanks,
>>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>>> Jiangjie (Becket) Qin
>>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>>> On Fri, Feb 22, 2019 at 4:34 PM Chesnay
>>>>>> Schepler
>>>>>> > > >>>>>>>>>>>>>>>>> <chesnay@apache.org <mailto:
>>>>>> chesnay@apache.org>>
>>>>>> > > wrote:
>>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>>>> Re: Flip
>>>>>> > > >>>>>>>>>>>>>>>>>>> The very first line under both the main
>>>>>> header and
>>>>>> > > >> Purpose
>>>>>> > > >>>>>>>>>>>>>>>>> section
>>>>>> > > >>>>>>>>>>>>>>>>>>> describe Flips as "major changes", which this
>>>>>> isn't.
>>>>>> > > >>>>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>>>> Re: complication
>>>>>> > > >>>>>>>>>>>>>>>>>>> I'm not arguing against standardization, but
>>>>>> again an
>>>>>> > > >>>>>>>>>>>>>>>>> over-complicated
>>>>>> > > >>>>>>>>>>>>>>>>>>> implementation when a static utility method
>>>>>> would be
>>>>>> > > >>>>>>>>>>>>>>>>> sufficient.
>>>>>> > > >>>>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>>>> public static void setupConnectorMetrics(
>>>>>> > > >>>>>>>>>>>>>>>>>>> MetricGroup operatorMetricGroup,
>>>>>> > > >>>>>>>>>>>>>>>>>>> String connectorName,
>>>>>> > > >>>>>>>>>>>>>>>>>>> Optional<Gauge<Long>> numRecordsIn,
>>>>>> > > >>>>>>>>>>>>>>>>>>> ...)
>>>>>> > > >>>>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>>>> This gives you all you need:
>>>>>> > > >>>>>>>>>>>>>>>>>>> * a well-defined set of metrics for a
>>>>>> connector to
>>>>>> > > opt-in
>>>>>> > > >>>>>>>>>>>>>>>>>>> * standardized naming schemes for scope and
>>>>>> > individual
>>>>>> > > >>>>>>>>>>>>>>> metrics
>>>>>> > > >>>>>>>>>>>>>>>>>>> * standardize metric types (although
>>>>>> personally I'm
>>>>>> > not
>>>>>> > > >>>>>>>>>>>>>>>>> interested in that
>>>>>> > > >>>>>>>>>>>>>>>>>>> since metric types should be considered
>>>>>> syntactic
>>>>>> > > sugar)
>>>>>> > > >>>>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>>>> Re: Configurable Histogram
>>>>>> > > >>>>>>>>>>>>>>>>>>> If anything they _must_ be turned off by
>>>>>> default, but
>>>>>> > > the
>>>>>> > > >>>>>>>>>>>>>>>>> metric system is
>>>>>> > > >>>>>>>>>>>>>>>>>>> already exposing so many options that I'm not
>>>>>> too
>>>>>> > keen
>>>>>> > > on
>>>>>> > > >>>>>>>>>>>>>>>>> adding even more.
>>>>>> > > >>>>>>>>>>>>>>>>>>> You have also only addressed my first argument
>>>>>> > against
>>>>>> > > >>>>>>>>>>>>>>>>> histograms
>>>>>> > > >>>>>>>>>>>>>>>>>>> (performance), the second one still stands
>>>>>> (calculate
>>>>>> > > >>>>>>>>>>>>>>>>> histogram in metric
>>>>>> > > >>>>>>>>>>>>>>>>>>> backends instead).
>>>>>> > > >>>>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>>>> On 21.02.2019 16:27, Becket Qin wrote:
>>>>>> > > >>>>>>>>>>>>>>>>>>>> Hi Chesnay,
>>>>>> > > >>>>>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>>>>> Thanks for the comments. I think this is
>>>>>> worthy of a
>>>>>> > > >> FLIP
>>>>>> > > >>>>>>>>>>>>>>>>> because it is
>>>>>> > > >>>>>>>>>>>>>>>>>>>> public API. According to the FLIP
>>>>>> description a FlIP
>>>>>> > > is
>>>>>> > > >>>>>>>>>>>>>>>>> required in case
>>>>>> > > >>>>>>>>>>>>>>>>>>> of:
>>>>>> > > >>>>>>>>>>>>>>>>>>>> - Any change that impacts the public
>>>>>> interfaces of
>>>>>> > > >>>>>>>>>>>>>>>>> the project
>>>>>> > > >>>>>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>>>>> and the following entry is found in the
>>>>>> definition
>>>>>> > of
>>>>>> > > >>>>>>>>>>>>>>>>> "public interface".
>>>>>> > > >>>>>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>>>>> - Exposed monitoring information
>>>>>> > > >>>>>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>>>>> Metrics are critical to any production
>>>>>> system. So a
>>>>>> > > >> clear
>>>>>> > > >>>>>>>>>>>>>>>>> metric
>>>>>> > > >>>>>>>>>>>>>>>>>>> definition
>>>>>> > > >>>>>>>>>>>>>>>>>>>> is important for any serious users. For an
>>>>>> > > organization
>>>>>> > > >>>>>>>>>>>>>>>>> with large Flink
>>>>>> > > >>>>>>>>>>>>>>>>>>>> installation, change in metrics means great
>>>>>> amount
>>>>>> > of
>>>>>> > > >>>>>>>>>>>>>>>>> work. So such
>>>>>> > > >>>>>>>>>>>>>>>>>>> changes
>>>>>> > > >>>>>>>>>>>>>>>>>>>> do need to be fully discussed and documented.
>>>>>> > > >>>>>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>>>>> ** Re: Histogram.
>>>>>> > > >>>>>>>>>>>>>>>>>>>> We can discuss whether there is a better way
>>>>>> to
>>>>>> > expose
>>>>>> > > >>>>>>>>>>>>>>>>> metrics that are
>>>>>> > > >>>>>>>>>>>>>>>>>>>> suitable for histograms. My micro-benchmark
>>>>>> on
>>>>>> > various
>>>>>> > > >>>>>>>>>>>>>>>>> histogram
>>>>>> > > >>>>>>>>>>>>>>>>>>>> implementations also indicates that they are
>>>>>> > > >>>>>>>>>>>>>> significantly
>>>>>> > > >>>>>>>>>>>>>>>>> slower than
>>>>>> > > >>>>>>>>>>>>>>>>>>>> other metric types. But I don't think that
>>>>>> means
>>>>>> > never
>>>>>> > > >>>>>>>>>>>>>> use
>>>>>> > > >>>>>>>>>>>>>>>>> histogram, but
>>>>>> > > >>>>>>>>>>>>>>>>>>>> means use it with caution. For example, we
>>>>>> can
>>>>>> > suggest
>>>>>> > > >>>>>>>>>>>>>> the
>>>>>> > > >>>>>>>>>>>>>>>>>>> implementations
>>>>>> > > >>>>>>>>>>>>>>>>>>>> to turn them off by default and only turn it
>>>>>> on for
>>>>>> > a
>>>>>> > > >>>>>>>>>>>>>>>>> small amount of
>>>>>> > > >>>>>>>>>>>>>>>>>>> time
>>>>>> > > >>>>>>>>>>>>>>>>>>>> when performing some micro-debugging.
>>>>>> > > >>>>>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>>>>> ** Re: complication:
>>>>>> > > >>>>>>>>>>>>>>>>>>>> Connector conventions are essential for Flink
>>>>>> > > ecosystem.
>>>>>> > > >>>>>>>>>>>>>>>>> Flink connectors
>>>>>> > > >>>>>>>>>>>>>>>>>>>> pool is probably the most important part of
>>>>>> Flink,
>>>>>> > > just
>>>>>> > > >>>>>>>>>>>>>>>>> like any other
>>>>>> > > >>>>>>>>>>>>>>>>>>> data
>>>>>> > > >>>>>>>>>>>>>>>>>>>> system. Clear conventions of connectors will
>>>>>> help
>>>>>> > > build
>>>>>> > > >>>>>>>>>>>>>>>>> Flink ecosystem
>>>>>> > > >>>>>>>>>>>>>>>>>>> in
>>>>>> > > >>>>>>>>>>>>>>>>>>>> a more organic way.
>>>>>> > > >>>>>>>>>>>>>>>>>>>> Take the metrics convention as an example,
>>>>>> imagine
>>>>>> > > >>>>>>>>>>>>>> someone
>>>>>> > > >>>>>>>>>>>>>>>>> has developed
>>>>>> > > >>>>>>>>>>>>>>>>>>> a
>>>>>> > > >>>>>>>>>>>>>>>>>>>> Flink connector for System foo, and another
>>>>>> > developer
>>>>>> > > >> may
>>>>>> > > >>>>>>>>>>>>>>>>> have developed
>>>>>> > > >>>>>>>>>>>>>>>>>>> a
>>>>>> > > >>>>>>>>>>>>>>>>>>>> monitoring and diagnostic framework for
>>>>>> Flink which
>>>>>> > > >>>>>>>>>>>>>>>>> analyzes the Flink
>>>>>> > > >>>>>>>>>>>>>>>>>>> job
>>>>>> > > >>>>>>>>>>>>>>>>>>>> performance based on metrics. With a clear
>>>>>> metric
>>>>>> > > >>>>>>>>>>>>>>>>> convention, those two
>>>>>> > > >>>>>>>>>>>>>>>>>>>> projects could be developed independently.
>>>>>> Once
>>>>>> > users
>>>>>> > > >> put
>>>>>> > > >>>>>>>>>>>>>>>>> them together,
>>>>>> > > >>>>>>>>>>>>>>>>>>>> it would work without additional
>>>>>> modifications. This
>>>>>> > > >>>>>>>>>>>>>>>>> cannot be easily
>>>>>> > > >>>>>>>>>>>>>>>>>>>> achieved by just defining a few constants.
>>>>>> > > >>>>>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>>>>> ** Re: selective metrics:
>>>>>> > > >>>>>>>>>>>>>>>>>>>> Sure, we can discuss that in a separate
>>>>>> thread.
>>>>>> > > >>>>>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>>>>> @Dawid
>>>>>> > > >>>>>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>>>>> ** Re: latency / fetchedLatency
>>>>>> > > >>>>>>>>>>>>>>>>>>>> The primary purpose of establish such a
>>>>>> convention
>>>>>> > is
>>>>>> > > to
>>>>>> > > >>>>>>>>>>>>>>>>> help developers
>>>>>> > > >>>>>>>>>>>>>>>>>>>> write connectors in a more compatible way.
>>>>>> The
>>>>>> > > >> convention
>>>>>> > > >>>>>>>>>>>>>>>>> is supposed to
>>>>>> > > >>>>>>>>>>>>>>>>>>> be
>>>>>> > > >>>>>>>>>>>>>>>>>>>> defined more proactively. So when look at the
>>>>>> > > >> convention,
>>>>>> > > >>>>>>>>>>>>>>>>> it seems more
>>>>>> > > >>>>>>>>>>>>>>>>>>>> important to see if the concept is
>>>>>> applicable to
>>>>>> > > >>>>>>>>>>>>>>>>> connectors in general.
>>>>>> > > >>>>>>>>>>>>>>>>>>> It
>>>>>> > > >>>>>>>>>>>>>>>>>>>> might be true so far only Kafka connector
>>>>>> reports
>>>>>> > > >>>>>>>>>>>>>> latency.
>>>>>> > > >>>>>>>>>>>>>>>>> But there
>>>>>> > > >>>>>>>>>>>>>>>>>>> might
>>>>>> > > >>>>>>>>>>>>>>>>>>>> be hundreds of other connector
>>>>>> implementations in
>>>>>> > the
>>>>>> > > >>>>>>>>>>>>>>>>> Flink ecosystem,
>>>>>> > > >>>>>>>>>>>>>>>>>>>> though not in the Flink repo, and some of
>>>>>> them also
>>>>>> > > >> emits
>>>>>> > > >>>>>>>>>>>>>>>>> latency. I
>>>>>> > > >>>>>>>>>>>>>>>>>>> think
>>>>>> > > >>>>>>>>>>>>>>>>>>>> a lot of other sources actually also has an
>>>>>> append
>>>>>> > > >>>>>>>>>>>>>>>>> timestamp. e.g.
>>>>>> > > >>>>>>>>>>>>>>>>>>> database
>>>>>> > > >>>>>>>>>>>>>>>>>>>> bin logs and some K-V stores. So I wouldn't
>>>>>> be
>>>>>> > > surprised
>>>>>> > > >>>>>>>>>>>>>>>>> if some database
>>>>>> > > >>>>>>>>>>>>>>>>>>>> connector can also emit latency metrics.
>>>>>> > > >>>>>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>>>>> Thanks,
>>>>>> > > >>>>>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>>>>> Jiangjie (Becket) Qin
>>>>>> > > >>>>>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>>>>> On Thu, Feb 21, 2019 at 10:14 PM Chesnay
>>>>>> Schepler
>>>>>> > > >>>>>>>>>>>>>>>>> <chesnay@apache.org <mailto:
>>>>>> chesnay@apache.org>>
>>>>>> > > >>>>>>>>>>>>>>>>>>>> wrote:
>>>>>> > > >>>>>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>>>>>> Regarding 2) It doesn't make sense to
>>>>>> investigate
>>>>>> > > this
>>>>>> > > >>>>>>>>>>>>>> as
>>>>>> > > >>>>>>>>>>>>>>>>> part of this
>>>>>> > > >>>>>>>>>>>>>>>>>>>>> FLIP. This is something that could be of
>>>>>> interest
>>>>>> > for
>>>>>> > > >>>>>>>>>>>>>> the
>>>>>> > > >>>>>>>>>>>>>>>>> entire metric
>>>>>> > > >>>>>>>>>>>>>>>>>>>>> system, and should be designed for as such.
>>>>>> > > >>>>>>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>>>>>> Regarding the proposal as a whole:
>>>>>> > > >>>>>>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>>>>>> Histogram metrics shall not be added to the
>>>>>> core of
>>>>>> > > >>>>>>>>>>>>>>>>> Flink. They are
>>>>>> > > >>>>>>>>>>>>>>>>>>>>> significantly more expensive than other
>>>>>> metrics,
>>>>>> > and
>>>>>> > > >>>>>>>>>>>>>>>>> calculating
>>>>>> > > >>>>>>>>>>>>>>>>>>>>> histograms in the application is regarded
>>>>>> as an
>>>>>> > > >>>>>>>>>>>>>>>>> anti-pattern by several
>>>>>> > > >>>>>>>>>>>>>>>>>>>>> metric backends, who instead recommend to
>>>>>> expose
>>>>>> > the
>>>>>> > > >> raw
>>>>>> > > >>>>>>>>>>>>>>>>> data and
>>>>>> > > >>>>>>>>>>>>>>>>>>>>> calculate the histogram in the backend.
>>>>>> > > >>>>>>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>>>>>> Second, this seems overly complicated.
>>>>>> Given that
>>>>>> > we
>>>>>> > > >>>>>>>>>>>>>>>>> already established
>>>>>> > > >>>>>>>>>>>>>>>>>>>>> that not all connectors will export all
>>>>>> metrics we
>>>>>> > > are
>>>>>> > > >>>>>>>>>>>>>>>>> effectively
>>>>>> > > >>>>>>>>>>>>>>>>>>>>> reducing this down to a consistent naming
>>>>>> scheme.
>>>>>> > We
>>>>>> > > >>>>>>>>>>>>>>>>> don't need anything
>>>>>> > > >>>>>>>>>>>>>>>>>>>>> sophisticated for that; basically just a few
>>>>>> > > constants
>>>>>> > > >>>>>>>>>>>>>>>>> that all
>>>>>> > > >>>>>>>>>>>>>>>>>>>>> connectors use.
>>>>>> > > >>>>>>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>>>>>> I'm not convinced that this is worthy of a
>>>>>> FLIP.
>>>>>> > > >>>>>>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>>>>>> On 21.02.2019 14:26, Dawid Wysakowicz wrote:
>>>>>> > > >>>>>>>>>>>>>>>>>>>>>> Hi,
>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>>>>>>> Ad 1. In general I undestand and I agree.
>>>>>> But
>>>>>> > those
>>>>>> > > >>>>>>>>>>>>>>>>> particular metrics
>>>>>> > > >>>>>>>>>>>>>>>>>>>>>> (latency, fetchLatency), right now would
>>>>>> only be
>>>>>> > > >>>>>>>>>>>>>>>>> reported if user uses
>>>>>> > > >>>>>>>>>>>>>>>>>>>>>> KafkaConsumer with internal
>>>>>> timestampAssigner with
>>>>>> > > >>>>>>>>>>>>>>>>> StreamCharacteristic
>>>>>> > > >>>>>>>>>>>>>>>>>>>>>> set to EventTime, right? That sounds like
>>>>>> a very
>>>>>> > > >>>>>>>>>>>>>>>>> specific case. I am
>>>>>> > > >>>>>>>>>>>>>>>>>>> not
>>>>>> > > >>>>>>>>>>>>>>>>>>>>>> sure if we should introduce a generic
>>>>>> metric that
>>>>>> > > will
>>>>>> > > >>>>>>>>>>>>>> be
>>>>>> > > >>>>>>>>>>>>>>>>>>>>>> disabled/absent for most of
>>>>>> implementations.
>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>>>>>>> Ad.2 That sounds like an orthogonal issue,
>>>>>> that
>>>>>> > > might
>>>>>> > > >>>>>>>>>>>>>>>>> make sense to
>>>>>> > > >>>>>>>>>>>>>>>>>>>>>> investigate in the future.
>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>>>>>>> Best,
>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>>>>>>> Dawid
>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>>>>>>> On 21/02/2019 13:20, Becket Qin wrote:
>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>> Hi Dawid,
>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>> Thanks for the feedback. That makes sense
>>>>>> to me.
>>>>>> > > >> There
>>>>>> > > >>>>>>>>>>>>>>>>> are two cases
>>>>>> > > >>>>>>>>>>>>>>>>>>> to
>>>>>> > > >>>>>>>>>>>>>>>>>>>>> be
>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>> addressed.
>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>> 1. The metrics are supposed to be a
>>>>>> guidance. It
>>>>>> > is
>>>>>> > > >>>>>>>>>>>>>>>>> likely that a
>>>>>> > > >>>>>>>>>>>>>>>>>>>>> connector
>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>> only supports some but not all of the
>>>>>> metrics. In
>>>>>> > > >> that
>>>>>> > > >>>>>>>>>>>>>>>>> case, each
>>>>>> > > >>>>>>>>>>>>>>>>>>>>> connector
>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>> implementation should have the freedom to
>>>>>> decide
>>>>>> > > >> which
>>>>>> > > >>>>>>>>>>>>>>>>> metrics are
>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>> reported. For the metrics that are
>>>>>> supported, the
>>>>>> > > >>>>>>>>>>>>>>>>> guidance should be
>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>> followed.
>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>> 2. Sometimes users may want to disable
>>>>>> certain
>>>>>> > > >> metrics
>>>>>> > > >>>>>>>>>>>>>>>>> for some reason
>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>> (e.g. performance / reprocessing of
>>>>>> data). A
>>>>>> > > generic
>>>>>> > > >>>>>>>>>>>>>>>>> mechanism should
>>>>>> > > >>>>>>>>>>>>>>>>>>> be
>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>> provided to allow user choose which
>>>>>> metrics are
>>>>>> > > >>>>>>>>>>>>>>>>> reported. This
>>>>>> > > >>>>>>>>>>>>>>>>>>> mechanism
>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>> should also be honored by the connector
>>>>>> > > >>>>>>>>>>>>>> implementations.
>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>> Does this sound reasonable to you?
>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>> Thanks,
>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>> Jiangjie (Becket) Qin
>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>> On Thu, Feb 21, 2019 at 4:22 PM Dawid
>>>>>> Wysakowicz
>>>>>> > <
>>>>>> > > >>>>>>>>>>>>>>>>>>>>> dwysakowicz@apache.org <mailto:
>>>>>> > > dwysakowicz@apache.org
>>>>>> > > >>>>
>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>> wrote:
>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> Hi,
>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> Generally I like the idea of having a
>>>>>> unified,
>>>>>> > > >>>>>>>>>>>>>>>>> standard set of
>>>>>> > > >>>>>>>>>>>>>>>>>>> metrics
>>>>>> > > >>>>>>>>>>>>>>>>>>>>> for
>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> all connectors. I have some slight
>>>>>> concerns
>>>>>> > about
>>>>>> > > >>>>>>>>>>>>>>>>> fetchLatency and
>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> latency though. They are computed based
>>>>>> on
>>>>>> > > EventTime
>>>>>> > > >>>>>>>>>>>>>>>>> which is not a
>>>>>> > > >>>>>>>>>>>>>>>>>>>>> purely
>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> technical feature. It depends often on
>>>>>> some
>>>>>> > > business
>>>>>> > > >>>>>>>>>>>>>>>>> logic, might be
>>>>>> > > >>>>>>>>>>>>>>>>>>>>> absent
>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> or defined after source. Those metrics
>>>>>> could
>>>>>> > also
>>>>>> > > >>>>>>>>>>>>>>>>> behave in a weird
>>>>>> > > >>>>>>>>>>>>>>>>>>>>> way in
>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> case of replaying backlog. Therefore I
>>>>>> am not
>>>>>> > sure
>>>>>> > > >> if
>>>>>> > > >>>>>>>>>>>>>>>>> we should
>>>>>> > > >>>>>>>>>>>>>>>>>>> include
>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> those metrics by default. Maybe we could
>>>>>> at
>>>>>> > least
>>>>>> > > >>>>>>>>>>>>>>>>> introduce a feature
>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> switch for them? What do you think?
>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> Best,
>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> Dawid
>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> On 21/02/2019 03:13, Becket Qin wrote:
>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> Bump. If there is no objections to the
>>>>>> proposed
>>>>>> > > >>>>>>>>>>>>>>>>> metrics. I'll start a
>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> voting thread later toady.
>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> Thanks,
>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> Jiangjie (Becket) Qin
>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> On Mon, Feb 11, 2019 at 8:17 PM Becket
>>>>>> Qin
>>>>>> > > >>>>>>>>>>>>>>>>> <becket.qin@gmail.com <mailto:
>>>>>> becket.qin@gmail.com>>
>>>>>> > <
>>>>>> > > >>>>>>>>>>>>>>>>>>>>> becket.qin@gmail.com <mailto:
>>>>>> becket.qin@gmail.com
>>>>>> > >>
>>>>>> > > >>>>>>>>>>>>>>> wrote:
>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> Hi folks,
>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> I would like to start the FLIP
>>>>>> discussion thread
>>>>>> > > >>>>>>>>>>>>>> about
>>>>>> > > >>>>>>>>>>>>>>>>> standardize
>>>>>> > > >>>>>>>>>>>>>>>>>>> the
>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> connector metrics.
>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> In short, we would like to provide a
>>>>>> convention
>>>>>> > of
>>>>>> > > >>>>>>>>>>>>>>>>> Flink connector
>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> metrics. It will help simplify the
>>>>>> monitoring
>>>>>> > and
>>>>>> > > >>>>>>>>>>>>>>>>> alerting on Flink
>>>>>> > > >>>>>>>>>>>>>>>>>>>>> jobs.
>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> The FLIP link is following:
>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>
>>>>>> > > >>>>>>>>>
>>>>>> > > >>>>>>>
>>>>>> > > >>>>>
>>>>>> > > >>
>>>>>> > >
>>>>>> >
>>>>>> https://cwiki.apache.org/confluence/display/FLINK/FLIP-33%3A+Standardize+Connector+Metrics
>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> Thanks,
>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> Jiangjie (Becket) Qin
>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>
>>>>>> > > >>>>>>>>>>>>
>>>>>> > > >>>>>>>>>
>>>>>> > > >>>>>>>>>
>>>>>> > > >>>>>>>>>
>>>>>> > > >>>>>>>
>>>>>> > > >>>>>>>
>>>>>> > > >>>>>>>
>>>>>> > > >>>>>
>>>>>> > > >>>>>
>>>>>> > > >>
>>>>>> > > >>
>>>>>> > >
>>>>>> > >
>>>>>> >
>>>>>>
>>>>>>
>>>>>> --
>>>>>>
>>>>>> Konstantin Knauf
>>>>>>
>>>>>> https://twitter.com/snntrable
>>>>>>
>>>>>> https://github.com/knaufk
>>>>>>
>>>>>
Re: [DISCUSS] FLIP-33: Standardize connector metrics
Posted by Becket Qin <be...@gmail.com>.
Hi folks,
Thanks for all the great feedback. I have just updated FLIP-33 wiki with
the following changes:
1. Renaming. "currentFetchLatency" to "currentFetchEventTimeLag",
"currentLatency" to "currentEmitEventTimeLag".
2. Added the public interface code change required for the new metrics.
3. Added description of whether a metric is predefined or optional, and
which component is expected to update the metric.
Please let me know if you have any questions. I'll start a vote in two days
if there are no further concerns.
Thanks,
Jiangjie (Becket) Qin
On Wed, Sep 9, 2020 at 9:56 AM Becket Qin <be...@gmail.com> wrote:
> Hi Stephan,
>
> Thanks for the input. Just a few more clarifications / questions.
>
> *Num Bytes / Records Metrics*
>
> 1. At this point, the *numRecordsIn(Rate)* metrics exist in both
> OperatorIOMetricGroup and TaskIOMetricGroup. I did not find
> *numRecordsIn(Rate)* in the TaskIOMetricGroup updated anywhere other than
> in the unit tests. Am I missing something?
>
> 2. *numBytesIn(Rate)* metrics only exist in TaskIOMetricGroup. At this
> point, the SourceReaders only has access to a SourceReaderContext which
> provides an OperatorMetricGroup. So it seems that the connector developers
> are not able to update the *numBytesIn(Rate). *With the multiple Source
> chaining support, it is possible that there are multiple Sources are in the
> same task. So it looks that we need to add *numBytesIn(Rate)* to the
> operator metrics as well.
>
>
> *Current (Fetch) Latency*
>
> *currentFetchLatency* helps clearly tell whether the latency is caused by
> Flink or not. Backpressure is not the only reason that we see fetch
> latency. Even if there is no back pressure, the records may have passed a
> long pipeline before they entered Flink. For example, say the *currentLatency
> *is 10 seconds and there is no backpressure. Does that mean the record
> spent 10 seconds in the Source operator? If not, how much did Flink
> contribute to that 10 seconds of latency? These questions are frequently
> asked and hard to tell without the fetch latency.
>
> For "currentFetchLatency", we would need to understand timestamps before
>> the records are decoded. That is only possible for some sources, where the
>> client gives us the records in a (partially) decoded from already (like
>> Kafka). Then, some work has been done between the fetch time and the time
>> we update the metric already, so it is already a bit closer to the
>> "currentFetchLatency". I think following this train of thought, there is
>> diminished benefit from that specific metric.
>
>
> We may not have to report the fetch latency before records are decoded.
> One solution is to remember the* FetchTime* when the encoded records are
> fetched, and report the fetch latency after the records are decoded by
> computing (*FetchTime - EventTime*). An approximate implementation would
> be adding a *FetchTime *field to the *RecordsWithSplitIds* assuming that
> all the records in that data structure are fetched at the same time.
>
> Thoughts?
>
> Thanks,
>
> Jiangjie (Becket) Qin
>
> On Wed, Sep 9, 2020 at 12:42 AM Stephan Ewen <st...@ververica.com>
> wrote:
>
>> Thanks for reviving this, Becket!
>>
>> I think Konstantin's comments are great. I'd add these points:
>>
>> *Num Bytes / Records Metrics*
>>
>> For "numBytesIn" and "numRecordsIn", we should reuse the OperatorIOMetric
>> group, then it also gets reported to the overview page in the Web UI.
>>
>> The "numBytesInPerSecond" and "numRecordsInPerSecond" are automatically
>> derived metrics, no need to do anything once we populate the above two
>> metrics
>>
>>
>> *Current (Fetch) Latency*
>>
>> I would really go for "eventTimeLag" rather than "fetchLatency". I think
>> "eventTimeLag" is a term that has some adoption in the Flink community and
>> beyond.
>>
>> I am not so sure that I see the benefit between "currentLatency" and
>> "currentFetchLatency", (or event time lag before/after) as this only is
>> different by the time it takes to emit a batch.
>> - In a non-backpressured case, these should be virtually identical
>> (and both dominated by watermark lag, not the actual time it takes the
>> fetch to be emitted)
>> - In a backpressured case, why do you care about when data was
>> fetched, as opposed to emitted? Emitted time is relevant for application
>> semantics and checkpoints. Fetch time seems to be an implementation detail
>> (how much does the source buffer).
>>
>> The "currentLatency" (eventTimeLagAfter) can be computed out-of-the-box,
>> independent of a source implementation, so that is also a good argument to
>> make it the main metric.
>> We know timestamps and watermarks in the source. Except for cases where
>> no watermarks have been defined at all (batch jobs or pure processing time
>> jobs), in which case this metric should probably be "Infinite".
>>
>> For "currentFetchLatency", we would need to understand timestamps before
>> the records are decoded. That is only possible for some sources, where the
>> client gives us the records in a (partially) decoded from already (like
>> Kafka). Then, some work has been done between the fetch time and the time
>> we update the metric already, so it is already a bit closer to the
>> "currentFetchLatency". I think following this train of thought, there is
>> diminished benefit from that specific metric.
>>
>>
>> *Idle Time*
>>
>> I agree, it would be great to rename this. Maybe to "sourceWaitTime" or
>> "sourceIdleTime" so to make clear that this is not exactly the time that
>> Flink's processing pipeline is idle, but the time where the source does not
>> have new data.
>>
>> This is not an easy metric to collect, though (except maybe for the
>> sources that are only idle while they have no split assigned, like
>> continuous file source).
>>
>> *Source Specific Metrics*
>>
>> I believe source-specific would only be "sourceIdleTime",
>> "numRecordsInErrors", "pendingBytes", and "pendingRecords".
>>
>>
>> *Conclusion*
>>
>> We can probably add "numBytesIn" and "numRecordsIn" and "eventTimeLag"
>> right away, with little complexity.
>> I'd suggest to start with these right away.
>>
>> Best,
>> Stephan
>>
>>
>> On Tue, Sep 8, 2020 at 3:25 PM Becket Qin <be...@gmail.com> wrote:
>>
>>> Hey Konstantin,
>>>
>>> Thanks for the feedback and suggestions. Please see the reply below.
>>>
>>> * idleTime: In the meantime, a similar metric "idleTimeMsPerSecond" has
>>>> been introduced in https://issues.apache.org/jira/browse/FLINK-16864.
>>>> They
>>>> have a similar name, but different definitions of idleness,
>>>> e.g. "idleTimeMsPerSecond" considers the SourceTask idle, when it is
>>>> backpressured. Can we make it clearer that these two metrics mean
>>>> different
>>>> things?
>>>
>>>
>>> That is a good point. I did not notice this metric earlier. It seems
>>> that both metrics are useful to the users. One tells them how busy the
>>> source is and how much more throughput the source can handle. The other
>>> tells the users how long since the source has seen the last record, which
>>> is useful for debugging. I'll update the FLIP to make it clear.
>>>
>>> * "current(Fetch)Latency" I am wondering if
>>>> "eventTimeLag(Before|After)"
>>>> is more descriptive/clear. What do others think?
>>>
>>>
>>> I am quite open to the ideas on these names. In fact I also feel
>>> "current(Fetch)Latency" are not super intuitive. So it would be great if we
>>> can have better names.
>>>
>>> * Current(Fetch)Latency implies that the timestamps are directly
>>>> extracted in the source connector, right? Will this be the default for
>>>> FLIP-27 sources anyway?
>>>
>>>
>>> The "currentFetchLatency" will probably be reported by each source
>>> implementation, because the data fetching is done by SplitReaders and there
>>> is no base implementation. The "currentLatency", on the other hand, can be
>>> reported by the SourceReader base implementation. However, since developers
>>> can actually implement their own source connector without using our base
>>> implementation, these metric guidance are still useful for the connector
>>> developers in that case.
>>>
>>> * Does FLIP-33 also include the implementation of these metrics (to the
>>>> extent possible) for all connectors currently available in Apache Flink
>>>> or
>>>> is the "per-connector implementation" out-of-scope?
>>>
>>>
>>> FLIP-33 itself does not specify any implementation of those metrics. But
>>> the connectors we provide in Apache Flink will follow the guidance of
>>> FLIP-33 to emit those metrics when applicable. Maybe We can have some
>>> public static Strings defined for the metric names to help other connector
>>> developers follow the same guidance. I can also add that to the public
>>> interface section of the FLIP if we decide to do that.
>>>
>>> Thanks,
>>>
>>> Jiangjie (Becket) Qin
>>>
>>> On Tue, Sep 8, 2020 at 9:02 PM Becket Qin <be...@gmail.com> wrote:
>>>
>>>>
>>>>
>>>> On Tue, Sep 8, 2020 at 6:55 PM Konstantin Knauf <kn...@apache.org>
>>>> wrote:
>>>>
>>>>> Hi Becket,
>>>>>
>>>>> Thank you for picking up this FLIP. I have a few questions:
>>>>>
>>>>> * two thoughts on naming:
>>>>> * idleTime: In the meantime, a similar metric "idleTimeMsPerSecond"
>>>>> has
>>>>> been introduced in https://issues.apache.org/jira/browse/FLINK-16864.
>>>>> They
>>>>> have a similar name, but different definitions of idleness,
>>>>> e.g. "idleTimeMsPerSecond" considers the SourceTask idle, when it is
>>>>> backpressured. Can we make it clearer that these two metrics mean
>>>>> different
>>>>> things?
>>>>>
>>>>> * "current(Fetch)Latency" I am wondering if
>>>>> "eventTimeLag(Before|After)"
>>>>> is more descriptive/clear. What do others think?
>>>>>
>>>>> * Current(Fetch)Latency implies that the timestamps are directly
>>>>> extracted in the source connector, right? Will this be the default for
>>>>> FLIP-27 sources anyway?
>>>>>
>>>>> * Does FLIP-33 also include the implementation of these metrics (to the
>>>>> extent possible) for all connectors currently available in Apache
>>>>> Flink or
>>>>> is the "per-connector implementation" out-of-scope?
>>>>>
>>>>> Thanks,
>>>>>
>>>>> Konstantin
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>> On Fri, Sep 4, 2020 at 4:56 PM Becket Qin <be...@gmail.com>
>>>>> wrote:
>>>>>
>>>>> > Hi all,
>>>>> >
>>>>> > To complete the Source refactoring work, I'd like to revive this
>>>>> > discussion. Since the mail thread has been dormant for more than a
>>>>> year,
>>>>> > just to recap the motivation of the FLIP:
>>>>> >
>>>>> > 1. The FLIP proposes to standardize the connector metrics by giving
>>>>> > guidance on the metric specifications, including the name, type and
>>>>> meaning
>>>>> > of the metrics.
>>>>> > 2. It is OK for a connector to not emit some of the metrics in the
>>>>> metric
>>>>> > guidance, but if a metric of the same semantic is emitted, the
>>>>> > implementation should follow the guidance.
>>>>> > 3. It is OK for a connector to emit more metrics than what are
>>>>> listed in
>>>>> > the FLIP. This includes having an alias for a metric specified in
>>>>> the FLIP.
>>>>> > 4. We will implement some of the metrics out of the box in the
>>>>> default
>>>>> > implementation of FLIP-27, as long as it is applicable.
>>>>> >
>>>>> > The FLIP wiki is following:
>>>>> > https://cwiki.apache.org/confluence/display/FLINK/FLIP-33
>>>>> > %3A+Standardize+Connector+Metrics
>>>>> >
>>>>> > Any thoughts?
>>>>> >
>>>>> > Thanks,
>>>>> >
>>>>> > Jiangjie (Becket) Qin
>>>>> >
>>>>> >
>>>>> > On Fri, Jun 14, 2019 at 2:29 PM Piotr Nowojski <pi...@ververica.com>
>>>>> > wrote:
>>>>> >
>>>>> > > > we will need to revisit the convention list and adjust them
>>>>> accordingly
>>>>> > > when FLIP-27 is ready
>>>>> > >
>>>>> > >
>>>>> > > Yes, this sounds good :)
>>>>> > >
>>>>> > > Piotrek
>>>>> > >
>>>>> > > > On 13 Jun 2019, at 13:35, Becket Qin <be...@gmail.com>
>>>>> wrote:
>>>>> > > >
>>>>> > > > Hi Piotr,
>>>>> > > >
>>>>> > > > That's great to know. Chances are that we will need to revisit
>>>>> the
>>>>> > > > convention list and adjust them accordingly when FLIP-27 is
>>>>> ready, At
>>>>> > > that
>>>>> > > > point we can mark some of the metrics as available by default for
>>>>> > > > connectors implementing the new interface.
>>>>> > > >
>>>>> > > > Thanks,
>>>>> > > >
>>>>> > > > Jiangjie (Becket) Qin
>>>>> > > >
>>>>> > > > On Thu, Jun 13, 2019 at 3:51 PM Piotr Nowojski <
>>>>> piotr@ververica.com>
>>>>> > > wrote:
>>>>> > > >
>>>>> > > >> Thanks for driving this. I’ve just noticed one small thing.
>>>>> With new
>>>>> > > >> SourceReader interface Flink will be able to provide `idleTime`
>>>>> metric
>>>>> > > >> automatically.
>>>>> > > >>
>>>>> > > >> Piotrek
>>>>> > > >>
>>>>> > > >>> On 13 Jun 2019, at 03:30, Becket Qin <be...@gmail.com>
>>>>> wrote:
>>>>> > > >>>
>>>>> > > >>> Thanks all for the feedback and discussion.
>>>>> > > >>>
>>>>> > > >>> Since there wasn't any concern raised, I've started the voting
>>>>> thread
>>>>> > > for
>>>>> > > >>> this FLIP, but please feel free to continue the discussion
>>>>> here if
>>>>> > you
>>>>> > > >>> think something still needs to be addressed.
>>>>> > > >>>
>>>>> > > >>> Thanks,
>>>>> > > >>>
>>>>> > > >>> Jiangjie (Becket) Qin
>>>>> > > >>>
>>>>> > > >>>
>>>>> > > >>>
>>>>> > > >>> On Mon, Jun 10, 2019 at 9:10 AM Becket Qin <
>>>>> becket.qin@gmail.com>
>>>>> > > wrote:
>>>>> > > >>>
>>>>> > > >>>> Hi Piotr,
>>>>> > > >>>>
>>>>> > > >>>> Thanks for the comments. Yes, you are right. Users will have
>>>>> to look
>>>>> > > at
>>>>> > > >>>> other metrics to decide whether the pipeline is healthy or
>>>>> not in
>>>>> > the
>>>>> > > >> first
>>>>> > > >>>> place before they can use the time-based metric to fix the
>>>>> > bottleneck.
>>>>> > > >>>>
>>>>> > > >>>> I agree that once we have FLIP-27 ready, some of the metrics
>>>>> can
>>>>> > just
>>>>> > > be
>>>>> > > >>>> reported by the abstract implementation.
>>>>> > > >>>>
>>>>> > > >>>> I've updated FLIP-33 wiki page to add the pendingBytes and
>>>>> > > >> pendingRecords
>>>>> > > >>>> metric. Please let me know if you have any concern over the
>>>>> updated
>>>>> > > >> metric
>>>>> > > >>>> convention proposal.
>>>>> > > >>>>
>>>>> > > >>>> @Chesnay Schepler <ch...@apache.org> @Stephan Ewen
>>>>> > > >>>> <st...@ververica.com> will you also have time to take a
>>>>> look at
>>>>> > the
>>>>> > > >>>> proposed metric convention? If there is no further concern
>>>>> I'll
>>>>> > start
>>>>> > > a
>>>>> > > >>>> voting thread for this FLIP in two days.
>>>>> > > >>>>
>>>>> > > >>>> Thanks,
>>>>> > > >>>>
>>>>> > > >>>> Jiangjie (Becket) Qin
>>>>> > > >>>>
>>>>> > > >>>>
>>>>> > > >>>>
>>>>> > > >>>> On Wed, Jun 5, 2019 at 6:54 PM Piotr Nowojski <
>>>>> piotr@ververica.com>
>>>>> > > >> wrote:
>>>>> > > >>>>
>>>>> > > >>>>> Hi Becket,
>>>>> > > >>>>>
>>>>> > > >>>>> Thanks for the answer :)
>>>>> > > >>>>>
>>>>> > > >>>>>> By time-based metric, I meant the portion of time spent on
>>>>> > producing
>>>>> > > >> the
>>>>> > > >>>>>> record to downstream. For example, a source connector can
>>>>> report
>>>>> > > that
>>>>> > > >>>>> it's
>>>>> > > >>>>>> spending 80% of time to emit record to downstream processing
>>>>> > > pipeline.
>>>>> > > >>>>> In
>>>>> > > >>>>>> another case, a sink connector may report that its spending
>>>>> 30% of
>>>>> > > >> time
>>>>> > > >>>>>> producing the records to the external system.
>>>>> > > >>>>>>
>>>>> > > >>>>>> This is in some sense equivalent to the buffer usage metric:
>>>>> > > >>>>>
>>>>> > > >>>>>> - 80% of time spent on emitting records to downstream --->
>>>>> > > downstream
>>>>> > > >>>>>> node is bottleneck ---> output buffer is probably full.
>>>>> > > >>>>>> - 30% of time spent on emitting records to downstream --->
>>>>> > > downstream
>>>>> > > >>>>>> node is not bottleneck ---> output buffer is probably not
>>>>> full.
>>>>> > > >>>>>
>>>>> > > >>>>> If by “time spent on emitting records to downstream” you
>>>>> understand
>>>>> > > >>>>> “waiting on back pressure”, then I see your point. And I
>>>>> agree that
>>>>> > > >> some
>>>>> > > >>>>> kind of ratio/time based metric gives you more information.
>>>>> However
>>>>> > > >> under
>>>>> > > >>>>> “time spent on emitting records to downstream” might be
>>>>> hidden the
>>>>> > > >>>>> following (extreme) situation:
>>>>> > > >>>>>
>>>>> > > >>>>> 1. Job is barely able to handle influx of records, there is
>>>>> 99%
>>>>> > > >>>>> CPU/resource usage in the cluster, but nobody is
>>>>> > > >>>>> bottlenecked/backpressured, all output buffers are empty,
>>>>> everybody
>>>>> > > is
>>>>> > > >>>>> waiting in 1% of it’s time for more records to process.
>>>>> > > >>>>> 2. 80% time can still be spent on "down stream operators”,
>>>>> because
>>>>> > > they
>>>>> > > >>>>> are the CPU intensive operations, but this doesn’t mean that
>>>>> > > >> increasing the
>>>>> > > >>>>> parallelism down the stream will help with anything there.
>>>>> To the
>>>>> > > >> contrary,
>>>>> > > >>>>> increasing parallelism of the source operator might help to
>>>>> > increase
>>>>> > > >>>>> resource utilisation up to 100%.
>>>>> > > >>>>>
>>>>> > > >>>>> However, this “time based/ratio” approach can be extended to
>>>>> > > in/output
>>>>> > > >>>>> buffer usage. Besides collecting an information that
>>>>> input/output
>>>>> > > >> buffer is
>>>>> > > >>>>> full/empty, we can probe profile how often are buffer
>>>>> empty/full.
>>>>> > If
>>>>> > > >> output
>>>>> > > >>>>> buffer is full 1% of times, there is almost no back
>>>>> pressure. If
>>>>> > it’s
>>>>> > > >> full
>>>>> > > >>>>> 80% of times, there is some back pressure, if it’s full
>>>>> 99.9% of
>>>>> > > times,
>>>>> > > >>>>> there is huge back pressure.
>>>>> > > >>>>>
>>>>> > > >>>>> Now for autoscaling you could compare the input & output
>>>>> buffers
>>>>> > fill
>>>>> > > >>>>> ratio:
>>>>> > > >>>>>
>>>>> > > >>>>> 1. Both are high, the source of bottleneck is down the stream
>>>>> > > >>>>> 2. Output is low, input is high, this is the bottleneck and
>>>>> the
>>>>> > > higher
>>>>> > > >>>>> the difference, the bigger source of bottleneck is this is
>>>>> > > >> operator/task
>>>>> > > >>>>> 3. Output is high, input is low - there was some load spike
>>>>> that we
>>>>> > > are
>>>>> > > >>>>> currently finishing to process
>>>>> > > >>>>>
>>>>> > > >>>>>
>>>>> > > >>>>>
>>>>> > > >>>>> But long story short, we are probably diverging from the
>>>>> topic of
>>>>> > > this
>>>>> > > >>>>> discussion, and we can discuss this at some later point.
>>>>> > > >>>>>
>>>>> > > >>>>> For now, for sources:
>>>>> > > >>>>>
>>>>> > > >>>>> as I wrote before, +1 for:
>>>>> > > >>>>> - pending.bytes, Gauge
>>>>> > > >>>>> - pending.messages, Gauge
>>>>> > > >>>>>
>>>>> > > >>>>> When we will be developing/discussing SourceReader from
>>>>> FLIP-27 we
>>>>> > > >> might
>>>>> > > >>>>> then add:
>>>>> > > >>>>>
>>>>> > > >>>>> - in-memory.buffer.usage (0 - 100%)
>>>>> > > >>>>>
>>>>> > > >>>>> Which will be estimated automatically by Flink while user
>>>>> will be
>>>>> > > able
>>>>> > > >> to
>>>>> > > >>>>> override/provide better estimation.
>>>>> > > >>>>>
>>>>> > > >>>>> Piotrek
>>>>> > > >>>>>
>>>>> > > >>>>>> On 5 Jun 2019, at 05:42, Becket Qin <be...@gmail.com>
>>>>> wrote:
>>>>> > > >>>>>>
>>>>> > > >>>>>> Hi Piotr,
>>>>> > > >>>>>>
>>>>> > > >>>>>> Thanks for the explanation. Please see some clarifications
>>>>> below.
>>>>> > > >>>>>>
>>>>> > > >>>>>> By time-based metric, I meant the portion of time spent on
>>>>> > producing
>>>>> > > >> the
>>>>> > > >>>>>> record to downstream. For example, a source connector can
>>>>> report
>>>>> > > that
>>>>> > > >>>>> it's
>>>>> > > >>>>>> spending 80% of time to emit record to downstream processing
>>>>> > > pipeline.
>>>>> > > >>>>> In
>>>>> > > >>>>>> another case, a sink connector may report that its spending
>>>>> 30% of
>>>>> > > >> time
>>>>> > > >>>>>> producing the records to the external system.
>>>>> > > >>>>>>
>>>>> > > >>>>>> This is in some sense equivalent to the buffer usage metric:
>>>>> > > >>>>>> - 80% of time spent on emitting records to downstream --->
>>>>> > > downstream
>>>>> > > >>>>>> node is bottleneck ---> output buffer is probably full.
>>>>> > > >>>>>> - 30% of time spent on emitting records to downstream --->
>>>>> > > downstream
>>>>> > > >>>>>> node is not bottleneck ---> output buffer is probably not
>>>>> full.
>>>>> > > >>>>>>
>>>>> > > >>>>>> However, the time-based metric has a few advantages that the
>>>>> > buffer
>>>>> > > >>>>> usage
>>>>> > > >>>>>> metric may not have.
>>>>> > > >>>>>>
>>>>> > > >>>>>> 1. Buffer usage metric may not be applicable to all the
>>>>> connector
>>>>> > > >>>>>> implementations, while reporting time-based metric are
>>>>> always
>>>>> > > doable.
>>>>> > > >>>>>> Some source connectors may not have any input buffer, or
>>>>> they may
>>>>> > > use
>>>>> > > >>>>> some
>>>>> > > >>>>>> third party library that does not expose the input buffer
>>>>> at all.
>>>>> > > >>>>>> Similarly, for sink connectors, the implementation may not
>>>>> have
>>>>> > any
>>>>> > > >>>>> output
>>>>> > > >>>>>> buffer, or the third party library does not expose such
>>>>> buffer.
>>>>> > > >>>>>>
>>>>> > > >>>>>> 2. Although both type of metrics can detect bottleneck,
>>>>> time-based
>>>>> > > >>>>> metrics
>>>>> > > >>>>>> can be used to generate a more informed action to remove the
>>>>> > > >> bottleneck.
>>>>> > > >>>>>> For example, when the downstream is bottleneck, the output
>>>>> buffer
>>>>> > > >> usage
>>>>> > > >>>>>> metric is likely to be 100%, and the input buffer usage
>>>>> might be
>>>>> > 0%.
>>>>> > > >>>>> That
>>>>> > > >>>>>> means we don't know what is the suitable parallelism to
>>>>> lift the
>>>>> > > >>>>>> bottleneck. The time-based metric, on the other hand, would
>>>>> give
>>>>> > > >> useful
>>>>> > > >>>>>> information, e.g. if 80% of time was spent on emitting
>>>>> records, we
>>>>> > > can
>>>>> > > >>>>>> roughly increase the downstream node parallelism by 4 times.
>>>>> > > >>>>>>
>>>>> > > >>>>>> Admittedly, the time-based metrics are more expensive than
>>>>> buffer
>>>>> > > >>>>> usage. So
>>>>> > > >>>>>> we may have to do some sampling to reduce the cost. But in
>>>>> > general,
>>>>> > > >>>>> using
>>>>> > > >>>>>> time-based metrics seems worth adding.
>>>>> > > >>>>>>
>>>>> > > >>>>>> That being said, I don't think buffer usage metric and
>>>>> time-based
>>>>> > > >>>>> metrics
>>>>> > > >>>>>> are mutually exclusive. We can probably have both. It is
>>>>> just that
>>>>> > > in
>>>>> > > >>>>>> practice, features like auto-scaling might prefer time-based
>>>>> > metrics
>>>>> > > >> for
>>>>> > > >>>>>> the reason stated above.
>>>>> > > >>>>>>
>>>>> > > >>>>>>> 1. Define the metrics that would allow us to manually
>>>>> detect
>>>>> > > >>>>> bottlenecks.
>>>>> > > >>>>>> As I wrote, we already have them in most of the places,
>>>>> except of
>>>>> > > >>>>>> sources/sinks.
>>>>> > > >>>>>>> 2. Use those metrics, to automatically detect bottlenecks.
>>>>> > > Currently
>>>>> > > >> we
>>>>> > > >>>>>> are only automatically detecting back pressure and
>>>>> reporting it to
>>>>> > > the
>>>>> > > >>>>> user
>>>>> > > >>>>>> in web UI (is it exposed as a metric at all?). Detecting
>>>>> the root
>>>>> > > >> cause
>>>>> > > >>>>> of
>>>>> > > >>>>>> the back pressure (bottleneck) is one step further.
>>>>> > > >>>>>>> 3. Use the knowledge about where exactly the bottleneck is
>>>>> > located,
>>>>> > > >> to
>>>>> > > >>>>>> try to do something with it.
>>>>> > > >>>>>>
>>>>> > > >>>>>> As explained above, I think time-based metric also
>>>>> addresses item
>>>>> > 1
>>>>> > > >> and
>>>>> > > >>>>>> item 2.
>>>>> > > >>>>>>
>>>>> > > >>>>>> Any thoughts？
>>>>> > > >>>>>>
>>>>> > > >>>>>> Thanks,
>>>>> > > >>>>>>
>>>>> > > >>>>>> Jiangjie (Becket) Qin
>>>>> > > >>>>>>
>>>>> > > >>>>>>
>>>>> > > >>>>>>
>>>>> > > >>>>>> On Mon, Jun 3, 2019 at 4:14 PM Piotr Nowojski <
>>>>> > piotr@ververica.com>
>>>>> > > >>>>> wrote:
>>>>> > > >>>>>>
>>>>> > > >>>>>>> Hi again :)
>>>>> > > >>>>>>>
>>>>> > > >>>>>>>> - pending.bytes, Gauge
>>>>> > > >>>>>>>> - pending.messages, Gauge
>>>>> > > >>>>>>>
>>>>> > > >>>>>>>
>>>>> > > >>>>>>> +1
>>>>> > > >>>>>>>
>>>>> > > >>>>>>> And true, instead of overloading one of the metric it is
>>>>> better
>>>>> > > when
>>>>> > > >>>>> user
>>>>> > > >>>>>>> can choose to provide only one of them.
>>>>> > > >>>>>>>
>>>>> > > >>>>>>> Re 2:
>>>>> > > >>>>>>>
>>>>> > > >>>>>>>> If I understand correctly, this metric along with the
>>>>> pending
>>>>> > > >> mesages
>>>>> > > >>>>> /
>>>>> > > >>>>>>>> bytes would answer the questions of:
>>>>> > > >>>>>>>
>>>>> > > >>>>>>>> - Does the connector consume fast enough? Lagging behind
>>>>> + empty
>>>>> > > >>>>> buffer
>>>>> > > >>>>>>> =
>>>>> > > >>>>>>>> cannot consume fast enough.
>>>>> > > >>>>>>>> - Does the connector emit fast enough? Lagging behind +
>>>>> full
>>>>> > > buffer
>>>>> > > >> =
>>>>> > > >>>>>>>> cannot emit fast enough, i.e. the Flink pipeline is slow.
>>>>> > > >>>>>>>
>>>>> > > >>>>>>> Yes, exactly. This can also be used to support decisions
>>>>> like
>>>>> > > >> changing
>>>>> > > >>>>> the
>>>>> > > >>>>>>> parallelism of the sources and/or down stream operators.
>>>>> > > >>>>>>>
>>>>> > > >>>>>>> I’m not sure if I understand your proposal with time based
>>>>> > > >>>>> measurements.
>>>>> > > >>>>>>> Maybe I’m missing something, but I do not see how
>>>>> measuring time
>>>>> > > >> alone
>>>>> > > >>>>>>> could answer the problem: where is the bottleneck. Time
>>>>> spent on
>>>>> > > the
>>>>> > > >>>>>>> next/emit might be short or long (depending on how heavy to
>>>>> > process
>>>>> > > >> the
>>>>> > > >>>>>>> record is) and the source can still be bottlenecked/back
>>>>> > pressured
>>>>> > > or
>>>>> > > >>>>> not.
>>>>> > > >>>>>>> Usually the easiest and the most reliable way how to detect
>>>>> > > >>>>> bottlenecks is
>>>>> > > >>>>>>> by checking usage of input & output buffers, since when
>>>>> input
>>>>> > > buffer
>>>>> > > >> is
>>>>> > > >>>>>>> full while output buffer is empty, that’s the definition
>>>>> of a
>>>>> > > >>>>> bottleneck.
>>>>> > > >>>>>>> Also this is usually very easy and cheap to measure (it
>>>>> works
>>>>> > > >>>>> effectively
>>>>> > > >>>>>>> the same way as current’s Flink back pressure monitoring,
>>>>> but
>>>>> > more
>>>>> > > >>>>> cleanly,
>>>>> > > >>>>>>> without probing thread’s stack traces).
>>>>> > > >>>>>>>
>>>>> > > >>>>>>> Also keep in mind that we are already using the buffer
>>>>> usage
>>>>> > > metrics
>>>>> > > >>>>> for
>>>>> > > >>>>>>> detecting the bottlenecks in Flink’s internal network
>>>>> exchanges
>>>>> > > >> (manual
>>>>> > > >>>>>>> work). That’s the reason why I wanted to extend this to
>>>>> > > >> sources/sinks,
>>>>> > > >>>>>>> since they are currently our blind spot.
>>>>> > > >>>>>>>
>>>>> > > >>>>>>>> One feature we are currently working on to scale Flink
>>>>> > > automatically
>>>>> > > >>>>>>> relies
>>>>> > > >>>>>>>> on some metrics answering the same question
>>>>> > > >>>>>>>
>>>>> > > >>>>>>> That would be very helpful feature. I think in order to
>>>>> achieve
>>>>> > > that
>>>>> > > >> we
>>>>> > > >>>>>>> would need to:
>>>>> > > >>>>>>> 1. Define the metrics that would allow us to manually
>>>>> detect
>>>>> > > >>>>> bottlenecks.
>>>>> > > >>>>>>> As I wrote, we already have them in most of the places,
>>>>> except of
>>>>> > > >>>>>>> sources/sinks.
>>>>> > > >>>>>>> 2. Use those metrics, to automatically detect bottlenecks.
>>>>> > > Currently
>>>>> > > >> we
>>>>> > > >>>>>>> are only automatically detecting back pressure and
>>>>> reporting it
>>>>> > to
>>>>> > > >> the
>>>>> > > >>>>> user
>>>>> > > >>>>>>> in web UI (is it exposed as a metric at all?). Detecting
>>>>> the root
>>>>> > > >>>>> cause of
>>>>> > > >>>>>>> the back pressure (bottleneck) is one step further.
>>>>> > > >>>>>>> 3. Use the knowledge about where exactly the bottleneck is
>>>>> > located,
>>>>> > > >> to
>>>>> > > >>>>> try
>>>>> > > >>>>>>> to do something with it.
>>>>> > > >>>>>>>
>>>>> > > >>>>>>> I think you are aiming for point 3., but before we reach
>>>>> it, we
>>>>> > are
>>>>> > > >>>>> still
>>>>> > > >>>>>>> missing 1. & 2. Also even if we have 3., there is a value
>>>>> in 1 &
>>>>> > 2
>>>>> > > >> for
>>>>> > > >>>>>>> manual analysis/dashboards.
>>>>> > > >>>>>>>
>>>>> > > >>>>>>> However, having the knowledge of where the bottleneck is,
>>>>> doesn’t
>>>>> > > >>>>>>> necessarily mean that we know what we can do about it. For
>>>>> > example
>>>>> > > >>>>>>> increasing parallelism might or might not help with
>>>>> anything
>>>>> > (data
>>>>> > > >>>>> skew,
>>>>> > > >>>>>>> bottleneck on some resource that does not scale), but this
>>>>> remark
>>>>> > > >>>>> applies
>>>>> > > >>>>>>> always, regardless of the way how did we detect the
>>>>> bottleneck.
>>>>> > > >>>>>>>
>>>>> > > >>>>>>> Piotrek
>>>>> > > >>>>>>>
>>>>> > > >>>>>>>> On 3 Jun 2019, at 06:16, Becket Qin <becket.qin@gmail.com
>>>>> >
>>>>> > wrote:
>>>>> > > >>>>>>>>
>>>>> > > >>>>>>>> Hi Piotr,
>>>>> > > >>>>>>>>
>>>>> > > >>>>>>>> Thanks for the suggestion. Some thoughts below:
>>>>> > > >>>>>>>>
>>>>> > > >>>>>>>> Re 1: The pending messages / bytes.
>>>>> > > >>>>>>>> I completely agree these are very useful metrics and we
>>>>> should
>>>>> > > >> expect
>>>>> > > >>>>> the
>>>>> > > >>>>>>>> connector to report. WRT the way to expose them, it seems
>>>>> more
>>>>> > > >>>>> consistent
>>>>> > > >>>>>>>> to add two metrics instead of adding a method (unless
>>>>> there are
>>>>> > > >> other
>>>>> > > >>>>> use
>>>>> > > >>>>>>>> cases other than metric reporting). So we can add the
>>>>> following
>>>>> > > two
>>>>> > > >>>>>>> metrics.
>>>>> > > >>>>>>>> - pending.bytes, Gauge
>>>>> > > >>>>>>>> - pending.messages, Gauge
>>>>> > > >>>>>>>> Applicable connectors can choose to report them. These two
>>>>> > metrics
>>>>> > > >>>>> along
>>>>> > > >>>>>>>> with latency should be sufficient for users to understand
>>>>> the
>>>>> > > >> progress
>>>>> > > >>>>>>> of a
>>>>> > > >>>>>>>> connector.
>>>>> > > >>>>>>>>
>>>>> > > >>>>>>>>
>>>>> > > >>>>>>>> Re 2: Number of buffered data in-memory of the connector
>>>>> > > >>>>>>>> If I understand correctly, this metric along with the
>>>>> pending
>>>>> > > >> mesages
>>>>> > > >>>>> /
>>>>> > > >>>>>>>> bytes would answer the questions of:
>>>>> > > >>>>>>>> - Does the connector consume fast enough? Lagging behind
>>>>> + empty
>>>>> > > >>>>> buffer
>>>>> > > >>>>>>> =
>>>>> > > >>>>>>>> cannot consume fast enough.
>>>>> > > >>>>>>>> - Does the connector emit fast enough? Lagging behind +
>>>>> full
>>>>> > > buffer
>>>>> > > >> =
>>>>> > > >>>>>>>> cannot emit fast enough, i.e. the Flink pipeline is slow.
>>>>> > > >>>>>>>>
>>>>> > > >>>>>>>> One feature we are currently working on to scale Flink
>>>>> > > automatically
>>>>> > > >>>>>>> relies
>>>>> > > >>>>>>>> on some metrics answering the same question, more
>>>>> specifically,
>>>>> > we
>>>>> > > >> are
>>>>> > > >>>>>>>> profiling the time spent on .next() method (time to
>>>>> consume) and
>>>>> > > the
>>>>> > > >>>>> time
>>>>> > > >>>>>>>> spent on .collect() method (time to emit / process). One
>>>>> > advantage
>>>>> > > >> of
>>>>> > > >>>>>>> such
>>>>> > > >>>>>>>> method level time cost allows us to calculate the
>>>>> parallelism
>>>>> > > >>>>> required to
>>>>> > > >>>>>>>> keep up in case their is a lag.
>>>>> > > >>>>>>>>
>>>>> > > >>>>>>>> However, one concern I have regarding such metric is that
>>>>> they
>>>>> > are
>>>>> > > >>>>>>>> implementation specific. Either profiling on the method
>>>>> time, or
>>>>> > > >>>>>>> reporting
>>>>> > > >>>>>>>> buffer usage assumes the connector are implemented in
>>>>> such a
>>>>> > way.
>>>>> > > A
>>>>> > > >>>>>>>> slightly better solution might be have the following
>>>>> metric:
>>>>> > > >>>>>>>>
>>>>> > > >>>>>>>> - EmitTimeRatio (or FetchTimeRatio): The time spent on
>>>>> emitting
>>>>> > > >>>>>>>> records / Total time elapsed.
>>>>> > > >>>>>>>>
>>>>> > > >>>>>>>> This assumes that the source connectors have to emit the
>>>>> records
>>>>> > > to
>>>>> > > >>>>> the
>>>>> > > >>>>>>>> downstream at some point. The emission may take some time
>>>>> ( e.g.
>>>>> > > go
>>>>> > > >>>>>>> through
>>>>> > > >>>>>>>> chained operators). And the rest of the time are spent to
>>>>> > prepare
>>>>> > > >> the
>>>>> > > >>>>>>>> record to emit, including time for consuming and format
>>>>> > > conversion,
>>>>> > > >>>>> etc.
>>>>> > > >>>>>>>> Ideally, we'd like to see the time spent on record fetch
>>>>> and
>>>>> > emit
>>>>> > > to
>>>>> > > >>>>> be
>>>>> > > >>>>>>>> about the same, so no one is bottleneck for the other.
>>>>> > > >>>>>>>>
>>>>> > > >>>>>>>> The downside of these time based metrics is additional
>>>>> overhead
>>>>> > to
>>>>> > > >> get
>>>>> > > >>>>>>> the
>>>>> > > >>>>>>>> time, therefore sampling might be needed. But in practice
>>>>> I feel
>>>>> > > >> such
>>>>> > > >>>>>>> time
>>>>> > > >>>>>>>> based metric might be more useful if we want to take
>>>>> action.
>>>>> > > >>>>>>>>
>>>>> > > >>>>>>>>
>>>>> > > >>>>>>>> I think we should absolutely add metrics in (1) to the
>>>>> metric
>>>>> > > >>>>> convention.
>>>>> > > >>>>>>>> We could also add the metrics mentioned in (2) if we reach
>>>>> > > consensus
>>>>> > > >>>>> on
>>>>> > > >>>>>>>> that. What do you think?
>>>>> > > >>>>>>>>
>>>>> > > >>>>>>>> Thanks,
>>>>> > > >>>>>>>>
>>>>> > > >>>>>>>> Jiangjie (Becket) Qin
>>>>> > > >>>>>>>>
>>>>> > > >>>>>>>>
>>>>> > > >>>>>>>> On Fri, May 31, 2019 at 4:26 PM Piotr Nowojski <
>>>>> > > piotr@ververica.com
>>>>> > > >>>
>>>>> > > >>>>>>> wrote:
>>>>> > > >>>>>>>>
>>>>> > > >>>>>>>>> Hey Becket,
>>>>> > > >>>>>>>>>
>>>>> > > >>>>>>>>> Re 1a) and 1b) +1 from my side.
>>>>> > > >>>>>>>>>
>>>>> > > >>>>>>>>> I’ve discussed this issue:
>>>>> > > >>>>>>>>>
>>>>> > > >>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>> 2. It would be nice to have metrics, that allow us to
>>>>> check
>>>>> > > the
>>>>> > > >>>>> cause
>>>>> > > >>>>>>>>> of
>>>>> > > >>>>>>>>>>>> back pressure:
>>>>> > > >>>>>>>>>>>> a) for sources, length of input queue (in bytes? Or
>>>>> boolean
>>>>> > > >>>>>>>>>>>> hasSomethingl/isEmpty)
>>>>> > > >>>>>>>>>>>> b) for sinks, length of output queue (in bytes? Or
>>>>> boolean
>>>>> > > >>>>>>>>>>>> hasSomething/isEmpty)
>>>>> > > >>>>>>>>>
>>>>> > > >>>>>>>>> With Nico at some lengths and he also saw the benefits
>>>>> of them.
>>>>> > > We
>>>>> > > >>>>> also
>>>>> > > >>>>>>>>> have more concrete proposal for that.
>>>>> > > >>>>>>>>>
>>>>> > > >>>>>>>>> Actually there are two really useful metrics, that we are
>>>>> > missing
>>>>> > > >>>>>>>>> currently:
>>>>> > > >>>>>>>>>
>>>>> > > >>>>>>>>> 1. Number of data/records/bytes in the backlog to
>>>>> process. For
>>>>> > > >>>>> example
>>>>> > > >>>>>>>>> remaining number of bytes in unread files. Or pending
>>>>> data in
>>>>> > > Kafka
>>>>> > > >>>>>>> topics.
>>>>> > > >>>>>>>>> 2. Number of buffered data in-memory of the connector,
>>>>> that are
>>>>> > > >>>>> waiting
>>>>> > > >>>>>>> to
>>>>> > > >>>>>>>>> be processed pushed to Flink pipeline.
>>>>> > > >>>>>>>>>
>>>>> > > >>>>>>>>> Re 1:
>>>>> > > >>>>>>>>> This would have to be a metric provided directly by a
>>>>> > connector.
>>>>> > > It
>>>>> > > >>>>>>> could
>>>>> > > >>>>>>>>> be an undefined `int`:
>>>>> > > >>>>>>>>>
>>>>> > > >>>>>>>>> `int backlog` - estimate of pending work.
>>>>> > > >>>>>>>>>
>>>>> > > >>>>>>>>> “Undefined” meaning that it would be up to a connector to
>>>>> > decided
>>>>> > > >>>>>>> whether
>>>>> > > >>>>>>>>> it’s measured in bytes, records, pending files or
>>>>> whatever it
>>>>> > is
>>>>> > > >>>>>>> possible
>>>>> > > >>>>>>>>> to provide by the connector. This is because I assume
>>>>> not every
>>>>> > > >>>>>>> connector
>>>>> > > >>>>>>>>> can provide exact number and for some of them it might be
>>>>> > > >> impossible
>>>>> > > >>>>> to
>>>>> > > >>>>>>>>> provide records number of bytes count.
>>>>> > > >>>>>>>>>
>>>>> > > >>>>>>>>> Re 2:
>>>>> > > >>>>>>>>> This metric could be either provided by a connector, or
>>>>> > > calculated
>>>>> > > >>>>>>> crudely
>>>>> > > >>>>>>>>> by Flink:
>>>>> > > >>>>>>>>>
>>>>> > > >>>>>>>>> `float bufferUsage` - value from [0.0, 1.0] range
>>>>> > > >>>>>>>>>
>>>>> > > >>>>>>>>> Percentage of used in memory buffers, like in Kafka’s
>>>>> handover.
>>>>> > > >>>>>>>>>
>>>>> > > >>>>>>>>> It could be crudely implemented by Flink with FLIP-27
>>>>> > > >>>>>>>>> SourceReader#isAvailable. If SourceReader is not
>>>>> available
>>>>> > > reported
>>>>> > > >>>>>>>>> `bufferUsage` could be 0.0. If it is available, it could
>>>>> be
>>>>> > 1.0.
>>>>> > > I
>>>>> > > >>>>> think
>>>>> > > >>>>>>>>> this would be a good enough estimation for most of the
>>>>> use
>>>>> > cases
>>>>> > > >>>>> (that
>>>>> > > >>>>>>>>> could be overloaded and implemented better if desired).
>>>>> > > Especially
>>>>> > > >>>>>>> since we
>>>>> > > >>>>>>>>> are reporting only probed values: if probed values are
>>>>> almost
>>>>> > > >> always
>>>>> > > >>>>>>> “1.0”,
>>>>> > > >>>>>>>>> it would mean that we have a back pressure. If they are
>>>>> almost
>>>>> > > >> always
>>>>> > > >>>>>>>>> “0.0”, there is probably no back pressure at the sources.
>>>>> > > >>>>>>>>>
>>>>> > > >>>>>>>>> What do you think about this?
>>>>> > > >>>>>>>>>
>>>>> > > >>>>>>>>> Piotrek
>>>>> > > >>>>>>>>>
>>>>> > > >>>>>>>>>> On 30 May 2019, at 11:41, Becket Qin <
>>>>> becket.qin@gmail.com>
>>>>> > > >> wrote:
>>>>> > > >>>>>>>>>>
>>>>> > > >>>>>>>>>> Hi all,
>>>>> > > >>>>>>>>>>
>>>>> > > >>>>>>>>>> Thanks a lot for all the feedback and comments. I'd
>>>>> like to
>>>>> > > >> continue
>>>>> > > >>>>>>> the
>>>>> > > >>>>>>>>>> discussion on this FLIP.
>>>>> > > >>>>>>>>>>
>>>>> > > >>>>>>>>>> I updated the FLIP-33 wiki to remove all the histogram
>>>>> metrics
>>>>> > > >> from
>>>>> > > >>>>> the
>>>>> > > >>>>>>>>>> first version of metric convention due to the
>>>>> performance
>>>>> > > concern.
>>>>> > > >>>>> The
>>>>> > > >>>>>>>>> plan
>>>>> > > >>>>>>>>>> is to introduce them later when we have a mechanism to
>>>>> opt
>>>>> > > in/out
>>>>> > > >>>>>>>>> metrics.
>>>>> > > >>>>>>>>>> At that point, users can decide whether they want to
>>>>> pay the
>>>>> > > cost
>>>>> > > >> to
>>>>> > > >>>>>>> get
>>>>> > > >>>>>>>>>> the metric or not.
>>>>> > > >>>>>>>>>>
>>>>> > > >>>>>>>>>> As Stephan suggested, for this FLIP, let's first try to
>>>>> agree
>>>>> > on
>>>>> > > >> the
>>>>> > > >>>>>>>>> small
>>>>> > > >>>>>>>>>> list of conventional metrics that connectors should
>>>>> follow.
>>>>> > > >>>>>>>>>> Just to be clear, the purpose of the convention is not
>>>>> to
>>>>> > > enforce
>>>>> > > >>>>> every
>>>>> > > >>>>>>>>>> connector to report all these metrics, but to provide a
>>>>> > guidance
>>>>> > > >> in
>>>>> > > >>>>>>> case
>>>>> > > >>>>>>>>>> these metrics are reported by some connectors.
>>>>> > > >>>>>>>>>>
>>>>> > > >>>>>>>>>>
>>>>> > > >>>>>>>>>> @ Stephan & Chesnay,
>>>>> > > >>>>>>>>>>
>>>>> > > >>>>>>>>>> Regarding the duplication of `RecordsIn` metric in
>>>>> operator /
>>>>> > > task
>>>>> > > >>>>>>>>>> IOMetricGroups, from what I understand, for source
>>>>> operator,
>>>>> > it
>>>>> > > is
>>>>> > > >>>>>>>>> actually
>>>>> > > >>>>>>>>>> the SourceFunction that reports the operator level
>>>>> > > >>>>>>>>>> RecordsIn/RecordsInPerSecond metric. So they are
>>>>> essentially
>>>>> > the
>>>>> > > >>>>> same
>>>>> > > >>>>>>>>>> metric in the operator level IOMetricGroup. Similarly
>>>>> for the
>>>>> > > Sink
>>>>> > > >>>>>>>>>> operator, the operator level
>>>>> RecordsOut/RecordsOutPerSecond
>>>>> > > >> metrics
>>>>> > > >>>>> are
>>>>> > > >>>>>>>>>> also reported by the Sink function. I marked them as
>>>>> existing
>>>>> > in
>>>>> > > >> the
>>>>> > > >>>>>>>>>> FLIP-33 wiki page. Please let me know if I
>>>>> misunderstood.
>>>>> > > >>>>>>>>>>
>>>>> > > >>>>>>>>>> Thanks,
>>>>> > > >>>>>>>>>>
>>>>> > > >>>>>>>>>> Jiangjie (Becket) Qin
>>>>> > > >>>>>>>>>>
>>>>> > > >>>>>>>>>>
>>>>> > > >>>>>>>>>> On Thu, May 30, 2019 at 5:16 PM Becket Qin <
>>>>> > > becket.qin@gmail.com>
>>>>> > > >>>>>>> wrote:
>>>>> > > >>>>>>>>>>
>>>>> > > >>>>>>>>>>> Hi Piotr,
>>>>> > > >>>>>>>>>>>
>>>>> > > >>>>>>>>>>> Thanks a lot for the feedback.
>>>>> > > >>>>>>>>>>>
>>>>> > > >>>>>>>>>>> 1a) I guess you are referring to the part that
>>>>> "original
>>>>> > system
>>>>> > > >>>>>>> specific
>>>>> > > >>>>>>>>>>> metrics should also be reported". The performance
>>>>> impact
>>>>> > > depends
>>>>> > > >> on
>>>>> > > >>>>>>> the
>>>>> > > >>>>>>>>>>> implementation. An efficient implementation would only
>>>>> record
>>>>> > > the
>>>>> > > >>>>>>> metric
>>>>> > > >>>>>>>>>>> once, but report them with two different metric names.
>>>>> This
>>>>> > is
>>>>> > > >>>>>>> unlikely
>>>>> > > >>>>>>>>> to
>>>>> > > >>>>>>>>>>> hurt performance.
>>>>> > > >>>>>>>>>>>
>>>>> > > >>>>>>>>>>> 1b) Yes, I agree that we should avoid adding overhead
>>>>> to the
>>>>> > > >>>>> critical
>>>>> > > >>>>>>>>> path
>>>>> > > >>>>>>>>>>> by all means. This is sometimes a tradeoff, running
>>>>> blindly
>>>>> > > >> without
>>>>> > > >>>>>>> any
>>>>> > > >>>>>>>>>>> metric gives best performance, but sometimes might be
>>>>> > > frustrating
>>>>> > > >>>>> when
>>>>> > > >>>>>>>>> we
>>>>> > > >>>>>>>>>>> debug some issues.
>>>>> > > >>>>>>>>>>>
>>>>> > > >>>>>>>>>>> 2. The metrics are indeed very useful. Are they
>>>>> supposed to
>>>>> > be
>>>>> > > >>>>>>> reported
>>>>> > > >>>>>>>>> by
>>>>> > > >>>>>>>>>>> the connectors or Flink itself? At this point FLIP-33
>>>>> is more
>>>>> > > >>>>> focused
>>>>> > > >>>>>>> on
>>>>> > > >>>>>>>>>>> provide a guidance to the connector authors on the
>>>>> metrics
>>>>> > > >>>>> reporting.
>>>>> > > >>>>>>>>> That
>>>>> > > >>>>>>>>>>> said, after FLIP-27, I think we should absolutely
>>>>> report
>>>>> > these
>>>>> > > >>>>> metrics
>>>>> > > >>>>>>>>> in
>>>>> > > >>>>>>>>>>> the abstract implementation. In any case, the metric
>>>>> > convention
>>>>> > > >> in
>>>>> > > >>>>>>> this
>>>>> > > >>>>>>>>>>> list are expected to evolve over time.
>>>>> > > >>>>>>>>>>>
>>>>> > > >>>>>>>>>>> Thanks,
>>>>> > > >>>>>>>>>>>
>>>>> > > >>>>>>>>>>> Jiangjie (Becket) Qin
>>>>> > > >>>>>>>>>>>
>>>>> > > >>>>>>>>>>> On Tue, May 28, 2019 at 6:24 PM Piotr Nowojski <
>>>>> > > >>>>> piotr@ververica.com>
>>>>> > > >>>>>>>>>>> wrote:
>>>>> > > >>>>>>>>>>>
>>>>> > > >>>>>>>>>>>> Hi,
>>>>> > > >>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>> Thanks for the proposal and driving the effort here
>>>>> Becket
>>>>> > :)
>>>>> > > >> I’ve
>>>>> > > >>>>>>> read
>>>>> > > >>>>>>>>>>>> through the FLIP-33 [1], and here are couple of my
>>>>> thoughts.
>>>>> > > >>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>> Big +1 for standardising the metric names between
>>>>> > connectors,
>>>>> > > it
>>>>> > > >>>>> will
>>>>> > > >>>>>>>>>>>> definitely help us and users a lot.
>>>>> > > >>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>> Issues/questions/things to discuss that I’ve thought
>>>>> of:
>>>>> > > >>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>> 1a. If we are about to duplicate some metrics, can
>>>>> this
>>>>> > > become a
>>>>> > > >>>>>>>>>>>> performance issue?
>>>>> > > >>>>>>>>>>>> 1b. Generally speaking, we should make sure that
>>>>> collecting
>>>>> > > >> those
>>>>> > > >>>>>>>>> metrics
>>>>> > > >>>>>>>>>>>> is as non intrusive as possible, especially that they
>>>>> will
>>>>> > > need
>>>>> > > >>>>> to be
>>>>> > > >>>>>>>>>>>> updated once per record. (They might be collected more
>>>>> > rarely
>>>>> > > >> with
>>>>> > > >>>>>>> some
>>>>> > > >>>>>>>>>>>> overhead, but the hot path of updating it per record
>>>>> will
>>>>> > need
>>>>> > > >> to
>>>>> > > >>>>> be
>>>>> > > >>>>>>> as
>>>>> > > >>>>>>>>>>>> quick as possible). That includes both avoiding heavy
>>>>> > > >> computation
>>>>> > > >>>>> on
>>>>> > > >>>>>>>>> per
>>>>> > > >>>>>>>>>>>> record path: histograms?, measuring time for time
>>>>> based
>>>>> > > metrics
>>>>> > > >>>>> (per
>>>>> > > >>>>>>>>>>>> second) (System.currentTimeMillis() depending on the
>>>>> > > >>>>> implementation
>>>>> > > >>>>>>> can
>>>>> > > >>>>>>>>>>>> invoke a system call)
>>>>> > > >>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>> 2. It would be nice to have metrics, that allow us to
>>>>> check
>>>>> > > the
>>>>> > > >>>>> cause
>>>>> > > >>>>>>>>> of
>>>>> > > >>>>>>>>>>>> back pressure:
>>>>> > > >>>>>>>>>>>> a) for sources, length of input queue (in bytes? Or
>>>>> boolean
>>>>> > > >>>>>>>>>>>> hasSomethingl/isEmpty)
>>>>> > > >>>>>>>>>>>> b) for sinks, length of output queue (in bytes? Or
>>>>> boolean
>>>>> > > >>>>>>>>>>>> hasSomething/isEmpty)
>>>>> > > >>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>> a) is useful in a scenario when we are processing
>>>>> backlog of
>>>>> > > >>>>> records,
>>>>> > > >>>>>>>>> all
>>>>> > > >>>>>>>>>>>> of the internal Flink’s input/output network buffers
>>>>> are
>>>>> > > empty,
>>>>> > > >>>>> and
>>>>> > > >>>>>>> we
>>>>> > > >>>>>>>>> want
>>>>> > > >>>>>>>>>>>> to check whether the external source system is the
>>>>> > bottleneck
>>>>> > > >>>>>>> (source’s
>>>>> > > >>>>>>>>>>>> input queue will be empty), or if the Flink’s
>>>>> connector is
>>>>> > the
>>>>> > > >>>>>>>>> bottleneck
>>>>> > > >>>>>>>>>>>> (source’s input queues will be full).
>>>>> > > >>>>>>>>>>>> b) similar story. Backlog of records, but this time
>>>>> all of
>>>>> > the
>>>>> > > >>>>>>> internal
>>>>> > > >>>>>>>>>>>> Flink’s input/ouput network buffers are full, and we
>>>>> want o
>>>>> > > >> check
>>>>> > > >>>>>>>>> whether
>>>>> > > >>>>>>>>>>>> the external sink system is the bottleneck (sink
>>>>> output
>>>>> > queues
>>>>> > > >> are
>>>>> > > >>>>>>>>> full),
>>>>> > > >>>>>>>>>>>> or if the Flink’s connector is the bottleneck (sink’s
>>>>> output
>>>>> > > >>>>> queues
>>>>> > > >>>>>>>>> will be
>>>>> > > >>>>>>>>>>>> empty)
>>>>> > > >>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>> It might be sometimes difficult to provide those
>>>>> metrics, so
>>>>> > > >> they
>>>>> > > >>>>>>> could
>>>>> > > >>>>>>>>>>>> be optional, but if we could provide them, it would be
>>>>> > really
>>>>> > > >>>>>>> helpful.
>>>>> > > >>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>> Piotrek
>>>>> > > >>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>> [1]
>>>>> > > >>>>>>>>>>>>
>>>>> > > >>>>>>>>>
>>>>> > > >>>>>>>
>>>>> > > >>>>>
>>>>> > > >>
>>>>> > >
>>>>> >
>>>>> https://cwiki.apache.org/confluence/display/FLINK/FLIP-33:+Standardize+Connector+Metrics
>>>>> > > >>>>>>>>>>>> <
>>>>> > > >>>>>>>>>>>>
>>>>> > > >>>>>>>>>
>>>>> > > >>>>>>>
>>>>> > > >>>>>
>>>>> > > >>
>>>>> > >
>>>>> >
>>>>> https://cwiki.apache.org/confluence/display/FLINK/FLIP-33:+Standardize+Connector+Metrics
>>>>> > > >>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>> On 24 Apr 2019, at 13:28, Stephan Ewen <
>>>>> sewen@apache.org>
>>>>> > > >> wrote:
>>>>> > > >>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>> I think this sounds reasonable.
>>>>> > > >>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>> Let's keep the "reconfiguration without stopping the
>>>>> job"
>>>>> > out
>>>>> > > >> of
>>>>> > > >>>>>>> this,
>>>>> > > >>>>>>>>>>>>> because that would be a super big effort and if we
>>>>> approach
>>>>> > > >> that,
>>>>> > > >>>>>>> then
>>>>> > > >>>>>>>>>>>> in
>>>>> > > >>>>>>>>>>>>> more generic way rather than specific to connector
>>>>> metrics.
>>>>> > > >>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>> I would suggest to look at the following things
>>>>> before
>>>>> > > starting
>>>>> > > >>>>> with
>>>>> > > >>>>>>>>> any
>>>>> > > >>>>>>>>>>>>> implementation work:
>>>>> > > >>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>> - Try and find a committer to support this,
>>>>> otherwise it
>>>>> > will
>>>>> > > >> be
>>>>> > > >>>>>>> hard
>>>>> > > >>>>>>>>>>>> to
>>>>> > > >>>>>>>>>>>>> make progress
>>>>> > > >>>>>>>>>>>>> - Start with defining a smaller set of "core
>>>>> metrics" and
>>>>> > > >> extend
>>>>> > > >>>>> the
>>>>> > > >>>>>>>>>>>> set
>>>>> > > >>>>>>>>>>>>> later. I think that is easier than now blocking on
>>>>> reaching
>>>>> > > >>>>>>> consensus
>>>>> > > >>>>>>>>>>>> on a
>>>>> > > >>>>>>>>>>>>> large group of metrics.
>>>>> > > >>>>>>>>>>>>> - Find a solution to the problem Chesnay mentioned,
>>>>> that
>>>>> > the
>>>>> > > >>>>>>> "records
>>>>> > > >>>>>>>>>>>> in"
>>>>> > > >>>>>>>>>>>>> metric is somehow overloaded and exists already in
>>>>> the IO
>>>>> > > >> Metric
>>>>> > > >>>>>>>>> group.
>>>>> > > >>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>> On Mon, Mar 25, 2019 at 7:16 AM Becket Qin <
>>>>> > > >> becket.qin@gmail.com
>>>>> > > >>>>>>
>>>>> > > >>>>>>>>>>>> wrote:
>>>>> > > >>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>> Hi Stephan,
>>>>> > > >>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>> Thanks a lot for the feedback. All makes sense.
>>>>> > > >>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>> It is a good suggestion to simply have an
>>>>> > onRecord(numBytes,
>>>>> > > >>>>>>>>> eventTime)
>>>>> > > >>>>>>>>>>>>>> method for connector writers. It should meet most
>>>>> of the
>>>>> > > >>>>>>>>> requirements,
>>>>> > > >>>>>>>>>>>>>> individual
>>>>> > > >>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>> The configurable metrics feature is something really
>>>>> > useful,
>>>>> > > >>>>>>>>>>>> especially if
>>>>> > > >>>>>>>>>>>>>> we can somehow make it dynamically configurable
>>>>> without
>>>>> > > >> stopping
>>>>> > > >>>>>>> the
>>>>> > > >>>>>>>>>>>> jobs.
>>>>> > > >>>>>>>>>>>>>> It might be better to make it a separate discussion
>>>>> > because
>>>>> > > it
>>>>> > > >>>>> is a
>>>>> > > >>>>>>>>>>>> more
>>>>> > > >>>>>>>>>>>>>> generic feature instead of only for connectors.
>>>>> > > >>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>> So in order to make some progress, in this FLIP we
>>>>> can
>>>>> > limit
>>>>> > > >> the
>>>>> > > >>>>>>>>>>>> discussion
>>>>> > > >>>>>>>>>>>>>> scope to the connector related items:
>>>>> > > >>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>> - the standard connector metric names and types.
>>>>> > > >>>>>>>>>>>>>> - the abstract ConnectorMetricHandler interface
>>>>> > > >>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>> I'll start a separate thread to discuss other
>>>>> general
>>>>> > metric
>>>>> > > >>>>>>> related
>>>>> > > >>>>>>>>>>>>>> enhancement items including:
>>>>> > > >>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>> - optional metrics
>>>>> > > >>>>>>>>>>>>>> - dynamic metric configuration
>>>>> > > >>>>>>>>>>>>>> - potential combination with rate limiter
>>>>> > > >>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>> Does this plan sound reasonable?
>>>>> > > >>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>> Thanks,
>>>>> > > >>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>> Jiangjie (Becket) Qin
>>>>> > > >>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>> On Sat, Mar 23, 2019 at 5:53 AM Stephan Ewen <
>>>>> > > >> sewen@apache.org>
>>>>> > > >>>>>>>>> wrote:
>>>>> > > >>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>> Ignoring for a moment implementation details, this
>>>>> > > connector
>>>>> > > >>>>>>> metrics
>>>>> > > >>>>>>>>>>>> work
>>>>> > > >>>>>>>>>>>>>>> is a really good thing to do, in my opinion
>>>>> > > >>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>> The questions "oh, my job seems to be doing
>>>>> nothing, I am
>>>>> > > >>>>> looking
>>>>> > > >>>>>>> at
>>>>> > > >>>>>>>>>>>> the
>>>>> > > >>>>>>>>>>>>>> UI
>>>>> > > >>>>>>>>>>>>>>> and the 'records in' value is still zero" is in
>>>>> the top
>>>>> > > three
>>>>> > > >>>>>>>>> support
>>>>> > > >>>>>>>>>>>>>>> questions I have been asked personally.
>>>>> > > >>>>>>>>>>>>>>> Introspection into "how far is the consumer lagging
>>>>> > behind"
>>>>> > > >>>>> (event
>>>>> > > >>>>>>>>>>>> time
>>>>> > > >>>>>>>>>>>>>>> fetch latency) came up many times as well.
>>>>> > > >>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>> So big +1 to solving this problem.
>>>>> > > >>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>> About the exact design - I would try to go for the
>>>>> > > following
>>>>> > > >>>>>>>>>>>> properties:
>>>>> > > >>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>> - keep complexity of of connectors. Ideally the
>>>>> metrics
>>>>> > > >> handler
>>>>> > > >>>>>>> has
>>>>> > > >>>>>>>>> a
>>>>> > > >>>>>>>>>>>>>>> single onRecord(numBytes, eventTime) method or so,
>>>>> and
>>>>> > > >>>>> everything
>>>>> > > >>>>>>>>>>>> else is
>>>>> > > >>>>>>>>>>>>>>> internal to the handler. That makes it dead simple
>>>>> for
>>>>> > the
>>>>> > > >>>>>>>>> connector.
>>>>> > > >>>>>>>>>>>> We
>>>>> > > >>>>>>>>>>>>>>> can also think of an extensive scheme for connector
>>>>> > > specific
>>>>> > > >>>>>>>>> metrics.
>>>>> > > >>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>> - make it configurable on the job it cluster level
>>>>> which
>>>>> > > >>>>> metrics
>>>>> > > >>>>>>> the
>>>>> > > >>>>>>>>>>>>>>> handler internally creates when that method is
>>>>> invoked.
>>>>> > > >>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>> What do you think?
>>>>> > > >>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>> Best,
>>>>> > > >>>>>>>>>>>>>>> Stephan
>>>>> > > >>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>> On Thu, Mar 21, 2019 at 10:42 AM Chesnay Schepler <
>>>>> > > >>>>>>>>> chesnay@apache.org
>>>>> > > >>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>> wrote:
>>>>> > > >>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>> As I said before, I believe this to be
>>>>> over-engineered
>>>>> > and
>>>>> > > >>>>> have
>>>>> > > >>>>>>> no
>>>>> > > >>>>>>>>>>>>>>>> interest in this implementation.
>>>>> > > >>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>> There are conceptual issues like defining a
>>>>> duplicate
>>>>> > > >>>>>>>>>>>>>> numBytesIn(PerSec)
>>>>> > > >>>>>>>>>>>>>>>> metric that already exists for each operator.
>>>>> > > >>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>> On 21.03.2019 06:13, Becket Qin wrote:
>>>>> > > >>>>>>>>>>>>>>>>> A few updates to the thread. I uploaded a
>>>>> patch[1] as a
>>>>> > > >>>>> complete
>>>>> > > >>>>>>>>>>>>>>>>> example of how users can use the metrics in the
>>>>> future.
>>>>> > > >>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>> Some thoughts below after taking a look at the
>>>>> > > >>>>>>> AbstractMetricGroup
>>>>> > > >>>>>>>>>>>>>> and
>>>>> > > >>>>>>>>>>>>>>>>> its subclasses.
>>>>> > > >>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>> This patch intends to provide convenience for
>>>>> Flink
>>>>> > > >> connector
>>>>> > > >>>>>>>>>>>>>>>>> implementations to follow metrics standards
>>>>> proposed in
>>>>> > > >>>>> FLIP-33.
>>>>> > > >>>>>>>>> It
>>>>> > > >>>>>>>>>>>>>>>>> also try to enhance the metric management in
>>>>> general
>>>>> > way
>>>>> > > to
>>>>> > > >>>>> help
>>>>> > > >>>>>>>>>>>>>> users
>>>>> > > >>>>>>>>>>>>>>>>> with:
>>>>> > > >>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>> 1. metric definition
>>>>> > > >>>>>>>>>>>>>>>>> 2. metric dependencies check
>>>>> > > >>>>>>>>>>>>>>>>> 3. metric validation
>>>>> > > >>>>>>>>>>>>>>>>> 4. metric control (turn on / off particular
>>>>> metrics)
>>>>> > > >>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>> This patch wraps |MetricGroup| to extend the
>>>>> > > functionality
>>>>> > > >> of
>>>>> > > >>>>>>>>>>>>>>>>> |AbstractMetricGroup| and its subclasses. The
>>>>> > > >>>>>>>>>>>>>>>>> |AbstractMetricGroup| mainly focus on the metric
>>>>> group
>>>>> > > >>>>>>> hierarchy,
>>>>> > > >>>>>>>>>>>> but
>>>>> > > >>>>>>>>>>>>>>>>> does not really manage the metrics other than
>>>>> keeping
>>>>> > > them
>>>>> > > >>>>> in a
>>>>> > > >>>>>>>>> Map.
>>>>> > > >>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>> Ideally we should only have one entry point for
>>>>> the
>>>>> > > >> metrics.
>>>>> > > >>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>> Right now the entry point is
>>>>> |AbstractMetricGroup|.
>>>>> > > >> However,
>>>>> > > >>>>>>>>> besides
>>>>> > > >>>>>>>>>>>>>>>>> the missing functionality mentioned above,
>>>>> > > >>>>> |AbstractMetricGroup|
>>>>> > > >>>>>>>>>>>>>> seems
>>>>> > > >>>>>>>>>>>>>>>>> deeply rooted in Flink runtime. We could extract
>>>>> it out
>>>>> > > to
>>>>> > > >>>>>>>>>>>>>>>>> flink-metrics in order to use it for generic
>>>>> purpose.
>>>>> > > There
>>>>> > > >>>>> will
>>>>> > > >>>>>>>>> be
>>>>> > > >>>>>>>>>>>>>>>>> some work, though.
>>>>> > > >>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>> Another approach is to make |AbstractMetrics| in
>>>>> this
>>>>> > > patch
>>>>> > > >>>>> as
>>>>> > > >>>>>>> the
>>>>> > > >>>>>>>>>>>>>>>>> metric entry point. It wraps metric group and
>>>>> provides
>>>>> > > the
>>>>> > > >>>>>>> missing
>>>>> > > >>>>>>>>>>>>>>>>> functionalities. Then we can roll out this
>>>>> pattern to
>>>>> > > >> runtime
>>>>> > > >>>>>>>>>>>>>>>>> components gradually as well.
>>>>> > > >>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>> My first thought is that the latter approach
>>>>> gives a
>>>>> > more
>>>>> > > >>>>> smooth
>>>>> > > >>>>>>>>>>>>>>>>> migration. But I am also OK with doing a
>>>>> refactoring on
>>>>> > > the
>>>>> > > >>>>>>>>>>>>>>>>> |AbstractMetricGroup| family.
>>>>> > > >>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>> Thanks,
>>>>> > > >>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>> Jiangjie (Becket) Qin
>>>>> > > >>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>> [1] https://github.com/becketqin/flink/pull/1
>>>>> > > >>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>> On Mon, Feb 25, 2019 at 2:32 PM Becket Qin <
>>>>> > > >>>>>>> becket.qin@gmail.com
>>>>> > > >>>>>>>>>>>>>>>>> <ma...@gmail.com>> wrote:
>>>>> > > >>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>> Hi Chesnay,
>>>>> > > >>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>> It might be easier to discuss some implementation
>>>>> > details
>>>>> > > >> in
>>>>> > > >>>>>>> the
>>>>> > > >>>>>>>>>>>>>>>>> PR review instead of in the FLIP discussion
>>>>> thread. I
>>>>> > > have
>>>>> > > >> a
>>>>> > > >>>>>>>>>>>>>> patch
>>>>> > > >>>>>>>>>>>>>>>>> for Kafka connectors ready but haven't submitted
>>>>> the PR
>>>>> > > >> yet.
>>>>> > > >>>>>>>>>>>>>>>>> Hopefully that will help explain a bit more.
>>>>> > > >>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>> ** Re: metric type binding
>>>>> > > >>>>>>>>>>>>>>>>> This is a valid point that worths discussing. If
>>>>> I
>>>>> > > >> understand
>>>>> > > >>>>>>>>>>>>>>>>> correctly, there are two points:
>>>>> > > >>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>> 1. Metric type / interface does not matter as
>>>>> long as
>>>>> > the
>>>>> > > >>>>>>> metric
>>>>> > > >>>>>>>>>>>>>>>>> semantic is clearly defined.
>>>>> > > >>>>>>>>>>>>>>>>> Conceptually speaking, I agree that as long as
>>>>> the
>>>>> > metric
>>>>> > > >>>>>>>>>>>>>> semantic
>>>>> > > >>>>>>>>>>>>>>>>> is defined, metric type does not matter. To some
>>>>> > extent,
>>>>> > > >>>>> Gauge
>>>>> > > >>>>>>> /
>>>>> > > >>>>>>>>>>>>>>>>> Counter / Meter / Histogram themselves can be
>>>>> think of
>>>>> > as
>>>>> > > >>>>> some
>>>>> > > >>>>>>>>>>>>>>>>> well-recognized semantics, if you wish. In
>>>>> Flink, these
>>>>> > > >>>>> metric
>>>>> > > >>>>>>>>>>>>>>>>> semantics have their associated interface
>>>>> classes. In
>>>>> > > >>>>> practice,
>>>>> > > >>>>>>>>>>>>>>>>> such semantic to interface binding seems
>>>>> necessary for
>>>>> > > >>>>>>> different
>>>>> > > >>>>>>>>>>>>>>>>> components to communicate. Simply standardize
>>>>> the
>>>>> > > semantic
>>>>> > > >>>>> of
>>>>> > > >>>>>>>>>>>>>> the
>>>>> > > >>>>>>>>>>>>>>>>> connector metrics seems not sufficient for
>>>>> people to
>>>>> > > build
>>>>> > > >>>>>>>>>>>>>>>>> ecosystem on top of. At the end of the day, we
>>>>> still
>>>>> > need
>>>>> > > >> to
>>>>> > > >>>>>>>>> have
>>>>> > > >>>>>>>>>>>>>>>>> some embodiment of the metric semantics that
>>>>> people can
>>>>> > > >>>>> program
>>>>> > > >>>>>>>>>>>>>>>>> against.
>>>>> > > >>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>> 2. Sometimes the same metric semantic can be
>>>>> exposed
>>>>> > > using
>>>>> > > >>>>>>>>>>>>>>>>> different metric types / interfaces.
>>>>> > > >>>>>>>>>>>>>>>>> This is a good point. Counter and
>>>>> Gauge-as-a-Counter
>>>>> > are
>>>>> > > >>>>> pretty
>>>>> > > >>>>>>>>>>>>>>>>> much interchangeable. This is more of a trade-off
>>>>> > between
>>>>> > > >> the
>>>>> > > >>>>>>>>>>>>>> user
>>>>> > > >>>>>>>>>>>>>>>>> experience of metric producers and consumers. The
>>>>> > metric
>>>>> > > >>>>>>>>>>>>>> producers
>>>>> > > >>>>>>>>>>>>>>>>> want to use Counter or Gauge depending on
>>>>> whether the
>>>>> > > >> counter
>>>>> > > >>>>>>> is
>>>>> > > >>>>>>>>>>>>>>>>> already tracked in code, while ideally the metric
>>>>> > > consumers
>>>>> > > >>>>>>> only
>>>>> > > >>>>>>>>>>>>>>>>> want to see a single metric type for each
>>>>> metric. I am
>>>>> > > >>>>> leaning
>>>>> > > >>>>>>>>>>>>>>>>> towards to make the metric producers happy, i.e.
>>>>> allow
>>>>> > > >> Gauge
>>>>> > > >>>>> /
>>>>> > > >>>>>>>>>>>>>>>>> Counter metric type, and the the metric consumers
>>>>> > handle
>>>>> > > >> the
>>>>> > > >>>>>>>>> type
>>>>> > > >>>>>>>>>>>>>>>>> variation. The reason is that in practice, there
>>>>> might
>>>>> > be
>>>>> > > >>>>> more
>>>>> > > >>>>>>>>>>>>>>>>> connector implementations than metric reporter
>>>>> > > >>>>> implementations.
>>>>> > > >>>>>>>>>>>>>> We
>>>>> > > >>>>>>>>>>>>>>>>> could also provide some helper method to
>>>>> facilitate
>>>>> > > reading
>>>>> > > >>>>>>> from
>>>>> > > >>>>>>>>>>>>>>>>> such variable metric type.
>>>>> > > >>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>> Just some quick replies to the comments around
>>>>> > > >> implementation
>>>>> > > >>>>>>>>>>>>>>>> details.
>>>>> > > >>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>> 4) single place where metrics are registered
>>>>> except
>>>>> > > >>>>>>>>>>>>>>>>> connector-specific
>>>>> > > >>>>>>>>>>>>>>>>> ones (which we can't really avoid).
>>>>> > > >>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>> Register connector specific ones in a single
>>>>> place is
>>>>> > > >>>>> actually
>>>>> > > >>>>>>>>>>>>>>>>> something that I want to achieve.
>>>>> > > >>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>> 2) I'm talking about time-series databases like
>>>>> > > >>>>> Prometheus.
>>>>> > > >>>>>>>>>>>>>> We
>>>>> > > >>>>>>>>>>>>>>>>> would
>>>>> > > >>>>>>>>>>>>>>>>> only have a gauge metric exposing the last
>>>>> > > >>>>>>>>> fetchTime/emitTime
>>>>> > > >>>>>>>>>>>>>>>>> that is
>>>>> > > >>>>>>>>>>>>>>>>> regularly reported to the backend (Prometheus),
>>>>> > where a
>>>>> > > >>>>>>> user
>>>>> > > >>>>>>>>>>>>>>>>> could build
>>>>> > > >>>>>>>>>>>>>>>>> a histogram of his choosing when/if he wants
>>>>> it.
>>>>> > > >>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>> Not sure if such downsampling works. As an
>>>>> example, if
>>>>> > a
>>>>> > > >> user
>>>>> > > >>>>>>>>>>>>>>>>> complains that there are some intermittent
>>>>> latency
>>>>> > spikes
>>>>> > > >>>>>>> (maybe
>>>>> > > >>>>>>>>>>>>>> a
>>>>> > > >>>>>>>>>>>>>>>>> few records in 10 seconds) in their processing
>>>>> system.
>>>>> > > >>>>> Having a
>>>>> > > >>>>>>>>>>>>>>>>> Gauge sampling instantaneous latency seems
>>>>> unlikely
>>>>> > > useful.
>>>>> > > >>>>>>>>>>>>>>>>> However by looking at actual 99.9 percentile
>>>>> latency
>>>>> > > might
>>>>> > > >>>>>>> help.
>>>>> > > >>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>> Thanks,
>>>>> > > >>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>> Jiangjie (Becket) Qin
>>>>> > > >>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>> On Fri, Feb 22, 2019 at 9:30 PM Chesnay Schepler
>>>>> > > >>>>>>>>>>>>>>>>> <chesnay@apache.org <ma...@apache.org>>
>>>>> > wrote:
>>>>> > > >>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>> Re: over complication of implementation.
>>>>> > > >>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>> I think I get understand better know what
>>>>> you're
>>>>> > > >> shooting
>>>>> > > >>>>>>>>>>>>>> for,
>>>>> > > >>>>>>>>>>>>>>>>> effectively something like the
>>>>> OperatorIOMetricGroup.
>>>>> > > >>>>>>>>>>>>>>>>> But still, re-define setupConnectorMetrics() to
>>>>> > accept
>>>>> > > a
>>>>> > > >>>>>>> set
>>>>> > > >>>>>>>>>>>>>>>>> of flags
>>>>> > > >>>>>>>>>>>>>>>>> for counters/meters(ans _possibly_ histograms)
>>>>> along
>>>>> > > >>>>> with a
>>>>> > > >>>>>>>>>>>>>>>>> set of
>>>>> > > >>>>>>>>>>>>>>>>> well-defined Optional<Gauge<?>>, and return the
>>>>> > group.
>>>>> > > >>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>> Solves all issues as far as i can tell:
>>>>> > > >>>>>>>>>>>>>>>>> 1) no metrics must be created manually (except
>>>>> > Gauges,
>>>>> > > >>>>>>> which
>>>>> > > >>>>>>>>>>>>>>> are
>>>>> > > >>>>>>>>>>>>>>>>> effectively just Suppliers and you can't get
>>>>> around
>>>>> > > >>>>> this),
>>>>> > > >>>>>>>>>>>>>>>>> 2) additional metrics can be registered on the
>>>>> > returned
>>>>> > > >>>>>>>>>>>>>> group,
>>>>> > > >>>>>>>>>>>>>>>>> 3) see 1),
>>>>> > > >>>>>>>>>>>>>>>>> 4) single place where metrics are registered
>>>>> except
>>>>> > > >>>>>>>>>>>>>>>>> connector-specific
>>>>> > > >>>>>>>>>>>>>>>>> ones (which we can't really avoid).
>>>>> > > >>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>> Re: Histogram
>>>>> > > >>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>> 1) As an example, whether "numRecordsIn" is
>>>>> exposed
>>>>> > as
>>>>> > > a
>>>>> > > >>>>>>>>>>>>>>>>> Counter or a
>>>>> > > >>>>>>>>>>>>>>>>> Gauge should be irrelevant. So far we're using
>>>>> the
>>>>> > > >> metric
>>>>> > > >>>>>>>>>>>>>> type
>>>>> > > >>>>>>>>>>>>>>>>> that is
>>>>> > > >>>>>>>>>>>>>>>>> the most convenient at exposing a given value.
>>>>> If
>>>>> > there
>>>>> > > >>>>> is
>>>>> > > >>>>>>>>>>>>>>>>> some backing
>>>>> > > >>>>>>>>>>>>>>>>> data-structure that we want to expose some
>>>>> data from
>>>>> > we
>>>>> > > >>>>>>>>>>>>>>>>> typically opt
>>>>> > > >>>>>>>>>>>>>>>>> for a Gauge, as otherwise we're just mucking
>>>>> around
>>>>> > > with
>>>>> > > >>>>>>> the
>>>>> > > >>>>>>>>>>>>>>>>> Meter/Counter API to get it to match.
>>>>> Similarly, if
>>>>> > we
>>>>> > > >>>>> want
>>>>> > > >>>>>>>>>>>>>> to
>>>>> > > >>>>>>>>>>>>>>>>> count
>>>>> > > >>>>>>>>>>>>>>>>> something but no current count exists we
>>>>> typically
>>>>> > > added
>>>>> > > >>>>> a
>>>>> > > >>>>>>>>>>>>>>>>> Counter.
>>>>> > > >>>>>>>>>>>>>>>>> That's why attaching semantics to metric types
>>>>> makes
>>>>> > > >>>>> little
>>>>> > > >>>>>>>>>>>>>>>>> sense (but
>>>>> > > >>>>>>>>>>>>>>>>> unfortunately several reporters already do
>>>>> it); for
>>>>> > > >>>>>>>>>>>>>>>>> counters/meters
>>>>> > > >>>>>>>>>>>>>>>>> certainly, but the majority of metrics are
>>>>> gauges.
>>>>> > > >>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>> 2) I'm talking about time-series databases like
>>>>> > > >>>>> Prometheus.
>>>>> > > >>>>>>>>>>>>>> We
>>>>> > > >>>>>>>>>>>>>>>>> would
>>>>> > > >>>>>>>>>>>>>>>>> only have a gauge metric exposing the last
>>>>> > > >>>>>>>>> fetchTime/emitTime
>>>>> > > >>>>>>>>>>>>>>>>> that is
>>>>> > > >>>>>>>>>>>>>>>>> regularly reported to the backend (Prometheus),
>>>>> > where a
>>>>> > > >>>>>>> user
>>>>> > > >>>>>>>>>>>>>>>>> could build
>>>>> > > >>>>>>>>>>>>>>>>> a histogram of his choosing when/if he wants
>>>>> it.
>>>>> > > >>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>> On 22.02.2019 13:57, Becket Qin wrote:
>>>>> > > >>>>>>>>>>>>>>>>>> Hi Chesnay,
>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>>> Thanks for the explanation.
>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>>> ** Re: FLIP
>>>>> > > >>>>>>>>>>>>>>>>>> I might have misunderstood this, but it seems
>>>>> that
>>>>> > > "major
>>>>> > > >>>>>>>>>>>>>>>>> changes" are well
>>>>> > > >>>>>>>>>>>>>>>>>> defined in FLIP. The full contents is following:
>>>>> > > >>>>>>>>>>>>>>>>>> What is considered a "major change" that needs
>>>>> a FLIP?
>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>>> Any of the following should be considered a
>>>>> major
>>>>> > > change:
>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>>> - Any major new feature, subsystem, or piece of
>>>>> > > >>>>>>>>>>>>>>>>> functionality
>>>>> > > >>>>>>>>>>>>>>>>>> - *Any change that impacts the public
>>>>> interfaces of
>>>>> > the
>>>>> > > >>>>>>>>>>>>>>>>> project*
>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>>> What are the "public interfaces" of the project?
>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>>> *All of the following are public interfaces
>>>>> *that
>>>>> > people
>>>>> > > >>>>>>>>>>>>>>>>> build around:
>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>>> - DataStream and DataSet API, including classes
>>>>> > related
>>>>> > > >>>>>>>>>>>>>>>>> to that, such as
>>>>> > > >>>>>>>>>>>>>>>>>> StreamExecutionEnvironment
>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>>> - Classes marked with the @Public annotation
>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>>> - On-disk binary formats, such as
>>>>> > > >>>>>>>>>>>>>> checkpoints/savepoints
>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>>> - User-facing scripts/command-line tools, i.e.
>>>>> > > >>>>>>>>>>>>>>>>> bin/flink, Yarn scripts,
>>>>> > > >>>>>>>>>>>>>>>>>> Mesos scripts
>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>>> - Configuration settings
>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>>> - *Exposed monitoring information*
>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>>> So any monitoring information change is
>>>>> considered as
>>>>> > > >>>>>>>>>>>>>> public
>>>>> > > >>>>>>>>>>>>>>>>> interface, and
>>>>> > > >>>>>>>>>>>>>>>>>> any public interface change is considered as a
>>>>> "major
>>>>> > > >>>>>>>>>>>>>>> change".
>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>>> ** Re: over complication of implementation.
>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>>> Although this is more of implementation details
>>>>> that
>>>>> > is
>>>>> > > >> not
>>>>> > > >>>>>>>>>>>>>>>>> covered by the
>>>>> > > >>>>>>>>>>>>>>>>>> FLIP. But it may be worth discussing.
>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>>> First of all, I completely agree that we should
>>>>> use
>>>>> > the
>>>>> > > >>>>>>>>>>>>>>>>> simplest way to
>>>>> > > >>>>>>>>>>>>>>>>>> achieve our goal. To me the goal is the
>>>>> following:
>>>>> > > >>>>>>>>>>>>>>>>>> 1. Clear connector conventions and interfaces.
>>>>> > > >>>>>>>>>>>>>>>>>> 2. The easiness of creating a connector.
>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>>> Both of them are important to the prosperity of
>>>>> the
>>>>> > > >>>>>>>>>>>>>>>>> connector ecosystem. So
>>>>> > > >>>>>>>>>>>>>>>>>> I'd rather abstract as much as possible on our
>>>>> side to
>>>>> > > >> make
>>>>> > > >>>>>>>>>>>>>>>>> the connector
>>>>> > > >>>>>>>>>>>>>>>>>> developer's work lighter. Given this goal, a
>>>>> static
>>>>> > util
>>>>> > > >>>>>>>>>>>>>>>>> method approach
>>>>> > > >>>>>>>>>>>>>>>>>> might have a few drawbacks:
>>>>> > > >>>>>>>>>>>>>>>>>> 1. Users still have to construct the metrics by
>>>>> > > >> themselves.
>>>>> > > >>>>>>>>>>>>>>>>> (And note that
>>>>> > > >>>>>>>>>>>>>>>>>> this might be erroneous by itself. For example,
>>>>> a
>>>>> > > customer
>>>>> > > >>>>>>>>>>>>>>>>> wrapper around
>>>>> > > >>>>>>>>>>>>>>>>>> dropwizard meter maybe used instead of
>>>>> MeterView).
>>>>> > > >>>>>>>>>>>>>>>>>> 2. When connector specific metrics are added,
>>>>> it is
>>>>> > > >>>>>>>>>>>>>>>>> difficult to enforce
>>>>> > > >>>>>>>>>>>>>>>>>> the scope to be the same as standard metrics.
>>>>> > > >>>>>>>>>>>>>>>>>> 3. It seems that a method proliferation is
>>>>> inevitable
>>>>> > if
>>>>> > > >> we
>>>>> > > >>>>>>>>>>>>>>>>> want to apply
>>>>> > > >>>>>>>>>>>>>>>>>> sanity checks. e.g. The metric of numBytesIn
>>>>> was not
>>>>> > > >>>>>>>>>>>>>>>>> registered for a meter.
>>>>> > > >>>>>>>>>>>>>>>>>> 4. Metrics are still defined in random places
>>>>> and hard
>>>>> > > to
>>>>> > > >>>>>>>>>>>>>>>> track.
>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>>> The current PR I had was inspired by the Config
>>>>> system
>>>>> > > in
>>>>> > > >>>>>>>>>>>>>>>>> Kafka, which I
>>>>> > > >>>>>>>>>>>>>>>>>> found pretty handy. In fact it is not only used
>>>>> by
>>>>> > Kafka
>>>>> > > >>>>>>>>>>>>>>>>> itself but even
>>>>> > > >>>>>>>>>>>>>>>>>> some other projects that depend on Kafka. I am
>>>>> not
>>>>> > > saying
>>>>> > > >>>>>>>>>>>>>>>>> this approach is
>>>>> > > >>>>>>>>>>>>>>>>>> perfect. But I think it worths to save the work
>>>>> for
>>>>> > > >>>>>>>>>>>>>>>>> connector writers and
>>>>> > > >>>>>>>>>>>>>>>>>> encourage more systematic implementation. That
>>>>> being
>>>>> > > said,
>>>>> > > >>>>>>>>>>>>>> I
>>>>> > > >>>>>>>>>>>>>>>>> am fully open
>>>>> > > >>>>>>>>>>>>>>>>>> to suggestions.
>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>>> Re: Histogram
>>>>> > > >>>>>>>>>>>>>>>>>> I think there are two orthogonal questions
>>>>> around
>>>>> > those
>>>>> > > >>>>>>>>>>>>>>>> metrics:
>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>>> 1. Regardless of the metric type, by just
>>>>> looking at
>>>>> > the
>>>>> > > >>>>>>>>>>>>>>>>> meaning of a
>>>>> > > >>>>>>>>>>>>>>>>>> metric, is generic to all connectors? If the
>>>>> answer is
>>>>> > > >> yes,
>>>>> > > >>>>>>>>>>>>>>>>> we should
>>>>> > > >>>>>>>>>>>>>>>>>> include the metric into the convention. No
>>>>> matter
>>>>> > > whether
>>>>> > > >>>>>>>>>>>>>> we
>>>>> > > >>>>>>>>>>>>>>>>> include it
>>>>> > > >>>>>>>>>>>>>>>>>> into the convention or not, some connector
>>>>> > > implementations
>>>>> > > >>>>>>>>>>>>>>>>> will emit such
>>>>> > > >>>>>>>>>>>>>>>>>> metric. It is better to have a convention than
>>>>> letting
>>>>> > > >> each
>>>>> > > >>>>>>>>>>>>>>>>> connector do
>>>>> > > >>>>>>>>>>>>>>>>>> random things.
>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>>> 2. If a standard metric is a histogram, what
>>>>> should we
>>>>> > > do?
>>>>> > > >>>>>>>>>>>>>>>>>> I agree that we should make it clear that using
>>>>> > > histograms
>>>>> > > >>>>>>>>>>>>>>>>> will have
>>>>> > > >>>>>>>>>>>>>>>>>> performance risk. But I do see histogram is
>>>>> useful in
>>>>> > > some
>>>>> > > >>>>>>>>>>>>>>>>> fine-granularity
>>>>> > > >>>>>>>>>>>>>>>>>> debugging where one do not have the luxury to
>>>>> stop the
>>>>> > > >>>>>>>>>>>>>>>>> system and inject
>>>>> > > >>>>>>>>>>>>>>>>>> more inspection code. So the workaround I am
>>>>> thinking
>>>>> > is
>>>>> > > >> to
>>>>> > > >>>>>>>>>>>>>>>>> provide some
>>>>> > > >>>>>>>>>>>>>>>>>> implementation suggestions. Assume later on we
>>>>> have a
>>>>> > > >>>>>>>>>>>>>>>>> mechanism of
>>>>> > > >>>>>>>>>>>>>>>>>> selective metrics. In the abstract metrics
>>>>> class we
>>>>> > can
>>>>> > > >>>>>>>>>>>>>>>>> disable those
>>>>> > > >>>>>>>>>>>>>>>>>> metrics by default individual connector writers
>>>>> does
>>>>> > not
>>>>> > > >>>>>>>>>>>>>>>>> have to do
>>>>> > > >>>>>>>>>>>>>>>>>> anything (this is another advantage of having an
>>>>> > > >>>>>>>>>>>>>>>>> AbstractMetrics instead of
>>>>> > > >>>>>>>>>>>>>>>>>> static util methods.)
>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>>> I am not sure I fully understand the histogram
>>>>> in the
>>>>> > > >>>>>>>>>>>>>>>>> backend approach. Can
>>>>> > > >>>>>>>>>>>>>>>>>> you explain a bit more? Do you mean emitting
>>>>> the raw
>>>>> > > data,
>>>>> > > >>>>>>>>>>>>>>>>> e.g. fetchTime
>>>>> > > >>>>>>>>>>>>>>>>>> and emitTime with each record and let the
>>>>> histogram
>>>>> > > >>>>>>>>>>>>>>>>> computation happen in
>>>>> > > >>>>>>>>>>>>>>>>>> the background? Or let the processing thread
>>>>> putting
>>>>> > the
>>>>> > > >>>>>>>>>>>>>>>>> values into a
>>>>> > > >>>>>>>>>>>>>>>>>> queue and have a separate thread polling from
>>>>> the
>>>>> > queue
>>>>> > > >> and
>>>>> > > >>>>>>>>>>>>>>>>> add them into
>>>>> > > >>>>>>>>>>>>>>>>>> the histogram?
>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>>> Thanks,
>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>>> Jiangjie (Becket) Qin
>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>>> On Fri, Feb 22, 2019 at 4:34 PM Chesnay Schepler
>>>>> > > >>>>>>>>>>>>>>>>> <chesnay@apache.org <mailto:chesnay@apache.org
>>>>> >>
>>>>> > > wrote:
>>>>> > > >>>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>>>> Re: Flip
>>>>> > > >>>>>>>>>>>>>>>>>>> The very first line under both the main header
>>>>> and
>>>>> > > >> Purpose
>>>>> > > >>>>>>>>>>>>>>>>> section
>>>>> > > >>>>>>>>>>>>>>>>>>> describe Flips as "major changes", which this
>>>>> isn't.
>>>>> > > >>>>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>>>> Re: complication
>>>>> > > >>>>>>>>>>>>>>>>>>> I'm not arguing against standardization, but
>>>>> again an
>>>>> > > >>>>>>>>>>>>>>>>> over-complicated
>>>>> > > >>>>>>>>>>>>>>>>>>> implementation when a static utility method
>>>>> would be
>>>>> > > >>>>>>>>>>>>>>>>> sufficient.
>>>>> > > >>>>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>>>> public static void setupConnectorMetrics(
>>>>> > > >>>>>>>>>>>>>>>>>>> MetricGroup operatorMetricGroup,
>>>>> > > >>>>>>>>>>>>>>>>>>> String connectorName,
>>>>> > > >>>>>>>>>>>>>>>>>>> Optional<Gauge<Long>> numRecordsIn,
>>>>> > > >>>>>>>>>>>>>>>>>>> ...)
>>>>> > > >>>>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>>>> This gives you all you need:
>>>>> > > >>>>>>>>>>>>>>>>>>> * a well-defined set of metrics for a
>>>>> connector to
>>>>> > > opt-in
>>>>> > > >>>>>>>>>>>>>>>>>>> * standardized naming schemes for scope and
>>>>> > individual
>>>>> > > >>>>>>>>>>>>>>> metrics
>>>>> > > >>>>>>>>>>>>>>>>>>> * standardize metric types (although
>>>>> personally I'm
>>>>> > not
>>>>> > > >>>>>>>>>>>>>>>>> interested in that
>>>>> > > >>>>>>>>>>>>>>>>>>> since metric types should be considered
>>>>> syntactic
>>>>> > > sugar)
>>>>> > > >>>>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>>>> Re: Configurable Histogram
>>>>> > > >>>>>>>>>>>>>>>>>>> If anything they _must_ be turned off by
>>>>> default, but
>>>>> > > the
>>>>> > > >>>>>>>>>>>>>>>>> metric system is
>>>>> > > >>>>>>>>>>>>>>>>>>> already exposing so many options that I'm not
>>>>> too
>>>>> > keen
>>>>> > > on
>>>>> > > >>>>>>>>>>>>>>>>> adding even more.
>>>>> > > >>>>>>>>>>>>>>>>>>> You have also only addressed my first argument
>>>>> > against
>>>>> > > >>>>>>>>>>>>>>>>> histograms
>>>>> > > >>>>>>>>>>>>>>>>>>> (performance), the second one still stands
>>>>> (calculate
>>>>> > > >>>>>>>>>>>>>>>>> histogram in metric
>>>>> > > >>>>>>>>>>>>>>>>>>> backends instead).
>>>>> > > >>>>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>>>> On 21.02.2019 16:27, Becket Qin wrote:
>>>>> > > >>>>>>>>>>>>>>>>>>>> Hi Chesnay,
>>>>> > > >>>>>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>>>>> Thanks for the comments. I think this is
>>>>> worthy of a
>>>>> > > >> FLIP
>>>>> > > >>>>>>>>>>>>>>>>> because it is
>>>>> > > >>>>>>>>>>>>>>>>>>>> public API. According to the FLIP description
>>>>> a FlIP
>>>>> > > is
>>>>> > > >>>>>>>>>>>>>>>>> required in case
>>>>> > > >>>>>>>>>>>>>>>>>>> of:
>>>>> > > >>>>>>>>>>>>>>>>>>>> - Any change that impacts the public
>>>>> interfaces of
>>>>> > > >>>>>>>>>>>>>>>>> the project
>>>>> > > >>>>>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>>>>> and the following entry is found in the
>>>>> definition
>>>>> > of
>>>>> > > >>>>>>>>>>>>>>>>> "public interface".
>>>>> > > >>>>>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>>>>> - Exposed monitoring information
>>>>> > > >>>>>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>>>>> Metrics are critical to any production
>>>>> system. So a
>>>>> > > >> clear
>>>>> > > >>>>>>>>>>>>>>>>> metric
>>>>> > > >>>>>>>>>>>>>>>>>>> definition
>>>>> > > >>>>>>>>>>>>>>>>>>>> is important for any serious users. For an
>>>>> > > organization
>>>>> > > >>>>>>>>>>>>>>>>> with large Flink
>>>>> > > >>>>>>>>>>>>>>>>>>>> installation, change in metrics means great
>>>>> amount
>>>>> > of
>>>>> > > >>>>>>>>>>>>>>>>> work. So such
>>>>> > > >>>>>>>>>>>>>>>>>>> changes
>>>>> > > >>>>>>>>>>>>>>>>>>>> do need to be fully discussed and documented.
>>>>> > > >>>>>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>>>>> ** Re: Histogram.
>>>>> > > >>>>>>>>>>>>>>>>>>>> We can discuss whether there is a better way
>>>>> to
>>>>> > expose
>>>>> > > >>>>>>>>>>>>>>>>> metrics that are
>>>>> > > >>>>>>>>>>>>>>>>>>>> suitable for histograms. My micro-benchmark on
>>>>> > various
>>>>> > > >>>>>>>>>>>>>>>>> histogram
>>>>> > > >>>>>>>>>>>>>>>>>>>> implementations also indicates that they are
>>>>> > > >>>>>>>>>>>>>> significantly
>>>>> > > >>>>>>>>>>>>>>>>> slower than
>>>>> > > >>>>>>>>>>>>>>>>>>>> other metric types. But I don't think that
>>>>> means
>>>>> > never
>>>>> > > >>>>>>>>>>>>>> use
>>>>> > > >>>>>>>>>>>>>>>>> histogram, but
>>>>> > > >>>>>>>>>>>>>>>>>>>> means use it with caution. For example, we can
>>>>> > suggest
>>>>> > > >>>>>>>>>>>>>> the
>>>>> > > >>>>>>>>>>>>>>>>>>> implementations
>>>>> > > >>>>>>>>>>>>>>>>>>>> to turn them off by default and only turn it
>>>>> on for
>>>>> > a
>>>>> > > >>>>>>>>>>>>>>>>> small amount of
>>>>> > > >>>>>>>>>>>>>>>>>>> time
>>>>> > > >>>>>>>>>>>>>>>>>>>> when performing some micro-debugging.
>>>>> > > >>>>>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>>>>> ** Re: complication:
>>>>> > > >>>>>>>>>>>>>>>>>>>> Connector conventions are essential for Flink
>>>>> > > ecosystem.
>>>>> > > >>>>>>>>>>>>>>>>> Flink connectors
>>>>> > > >>>>>>>>>>>>>>>>>>>> pool is probably the most important part of
>>>>> Flink,
>>>>> > > just
>>>>> > > >>>>>>>>>>>>>>>>> like any other
>>>>> > > >>>>>>>>>>>>>>>>>>> data
>>>>> > > >>>>>>>>>>>>>>>>>>>> system. Clear conventions of connectors will
>>>>> help
>>>>> > > build
>>>>> > > >>>>>>>>>>>>>>>>> Flink ecosystem
>>>>> > > >>>>>>>>>>>>>>>>>>> in
>>>>> > > >>>>>>>>>>>>>>>>>>>> a more organic way.
>>>>> > > >>>>>>>>>>>>>>>>>>>> Take the metrics convention as an example,
>>>>> imagine
>>>>> > > >>>>>>>>>>>>>> someone
>>>>> > > >>>>>>>>>>>>>>>>> has developed
>>>>> > > >>>>>>>>>>>>>>>>>>> a
>>>>> > > >>>>>>>>>>>>>>>>>>>> Flink connector for System foo, and another
>>>>> > developer
>>>>> > > >> may
>>>>> > > >>>>>>>>>>>>>>>>> have developed
>>>>> > > >>>>>>>>>>>>>>>>>>> a
>>>>> > > >>>>>>>>>>>>>>>>>>>> monitoring and diagnostic framework for Flink
>>>>> which
>>>>> > > >>>>>>>>>>>>>>>>> analyzes the Flink
>>>>> > > >>>>>>>>>>>>>>>>>>> job
>>>>> > > >>>>>>>>>>>>>>>>>>>> performance based on metrics. With a clear
>>>>> metric
>>>>> > > >>>>>>>>>>>>>>>>> convention, those two
>>>>> > > >>>>>>>>>>>>>>>>>>>> projects could be developed independently.
>>>>> Once
>>>>> > users
>>>>> > > >> put
>>>>> > > >>>>>>>>>>>>>>>>> them together,
>>>>> > > >>>>>>>>>>>>>>>>>>>> it would work without additional
>>>>> modifications. This
>>>>> > > >>>>>>>>>>>>>>>>> cannot be easily
>>>>> > > >>>>>>>>>>>>>>>>>>>> achieved by just defining a few constants.
>>>>> > > >>>>>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>>>>> ** Re: selective metrics:
>>>>> > > >>>>>>>>>>>>>>>>>>>> Sure, we can discuss that in a separate
>>>>> thread.
>>>>> > > >>>>>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>>>>> @Dawid
>>>>> > > >>>>>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>>>>> ** Re: latency / fetchedLatency
>>>>> > > >>>>>>>>>>>>>>>>>>>> The primary purpose of establish such a
>>>>> convention
>>>>> > is
>>>>> > > to
>>>>> > > >>>>>>>>>>>>>>>>> help developers
>>>>> > > >>>>>>>>>>>>>>>>>>>> write connectors in a more compatible way. The
>>>>> > > >> convention
>>>>> > > >>>>>>>>>>>>>>>>> is supposed to
>>>>> > > >>>>>>>>>>>>>>>>>>> be
>>>>> > > >>>>>>>>>>>>>>>>>>>> defined more proactively. So when look at the
>>>>> > > >> convention,
>>>>> > > >>>>>>>>>>>>>>>>> it seems more
>>>>> > > >>>>>>>>>>>>>>>>>>>> important to see if the concept is applicable
>>>>> to
>>>>> > > >>>>>>>>>>>>>>>>> connectors in general.
>>>>> > > >>>>>>>>>>>>>>>>>>> It
>>>>> > > >>>>>>>>>>>>>>>>>>>> might be true so far only Kafka connector
>>>>> reports
>>>>> > > >>>>>>>>>>>>>> latency.
>>>>> > > >>>>>>>>>>>>>>>>> But there
>>>>> > > >>>>>>>>>>>>>>>>>>> might
>>>>> > > >>>>>>>>>>>>>>>>>>>> be hundreds of other connector
>>>>> implementations in
>>>>> > the
>>>>> > > >>>>>>>>>>>>>>>>> Flink ecosystem,
>>>>> > > >>>>>>>>>>>>>>>>>>>> though not in the Flink repo, and some of
>>>>> them also
>>>>> > > >> emits
>>>>> > > >>>>>>>>>>>>>>>>> latency. I
>>>>> > > >>>>>>>>>>>>>>>>>>> think
>>>>> > > >>>>>>>>>>>>>>>>>>>> a lot of other sources actually also has an
>>>>> append
>>>>> > > >>>>>>>>>>>>>>>>> timestamp. e.g.
>>>>> > > >>>>>>>>>>>>>>>>>>> database
>>>>> > > >>>>>>>>>>>>>>>>>>>> bin logs and some K-V stores. So I wouldn't be
>>>>> > > surprised
>>>>> > > >>>>>>>>>>>>>>>>> if some database
>>>>> > > >>>>>>>>>>>>>>>>>>>> connector can also emit latency metrics.
>>>>> > > >>>>>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>>>>> Thanks,
>>>>> > > >>>>>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>>>>> Jiangjie (Becket) Qin
>>>>> > > >>>>>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>>>>> On Thu, Feb 21, 2019 at 10:14 PM Chesnay
>>>>> Schepler
>>>>> > > >>>>>>>>>>>>>>>>> <chesnay@apache.org <mailto:chesnay@apache.org
>>>>> >>
>>>>> > > >>>>>>>>>>>>>>>>>>>> wrote:
>>>>> > > >>>>>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>>>>>> Regarding 2) It doesn't make sense to
>>>>> investigate
>>>>> > > this
>>>>> > > >>>>>>>>>>>>>> as
>>>>> > > >>>>>>>>>>>>>>>>> part of this
>>>>> > > >>>>>>>>>>>>>>>>>>>>> FLIP. This is something that could be of
>>>>> interest
>>>>> > for
>>>>> > > >>>>>>>>>>>>>> the
>>>>> > > >>>>>>>>>>>>>>>>> entire metric
>>>>> > > >>>>>>>>>>>>>>>>>>>>> system, and should be designed for as such.
>>>>> > > >>>>>>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>>>>>> Regarding the proposal as a whole:
>>>>> > > >>>>>>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>>>>>> Histogram metrics shall not be added to the
>>>>> core of
>>>>> > > >>>>>>>>>>>>>>>>> Flink. They are
>>>>> > > >>>>>>>>>>>>>>>>>>>>> significantly more expensive than other
>>>>> metrics,
>>>>> > and
>>>>> > > >>>>>>>>>>>>>>>>> calculating
>>>>> > > >>>>>>>>>>>>>>>>>>>>> histograms in the application is regarded as
>>>>> an
>>>>> > > >>>>>>>>>>>>>>>>> anti-pattern by several
>>>>> > > >>>>>>>>>>>>>>>>>>>>> metric backends, who instead recommend to
>>>>> expose
>>>>> > the
>>>>> > > >> raw
>>>>> > > >>>>>>>>>>>>>>>>> data and
>>>>> > > >>>>>>>>>>>>>>>>>>>>> calculate the histogram in the backend.
>>>>> > > >>>>>>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>>>>>> Second, this seems overly complicated. Given
>>>>> that
>>>>> > we
>>>>> > > >>>>>>>>>>>>>>>>> already established
>>>>> > > >>>>>>>>>>>>>>>>>>>>> that not all connectors will export all
>>>>> metrics we
>>>>> > > are
>>>>> > > >>>>>>>>>>>>>>>>> effectively
>>>>> > > >>>>>>>>>>>>>>>>>>>>> reducing this down to a consistent naming
>>>>> scheme.
>>>>> > We
>>>>> > > >>>>>>>>>>>>>>>>> don't need anything
>>>>> > > >>>>>>>>>>>>>>>>>>>>> sophisticated for that; basically just a few
>>>>> > > constants
>>>>> > > >>>>>>>>>>>>>>>>> that all
>>>>> > > >>>>>>>>>>>>>>>>>>>>> connectors use.
>>>>> > > >>>>>>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>>>>>> I'm not convinced that this is worthy of a
>>>>> FLIP.
>>>>> > > >>>>>>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>>>>>> On 21.02.2019 14:26, Dawid Wysakowicz wrote:
>>>>> > > >>>>>>>>>>>>>>>>>>>>>> Hi,
>>>>> > > >>>>>>>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>>>>>>> Ad 1. In general I undestand and I agree.
>>>>> But
>>>>> > those
>>>>> > > >>>>>>>>>>>>>>>>> particular metrics
>>>>> > > >>>>>>>>>>>>>>>>>>>>>> (latency, fetchLatency), right now would
>>>>> only be
>>>>> > > >>>>>>>>>>>>>>>>> reported if user uses
>>>>> > > >>>>>>>>>>>>>>>>>>>>>> KafkaConsumer with internal
>>>>> timestampAssigner with
>>>>> > > >>>>>>>>>>>>>>>>> StreamCharacteristic
>>>>> > > >>>>>>>>>>>>>>>>>>>>>> set to EventTime, right? That sounds like a
>>>>> very
>>>>> > > >>>>>>>>>>>>>>>>> specific case. I am
>>>>> > > >>>>>>>>>>>>>>>>>>> not
>>>>> > > >>>>>>>>>>>>>>>>>>>>>> sure if we should introduce a generic
>>>>> metric that
>>>>> > > will
>>>>> > > >>>>>>>>>>>>>> be
>>>>> > > >>>>>>>>>>>>>>>>>>>>>> disabled/absent for most of implementations.
>>>>> > > >>>>>>>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>>>>>>> Ad.2 That sounds like an orthogonal issue,
>>>>> that
>>>>> > > might
>>>>> > > >>>>>>>>>>>>>>>>> make sense to
>>>>> > > >>>>>>>>>>>>>>>>>>>>>> investigate in the future.
>>>>> > > >>>>>>>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>>>>>>> Best,
>>>>> > > >>>>>>>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>>>>>>> Dawid
>>>>> > > >>>>>>>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>>>>>>> On 21/02/2019 13:20, Becket Qin wrote:
>>>>> > > >>>>>>>>>>>>>>>>>>>>>>> Hi Dawid,
>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>>>>>>>> Thanks for the feedback. That makes sense
>>>>> to me.
>>>>> > > >> There
>>>>> > > >>>>>>>>>>>>>>>>> are two cases
>>>>> > > >>>>>>>>>>>>>>>>>>> to
>>>>> > > >>>>>>>>>>>>>>>>>>>>> be
>>>>> > > >>>>>>>>>>>>>>>>>>>>>>> addressed.
>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>>>>>>>> 1. The metrics are supposed to be a
>>>>> guidance. It
>>>>> > is
>>>>> > > >>>>>>>>>>>>>>>>> likely that a
>>>>> > > >>>>>>>>>>>>>>>>>>>>> connector
>>>>> > > >>>>>>>>>>>>>>>>>>>>>>> only supports some but not all of the
>>>>> metrics. In
>>>>> > > >> that
>>>>> > > >>>>>>>>>>>>>>>>> case, each
>>>>> > > >>>>>>>>>>>>>>>>>>>>> connector
>>>>> > > >>>>>>>>>>>>>>>>>>>>>>> implementation should have the freedom to
>>>>> decide
>>>>> > > >> which
>>>>> > > >>>>>>>>>>>>>>>>> metrics are
>>>>> > > >>>>>>>>>>>>>>>>>>>>>>> reported. For the metrics that are
>>>>> supported, the
>>>>> > > >>>>>>>>>>>>>>>>> guidance should be
>>>>> > > >>>>>>>>>>>>>>>>>>>>>>> followed.
>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>>>>>>>> 2. Sometimes users may want to disable
>>>>> certain
>>>>> > > >> metrics
>>>>> > > >>>>>>>>>>>>>>>>> for some reason
>>>>> > > >>>>>>>>>>>>>>>>>>>>>>> (e.g. performance / reprocessing of data).
>>>>> A
>>>>> > > generic
>>>>> > > >>>>>>>>>>>>>>>>> mechanism should
>>>>> > > >>>>>>>>>>>>>>>>>>> be
>>>>> > > >>>>>>>>>>>>>>>>>>>>>>> provided to allow user choose which
>>>>> metrics are
>>>>> > > >>>>>>>>>>>>>>>>> reported. This
>>>>> > > >>>>>>>>>>>>>>>>>>> mechanism
>>>>> > > >>>>>>>>>>>>>>>>>>>>>>> should also be honored by the connector
>>>>> > > >>>>>>>>>>>>>> implementations.
>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>>>>>>>> Does this sound reasonable to you?
>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>>>>>>>> Thanks,
>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>>>>>>>> Jiangjie (Becket) Qin
>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>>>>>>>> On Thu, Feb 21, 2019 at 4:22 PM Dawid
>>>>> Wysakowicz
>>>>> > <
>>>>> > > >>>>>>>>>>>>>>>>>>>>> dwysakowicz@apache.org <mailto:
>>>>> > > dwysakowicz@apache.org
>>>>> > > >>>>
>>>>> > > >>>>>>>>>>>>>>>>>>>>>>> wrote:
>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> Hi,
>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> Generally I like the idea of having a
>>>>> unified,
>>>>> > > >>>>>>>>>>>>>>>>> standard set of
>>>>> > > >>>>>>>>>>>>>>>>>>> metrics
>>>>> > > >>>>>>>>>>>>>>>>>>>>> for
>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> all connectors. I have some slight
>>>>> concerns
>>>>> > about
>>>>> > > >>>>>>>>>>>>>>>>> fetchLatency and
>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> latency though. They are computed based on
>>>>> > > EventTime
>>>>> > > >>>>>>>>>>>>>>>>> which is not a
>>>>> > > >>>>>>>>>>>>>>>>>>>>> purely
>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> technical feature. It depends often on
>>>>> some
>>>>> > > business
>>>>> > > >>>>>>>>>>>>>>>>> logic, might be
>>>>> > > >>>>>>>>>>>>>>>>>>>>> absent
>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> or defined after source. Those metrics
>>>>> could
>>>>> > also
>>>>> > > >>>>>>>>>>>>>>>>> behave in a weird
>>>>> > > >>>>>>>>>>>>>>>>>>>>> way in
>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> case of replaying backlog. Therefore I am
>>>>> not
>>>>> > sure
>>>>> > > >> if
>>>>> > > >>>>>>>>>>>>>>>>> we should
>>>>> > > >>>>>>>>>>>>>>>>>>> include
>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> those metrics by default. Maybe we could
>>>>> at
>>>>> > least
>>>>> > > >>>>>>>>>>>>>>>>> introduce a feature
>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> switch for them? What do you think?
>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> Best,
>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> Dawid
>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> On 21/02/2019 03:13, Becket Qin wrote:
>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> Bump. If there is no objections to the
>>>>> proposed
>>>>> > > >>>>>>>>>>>>>>>>> metrics. I'll start a
>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> voting thread later toady.
>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> Thanks,
>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> Jiangjie (Becket) Qin
>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> On Mon, Feb 11, 2019 at 8:17 PM Becket Qin
>>>>> > > >>>>>>>>>>>>>>>>> <becket.qin@gmail.com <mailto:
>>>>> becket.qin@gmail.com>>
>>>>> > <
>>>>> > > >>>>>>>>>>>>>>>>>>>>> becket.qin@gmail.com <mailto:
>>>>> becket.qin@gmail.com
>>>>> > >>
>>>>> > > >>>>>>>>>>>>>>> wrote:
>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> Hi folks,
>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> I would like to start the FLIP discussion
>>>>> thread
>>>>> > > >>>>>>>>>>>>>> about
>>>>> > > >>>>>>>>>>>>>>>>> standardize
>>>>> > > >>>>>>>>>>>>>>>>>>> the
>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> connector metrics.
>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> In short, we would like to provide a
>>>>> convention
>>>>> > of
>>>>> > > >>>>>>>>>>>>>>>>> Flink connector
>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> metrics. It will help simplify the
>>>>> monitoring
>>>>> > and
>>>>> > > >>>>>>>>>>>>>>>>> alerting on Flink
>>>>> > > >>>>>>>>>>>>>>>>>>>>> jobs.
>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> The FLIP link is following:
>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>
>>>>> > > >>>>>>>>>
>>>>> > > >>>>>>>
>>>>> > > >>>>>
>>>>> > > >>
>>>>> > >
>>>>> >
>>>>> https://cwiki.apache.org/confluence/display/FLINK/FLIP-33%3A+Standardize+Connector+Metrics
>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> Thanks,
>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> Jiangjie (Becket) Qin
>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>
>>>>> > > >>>>>>>>>>>>
>>>>> > > >>>>>>>>>
>>>>> > > >>>>>>>>>
>>>>> > > >>>>>>>>>
>>>>> > > >>>>>>>
>>>>> > > >>>>>>>
>>>>> > > >>>>>>>
>>>>> > > >>>>>
>>>>> > > >>>>>
>>>>> > > >>
>>>>> > > >>
>>>>> > >
>>>>> > >
>>>>> >
>>>>>
>>>>>
>>>>> --
>>>>>
>>>>> Konstantin Knauf
>>>>>
>>>>> https://twitter.com/snntrable
>>>>>
>>>>> https://github.com/knaufk
>>>>>
>>>>
Re: [DISCUSS] FLIP-33: Standardize connector metrics
Posted by Becket Qin <be...@gmail.com>.
Hi Stephan,
Thanks for the input. Just a few more clarifications / questions.
*Num Bytes / Records Metrics*
1. At this point, the *numRecordsIn(Rate)* metrics exist in both
OperatorIOMetricGroup and TaskIOMetricGroup. I did not find
*numRecordsIn(Rate)* in the TaskIOMetricGroup updated anywhere other than
in the unit tests. Am I missing something?
2. *numBytesIn(Rate)* metrics only exist in TaskIOMetricGroup. At this
point, the SourceReaders only has access to a SourceReaderContext which
provides an OperatorMetricGroup. So it seems that the connector developers
are not able to update the *numBytesIn(Rate). *With the multiple Source
chaining support, it is possible that there are multiple Sources are in the
same task. So it looks that we need to add *numBytesIn(Rate)* to the
operator metrics as well.
*Current (Fetch) Latency*
*currentFetchLatency* helps clearly tell whether the latency is caused by
Flink or not. Backpressure is not the only reason that we see fetch
latency. Even if there is no back pressure, the records may have passed a
long pipeline before they entered Flink. For example, say the *currentLatency
*is 10 seconds and there is no backpressure. Does that mean the record
spent 10 seconds in the Source operator? If not, how much did Flink
contribute to that 10 seconds of latency? These questions are frequently
asked and hard to tell without the fetch latency.
For "currentFetchLatency", we would need to understand timestamps before
> the records are decoded. That is only possible for some sources, where the
> client gives us the records in a (partially) decoded from already (like
> Kafka). Then, some work has been done between the fetch time and the time
> we update the metric already, so it is already a bit closer to the
> "currentFetchLatency". I think following this train of thought, there is
> diminished benefit from that specific metric.
We may not have to report the fetch latency before records are decoded. One
solution is to remember the* FetchTime* when the encoded records are
fetched, and report the fetch latency after the records are decoded by
computing (*FetchTime - EventTime*). An approximate implementation would be
adding a *FetchTime *field to the *RecordsWithSplitIds* assuming that all
the records in that data structure are fetched at the same time.
Thoughts?
Thanks,
Jiangjie (Becket) Qin
On Wed, Sep 9, 2020 at 12:42 AM Stephan Ewen <st...@ververica.com> wrote:
> Thanks for reviving this, Becket!
>
> I think Konstantin's comments are great. I'd add these points:
>
> *Num Bytes / Records Metrics*
>
> For "numBytesIn" and "numRecordsIn", we should reuse the OperatorIOMetric
> group, then it also gets reported to the overview page in the Web UI.
>
> The "numBytesInPerSecond" and "numRecordsInPerSecond" are automatically
> derived metrics, no need to do anything once we populate the above two
> metrics
>
>
> *Current (Fetch) Latency*
>
> I would really go for "eventTimeLag" rather than "fetchLatency". I think
> "eventTimeLag" is a term that has some adoption in the Flink community and
> beyond.
>
> I am not so sure that I see the benefit between "currentLatency" and
> "currentFetchLatency", (or event time lag before/after) as this only is
> different by the time it takes to emit a batch.
> - In a non-backpressured case, these should be virtually identical
> (and both dominated by watermark lag, not the actual time it takes the
> fetch to be emitted)
> - In a backpressured case, why do you care about when data was
> fetched, as opposed to emitted? Emitted time is relevant for application
> semantics and checkpoints. Fetch time seems to be an implementation detail
> (how much does the source buffer).
>
> The "currentLatency" (eventTimeLagAfter) can be computed out-of-the-box,
> independent of a source implementation, so that is also a good argument to
> make it the main metric.
> We know timestamps and watermarks in the source. Except for cases where no
> watermarks have been defined at all (batch jobs or pure processing time
> jobs), in which case this metric should probably be "Infinite".
>
> For "currentFetchLatency", we would need to understand timestamps before
> the records are decoded. That is only possible for some sources, where the
> client gives us the records in a (partially) decoded from already (like
> Kafka). Then, some work has been done between the fetch time and the time
> we update the metric already, so it is already a bit closer to the
> "currentFetchLatency". I think following this train of thought, there is
> diminished benefit from that specific metric.
>
>
> *Idle Time*
>
> I agree, it would be great to rename this. Maybe to "sourceWaitTime" or
> "sourceIdleTime" so to make clear that this is not exactly the time that
> Flink's processing pipeline is idle, but the time where the source does not
> have new data.
>
> This is not an easy metric to collect, though (except maybe for the
> sources that are only idle while they have no split assigned, like
> continuous file source).
>
> *Source Specific Metrics*
>
> I believe source-specific would only be "sourceIdleTime",
> "numRecordsInErrors", "pendingBytes", and "pendingRecords".
>
>
> *Conclusion*
>
> We can probably add "numBytesIn" and "numRecordsIn" and "eventTimeLag"
> right away, with little complexity.
> I'd suggest to start with these right away.
>
> Best,
> Stephan
>
>
> On Tue, Sep 8, 2020 at 3:25 PM Becket Qin <be...@gmail.com> wrote:
>
>> Hey Konstantin,
>>
>> Thanks for the feedback and suggestions. Please see the reply below.
>>
>> * idleTime: In the meantime, a similar metric "idleTimeMsPerSecond" has
>>> been introduced in https://issues.apache.org/jira/browse/FLINK-16864.
>>> They
>>> have a similar name, but different definitions of idleness,
>>> e.g. "idleTimeMsPerSecond" considers the SourceTask idle, when it is
>>> backpressured. Can we make it clearer that these two metrics mean
>>> different
>>> things?
>>
>>
>> That is a good point. I did not notice this metric earlier. It seems that
>> both metrics are useful to the users. One tells them how busy the source is
>> and how much more throughput the source can handle. The other tells the
>> users how long since the source has seen the last record, which is useful
>> for debugging. I'll update the FLIP to make it clear.
>>
>> * "current(Fetch)Latency" I am wondering if "eventTimeLag(Before|After)"
>>> is more descriptive/clear. What do others think?
>>
>>
>> I am quite open to the ideas on these names. In fact I also feel
>> "current(Fetch)Latency" are not super intuitive. So it would be great if we
>> can have better names.
>>
>> * Current(Fetch)Latency implies that the timestamps are directly
>>> extracted in the source connector, right? Will this be the default for
>>> FLIP-27 sources anyway?
>>
>>
>> The "currentFetchLatency" will probably be reported by each source
>> implementation, because the data fetching is done by SplitReaders and there
>> is no base implementation. The "currentLatency", on the other hand, can be
>> reported by the SourceReader base implementation. However, since developers
>> can actually implement their own source connector without using our base
>> implementation, these metric guidance are still useful for the connector
>> developers in that case.
>>
>> * Does FLIP-33 also include the implementation of these metrics (to the
>>> extent possible) for all connectors currently available in Apache Flink
>>> or
>>> is the "per-connector implementation" out-of-scope?
>>
>>
>> FLIP-33 itself does not specify any implementation of those metrics. But
>> the connectors we provide in Apache Flink will follow the guidance of
>> FLIP-33 to emit those metrics when applicable. Maybe We can have some
>> public static Strings defined for the metric names to help other connector
>> developers follow the same guidance. I can also add that to the public
>> interface section of the FLIP if we decide to do that.
>>
>> Thanks,
>>
>> Jiangjie (Becket) Qin
>>
>> On Tue, Sep 8, 2020 at 9:02 PM Becket Qin <be...@gmail.com> wrote:
>>
>>>
>>>
>>> On Tue, Sep 8, 2020 at 6:55 PM Konstantin Knauf <kn...@apache.org>
>>> wrote:
>>>
>>>> Hi Becket,
>>>>
>>>> Thank you for picking up this FLIP. I have a few questions:
>>>>
>>>> * two thoughts on naming:
>>>> * idleTime: In the meantime, a similar metric "idleTimeMsPerSecond"
>>>> has
>>>> been introduced in https://issues.apache.org/jira/browse/FLINK-16864.
>>>> They
>>>> have a similar name, but different definitions of idleness,
>>>> e.g. "idleTimeMsPerSecond" considers the SourceTask idle, when it is
>>>> backpressured. Can we make it clearer that these two metrics mean
>>>> different
>>>> things?
>>>>
>>>> * "current(Fetch)Latency" I am wondering if
>>>> "eventTimeLag(Before|After)"
>>>> is more descriptive/clear. What do others think?
>>>>
>>>> * Current(Fetch)Latency implies that the timestamps are directly
>>>> extracted in the source connector, right? Will this be the default for
>>>> FLIP-27 sources anyway?
>>>>
>>>> * Does FLIP-33 also include the implementation of these metrics (to the
>>>> extent possible) for all connectors currently available in Apache Flink
>>>> or
>>>> is the "per-connector implementation" out-of-scope?
>>>>
>>>> Thanks,
>>>>
>>>> Konstantin
>>>>
>>>>
>>>>
>>>>
>>>>
>>>> On Fri, Sep 4, 2020 at 4:56 PM Becket Qin <be...@gmail.com> wrote:
>>>>
>>>> > Hi all,
>>>> >
>>>> > To complete the Source refactoring work, I'd like to revive this
>>>> > discussion. Since the mail thread has been dormant for more than a
>>>> year,
>>>> > just to recap the motivation of the FLIP:
>>>> >
>>>> > 1. The FLIP proposes to standardize the connector metrics by giving
>>>> > guidance on the metric specifications, including the name, type and
>>>> meaning
>>>> > of the metrics.
>>>> > 2. It is OK for a connector to not emit some of the metrics in the
>>>> metric
>>>> > guidance, but if a metric of the same semantic is emitted, the
>>>> > implementation should follow the guidance.
>>>> > 3. It is OK for a connector to emit more metrics than what are listed
>>>> in
>>>> > the FLIP. This includes having an alias for a metric specified in the
>>>> FLIP.
>>>> > 4. We will implement some of the metrics out of the box in the default
>>>> > implementation of FLIP-27, as long as it is applicable.
>>>> >
>>>> > The FLIP wiki is following:
>>>> > https://cwiki.apache.org/confluence/display/FLINK/FLIP-33
>>>> > %3A+Standardize+Connector+Metrics
>>>> >
>>>> > Any thoughts?
>>>> >
>>>> > Thanks,
>>>> >
>>>> > Jiangjie (Becket) Qin
>>>> >
>>>> >
>>>> > On Fri, Jun 14, 2019 at 2:29 PM Piotr Nowojski <pi...@ververica.com>
>>>> > wrote:
>>>> >
>>>> > > > we will need to revisit the convention list and adjust them
>>>> accordingly
>>>> > > when FLIP-27 is ready
>>>> > >
>>>> > >
>>>> > > Yes, this sounds good :)
>>>> > >
>>>> > > Piotrek
>>>> > >
>>>> > > > On 13 Jun 2019, at 13:35, Becket Qin <be...@gmail.com>
>>>> wrote:
>>>> > > >
>>>> > > > Hi Piotr,
>>>> > > >
>>>> > > > That's great to know. Chances are that we will need to revisit the
>>>> > > > convention list and adjust them accordingly when FLIP-27 is
>>>> ready, At
>>>> > > that
>>>> > > > point we can mark some of the metrics as available by default for
>>>> > > > connectors implementing the new interface.
>>>> > > >
>>>> > > > Thanks,
>>>> > > >
>>>> > > > Jiangjie (Becket) Qin
>>>> > > >
>>>> > > > On Thu, Jun 13, 2019 at 3:51 PM Piotr Nowojski <
>>>> piotr@ververica.com>
>>>> > > wrote:
>>>> > > >
>>>> > > >> Thanks for driving this. I’ve just noticed one small thing. With
>>>> new
>>>> > > >> SourceReader interface Flink will be able to provide `idleTime`
>>>> metric
>>>> > > >> automatically.
>>>> > > >>
>>>> > > >> Piotrek
>>>> > > >>
>>>> > > >>> On 13 Jun 2019, at 03:30, Becket Qin <be...@gmail.com>
>>>> wrote:
>>>> > > >>>
>>>> > > >>> Thanks all for the feedback and discussion.
>>>> > > >>>
>>>> > > >>> Since there wasn't any concern raised, I've started the voting
>>>> thread
>>>> > > for
>>>> > > >>> this FLIP, but please feel free to continue the discussion here
>>>> if
>>>> > you
>>>> > > >>> think something still needs to be addressed.
>>>> > > >>>
>>>> > > >>> Thanks,
>>>> > > >>>
>>>> > > >>> Jiangjie (Becket) Qin
>>>> > > >>>
>>>> > > >>>
>>>> > > >>>
>>>> > > >>> On Mon, Jun 10, 2019 at 9:10 AM Becket Qin <
>>>> becket.qin@gmail.com>
>>>> > > wrote:
>>>> > > >>>
>>>> > > >>>> Hi Piotr,
>>>> > > >>>>
>>>> > > >>>> Thanks for the comments. Yes, you are right. Users will have
>>>> to look
>>>> > > at
>>>> > > >>>> other metrics to decide whether the pipeline is healthy or not
>>>> in
>>>> > the
>>>> > > >> first
>>>> > > >>>> place before they can use the time-based metric to fix the
>>>> > bottleneck.
>>>> > > >>>>
>>>> > > >>>> I agree that once we have FLIP-27 ready, some of the metrics
>>>> can
>>>> > just
>>>> > > be
>>>> > > >>>> reported by the abstract implementation.
>>>> > > >>>>
>>>> > > >>>> I've updated FLIP-33 wiki page to add the pendingBytes and
>>>> > > >> pendingRecords
>>>> > > >>>> metric. Please let me know if you have any concern over the
>>>> updated
>>>> > > >> metric
>>>> > > >>>> convention proposal.
>>>> > > >>>>
>>>> > > >>>> @Chesnay Schepler <ch...@apache.org> @Stephan Ewen
>>>> > > >>>> <st...@ververica.com> will you also have time to take a
>>>> look at
>>>> > the
>>>> > > >>>> proposed metric convention? If there is no further concern I'll
>>>> > start
>>>> > > a
>>>> > > >>>> voting thread for this FLIP in two days.
>>>> > > >>>>
>>>> > > >>>> Thanks,
>>>> > > >>>>
>>>> > > >>>> Jiangjie (Becket) Qin
>>>> > > >>>>
>>>> > > >>>>
>>>> > > >>>>
>>>> > > >>>> On Wed, Jun 5, 2019 at 6:54 PM Piotr Nowojski <
>>>> piotr@ververica.com>
>>>> > > >> wrote:
>>>> > > >>>>
>>>> > > >>>>> Hi Becket,
>>>> > > >>>>>
>>>> > > >>>>> Thanks for the answer :)
>>>> > > >>>>>
>>>> > > >>>>>> By time-based metric, I meant the portion of time spent on
>>>> > producing
>>>> > > >> the
>>>> > > >>>>>> record to downstream. For example, a source connector can
>>>> report
>>>> > > that
>>>> > > >>>>> it's
>>>> > > >>>>>> spending 80% of time to emit record to downstream processing
>>>> > > pipeline.
>>>> > > >>>>> In
>>>> > > >>>>>> another case, a sink connector may report that its spending
>>>> 30% of
>>>> > > >> time
>>>> > > >>>>>> producing the records to the external system.
>>>> > > >>>>>>
>>>> > > >>>>>> This is in some sense equivalent to the buffer usage metric:
>>>> > > >>>>>
>>>> > > >>>>>> - 80% of time spent on emitting records to downstream --->
>>>> > > downstream
>>>> > > >>>>>> node is bottleneck ---> output buffer is probably full.
>>>> > > >>>>>> - 30% of time spent on emitting records to downstream --->
>>>> > > downstream
>>>> > > >>>>>> node is not bottleneck ---> output buffer is probably not
>>>> full.
>>>> > > >>>>>
>>>> > > >>>>> If by “time spent on emitting records to downstream” you
>>>> understand
>>>> > > >>>>> “waiting on back pressure”, then I see your point. And I
>>>> agree that
>>>> > > >> some
>>>> > > >>>>> kind of ratio/time based metric gives you more information.
>>>> However
>>>> > > >> under
>>>> > > >>>>> “time spent on emitting records to downstream” might be
>>>> hidden the
>>>> > > >>>>> following (extreme) situation:
>>>> > > >>>>>
>>>> > > >>>>> 1. Job is barely able to handle influx of records, there is
>>>> 99%
>>>> > > >>>>> CPU/resource usage in the cluster, but nobody is
>>>> > > >>>>> bottlenecked/backpressured, all output buffers are empty,
>>>> everybody
>>>> > > is
>>>> > > >>>>> waiting in 1% of it’s time for more records to process.
>>>> > > >>>>> 2. 80% time can still be spent on "down stream operators”,
>>>> because
>>>> > > they
>>>> > > >>>>> are the CPU intensive operations, but this doesn’t mean that
>>>> > > >> increasing the
>>>> > > >>>>> parallelism down the stream will help with anything there. To
>>>> the
>>>> > > >> contrary,
>>>> > > >>>>> increasing parallelism of the source operator might help to
>>>> > increase
>>>> > > >>>>> resource utilisation up to 100%.
>>>> > > >>>>>
>>>> > > >>>>> However, this “time based/ratio” approach can be extended to
>>>> > > in/output
>>>> > > >>>>> buffer usage. Besides collecting an information that
>>>> input/output
>>>> > > >> buffer is
>>>> > > >>>>> full/empty, we can probe profile how often are buffer
>>>> empty/full.
>>>> > If
>>>> > > >> output
>>>> > > >>>>> buffer is full 1% of times, there is almost no back pressure.
>>>> If
>>>> > it’s
>>>> > > >> full
>>>> > > >>>>> 80% of times, there is some back pressure, if it’s full 99.9%
>>>> of
>>>> > > times,
>>>> > > >>>>> there is huge back pressure.
>>>> > > >>>>>
>>>> > > >>>>> Now for autoscaling you could compare the input & output
>>>> buffers
>>>> > fill
>>>> > > >>>>> ratio:
>>>> > > >>>>>
>>>> > > >>>>> 1. Both are high, the source of bottleneck is down the stream
>>>> > > >>>>> 2. Output is low, input is high, this is the bottleneck and
>>>> the
>>>> > > higher
>>>> > > >>>>> the difference, the bigger source of bottleneck is this is
>>>> > > >> operator/task
>>>> > > >>>>> 3. Output is high, input is low - there was some load spike
>>>> that we
>>>> > > are
>>>> > > >>>>> currently finishing to process
>>>> > > >>>>>
>>>> > > >>>>>
>>>> > > >>>>>
>>>> > > >>>>> But long story short, we are probably diverging from the
>>>> topic of
>>>> > > this
>>>> > > >>>>> discussion, and we can discuss this at some later point.
>>>> > > >>>>>
>>>> > > >>>>> For now, for sources:
>>>> > > >>>>>
>>>> > > >>>>> as I wrote before, +1 for:
>>>> > > >>>>> - pending.bytes, Gauge
>>>> > > >>>>> - pending.messages, Gauge
>>>> > > >>>>>
>>>> > > >>>>> When we will be developing/discussing SourceReader from
>>>> FLIP-27 we
>>>> > > >> might
>>>> > > >>>>> then add:
>>>> > > >>>>>
>>>> > > >>>>> - in-memory.buffer.usage (0 - 100%)
>>>> > > >>>>>
>>>> > > >>>>> Which will be estimated automatically by Flink while user
>>>> will be
>>>> > > able
>>>> > > >> to
>>>> > > >>>>> override/provide better estimation.
>>>> > > >>>>>
>>>> > > >>>>> Piotrek
>>>> > > >>>>>
>>>> > > >>>>>> On 5 Jun 2019, at 05:42, Becket Qin <be...@gmail.com>
>>>> wrote:
>>>> > > >>>>>>
>>>> > > >>>>>> Hi Piotr,
>>>> > > >>>>>>
>>>> > > >>>>>> Thanks for the explanation. Please see some clarifications
>>>> below.
>>>> > > >>>>>>
>>>> > > >>>>>> By time-based metric, I meant the portion of time spent on
>>>> > producing
>>>> > > >> the
>>>> > > >>>>>> record to downstream. For example, a source connector can
>>>> report
>>>> > > that
>>>> > > >>>>> it's
>>>> > > >>>>>> spending 80% of time to emit record to downstream processing
>>>> > > pipeline.
>>>> > > >>>>> In
>>>> > > >>>>>> another case, a sink connector may report that its spending
>>>> 30% of
>>>> > > >> time
>>>> > > >>>>>> producing the records to the external system.
>>>> > > >>>>>>
>>>> > > >>>>>> This is in some sense equivalent to the buffer usage metric:
>>>> > > >>>>>> - 80% of time spent on emitting records to downstream --->
>>>> > > downstream
>>>> > > >>>>>> node is bottleneck ---> output buffer is probably full.
>>>> > > >>>>>> - 30% of time spent on emitting records to downstream --->
>>>> > > downstream
>>>> > > >>>>>> node is not bottleneck ---> output buffer is probably not
>>>> full.
>>>> > > >>>>>>
>>>> > > >>>>>> However, the time-based metric has a few advantages that the
>>>> > buffer
>>>> > > >>>>> usage
>>>> > > >>>>>> metric may not have.
>>>> > > >>>>>>
>>>> > > >>>>>> 1. Buffer usage metric may not be applicable to all the
>>>> connector
>>>> > > >>>>>> implementations, while reporting time-based metric are always
>>>> > > doable.
>>>> > > >>>>>> Some source connectors may not have any input buffer, or
>>>> they may
>>>> > > use
>>>> > > >>>>> some
>>>> > > >>>>>> third party library that does not expose the input buffer at
>>>> all.
>>>> > > >>>>>> Similarly, for sink connectors, the implementation may not
>>>> have
>>>> > any
>>>> > > >>>>> output
>>>> > > >>>>>> buffer, or the third party library does not expose such
>>>> buffer.
>>>> > > >>>>>>
>>>> > > >>>>>> 2. Although both type of metrics can detect bottleneck,
>>>> time-based
>>>> > > >>>>> metrics
>>>> > > >>>>>> can be used to generate a more informed action to remove the
>>>> > > >> bottleneck.
>>>> > > >>>>>> For example, when the downstream is bottleneck, the output
>>>> buffer
>>>> > > >> usage
>>>> > > >>>>>> metric is likely to be 100%, and the input buffer usage
>>>> might be
>>>> > 0%.
>>>> > > >>>>> That
>>>> > > >>>>>> means we don't know what is the suitable parallelism to lift
>>>> the
>>>> > > >>>>>> bottleneck. The time-based metric, on the other hand, would
>>>> give
>>>> > > >> useful
>>>> > > >>>>>> information, e.g. if 80% of time was spent on emitting
>>>> records, we
>>>> > > can
>>>> > > >>>>>> roughly increase the downstream node parallelism by 4 times.
>>>> > > >>>>>>
>>>> > > >>>>>> Admittedly, the time-based metrics are more expensive than
>>>> buffer
>>>> > > >>>>> usage. So
>>>> > > >>>>>> we may have to do some sampling to reduce the cost. But in
>>>> > general,
>>>> > > >>>>> using
>>>> > > >>>>>> time-based metrics seems worth adding.
>>>> > > >>>>>>
>>>> > > >>>>>> That being said, I don't think buffer usage metric and
>>>> time-based
>>>> > > >>>>> metrics
>>>> > > >>>>>> are mutually exclusive. We can probably have both. It is
>>>> just that
>>>> > > in
>>>> > > >>>>>> practice, features like auto-scaling might prefer time-based
>>>> > metrics
>>>> > > >> for
>>>> > > >>>>>> the reason stated above.
>>>> > > >>>>>>
>>>> > > >>>>>>> 1. Define the metrics that would allow us to manually detect
>>>> > > >>>>> bottlenecks.
>>>> > > >>>>>> As I wrote, we already have them in most of the places,
>>>> except of
>>>> > > >>>>>> sources/sinks.
>>>> > > >>>>>>> 2. Use those metrics, to automatically detect bottlenecks.
>>>> > > Currently
>>>> > > >> we
>>>> > > >>>>>> are only automatically detecting back pressure and reporting
>>>> it to
>>>> > > the
>>>> > > >>>>> user
>>>> > > >>>>>> in web UI (is it exposed as a metric at all?). Detecting the
>>>> root
>>>> > > >> cause
>>>> > > >>>>> of
>>>> > > >>>>>> the back pressure (bottleneck) is one step further.
>>>> > > >>>>>>> 3. Use the knowledge about where exactly the bottleneck is
>>>> > located,
>>>> > > >> to
>>>> > > >>>>>> try to do something with it.
>>>> > > >>>>>>
>>>> > > >>>>>> As explained above, I think time-based metric also addresses
>>>> item
>>>> > 1
>>>> > > >> and
>>>> > > >>>>>> item 2.
>>>> > > >>>>>>
>>>> > > >>>>>> Any thoughts？
>>>> > > >>>>>>
>>>> > > >>>>>> Thanks,
>>>> > > >>>>>>
>>>> > > >>>>>> Jiangjie (Becket) Qin
>>>> > > >>>>>>
>>>> > > >>>>>>
>>>> > > >>>>>>
>>>> > > >>>>>> On Mon, Jun 3, 2019 at 4:14 PM Piotr Nowojski <
>>>> > piotr@ververica.com>
>>>> > > >>>>> wrote:
>>>> > > >>>>>>
>>>> > > >>>>>>> Hi again :)
>>>> > > >>>>>>>
>>>> > > >>>>>>>> - pending.bytes, Gauge
>>>> > > >>>>>>>> - pending.messages, Gauge
>>>> > > >>>>>>>
>>>> > > >>>>>>>
>>>> > > >>>>>>> +1
>>>> > > >>>>>>>
>>>> > > >>>>>>> And true, instead of overloading one of the metric it is
>>>> better
>>>> > > when
>>>> > > >>>>> user
>>>> > > >>>>>>> can choose to provide only one of them.
>>>> > > >>>>>>>
>>>> > > >>>>>>> Re 2:
>>>> > > >>>>>>>
>>>> > > >>>>>>>> If I understand correctly, this metric along with the
>>>> pending
>>>> > > >> mesages
>>>> > > >>>>> /
>>>> > > >>>>>>>> bytes would answer the questions of:
>>>> > > >>>>>>>
>>>> > > >>>>>>>> - Does the connector consume fast enough? Lagging behind +
>>>> empty
>>>> > > >>>>> buffer
>>>> > > >>>>>>> =
>>>> > > >>>>>>>> cannot consume fast enough.
>>>> > > >>>>>>>> - Does the connector emit fast enough? Lagging behind +
>>>> full
>>>> > > buffer
>>>> > > >> =
>>>> > > >>>>>>>> cannot emit fast enough, i.e. the Flink pipeline is slow.
>>>> > > >>>>>>>
>>>> > > >>>>>>> Yes, exactly. This can also be used to support decisions
>>>> like
>>>> > > >> changing
>>>> > > >>>>> the
>>>> > > >>>>>>> parallelism of the sources and/or down stream operators.
>>>> > > >>>>>>>
>>>> > > >>>>>>> I’m not sure if I understand your proposal with time based
>>>> > > >>>>> measurements.
>>>> > > >>>>>>> Maybe I’m missing something, but I do not see how measuring
>>>> time
>>>> > > >> alone
>>>> > > >>>>>>> could answer the problem: where is the bottleneck. Time
>>>> spent on
>>>> > > the
>>>> > > >>>>>>> next/emit might be short or long (depending on how heavy to
>>>> > process
>>>> > > >> the
>>>> > > >>>>>>> record is) and the source can still be bottlenecked/back
>>>> > pressured
>>>> > > or
>>>> > > >>>>> not.
>>>> > > >>>>>>> Usually the easiest and the most reliable way how to detect
>>>> > > >>>>> bottlenecks is
>>>> > > >>>>>>> by checking usage of input & output buffers, since when
>>>> input
>>>> > > buffer
>>>> > > >> is
>>>> > > >>>>>>> full while output buffer is empty, that’s the definition of
>>>> a
>>>> > > >>>>> bottleneck.
>>>> > > >>>>>>> Also this is usually very easy and cheap to measure (it
>>>> works
>>>> > > >>>>> effectively
>>>> > > >>>>>>> the same way as current’s Flink back pressure monitoring,
>>>> but
>>>> > more
>>>> > > >>>>> cleanly,
>>>> > > >>>>>>> without probing thread’s stack traces).
>>>> > > >>>>>>>
>>>> > > >>>>>>> Also keep in mind that we are already using the buffer usage
>>>> > > metrics
>>>> > > >>>>> for
>>>> > > >>>>>>> detecting the bottlenecks in Flink’s internal network
>>>> exchanges
>>>> > > >> (manual
>>>> > > >>>>>>> work). That’s the reason why I wanted to extend this to
>>>> > > >> sources/sinks,
>>>> > > >>>>>>> since they are currently our blind spot.
>>>> > > >>>>>>>
>>>> > > >>>>>>>> One feature we are currently working on to scale Flink
>>>> > > automatically
>>>> > > >>>>>>> relies
>>>> > > >>>>>>>> on some metrics answering the same question
>>>> > > >>>>>>>
>>>> > > >>>>>>> That would be very helpful feature. I think in order to
>>>> achieve
>>>> > > that
>>>> > > >> we
>>>> > > >>>>>>> would need to:
>>>> > > >>>>>>> 1. Define the metrics that would allow us to manually detect
>>>> > > >>>>> bottlenecks.
>>>> > > >>>>>>> As I wrote, we already have them in most of the places,
>>>> except of
>>>> > > >>>>>>> sources/sinks.
>>>> > > >>>>>>> 2. Use those metrics, to automatically detect bottlenecks.
>>>> > > Currently
>>>> > > >> we
>>>> > > >>>>>>> are only automatically detecting back pressure and
>>>> reporting it
>>>> > to
>>>> > > >> the
>>>> > > >>>>> user
>>>> > > >>>>>>> in web UI (is it exposed as a metric at all?). Detecting
>>>> the root
>>>> > > >>>>> cause of
>>>> > > >>>>>>> the back pressure (bottleneck) is one step further.
>>>> > > >>>>>>> 3. Use the knowledge about where exactly the bottleneck is
>>>> > located,
>>>> > > >> to
>>>> > > >>>>> try
>>>> > > >>>>>>> to do something with it.
>>>> > > >>>>>>>
>>>> > > >>>>>>> I think you are aiming for point 3., but before we reach
>>>> it, we
>>>> > are
>>>> > > >>>>> still
>>>> > > >>>>>>> missing 1. & 2. Also even if we have 3., there is a value
>>>> in 1 &
>>>> > 2
>>>> > > >> for
>>>> > > >>>>>>> manual analysis/dashboards.
>>>> > > >>>>>>>
>>>> > > >>>>>>> However, having the knowledge of where the bottleneck is,
>>>> doesn’t
>>>> > > >>>>>>> necessarily mean that we know what we can do about it. For
>>>> > example
>>>> > > >>>>>>> increasing parallelism might or might not help with anything
>>>> > (data
>>>> > > >>>>> skew,
>>>> > > >>>>>>> bottleneck on some resource that does not scale), but this
>>>> remark
>>>> > > >>>>> applies
>>>> > > >>>>>>> always, regardless of the way how did we detect the
>>>> bottleneck.
>>>> > > >>>>>>>
>>>> > > >>>>>>> Piotrek
>>>> > > >>>>>>>
>>>> > > >>>>>>>> On 3 Jun 2019, at 06:16, Becket Qin <be...@gmail.com>
>>>> > wrote:
>>>> > > >>>>>>>>
>>>> > > >>>>>>>> Hi Piotr,
>>>> > > >>>>>>>>
>>>> > > >>>>>>>> Thanks for the suggestion. Some thoughts below:
>>>> > > >>>>>>>>
>>>> > > >>>>>>>> Re 1: The pending messages / bytes.
>>>> > > >>>>>>>> I completely agree these are very useful metrics and we
>>>> should
>>>> > > >> expect
>>>> > > >>>>> the
>>>> > > >>>>>>>> connector to report. WRT the way to expose them, it seems
>>>> more
>>>> > > >>>>> consistent
>>>> > > >>>>>>>> to add two metrics instead of adding a method (unless
>>>> there are
>>>> > > >> other
>>>> > > >>>>> use
>>>> > > >>>>>>>> cases other than metric reporting). So we can add the
>>>> following
>>>> > > two
>>>> > > >>>>>>> metrics.
>>>> > > >>>>>>>> - pending.bytes, Gauge
>>>> > > >>>>>>>> - pending.messages, Gauge
>>>> > > >>>>>>>> Applicable connectors can choose to report them. These two
>>>> > metrics
>>>> > > >>>>> along
>>>> > > >>>>>>>> with latency should be sufficient for users to understand
>>>> the
>>>> > > >> progress
>>>> > > >>>>>>> of a
>>>> > > >>>>>>>> connector.
>>>> > > >>>>>>>>
>>>> > > >>>>>>>>
>>>> > > >>>>>>>> Re 2: Number of buffered data in-memory of the connector
>>>> > > >>>>>>>> If I understand correctly, this metric along with the
>>>> pending
>>>> > > >> mesages
>>>> > > >>>>> /
>>>> > > >>>>>>>> bytes would answer the questions of:
>>>> > > >>>>>>>> - Does the connector consume fast enough? Lagging behind +
>>>> empty
>>>> > > >>>>> buffer
>>>> > > >>>>>>> =
>>>> > > >>>>>>>> cannot consume fast enough.
>>>> > > >>>>>>>> - Does the connector emit fast enough? Lagging behind +
>>>> full
>>>> > > buffer
>>>> > > >> =
>>>> > > >>>>>>>> cannot emit fast enough, i.e. the Flink pipeline is slow.
>>>> > > >>>>>>>>
>>>> > > >>>>>>>> One feature we are currently working on to scale Flink
>>>> > > automatically
>>>> > > >>>>>>> relies
>>>> > > >>>>>>>> on some metrics answering the same question, more
>>>> specifically,
>>>> > we
>>>> > > >> are
>>>> > > >>>>>>>> profiling the time spent on .next() method (time to
>>>> consume) and
>>>> > > the
>>>> > > >>>>> time
>>>> > > >>>>>>>> spent on .collect() method (time to emit / process). One
>>>> > advantage
>>>> > > >> of
>>>> > > >>>>>>> such
>>>> > > >>>>>>>> method level time cost allows us to calculate the
>>>> parallelism
>>>> > > >>>>> required to
>>>> > > >>>>>>>> keep up in case their is a lag.
>>>> > > >>>>>>>>
>>>> > > >>>>>>>> However, one concern I have regarding such metric is that
>>>> they
>>>> > are
>>>> > > >>>>>>>> implementation specific. Either profiling on the method
>>>> time, or
>>>> > > >>>>>>> reporting
>>>> > > >>>>>>>> buffer usage assumes the connector are implemented in such
>>>> a
>>>> > way.
>>>> > > A
>>>> > > >>>>>>>> slightly better solution might be have the following
>>>> metric:
>>>> > > >>>>>>>>
>>>> > > >>>>>>>> - EmitTimeRatio (or FetchTimeRatio): The time spent on
>>>> emitting
>>>> > > >>>>>>>> records / Total time elapsed.
>>>> > > >>>>>>>>
>>>> > > >>>>>>>> This assumes that the source connectors have to emit the
>>>> records
>>>> > > to
>>>> > > >>>>> the
>>>> > > >>>>>>>> downstream at some point. The emission may take some time
>>>> ( e.g.
>>>> > > go
>>>> > > >>>>>>> through
>>>> > > >>>>>>>> chained operators). And the rest of the time are spent to
>>>> > prepare
>>>> > > >> the
>>>> > > >>>>>>>> record to emit, including time for consuming and format
>>>> > > conversion,
>>>> > > >>>>> etc.
>>>> > > >>>>>>>> Ideally, we'd like to see the time spent on record fetch
>>>> and
>>>> > emit
>>>> > > to
>>>> > > >>>>> be
>>>> > > >>>>>>>> about the same, so no one is bottleneck for the other.
>>>> > > >>>>>>>>
>>>> > > >>>>>>>> The downside of these time based metrics is additional
>>>> overhead
>>>> > to
>>>> > > >> get
>>>> > > >>>>>>> the
>>>> > > >>>>>>>> time, therefore sampling might be needed. But in practice
>>>> I feel
>>>> > > >> such
>>>> > > >>>>>>> time
>>>> > > >>>>>>>> based metric might be more useful if we want to take
>>>> action.
>>>> > > >>>>>>>>
>>>> > > >>>>>>>>
>>>> > > >>>>>>>> I think we should absolutely add metrics in (1) to the
>>>> metric
>>>> > > >>>>> convention.
>>>> > > >>>>>>>> We could also add the metrics mentioned in (2) if we reach
>>>> > > consensus
>>>> > > >>>>> on
>>>> > > >>>>>>>> that. What do you think?
>>>> > > >>>>>>>>
>>>> > > >>>>>>>> Thanks,
>>>> > > >>>>>>>>
>>>> > > >>>>>>>> Jiangjie (Becket) Qin
>>>> > > >>>>>>>>
>>>> > > >>>>>>>>
>>>> > > >>>>>>>> On Fri, May 31, 2019 at 4:26 PM Piotr Nowojski <
>>>> > > piotr@ververica.com
>>>> > > >>>
>>>> > > >>>>>>> wrote:
>>>> > > >>>>>>>>
>>>> > > >>>>>>>>> Hey Becket,
>>>> > > >>>>>>>>>
>>>> > > >>>>>>>>> Re 1a) and 1b) +1 from my side.
>>>> > > >>>>>>>>>
>>>> > > >>>>>>>>> I’ve discussed this issue:
>>>> > > >>>>>>>>>
>>>> > > >>>>>>>>>>>>
>>>> > > >>>>>>>>>>>> 2. It would be nice to have metrics, that allow us to
>>>> check
>>>> > > the
>>>> > > >>>>> cause
>>>> > > >>>>>>>>> of
>>>> > > >>>>>>>>>>>> back pressure:
>>>> > > >>>>>>>>>>>> a) for sources, length of input queue (in bytes? Or
>>>> boolean
>>>> > > >>>>>>>>>>>> hasSomethingl/isEmpty)
>>>> > > >>>>>>>>>>>> b) for sinks, length of output queue (in bytes? Or
>>>> boolean
>>>> > > >>>>>>>>>>>> hasSomething/isEmpty)
>>>> > > >>>>>>>>>
>>>> > > >>>>>>>>> With Nico at some lengths and he also saw the benefits of
>>>> them.
>>>> > > We
>>>> > > >>>>> also
>>>> > > >>>>>>>>> have more concrete proposal for that.
>>>> > > >>>>>>>>>
>>>> > > >>>>>>>>> Actually there are two really useful metrics, that we are
>>>> > missing
>>>> > > >>>>>>>>> currently:
>>>> > > >>>>>>>>>
>>>> > > >>>>>>>>> 1. Number of data/records/bytes in the backlog to
>>>> process. For
>>>> > > >>>>> example
>>>> > > >>>>>>>>> remaining number of bytes in unread files. Or pending
>>>> data in
>>>> > > Kafka
>>>> > > >>>>>>> topics.
>>>> > > >>>>>>>>> 2. Number of buffered data in-memory of the connector,
>>>> that are
>>>> > > >>>>> waiting
>>>> > > >>>>>>> to
>>>> > > >>>>>>>>> be processed pushed to Flink pipeline.
>>>> > > >>>>>>>>>
>>>> > > >>>>>>>>> Re 1:
>>>> > > >>>>>>>>> This would have to be a metric provided directly by a
>>>> > connector.
>>>> > > It
>>>> > > >>>>>>> could
>>>> > > >>>>>>>>> be an undefined `int`:
>>>> > > >>>>>>>>>
>>>> > > >>>>>>>>> `int backlog` - estimate of pending work.
>>>> > > >>>>>>>>>
>>>> > > >>>>>>>>> “Undefined” meaning that it would be up to a connector to
>>>> > decided
>>>> > > >>>>>>> whether
>>>> > > >>>>>>>>> it’s measured in bytes, records, pending files or
>>>> whatever it
>>>> > is
>>>> > > >>>>>>> possible
>>>> > > >>>>>>>>> to provide by the connector. This is because I assume not
>>>> every
>>>> > > >>>>>>> connector
>>>> > > >>>>>>>>> can provide exact number and for some of them it might be
>>>> > > >> impossible
>>>> > > >>>>> to
>>>> > > >>>>>>>>> provide records number of bytes count.
>>>> > > >>>>>>>>>
>>>> > > >>>>>>>>> Re 2:
>>>> > > >>>>>>>>> This metric could be either provided by a connector, or
>>>> > > calculated
>>>> > > >>>>>>> crudely
>>>> > > >>>>>>>>> by Flink:
>>>> > > >>>>>>>>>
>>>> > > >>>>>>>>> `float bufferUsage` - value from [0.0, 1.0] range
>>>> > > >>>>>>>>>
>>>> > > >>>>>>>>> Percentage of used in memory buffers, like in Kafka’s
>>>> handover.
>>>> > > >>>>>>>>>
>>>> > > >>>>>>>>> It could be crudely implemented by Flink with FLIP-27
>>>> > > >>>>>>>>> SourceReader#isAvailable. If SourceReader is not available
>>>> > > reported
>>>> > > >>>>>>>>> `bufferUsage` could be 0.0. If it is available, it could
>>>> be
>>>> > 1.0.
>>>> > > I
>>>> > > >>>>> think
>>>> > > >>>>>>>>> this would be a good enough estimation for most of the use
>>>> > cases
>>>> > > >>>>> (that
>>>> > > >>>>>>>>> could be overloaded and implemented better if desired).
>>>> > > Especially
>>>> > > >>>>>>> since we
>>>> > > >>>>>>>>> are reporting only probed values: if probed values are
>>>> almost
>>>> > > >> always
>>>> > > >>>>>>> “1.0”,
>>>> > > >>>>>>>>> it would mean that we have a back pressure. If they are
>>>> almost
>>>> > > >> always
>>>> > > >>>>>>>>> “0.0”, there is probably no back pressure at the sources.
>>>> > > >>>>>>>>>
>>>> > > >>>>>>>>> What do you think about this?
>>>> > > >>>>>>>>>
>>>> > > >>>>>>>>> Piotrek
>>>> > > >>>>>>>>>
>>>> > > >>>>>>>>>> On 30 May 2019, at 11:41, Becket Qin <
>>>> becket.qin@gmail.com>
>>>> > > >> wrote:
>>>> > > >>>>>>>>>>
>>>> > > >>>>>>>>>> Hi all,
>>>> > > >>>>>>>>>>
>>>> > > >>>>>>>>>> Thanks a lot for all the feedback and comments. I'd like
>>>> to
>>>> > > >> continue
>>>> > > >>>>>>> the
>>>> > > >>>>>>>>>> discussion on this FLIP.
>>>> > > >>>>>>>>>>
>>>> > > >>>>>>>>>> I updated the FLIP-33 wiki to remove all the histogram
>>>> metrics
>>>> > > >> from
>>>> > > >>>>> the
>>>> > > >>>>>>>>>> first version of metric convention due to the performance
>>>> > > concern.
>>>> > > >>>>> The
>>>> > > >>>>>>>>> plan
>>>> > > >>>>>>>>>> is to introduce them later when we have a mechanism to
>>>> opt
>>>> > > in/out
>>>> > > >>>>>>>>> metrics.
>>>> > > >>>>>>>>>> At that point, users can decide whether they want to pay
>>>> the
>>>> > > cost
>>>> > > >> to
>>>> > > >>>>>>> get
>>>> > > >>>>>>>>>> the metric or not.
>>>> > > >>>>>>>>>>
>>>> > > >>>>>>>>>> As Stephan suggested, for this FLIP, let's first try to
>>>> agree
>>>> > on
>>>> > > >> the
>>>> > > >>>>>>>>> small
>>>> > > >>>>>>>>>> list of conventional metrics that connectors should
>>>> follow.
>>>> > > >>>>>>>>>> Just to be clear, the purpose of the convention is not to
>>>> > > enforce
>>>> > > >>>>> every
>>>> > > >>>>>>>>>> connector to report all these metrics, but to provide a
>>>> > guidance
>>>> > > >> in
>>>> > > >>>>>>> case
>>>> > > >>>>>>>>>> these metrics are reported by some connectors.
>>>> > > >>>>>>>>>>
>>>> > > >>>>>>>>>>
>>>> > > >>>>>>>>>> @ Stephan & Chesnay,
>>>> > > >>>>>>>>>>
>>>> > > >>>>>>>>>> Regarding the duplication of `RecordsIn` metric in
>>>> operator /
>>>> > > task
>>>> > > >>>>>>>>>> IOMetricGroups, from what I understand, for source
>>>> operator,
>>>> > it
>>>> > > is
>>>> > > >>>>>>>>> actually
>>>> > > >>>>>>>>>> the SourceFunction that reports the operator level
>>>> > > >>>>>>>>>> RecordsIn/RecordsInPerSecond metric. So they are
>>>> essentially
>>>> > the
>>>> > > >>>>> same
>>>> > > >>>>>>>>>> metric in the operator level IOMetricGroup. Similarly
>>>> for the
>>>> > > Sink
>>>> > > >>>>>>>>>> operator, the operator level
>>>> RecordsOut/RecordsOutPerSecond
>>>> > > >> metrics
>>>> > > >>>>> are
>>>> > > >>>>>>>>>> also reported by the Sink function. I marked them as
>>>> existing
>>>> > in
>>>> > > >> the
>>>> > > >>>>>>>>>> FLIP-33 wiki page. Please let me know if I misunderstood.
>>>> > > >>>>>>>>>>
>>>> > > >>>>>>>>>> Thanks,
>>>> > > >>>>>>>>>>
>>>> > > >>>>>>>>>> Jiangjie (Becket) Qin
>>>> > > >>>>>>>>>>
>>>> > > >>>>>>>>>>
>>>> > > >>>>>>>>>> On Thu, May 30, 2019 at 5:16 PM Becket Qin <
>>>> > > becket.qin@gmail.com>
>>>> > > >>>>>>> wrote:
>>>> > > >>>>>>>>>>
>>>> > > >>>>>>>>>>> Hi Piotr,
>>>> > > >>>>>>>>>>>
>>>> > > >>>>>>>>>>> Thanks a lot for the feedback.
>>>> > > >>>>>>>>>>>
>>>> > > >>>>>>>>>>> 1a) I guess you are referring to the part that "original
>>>> > system
>>>> > > >>>>>>> specific
>>>> > > >>>>>>>>>>> metrics should also be reported". The performance impact
>>>> > > depends
>>>> > > >> on
>>>> > > >>>>>>> the
>>>> > > >>>>>>>>>>> implementation. An efficient implementation would only
>>>> record
>>>> > > the
>>>> > > >>>>>>> metric
>>>> > > >>>>>>>>>>> once, but report them with two different metric names.
>>>> This
>>>> > is
>>>> > > >>>>>>> unlikely
>>>> > > >>>>>>>>> to
>>>> > > >>>>>>>>>>> hurt performance.
>>>> > > >>>>>>>>>>>
>>>> > > >>>>>>>>>>> 1b) Yes, I agree that we should avoid adding overhead
>>>> to the
>>>> > > >>>>> critical
>>>> > > >>>>>>>>> path
>>>> > > >>>>>>>>>>> by all means. This is sometimes a tradeoff, running
>>>> blindly
>>>> > > >> without
>>>> > > >>>>>>> any
>>>> > > >>>>>>>>>>> metric gives best performance, but sometimes might be
>>>> > > frustrating
>>>> > > >>>>> when
>>>> > > >>>>>>>>> we
>>>> > > >>>>>>>>>>> debug some issues.
>>>> > > >>>>>>>>>>>
>>>> > > >>>>>>>>>>> 2. The metrics are indeed very useful. Are they
>>>> supposed to
>>>> > be
>>>> > > >>>>>>> reported
>>>> > > >>>>>>>>> by
>>>> > > >>>>>>>>>>> the connectors or Flink itself? At this point FLIP-33
>>>> is more
>>>> > > >>>>> focused
>>>> > > >>>>>>> on
>>>> > > >>>>>>>>>>> provide a guidance to the connector authors on the
>>>> metrics
>>>> > > >>>>> reporting.
>>>> > > >>>>>>>>> That
>>>> > > >>>>>>>>>>> said, after FLIP-27, I think we should absolutely report
>>>> > these
>>>> > > >>>>> metrics
>>>> > > >>>>>>>>> in
>>>> > > >>>>>>>>>>> the abstract implementation. In any case, the metric
>>>> > convention
>>>> > > >> in
>>>> > > >>>>>>> this
>>>> > > >>>>>>>>>>> list are expected to evolve over time.
>>>> > > >>>>>>>>>>>
>>>> > > >>>>>>>>>>> Thanks,
>>>> > > >>>>>>>>>>>
>>>> > > >>>>>>>>>>> Jiangjie (Becket) Qin
>>>> > > >>>>>>>>>>>
>>>> > > >>>>>>>>>>> On Tue, May 28, 2019 at 6:24 PM Piotr Nowojski <
>>>> > > >>>>> piotr@ververica.com>
>>>> > > >>>>>>>>>>> wrote:
>>>> > > >>>>>>>>>>>
>>>> > > >>>>>>>>>>>> Hi,
>>>> > > >>>>>>>>>>>>
>>>> > > >>>>>>>>>>>> Thanks for the proposal and driving the effort here
>>>> Becket
>>>> > :)
>>>> > > >> I’ve
>>>> > > >>>>>>> read
>>>> > > >>>>>>>>>>>> through the FLIP-33 [1], and here are couple of my
>>>> thoughts.
>>>> > > >>>>>>>>>>>>
>>>> > > >>>>>>>>>>>> Big +1 for standardising the metric names between
>>>> > connectors,
>>>> > > it
>>>> > > >>>>> will
>>>> > > >>>>>>>>>>>> definitely help us and users a lot.
>>>> > > >>>>>>>>>>>>
>>>> > > >>>>>>>>>>>> Issues/questions/things to discuss that I’ve thought
>>>> of:
>>>> > > >>>>>>>>>>>>
>>>> > > >>>>>>>>>>>> 1a. If we are about to duplicate some metrics, can this
>>>> > > become a
>>>> > > >>>>>>>>>>>> performance issue?
>>>> > > >>>>>>>>>>>> 1b. Generally speaking, we should make sure that
>>>> collecting
>>>> > > >> those
>>>> > > >>>>>>>>> metrics
>>>> > > >>>>>>>>>>>> is as non intrusive as possible, especially that they
>>>> will
>>>> > > need
>>>> > > >>>>> to be
>>>> > > >>>>>>>>>>>> updated once per record. (They might be collected more
>>>> > rarely
>>>> > > >> with
>>>> > > >>>>>>> some
>>>> > > >>>>>>>>>>>> overhead, but the hot path of updating it per record
>>>> will
>>>> > need
>>>> > > >> to
>>>> > > >>>>> be
>>>> > > >>>>>>> as
>>>> > > >>>>>>>>>>>> quick as possible). That includes both avoiding heavy
>>>> > > >> computation
>>>> > > >>>>> on
>>>> > > >>>>>>>>> per
>>>> > > >>>>>>>>>>>> record path: histograms?, measuring time for time based
>>>> > > metrics
>>>> > > >>>>> (per
>>>> > > >>>>>>>>>>>> second) (System.currentTimeMillis() depending on the
>>>> > > >>>>> implementation
>>>> > > >>>>>>> can
>>>> > > >>>>>>>>>>>> invoke a system call)
>>>> > > >>>>>>>>>>>>
>>>> > > >>>>>>>>>>>> 2. It would be nice to have metrics, that allow us to
>>>> check
>>>> > > the
>>>> > > >>>>> cause
>>>> > > >>>>>>>>> of
>>>> > > >>>>>>>>>>>> back pressure:
>>>> > > >>>>>>>>>>>> a) for sources, length of input queue (in bytes? Or
>>>> boolean
>>>> > > >>>>>>>>>>>> hasSomethingl/isEmpty)
>>>> > > >>>>>>>>>>>> b) for sinks, length of output queue (in bytes? Or
>>>> boolean
>>>> > > >>>>>>>>>>>> hasSomething/isEmpty)
>>>> > > >>>>>>>>>>>>
>>>> > > >>>>>>>>>>>> a) is useful in a scenario when we are processing
>>>> backlog of
>>>> > > >>>>> records,
>>>> > > >>>>>>>>> all
>>>> > > >>>>>>>>>>>> of the internal Flink’s input/output network buffers
>>>> are
>>>> > > empty,
>>>> > > >>>>> and
>>>> > > >>>>>>> we
>>>> > > >>>>>>>>> want
>>>> > > >>>>>>>>>>>> to check whether the external source system is the
>>>> > bottleneck
>>>> > > >>>>>>> (source’s
>>>> > > >>>>>>>>>>>> input queue will be empty), or if the Flink’s
>>>> connector is
>>>> > the
>>>> > > >>>>>>>>> bottleneck
>>>> > > >>>>>>>>>>>> (source’s input queues will be full).
>>>> > > >>>>>>>>>>>> b) similar story. Backlog of records, but this time
>>>> all of
>>>> > the
>>>> > > >>>>>>> internal
>>>> > > >>>>>>>>>>>> Flink’s input/ouput network buffers are full, and we
>>>> want o
>>>> > > >> check
>>>> > > >>>>>>>>> whether
>>>> > > >>>>>>>>>>>> the external sink system is the bottleneck (sink output
>>>> > queues
>>>> > > >> are
>>>> > > >>>>>>>>> full),
>>>> > > >>>>>>>>>>>> or if the Flink’s connector is the bottleneck (sink’s
>>>> output
>>>> > > >>>>> queues
>>>> > > >>>>>>>>> will be
>>>> > > >>>>>>>>>>>> empty)
>>>> > > >>>>>>>>>>>>
>>>> > > >>>>>>>>>>>> It might be sometimes difficult to provide those
>>>> metrics, so
>>>> > > >> they
>>>> > > >>>>>>> could
>>>> > > >>>>>>>>>>>> be optional, but if we could provide them, it would be
>>>> > really
>>>> > > >>>>>>> helpful.
>>>> > > >>>>>>>>>>>>
>>>> > > >>>>>>>>>>>> Piotrek
>>>> > > >>>>>>>>>>>>
>>>> > > >>>>>>>>>>>> [1]
>>>> > > >>>>>>>>>>>>
>>>> > > >>>>>>>>>
>>>> > > >>>>>>>
>>>> > > >>>>>
>>>> > > >>
>>>> > >
>>>> >
>>>> https://cwiki.apache.org/confluence/display/FLINK/FLIP-33:+Standardize+Connector+Metrics
>>>> > > >>>>>>>>>>>> <
>>>> > > >>>>>>>>>>>>
>>>> > > >>>>>>>>>
>>>> > > >>>>>>>
>>>> > > >>>>>
>>>> > > >>
>>>> > >
>>>> >
>>>> https://cwiki.apache.org/confluence/display/FLINK/FLIP-33:+Standardize+Connector+Metrics
>>>> > > >>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>> On 24 Apr 2019, at 13:28, Stephan Ewen <
>>>> sewen@apache.org>
>>>> > > >> wrote:
>>>> > > >>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>> I think this sounds reasonable.
>>>> > > >>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>> Let's keep the "reconfiguration without stopping the
>>>> job"
>>>> > out
>>>> > > >> of
>>>> > > >>>>>>> this,
>>>> > > >>>>>>>>>>>>> because that would be a super big effort and if we
>>>> approach
>>>> > > >> that,
>>>> > > >>>>>>> then
>>>> > > >>>>>>>>>>>> in
>>>> > > >>>>>>>>>>>>> more generic way rather than specific to connector
>>>> metrics.
>>>> > > >>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>> I would suggest to look at the following things before
>>>> > > starting
>>>> > > >>>>> with
>>>> > > >>>>>>>>> any
>>>> > > >>>>>>>>>>>>> implementation work:
>>>> > > >>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>> - Try and find a committer to support this, otherwise
>>>> it
>>>> > will
>>>> > > >> be
>>>> > > >>>>>>> hard
>>>> > > >>>>>>>>>>>> to
>>>> > > >>>>>>>>>>>>> make progress
>>>> > > >>>>>>>>>>>>> - Start with defining a smaller set of "core metrics"
>>>> and
>>>> > > >> extend
>>>> > > >>>>> the
>>>> > > >>>>>>>>>>>> set
>>>> > > >>>>>>>>>>>>> later. I think that is easier than now blocking on
>>>> reaching
>>>> > > >>>>>>> consensus
>>>> > > >>>>>>>>>>>> on a
>>>> > > >>>>>>>>>>>>> large group of metrics.
>>>> > > >>>>>>>>>>>>> - Find a solution to the problem Chesnay mentioned,
>>>> that
>>>> > the
>>>> > > >>>>>>> "records
>>>> > > >>>>>>>>>>>> in"
>>>> > > >>>>>>>>>>>>> metric is somehow overloaded and exists already in
>>>> the IO
>>>> > > >> Metric
>>>> > > >>>>>>>>> group.
>>>> > > >>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>> On Mon, Mar 25, 2019 at 7:16 AM Becket Qin <
>>>> > > >> becket.qin@gmail.com
>>>> > > >>>>>>
>>>> > > >>>>>>>>>>>> wrote:
>>>> > > >>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>> Hi Stephan,
>>>> > > >>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>> Thanks a lot for the feedback. All makes sense.
>>>> > > >>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>> It is a good suggestion to simply have an
>>>> > onRecord(numBytes,
>>>> > > >>>>>>>>> eventTime)
>>>> > > >>>>>>>>>>>>>> method for connector writers. It should meet most of
>>>> the
>>>> > > >>>>>>>>> requirements,
>>>> > > >>>>>>>>>>>>>> individual
>>>> > > >>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>> The configurable metrics feature is something really
>>>> > useful,
>>>> > > >>>>>>>>>>>> especially if
>>>> > > >>>>>>>>>>>>>> we can somehow make it dynamically configurable
>>>> without
>>>> > > >> stopping
>>>> > > >>>>>>> the
>>>> > > >>>>>>>>>>>> jobs.
>>>> > > >>>>>>>>>>>>>> It might be better to make it a separate discussion
>>>> > because
>>>> > > it
>>>> > > >>>>> is a
>>>> > > >>>>>>>>>>>> more
>>>> > > >>>>>>>>>>>>>> generic feature instead of only for connectors.
>>>> > > >>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>> So in order to make some progress, in this FLIP we
>>>> can
>>>> > limit
>>>> > > >> the
>>>> > > >>>>>>>>>>>> discussion
>>>> > > >>>>>>>>>>>>>> scope to the connector related items:
>>>> > > >>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>> - the standard connector metric names and types.
>>>> > > >>>>>>>>>>>>>> - the abstract ConnectorMetricHandler interface
>>>> > > >>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>> I'll start a separate thread to discuss other general
>>>> > metric
>>>> > > >>>>>>> related
>>>> > > >>>>>>>>>>>>>> enhancement items including:
>>>> > > >>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>> - optional metrics
>>>> > > >>>>>>>>>>>>>> - dynamic metric configuration
>>>> > > >>>>>>>>>>>>>> - potential combination with rate limiter
>>>> > > >>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>> Does this plan sound reasonable?
>>>> > > >>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>> Thanks,
>>>> > > >>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>> Jiangjie (Becket) Qin
>>>> > > >>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>> On Sat, Mar 23, 2019 at 5:53 AM Stephan Ewen <
>>>> > > >> sewen@apache.org>
>>>> > > >>>>>>>>> wrote:
>>>> > > >>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>> Ignoring for a moment implementation details, this
>>>> > > connector
>>>> > > >>>>>>> metrics
>>>> > > >>>>>>>>>>>> work
>>>> > > >>>>>>>>>>>>>>> is a really good thing to do, in my opinion
>>>> > > >>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>> The questions "oh, my job seems to be doing
>>>> nothing, I am
>>>> > > >>>>> looking
>>>> > > >>>>>>> at
>>>> > > >>>>>>>>>>>> the
>>>> > > >>>>>>>>>>>>>> UI
>>>> > > >>>>>>>>>>>>>>> and the 'records in' value is still zero" is in the
>>>> top
>>>> > > three
>>>> > > >>>>>>>>> support
>>>> > > >>>>>>>>>>>>>>> questions I have been asked personally.
>>>> > > >>>>>>>>>>>>>>> Introspection into "how far is the consumer lagging
>>>> > behind"
>>>> > > >>>>> (event
>>>> > > >>>>>>>>>>>> time
>>>> > > >>>>>>>>>>>>>>> fetch latency) came up many times as well.
>>>> > > >>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>> So big +1 to solving this problem.
>>>> > > >>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>> About the exact design - I would try to go for the
>>>> > > following
>>>> > > >>>>>>>>>>>> properties:
>>>> > > >>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>> - keep complexity of of connectors. Ideally the
>>>> metrics
>>>> > > >> handler
>>>> > > >>>>>>> has
>>>> > > >>>>>>>>> a
>>>> > > >>>>>>>>>>>>>>> single onRecord(numBytes, eventTime) method or so,
>>>> and
>>>> > > >>>>> everything
>>>> > > >>>>>>>>>>>> else is
>>>> > > >>>>>>>>>>>>>>> internal to the handler. That makes it dead simple
>>>> for
>>>> > the
>>>> > > >>>>>>>>> connector.
>>>> > > >>>>>>>>>>>> We
>>>> > > >>>>>>>>>>>>>>> can also think of an extensive scheme for connector
>>>> > > specific
>>>> > > >>>>>>>>> metrics.
>>>> > > >>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>> - make it configurable on the job it cluster level
>>>> which
>>>> > > >>>>> metrics
>>>> > > >>>>>>> the
>>>> > > >>>>>>>>>>>>>>> handler internally creates when that method is
>>>> invoked.
>>>> > > >>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>> What do you think?
>>>> > > >>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>> Best,
>>>> > > >>>>>>>>>>>>>>> Stephan
>>>> > > >>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>> On Thu, Mar 21, 2019 at 10:42 AM Chesnay Schepler <
>>>> > > >>>>>>>>> chesnay@apache.org
>>>> > > >>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>> wrote:
>>>> > > >>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>> As I said before, I believe this to be
>>>> over-engineered
>>>> > and
>>>> > > >>>>> have
>>>> > > >>>>>>> no
>>>> > > >>>>>>>>>>>>>>>> interest in this implementation.
>>>> > > >>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>> There are conceptual issues like defining a
>>>> duplicate
>>>> > > >>>>>>>>>>>>>> numBytesIn(PerSec)
>>>> > > >>>>>>>>>>>>>>>> metric that already exists for each operator.
>>>> > > >>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>> On 21.03.2019 06:13, Becket Qin wrote:
>>>> > > >>>>>>>>>>>>>>>>> A few updates to the thread. I uploaded a
>>>> patch[1] as a
>>>> > > >>>>> complete
>>>> > > >>>>>>>>>>>>>>>>> example of how users can use the metrics in the
>>>> future.
>>>> > > >>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>> Some thoughts below after taking a look at the
>>>> > > >>>>>>> AbstractMetricGroup
>>>> > > >>>>>>>>>>>>>> and
>>>> > > >>>>>>>>>>>>>>>>> its subclasses.
>>>> > > >>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>> This patch intends to provide convenience for
>>>> Flink
>>>> > > >> connector
>>>> > > >>>>>>>>>>>>>>>>> implementations to follow metrics standards
>>>> proposed in
>>>> > > >>>>> FLIP-33.
>>>> > > >>>>>>>>> It
>>>> > > >>>>>>>>>>>>>>>>> also try to enhance the metric management in
>>>> general
>>>> > way
>>>> > > to
>>>> > > >>>>> help
>>>> > > >>>>>>>>>>>>>> users
>>>> > > >>>>>>>>>>>>>>>>> with:
>>>> > > >>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>> 1. metric definition
>>>> > > >>>>>>>>>>>>>>>>> 2. metric dependencies check
>>>> > > >>>>>>>>>>>>>>>>> 3. metric validation
>>>> > > >>>>>>>>>>>>>>>>> 4. metric control (turn on / off particular
>>>> metrics)
>>>> > > >>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>> This patch wraps |MetricGroup| to extend the
>>>> > > functionality
>>>> > > >> of
>>>> > > >>>>>>>>>>>>>>>>> |AbstractMetricGroup| and its subclasses. The
>>>> > > >>>>>>>>>>>>>>>>> |AbstractMetricGroup| mainly focus on the metric
>>>> group
>>>> > > >>>>>>> hierarchy,
>>>> > > >>>>>>>>>>>> but
>>>> > > >>>>>>>>>>>>>>>>> does not really manage the metrics other than
>>>> keeping
>>>> > > them
>>>> > > >>>>> in a
>>>> > > >>>>>>>>> Map.
>>>> > > >>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>> Ideally we should only have one entry point for
>>>> the
>>>> > > >> metrics.
>>>> > > >>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>> Right now the entry point is
>>>> |AbstractMetricGroup|.
>>>> > > >> However,
>>>> > > >>>>>>>>> besides
>>>> > > >>>>>>>>>>>>>>>>> the missing functionality mentioned above,
>>>> > > >>>>> |AbstractMetricGroup|
>>>> > > >>>>>>>>>>>>>> seems
>>>> > > >>>>>>>>>>>>>>>>> deeply rooted in Flink runtime. We could extract
>>>> it out
>>>> > > to
>>>> > > >>>>>>>>>>>>>>>>> flink-metrics in order to use it for generic
>>>> purpose.
>>>> > > There
>>>> > > >>>>> will
>>>> > > >>>>>>>>> be
>>>> > > >>>>>>>>>>>>>>>>> some work, though.
>>>> > > >>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>> Another approach is to make |AbstractMetrics| in
>>>> this
>>>> > > patch
>>>> > > >>>>> as
>>>> > > >>>>>>> the
>>>> > > >>>>>>>>>>>>>>>>> metric entry point. It wraps metric group and
>>>> provides
>>>> > > the
>>>> > > >>>>>>> missing
>>>> > > >>>>>>>>>>>>>>>>> functionalities. Then we can roll out this
>>>> pattern to
>>>> > > >> runtime
>>>> > > >>>>>>>>>>>>>>>>> components gradually as well.
>>>> > > >>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>> My first thought is that the latter approach
>>>> gives a
>>>> > more
>>>> > > >>>>> smooth
>>>> > > >>>>>>>>>>>>>>>>> migration. But I am also OK with doing a
>>>> refactoring on
>>>> > > the
>>>> > > >>>>>>>>>>>>>>>>> |AbstractMetricGroup| family.
>>>> > > >>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>> Thanks,
>>>> > > >>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>> Jiangjie (Becket) Qin
>>>> > > >>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>> [1] https://github.com/becketqin/flink/pull/1
>>>> > > >>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>> On Mon, Feb 25, 2019 at 2:32 PM Becket Qin <
>>>> > > >>>>>>> becket.qin@gmail.com
>>>> > > >>>>>>>>>>>>>>>>> <ma...@gmail.com>> wrote:
>>>> > > >>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>> Hi Chesnay,
>>>> > > >>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>> It might be easier to discuss some implementation
>>>> > details
>>>> > > >> in
>>>> > > >>>>>>> the
>>>> > > >>>>>>>>>>>>>>>>> PR review instead of in the FLIP discussion
>>>> thread. I
>>>> > > have
>>>> > > >> a
>>>> > > >>>>>>>>>>>>>> patch
>>>> > > >>>>>>>>>>>>>>>>> for Kafka connectors ready but haven't submitted
>>>> the PR
>>>> > > >> yet.
>>>> > > >>>>>>>>>>>>>>>>> Hopefully that will help explain a bit more.
>>>> > > >>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>> ** Re: metric type binding
>>>> > > >>>>>>>>>>>>>>>>> This is a valid point that worths discussing. If I
>>>> > > >> understand
>>>> > > >>>>>>>>>>>>>>>>> correctly, there are two points:
>>>> > > >>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>> 1. Metric type / interface does not matter as
>>>> long as
>>>> > the
>>>> > > >>>>>>> metric
>>>> > > >>>>>>>>>>>>>>>>> semantic is clearly defined.
>>>> > > >>>>>>>>>>>>>>>>> Conceptually speaking, I agree that as long as the
>>>> > metric
>>>> > > >>>>>>>>>>>>>> semantic
>>>> > > >>>>>>>>>>>>>>>>> is defined, metric type does not matter. To some
>>>> > extent,
>>>> > > >>>>> Gauge
>>>> > > >>>>>>> /
>>>> > > >>>>>>>>>>>>>>>>> Counter / Meter / Histogram themselves can be
>>>> think of
>>>> > as
>>>> > > >>>>> some
>>>> > > >>>>>>>>>>>>>>>>> well-recognized semantics, if you wish. In Flink,
>>>> these
>>>> > > >>>>> metric
>>>> > > >>>>>>>>>>>>>>>>> semantics have their associated interface
>>>> classes. In
>>>> > > >>>>> practice,
>>>> > > >>>>>>>>>>>>>>>>> such semantic to interface binding seems
>>>> necessary for
>>>> > > >>>>>>> different
>>>> > > >>>>>>>>>>>>>>>>> components to communicate. Simply standardize the
>>>> > > semantic
>>>> > > >>>>> of
>>>> > > >>>>>>>>>>>>>> the
>>>> > > >>>>>>>>>>>>>>>>> connector metrics seems not sufficient for people
>>>> to
>>>> > > build
>>>> > > >>>>>>>>>>>>>>>>> ecosystem on top of. At the end of the day, we
>>>> still
>>>> > need
>>>> > > >> to
>>>> > > >>>>>>>>> have
>>>> > > >>>>>>>>>>>>>>>>> some embodiment of the metric semantics that
>>>> people can
>>>> > > >>>>> program
>>>> > > >>>>>>>>>>>>>>>>> against.
>>>> > > >>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>> 2. Sometimes the same metric semantic can be
>>>> exposed
>>>> > > using
>>>> > > >>>>>>>>>>>>>>>>> different metric types / interfaces.
>>>> > > >>>>>>>>>>>>>>>>> This is a good point. Counter and
>>>> Gauge-as-a-Counter
>>>> > are
>>>> > > >>>>> pretty
>>>> > > >>>>>>>>>>>>>>>>> much interchangeable. This is more of a trade-off
>>>> > between
>>>> > > >> the
>>>> > > >>>>>>>>>>>>>> user
>>>> > > >>>>>>>>>>>>>>>>> experience of metric producers and consumers. The
>>>> > metric
>>>> > > >>>>>>>>>>>>>> producers
>>>> > > >>>>>>>>>>>>>>>>> want to use Counter or Gauge depending on whether
>>>> the
>>>> > > >> counter
>>>> > > >>>>>>> is
>>>> > > >>>>>>>>>>>>>>>>> already tracked in code, while ideally the metric
>>>> > > consumers
>>>> > > >>>>>>> only
>>>> > > >>>>>>>>>>>>>>>>> want to see a single metric type for each metric.
>>>> I am
>>>> > > >>>>> leaning
>>>> > > >>>>>>>>>>>>>>>>> towards to make the metric producers happy, i.e.
>>>> allow
>>>> > > >> Gauge
>>>> > > >>>>> /
>>>> > > >>>>>>>>>>>>>>>>> Counter metric type, and the the metric consumers
>>>> > handle
>>>> > > >> the
>>>> > > >>>>>>>>> type
>>>> > > >>>>>>>>>>>>>>>>> variation. The reason is that in practice, there
>>>> might
>>>> > be
>>>> > > >>>>> more
>>>> > > >>>>>>>>>>>>>>>>> connector implementations than metric reporter
>>>> > > >>>>> implementations.
>>>> > > >>>>>>>>>>>>>> We
>>>> > > >>>>>>>>>>>>>>>>> could also provide some helper method to
>>>> facilitate
>>>> > > reading
>>>> > > >>>>>>> from
>>>> > > >>>>>>>>>>>>>>>>> such variable metric type.
>>>> > > >>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>> Just some quick replies to the comments around
>>>> > > >> implementation
>>>> > > >>>>>>>>>>>>>>>> details.
>>>> > > >>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>> 4) single place where metrics are registered
>>>> except
>>>> > > >>>>>>>>>>>>>>>>> connector-specific
>>>> > > >>>>>>>>>>>>>>>>> ones (which we can't really avoid).
>>>> > > >>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>> Register connector specific ones in a single
>>>> place is
>>>> > > >>>>> actually
>>>> > > >>>>>>>>>>>>>>>>> something that I want to achieve.
>>>> > > >>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>> 2) I'm talking about time-series databases like
>>>> > > >>>>> Prometheus.
>>>> > > >>>>>>>>>>>>>> We
>>>> > > >>>>>>>>>>>>>>>>> would
>>>> > > >>>>>>>>>>>>>>>>> only have a gauge metric exposing the last
>>>> > > >>>>>>>>> fetchTime/emitTime
>>>> > > >>>>>>>>>>>>>>>>> that is
>>>> > > >>>>>>>>>>>>>>>>> regularly reported to the backend (Prometheus),
>>>> > where a
>>>> > > >>>>>>> user
>>>> > > >>>>>>>>>>>>>>>>> could build
>>>> > > >>>>>>>>>>>>>>>>> a histogram of his choosing when/if he wants it.
>>>> > > >>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>> Not sure if such downsampling works. As an
>>>> example, if
>>>> > a
>>>> > > >> user
>>>> > > >>>>>>>>>>>>>>>>> complains that there are some intermittent latency
>>>> > spikes
>>>> > > >>>>>>> (maybe
>>>> > > >>>>>>>>>>>>>> a
>>>> > > >>>>>>>>>>>>>>>>> few records in 10 seconds) in their processing
>>>> system.
>>>> > > >>>>> Having a
>>>> > > >>>>>>>>>>>>>>>>> Gauge sampling instantaneous latency seems
>>>> unlikely
>>>> > > useful.
>>>> > > >>>>>>>>>>>>>>>>> However by looking at actual 99.9 percentile
>>>> latency
>>>> > > might
>>>> > > >>>>>>> help.
>>>> > > >>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>> Thanks,
>>>> > > >>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>> Jiangjie (Becket) Qin
>>>> > > >>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>> On Fri, Feb 22, 2019 at 9:30 PM Chesnay Schepler
>>>> > > >>>>>>>>>>>>>>>>> <chesnay@apache.org <ma...@apache.org>>
>>>> > wrote:
>>>> > > >>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>> Re: over complication of implementation.
>>>> > > >>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>> I think I get understand better know what you're
>>>> > > >> shooting
>>>> > > >>>>>>>>>>>>>> for,
>>>> > > >>>>>>>>>>>>>>>>> effectively something like the
>>>> OperatorIOMetricGroup.
>>>> > > >>>>>>>>>>>>>>>>> But still, re-define setupConnectorMetrics() to
>>>> > accept
>>>> > > a
>>>> > > >>>>>>> set
>>>> > > >>>>>>>>>>>>>>>>> of flags
>>>> > > >>>>>>>>>>>>>>>>> for counters/meters(ans _possibly_ histograms)
>>>> along
>>>> > > >>>>> with a
>>>> > > >>>>>>>>>>>>>>>>> set of
>>>> > > >>>>>>>>>>>>>>>>> well-defined Optional<Gauge<?>>, and return the
>>>> > group.
>>>> > > >>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>> Solves all issues as far as i can tell:
>>>> > > >>>>>>>>>>>>>>>>> 1) no metrics must be created manually (except
>>>> > Gauges,
>>>> > > >>>>>>> which
>>>> > > >>>>>>>>>>>>>>> are
>>>> > > >>>>>>>>>>>>>>>>> effectively just Suppliers and you can't get
>>>> around
>>>> > > >>>>> this),
>>>> > > >>>>>>>>>>>>>>>>> 2) additional metrics can be registered on the
>>>> > returned
>>>> > > >>>>>>>>>>>>>> group,
>>>> > > >>>>>>>>>>>>>>>>> 3) see 1),
>>>> > > >>>>>>>>>>>>>>>>> 4) single place where metrics are registered
>>>> except
>>>> > > >>>>>>>>>>>>>>>>> connector-specific
>>>> > > >>>>>>>>>>>>>>>>> ones (which we can't really avoid).
>>>> > > >>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>> Re: Histogram
>>>> > > >>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>> 1) As an example, whether "numRecordsIn" is
>>>> exposed
>>>> > as
>>>> > > a
>>>> > > >>>>>>>>>>>>>>>>> Counter or a
>>>> > > >>>>>>>>>>>>>>>>> Gauge should be irrelevant. So far we're using
>>>> the
>>>> > > >> metric
>>>> > > >>>>>>>>>>>>>> type
>>>> > > >>>>>>>>>>>>>>>>> that is
>>>> > > >>>>>>>>>>>>>>>>> the most convenient at exposing a given value.
>>>> If
>>>> > there
>>>> > > >>>>> is
>>>> > > >>>>>>>>>>>>>>>>> some backing
>>>> > > >>>>>>>>>>>>>>>>> data-structure that we want to expose some data
>>>> from
>>>> > we
>>>> > > >>>>>>>>>>>>>>>>> typically opt
>>>> > > >>>>>>>>>>>>>>>>> for a Gauge, as otherwise we're just mucking
>>>> around
>>>> > > with
>>>> > > >>>>>>> the
>>>> > > >>>>>>>>>>>>>>>>> Meter/Counter API to get it to match.
>>>> Similarly, if
>>>> > we
>>>> > > >>>>> want
>>>> > > >>>>>>>>>>>>>> to
>>>> > > >>>>>>>>>>>>>>>>> count
>>>> > > >>>>>>>>>>>>>>>>> something but no current count exists we
>>>> typically
>>>> > > added
>>>> > > >>>>> a
>>>> > > >>>>>>>>>>>>>>>>> Counter.
>>>> > > >>>>>>>>>>>>>>>>> That's why attaching semantics to metric types
>>>> makes
>>>> > > >>>>> little
>>>> > > >>>>>>>>>>>>>>>>> sense (but
>>>> > > >>>>>>>>>>>>>>>>> unfortunately several reporters already do it);
>>>> for
>>>> > > >>>>>>>>>>>>>>>>> counters/meters
>>>> > > >>>>>>>>>>>>>>>>> certainly, but the majority of metrics are
>>>> gauges.
>>>> > > >>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>> 2) I'm talking about time-series databases like
>>>> > > >>>>> Prometheus.
>>>> > > >>>>>>>>>>>>>> We
>>>> > > >>>>>>>>>>>>>>>>> would
>>>> > > >>>>>>>>>>>>>>>>> only have a gauge metric exposing the last
>>>> > > >>>>>>>>> fetchTime/emitTime
>>>> > > >>>>>>>>>>>>>>>>> that is
>>>> > > >>>>>>>>>>>>>>>>> regularly reported to the backend (Prometheus),
>>>> > where a
>>>> > > >>>>>>> user
>>>> > > >>>>>>>>>>>>>>>>> could build
>>>> > > >>>>>>>>>>>>>>>>> a histogram of his choosing when/if he wants it.
>>>> > > >>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>> On 22.02.2019 13:57, Becket Qin wrote:
>>>> > > >>>>>>>>>>>>>>>>>> Hi Chesnay,
>>>> > > >>>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>>> Thanks for the explanation.
>>>> > > >>>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>>> ** Re: FLIP
>>>> > > >>>>>>>>>>>>>>>>>> I might have misunderstood this, but it seems
>>>> that
>>>> > > "major
>>>> > > >>>>>>>>>>>>>>>>> changes" are well
>>>> > > >>>>>>>>>>>>>>>>>> defined in FLIP. The full contents is following:
>>>> > > >>>>>>>>>>>>>>>>>> What is considered a "major change" that needs a
>>>> FLIP?
>>>> > > >>>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>>> Any of the following should be considered a major
>>>> > > change:
>>>> > > >>>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>>> - Any major new feature, subsystem, or piece of
>>>> > > >>>>>>>>>>>>>>>>> functionality
>>>> > > >>>>>>>>>>>>>>>>>> - *Any change that impacts the public interfaces
>>>> of
>>>> > the
>>>> > > >>>>>>>>>>>>>>>>> project*
>>>> > > >>>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>>> What are the "public interfaces" of the project?
>>>> > > >>>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>>> *All of the following are public interfaces *that
>>>> > people
>>>> > > >>>>>>>>>>>>>>>>> build around:
>>>> > > >>>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>>> - DataStream and DataSet API, including classes
>>>> > related
>>>> > > >>>>>>>>>>>>>>>>> to that, such as
>>>> > > >>>>>>>>>>>>>>>>>> StreamExecutionEnvironment
>>>> > > >>>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>>> - Classes marked with the @Public annotation
>>>> > > >>>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>>> - On-disk binary formats, such as
>>>> > > >>>>>>>>>>>>>> checkpoints/savepoints
>>>> > > >>>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>>> - User-facing scripts/command-line tools, i.e.
>>>> > > >>>>>>>>>>>>>>>>> bin/flink, Yarn scripts,
>>>> > > >>>>>>>>>>>>>>>>>> Mesos scripts
>>>> > > >>>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>>> - Configuration settings
>>>> > > >>>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>>> - *Exposed monitoring information*
>>>> > > >>>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>>> So any monitoring information change is
>>>> considered as
>>>> > > >>>>>>>>>>>>>> public
>>>> > > >>>>>>>>>>>>>>>>> interface, and
>>>> > > >>>>>>>>>>>>>>>>>> any public interface change is considered as a
>>>> "major
>>>> > > >>>>>>>>>>>>>>> change".
>>>> > > >>>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>>> ** Re: over complication of implementation.
>>>> > > >>>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>>> Although this is more of implementation details
>>>> that
>>>> > is
>>>> > > >> not
>>>> > > >>>>>>>>>>>>>>>>> covered by the
>>>> > > >>>>>>>>>>>>>>>>>> FLIP. But it may be worth discussing.
>>>> > > >>>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>>> First of all, I completely agree that we should
>>>> use
>>>> > the
>>>> > > >>>>>>>>>>>>>>>>> simplest way to
>>>> > > >>>>>>>>>>>>>>>>>> achieve our goal. To me the goal is the
>>>> following:
>>>> > > >>>>>>>>>>>>>>>>>> 1. Clear connector conventions and interfaces.
>>>> > > >>>>>>>>>>>>>>>>>> 2. The easiness of creating a connector.
>>>> > > >>>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>>> Both of them are important to the prosperity of
>>>> the
>>>> > > >>>>>>>>>>>>>>>>> connector ecosystem. So
>>>> > > >>>>>>>>>>>>>>>>>> I'd rather abstract as much as possible on our
>>>> side to
>>>> > > >> make
>>>> > > >>>>>>>>>>>>>>>>> the connector
>>>> > > >>>>>>>>>>>>>>>>>> developer's work lighter. Given this goal, a
>>>> static
>>>> > util
>>>> > > >>>>>>>>>>>>>>>>> method approach
>>>> > > >>>>>>>>>>>>>>>>>> might have a few drawbacks:
>>>> > > >>>>>>>>>>>>>>>>>> 1. Users still have to construct the metrics by
>>>> > > >> themselves.
>>>> > > >>>>>>>>>>>>>>>>> (And note that
>>>> > > >>>>>>>>>>>>>>>>>> this might be erroneous by itself. For example, a
>>>> > > customer
>>>> > > >>>>>>>>>>>>>>>>> wrapper around
>>>> > > >>>>>>>>>>>>>>>>>> dropwizard meter maybe used instead of
>>>> MeterView).
>>>> > > >>>>>>>>>>>>>>>>>> 2. When connector specific metrics are added, it
>>>> is
>>>> > > >>>>>>>>>>>>>>>>> difficult to enforce
>>>> > > >>>>>>>>>>>>>>>>>> the scope to be the same as standard metrics.
>>>> > > >>>>>>>>>>>>>>>>>> 3. It seems that a method proliferation is
>>>> inevitable
>>>> > if
>>>> > > >> we
>>>> > > >>>>>>>>>>>>>>>>> want to apply
>>>> > > >>>>>>>>>>>>>>>>>> sanity checks. e.g. The metric of numBytesIn was
>>>> not
>>>> > > >>>>>>>>>>>>>>>>> registered for a meter.
>>>> > > >>>>>>>>>>>>>>>>>> 4. Metrics are still defined in random places
>>>> and hard
>>>> > > to
>>>> > > >>>>>>>>>>>>>>>> track.
>>>> > > >>>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>>> The current PR I had was inspired by the Config
>>>> system
>>>> > > in
>>>> > > >>>>>>>>>>>>>>>>> Kafka, which I
>>>> > > >>>>>>>>>>>>>>>>>> found pretty handy. In fact it is not only used
>>>> by
>>>> > Kafka
>>>> > > >>>>>>>>>>>>>>>>> itself but even
>>>> > > >>>>>>>>>>>>>>>>>> some other projects that depend on Kafka. I am
>>>> not
>>>> > > saying
>>>> > > >>>>>>>>>>>>>>>>> this approach is
>>>> > > >>>>>>>>>>>>>>>>>> perfect. But I think it worths to save the work
>>>> for
>>>> > > >>>>>>>>>>>>>>>>> connector writers and
>>>> > > >>>>>>>>>>>>>>>>>> encourage more systematic implementation. That
>>>> being
>>>> > > said,
>>>> > > >>>>>>>>>>>>>> I
>>>> > > >>>>>>>>>>>>>>>>> am fully open
>>>> > > >>>>>>>>>>>>>>>>>> to suggestions.
>>>> > > >>>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>>> Re: Histogram
>>>> > > >>>>>>>>>>>>>>>>>> I think there are two orthogonal questions around
>>>> > those
>>>> > > >>>>>>>>>>>>>>>> metrics:
>>>> > > >>>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>>> 1. Regardless of the metric type, by just
>>>> looking at
>>>> > the
>>>> > > >>>>>>>>>>>>>>>>> meaning of a
>>>> > > >>>>>>>>>>>>>>>>>> metric, is generic to all connectors? If the
>>>> answer is
>>>> > > >> yes,
>>>> > > >>>>>>>>>>>>>>>>> we should
>>>> > > >>>>>>>>>>>>>>>>>> include the metric into the convention. No matter
>>>> > > whether
>>>> > > >>>>>>>>>>>>>> we
>>>> > > >>>>>>>>>>>>>>>>> include it
>>>> > > >>>>>>>>>>>>>>>>>> into the convention or not, some connector
>>>> > > implementations
>>>> > > >>>>>>>>>>>>>>>>> will emit such
>>>> > > >>>>>>>>>>>>>>>>>> metric. It is better to have a convention than
>>>> letting
>>>> > > >> each
>>>> > > >>>>>>>>>>>>>>>>> connector do
>>>> > > >>>>>>>>>>>>>>>>>> random things.
>>>> > > >>>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>>> 2. If a standard metric is a histogram, what
>>>> should we
>>>> > > do?
>>>> > > >>>>>>>>>>>>>>>>>> I agree that we should make it clear that using
>>>> > > histograms
>>>> > > >>>>>>>>>>>>>>>>> will have
>>>> > > >>>>>>>>>>>>>>>>>> performance risk. But I do see histogram is
>>>> useful in
>>>> > > some
>>>> > > >>>>>>>>>>>>>>>>> fine-granularity
>>>> > > >>>>>>>>>>>>>>>>>> debugging where one do not have the luxury to
>>>> stop the
>>>> > > >>>>>>>>>>>>>>>>> system and inject
>>>> > > >>>>>>>>>>>>>>>>>> more inspection code. So the workaround I am
>>>> thinking
>>>> > is
>>>> > > >> to
>>>> > > >>>>>>>>>>>>>>>>> provide some
>>>> > > >>>>>>>>>>>>>>>>>> implementation suggestions. Assume later on we
>>>> have a
>>>> > > >>>>>>>>>>>>>>>>> mechanism of
>>>> > > >>>>>>>>>>>>>>>>>> selective metrics. In the abstract metrics class
>>>> we
>>>> > can
>>>> > > >>>>>>>>>>>>>>>>> disable those
>>>> > > >>>>>>>>>>>>>>>>>> metrics by default individual connector writers
>>>> does
>>>> > not
>>>> > > >>>>>>>>>>>>>>>>> have to do
>>>> > > >>>>>>>>>>>>>>>>>> anything (this is another advantage of having an
>>>> > > >>>>>>>>>>>>>>>>> AbstractMetrics instead of
>>>> > > >>>>>>>>>>>>>>>>>> static util methods.)
>>>> > > >>>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>>> I am not sure I fully understand the histogram
>>>> in the
>>>> > > >>>>>>>>>>>>>>>>> backend approach. Can
>>>> > > >>>>>>>>>>>>>>>>>> you explain a bit more? Do you mean emitting the
>>>> raw
>>>> > > data,
>>>> > > >>>>>>>>>>>>>>>>> e.g. fetchTime
>>>> > > >>>>>>>>>>>>>>>>>> and emitTime with each record and let the
>>>> histogram
>>>> > > >>>>>>>>>>>>>>>>> computation happen in
>>>> > > >>>>>>>>>>>>>>>>>> the background? Or let the processing thread
>>>> putting
>>>> > the
>>>> > > >>>>>>>>>>>>>>>>> values into a
>>>> > > >>>>>>>>>>>>>>>>>> queue and have a separate thread polling from the
>>>> > queue
>>>> > > >> and
>>>> > > >>>>>>>>>>>>>>>>> add them into
>>>> > > >>>>>>>>>>>>>>>>>> the histogram?
>>>> > > >>>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>>> Thanks,
>>>> > > >>>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>>> Jiangjie (Becket) Qin
>>>> > > >>>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>>> On Fri, Feb 22, 2019 at 4:34 PM Chesnay Schepler
>>>> > > >>>>>>>>>>>>>>>>> <chesnay@apache.org <mailto:chesnay@apache.org
>>>> >>
>>>> > > wrote:
>>>> > > >>>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>>>> Re: Flip
>>>> > > >>>>>>>>>>>>>>>>>>> The very first line under both the main header
>>>> and
>>>> > > >> Purpose
>>>> > > >>>>>>>>>>>>>>>>> section
>>>> > > >>>>>>>>>>>>>>>>>>> describe Flips as "major changes", which this
>>>> isn't.
>>>> > > >>>>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>>>> Re: complication
>>>> > > >>>>>>>>>>>>>>>>>>> I'm not arguing against standardization, but
>>>> again an
>>>> > > >>>>>>>>>>>>>>>>> over-complicated
>>>> > > >>>>>>>>>>>>>>>>>>> implementation when a static utility method
>>>> would be
>>>> > > >>>>>>>>>>>>>>>>> sufficient.
>>>> > > >>>>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>>>> public static void setupConnectorMetrics(
>>>> > > >>>>>>>>>>>>>>>>>>> MetricGroup operatorMetricGroup,
>>>> > > >>>>>>>>>>>>>>>>>>> String connectorName,
>>>> > > >>>>>>>>>>>>>>>>>>> Optional<Gauge<Long>> numRecordsIn,
>>>> > > >>>>>>>>>>>>>>>>>>> ...)
>>>> > > >>>>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>>>> This gives you all you need:
>>>> > > >>>>>>>>>>>>>>>>>>> * a well-defined set of metrics for a connector
>>>> to
>>>> > > opt-in
>>>> > > >>>>>>>>>>>>>>>>>>> * standardized naming schemes for scope and
>>>> > individual
>>>> > > >>>>>>>>>>>>>>> metrics
>>>> > > >>>>>>>>>>>>>>>>>>> * standardize metric types (although personally
>>>> I'm
>>>> > not
>>>> > > >>>>>>>>>>>>>>>>> interested in that
>>>> > > >>>>>>>>>>>>>>>>>>> since metric types should be considered
>>>> syntactic
>>>> > > sugar)
>>>> > > >>>>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>>>> Re: Configurable Histogram
>>>> > > >>>>>>>>>>>>>>>>>>> If anything they _must_ be turned off by
>>>> default, but
>>>> > > the
>>>> > > >>>>>>>>>>>>>>>>> metric system is
>>>> > > >>>>>>>>>>>>>>>>>>> already exposing so many options that I'm not
>>>> too
>>>> > keen
>>>> > > on
>>>> > > >>>>>>>>>>>>>>>>> adding even more.
>>>> > > >>>>>>>>>>>>>>>>>>> You have also only addressed my first argument
>>>> > against
>>>> > > >>>>>>>>>>>>>>>>> histograms
>>>> > > >>>>>>>>>>>>>>>>>>> (performance), the second one still stands
>>>> (calculate
>>>> > > >>>>>>>>>>>>>>>>> histogram in metric
>>>> > > >>>>>>>>>>>>>>>>>>> backends instead).
>>>> > > >>>>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>>>> On 21.02.2019 16:27, Becket Qin wrote:
>>>> > > >>>>>>>>>>>>>>>>>>>> Hi Chesnay,
>>>> > > >>>>>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>>>>> Thanks for the comments. I think this is
>>>> worthy of a
>>>> > > >> FLIP
>>>> > > >>>>>>>>>>>>>>>>> because it is
>>>> > > >>>>>>>>>>>>>>>>>>>> public API. According to the FLIP description
>>>> a FlIP
>>>> > > is
>>>> > > >>>>>>>>>>>>>>>>> required in case
>>>> > > >>>>>>>>>>>>>>>>>>> of:
>>>> > > >>>>>>>>>>>>>>>>>>>> - Any change that impacts the public
>>>> interfaces of
>>>> > > >>>>>>>>>>>>>>>>> the project
>>>> > > >>>>>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>>>>> and the following entry is found in the
>>>> definition
>>>> > of
>>>> > > >>>>>>>>>>>>>>>>> "public interface".
>>>> > > >>>>>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>>>>> - Exposed monitoring information
>>>> > > >>>>>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>>>>> Metrics are critical to any production system.
>>>> So a
>>>> > > >> clear
>>>> > > >>>>>>>>>>>>>>>>> metric
>>>> > > >>>>>>>>>>>>>>>>>>> definition
>>>> > > >>>>>>>>>>>>>>>>>>>> is important for any serious users. For an
>>>> > > organization
>>>> > > >>>>>>>>>>>>>>>>> with large Flink
>>>> > > >>>>>>>>>>>>>>>>>>>> installation, change in metrics means great
>>>> amount
>>>> > of
>>>> > > >>>>>>>>>>>>>>>>> work. So such
>>>> > > >>>>>>>>>>>>>>>>>>> changes
>>>> > > >>>>>>>>>>>>>>>>>>>> do need to be fully discussed and documented.
>>>> > > >>>>>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>>>>> ** Re: Histogram.
>>>> > > >>>>>>>>>>>>>>>>>>>> We can discuss whether there is a better way to
>>>> > expose
>>>> > > >>>>>>>>>>>>>>>>> metrics that are
>>>> > > >>>>>>>>>>>>>>>>>>>> suitable for histograms. My micro-benchmark on
>>>> > various
>>>> > > >>>>>>>>>>>>>>>>> histogram
>>>> > > >>>>>>>>>>>>>>>>>>>> implementations also indicates that they are
>>>> > > >>>>>>>>>>>>>> significantly
>>>> > > >>>>>>>>>>>>>>>>> slower than
>>>> > > >>>>>>>>>>>>>>>>>>>> other metric types. But I don't think that
>>>> means
>>>> > never
>>>> > > >>>>>>>>>>>>>> use
>>>> > > >>>>>>>>>>>>>>>>> histogram, but
>>>> > > >>>>>>>>>>>>>>>>>>>> means use it with caution. For example, we can
>>>> > suggest
>>>> > > >>>>>>>>>>>>>> the
>>>> > > >>>>>>>>>>>>>>>>>>> implementations
>>>> > > >>>>>>>>>>>>>>>>>>>> to turn them off by default and only turn it
>>>> on for
>>>> > a
>>>> > > >>>>>>>>>>>>>>>>> small amount of
>>>> > > >>>>>>>>>>>>>>>>>>> time
>>>> > > >>>>>>>>>>>>>>>>>>>> when performing some micro-debugging.
>>>> > > >>>>>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>>>>> ** Re: complication:
>>>> > > >>>>>>>>>>>>>>>>>>>> Connector conventions are essential for Flink
>>>> > > ecosystem.
>>>> > > >>>>>>>>>>>>>>>>> Flink connectors
>>>> > > >>>>>>>>>>>>>>>>>>>> pool is probably the most important part of
>>>> Flink,
>>>> > > just
>>>> > > >>>>>>>>>>>>>>>>> like any other
>>>> > > >>>>>>>>>>>>>>>>>>> data
>>>> > > >>>>>>>>>>>>>>>>>>>> system. Clear conventions of connectors will
>>>> help
>>>> > > build
>>>> > > >>>>>>>>>>>>>>>>> Flink ecosystem
>>>> > > >>>>>>>>>>>>>>>>>>> in
>>>> > > >>>>>>>>>>>>>>>>>>>> a more organic way.
>>>> > > >>>>>>>>>>>>>>>>>>>> Take the metrics convention as an example,
>>>> imagine
>>>> > > >>>>>>>>>>>>>> someone
>>>> > > >>>>>>>>>>>>>>>>> has developed
>>>> > > >>>>>>>>>>>>>>>>>>> a
>>>> > > >>>>>>>>>>>>>>>>>>>> Flink connector for System foo, and another
>>>> > developer
>>>> > > >> may
>>>> > > >>>>>>>>>>>>>>>>> have developed
>>>> > > >>>>>>>>>>>>>>>>>>> a
>>>> > > >>>>>>>>>>>>>>>>>>>> monitoring and diagnostic framework for Flink
>>>> which
>>>> > > >>>>>>>>>>>>>>>>> analyzes the Flink
>>>> > > >>>>>>>>>>>>>>>>>>> job
>>>> > > >>>>>>>>>>>>>>>>>>>> performance based on metrics. With a clear
>>>> metric
>>>> > > >>>>>>>>>>>>>>>>> convention, those two
>>>> > > >>>>>>>>>>>>>>>>>>>> projects could be developed independently. Once
>>>> > users
>>>> > > >> put
>>>> > > >>>>>>>>>>>>>>>>> them together,
>>>> > > >>>>>>>>>>>>>>>>>>>> it would work without additional
>>>> modifications. This
>>>> > > >>>>>>>>>>>>>>>>> cannot be easily
>>>> > > >>>>>>>>>>>>>>>>>>>> achieved by just defining a few constants.
>>>> > > >>>>>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>>>>> ** Re: selective metrics:
>>>> > > >>>>>>>>>>>>>>>>>>>> Sure, we can discuss that in a separate thread.
>>>> > > >>>>>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>>>>> @Dawid
>>>> > > >>>>>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>>>>> ** Re: latency / fetchedLatency
>>>> > > >>>>>>>>>>>>>>>>>>>> The primary purpose of establish such a
>>>> convention
>>>> > is
>>>> > > to
>>>> > > >>>>>>>>>>>>>>>>> help developers
>>>> > > >>>>>>>>>>>>>>>>>>>> write connectors in a more compatible way. The
>>>> > > >> convention
>>>> > > >>>>>>>>>>>>>>>>> is supposed to
>>>> > > >>>>>>>>>>>>>>>>>>> be
>>>> > > >>>>>>>>>>>>>>>>>>>> defined more proactively. So when look at the
>>>> > > >> convention,
>>>> > > >>>>>>>>>>>>>>>>> it seems more
>>>> > > >>>>>>>>>>>>>>>>>>>> important to see if the concept is applicable
>>>> to
>>>> > > >>>>>>>>>>>>>>>>> connectors in general.
>>>> > > >>>>>>>>>>>>>>>>>>> It
>>>> > > >>>>>>>>>>>>>>>>>>>> might be true so far only Kafka connector
>>>> reports
>>>> > > >>>>>>>>>>>>>> latency.
>>>> > > >>>>>>>>>>>>>>>>> But there
>>>> > > >>>>>>>>>>>>>>>>>>> might
>>>> > > >>>>>>>>>>>>>>>>>>>> be hundreds of other connector implementations
>>>> in
>>>> > the
>>>> > > >>>>>>>>>>>>>>>>> Flink ecosystem,
>>>> > > >>>>>>>>>>>>>>>>>>>> though not in the Flink repo, and some of them
>>>> also
>>>> > > >> emits
>>>> > > >>>>>>>>>>>>>>>>> latency. I
>>>> > > >>>>>>>>>>>>>>>>>>> think
>>>> > > >>>>>>>>>>>>>>>>>>>> a lot of other sources actually also has an
>>>> append
>>>> > > >>>>>>>>>>>>>>>>> timestamp. e.g.
>>>> > > >>>>>>>>>>>>>>>>>>> database
>>>> > > >>>>>>>>>>>>>>>>>>>> bin logs and some K-V stores. So I wouldn't be
>>>> > > surprised
>>>> > > >>>>>>>>>>>>>>>>> if some database
>>>> > > >>>>>>>>>>>>>>>>>>>> connector can also emit latency metrics.
>>>> > > >>>>>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>>>>> Thanks,
>>>> > > >>>>>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>>>>> Jiangjie (Becket) Qin
>>>> > > >>>>>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>>>>> On Thu, Feb 21, 2019 at 10:14 PM Chesnay
>>>> Schepler
>>>> > > >>>>>>>>>>>>>>>>> <chesnay@apache.org <mailto:chesnay@apache.org
>>>> >>
>>>> > > >>>>>>>>>>>>>>>>>>>> wrote:
>>>> > > >>>>>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>>>>>> Regarding 2) It doesn't make sense to
>>>> investigate
>>>> > > this
>>>> > > >>>>>>>>>>>>>> as
>>>> > > >>>>>>>>>>>>>>>>> part of this
>>>> > > >>>>>>>>>>>>>>>>>>>>> FLIP. This is something that could be of
>>>> interest
>>>> > for
>>>> > > >>>>>>>>>>>>>> the
>>>> > > >>>>>>>>>>>>>>>>> entire metric
>>>> > > >>>>>>>>>>>>>>>>>>>>> system, and should be designed for as such.
>>>> > > >>>>>>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>>>>>> Regarding the proposal as a whole:
>>>> > > >>>>>>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>>>>>> Histogram metrics shall not be added to the
>>>> core of
>>>> > > >>>>>>>>>>>>>>>>> Flink. They are
>>>> > > >>>>>>>>>>>>>>>>>>>>> significantly more expensive than other
>>>> metrics,
>>>> > and
>>>> > > >>>>>>>>>>>>>>>>> calculating
>>>> > > >>>>>>>>>>>>>>>>>>>>> histograms in the application is regarded as
>>>> an
>>>> > > >>>>>>>>>>>>>>>>> anti-pattern by several
>>>> > > >>>>>>>>>>>>>>>>>>>>> metric backends, who instead recommend to
>>>> expose
>>>> > the
>>>> > > >> raw
>>>> > > >>>>>>>>>>>>>>>>> data and
>>>> > > >>>>>>>>>>>>>>>>>>>>> calculate the histogram in the backend.
>>>> > > >>>>>>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>>>>>> Second, this seems overly complicated. Given
>>>> that
>>>> > we
>>>> > > >>>>>>>>>>>>>>>>> already established
>>>> > > >>>>>>>>>>>>>>>>>>>>> that not all connectors will export all
>>>> metrics we
>>>> > > are
>>>> > > >>>>>>>>>>>>>>>>> effectively
>>>> > > >>>>>>>>>>>>>>>>>>>>> reducing this down to a consistent naming
>>>> scheme.
>>>> > We
>>>> > > >>>>>>>>>>>>>>>>> don't need anything
>>>> > > >>>>>>>>>>>>>>>>>>>>> sophisticated for that; basically just a few
>>>> > > constants
>>>> > > >>>>>>>>>>>>>>>>> that all
>>>> > > >>>>>>>>>>>>>>>>>>>>> connectors use.
>>>> > > >>>>>>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>>>>>> I'm not convinced that this is worthy of a
>>>> FLIP.
>>>> > > >>>>>>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>>>>>> On 21.02.2019 14:26, Dawid Wysakowicz wrote:
>>>> > > >>>>>>>>>>>>>>>>>>>>>> Hi,
>>>> > > >>>>>>>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>>>>>>> Ad 1. In general I undestand and I agree. But
>>>> > those
>>>> > > >>>>>>>>>>>>>>>>> particular metrics
>>>> > > >>>>>>>>>>>>>>>>>>>>>> (latency, fetchLatency), right now would
>>>> only be
>>>> > > >>>>>>>>>>>>>>>>> reported if user uses
>>>> > > >>>>>>>>>>>>>>>>>>>>>> KafkaConsumer with internal
>>>> timestampAssigner with
>>>> > > >>>>>>>>>>>>>>>>> StreamCharacteristic
>>>> > > >>>>>>>>>>>>>>>>>>>>>> set to EventTime, right? That sounds like a
>>>> very
>>>> > > >>>>>>>>>>>>>>>>> specific case. I am
>>>> > > >>>>>>>>>>>>>>>>>>> not
>>>> > > >>>>>>>>>>>>>>>>>>>>>> sure if we should introduce a generic metric
>>>> that
>>>> > > will
>>>> > > >>>>>>>>>>>>>> be
>>>> > > >>>>>>>>>>>>>>>>>>>>>> disabled/absent for most of implementations.
>>>> > > >>>>>>>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>>>>>>> Ad.2 That sounds like an orthogonal issue,
>>>> that
>>>> > > might
>>>> > > >>>>>>>>>>>>>>>>> make sense to
>>>> > > >>>>>>>>>>>>>>>>>>>>>> investigate in the future.
>>>> > > >>>>>>>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>>>>>>> Best,
>>>> > > >>>>>>>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>>>>>>> Dawid
>>>> > > >>>>>>>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>>>>>>> On 21/02/2019 13:20, Becket Qin wrote:
>>>> > > >>>>>>>>>>>>>>>>>>>>>>> Hi Dawid,
>>>> > > >>>>>>>>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>>>>>>>> Thanks for the feedback. That makes sense
>>>> to me.
>>>> > > >> There
>>>> > > >>>>>>>>>>>>>>>>> are two cases
>>>> > > >>>>>>>>>>>>>>>>>>> to
>>>> > > >>>>>>>>>>>>>>>>>>>>> be
>>>> > > >>>>>>>>>>>>>>>>>>>>>>> addressed.
>>>> > > >>>>>>>>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>>>>>>>> 1. The metrics are supposed to be a
>>>> guidance. It
>>>> > is
>>>> > > >>>>>>>>>>>>>>>>> likely that a
>>>> > > >>>>>>>>>>>>>>>>>>>>> connector
>>>> > > >>>>>>>>>>>>>>>>>>>>>>> only supports some but not all of the
>>>> metrics. In
>>>> > > >> that
>>>> > > >>>>>>>>>>>>>>>>> case, each
>>>> > > >>>>>>>>>>>>>>>>>>>>> connector
>>>> > > >>>>>>>>>>>>>>>>>>>>>>> implementation should have the freedom to
>>>> decide
>>>> > > >> which
>>>> > > >>>>>>>>>>>>>>>>> metrics are
>>>> > > >>>>>>>>>>>>>>>>>>>>>>> reported. For the metrics that are
>>>> supported, the
>>>> > > >>>>>>>>>>>>>>>>> guidance should be
>>>> > > >>>>>>>>>>>>>>>>>>>>>>> followed.
>>>> > > >>>>>>>>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>>>>>>>> 2. Sometimes users may want to disable
>>>> certain
>>>> > > >> metrics
>>>> > > >>>>>>>>>>>>>>>>> for some reason
>>>> > > >>>>>>>>>>>>>>>>>>>>>>> (e.g. performance / reprocessing of data). A
>>>> > > generic
>>>> > > >>>>>>>>>>>>>>>>> mechanism should
>>>> > > >>>>>>>>>>>>>>>>>>> be
>>>> > > >>>>>>>>>>>>>>>>>>>>>>> provided to allow user choose which metrics
>>>> are
>>>> > > >>>>>>>>>>>>>>>>> reported. This
>>>> > > >>>>>>>>>>>>>>>>>>> mechanism
>>>> > > >>>>>>>>>>>>>>>>>>>>>>> should also be honored by the connector
>>>> > > >>>>>>>>>>>>>> implementations.
>>>> > > >>>>>>>>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>>>>>>>> Does this sound reasonable to you?
>>>> > > >>>>>>>>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>>>>>>>> Thanks,
>>>> > > >>>>>>>>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>>>>>>>> Jiangjie (Becket) Qin
>>>> > > >>>>>>>>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>>>>>>>> On Thu, Feb 21, 2019 at 4:22 PM Dawid
>>>> Wysakowicz
>>>> > <
>>>> > > >>>>>>>>>>>>>>>>>>>>> dwysakowicz@apache.org <mailto:
>>>> > > dwysakowicz@apache.org
>>>> > > >>>>
>>>> > > >>>>>>>>>>>>>>>>>>>>>>> wrote:
>>>> > > >>>>>>>>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> Hi,
>>>> > > >>>>>>>>>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> Generally I like the idea of having a
>>>> unified,
>>>> > > >>>>>>>>>>>>>>>>> standard set of
>>>> > > >>>>>>>>>>>>>>>>>>> metrics
>>>> > > >>>>>>>>>>>>>>>>>>>>> for
>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> all connectors. I have some slight concerns
>>>> > about
>>>> > > >>>>>>>>>>>>>>>>> fetchLatency and
>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> latency though. They are computed based on
>>>> > > EventTime
>>>> > > >>>>>>>>>>>>>>>>> which is not a
>>>> > > >>>>>>>>>>>>>>>>>>>>> purely
>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> technical feature. It depends often on some
>>>> > > business
>>>> > > >>>>>>>>>>>>>>>>> logic, might be
>>>> > > >>>>>>>>>>>>>>>>>>>>> absent
>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> or defined after source. Those metrics
>>>> could
>>>> > also
>>>> > > >>>>>>>>>>>>>>>>> behave in a weird
>>>> > > >>>>>>>>>>>>>>>>>>>>> way in
>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> case of replaying backlog. Therefore I am
>>>> not
>>>> > sure
>>>> > > >> if
>>>> > > >>>>>>>>>>>>>>>>> we should
>>>> > > >>>>>>>>>>>>>>>>>>> include
>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> those metrics by default. Maybe we could at
>>>> > least
>>>> > > >>>>>>>>>>>>>>>>> introduce a feature
>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> switch for them? What do you think?
>>>> > > >>>>>>>>>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> Best,
>>>> > > >>>>>>>>>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> Dawid
>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> On 21/02/2019 03:13, Becket Qin wrote:
>>>> > > >>>>>>>>>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> Bump. If there is no objections to the
>>>> proposed
>>>> > > >>>>>>>>>>>>>>>>> metrics. I'll start a
>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> voting thread later toady.
>>>> > > >>>>>>>>>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> Thanks,
>>>> > > >>>>>>>>>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> Jiangjie (Becket) Qin
>>>> > > >>>>>>>>>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> On Mon, Feb 11, 2019 at 8:17 PM Becket Qin
>>>> > > >>>>>>>>>>>>>>>>> <becket.qin@gmail.com <mailto:
>>>> becket.qin@gmail.com>>
>>>> > <
>>>> > > >>>>>>>>>>>>>>>>>>>>> becket.qin@gmail.com <mailto:
>>>> becket.qin@gmail.com
>>>> > >>
>>>> > > >>>>>>>>>>>>>>> wrote:
>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> Hi folks,
>>>> > > >>>>>>>>>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> I would like to start the FLIP discussion
>>>> thread
>>>> > > >>>>>>>>>>>>>> about
>>>> > > >>>>>>>>>>>>>>>>> standardize
>>>> > > >>>>>>>>>>>>>>>>>>> the
>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> connector metrics.
>>>> > > >>>>>>>>>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> In short, we would like to provide a
>>>> convention
>>>> > of
>>>> > > >>>>>>>>>>>>>>>>> Flink connector
>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> metrics. It will help simplify the
>>>> monitoring
>>>> > and
>>>> > > >>>>>>>>>>>>>>>>> alerting on Flink
>>>> > > >>>>>>>>>>>>>>>>>>>>> jobs.
>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> The FLIP link is following:
>>>> > > >>>>>>>>>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>
>>>> > > >>>>>>>>>
>>>> > > >>>>>>>
>>>> > > >>>>>
>>>> > > >>
>>>> > >
>>>> >
>>>> https://cwiki.apache.org/confluence/display/FLINK/FLIP-33%3A+Standardize+Connector+Metrics
>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> Thanks,
>>>> > > >>>>>>>>>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>>>>>>>>> Jiangjie (Becket) Qin
>>>> > > >>>>>>>>>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>
>>>> > > >>>>>>>>>>>>
>>>> > > >>>>>>>>>
>>>> > > >>>>>>>>>
>>>> > > >>>>>>>>>
>>>> > > >>>>>>>
>>>> > > >>>>>>>
>>>> > > >>>>>>>
>>>> > > >>>>>
>>>> > > >>>>>
>>>> > > >>
>>>> > > >>
>>>> > >
>>>> > >
>>>> >
>>>>
>>>>
>>>> --
>>>>
>>>> Konstantin Knauf
>>>>
>>>> https://twitter.com/snntrable
>>>>
>>>> https://github.com/knaufk
>>>>
>>>
Re: [DISCUSS] FLIP-33: Standardize connector metrics
Posted by Becket Qin <be...@gmail.com>.
Hey Konstantin,
Thanks for the feedback and suggestions. Please see the reply below.
* idleTime: In the meantime, a similar metric "idleTimeMsPerSecond" has
> been introduced in https://issues.apache.org/jira/browse/FLINK-16864. They
> have a similar name, but different definitions of idleness,
> e.g. "idleTimeMsPerSecond" considers the SourceTask idle, when it is
> backpressured. Can we make it clearer that these two metrics mean different
> things?
That is a good point. I did not notice this metric earlier. It seems that
both metrics are useful to the users. One tells them how busy the source is
and how much more throughput the source can handle. The other tells the
users how long since the source has seen the last record, which is useful
for debugging. I'll update the FLIP to make it clear.
* "current(Fetch)Latency" I am wondering if "eventTimeLag(Before|After)"
> is more descriptive/clear. What do others think?
I am quite open to the ideas on these names. In fact I also feel
"current(Fetch)Latency" are not super intuitive. So it would be great if we
can have better names.
* Current(Fetch)Latency implies that the timestamps are directly
> extracted in the source connector, right? Will this be the default for
> FLIP-27 sources anyway?
The "currentFetchLatency" will probably be reported by each source
implementation, because the data fetching is done by SplitReaders and there
is no base implementation. The "currentLatency", on the other hand, can be
reported by the SourceReader base implementation. However, since developers
can actually implement their own source connector without using our base
implementation, these metric guidance are still useful for the connector
developers in that case.
* Does FLIP-33 also include the implementation of these metrics (to the
> extent possible) for all connectors currently available in Apache Flink or
> is the "per-connector implementation" out-of-scope?
FLIP-33 itself does not specify any implementation of those metrics. But
the connectors we provide in Apache Flink will follow the guidance of
FLIP-33 to emit those metrics when applicable. Maybe We can have some
public static Strings defined for the metric names to help other connector
developers follow the same guidance. I can also add that to the public
interface section of the FLIP if we decide to do that.
Thanks,
Jiangjie (Becket) Qin
On Tue, Sep 8, 2020 at 9:02 PM Becket Qin <be...@gmail.com> wrote:
>
>
> On Tue, Sep 8, 2020 at 6:55 PM Konstantin Knauf <kn...@apache.org> wrote:
>
>> Hi Becket,
>>
>> Thank you for picking up this FLIP. I have a few questions:
>>
>> * two thoughts on naming:
>> * idleTime: In the meantime, a similar metric "idleTimeMsPerSecond" has
>> been introduced in https://issues.apache.org/jira/browse/FLINK-16864.
>> They
>> have a similar name, but different definitions of idleness,
>> e.g. "idleTimeMsPerSecond" considers the SourceTask idle, when it is
>> backpressured. Can we make it clearer that these two metrics mean
>> different
>> things?
>>
>> * "current(Fetch)Latency" I am wondering if "eventTimeLag(Before|After)"
>> is more descriptive/clear. What do others think?
>>
>> * Current(Fetch)Latency implies that the timestamps are directly
>> extracted in the source connector, right? Will this be the default for
>> FLIP-27 sources anyway?
>>
>> * Does FLIP-33 also include the implementation of these metrics (to the
>> extent possible) for all connectors currently available in Apache Flink or
>> is the "per-connector implementation" out-of-scope?
>>
>> Thanks,
>>
>> Konstantin
>>
>>
>>
>>
>>
>> On Fri, Sep 4, 2020 at 4:56 PM Becket Qin <be...@gmail.com> wrote:
>>
>> > Hi all,
>> >
>> > To complete the Source refactoring work, I'd like to revive this
>> > discussion. Since the mail thread has been dormant for more than a year,
>> > just to recap the motivation of the FLIP:
>> >
>> > 1. The FLIP proposes to standardize the connector metrics by giving
>> > guidance on the metric specifications, including the name, type and
>> meaning
>> > of the metrics.
>> > 2. It is OK for a connector to not emit some of the metrics in the
>> metric
>> > guidance, but if a metric of the same semantic is emitted, the
>> > implementation should follow the guidance.
>> > 3. It is OK for a connector to emit more metrics than what are listed in
>> > the FLIP. This includes having an alias for a metric specified in the
>> FLIP.
>> > 4. We will implement some of the metrics out of the box in the default
>> > implementation of FLIP-27, as long as it is applicable.
>> >
>> > The FLIP wiki is following:
>> > https://cwiki.apache.org/confluence/display/FLINK/FLIP-33
>> > %3A+Standardize+Connector+Metrics
>> >
>> > Any thoughts?
>> >
>> > Thanks,
>> >
>> > Jiangjie (Becket) Qin
>> >
>> >
>> > On Fri, Jun 14, 2019 at 2:29 PM Piotr Nowojski <pi...@ververica.com>
>> > wrote:
>> >
>> > > > we will need to revisit the convention list and adjust them
>> accordingly
>> > > when FLIP-27 is ready
>> > >
>> > >
>> > > Yes, this sounds good :)
>> > >
>> > > Piotrek
>> > >
>> > > > On 13 Jun 2019, at 13:35, Becket Qin <be...@gmail.com> wrote:
>> > > >
>> > > > Hi Piotr,
>> > > >
>> > > > That's great to know. Chances are that we will need to revisit the
>> > > > convention list and adjust them accordingly when FLIP-27 is ready,
>> At
>> > > that
>> > > > point we can mark some of the metrics as available by default for
>> > > > connectors implementing the new interface.
>> > > >
>> > > > Thanks,
>> > > >
>> > > > Jiangjie (Becket) Qin
>> > > >
>> > > > On Thu, Jun 13, 2019 at 3:51 PM Piotr Nowojski <piotr@ververica.com
>> >
>> > > wrote:
>> > > >
>> > > >> Thanks for driving this. I’ve just noticed one small thing. With
>> new
>> > > >> SourceReader interface Flink will be able to provide `idleTime`
>> metric
>> > > >> automatically.
>> > > >>
>> > > >> Piotrek
>> > > >>
>> > > >>> On 13 Jun 2019, at 03:30, Becket Qin <be...@gmail.com>
>> wrote:
>> > > >>>
>> > > >>> Thanks all for the feedback and discussion.
>> > > >>>
>> > > >>> Since there wasn't any concern raised, I've started the voting
>> thread
>> > > for
>> > > >>> this FLIP, but please feel free to continue the discussion here if
>> > you
>> > > >>> think something still needs to be addressed.
>> > > >>>
>> > > >>> Thanks,
>> > > >>>
>> > > >>> Jiangjie (Becket) Qin
>> > > >>>
>> > > >>>
>> > > >>>
>> > > >>> On Mon, Jun 10, 2019 at 9:10 AM Becket Qin <be...@gmail.com>
>> > > wrote:
>> > > >>>
>> > > >>>> Hi Piotr,
>> > > >>>>
>> > > >>>> Thanks for the comments. Yes, you are right. Users will have to
>> look
>> > > at
>> > > >>>> other metrics to decide whether the pipeline is healthy or not in
>> > the
>> > > >> first
>> > > >>>> place before they can use the time-based metric to fix the
>> > bottleneck.
>> > > >>>>
>> > > >>>> I agree that once we have FLIP-27 ready, some of the metrics can
>> > just
>> > > be
>> > > >>>> reported by the abstract implementation.
>> > > >>>>
>> > > >>>> I've updated FLIP-33 wiki page to add the pendingBytes and
>> > > >> pendingRecords
>> > > >>>> metric. Please let me know if you have any concern over the
>> updated
>> > > >> metric
>> > > >>>> convention proposal.
>> > > >>>>
>> > > >>>> @Chesnay Schepler <ch...@apache.org> @Stephan Ewen
>> > > >>>> <st...@ververica.com> will you also have time to take a look
>> at
>> > the
>> > > >>>> proposed metric convention? If there is no further concern I'll
>> > start
>> > > a
>> > > >>>> voting thread for this FLIP in two days.
>> > > >>>>
>> > > >>>> Thanks,
>> > > >>>>
>> > > >>>> Jiangjie (Becket) Qin
>> > > >>>>
>> > > >>>>
>> > > >>>>
>> > > >>>> On Wed, Jun 5, 2019 at 6:54 PM Piotr Nowojski <
>> piotr@ververica.com>
>> > > >> wrote:
>> > > >>>>
>> > > >>>>> Hi Becket,
>> > > >>>>>
>> > > >>>>> Thanks for the answer :)
>> > > >>>>>
>> > > >>>>>> By time-based metric, I meant the portion of time spent on
>> > producing
>> > > >> the
>> > > >>>>>> record to downstream. For example, a source connector can
>> report
>> > > that
>> > > >>>>> it's
>> > > >>>>>> spending 80% of time to emit record to downstream processing
>> > > pipeline.
>> > > >>>>> In
>> > > >>>>>> another case, a sink connector may report that its spending
>> 30% of
>> > > >> time
>> > > >>>>>> producing the records to the external system.
>> > > >>>>>>
>> > > >>>>>> This is in some sense equivalent to the buffer usage metric:
>> > > >>>>>
>> > > >>>>>> - 80% of time spent on emitting records to downstream --->
>> > > downstream
>> > > >>>>>> node is bottleneck ---> output buffer is probably full.
>> > > >>>>>> - 30% of time spent on emitting records to downstream --->
>> > > downstream
>> > > >>>>>> node is not bottleneck ---> output buffer is probably not full.
>> > > >>>>>
>> > > >>>>> If by “time spent on emitting records to downstream” you
>> understand
>> > > >>>>> “waiting on back pressure”, then I see your point. And I agree
>> that
>> > > >> some
>> > > >>>>> kind of ratio/time based metric gives you more information.
>> However
>> > > >> under
>> > > >>>>> “time spent on emitting records to downstream” might be hidden
>> the
>> > > >>>>> following (extreme) situation:
>> > > >>>>>
>> > > >>>>> 1. Job is barely able to handle influx of records, there is 99%
>> > > >>>>> CPU/resource usage in the cluster, but nobody is
>> > > >>>>> bottlenecked/backpressured, all output buffers are empty,
>> everybody
>> > > is
>> > > >>>>> waiting in 1% of it’s time for more records to process.
>> > > >>>>> 2. 80% time can still be spent on "down stream operators”,
>> because
>> > > they
>> > > >>>>> are the CPU intensive operations, but this doesn’t mean that
>> > > >> increasing the
>> > > >>>>> parallelism down the stream will help with anything there. To
>> the
>> > > >> contrary,
>> > > >>>>> increasing parallelism of the source operator might help to
>> > increase
>> > > >>>>> resource utilisation up to 100%.
>> > > >>>>>
>> > > >>>>> However, this “time based/ratio” approach can be extended to
>> > > in/output
>> > > >>>>> buffer usage. Besides collecting an information that
>> input/output
>> > > >> buffer is
>> > > >>>>> full/empty, we can probe profile how often are buffer
>> empty/full.
>> > If
>> > > >> output
>> > > >>>>> buffer is full 1% of times, there is almost no back pressure. If
>> > it’s
>> > > >> full
>> > > >>>>> 80% of times, there is some back pressure, if it’s full 99.9% of
>> > > times,
>> > > >>>>> there is huge back pressure.
>> > > >>>>>
>> > > >>>>> Now for autoscaling you could compare the input & output buffers
>> > fill
>> > > >>>>> ratio:
>> > > >>>>>
>> > > >>>>> 1. Both are high, the source of bottleneck is down the stream
>> > > >>>>> 2. Output is low, input is high, this is the bottleneck and the
>> > > higher
>> > > >>>>> the difference, the bigger source of bottleneck is this is
>> > > >> operator/task
>> > > >>>>> 3. Output is high, input is low - there was some load spike
>> that we
>> > > are
>> > > >>>>> currently finishing to process
>> > > >>>>>
>> > > >>>>>
>> > > >>>>>
>> > > >>>>> But long story short, we are probably diverging from the topic
>> of
>> > > this
>> > > >>>>> discussion, and we can discuss this at some later point.
>> > > >>>>>
>> > > >>>>> For now, for sources:
>> > > >>>>>
>> > > >>>>> as I wrote before, +1 for:
>> > > >>>>> - pending.bytes, Gauge
>> > > >>>>> - pending.messages, Gauge
>> > > >>>>>
>> > > >>>>> When we will be developing/discussing SourceReader from FLIP-27
>> we
>> > > >> might
>> > > >>>>> then add:
>> > > >>>>>
>> > > >>>>> - in-memory.buffer.usage (0 - 100%)
>> > > >>>>>
>> > > >>>>> Which will be estimated automatically by Flink while user will
>> be
>> > > able
>> > > >> to
>> > > >>>>> override/provide better estimation.
>> > > >>>>>
>> > > >>>>> Piotrek
>> > > >>>>>
>> > > >>>>>> On 5 Jun 2019, at 05:42, Becket Qin <be...@gmail.com>
>> wrote:
>> > > >>>>>>
>> > > >>>>>> Hi Piotr,
>> > > >>>>>>
>> > > >>>>>> Thanks for the explanation. Please see some clarifications
>> below.
>> > > >>>>>>
>> > > >>>>>> By time-based metric, I meant the portion of time spent on
>> > producing
>> > > >> the
>> > > >>>>>> record to downstream. For example, a source connector can
>> report
>> > > that
>> > > >>>>> it's
>> > > >>>>>> spending 80% of time to emit record to downstream processing
>> > > pipeline.
>> > > >>>>> In
>> > > >>>>>> another case, a sink connector may report that its spending
>> 30% of
>> > > >> time
>> > > >>>>>> producing the records to the external system.
>> > > >>>>>>
>> > > >>>>>> This is in some sense equivalent to the buffer usage metric:
>> > > >>>>>> - 80% of time spent on emitting records to downstream --->
>> > > downstream
>> > > >>>>>> node is bottleneck ---> output buffer is probably full.
>> > > >>>>>> - 30% of time spent on emitting records to downstream --->
>> > > downstream
>> > > >>>>>> node is not bottleneck ---> output buffer is probably not full.
>> > > >>>>>>
>> > > >>>>>> However, the time-based metric has a few advantages that the
>> > buffer
>> > > >>>>> usage
>> > > >>>>>> metric may not have.
>> > > >>>>>>
>> > > >>>>>> 1. Buffer usage metric may not be applicable to all the
>> connector
>> > > >>>>>> implementations, while reporting time-based metric are always
>> > > doable.
>> > > >>>>>> Some source connectors may not have any input buffer, or they
>> may
>> > > use
>> > > >>>>> some
>> > > >>>>>> third party library that does not expose the input buffer at
>> all.
>> > > >>>>>> Similarly, for sink connectors, the implementation may not have
>> > any
>> > > >>>>> output
>> > > >>>>>> buffer, or the third party library does not expose such buffer.
>> > > >>>>>>
>> > > >>>>>> 2. Although both type of metrics can detect bottleneck,
>> time-based
>> > > >>>>> metrics
>> > > >>>>>> can be used to generate a more informed action to remove the
>> > > >> bottleneck.
>> > > >>>>>> For example, when the downstream is bottleneck, the output
>> buffer
>> > > >> usage
>> > > >>>>>> metric is likely to be 100%, and the input buffer usage might
>> be
>> > 0%.
>> > > >>>>> That
>> > > >>>>>> means we don't know what is the suitable parallelism to lift
>> the
>> > > >>>>>> bottleneck. The time-based metric, on the other hand, would
>> give
>> > > >> useful
>> > > >>>>>> information, e.g. if 80% of time was spent on emitting
>> records, we
>> > > can
>> > > >>>>>> roughly increase the downstream node parallelism by 4 times.
>> > > >>>>>>
>> > > >>>>>> Admittedly, the time-based metrics are more expensive than
>> buffer
>> > > >>>>> usage. So
>> > > >>>>>> we may have to do some sampling to reduce the cost. But in
>> > general,
>> > > >>>>> using
>> > > >>>>>> time-based metrics seems worth adding.
>> > > >>>>>>
>> > > >>>>>> That being said, I don't think buffer usage metric and
>> time-based
>> > > >>>>> metrics
>> > > >>>>>> are mutually exclusive. We can probably have both. It is just
>> that
>> > > in
>> > > >>>>>> practice, features like auto-scaling might prefer time-based
>> > metrics
>> > > >> for
>> > > >>>>>> the reason stated above.
>> > > >>>>>>
>> > > >>>>>>> 1. Define the metrics that would allow us to manually detect
>> > > >>>>> bottlenecks.
>> > > >>>>>> As I wrote, we already have them in most of the places, except
>> of
>> > > >>>>>> sources/sinks.
>> > > >>>>>>> 2. Use those metrics, to automatically detect bottlenecks.
>> > > Currently
>> > > >> we
>> > > >>>>>> are only automatically detecting back pressure and reporting
>> it to
>> > > the
>> > > >>>>> user
>> > > >>>>>> in web UI (is it exposed as a metric at all?). Detecting the
>> root
>> > > >> cause
>> > > >>>>> of
>> > > >>>>>> the back pressure (bottleneck) is one step further.
>> > > >>>>>>> 3. Use the knowledge about where exactly the bottleneck is
>> > located,
>> > > >> to
>> > > >>>>>> try to do something with it.
>> > > >>>>>>
>> > > >>>>>> As explained above, I think time-based metric also addresses
>> item
>> > 1
>> > > >> and
>> > > >>>>>> item 2.
>> > > >>>>>>
>> > > >>>>>> Any thoughts？
>> > > >>>>>>
>> > > >>>>>> Thanks,
>> > > >>>>>>
>> > > >>>>>> Jiangjie (Becket) Qin
>> > > >>>>>>
>> > > >>>>>>
>> > > >>>>>>
>> > > >>>>>> On Mon, Jun 3, 2019 at 4:14 PM Piotr Nowojski <
>> > piotr@ververica.com>
>> > > >>>>> wrote:
>> > > >>>>>>
>> > > >>>>>>> Hi again :)
>> > > >>>>>>>
>> > > >>>>>>>> - pending.bytes, Gauge
>> > > >>>>>>>> - pending.messages, Gauge
>> > > >>>>>>>
>> > > >>>>>>>
>> > > >>>>>>> +1
>> > > >>>>>>>
>> > > >>>>>>> And true, instead of overloading one of the metric it is
>> better
>> > > when
>> > > >>>>> user
>> > > >>>>>>> can choose to provide only one of them.
>> > > >>>>>>>
>> > > >>>>>>> Re 2:
>> > > >>>>>>>
>> > > >>>>>>>> If I understand correctly, this metric along with the pending
>> > > >> mesages
>> > > >>>>> /
>> > > >>>>>>>> bytes would answer the questions of:
>> > > >>>>>>>
>> > > >>>>>>>> - Does the connector consume fast enough? Lagging behind +
>> empty
>> > > >>>>> buffer
>> > > >>>>>>> =
>> > > >>>>>>>> cannot consume fast enough.
>> > > >>>>>>>> - Does the connector emit fast enough? Lagging behind + full
>> > > buffer
>> > > >> =
>> > > >>>>>>>> cannot emit fast enough, i.e. the Flink pipeline is slow.
>> > > >>>>>>>
>> > > >>>>>>> Yes, exactly. This can also be used to support decisions like
>> > > >> changing
>> > > >>>>> the
>> > > >>>>>>> parallelism of the sources and/or down stream operators.
>> > > >>>>>>>
>> > > >>>>>>> I’m not sure if I understand your proposal with time based
>> > > >>>>> measurements.
>> > > >>>>>>> Maybe I’m missing something, but I do not see how measuring
>> time
>> > > >> alone
>> > > >>>>>>> could answer the problem: where is the bottleneck. Time spent
>> on
>> > > the
>> > > >>>>>>> next/emit might be short or long (depending on how heavy to
>> > process
>> > > >> the
>> > > >>>>>>> record is) and the source can still be bottlenecked/back
>> > pressured
>> > > or
>> > > >>>>> not.
>> > > >>>>>>> Usually the easiest and the most reliable way how to detect
>> > > >>>>> bottlenecks is
>> > > >>>>>>> by checking usage of input & output buffers, since when input
>> > > buffer
>> > > >> is
>> > > >>>>>>> full while output buffer is empty, that’s the definition of a
>> > > >>>>> bottleneck.
>> > > >>>>>>> Also this is usually very easy and cheap to measure (it works
>> > > >>>>> effectively
>> > > >>>>>>> the same way as current’s Flink back pressure monitoring, but
>> > more
>> > > >>>>> cleanly,
>> > > >>>>>>> without probing thread’s stack traces).
>> > > >>>>>>>
>> > > >>>>>>> Also keep in mind that we are already using the buffer usage
>> > > metrics
>> > > >>>>> for
>> > > >>>>>>> detecting the bottlenecks in Flink’s internal network
>> exchanges
>> > > >> (manual
>> > > >>>>>>> work). That’s the reason why I wanted to extend this to
>> > > >> sources/sinks,
>> > > >>>>>>> since they are currently our blind spot.
>> > > >>>>>>>
>> > > >>>>>>>> One feature we are currently working on to scale Flink
>> > > automatically
>> > > >>>>>>> relies
>> > > >>>>>>>> on some metrics answering the same question
>> > > >>>>>>>
>> > > >>>>>>> That would be very helpful feature. I think in order to
>> achieve
>> > > that
>> > > >> we
>> > > >>>>>>> would need to:
>> > > >>>>>>> 1. Define the metrics that would allow us to manually detect
>> > > >>>>> bottlenecks.
>> > > >>>>>>> As I wrote, we already have them in most of the places,
>> except of
>> > > >>>>>>> sources/sinks.
>> > > >>>>>>> 2. Use those metrics, to automatically detect bottlenecks.
>> > > Currently
>> > > >> we
>> > > >>>>>>> are only automatically detecting back pressure and reporting
>> it
>> > to
>> > > >> the
>> > > >>>>> user
>> > > >>>>>>> in web UI (is it exposed as a metric at all?). Detecting the
>> root
>> > > >>>>> cause of
>> > > >>>>>>> the back pressure (bottleneck) is one step further.
>> > > >>>>>>> 3. Use the knowledge about where exactly the bottleneck is
>> > located,
>> > > >> to
>> > > >>>>> try
>> > > >>>>>>> to do something with it.
>> > > >>>>>>>
>> > > >>>>>>> I think you are aiming for point 3., but before we reach it,
>> we
>> > are
>> > > >>>>> still
>> > > >>>>>>> missing 1. & 2. Also even if we have 3., there is a value in
>> 1 &
>> > 2
>> > > >> for
>> > > >>>>>>> manual analysis/dashboards.
>> > > >>>>>>>
>> > > >>>>>>> However, having the knowledge of where the bottleneck is,
>> doesn’t
>> > > >>>>>>> necessarily mean that we know what we can do about it. For
>> > example
>> > > >>>>>>> increasing parallelism might or might not help with anything
>> > (data
>> > > >>>>> skew,
>> > > >>>>>>> bottleneck on some resource that does not scale), but this
>> remark
>> > > >>>>> applies
>> > > >>>>>>> always, regardless of the way how did we detect the
>> bottleneck.
>> > > >>>>>>>
>> > > >>>>>>> Piotrek
>> > > >>>>>>>
>> > > >>>>>>>> On 3 Jun 2019, at 06:16, Becket Qin <be...@gmail.com>
>> > wrote:
>> > > >>>>>>>>
>> > > >>>>>>>> Hi Piotr,
>> > > >>>>>>>>
>> > > >>>>>>>> Thanks for the suggestion. Some thoughts below:
>> > > >>>>>>>>
>> > > >>>>>>>> Re 1: The pending messages / bytes.
>> > > >>>>>>>> I completely agree these are very useful metrics and we
>> should
>> > > >> expect
>> > > >>>>> the
>> > > >>>>>>>> connector to report. WRT the way to expose them, it seems
>> more
>> > > >>>>> consistent
>> > > >>>>>>>> to add two metrics instead of adding a method (unless there
>> are
>> > > >> other
>> > > >>>>> use
>> > > >>>>>>>> cases other than metric reporting). So we can add the
>> following
>> > > two
>> > > >>>>>>> metrics.
>> > > >>>>>>>> - pending.bytes, Gauge
>> > > >>>>>>>> - pending.messages, Gauge
>> > > >>>>>>>> Applicable connectors can choose to report them. These two
>> > metrics
>> > > >>>>> along
>> > > >>>>>>>> with latency should be sufficient for users to understand the
>> > > >> progress
>> > > >>>>>>> of a
>> > > >>>>>>>> connector.
>> > > >>>>>>>>
>> > > >>>>>>>>
>> > > >>>>>>>> Re 2: Number of buffered data in-memory of the connector
>> > > >>>>>>>> If I understand correctly, this metric along with the pending
>> > > >> mesages
>> > > >>>>> /
>> > > >>>>>>>> bytes would answer the questions of:
>> > > >>>>>>>> - Does the connector consume fast enough? Lagging behind +
>> empty
>> > > >>>>> buffer
>> > > >>>>>>> =
>> > > >>>>>>>> cannot consume fast enough.
>> > > >>>>>>>> - Does the connector emit fast enough? Lagging behind + full
>> > > buffer
>> > > >> =
>> > > >>>>>>>> cannot emit fast enough, i.e. the Flink pipeline is slow.
>> > > >>>>>>>>
>> > > >>>>>>>> One feature we are currently working on to scale Flink
>> > > automatically
>> > > >>>>>>> relies
>> > > >>>>>>>> on some metrics answering the same question, more
>> specifically,
>> > we
>> > > >> are
>> > > >>>>>>>> profiling the time spent on .next() method (time to consume)
>> and
>> > > the
>> > > >>>>> time
>> > > >>>>>>>> spent on .collect() method (time to emit / process). One
>> > advantage
>> > > >> of
>> > > >>>>>>> such
>> > > >>>>>>>> method level time cost allows us to calculate the parallelism
>> > > >>>>> required to
>> > > >>>>>>>> keep up in case their is a lag.
>> > > >>>>>>>>
>> > > >>>>>>>> However, one concern I have regarding such metric is that
>> they
>> > are
>> > > >>>>>>>> implementation specific. Either profiling on the method
>> time, or
>> > > >>>>>>> reporting
>> > > >>>>>>>> buffer usage assumes the connector are implemented in such a
>> > way.
>> > > A
>> > > >>>>>>>> slightly better solution might be have the following metric:
>> > > >>>>>>>>
>> > > >>>>>>>> - EmitTimeRatio (or FetchTimeRatio): The time spent on
>> emitting
>> > > >>>>>>>> records / Total time elapsed.
>> > > >>>>>>>>
>> > > >>>>>>>> This assumes that the source connectors have to emit the
>> records
>> > > to
>> > > >>>>> the
>> > > >>>>>>>> downstream at some point. The emission may take some time (
>> e.g.
>> > > go
>> > > >>>>>>> through
>> > > >>>>>>>> chained operators). And the rest of the time are spent to
>> > prepare
>> > > >> the
>> > > >>>>>>>> record to emit, including time for consuming and format
>> > > conversion,
>> > > >>>>> etc.
>> > > >>>>>>>> Ideally, we'd like to see the time spent on record fetch and
>> > emit
>> > > to
>> > > >>>>> be
>> > > >>>>>>>> about the same, so no one is bottleneck for the other.
>> > > >>>>>>>>
>> > > >>>>>>>> The downside of these time based metrics is additional
>> overhead
>> > to
>> > > >> get
>> > > >>>>>>> the
>> > > >>>>>>>> time, therefore sampling might be needed. But in practice I
>> feel
>> > > >> such
>> > > >>>>>>> time
>> > > >>>>>>>> based metric might be more useful if we want to take action.
>> > > >>>>>>>>
>> > > >>>>>>>>
>> > > >>>>>>>> I think we should absolutely add metrics in (1) to the metric
>> > > >>>>> convention.
>> > > >>>>>>>> We could also add the metrics mentioned in (2) if we reach
>> > > consensus
>> > > >>>>> on
>> > > >>>>>>>> that. What do you think?
>> > > >>>>>>>>
>> > > >>>>>>>> Thanks,
>> > > >>>>>>>>
>> > > >>>>>>>> Jiangjie (Becket) Qin
>> > > >>>>>>>>
>> > > >>>>>>>>
>> > > >>>>>>>> On Fri, May 31, 2019 at 4:26 PM Piotr Nowojski <
>> > > piotr@ververica.com
>> > > >>>
>> > > >>>>>>> wrote:
>> > > >>>>>>>>
>> > > >>>>>>>>> Hey Becket,
>> > > >>>>>>>>>
>> > > >>>>>>>>> Re 1a) and 1b) +1 from my side.
>> > > >>>>>>>>>
>> > > >>>>>>>>> I’ve discussed this issue:
>> > > >>>>>>>>>
>> > > >>>>>>>>>>>>
>> > > >>>>>>>>>>>> 2. It would be nice to have metrics, that allow us to
>> check
>> > > the
>> > > >>>>> cause
>> > > >>>>>>>>> of
>> > > >>>>>>>>>>>> back pressure:
>> > > >>>>>>>>>>>> a) for sources, length of input queue (in bytes? Or
>> boolean
>> > > >>>>>>>>>>>> hasSomethingl/isEmpty)
>> > > >>>>>>>>>>>> b) for sinks, length of output queue (in bytes? Or
>> boolean
>> > > >>>>>>>>>>>> hasSomething/isEmpty)
>> > > >>>>>>>>>
>> > > >>>>>>>>> With Nico at some lengths and he also saw the benefits of
>> them.
>> > > We
>> > > >>>>> also
>> > > >>>>>>>>> have more concrete proposal for that.
>> > > >>>>>>>>>
>> > > >>>>>>>>> Actually there are two really useful metrics, that we are
>> > missing
>> > > >>>>>>>>> currently:
>> > > >>>>>>>>>
>> > > >>>>>>>>> 1. Number of data/records/bytes in the backlog to process.
>> For
>> > > >>>>> example
>> > > >>>>>>>>> remaining number of bytes in unread files. Or pending data
>> in
>> > > Kafka
>> > > >>>>>>> topics.
>> > > >>>>>>>>> 2. Number of buffered data in-memory of the connector, that
>> are
>> > > >>>>> waiting
>> > > >>>>>>> to
>> > > >>>>>>>>> be processed pushed to Flink pipeline.
>> > > >>>>>>>>>
>> > > >>>>>>>>> Re 1:
>> > > >>>>>>>>> This would have to be a metric provided directly by a
>> > connector.
>> > > It
>> > > >>>>>>> could
>> > > >>>>>>>>> be an undefined `int`:
>> > > >>>>>>>>>
>> > > >>>>>>>>> `int backlog` - estimate of pending work.
>> > > >>>>>>>>>
>> > > >>>>>>>>> “Undefined” meaning that it would be up to a connector to
>> > decided
>> > > >>>>>>> whether
>> > > >>>>>>>>> it’s measured in bytes, records, pending files or whatever
>> it
>> > is
>> > > >>>>>>> possible
>> > > >>>>>>>>> to provide by the connector. This is because I assume not
>> every
>> > > >>>>>>> connector
>> > > >>>>>>>>> can provide exact number and for some of them it might be
>> > > >> impossible
>> > > >>>>> to
>> > > >>>>>>>>> provide records number of bytes count.
>> > > >>>>>>>>>
>> > > >>>>>>>>> Re 2:
>> > > >>>>>>>>> This metric could be either provided by a connector, or
>> > > calculated
>> > > >>>>>>> crudely
>> > > >>>>>>>>> by Flink:
>> > > >>>>>>>>>
>> > > >>>>>>>>> `float bufferUsage` - value from [0.0, 1.0] range
>> > > >>>>>>>>>
>> > > >>>>>>>>> Percentage of used in memory buffers, like in Kafka’s
>> handover.
>> > > >>>>>>>>>
>> > > >>>>>>>>> It could be crudely implemented by Flink with FLIP-27
>> > > >>>>>>>>> SourceReader#isAvailable. If SourceReader is not available
>> > > reported
>> > > >>>>>>>>> `bufferUsage` could be 0.0. If it is available, it could be
>> > 1.0.
>> > > I
>> > > >>>>> think
>> > > >>>>>>>>> this would be a good enough estimation for most of the use
>> > cases
>> > > >>>>> (that
>> > > >>>>>>>>> could be overloaded and implemented better if desired).
>> > > Especially
>> > > >>>>>>> since we
>> > > >>>>>>>>> are reporting only probed values: if probed values are
>> almost
>> > > >> always
>> > > >>>>>>> “1.0”,
>> > > >>>>>>>>> it would mean that we have a back pressure. If they are
>> almost
>> > > >> always
>> > > >>>>>>>>> “0.0”, there is probably no back pressure at the sources.
>> > > >>>>>>>>>
>> > > >>>>>>>>> What do you think about this?
>> > > >>>>>>>>>
>> > > >>>>>>>>> Piotrek
>> > > >>>>>>>>>
>> > > >>>>>>>>>> On 30 May 2019, at 11:41, Becket Qin <becket.qin@gmail.com
>> >
>> > > >> wrote:
>> > > >>>>>>>>>>
>> > > >>>>>>>>>> Hi all,
>> > > >>>>>>>>>>
>> > > >>>>>>>>>> Thanks a lot for all the feedback and comments. I'd like to
>> > > >> continue
>> > > >>>>>>> the
>> > > >>>>>>>>>> discussion on this FLIP.
>> > > >>>>>>>>>>
>> > > >>>>>>>>>> I updated the FLIP-33 wiki to remove all the histogram
>> metrics
>> > > >> from
>> > > >>>>> the
>> > > >>>>>>>>>> first version of metric convention due to the performance
>> > > concern.
>> > > >>>>> The
>> > > >>>>>>>>> plan
>> > > >>>>>>>>>> is to introduce them later when we have a mechanism to opt
>> > > in/out
>> > > >>>>>>>>> metrics.
>> > > >>>>>>>>>> At that point, users can decide whether they want to pay
>> the
>> > > cost
>> > > >> to
>> > > >>>>>>> get
>> > > >>>>>>>>>> the metric or not.
>> > > >>>>>>>>>>
>> > > >>>>>>>>>> As Stephan suggested, for this FLIP, let's first try to
>> agree
>> > on
>> > > >> the
>> > > >>>>>>>>> small
>> > > >>>>>>>>>> list of conventional metrics that connectors should follow.
>> > > >>>>>>>>>> Just to be clear, the purpose of the convention is not to
>> > > enforce
>> > > >>>>> every
>> > > >>>>>>>>>> connector to report all these metrics, but to provide a
>> > guidance
>> > > >> in
>> > > >>>>>>> case
>> > > >>>>>>>>>> these metrics are reported by some connectors.
>> > > >>>>>>>>>>
>> > > >>>>>>>>>>
>> > > >>>>>>>>>> @ Stephan & Chesnay,
>> > > >>>>>>>>>>
>> > > >>>>>>>>>> Regarding the duplication of `RecordsIn` metric in
>> operator /
>> > > task
>> > > >>>>>>>>>> IOMetricGroups, from what I understand, for source
>> operator,
>> > it
>> > > is
>> > > >>>>>>>>> actually
>> > > >>>>>>>>>> the SourceFunction that reports the operator level
>> > > >>>>>>>>>> RecordsIn/RecordsInPerSecond metric. So they are
>> essentially
>> > the
>> > > >>>>> same
>> > > >>>>>>>>>> metric in the operator level IOMetricGroup. Similarly for
>> the
>> > > Sink
>> > > >>>>>>>>>> operator, the operator level RecordsOut/RecordsOutPerSecond
>> > > >> metrics
>> > > >>>>> are
>> > > >>>>>>>>>> also reported by the Sink function. I marked them as
>> existing
>> > in
>> > > >> the
>> > > >>>>>>>>>> FLIP-33 wiki page. Please let me know if I misunderstood.
>> > > >>>>>>>>>>
>> > > >>>>>>>>>> Thanks,
>> > > >>>>>>>>>>
>> > > >>>>>>>>>> Jiangjie (Becket) Qin
>> > > >>>>>>>>>>
>> > > >>>>>>>>>>
>> > > >>>>>>>>>> On Thu, May 30, 2019 at 5:16 PM Becket Qin <
>> > > becket.qin@gmail.com>
>> > > >>>>>>> wrote:
>> > > >>>>>>>>>>
>> > > >>>>>>>>>>> Hi Piotr,
>> > > >>>>>>>>>>>
>> > > >>>>>>>>>>> Thanks a lot for the feedback.
>> > > >>>>>>>>>>>
>> > > >>>>>>>>>>> 1a) I guess you are referring to the part that "original
>> > system
>> > > >>>>>>> specific
>> > > >>>>>>>>>>> metrics should also be reported". The performance impact
>> > > depends
>> > > >> on
>> > > >>>>>>> the
>> > > >>>>>>>>>>> implementation. An efficient implementation would only
>> record
>> > > the
>> > > >>>>>>> metric
>> > > >>>>>>>>>>> once, but report them with two different metric names.
>> This
>> > is
>> > > >>>>>>> unlikely
>> > > >>>>>>>>> to
>> > > >>>>>>>>>>> hurt performance.
>> > > >>>>>>>>>>>
>> > > >>>>>>>>>>> 1b) Yes, I agree that we should avoid adding overhead to
>> the
>> > > >>>>> critical
>> > > >>>>>>>>> path
>> > > >>>>>>>>>>> by all means. This is sometimes a tradeoff, running
>> blindly
>> > > >> without
>> > > >>>>>>> any
>> > > >>>>>>>>>>> metric gives best performance, but sometimes might be
>> > > frustrating
>> > > >>>>> when
>> > > >>>>>>>>> we
>> > > >>>>>>>>>>> debug some issues.
>> > > >>>>>>>>>>>
>> > > >>>>>>>>>>> 2. The metrics are indeed very useful. Are they supposed
>> to
>> > be
>> > > >>>>>>> reported
>> > > >>>>>>>>> by
>> > > >>>>>>>>>>> the connectors or Flink itself? At this point FLIP-33 is
>> more
>> > > >>>>> focused
>> > > >>>>>>> on
>> > > >>>>>>>>>>> provide a guidance to the connector authors on the metrics
>> > > >>>>> reporting.
>> > > >>>>>>>>> That
>> > > >>>>>>>>>>> said, after FLIP-27, I think we should absolutely report
>> > these
>> > > >>>>> metrics
>> > > >>>>>>>>> in
>> > > >>>>>>>>>>> the abstract implementation. In any case, the metric
>> > convention
>> > > >> in
>> > > >>>>>>> this
>> > > >>>>>>>>>>> list are expected to evolve over time.
>> > > >>>>>>>>>>>
>> > > >>>>>>>>>>> Thanks,
>> > > >>>>>>>>>>>
>> > > >>>>>>>>>>> Jiangjie (Becket) Qin
>> > > >>>>>>>>>>>
>> > > >>>>>>>>>>> On Tue, May 28, 2019 at 6:24 PM Piotr Nowojski <
>> > > >>>>> piotr@ververica.com>
>> > > >>>>>>>>>>> wrote:
>> > > >>>>>>>>>>>
>> > > >>>>>>>>>>>> Hi,
>> > > >>>>>>>>>>>>
>> > > >>>>>>>>>>>> Thanks for the proposal and driving the effort here
>> Becket
>> > :)
>> > > >> I’ve
>> > > >>>>>>> read
>> > > >>>>>>>>>>>> through the FLIP-33 [1], and here are couple of my
>> thoughts.
>> > > >>>>>>>>>>>>
>> > > >>>>>>>>>>>> Big +1 for standardising the metric names between
>> > connectors,
>> > > it
>> > > >>>>> will
>> > > >>>>>>>>>>>> definitely help us and users a lot.
>> > > >>>>>>>>>>>>
>> > > >>>>>>>>>>>> Issues/questions/things to discuss that I’ve thought of:
>> > > >>>>>>>>>>>>
>> > > >>>>>>>>>>>> 1a. If we are about to duplicate some metrics, can this
>> > > become a
>> > > >>>>>>>>>>>> performance issue?
>> > > >>>>>>>>>>>> 1b. Generally speaking, we should make sure that
>> collecting
>> > > >> those
>> > > >>>>>>>>> metrics
>> > > >>>>>>>>>>>> is as non intrusive as possible, especially that they
>> will
>> > > need
>> > > >>>>> to be
>> > > >>>>>>>>>>>> updated once per record. (They might be collected more
>> > rarely
>> > > >> with
>> > > >>>>>>> some
>> > > >>>>>>>>>>>> overhead, but the hot path of updating it per record will
>> > need
>> > > >> to
>> > > >>>>> be
>> > > >>>>>>> as
>> > > >>>>>>>>>>>> quick as possible). That includes both avoiding heavy
>> > > >> computation
>> > > >>>>> on
>> > > >>>>>>>>> per
>> > > >>>>>>>>>>>> record path: histograms?, measuring time for time based
>> > > metrics
>> > > >>>>> (per
>> > > >>>>>>>>>>>> second) (System.currentTimeMillis() depending on the
>> > > >>>>> implementation
>> > > >>>>>>> can
>> > > >>>>>>>>>>>> invoke a system call)
>> > > >>>>>>>>>>>>
>> > > >>>>>>>>>>>> 2. It would be nice to have metrics, that allow us to
>> check
>> > > the
>> > > >>>>> cause
>> > > >>>>>>>>> of
>> > > >>>>>>>>>>>> back pressure:
>> > > >>>>>>>>>>>> a) for sources, length of input queue (in bytes? Or
>> boolean
>> > > >>>>>>>>>>>> hasSomethingl/isEmpty)
>> > > >>>>>>>>>>>> b) for sinks, length of output queue (in bytes? Or
>> boolean
>> > > >>>>>>>>>>>> hasSomething/isEmpty)
>> > > >>>>>>>>>>>>
>> > > >>>>>>>>>>>> a) is useful in a scenario when we are processing
>> backlog of
>> > > >>>>> records,
>> > > >>>>>>>>> all
>> > > >>>>>>>>>>>> of the internal Flink’s input/output network buffers are
>> > > empty,
>> > > >>>>> and
>> > > >>>>>>> we
>> > > >>>>>>>>> want
>> > > >>>>>>>>>>>> to check whether the external source system is the
>> > bottleneck
>> > > >>>>>>> (source’s
>> > > >>>>>>>>>>>> input queue will be empty), or if the Flink’s connector
>> is
>> > the
>> > > >>>>>>>>> bottleneck
>> > > >>>>>>>>>>>> (source’s input queues will be full).
>> > > >>>>>>>>>>>> b) similar story. Backlog of records, but this time all
>> of
>> > the
>> > > >>>>>>> internal
>> > > >>>>>>>>>>>> Flink’s input/ouput network buffers are full, and we
>> want o
>> > > >> check
>> > > >>>>>>>>> whether
>> > > >>>>>>>>>>>> the external sink system is the bottleneck (sink output
>> > queues
>> > > >> are
>> > > >>>>>>>>> full),
>> > > >>>>>>>>>>>> or if the Flink’s connector is the bottleneck (sink’s
>> output
>> > > >>>>> queues
>> > > >>>>>>>>> will be
>> > > >>>>>>>>>>>> empty)
>> > > >>>>>>>>>>>>
>> > > >>>>>>>>>>>> It might be sometimes difficult to provide those
>> metrics, so
>> > > >> they
>> > > >>>>>>> could
>> > > >>>>>>>>>>>> be optional, but if we could provide them, it would be
>> > really
>> > > >>>>>>> helpful.
>> > > >>>>>>>>>>>>
>> > > >>>>>>>>>>>> Piotrek
>> > > >>>>>>>>>>>>
>> > > >>>>>>>>>>>> [1]
>> > > >>>>>>>>>>>>
>> > > >>>>>>>>>
>> > > >>>>>>>
>> > > >>>>>
>> > > >>
>> > >
>> >
>> https://cwiki.apache.org/confluence/display/FLINK/FLIP-33:+Standardize+Connector+Metrics
>> > > >>>>>>>>>>>> <
>> > > >>>>>>>>>>>>
>> > > >>>>>>>>>
>> > > >>>>>>>
>> > > >>>>>
>> > > >>
>> > >
>> >
>> https://cwiki.apache.org/confluence/display/FLINK/FLIP-33:+Standardize+Connector+Metrics
>> > > >>>>>>>>>>>>>
>> > > >>>>>>>>>>>>
>> > > >>>>>>>>>>>>> On 24 Apr 2019, at 13:28, Stephan Ewen <
>> sewen@apache.org>
>> > > >> wrote:
>> > > >>>>>>>>>>>>>
>> > > >>>>>>>>>>>>> I think this sounds reasonable.
>> > > >>>>>>>>>>>>>
>> > > >>>>>>>>>>>>> Let's keep the "reconfiguration without stopping the
>> job"
>> > out
>> > > >> of
>> > > >>>>>>> this,
>> > > >>>>>>>>>>>>> because that would be a super big effort and if we
>> approach
>> > > >> that,
>> > > >>>>>>> then
>> > > >>>>>>>>>>>> in
>> > > >>>>>>>>>>>>> more generic way rather than specific to connector
>> metrics.
>> > > >>>>>>>>>>>>>
>> > > >>>>>>>>>>>>> I would suggest to look at the following things before
>> > > starting
>> > > >>>>> with
>> > > >>>>>>>>> any
>> > > >>>>>>>>>>>>> implementation work:
>> > > >>>>>>>>>>>>>
>> > > >>>>>>>>>>>>> - Try and find a committer to support this, otherwise it
>> > will
>> > > >> be
>> > > >>>>>>> hard
>> > > >>>>>>>>>>>> to
>> > > >>>>>>>>>>>>> make progress
>> > > >>>>>>>>>>>>> - Start with defining a smaller set of "core metrics"
>> and
>> > > >> extend
>> > > >>>>> the
>> > > >>>>>>>>>>>> set
>> > > >>>>>>>>>>>>> later. I think that is easier than now blocking on
>> reaching
>> > > >>>>>>> consensus
>> > > >>>>>>>>>>>> on a
>> > > >>>>>>>>>>>>> large group of metrics.
>> > > >>>>>>>>>>>>> - Find a solution to the problem Chesnay mentioned, that
>> > the
>> > > >>>>>>> "records
>> > > >>>>>>>>>>>> in"
>> > > >>>>>>>>>>>>> metric is somehow overloaded and exists already in the
>> IO
>> > > >> Metric
>> > > >>>>>>>>> group.
>> > > >>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>
>> > > >>>>>>>>>>>>> On Mon, Mar 25, 2019 at 7:16 AM Becket Qin <
>> > > >> becket.qin@gmail.com
>> > > >>>>>>
>> > > >>>>>>>>>>>> wrote:
>> > > >>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>> Hi Stephan,
>> > > >>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>> Thanks a lot for the feedback. All makes sense.
>> > > >>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>> It is a good suggestion to simply have an
>> > onRecord(numBytes,
>> > > >>>>>>>>> eventTime)
>> > > >>>>>>>>>>>>>> method for connector writers. It should meet most of
>> the
>> > > >>>>>>>>> requirements,
>> > > >>>>>>>>>>>>>> individual
>> > > >>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>> The configurable metrics feature is something really
>> > useful,
>> > > >>>>>>>>>>>> especially if
>> > > >>>>>>>>>>>>>> we can somehow make it dynamically configurable without
>> > > >> stopping
>> > > >>>>>>> the
>> > > >>>>>>>>>>>> jobs.
>> > > >>>>>>>>>>>>>> It might be better to make it a separate discussion
>> > because
>> > > it
>> > > >>>>> is a
>> > > >>>>>>>>>>>> more
>> > > >>>>>>>>>>>>>> generic feature instead of only for connectors.
>> > > >>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>> So in order to make some progress, in this FLIP we can
>> > limit
>> > > >> the
>> > > >>>>>>>>>>>> discussion
>> > > >>>>>>>>>>>>>> scope to the connector related items:
>> > > >>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>> - the standard connector metric names and types.
>> > > >>>>>>>>>>>>>> - the abstract ConnectorMetricHandler interface
>> > > >>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>> I'll start a separate thread to discuss other general
>> > metric
>> > > >>>>>>> related
>> > > >>>>>>>>>>>>>> enhancement items including:
>> > > >>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>> - optional metrics
>> > > >>>>>>>>>>>>>> - dynamic metric configuration
>> > > >>>>>>>>>>>>>> - potential combination with rate limiter
>> > > >>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>> Does this plan sound reasonable?
>> > > >>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>> Thanks,
>> > > >>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>> Jiangjie (Becket) Qin
>> > > >>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>> On Sat, Mar 23, 2019 at 5:53 AM Stephan Ewen <
>> > > >> sewen@apache.org>
>> > > >>>>>>>>> wrote:
>> > > >>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>> Ignoring for a moment implementation details, this
>> > > connector
>> > > >>>>>>> metrics
>> > > >>>>>>>>>>>> work
>> > > >>>>>>>>>>>>>>> is a really good thing to do, in my opinion
>> > > >>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>> The questions "oh, my job seems to be doing nothing,
>> I am
>> > > >>>>> looking
>> > > >>>>>>> at
>> > > >>>>>>>>>>>> the
>> > > >>>>>>>>>>>>>> UI
>> > > >>>>>>>>>>>>>>> and the 'records in' value is still zero" is in the
>> top
>> > > three
>> > > >>>>>>>>> support
>> > > >>>>>>>>>>>>>>> questions I have been asked personally.
>> > > >>>>>>>>>>>>>>> Introspection into "how far is the consumer lagging
>> > behind"
>> > > >>>>> (event
>> > > >>>>>>>>>>>> time
>> > > >>>>>>>>>>>>>>> fetch latency) came up many times as well.
>> > > >>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>> So big +1 to solving this problem.
>> > > >>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>> About the exact design - I would try to go for the
>> > > following
>> > > >>>>>>>>>>>> properties:
>> > > >>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>> - keep complexity of of connectors. Ideally the
>> metrics
>> > > >> handler
>> > > >>>>>>> has
>> > > >>>>>>>>> a
>> > > >>>>>>>>>>>>>>> single onRecord(numBytes, eventTime) method or so, and
>> > > >>>>> everything
>> > > >>>>>>>>>>>> else is
>> > > >>>>>>>>>>>>>>> internal to the handler. That makes it dead simple for
>> > the
>> > > >>>>>>>>> connector.
>> > > >>>>>>>>>>>> We
>> > > >>>>>>>>>>>>>>> can also think of an extensive scheme for connector
>> > > specific
>> > > >>>>>>>>> metrics.
>> > > >>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>> - make it configurable on the job it cluster level
>> which
>> > > >>>>> metrics
>> > > >>>>>>> the
>> > > >>>>>>>>>>>>>>> handler internally creates when that method is
>> invoked.
>> > > >>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>> What do you think?
>> > > >>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>> Best,
>> > > >>>>>>>>>>>>>>> Stephan
>> > > >>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>> On Thu, Mar 21, 2019 at 10:42 AM Chesnay Schepler <
>> > > >>>>>>>>> chesnay@apache.org
>> > > >>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>> wrote:
>> > > >>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>> As I said before, I believe this to be
>> over-engineered
>> > and
>> > > >>>>> have
>> > > >>>>>>> no
>> > > >>>>>>>>>>>>>>>> interest in this implementation.
>> > > >>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>> There are conceptual issues like defining a duplicate
>> > > >>>>>>>>>>>>>> numBytesIn(PerSec)
>> > > >>>>>>>>>>>>>>>> metric that already exists for each operator.
>> > > >>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>> On 21.03.2019 06:13, Becket Qin wrote:
>> > > >>>>>>>>>>>>>>>>> A few updates to the thread. I uploaded a patch[1]
>> as a
>> > > >>>>> complete
>> > > >>>>>>>>>>>>>>>>> example of how users can use the metrics in the
>> future.
>> > > >>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>> Some thoughts below after taking a look at the
>> > > >>>>>>> AbstractMetricGroup
>> > > >>>>>>>>>>>>>> and
>> > > >>>>>>>>>>>>>>>>> its subclasses.
>> > > >>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>> This patch intends to provide convenience for Flink
>> > > >> connector
>> > > >>>>>>>>>>>>>>>>> implementations to follow metrics standards
>> proposed in
>> > > >>>>> FLIP-33.
>> > > >>>>>>>>> It
>> > > >>>>>>>>>>>>>>>>> also try to enhance the metric management in general
>> > way
>> > > to
>> > > >>>>> help
>> > > >>>>>>>>>>>>>> users
>> > > >>>>>>>>>>>>>>>>> with:
>> > > >>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>> 1. metric definition
>> > > >>>>>>>>>>>>>>>>> 2. metric dependencies check
>> > > >>>>>>>>>>>>>>>>> 3. metric validation
>> > > >>>>>>>>>>>>>>>>> 4. metric control (turn on / off particular metrics)
>> > > >>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>> This patch wraps |MetricGroup| to extend the
>> > > functionality
>> > > >> of
>> > > >>>>>>>>>>>>>>>>> |AbstractMetricGroup| and its subclasses. The
>> > > >>>>>>>>>>>>>>>>> |AbstractMetricGroup| mainly focus on the metric
>> group
>> > > >>>>>>> hierarchy,
>> > > >>>>>>>>>>>> but
>> > > >>>>>>>>>>>>>>>>> does not really manage the metrics other than
>> keeping
>> > > them
>> > > >>>>> in a
>> > > >>>>>>>>> Map.
>> > > >>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>> Ideally we should only have one entry point for the
>> > > >> metrics.
>> > > >>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>> Right now the entry point is |AbstractMetricGroup|.
>> > > >> However,
>> > > >>>>>>>>> besides
>> > > >>>>>>>>>>>>>>>>> the missing functionality mentioned above,
>> > > >>>>> |AbstractMetricGroup|
>> > > >>>>>>>>>>>>>> seems
>> > > >>>>>>>>>>>>>>>>> deeply rooted in Flink runtime. We could extract it
>> out
>> > > to
>> > > >>>>>>>>>>>>>>>>> flink-metrics in order to use it for generic
>> purpose.
>> > > There
>> > > >>>>> will
>> > > >>>>>>>>> be
>> > > >>>>>>>>>>>>>>>>> some work, though.
>> > > >>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>> Another approach is to make |AbstractMetrics| in
>> this
>> > > patch
>> > > >>>>> as
>> > > >>>>>>> the
>> > > >>>>>>>>>>>>>>>>> metric entry point. It wraps metric group and
>> provides
>> > > the
>> > > >>>>>>> missing
>> > > >>>>>>>>>>>>>>>>> functionalities. Then we can roll out this pattern
>> to
>> > > >> runtime
>> > > >>>>>>>>>>>>>>>>> components gradually as well.
>> > > >>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>> My first thought is that the latter approach gives a
>> > more
>> > > >>>>> smooth
>> > > >>>>>>>>>>>>>>>>> migration. But I am also OK with doing a
>> refactoring on
>> > > the
>> > > >>>>>>>>>>>>>>>>> |AbstractMetricGroup| family.
>> > > >>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>> Thanks,
>> > > >>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>> Jiangjie (Becket) Qin
>> > > >>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>> [1] https://github.com/becketqin/flink/pull/1
>> > > >>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>> On Mon, Feb 25, 2019 at 2:32 PM Becket Qin <
>> > > >>>>>>> becket.qin@gmail.com
>> > > >>>>>>>>>>>>>>>>> <ma...@gmail.com>> wrote:
>> > > >>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>> Hi Chesnay,
>> > > >>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>> It might be easier to discuss some implementation
>> > details
>> > > >> in
>> > > >>>>>>> the
>> > > >>>>>>>>>>>>>>>>> PR review instead of in the FLIP discussion thread.
>> I
>> > > have
>> > > >> a
>> > > >>>>>>>>>>>>>> patch
>> > > >>>>>>>>>>>>>>>>> for Kafka connectors ready but haven't submitted
>> the PR
>> > > >> yet.
>> > > >>>>>>>>>>>>>>>>> Hopefully that will help explain a bit more.
>> > > >>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>> ** Re: metric type binding
>> > > >>>>>>>>>>>>>>>>> This is a valid point that worths discussing. If I
>> > > >> understand
>> > > >>>>>>>>>>>>>>>>> correctly, there are two points:
>> > > >>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>> 1. Metric type / interface does not matter as long
>> as
>> > the
>> > > >>>>>>> metric
>> > > >>>>>>>>>>>>>>>>> semantic is clearly defined.
>> > > >>>>>>>>>>>>>>>>> Conceptually speaking, I agree that as long as the
>> > metric
>> > > >>>>>>>>>>>>>> semantic
>> > > >>>>>>>>>>>>>>>>> is defined, metric type does not matter. To some
>> > extent,
>> > > >>>>> Gauge
>> > > >>>>>>> /
>> > > >>>>>>>>>>>>>>>>> Counter / Meter / Histogram themselves can be think
>> of
>> > as
>> > > >>>>> some
>> > > >>>>>>>>>>>>>>>>> well-recognized semantics, if you wish. In Flink,
>> these
>> > > >>>>> metric
>> > > >>>>>>>>>>>>>>>>> semantics have their associated interface classes.
>> In
>> > > >>>>> practice,
>> > > >>>>>>>>>>>>>>>>> such semantic to interface binding seems necessary
>> for
>> > > >>>>>>> different
>> > > >>>>>>>>>>>>>>>>> components to communicate. Simply standardize the
>> > > semantic
>> > > >>>>> of
>> > > >>>>>>>>>>>>>> the
>> > > >>>>>>>>>>>>>>>>> connector metrics seems not sufficient for people to
>> > > build
>> > > >>>>>>>>>>>>>>>>> ecosystem on top of. At the end of the day, we still
>> > need
>> > > >> to
>> > > >>>>>>>>> have
>> > > >>>>>>>>>>>>>>>>> some embodiment of the metric semantics that people
>> can
>> > > >>>>> program
>> > > >>>>>>>>>>>>>>>>> against.
>> > > >>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>> 2. Sometimes the same metric semantic can be exposed
>> > > using
>> > > >>>>>>>>>>>>>>>>> different metric types / interfaces.
>> > > >>>>>>>>>>>>>>>>> This is a good point. Counter and Gauge-as-a-Counter
>> > are
>> > > >>>>> pretty
>> > > >>>>>>>>>>>>>>>>> much interchangeable. This is more of a trade-off
>> > between
>> > > >> the
>> > > >>>>>>>>>>>>>> user
>> > > >>>>>>>>>>>>>>>>> experience of metric producers and consumers. The
>> > metric
>> > > >>>>>>>>>>>>>> producers
>> > > >>>>>>>>>>>>>>>>> want to use Counter or Gauge depending on whether
>> the
>> > > >> counter
>> > > >>>>>>> is
>> > > >>>>>>>>>>>>>>>>> already tracked in code, while ideally the metric
>> > > consumers
>> > > >>>>>>> only
>> > > >>>>>>>>>>>>>>>>> want to see a single metric type for each metric. I
>> am
>> > > >>>>> leaning
>> > > >>>>>>>>>>>>>>>>> towards to make the metric producers happy, i.e.
>> allow
>> > > >> Gauge
>> > > >>>>> /
>> > > >>>>>>>>>>>>>>>>> Counter metric type, and the the metric consumers
>> > handle
>> > > >> the
>> > > >>>>>>>>> type
>> > > >>>>>>>>>>>>>>>>> variation. The reason is that in practice, there
>> might
>> > be
>> > > >>>>> more
>> > > >>>>>>>>>>>>>>>>> connector implementations than metric reporter
>> > > >>>>> implementations.
>> > > >>>>>>>>>>>>>> We
>> > > >>>>>>>>>>>>>>>>> could also provide some helper method to facilitate
>> > > reading
>> > > >>>>>>> from
>> > > >>>>>>>>>>>>>>>>> such variable metric type.
>> > > >>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>> Just some quick replies to the comments around
>> > > >> implementation
>> > > >>>>>>>>>>>>>>>> details.
>> > > >>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>> 4) single place where metrics are registered
>> except
>> > > >>>>>>>>>>>>>>>>> connector-specific
>> > > >>>>>>>>>>>>>>>>> ones (which we can't really avoid).
>> > > >>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>> Register connector specific ones in a single place
>> is
>> > > >>>>> actually
>> > > >>>>>>>>>>>>>>>>> something that I want to achieve.
>> > > >>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>> 2) I'm talking about time-series databases like
>> > > >>>>> Prometheus.
>> > > >>>>>>>>>>>>>> We
>> > > >>>>>>>>>>>>>>>>> would
>> > > >>>>>>>>>>>>>>>>> only have a gauge metric exposing the last
>> > > >>>>>>>>> fetchTime/emitTime
>> > > >>>>>>>>>>>>>>>>> that is
>> > > >>>>>>>>>>>>>>>>> regularly reported to the backend (Prometheus),
>> > where a
>> > > >>>>>>> user
>> > > >>>>>>>>>>>>>>>>> could build
>> > > >>>>>>>>>>>>>>>>> a histogram of his choosing when/if he wants it.
>> > > >>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>> Not sure if such downsampling works. As an example,
>> if
>> > a
>> > > >> user
>> > > >>>>>>>>>>>>>>>>> complains that there are some intermittent latency
>> > spikes
>> > > >>>>>>> (maybe
>> > > >>>>>>>>>>>>>> a
>> > > >>>>>>>>>>>>>>>>> few records in 10 seconds) in their processing
>> system.
>> > > >>>>> Having a
>> > > >>>>>>>>>>>>>>>>> Gauge sampling instantaneous latency seems unlikely
>> > > useful.
>> > > >>>>>>>>>>>>>>>>> However by looking at actual 99.9 percentile latency
>> > > might
>> > > >>>>>>> help.
>> > > >>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>> Thanks,
>> > > >>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>> Jiangjie (Becket) Qin
>> > > >>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>> On Fri, Feb 22, 2019 at 9:30 PM Chesnay Schepler
>> > > >>>>>>>>>>>>>>>>> <chesnay@apache.org <ma...@apache.org>>
>> > wrote:
>> > > >>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>> Re: over complication of implementation.
>> > > >>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>> I think I get understand better know what you're
>> > > >> shooting
>> > > >>>>>>>>>>>>>> for,
>> > > >>>>>>>>>>>>>>>>> effectively something like the
>> OperatorIOMetricGroup.
>> > > >>>>>>>>>>>>>>>>> But still, re-define setupConnectorMetrics() to
>> > accept
>> > > a
>> > > >>>>>>> set
>> > > >>>>>>>>>>>>>>>>> of flags
>> > > >>>>>>>>>>>>>>>>> for counters/meters(ans _possibly_ histograms)
>> along
>> > > >>>>> with a
>> > > >>>>>>>>>>>>>>>>> set of
>> > > >>>>>>>>>>>>>>>>> well-defined Optional<Gauge<?>>, and return the
>> > group.
>> > > >>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>> Solves all issues as far as i can tell:
>> > > >>>>>>>>>>>>>>>>> 1) no metrics must be created manually (except
>> > Gauges,
>> > > >>>>>>> which
>> > > >>>>>>>>>>>>>>> are
>> > > >>>>>>>>>>>>>>>>> effectively just Suppliers and you can't get
>> around
>> > > >>>>> this),
>> > > >>>>>>>>>>>>>>>>> 2) additional metrics can be registered on the
>> > returned
>> > > >>>>>>>>>>>>>> group,
>> > > >>>>>>>>>>>>>>>>> 3) see 1),
>> > > >>>>>>>>>>>>>>>>> 4) single place where metrics are registered
>> except
>> > > >>>>>>>>>>>>>>>>> connector-specific
>> > > >>>>>>>>>>>>>>>>> ones (which we can't really avoid).
>> > > >>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>> Re: Histogram
>> > > >>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>> 1) As an example, whether "numRecordsIn" is
>> exposed
>> > as
>> > > a
>> > > >>>>>>>>>>>>>>>>> Counter or a
>> > > >>>>>>>>>>>>>>>>> Gauge should be irrelevant. So far we're using the
>> > > >> metric
>> > > >>>>>>>>>>>>>> type
>> > > >>>>>>>>>>>>>>>>> that is
>> > > >>>>>>>>>>>>>>>>> the most convenient at exposing a given value. If
>> > there
>> > > >>>>> is
>> > > >>>>>>>>>>>>>>>>> some backing
>> > > >>>>>>>>>>>>>>>>> data-structure that we want to expose some data
>> from
>> > we
>> > > >>>>>>>>>>>>>>>>> typically opt
>> > > >>>>>>>>>>>>>>>>> for a Gauge, as otherwise we're just mucking
>> around
>> > > with
>> > > >>>>>>> the
>> > > >>>>>>>>>>>>>>>>> Meter/Counter API to get it to match. Similarly,
>> if
>> > we
>> > > >>>>> want
>> > > >>>>>>>>>>>>>> to
>> > > >>>>>>>>>>>>>>>>> count
>> > > >>>>>>>>>>>>>>>>> something but no current count exists we typically
>> > > added
>> > > >>>>> a
>> > > >>>>>>>>>>>>>>>>> Counter.
>> > > >>>>>>>>>>>>>>>>> That's why attaching semantics to metric types
>> makes
>> > > >>>>> little
>> > > >>>>>>>>>>>>>>>>> sense (but
>> > > >>>>>>>>>>>>>>>>> unfortunately several reporters already do it);
>> for
>> > > >>>>>>>>>>>>>>>>> counters/meters
>> > > >>>>>>>>>>>>>>>>> certainly, but the majority of metrics are gauges.
>> > > >>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>> 2) I'm talking about time-series databases like
>> > > >>>>> Prometheus.
>> > > >>>>>>>>>>>>>> We
>> > > >>>>>>>>>>>>>>>>> would
>> > > >>>>>>>>>>>>>>>>> only have a gauge metric exposing the last
>> > > >>>>>>>>> fetchTime/emitTime
>> > > >>>>>>>>>>>>>>>>> that is
>> > > >>>>>>>>>>>>>>>>> regularly reported to the backend (Prometheus),
>> > where a
>> > > >>>>>>> user
>> > > >>>>>>>>>>>>>>>>> could build
>> > > >>>>>>>>>>>>>>>>> a histogram of his choosing when/if he wants it.
>> > > >>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>> On 22.02.2019 13:57, Becket Qin wrote:
>> > > >>>>>>>>>>>>>>>>>> Hi Chesnay,
>> > > >>>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>>> Thanks for the explanation.
>> > > >>>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>>> ** Re: FLIP
>> > > >>>>>>>>>>>>>>>>>> I might have misunderstood this, but it seems that
>> > > "major
>> > > >>>>>>>>>>>>>>>>> changes" are well
>> > > >>>>>>>>>>>>>>>>>> defined in FLIP. The full contents is following:
>> > > >>>>>>>>>>>>>>>>>> What is considered a "major change" that needs a
>> FLIP?
>> > > >>>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>>> Any of the following should be considered a major
>> > > change:
>> > > >>>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>>> - Any major new feature, subsystem, or piece of
>> > > >>>>>>>>>>>>>>>>> functionality
>> > > >>>>>>>>>>>>>>>>>> - *Any change that impacts the public interfaces of
>> > the
>> > > >>>>>>>>>>>>>>>>> project*
>> > > >>>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>>> What are the "public interfaces" of the project?
>> > > >>>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>>> *All of the following are public interfaces *that
>> > people
>> > > >>>>>>>>>>>>>>>>> build around:
>> > > >>>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>>> - DataStream and DataSet API, including classes
>> > related
>> > > >>>>>>>>>>>>>>>>> to that, such as
>> > > >>>>>>>>>>>>>>>>>> StreamExecutionEnvironment
>> > > >>>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>>> - Classes marked with the @Public annotation
>> > > >>>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>>> - On-disk binary formats, such as
>> > > >>>>>>>>>>>>>> checkpoints/savepoints
>> > > >>>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>>> - User-facing scripts/command-line tools, i.e.
>> > > >>>>>>>>>>>>>>>>> bin/flink, Yarn scripts,
>> > > >>>>>>>>>>>>>>>>>> Mesos scripts
>> > > >>>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>>> - Configuration settings
>> > > >>>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>>> - *Exposed monitoring information*
>> > > >>>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>>> So any monitoring information change is considered
>> as
>> > > >>>>>>>>>>>>>> public
>> > > >>>>>>>>>>>>>>>>> interface, and
>> > > >>>>>>>>>>>>>>>>>> any public interface change is considered as a
>> "major
>> > > >>>>>>>>>>>>>>> change".
>> > > >>>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>>> ** Re: over complication of implementation.
>> > > >>>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>>> Although this is more of implementation details
>> that
>> > is
>> > > >> not
>> > > >>>>>>>>>>>>>>>>> covered by the
>> > > >>>>>>>>>>>>>>>>>> FLIP. But it may be worth discussing.
>> > > >>>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>>> First of all, I completely agree that we should use
>> > the
>> > > >>>>>>>>>>>>>>>>> simplest way to
>> > > >>>>>>>>>>>>>>>>>> achieve our goal. To me the goal is the following:
>> > > >>>>>>>>>>>>>>>>>> 1. Clear connector conventions and interfaces.
>> > > >>>>>>>>>>>>>>>>>> 2. The easiness of creating a connector.
>> > > >>>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>>> Both of them are important to the prosperity of the
>> > > >>>>>>>>>>>>>>>>> connector ecosystem. So
>> > > >>>>>>>>>>>>>>>>>> I'd rather abstract as much as possible on our
>> side to
>> > > >> make
>> > > >>>>>>>>>>>>>>>>> the connector
>> > > >>>>>>>>>>>>>>>>>> developer's work lighter. Given this goal, a static
>> > util
>> > > >>>>>>>>>>>>>>>>> method approach
>> > > >>>>>>>>>>>>>>>>>> might have a few drawbacks:
>> > > >>>>>>>>>>>>>>>>>> 1. Users still have to construct the metrics by
>> > > >> themselves.
>> > > >>>>>>>>>>>>>>>>> (And note that
>> > > >>>>>>>>>>>>>>>>>> this might be erroneous by itself. For example, a
>> > > customer
>> > > >>>>>>>>>>>>>>>>> wrapper around
>> > > >>>>>>>>>>>>>>>>>> dropwizard meter maybe used instead of MeterView).
>> > > >>>>>>>>>>>>>>>>>> 2. When connector specific metrics are added, it is
>> > > >>>>>>>>>>>>>>>>> difficult to enforce
>> > > >>>>>>>>>>>>>>>>>> the scope to be the same as standard metrics.
>> > > >>>>>>>>>>>>>>>>>> 3. It seems that a method proliferation is
>> inevitable
>> > if
>> > > >> we
>> > > >>>>>>>>>>>>>>>>> want to apply
>> > > >>>>>>>>>>>>>>>>>> sanity checks. e.g. The metric of numBytesIn was
>> not
>> > > >>>>>>>>>>>>>>>>> registered for a meter.
>> > > >>>>>>>>>>>>>>>>>> 4. Metrics are still defined in random places and
>> hard
>> > > to
>> > > >>>>>>>>>>>>>>>> track.
>> > > >>>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>>> The current PR I had was inspired by the Config
>> system
>> > > in
>> > > >>>>>>>>>>>>>>>>> Kafka, which I
>> > > >>>>>>>>>>>>>>>>>> found pretty handy. In fact it is not only used by
>> > Kafka
>> > > >>>>>>>>>>>>>>>>> itself but even
>> > > >>>>>>>>>>>>>>>>>> some other projects that depend on Kafka. I am not
>> > > saying
>> > > >>>>>>>>>>>>>>>>> this approach is
>> > > >>>>>>>>>>>>>>>>>> perfect. But I think it worths to save the work for
>> > > >>>>>>>>>>>>>>>>> connector writers and
>> > > >>>>>>>>>>>>>>>>>> encourage more systematic implementation. That
>> being
>> > > said,
>> > > >>>>>>>>>>>>>> I
>> > > >>>>>>>>>>>>>>>>> am fully open
>> > > >>>>>>>>>>>>>>>>>> to suggestions.
>> > > >>>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>>> Re: Histogram
>> > > >>>>>>>>>>>>>>>>>> I think there are two orthogonal questions around
>> > those
>> > > >>>>>>>>>>>>>>>> metrics:
>> > > >>>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>>> 1. Regardless of the metric type, by just looking
>> at
>> > the
>> > > >>>>>>>>>>>>>>>>> meaning of a
>> > > >>>>>>>>>>>>>>>>>> metric, is generic to all connectors? If the
>> answer is
>> > > >> yes,
>> > > >>>>>>>>>>>>>>>>> we should
>> > > >>>>>>>>>>>>>>>>>> include the metric into the convention. No matter
>> > > whether
>> > > >>>>>>>>>>>>>> we
>> > > >>>>>>>>>>>>>>>>> include it
>> > > >>>>>>>>>>>>>>>>>> into the convention or not, some connector
>> > > implementations
>> > > >>>>>>>>>>>>>>>>> will emit such
>> > > >>>>>>>>>>>>>>>>>> metric. It is better to have a convention than
>> letting
>> > > >> each
>> > > >>>>>>>>>>>>>>>>> connector do
>> > > >>>>>>>>>>>>>>>>>> random things.
>> > > >>>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>>> 2. If a standard metric is a histogram, what
>> should we
>> > > do?
>> > > >>>>>>>>>>>>>>>>>> I agree that we should make it clear that using
>> > > histograms
>> > > >>>>>>>>>>>>>>>>> will have
>> > > >>>>>>>>>>>>>>>>>> performance risk. But I do see histogram is useful
>> in
>> > > some
>> > > >>>>>>>>>>>>>>>>> fine-granularity
>> > > >>>>>>>>>>>>>>>>>> debugging where one do not have the luxury to stop
>> the
>> > > >>>>>>>>>>>>>>>>> system and inject
>> > > >>>>>>>>>>>>>>>>>> more inspection code. So the workaround I am
>> thinking
>> > is
>> > > >> to
>> > > >>>>>>>>>>>>>>>>> provide some
>> > > >>>>>>>>>>>>>>>>>> implementation suggestions. Assume later on we
>> have a
>> > > >>>>>>>>>>>>>>>>> mechanism of
>> > > >>>>>>>>>>>>>>>>>> selective metrics. In the abstract metrics class we
>> > can
>> > > >>>>>>>>>>>>>>>>> disable those
>> > > >>>>>>>>>>>>>>>>>> metrics by default individual connector writers
>> does
>> > not
>> > > >>>>>>>>>>>>>>>>> have to do
>> > > >>>>>>>>>>>>>>>>>> anything (this is another advantage of having an
>> > > >>>>>>>>>>>>>>>>> AbstractMetrics instead of
>> > > >>>>>>>>>>>>>>>>>> static util methods.)
>> > > >>>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>>> I am not sure I fully understand the histogram in
>> the
>> > > >>>>>>>>>>>>>>>>> backend approach. Can
>> > > >>>>>>>>>>>>>>>>>> you explain a bit more? Do you mean emitting the
>> raw
>> > > data,
>> > > >>>>>>>>>>>>>>>>> e.g. fetchTime
>> > > >>>>>>>>>>>>>>>>>> and emitTime with each record and let the histogram
>> > > >>>>>>>>>>>>>>>>> computation happen in
>> > > >>>>>>>>>>>>>>>>>> the background? Or let the processing thread
>> putting
>> > the
>> > > >>>>>>>>>>>>>>>>> values into a
>> > > >>>>>>>>>>>>>>>>>> queue and have a separate thread polling from the
>> > queue
>> > > >> and
>> > > >>>>>>>>>>>>>>>>> add them into
>> > > >>>>>>>>>>>>>>>>>> the histogram?
>> > > >>>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>>> Thanks,
>> > > >>>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>>> Jiangjie (Becket) Qin
>> > > >>>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>>> On Fri, Feb 22, 2019 at 4:34 PM Chesnay Schepler
>> > > >>>>>>>>>>>>>>>>> <chesnay@apache.org <ma...@apache.org>>
>> > > wrote:
>> > > >>>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>>>> Re: Flip
>> > > >>>>>>>>>>>>>>>>>>> The very first line under both the main header and
>> > > >> Purpose
>> > > >>>>>>>>>>>>>>>>> section
>> > > >>>>>>>>>>>>>>>>>>> describe Flips as "major changes", which this
>> isn't.
>> > > >>>>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>>>> Re: complication
>> > > >>>>>>>>>>>>>>>>>>> I'm not arguing against standardization, but
>> again an
>> > > >>>>>>>>>>>>>>>>> over-complicated
>> > > >>>>>>>>>>>>>>>>>>> implementation when a static utility method would
>> be
>> > > >>>>>>>>>>>>>>>>> sufficient.
>> > > >>>>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>>>> public static void setupConnectorMetrics(
>> > > >>>>>>>>>>>>>>>>>>> MetricGroup operatorMetricGroup,
>> > > >>>>>>>>>>>>>>>>>>> String connectorName,
>> > > >>>>>>>>>>>>>>>>>>> Optional<Gauge<Long>> numRecordsIn,
>> > > >>>>>>>>>>>>>>>>>>> ...)
>> > > >>>>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>>>> This gives you all you need:
>> > > >>>>>>>>>>>>>>>>>>> * a well-defined set of metrics for a connector to
>> > > opt-in
>> > > >>>>>>>>>>>>>>>>>>> * standardized naming schemes for scope and
>> > individual
>> > > >>>>>>>>>>>>>>> metrics
>> > > >>>>>>>>>>>>>>>>>>> * standardize metric types (although personally
>> I'm
>> > not
>> > > >>>>>>>>>>>>>>>>> interested in that
>> > > >>>>>>>>>>>>>>>>>>> since metric types should be considered syntactic
>> > > sugar)
>> > > >>>>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>>>> Re: Configurable Histogram
>> > > >>>>>>>>>>>>>>>>>>> If anything they _must_ be turned off by default,
>> but
>> > > the
>> > > >>>>>>>>>>>>>>>>> metric system is
>> > > >>>>>>>>>>>>>>>>>>> already exposing so many options that I'm not too
>> > keen
>> > > on
>> > > >>>>>>>>>>>>>>>>> adding even more.
>> > > >>>>>>>>>>>>>>>>>>> You have also only addressed my first argument
>> > against
>> > > >>>>>>>>>>>>>>>>> histograms
>> > > >>>>>>>>>>>>>>>>>>> (performance), the second one still stands
>> (calculate
>> > > >>>>>>>>>>>>>>>>> histogram in metric
>> > > >>>>>>>>>>>>>>>>>>> backends instead).
>> > > >>>>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>>>> On 21.02.2019 16:27, Becket Qin wrote:
>> > > >>>>>>>>>>>>>>>>>>>> Hi Chesnay,
>> > > >>>>>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>>>>> Thanks for the comments. I think this is worthy
>> of a
>> > > >> FLIP
>> > > >>>>>>>>>>>>>>>>> because it is
>> > > >>>>>>>>>>>>>>>>>>>> public API. According to the FLIP description a
>> FlIP
>> > > is
>> > > >>>>>>>>>>>>>>>>> required in case
>> > > >>>>>>>>>>>>>>>>>>> of:
>> > > >>>>>>>>>>>>>>>>>>>> - Any change that impacts the public interfaces
>> of
>> > > >>>>>>>>>>>>>>>>> the project
>> > > >>>>>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>>>>> and the following entry is found in the
>> definition
>> > of
>> > > >>>>>>>>>>>>>>>>> "public interface".
>> > > >>>>>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>>>>> - Exposed monitoring information
>> > > >>>>>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>>>>> Metrics are critical to any production system.
>> So a
>> > > >> clear
>> > > >>>>>>>>>>>>>>>>> metric
>> > > >>>>>>>>>>>>>>>>>>> definition
>> > > >>>>>>>>>>>>>>>>>>>> is important for any serious users. For an
>> > > organization
>> > > >>>>>>>>>>>>>>>>> with large Flink
>> > > >>>>>>>>>>>>>>>>>>>> installation, change in metrics means great
>> amount
>> > of
>> > > >>>>>>>>>>>>>>>>> work. So such
>> > > >>>>>>>>>>>>>>>>>>> changes
>> > > >>>>>>>>>>>>>>>>>>>> do need to be fully discussed and documented.
>> > > >>>>>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>>>>> ** Re: Histogram.
>> > > >>>>>>>>>>>>>>>>>>>> We can discuss whether there is a better way to
>> > expose
>> > > >>>>>>>>>>>>>>>>> metrics that are
>> > > >>>>>>>>>>>>>>>>>>>> suitable for histograms. My micro-benchmark on
>> > various
>> > > >>>>>>>>>>>>>>>>> histogram
>> > > >>>>>>>>>>>>>>>>>>>> implementations also indicates that they are
>> > > >>>>>>>>>>>>>> significantly
>> > > >>>>>>>>>>>>>>>>> slower than
>> > > >>>>>>>>>>>>>>>>>>>> other metric types. But I don't think that means
>> > never
>> > > >>>>>>>>>>>>>> use
>> > > >>>>>>>>>>>>>>>>> histogram, but
>> > > >>>>>>>>>>>>>>>>>>>> means use it with caution. For example, we can
>> > suggest
>> > > >>>>>>>>>>>>>> the
>> > > >>>>>>>>>>>>>>>>>>> implementations
>> > > >>>>>>>>>>>>>>>>>>>> to turn them off by default and only turn it on
>> for
>> > a
>> > > >>>>>>>>>>>>>>>>> small amount of
>> > > >>>>>>>>>>>>>>>>>>> time
>> > > >>>>>>>>>>>>>>>>>>>> when performing some micro-debugging.
>> > > >>>>>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>>>>> ** Re: complication:
>> > > >>>>>>>>>>>>>>>>>>>> Connector conventions are essential for Flink
>> > > ecosystem.
>> > > >>>>>>>>>>>>>>>>> Flink connectors
>> > > >>>>>>>>>>>>>>>>>>>> pool is probably the most important part of
>> Flink,
>> > > just
>> > > >>>>>>>>>>>>>>>>> like any other
>> > > >>>>>>>>>>>>>>>>>>> data
>> > > >>>>>>>>>>>>>>>>>>>> system. Clear conventions of connectors will help
>> > > build
>> > > >>>>>>>>>>>>>>>>> Flink ecosystem
>> > > >>>>>>>>>>>>>>>>>>> in
>> > > >>>>>>>>>>>>>>>>>>>> a more organic way.
>> > > >>>>>>>>>>>>>>>>>>>> Take the metrics convention as an example,
>> imagine
>> > > >>>>>>>>>>>>>> someone
>> > > >>>>>>>>>>>>>>>>> has developed
>> > > >>>>>>>>>>>>>>>>>>> a
>> > > >>>>>>>>>>>>>>>>>>>> Flink connector for System foo, and another
>> > developer
>> > > >> may
>> > > >>>>>>>>>>>>>>>>> have developed
>> > > >>>>>>>>>>>>>>>>>>> a
>> > > >>>>>>>>>>>>>>>>>>>> monitoring and diagnostic framework for Flink
>> which
>> > > >>>>>>>>>>>>>>>>> analyzes the Flink
>> > > >>>>>>>>>>>>>>>>>>> job
>> > > >>>>>>>>>>>>>>>>>>>> performance based on metrics. With a clear metric
>> > > >>>>>>>>>>>>>>>>> convention, those two
>> > > >>>>>>>>>>>>>>>>>>>> projects could be developed independently. Once
>> > users
>> > > >> put
>> > > >>>>>>>>>>>>>>>>> them together,
>> > > >>>>>>>>>>>>>>>>>>>> it would work without additional modifications.
>> This
>> > > >>>>>>>>>>>>>>>>> cannot be easily
>> > > >>>>>>>>>>>>>>>>>>>> achieved by just defining a few constants.
>> > > >>>>>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>>>>> ** Re: selective metrics:
>> > > >>>>>>>>>>>>>>>>>>>> Sure, we can discuss that in a separate thread.
>> > > >>>>>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>>>>> @Dawid
>> > > >>>>>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>>>>> ** Re: latency / fetchedLatency
>> > > >>>>>>>>>>>>>>>>>>>> The primary purpose of establish such a
>> convention
>> > is
>> > > to
>> > > >>>>>>>>>>>>>>>>> help developers
>> > > >>>>>>>>>>>>>>>>>>>> write connectors in a more compatible way. The
>> > > >> convention
>> > > >>>>>>>>>>>>>>>>> is supposed to
>> > > >>>>>>>>>>>>>>>>>>> be
>> > > >>>>>>>>>>>>>>>>>>>> defined more proactively. So when look at the
>> > > >> convention,
>> > > >>>>>>>>>>>>>>>>> it seems more
>> > > >>>>>>>>>>>>>>>>>>>> important to see if the concept is applicable to
>> > > >>>>>>>>>>>>>>>>> connectors in general.
>> > > >>>>>>>>>>>>>>>>>>> It
>> > > >>>>>>>>>>>>>>>>>>>> might be true so far only Kafka connector reports
>> > > >>>>>>>>>>>>>> latency.
>> > > >>>>>>>>>>>>>>>>> But there
>> > > >>>>>>>>>>>>>>>>>>> might
>> > > >>>>>>>>>>>>>>>>>>>> be hundreds of other connector implementations in
>> > the
>> > > >>>>>>>>>>>>>>>>> Flink ecosystem,
>> > > >>>>>>>>>>>>>>>>>>>> though not in the Flink repo, and some of them
>> also
>> > > >> emits
>> > > >>>>>>>>>>>>>>>>> latency. I
>> > > >>>>>>>>>>>>>>>>>>> think
>> > > >>>>>>>>>>>>>>>>>>>> a lot of other sources actually also has an
>> append
>> > > >>>>>>>>>>>>>>>>> timestamp. e.g.
>> > > >>>>>>>>>>>>>>>>>>> database
>> > > >>>>>>>>>>>>>>>>>>>> bin logs and some K-V stores. So I wouldn't be
>> > > surprised
>> > > >>>>>>>>>>>>>>>>> if some database
>> > > >>>>>>>>>>>>>>>>>>>> connector can also emit latency metrics.
>> > > >>>>>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>>>>> Thanks,
>> > > >>>>>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>>>>> Jiangjie (Becket) Qin
>> > > >>>>>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>>>>> On Thu, Feb 21, 2019 at 10:14 PM Chesnay Schepler
>> > > >>>>>>>>>>>>>>>>> <chesnay@apache.org <ma...@apache.org>>
>> > > >>>>>>>>>>>>>>>>>>>> wrote:
>> > > >>>>>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>>>>>> Regarding 2) It doesn't make sense to
>> investigate
>> > > this
>> > > >>>>>>>>>>>>>> as
>> > > >>>>>>>>>>>>>>>>> part of this
>> > > >>>>>>>>>>>>>>>>>>>>> FLIP. This is something that could be of
>> interest
>> > for
>> > > >>>>>>>>>>>>>> the
>> > > >>>>>>>>>>>>>>>>> entire metric
>> > > >>>>>>>>>>>>>>>>>>>>> system, and should be designed for as such.
>> > > >>>>>>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>>>>>> Regarding the proposal as a whole:
>> > > >>>>>>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>>>>>> Histogram metrics shall not be added to the
>> core of
>> > > >>>>>>>>>>>>>>>>> Flink. They are
>> > > >>>>>>>>>>>>>>>>>>>>> significantly more expensive than other metrics,
>> > and
>> > > >>>>>>>>>>>>>>>>> calculating
>> > > >>>>>>>>>>>>>>>>>>>>> histograms in the application is regarded as an
>> > > >>>>>>>>>>>>>>>>> anti-pattern by several
>> > > >>>>>>>>>>>>>>>>>>>>> metric backends, who instead recommend to expose
>> > the
>> > > >> raw
>> > > >>>>>>>>>>>>>>>>> data and
>> > > >>>>>>>>>>>>>>>>>>>>> calculate the histogram in the backend.
>> > > >>>>>>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>>>>>> Second, this seems overly complicated. Given
>> that
>> > we
>> > > >>>>>>>>>>>>>>>>> already established
>> > > >>>>>>>>>>>>>>>>>>>>> that not all connectors will export all metrics
>> we
>> > > are
>> > > >>>>>>>>>>>>>>>>> effectively
>> > > >>>>>>>>>>>>>>>>>>>>> reducing this down to a consistent naming
>> scheme.
>> > We
>> > > >>>>>>>>>>>>>>>>> don't need anything
>> > > >>>>>>>>>>>>>>>>>>>>> sophisticated for that; basically just a few
>> > > constants
>> > > >>>>>>>>>>>>>>>>> that all
>> > > >>>>>>>>>>>>>>>>>>>>> connectors use.
>> > > >>>>>>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>>>>>> I'm not convinced that this is worthy of a FLIP.
>> > > >>>>>>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>>>>>> On 21.02.2019 14:26, Dawid Wysakowicz wrote:
>> > > >>>>>>>>>>>>>>>>>>>>>> Hi,
>> > > >>>>>>>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>>>>>>> Ad 1. In general I undestand and I agree. But
>> > those
>> > > >>>>>>>>>>>>>>>>> particular metrics
>> > > >>>>>>>>>>>>>>>>>>>>>> (latency, fetchLatency), right now would only
>> be
>> > > >>>>>>>>>>>>>>>>> reported if user uses
>> > > >>>>>>>>>>>>>>>>>>>>>> KafkaConsumer with internal timestampAssigner
>> with
>> > > >>>>>>>>>>>>>>>>> StreamCharacteristic
>> > > >>>>>>>>>>>>>>>>>>>>>> set to EventTime, right? That sounds like a
>> very
>> > > >>>>>>>>>>>>>>>>> specific case. I am
>> > > >>>>>>>>>>>>>>>>>>> not
>> > > >>>>>>>>>>>>>>>>>>>>>> sure if we should introduce a generic metric
>> that
>> > > will
>> > > >>>>>>>>>>>>>> be
>> > > >>>>>>>>>>>>>>>>>>>>>> disabled/absent for most of implementations.
>> > > >>>>>>>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>>>>>>> Ad.2 That sounds like an orthogonal issue, that
>> > > might
>> > > >>>>>>>>>>>>>>>>> make sense to
>> > > >>>>>>>>>>>>>>>>>>>>>> investigate in the future.
>> > > >>>>>>>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>>>>>>> Best,
>> > > >>>>>>>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>>>>>>> Dawid
>> > > >>>>>>>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>>>>>>> On 21/02/2019 13:20, Becket Qin wrote:
>> > > >>>>>>>>>>>>>>>>>>>>>>> Hi Dawid,
>> > > >>>>>>>>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>>>>>>>> Thanks for the feedback. That makes sense to
>> me.
>> > > >> There
>> > > >>>>>>>>>>>>>>>>> are two cases
>> > > >>>>>>>>>>>>>>>>>>> to
>> > > >>>>>>>>>>>>>>>>>>>>> be
>> > > >>>>>>>>>>>>>>>>>>>>>>> addressed.
>> > > >>>>>>>>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>>>>>>>> 1. The metrics are supposed to be a guidance.
>> It
>> > is
>> > > >>>>>>>>>>>>>>>>> likely that a
>> > > >>>>>>>>>>>>>>>>>>>>> connector
>> > > >>>>>>>>>>>>>>>>>>>>>>> only supports some but not all of the
>> metrics. In
>> > > >> that
>> > > >>>>>>>>>>>>>>>>> case, each
>> > > >>>>>>>>>>>>>>>>>>>>> connector
>> > > >>>>>>>>>>>>>>>>>>>>>>> implementation should have the freedom to
>> decide
>> > > >> which
>> > > >>>>>>>>>>>>>>>>> metrics are
>> > > >>>>>>>>>>>>>>>>>>>>>>> reported. For the metrics that are supported,
>> the
>> > > >>>>>>>>>>>>>>>>> guidance should be
>> > > >>>>>>>>>>>>>>>>>>>>>>> followed.
>> > > >>>>>>>>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>>>>>>>> 2. Sometimes users may want to disable certain
>> > > >> metrics
>> > > >>>>>>>>>>>>>>>>> for some reason
>> > > >>>>>>>>>>>>>>>>>>>>>>> (e.g. performance / reprocessing of data). A
>> > > generic
>> > > >>>>>>>>>>>>>>>>> mechanism should
>> > > >>>>>>>>>>>>>>>>>>> be
>> > > >>>>>>>>>>>>>>>>>>>>>>> provided to allow user choose which metrics
>> are
>> > > >>>>>>>>>>>>>>>>> reported. This
>> > > >>>>>>>>>>>>>>>>>>> mechanism
>> > > >>>>>>>>>>>>>>>>>>>>>>> should also be honored by the connector
>> > > >>>>>>>>>>>>>> implementations.
>> > > >>>>>>>>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>>>>>>>> Does this sound reasonable to you?
>> > > >>>>>>>>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>>>>>>>> Thanks,
>> > > >>>>>>>>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>>>>>>>> Jiangjie (Becket) Qin
>> > > >>>>>>>>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>>>>>>>> On Thu, Feb 21, 2019 at 4:22 PM Dawid
>> Wysakowicz
>> > <
>> > > >>>>>>>>>>>>>>>>>>>>> dwysakowicz@apache.org <mailto:
>> > > dwysakowicz@apache.org
>> > > >>>>
>> > > >>>>>>>>>>>>>>>>>>>>>>> wrote:
>> > > >>>>>>>>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>>>>>>>>> Hi,
>> > > >>>>>>>>>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>>>>>>>>> Generally I like the idea of having a
>> unified,
>> > > >>>>>>>>>>>>>>>>> standard set of
>> > > >>>>>>>>>>>>>>>>>>> metrics
>> > > >>>>>>>>>>>>>>>>>>>>> for
>> > > >>>>>>>>>>>>>>>>>>>>>>>> all connectors. I have some slight concerns
>> > about
>> > > >>>>>>>>>>>>>>>>> fetchLatency and
>> > > >>>>>>>>>>>>>>>>>>>>>>>> latency though. They are computed based on
>> > > EventTime
>> > > >>>>>>>>>>>>>>>>> which is not a
>> > > >>>>>>>>>>>>>>>>>>>>> purely
>> > > >>>>>>>>>>>>>>>>>>>>>>>> technical feature. It depends often on some
>> > > business
>> > > >>>>>>>>>>>>>>>>> logic, might be
>> > > >>>>>>>>>>>>>>>>>>>>> absent
>> > > >>>>>>>>>>>>>>>>>>>>>>>> or defined after source. Those metrics could
>> > also
>> > > >>>>>>>>>>>>>>>>> behave in a weird
>> > > >>>>>>>>>>>>>>>>>>>>> way in
>> > > >>>>>>>>>>>>>>>>>>>>>>>> case of replaying backlog. Therefore I am not
>> > sure
>> > > >> if
>> > > >>>>>>>>>>>>>>>>> we should
>> > > >>>>>>>>>>>>>>>>>>> include
>> > > >>>>>>>>>>>>>>>>>>>>>>>> those metrics by default. Maybe we could at
>> > least
>> > > >>>>>>>>>>>>>>>>> introduce a feature
>> > > >>>>>>>>>>>>>>>>>>>>>>>> switch for them? What do you think?
>> > > >>>>>>>>>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>>>>>>>>> Best,
>> > > >>>>>>>>>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>>>>>>>>> Dawid
>> > > >>>>>>>>>>>>>>>>>>>>>>>> On 21/02/2019 03:13, Becket Qin wrote:
>> > > >>>>>>>>>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>>>>>>>>> Bump. If there is no objections to the
>> proposed
>> > > >>>>>>>>>>>>>>>>> metrics. I'll start a
>> > > >>>>>>>>>>>>>>>>>>>>>>>> voting thread later toady.
>> > > >>>>>>>>>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>>>>>>>>> Thanks,
>> > > >>>>>>>>>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>>>>>>>>> Jiangjie (Becket) Qin
>> > > >>>>>>>>>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>>>>>>>>> On Mon, Feb 11, 2019 at 8:17 PM Becket Qin
>> > > >>>>>>>>>>>>>>>>> <becket.qin@gmail.com <mailto:
>> becket.qin@gmail.com>>
>> > <
>> > > >>>>>>>>>>>>>>>>>>>>> becket.qin@gmail.com <mailto:
>> becket.qin@gmail.com
>> > >>
>> > > >>>>>>>>>>>>>>> wrote:
>> > > >>>>>>>>>>>>>>>>>>>>>>>> Hi folks,
>> > > >>>>>>>>>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>>>>>>>>> I would like to start the FLIP discussion
>> thread
>> > > >>>>>>>>>>>>>> about
>> > > >>>>>>>>>>>>>>>>> standardize
>> > > >>>>>>>>>>>>>>>>>>> the
>> > > >>>>>>>>>>>>>>>>>>>>>>>> connector metrics.
>> > > >>>>>>>>>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>>>>>>>>> In short, we would like to provide a
>> convention
>> > of
>> > > >>>>>>>>>>>>>>>>> Flink connector
>> > > >>>>>>>>>>>>>>>>>>>>>>>> metrics. It will help simplify the monitoring
>> > and
>> > > >>>>>>>>>>>>>>>>> alerting on Flink
>> > > >>>>>>>>>>>>>>>>>>>>> jobs.
>> > > >>>>>>>>>>>>>>>>>>>>>>>> The FLIP link is following:
>> > > >>>>>>>>>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>
>> > > >>>>>>>>>
>> > > >>>>>>>
>> > > >>>>>
>> > > >>
>> > >
>> >
>> https://cwiki.apache.org/confluence/display/FLINK/FLIP-33%3A+Standardize+Connector+Metrics
>> > > >>>>>>>>>>>>>>>>>>>>>>>> Thanks,
>> > > >>>>>>>>>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>>>>>>>>> Jiangjie (Becket) Qin
>> > > >>>>>>>>>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>>>
>> > > >>>>>>>>>>>>
>> > > >>>>>>>>>>>>
>> > > >>>>>>>>>
>> > > >>>>>>>>>
>> > > >>>>>>>>>
>> > > >>>>>>>
>> > > >>>>>>>
>> > > >>>>>>>
>> > > >>>>>
>> > > >>>>>
>> > > >>
>> > > >>
>> > >
>> > >
>> >
>>
>>
>> --
>>
>> Konstantin Knauf
>>
>> https://twitter.com/snntrable
>>
>> https://github.com/knaufk
>>
>
Re: [DISCUSS] FLIP-33: Standardize connector metrics
Posted by Becket Qin <be...@gmail.com>.
On Tue, Sep 8, 2020 at 6:55 PM Konstantin Knauf <kn...@apache.org> wrote:
> Hi Becket,
>
> Thank you for picking up this FLIP. I have a few questions:
>
> * two thoughts on naming:
> * idleTime: In the meantime, a similar metric "idleTimeMsPerSecond" has
> been introduced in https://issues.apache.org/jira/browse/FLINK-16864. They
> have a similar name, but different definitions of idleness,
> e.g. "idleTimeMsPerSecond" considers the SourceTask idle, when it is
> backpressured. Can we make it clearer that these two metrics mean different
> things?
>
> * "current(Fetch)Latency" I am wondering if "eventTimeLag(Before|After)"
> is more descriptive/clear. What do others think?
>
> * Current(Fetch)Latency implies that the timestamps are directly
> extracted in the source connector, right? Will this be the default for
> FLIP-27 sources anyway?
>
> * Does FLIP-33 also include the implementation of these metrics (to the
> extent possible) for all connectors currently available in Apache Flink or
> is the "per-connector implementation" out-of-scope?
>
> Thanks,
>
> Konstantin
>
>
>
>
>
> On Fri, Sep 4, 2020 at 4:56 PM Becket Qin <be...@gmail.com> wrote:
>
> > Hi all,
> >
> > To complete the Source refactoring work, I'd like to revive this
> > discussion. Since the mail thread has been dormant for more than a year,
> > just to recap the motivation of the FLIP:
> >
> > 1. The FLIP proposes to standardize the connector metrics by giving
> > guidance on the metric specifications, including the name, type and
> meaning
> > of the metrics.
> > 2. It is OK for a connector to not emit some of the metrics in the metric
> > guidance, but if a metric of the same semantic is emitted, the
> > implementation should follow the guidance.
> > 3. It is OK for a connector to emit more metrics than what are listed in
> > the FLIP. This includes having an alias for a metric specified in the
> FLIP.
> > 4. We will implement some of the metrics out of the box in the default
> > implementation of FLIP-27, as long as it is applicable.
> >
> > The FLIP wiki is following:
> > https://cwiki.apache.org/confluence/display/FLINK/FLIP-33
> > %3A+Standardize+Connector+Metrics
> >
> > Any thoughts?
> >
> > Thanks,
> >
> > Jiangjie (Becket) Qin
> >
> >
> > On Fri, Jun 14, 2019 at 2:29 PM Piotr Nowojski <pi...@ververica.com>
> > wrote:
> >
> > > > we will need to revisit the convention list and adjust them
> accordingly
> > > when FLIP-27 is ready
> > >
> > >
> > > Yes, this sounds good :)
> > >
> > > Piotrek
> > >
> > > > On 13 Jun 2019, at 13:35, Becket Qin <be...@gmail.com> wrote:
> > > >
> > > > Hi Piotr,
> > > >
> > > > That's great to know. Chances are that we will need to revisit the
> > > > convention list and adjust them accordingly when FLIP-27 is ready, At
> > > that
> > > > point we can mark some of the metrics as available by default for
> > > > connectors implementing the new interface.
> > > >
> > > > Thanks,
> > > >
> > > > Jiangjie (Becket) Qin
> > > >
> > > > On Thu, Jun 13, 2019 at 3:51 PM Piotr Nowojski <pi...@ververica.com>
> > > wrote:
> > > >
> > > >> Thanks for driving this. I’ve just noticed one small thing. With new
> > > >> SourceReader interface Flink will be able to provide `idleTime`
> metric
> > > >> automatically.
> > > >>
> > > >> Piotrek
> > > >>
> > > >>> On 13 Jun 2019, at 03:30, Becket Qin <be...@gmail.com> wrote:
> > > >>>
> > > >>> Thanks all for the feedback and discussion.
> > > >>>
> > > >>> Since there wasn't any concern raised, I've started the voting
> thread
> > > for
> > > >>> this FLIP, but please feel free to continue the discussion here if
> > you
> > > >>> think something still needs to be addressed.
> > > >>>
> > > >>> Thanks,
> > > >>>
> > > >>> Jiangjie (Becket) Qin
> > > >>>
> > > >>>
> > > >>>
> > > >>> On Mon, Jun 10, 2019 at 9:10 AM Becket Qin <be...@gmail.com>
> > > wrote:
> > > >>>
> > > >>>> Hi Piotr,
> > > >>>>
> > > >>>> Thanks for the comments. Yes, you are right. Users will have to
> look
> > > at
> > > >>>> other metrics to decide whether the pipeline is healthy or not in
> > the
> > > >> first
> > > >>>> place before they can use the time-based metric to fix the
> > bottleneck.
> > > >>>>
> > > >>>> I agree that once we have FLIP-27 ready, some of the metrics can
> > just
> > > be
> > > >>>> reported by the abstract implementation.
> > > >>>>
> > > >>>> I've updated FLIP-33 wiki page to add the pendingBytes and
> > > >> pendingRecords
> > > >>>> metric. Please let me know if you have any concern over the
> updated
> > > >> metric
> > > >>>> convention proposal.
> > > >>>>
> > > >>>> @Chesnay Schepler <ch...@apache.org> @Stephan Ewen
> > > >>>> <st...@ververica.com> will you also have time to take a look at
> > the
> > > >>>> proposed metric convention? If there is no further concern I'll
> > start
> > > a
> > > >>>> voting thread for this FLIP in two days.
> > > >>>>
> > > >>>> Thanks,
> > > >>>>
> > > >>>> Jiangjie (Becket) Qin
> > > >>>>
> > > >>>>
> > > >>>>
> > > >>>> On Wed, Jun 5, 2019 at 6:54 PM Piotr Nowojski <
> piotr@ververica.com>
> > > >> wrote:
> > > >>>>
> > > >>>>> Hi Becket,
> > > >>>>>
> > > >>>>> Thanks for the answer :)
> > > >>>>>
> > > >>>>>> By time-based metric, I meant the portion of time spent on
> > producing
> > > >> the
> > > >>>>>> record to downstream. For example, a source connector can report
> > > that
> > > >>>>> it's
> > > >>>>>> spending 80% of time to emit record to downstream processing
> > > pipeline.
> > > >>>>> In
> > > >>>>>> another case, a sink connector may report that its spending 30%
> of
> > > >> time
> > > >>>>>> producing the records to the external system.
> > > >>>>>>
> > > >>>>>> This is in some sense equivalent to the buffer usage metric:
> > > >>>>>
> > > >>>>>> - 80% of time spent on emitting records to downstream --->
> > > downstream
> > > >>>>>> node is bottleneck ---> output buffer is probably full.
> > > >>>>>> - 30% of time spent on emitting records to downstream --->
> > > downstream
> > > >>>>>> node is not bottleneck ---> output buffer is probably not full.
> > > >>>>>
> > > >>>>> If by “time spent on emitting records to downstream” you
> understand
> > > >>>>> “waiting on back pressure”, then I see your point. And I agree
> that
> > > >> some
> > > >>>>> kind of ratio/time based metric gives you more information.
> However
> > > >> under
> > > >>>>> “time spent on emitting records to downstream” might be hidden
> the
> > > >>>>> following (extreme) situation:
> > > >>>>>
> > > >>>>> 1. Job is barely able to handle influx of records, there is 99%
> > > >>>>> CPU/resource usage in the cluster, but nobody is
> > > >>>>> bottlenecked/backpressured, all output buffers are empty,
> everybody
> > > is
> > > >>>>> waiting in 1% of it’s time for more records to process.
> > > >>>>> 2. 80% time can still be spent on "down stream operators”,
> because
> > > they
> > > >>>>> are the CPU intensive operations, but this doesn’t mean that
> > > >> increasing the
> > > >>>>> parallelism down the stream will help with anything there. To the
> > > >> contrary,
> > > >>>>> increasing parallelism of the source operator might help to
> > increase
> > > >>>>> resource utilisation up to 100%.
> > > >>>>>
> > > >>>>> However, this “time based/ratio” approach can be extended to
> > > in/output
> > > >>>>> buffer usage. Besides collecting an information that input/output
> > > >> buffer is
> > > >>>>> full/empty, we can probe profile how often are buffer empty/full.
> > If
> > > >> output
> > > >>>>> buffer is full 1% of times, there is almost no back pressure. If
> > it’s
> > > >> full
> > > >>>>> 80% of times, there is some back pressure, if it’s full 99.9% of
> > > times,
> > > >>>>> there is huge back pressure.
> > > >>>>>
> > > >>>>> Now for autoscaling you could compare the input & output buffers
> > fill
> > > >>>>> ratio:
> > > >>>>>
> > > >>>>> 1. Both are high, the source of bottleneck is down the stream
> > > >>>>> 2. Output is low, input is high, this is the bottleneck and the
> > > higher
> > > >>>>> the difference, the bigger source of bottleneck is this is
> > > >> operator/task
> > > >>>>> 3. Output is high, input is low - there was some load spike that
> we
> > > are
> > > >>>>> currently finishing to process
> > > >>>>>
> > > >>>>>
> > > >>>>>
> > > >>>>> But long story short, we are probably diverging from the topic of
> > > this
> > > >>>>> discussion, and we can discuss this at some later point.
> > > >>>>>
> > > >>>>> For now, for sources:
> > > >>>>>
> > > >>>>> as I wrote before, +1 for:
> > > >>>>> - pending.bytes, Gauge
> > > >>>>> - pending.messages, Gauge
> > > >>>>>
> > > >>>>> When we will be developing/discussing SourceReader from FLIP-27
> we
> > > >> might
> > > >>>>> then add:
> > > >>>>>
> > > >>>>> - in-memory.buffer.usage (0 - 100%)
> > > >>>>>
> > > >>>>> Which will be estimated automatically by Flink while user will be
> > > able
> > > >> to
> > > >>>>> override/provide better estimation.
> > > >>>>>
> > > >>>>> Piotrek
> > > >>>>>
> > > >>>>>> On 5 Jun 2019, at 05:42, Becket Qin <be...@gmail.com>
> wrote:
> > > >>>>>>
> > > >>>>>> Hi Piotr,
> > > >>>>>>
> > > >>>>>> Thanks for the explanation. Please see some clarifications
> below.
> > > >>>>>>
> > > >>>>>> By time-based metric, I meant the portion of time spent on
> > producing
> > > >> the
> > > >>>>>> record to downstream. For example, a source connector can report
> > > that
> > > >>>>> it's
> > > >>>>>> spending 80% of time to emit record to downstream processing
> > > pipeline.
> > > >>>>> In
> > > >>>>>> another case, a sink connector may report that its spending 30%
> of
> > > >> time
> > > >>>>>> producing the records to the external system.
> > > >>>>>>
> > > >>>>>> This is in some sense equivalent to the buffer usage metric:
> > > >>>>>> - 80% of time spent on emitting records to downstream --->
> > > downstream
> > > >>>>>> node is bottleneck ---> output buffer is probably full.
> > > >>>>>> - 30% of time spent on emitting records to downstream --->
> > > downstream
> > > >>>>>> node is not bottleneck ---> output buffer is probably not full.
> > > >>>>>>
> > > >>>>>> However, the time-based metric has a few advantages that the
> > buffer
> > > >>>>> usage
> > > >>>>>> metric may not have.
> > > >>>>>>
> > > >>>>>> 1. Buffer usage metric may not be applicable to all the
> connector
> > > >>>>>> implementations, while reporting time-based metric are always
> > > doable.
> > > >>>>>> Some source connectors may not have any input buffer, or they
> may
> > > use
> > > >>>>> some
> > > >>>>>> third party library that does not expose the input buffer at
> all.
> > > >>>>>> Similarly, for sink connectors, the implementation may not have
> > any
> > > >>>>> output
> > > >>>>>> buffer, or the third party library does not expose such buffer.
> > > >>>>>>
> > > >>>>>> 2. Although both type of metrics can detect bottleneck,
> time-based
> > > >>>>> metrics
> > > >>>>>> can be used to generate a more informed action to remove the
> > > >> bottleneck.
> > > >>>>>> For example, when the downstream is bottleneck, the output
> buffer
> > > >> usage
> > > >>>>>> metric is likely to be 100%, and the input buffer usage might be
> > 0%.
> > > >>>>> That
> > > >>>>>> means we don't know what is the suitable parallelism to lift the
> > > >>>>>> bottleneck. The time-based metric, on the other hand, would give
> > > >> useful
> > > >>>>>> information, e.g. if 80% of time was spent on emitting records,
> we
> > > can
> > > >>>>>> roughly increase the downstream node parallelism by 4 times.
> > > >>>>>>
> > > >>>>>> Admittedly, the time-based metrics are more expensive than
> buffer
> > > >>>>> usage. So
> > > >>>>>> we may have to do some sampling to reduce the cost. But in
> > general,
> > > >>>>> using
> > > >>>>>> time-based metrics seems worth adding.
> > > >>>>>>
> > > >>>>>> That being said, I don't think buffer usage metric and
> time-based
> > > >>>>> metrics
> > > >>>>>> are mutually exclusive. We can probably have both. It is just
> that
> > > in
> > > >>>>>> practice, features like auto-scaling might prefer time-based
> > metrics
> > > >> for
> > > >>>>>> the reason stated above.
> > > >>>>>>
> > > >>>>>>> 1. Define the metrics that would allow us to manually detect
> > > >>>>> bottlenecks.
> > > >>>>>> As I wrote, we already have them in most of the places, except
> of
> > > >>>>>> sources/sinks.
> > > >>>>>>> 2. Use those metrics, to automatically detect bottlenecks.
> > > Currently
> > > >> we
> > > >>>>>> are only automatically detecting back pressure and reporting it
> to
> > > the
> > > >>>>> user
> > > >>>>>> in web UI (is it exposed as a metric at all?). Detecting the
> root
> > > >> cause
> > > >>>>> of
> > > >>>>>> the back pressure (bottleneck) is one step further.
> > > >>>>>>> 3. Use the knowledge about where exactly the bottleneck is
> > located,
> > > >> to
> > > >>>>>> try to do something with it.
> > > >>>>>>
> > > >>>>>> As explained above, I think time-based metric also addresses
> item
> > 1
> > > >> and
> > > >>>>>> item 2.
> > > >>>>>>
> > > >>>>>> Any thoughts？
> > > >>>>>>
> > > >>>>>> Thanks,
> > > >>>>>>
> > > >>>>>> Jiangjie (Becket) Qin
> > > >>>>>>
> > > >>>>>>
> > > >>>>>>
> > > >>>>>> On Mon, Jun 3, 2019 at 4:14 PM Piotr Nowojski <
> > piotr@ververica.com>
> > > >>>>> wrote:
> > > >>>>>>
> > > >>>>>>> Hi again :)
> > > >>>>>>>
> > > >>>>>>>> - pending.bytes, Gauge
> > > >>>>>>>> - pending.messages, Gauge
> > > >>>>>>>
> > > >>>>>>>
> > > >>>>>>> +1
> > > >>>>>>>
> > > >>>>>>> And true, instead of overloading one of the metric it is better
> > > when
> > > >>>>> user
> > > >>>>>>> can choose to provide only one of them.
> > > >>>>>>>
> > > >>>>>>> Re 2:
> > > >>>>>>>
> > > >>>>>>>> If I understand correctly, this metric along with the pending
> > > >> mesages
> > > >>>>> /
> > > >>>>>>>> bytes would answer the questions of:
> > > >>>>>>>
> > > >>>>>>>> - Does the connector consume fast enough? Lagging behind +
> empty
> > > >>>>> buffer
> > > >>>>>>> =
> > > >>>>>>>> cannot consume fast enough.
> > > >>>>>>>> - Does the connector emit fast enough? Lagging behind + full
> > > buffer
> > > >> =
> > > >>>>>>>> cannot emit fast enough, i.e. the Flink pipeline is slow.
> > > >>>>>>>
> > > >>>>>>> Yes, exactly. This can also be used to support decisions like
> > > >> changing
> > > >>>>> the
> > > >>>>>>> parallelism of the sources and/or down stream operators.
> > > >>>>>>>
> > > >>>>>>> I’m not sure if I understand your proposal with time based
> > > >>>>> measurements.
> > > >>>>>>> Maybe I’m missing something, but I do not see how measuring
> time
> > > >> alone
> > > >>>>>>> could answer the problem: where is the bottleneck. Time spent
> on
> > > the
> > > >>>>>>> next/emit might be short or long (depending on how heavy to
> > process
> > > >> the
> > > >>>>>>> record is) and the source can still be bottlenecked/back
> > pressured
> > > or
> > > >>>>> not.
> > > >>>>>>> Usually the easiest and the most reliable way how to detect
> > > >>>>> bottlenecks is
> > > >>>>>>> by checking usage of input & output buffers, since when input
> > > buffer
> > > >> is
> > > >>>>>>> full while output buffer is empty, that’s the definition of a
> > > >>>>> bottleneck.
> > > >>>>>>> Also this is usually very easy and cheap to measure (it works
> > > >>>>> effectively
> > > >>>>>>> the same way as current’s Flink back pressure monitoring, but
> > more
> > > >>>>> cleanly,
> > > >>>>>>> without probing thread’s stack traces).
> > > >>>>>>>
> > > >>>>>>> Also keep in mind that we are already using the buffer usage
> > > metrics
> > > >>>>> for
> > > >>>>>>> detecting the bottlenecks in Flink’s internal network exchanges
> > > >> (manual
> > > >>>>>>> work). That’s the reason why I wanted to extend this to
> > > >> sources/sinks,
> > > >>>>>>> since they are currently our blind spot.
> > > >>>>>>>
> > > >>>>>>>> One feature we are currently working on to scale Flink
> > > automatically
> > > >>>>>>> relies
> > > >>>>>>>> on some metrics answering the same question
> > > >>>>>>>
> > > >>>>>>> That would be very helpful feature. I think in order to achieve
> > > that
> > > >> we
> > > >>>>>>> would need to:
> > > >>>>>>> 1. Define the metrics that would allow us to manually detect
> > > >>>>> bottlenecks.
> > > >>>>>>> As I wrote, we already have them in most of the places, except
> of
> > > >>>>>>> sources/sinks.
> > > >>>>>>> 2. Use those metrics, to automatically detect bottlenecks.
> > > Currently
> > > >> we
> > > >>>>>>> are only automatically detecting back pressure and reporting it
> > to
> > > >> the
> > > >>>>> user
> > > >>>>>>> in web UI (is it exposed as a metric at all?). Detecting the
> root
> > > >>>>> cause of
> > > >>>>>>> the back pressure (bottleneck) is one step further.
> > > >>>>>>> 3. Use the knowledge about where exactly the bottleneck is
> > located,
> > > >> to
> > > >>>>> try
> > > >>>>>>> to do something with it.
> > > >>>>>>>
> > > >>>>>>> I think you are aiming for point 3., but before we reach it, we
> > are
> > > >>>>> still
> > > >>>>>>> missing 1. & 2. Also even if we have 3., there is a value in 1
> &
> > 2
> > > >> for
> > > >>>>>>> manual analysis/dashboards.
> > > >>>>>>>
> > > >>>>>>> However, having the knowledge of where the bottleneck is,
> doesn’t
> > > >>>>>>> necessarily mean that we know what we can do about it. For
> > example
> > > >>>>>>> increasing parallelism might or might not help with anything
> > (data
> > > >>>>> skew,
> > > >>>>>>> bottleneck on some resource that does not scale), but this
> remark
> > > >>>>> applies
> > > >>>>>>> always, regardless of the way how did we detect the bottleneck.
> > > >>>>>>>
> > > >>>>>>> Piotrek
> > > >>>>>>>
> > > >>>>>>>> On 3 Jun 2019, at 06:16, Becket Qin <be...@gmail.com>
> > wrote:
> > > >>>>>>>>
> > > >>>>>>>> Hi Piotr,
> > > >>>>>>>>
> > > >>>>>>>> Thanks for the suggestion. Some thoughts below:
> > > >>>>>>>>
> > > >>>>>>>> Re 1: The pending messages / bytes.
> > > >>>>>>>> I completely agree these are very useful metrics and we should
> > > >> expect
> > > >>>>> the
> > > >>>>>>>> connector to report. WRT the way to expose them, it seems more
> > > >>>>> consistent
> > > >>>>>>>> to add two metrics instead of adding a method (unless there
> are
> > > >> other
> > > >>>>> use
> > > >>>>>>>> cases other than metric reporting). So we can add the
> following
> > > two
> > > >>>>>>> metrics.
> > > >>>>>>>> - pending.bytes, Gauge
> > > >>>>>>>> - pending.messages, Gauge
> > > >>>>>>>> Applicable connectors can choose to report them. These two
> > metrics
> > > >>>>> along
> > > >>>>>>>> with latency should be sufficient for users to understand the
> > > >> progress
> > > >>>>>>> of a
> > > >>>>>>>> connector.
> > > >>>>>>>>
> > > >>>>>>>>
> > > >>>>>>>> Re 2: Number of buffered data in-memory of the connector
> > > >>>>>>>> If I understand correctly, this metric along with the pending
> > > >> mesages
> > > >>>>> /
> > > >>>>>>>> bytes would answer the questions of:
> > > >>>>>>>> - Does the connector consume fast enough? Lagging behind +
> empty
> > > >>>>> buffer
> > > >>>>>>> =
> > > >>>>>>>> cannot consume fast enough.
> > > >>>>>>>> - Does the connector emit fast enough? Lagging behind + full
> > > buffer
> > > >> =
> > > >>>>>>>> cannot emit fast enough, i.e. the Flink pipeline is slow.
> > > >>>>>>>>
> > > >>>>>>>> One feature we are currently working on to scale Flink
> > > automatically
> > > >>>>>>> relies
> > > >>>>>>>> on some metrics answering the same question, more
> specifically,
> > we
> > > >> are
> > > >>>>>>>> profiling the time spent on .next() method (time to consume)
> and
> > > the
> > > >>>>> time
> > > >>>>>>>> spent on .collect() method (time to emit / process). One
> > advantage
> > > >> of
> > > >>>>>>> such
> > > >>>>>>>> method level time cost allows us to calculate the parallelism
> > > >>>>> required to
> > > >>>>>>>> keep up in case their is a lag.
> > > >>>>>>>>
> > > >>>>>>>> However, one concern I have regarding such metric is that they
> > are
> > > >>>>>>>> implementation specific. Either profiling on the method time,
> or
> > > >>>>>>> reporting
> > > >>>>>>>> buffer usage assumes the connector are implemented in such a
> > way.
> > > A
> > > >>>>>>>> slightly better solution might be have the following metric:
> > > >>>>>>>>
> > > >>>>>>>> - EmitTimeRatio (or FetchTimeRatio): The time spent on
> emitting
> > > >>>>>>>> records / Total time elapsed.
> > > >>>>>>>>
> > > >>>>>>>> This assumes that the source connectors have to emit the
> records
> > > to
> > > >>>>> the
> > > >>>>>>>> downstream at some point. The emission may take some time (
> e.g.
> > > go
> > > >>>>>>> through
> > > >>>>>>>> chained operators). And the rest of the time are spent to
> > prepare
> > > >> the
> > > >>>>>>>> record to emit, including time for consuming and format
> > > conversion,
> > > >>>>> etc.
> > > >>>>>>>> Ideally, we'd like to see the time spent on record fetch and
> > emit
> > > to
> > > >>>>> be
> > > >>>>>>>> about the same, so no one is bottleneck for the other.
> > > >>>>>>>>
> > > >>>>>>>> The downside of these time based metrics is additional
> overhead
> > to
> > > >> get
> > > >>>>>>> the
> > > >>>>>>>> time, therefore sampling might be needed. But in practice I
> feel
> > > >> such
> > > >>>>>>> time
> > > >>>>>>>> based metric might be more useful if we want to take action.
> > > >>>>>>>>
> > > >>>>>>>>
> > > >>>>>>>> I think we should absolutely add metrics in (1) to the metric
> > > >>>>> convention.
> > > >>>>>>>> We could also add the metrics mentioned in (2) if we reach
> > > consensus
> > > >>>>> on
> > > >>>>>>>> that. What do you think?
> > > >>>>>>>>
> > > >>>>>>>> Thanks,
> > > >>>>>>>>
> > > >>>>>>>> Jiangjie (Becket) Qin
> > > >>>>>>>>
> > > >>>>>>>>
> > > >>>>>>>> On Fri, May 31, 2019 at 4:26 PM Piotr Nowojski <
> > > piotr@ververica.com
> > > >>>
> > > >>>>>>> wrote:
> > > >>>>>>>>
> > > >>>>>>>>> Hey Becket,
> > > >>>>>>>>>
> > > >>>>>>>>> Re 1a) and 1b) +1 from my side.
> > > >>>>>>>>>
> > > >>>>>>>>> I’ve discussed this issue:
> > > >>>>>>>>>
> > > >>>>>>>>>>>>
> > > >>>>>>>>>>>> 2. It would be nice to have metrics, that allow us to
> check
> > > the
> > > >>>>> cause
> > > >>>>>>>>> of
> > > >>>>>>>>>>>> back pressure:
> > > >>>>>>>>>>>> a) for sources, length of input queue (in bytes? Or
> boolean
> > > >>>>>>>>>>>> hasSomethingl/isEmpty)
> > > >>>>>>>>>>>> b) for sinks, length of output queue (in bytes? Or boolean
> > > >>>>>>>>>>>> hasSomething/isEmpty)
> > > >>>>>>>>>
> > > >>>>>>>>> With Nico at some lengths and he also saw the benefits of
> them.
> > > We
> > > >>>>> also
> > > >>>>>>>>> have more concrete proposal for that.
> > > >>>>>>>>>
> > > >>>>>>>>> Actually there are two really useful metrics, that we are
> > missing
> > > >>>>>>>>> currently:
> > > >>>>>>>>>
> > > >>>>>>>>> 1. Number of data/records/bytes in the backlog to process.
> For
> > > >>>>> example
> > > >>>>>>>>> remaining number of bytes in unread files. Or pending data in
> > > Kafka
> > > >>>>>>> topics.
> > > >>>>>>>>> 2. Number of buffered data in-memory of the connector, that
> are
> > > >>>>> waiting
> > > >>>>>>> to
> > > >>>>>>>>> be processed pushed to Flink pipeline.
> > > >>>>>>>>>
> > > >>>>>>>>> Re 1:
> > > >>>>>>>>> This would have to be a metric provided directly by a
> > connector.
> > > It
> > > >>>>>>> could
> > > >>>>>>>>> be an undefined `int`:
> > > >>>>>>>>>
> > > >>>>>>>>> `int backlog` - estimate of pending work.
> > > >>>>>>>>>
> > > >>>>>>>>> “Undefined” meaning that it would be up to a connector to
> > decided
> > > >>>>>>> whether
> > > >>>>>>>>> it’s measured in bytes, records, pending files or whatever it
> > is
> > > >>>>>>> possible
> > > >>>>>>>>> to provide by the connector. This is because I assume not
> every
> > > >>>>>>> connector
> > > >>>>>>>>> can provide exact number and for some of them it might be
> > > >> impossible
> > > >>>>> to
> > > >>>>>>>>> provide records number of bytes count.
> > > >>>>>>>>>
> > > >>>>>>>>> Re 2:
> > > >>>>>>>>> This metric could be either provided by a connector, or
> > > calculated
> > > >>>>>>> crudely
> > > >>>>>>>>> by Flink:
> > > >>>>>>>>>
> > > >>>>>>>>> `float bufferUsage` - value from [0.0, 1.0] range
> > > >>>>>>>>>
> > > >>>>>>>>> Percentage of used in memory buffers, like in Kafka’s
> handover.
> > > >>>>>>>>>
> > > >>>>>>>>> It could be crudely implemented by Flink with FLIP-27
> > > >>>>>>>>> SourceReader#isAvailable. If SourceReader is not available
> > > reported
> > > >>>>>>>>> `bufferUsage` could be 0.0. If it is available, it could be
> > 1.0.
> > > I
> > > >>>>> think
> > > >>>>>>>>> this would be a good enough estimation for most of the use
> > cases
> > > >>>>> (that
> > > >>>>>>>>> could be overloaded and implemented better if desired).
> > > Especially
> > > >>>>>>> since we
> > > >>>>>>>>> are reporting only probed values: if probed values are almost
> > > >> always
> > > >>>>>>> “1.0”,
> > > >>>>>>>>> it would mean that we have a back pressure. If they are
> almost
> > > >> always
> > > >>>>>>>>> “0.0”, there is probably no back pressure at the sources.
> > > >>>>>>>>>
> > > >>>>>>>>> What do you think about this?
> > > >>>>>>>>>
> > > >>>>>>>>> Piotrek
> > > >>>>>>>>>
> > > >>>>>>>>>> On 30 May 2019, at 11:41, Becket Qin <be...@gmail.com>
> > > >> wrote:
> > > >>>>>>>>>>
> > > >>>>>>>>>> Hi all,
> > > >>>>>>>>>>
> > > >>>>>>>>>> Thanks a lot for all the feedback and comments. I'd like to
> > > >> continue
> > > >>>>>>> the
> > > >>>>>>>>>> discussion on this FLIP.
> > > >>>>>>>>>>
> > > >>>>>>>>>> I updated the FLIP-33 wiki to remove all the histogram
> metrics
> > > >> from
> > > >>>>> the
> > > >>>>>>>>>> first version of metric convention due to the performance
> > > concern.
> > > >>>>> The
> > > >>>>>>>>> plan
> > > >>>>>>>>>> is to introduce them later when we have a mechanism to opt
> > > in/out
> > > >>>>>>>>> metrics.
> > > >>>>>>>>>> At that point, users can decide whether they want to pay the
> > > cost
> > > >> to
> > > >>>>>>> get
> > > >>>>>>>>>> the metric or not.
> > > >>>>>>>>>>
> > > >>>>>>>>>> As Stephan suggested, for this FLIP, let's first try to
> agree
> > on
> > > >> the
> > > >>>>>>>>> small
> > > >>>>>>>>>> list of conventional metrics that connectors should follow.
> > > >>>>>>>>>> Just to be clear, the purpose of the convention is not to
> > > enforce
> > > >>>>> every
> > > >>>>>>>>>> connector to report all these metrics, but to provide a
> > guidance
> > > >> in
> > > >>>>>>> case
> > > >>>>>>>>>> these metrics are reported by some connectors.
> > > >>>>>>>>>>
> > > >>>>>>>>>>
> > > >>>>>>>>>> @ Stephan & Chesnay,
> > > >>>>>>>>>>
> > > >>>>>>>>>> Regarding the duplication of `RecordsIn` metric in operator
> /
> > > task
> > > >>>>>>>>>> IOMetricGroups, from what I understand, for source operator,
> > it
> > > is
> > > >>>>>>>>> actually
> > > >>>>>>>>>> the SourceFunction that reports the operator level
> > > >>>>>>>>>> RecordsIn/RecordsInPerSecond metric. So they are essentially
> > the
> > > >>>>> same
> > > >>>>>>>>>> metric in the operator level IOMetricGroup. Similarly for
> the
> > > Sink
> > > >>>>>>>>>> operator, the operator level RecordsOut/RecordsOutPerSecond
> > > >> metrics
> > > >>>>> are
> > > >>>>>>>>>> also reported by the Sink function. I marked them as
> existing
> > in
> > > >> the
> > > >>>>>>>>>> FLIP-33 wiki page. Please let me know if I misunderstood.
> > > >>>>>>>>>>
> > > >>>>>>>>>> Thanks,
> > > >>>>>>>>>>
> > > >>>>>>>>>> Jiangjie (Becket) Qin
> > > >>>>>>>>>>
> > > >>>>>>>>>>
> > > >>>>>>>>>> On Thu, May 30, 2019 at 5:16 PM Becket Qin <
> > > becket.qin@gmail.com>
> > > >>>>>>> wrote:
> > > >>>>>>>>>>
> > > >>>>>>>>>>> Hi Piotr,
> > > >>>>>>>>>>>
> > > >>>>>>>>>>> Thanks a lot for the feedback.
> > > >>>>>>>>>>>
> > > >>>>>>>>>>> 1a) I guess you are referring to the part that "original
> > system
> > > >>>>>>> specific
> > > >>>>>>>>>>> metrics should also be reported". The performance impact
> > > depends
> > > >> on
> > > >>>>>>> the
> > > >>>>>>>>>>> implementation. An efficient implementation would only
> record
> > > the
> > > >>>>>>> metric
> > > >>>>>>>>>>> once, but report them with two different metric names. This
> > is
> > > >>>>>>> unlikely
> > > >>>>>>>>> to
> > > >>>>>>>>>>> hurt performance.
> > > >>>>>>>>>>>
> > > >>>>>>>>>>> 1b) Yes, I agree that we should avoid adding overhead to
> the
> > > >>>>> critical
> > > >>>>>>>>> path
> > > >>>>>>>>>>> by all means. This is sometimes a tradeoff, running blindly
> > > >> without
> > > >>>>>>> any
> > > >>>>>>>>>>> metric gives best performance, but sometimes might be
> > > frustrating
> > > >>>>> when
> > > >>>>>>>>> we
> > > >>>>>>>>>>> debug some issues.
> > > >>>>>>>>>>>
> > > >>>>>>>>>>> 2. The metrics are indeed very useful. Are they supposed to
> > be
> > > >>>>>>> reported
> > > >>>>>>>>> by
> > > >>>>>>>>>>> the connectors or Flink itself? At this point FLIP-33 is
> more
> > > >>>>> focused
> > > >>>>>>> on
> > > >>>>>>>>>>> provide a guidance to the connector authors on the metrics
> > > >>>>> reporting.
> > > >>>>>>>>> That
> > > >>>>>>>>>>> said, after FLIP-27, I think we should absolutely report
> > these
> > > >>>>> metrics
> > > >>>>>>>>> in
> > > >>>>>>>>>>> the abstract implementation. In any case, the metric
> > convention
> > > >> in
> > > >>>>>>> this
> > > >>>>>>>>>>> list are expected to evolve over time.
> > > >>>>>>>>>>>
> > > >>>>>>>>>>> Thanks,
> > > >>>>>>>>>>>
> > > >>>>>>>>>>> Jiangjie (Becket) Qin
> > > >>>>>>>>>>>
> > > >>>>>>>>>>> On Tue, May 28, 2019 at 6:24 PM Piotr Nowojski <
> > > >>>>> piotr@ververica.com>
> > > >>>>>>>>>>> wrote:
> > > >>>>>>>>>>>
> > > >>>>>>>>>>>> Hi,
> > > >>>>>>>>>>>>
> > > >>>>>>>>>>>> Thanks for the proposal and driving the effort here Becket
> > :)
> > > >> I’ve
> > > >>>>>>> read
> > > >>>>>>>>>>>> through the FLIP-33 [1], and here are couple of my
> thoughts.
> > > >>>>>>>>>>>>
> > > >>>>>>>>>>>> Big +1 for standardising the metric names between
> > connectors,
> > > it
> > > >>>>> will
> > > >>>>>>>>>>>> definitely help us and users a lot.
> > > >>>>>>>>>>>>
> > > >>>>>>>>>>>> Issues/questions/things to discuss that I’ve thought of:
> > > >>>>>>>>>>>>
> > > >>>>>>>>>>>> 1a. If we are about to duplicate some metrics, can this
> > > become a
> > > >>>>>>>>>>>> performance issue?
> > > >>>>>>>>>>>> 1b. Generally speaking, we should make sure that
> collecting
> > > >> those
> > > >>>>>>>>> metrics
> > > >>>>>>>>>>>> is as non intrusive as possible, especially that they will
> > > need
> > > >>>>> to be
> > > >>>>>>>>>>>> updated once per record. (They might be collected more
> > rarely
> > > >> with
> > > >>>>>>> some
> > > >>>>>>>>>>>> overhead, but the hot path of updating it per record will
> > need
> > > >> to
> > > >>>>> be
> > > >>>>>>> as
> > > >>>>>>>>>>>> quick as possible). That includes both avoiding heavy
> > > >> computation
> > > >>>>> on
> > > >>>>>>>>> per
> > > >>>>>>>>>>>> record path: histograms?, measuring time for time based
> > > metrics
> > > >>>>> (per
> > > >>>>>>>>>>>> second) (System.currentTimeMillis() depending on the
> > > >>>>> implementation
> > > >>>>>>> can
> > > >>>>>>>>>>>> invoke a system call)
> > > >>>>>>>>>>>>
> > > >>>>>>>>>>>> 2. It would be nice to have metrics, that allow us to
> check
> > > the
> > > >>>>> cause
> > > >>>>>>>>> of
> > > >>>>>>>>>>>> back pressure:
> > > >>>>>>>>>>>> a) for sources, length of input queue (in bytes? Or
> boolean
> > > >>>>>>>>>>>> hasSomethingl/isEmpty)
> > > >>>>>>>>>>>> b) for sinks, length of output queue (in bytes? Or boolean
> > > >>>>>>>>>>>> hasSomething/isEmpty)
> > > >>>>>>>>>>>>
> > > >>>>>>>>>>>> a) is useful in a scenario when we are processing backlog
> of
> > > >>>>> records,
> > > >>>>>>>>> all
> > > >>>>>>>>>>>> of the internal Flink’s input/output network buffers are
> > > empty,
> > > >>>>> and
> > > >>>>>>> we
> > > >>>>>>>>> want
> > > >>>>>>>>>>>> to check whether the external source system is the
> > bottleneck
> > > >>>>>>> (source’s
> > > >>>>>>>>>>>> input queue will be empty), or if the Flink’s connector is
> > the
> > > >>>>>>>>> bottleneck
> > > >>>>>>>>>>>> (source’s input queues will be full).
> > > >>>>>>>>>>>> b) similar story. Backlog of records, but this time all of
> > the
> > > >>>>>>> internal
> > > >>>>>>>>>>>> Flink’s input/ouput network buffers are full, and we want
> o
> > > >> check
> > > >>>>>>>>> whether
> > > >>>>>>>>>>>> the external sink system is the bottleneck (sink output
> > queues
> > > >> are
> > > >>>>>>>>> full),
> > > >>>>>>>>>>>> or if the Flink’s connector is the bottleneck (sink’s
> output
> > > >>>>> queues
> > > >>>>>>>>> will be
> > > >>>>>>>>>>>> empty)
> > > >>>>>>>>>>>>
> > > >>>>>>>>>>>> It might be sometimes difficult to provide those metrics,
> so
> > > >> they
> > > >>>>>>> could
> > > >>>>>>>>>>>> be optional, but if we could provide them, it would be
> > really
> > > >>>>>>> helpful.
> > > >>>>>>>>>>>>
> > > >>>>>>>>>>>> Piotrek
> > > >>>>>>>>>>>>
> > > >>>>>>>>>>>> [1]
> > > >>>>>>>>>>>>
> > > >>>>>>>>>
> > > >>>>>>>
> > > >>>>>
> > > >>
> > >
> >
> https://cwiki.apache.org/confluence/display/FLINK/FLIP-33:+Standardize+Connector+Metrics
> > > >>>>>>>>>>>> <
> > > >>>>>>>>>>>>
> > > >>>>>>>>>
> > > >>>>>>>
> > > >>>>>
> > > >>
> > >
> >
> https://cwiki.apache.org/confluence/display/FLINK/FLIP-33:+Standardize+Connector+Metrics
> > > >>>>>>>>>>>>>
> > > >>>>>>>>>>>>
> > > >>>>>>>>>>>>> On 24 Apr 2019, at 13:28, Stephan Ewen <sewen@apache.org
> >
> > > >> wrote:
> > > >>>>>>>>>>>>>
> > > >>>>>>>>>>>>> I think this sounds reasonable.
> > > >>>>>>>>>>>>>
> > > >>>>>>>>>>>>> Let's keep the "reconfiguration without stopping the job"
> > out
> > > >> of
> > > >>>>>>> this,
> > > >>>>>>>>>>>>> because that would be a super big effort and if we
> approach
> > > >> that,
> > > >>>>>>> then
> > > >>>>>>>>>>>> in
> > > >>>>>>>>>>>>> more generic way rather than specific to connector
> metrics.
> > > >>>>>>>>>>>>>
> > > >>>>>>>>>>>>> I would suggest to look at the following things before
> > > starting
> > > >>>>> with
> > > >>>>>>>>> any
> > > >>>>>>>>>>>>> implementation work:
> > > >>>>>>>>>>>>>
> > > >>>>>>>>>>>>> - Try and find a committer to support this, otherwise it
> > will
> > > >> be
> > > >>>>>>> hard
> > > >>>>>>>>>>>> to
> > > >>>>>>>>>>>>> make progress
> > > >>>>>>>>>>>>> - Start with defining a smaller set of "core metrics" and
> > > >> extend
> > > >>>>> the
> > > >>>>>>>>>>>> set
> > > >>>>>>>>>>>>> later. I think that is easier than now blocking on
> reaching
> > > >>>>>>> consensus
> > > >>>>>>>>>>>> on a
> > > >>>>>>>>>>>>> large group of metrics.
> > > >>>>>>>>>>>>> - Find a solution to the problem Chesnay mentioned, that
> > the
> > > >>>>>>> "records
> > > >>>>>>>>>>>> in"
> > > >>>>>>>>>>>>> metric is somehow overloaded and exists already in the IO
> > > >> Metric
> > > >>>>>>>>> group.
> > > >>>>>>>>>>>>>
> > > >>>>>>>>>>>>>
> > > >>>>>>>>>>>>> On Mon, Mar 25, 2019 at 7:16 AM Becket Qin <
> > > >> becket.qin@gmail.com
> > > >>>>>>
> > > >>>>>>>>>>>> wrote:
> > > >>>>>>>>>>>>>
> > > >>>>>>>>>>>>>> Hi Stephan,
> > > >>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>> Thanks a lot for the feedback. All makes sense.
> > > >>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>> It is a good suggestion to simply have an
> > onRecord(numBytes,
> > > >>>>>>>>> eventTime)
> > > >>>>>>>>>>>>>> method for connector writers. It should meet most of the
> > > >>>>>>>>> requirements,
> > > >>>>>>>>>>>>>> individual
> > > >>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>> The configurable metrics feature is something really
> > useful,
> > > >>>>>>>>>>>> especially if
> > > >>>>>>>>>>>>>> we can somehow make it dynamically configurable without
> > > >> stopping
> > > >>>>>>> the
> > > >>>>>>>>>>>> jobs.
> > > >>>>>>>>>>>>>> It might be better to make it a separate discussion
> > because
> > > it
> > > >>>>> is a
> > > >>>>>>>>>>>> more
> > > >>>>>>>>>>>>>> generic feature instead of only for connectors.
> > > >>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>> So in order to make some progress, in this FLIP we can
> > limit
> > > >> the
> > > >>>>>>>>>>>> discussion
> > > >>>>>>>>>>>>>> scope to the connector related items:
> > > >>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>> - the standard connector metric names and types.
> > > >>>>>>>>>>>>>> - the abstract ConnectorMetricHandler interface
> > > >>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>> I'll start a separate thread to discuss other general
> > metric
> > > >>>>>>> related
> > > >>>>>>>>>>>>>> enhancement items including:
> > > >>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>> - optional metrics
> > > >>>>>>>>>>>>>> - dynamic metric configuration
> > > >>>>>>>>>>>>>> - potential combination with rate limiter
> > > >>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>> Does this plan sound reasonable?
> > > >>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>> Thanks,
> > > >>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>> Jiangjie (Becket) Qin
> > > >>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>> On Sat, Mar 23, 2019 at 5:53 AM Stephan Ewen <
> > > >> sewen@apache.org>
> > > >>>>>>>>> wrote:
> > > >>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>> Ignoring for a moment implementation details, this
> > > connector
> > > >>>>>>> metrics
> > > >>>>>>>>>>>> work
> > > >>>>>>>>>>>>>>> is a really good thing to do, in my opinion
> > > >>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>> The questions "oh, my job seems to be doing nothing, I
> am
> > > >>>>> looking
> > > >>>>>>> at
> > > >>>>>>>>>>>> the
> > > >>>>>>>>>>>>>> UI
> > > >>>>>>>>>>>>>>> and the 'records in' value is still zero" is in the top
> > > three
> > > >>>>>>>>> support
> > > >>>>>>>>>>>>>>> questions I have been asked personally.
> > > >>>>>>>>>>>>>>> Introspection into "how far is the consumer lagging
> > behind"
> > > >>>>> (event
> > > >>>>>>>>>>>> time
> > > >>>>>>>>>>>>>>> fetch latency) came up many times as well.
> > > >>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>> So big +1 to solving this problem.
> > > >>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>> About the exact design - I would try to go for the
> > > following
> > > >>>>>>>>>>>> properties:
> > > >>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>> - keep complexity of of connectors. Ideally the metrics
> > > >> handler
> > > >>>>>>> has
> > > >>>>>>>>> a
> > > >>>>>>>>>>>>>>> single onRecord(numBytes, eventTime) method or so, and
> > > >>>>> everything
> > > >>>>>>>>>>>> else is
> > > >>>>>>>>>>>>>>> internal to the handler. That makes it dead simple for
> > the
> > > >>>>>>>>> connector.
> > > >>>>>>>>>>>> We
> > > >>>>>>>>>>>>>>> can also think of an extensive scheme for connector
> > > specific
> > > >>>>>>>>> metrics.
> > > >>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>> - make it configurable on the job it cluster level
> which
> > > >>>>> metrics
> > > >>>>>>> the
> > > >>>>>>>>>>>>>>> handler internally creates when that method is invoked.
> > > >>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>> What do you think?
> > > >>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>> Best,
> > > >>>>>>>>>>>>>>> Stephan
> > > >>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>> On Thu, Mar 21, 2019 at 10:42 AM Chesnay Schepler <
> > > >>>>>>>>> chesnay@apache.org
> > > >>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>> wrote:
> > > >>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>> As I said before, I believe this to be over-engineered
> > and
> > > >>>>> have
> > > >>>>>>> no
> > > >>>>>>>>>>>>>>>> interest in this implementation.
> > > >>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>> There are conceptual issues like defining a duplicate
> > > >>>>>>>>>>>>>> numBytesIn(PerSec)
> > > >>>>>>>>>>>>>>>> metric that already exists for each operator.
> > > >>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>> On 21.03.2019 06:13, Becket Qin wrote:
> > > >>>>>>>>>>>>>>>>> A few updates to the thread. I uploaded a patch[1]
> as a
> > > >>>>> complete
> > > >>>>>>>>>>>>>>>>> example of how users can use the metrics in the
> future.
> > > >>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>> Some thoughts below after taking a look at the
> > > >>>>>>> AbstractMetricGroup
> > > >>>>>>>>>>>>>> and
> > > >>>>>>>>>>>>>>>>> its subclasses.
> > > >>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>> This patch intends to provide convenience for Flink
> > > >> connector
> > > >>>>>>>>>>>>>>>>> implementations to follow metrics standards proposed
> in
> > > >>>>> FLIP-33.
> > > >>>>>>>>> It
> > > >>>>>>>>>>>>>>>>> also try to enhance the metric management in general
> > way
> > > to
> > > >>>>> help
> > > >>>>>>>>>>>>>> users
> > > >>>>>>>>>>>>>>>>> with:
> > > >>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>> 1. metric definition
> > > >>>>>>>>>>>>>>>>> 2. metric dependencies check
> > > >>>>>>>>>>>>>>>>> 3. metric validation
> > > >>>>>>>>>>>>>>>>> 4. metric control (turn on / off particular metrics)
> > > >>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>> This patch wraps |MetricGroup| to extend the
> > > functionality
> > > >> of
> > > >>>>>>>>>>>>>>>>> |AbstractMetricGroup| and its subclasses. The
> > > >>>>>>>>>>>>>>>>> |AbstractMetricGroup| mainly focus on the metric
> group
> > > >>>>>>> hierarchy,
> > > >>>>>>>>>>>> but
> > > >>>>>>>>>>>>>>>>> does not really manage the metrics other than keeping
> > > them
> > > >>>>> in a
> > > >>>>>>>>> Map.
> > > >>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>> Ideally we should only have one entry point for the
> > > >> metrics.
> > > >>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>> Right now the entry point is |AbstractMetricGroup|.
> > > >> However,
> > > >>>>>>>>> besides
> > > >>>>>>>>>>>>>>>>> the missing functionality mentioned above,
> > > >>>>> |AbstractMetricGroup|
> > > >>>>>>>>>>>>>> seems
> > > >>>>>>>>>>>>>>>>> deeply rooted in Flink runtime. We could extract it
> out
> > > to
> > > >>>>>>>>>>>>>>>>> flink-metrics in order to use it for generic purpose.
> > > There
> > > >>>>> will
> > > >>>>>>>>> be
> > > >>>>>>>>>>>>>>>>> some work, though.
> > > >>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>> Another approach is to make |AbstractMetrics| in this
> > > patch
> > > >>>>> as
> > > >>>>>>> the
> > > >>>>>>>>>>>>>>>>> metric entry point. It wraps metric group and
> provides
> > > the
> > > >>>>>>> missing
> > > >>>>>>>>>>>>>>>>> functionalities. Then we can roll out this pattern to
> > > >> runtime
> > > >>>>>>>>>>>>>>>>> components gradually as well.
> > > >>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>> My first thought is that the latter approach gives a
> > more
> > > >>>>> smooth
> > > >>>>>>>>>>>>>>>>> migration. But I am also OK with doing a refactoring
> on
> > > the
> > > >>>>>>>>>>>>>>>>> |AbstractMetricGroup| family.
> > > >>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>> Thanks,
> > > >>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>> Jiangjie (Becket) Qin
> > > >>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>> [1] https://github.com/becketqin/flink/pull/1
> > > >>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>> On Mon, Feb 25, 2019 at 2:32 PM Becket Qin <
> > > >>>>>>> becket.qin@gmail.com
> > > >>>>>>>>>>>>>>>>> <ma...@gmail.com>> wrote:
> > > >>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>> Hi Chesnay,
> > > >>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>> It might be easier to discuss some implementation
> > details
> > > >> in
> > > >>>>>>> the
> > > >>>>>>>>>>>>>>>>> PR review instead of in the FLIP discussion thread. I
> > > have
> > > >> a
> > > >>>>>>>>>>>>>> patch
> > > >>>>>>>>>>>>>>>>> for Kafka connectors ready but haven't submitted the
> PR
> > > >> yet.
> > > >>>>>>>>>>>>>>>>> Hopefully that will help explain a bit more.
> > > >>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>> ** Re: metric type binding
> > > >>>>>>>>>>>>>>>>> This is a valid point that worths discussing. If I
> > > >> understand
> > > >>>>>>>>>>>>>>>>> correctly, there are two points:
> > > >>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>> 1. Metric type / interface does not matter as long as
> > the
> > > >>>>>>> metric
> > > >>>>>>>>>>>>>>>>> semantic is clearly defined.
> > > >>>>>>>>>>>>>>>>> Conceptually speaking, I agree that as long as the
> > metric
> > > >>>>>>>>>>>>>> semantic
> > > >>>>>>>>>>>>>>>>> is defined, metric type does not matter. To some
> > extent,
> > > >>>>> Gauge
> > > >>>>>>> /
> > > >>>>>>>>>>>>>>>>> Counter / Meter / Histogram themselves can be think
> of
> > as
> > > >>>>> some
> > > >>>>>>>>>>>>>>>>> well-recognized semantics, if you wish. In Flink,
> these
> > > >>>>> metric
> > > >>>>>>>>>>>>>>>>> semantics have their associated interface classes. In
> > > >>>>> practice,
> > > >>>>>>>>>>>>>>>>> such semantic to interface binding seems necessary
> for
> > > >>>>>>> different
> > > >>>>>>>>>>>>>>>>> components to communicate. Simply standardize the
> > > semantic
> > > >>>>> of
> > > >>>>>>>>>>>>>> the
> > > >>>>>>>>>>>>>>>>> connector metrics seems not sufficient for people to
> > > build
> > > >>>>>>>>>>>>>>>>> ecosystem on top of. At the end of the day, we still
> > need
> > > >> to
> > > >>>>>>>>> have
> > > >>>>>>>>>>>>>>>>> some embodiment of the metric semantics that people
> can
> > > >>>>> program
> > > >>>>>>>>>>>>>>>>> against.
> > > >>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>> 2. Sometimes the same metric semantic can be exposed
> > > using
> > > >>>>>>>>>>>>>>>>> different metric types / interfaces.
> > > >>>>>>>>>>>>>>>>> This is a good point. Counter and Gauge-as-a-Counter
> > are
> > > >>>>> pretty
> > > >>>>>>>>>>>>>>>>> much interchangeable. This is more of a trade-off
> > between
> > > >> the
> > > >>>>>>>>>>>>>> user
> > > >>>>>>>>>>>>>>>>> experience of metric producers and consumers. The
> > metric
> > > >>>>>>>>>>>>>> producers
> > > >>>>>>>>>>>>>>>>> want to use Counter or Gauge depending on whether the
> > > >> counter
> > > >>>>>>> is
> > > >>>>>>>>>>>>>>>>> already tracked in code, while ideally the metric
> > > consumers
> > > >>>>>>> only
> > > >>>>>>>>>>>>>>>>> want to see a single metric type for each metric. I
> am
> > > >>>>> leaning
> > > >>>>>>>>>>>>>>>>> towards to make the metric producers happy, i.e.
> allow
> > > >> Gauge
> > > >>>>> /
> > > >>>>>>>>>>>>>>>>> Counter metric type, and the the metric consumers
> > handle
> > > >> the
> > > >>>>>>>>> type
> > > >>>>>>>>>>>>>>>>> variation. The reason is that in practice, there
> might
> > be
> > > >>>>> more
> > > >>>>>>>>>>>>>>>>> connector implementations than metric reporter
> > > >>>>> implementations.
> > > >>>>>>>>>>>>>> We
> > > >>>>>>>>>>>>>>>>> could also provide some helper method to facilitate
> > > reading
> > > >>>>>>> from
> > > >>>>>>>>>>>>>>>>> such variable metric type.
> > > >>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>> Just some quick replies to the comments around
> > > >> implementation
> > > >>>>>>>>>>>>>>>> details.
> > > >>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>> 4) single place where metrics are registered except
> > > >>>>>>>>>>>>>>>>> connector-specific
> > > >>>>>>>>>>>>>>>>> ones (which we can't really avoid).
> > > >>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>> Register connector specific ones in a single place is
> > > >>>>> actually
> > > >>>>>>>>>>>>>>>>> something that I want to achieve.
> > > >>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>> 2) I'm talking about time-series databases like
> > > >>>>> Prometheus.
> > > >>>>>>>>>>>>>> We
> > > >>>>>>>>>>>>>>>>> would
> > > >>>>>>>>>>>>>>>>> only have a gauge metric exposing the last
> > > >>>>>>>>> fetchTime/emitTime
> > > >>>>>>>>>>>>>>>>> that is
> > > >>>>>>>>>>>>>>>>> regularly reported to the backend (Prometheus),
> > where a
> > > >>>>>>> user
> > > >>>>>>>>>>>>>>>>> could build
> > > >>>>>>>>>>>>>>>>> a histogram of his choosing when/if he wants it.
> > > >>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>> Not sure if such downsampling works. As an example,
> if
> > a
> > > >> user
> > > >>>>>>>>>>>>>>>>> complains that there are some intermittent latency
> > spikes
> > > >>>>>>> (maybe
> > > >>>>>>>>>>>>>> a
> > > >>>>>>>>>>>>>>>>> few records in 10 seconds) in their processing
> system.
> > > >>>>> Having a
> > > >>>>>>>>>>>>>>>>> Gauge sampling instantaneous latency seems unlikely
> > > useful.
> > > >>>>>>>>>>>>>>>>> However by looking at actual 99.9 percentile latency
> > > might
> > > >>>>>>> help.
> > > >>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>> Thanks,
> > > >>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>> Jiangjie (Becket) Qin
> > > >>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>> On Fri, Feb 22, 2019 at 9:30 PM Chesnay Schepler
> > > >>>>>>>>>>>>>>>>> <chesnay@apache.org <ma...@apache.org>>
> > wrote:
> > > >>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>> Re: over complication of implementation.
> > > >>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>> I think I get understand better know what you're
> > > >> shooting
> > > >>>>>>>>>>>>>> for,
> > > >>>>>>>>>>>>>>>>> effectively something like the
> OperatorIOMetricGroup.
> > > >>>>>>>>>>>>>>>>> But still, re-define setupConnectorMetrics() to
> > accept
> > > a
> > > >>>>>>> set
> > > >>>>>>>>>>>>>>>>> of flags
> > > >>>>>>>>>>>>>>>>> for counters/meters(ans _possibly_ histograms)
> along
> > > >>>>> with a
> > > >>>>>>>>>>>>>>>>> set of
> > > >>>>>>>>>>>>>>>>> well-defined Optional<Gauge<?>>, and return the
> > group.
> > > >>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>> Solves all issues as far as i can tell:
> > > >>>>>>>>>>>>>>>>> 1) no metrics must be created manually (except
> > Gauges,
> > > >>>>>>> which
> > > >>>>>>>>>>>>>>> are
> > > >>>>>>>>>>>>>>>>> effectively just Suppliers and you can't get around
> > > >>>>> this),
> > > >>>>>>>>>>>>>>>>> 2) additional metrics can be registered on the
> > returned
> > > >>>>>>>>>>>>>> group,
> > > >>>>>>>>>>>>>>>>> 3) see 1),
> > > >>>>>>>>>>>>>>>>> 4) single place where metrics are registered except
> > > >>>>>>>>>>>>>>>>> connector-specific
> > > >>>>>>>>>>>>>>>>> ones (which we can't really avoid).
> > > >>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>> Re: Histogram
> > > >>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>> 1) As an example, whether "numRecordsIn" is exposed
> > as
> > > a
> > > >>>>>>>>>>>>>>>>> Counter or a
> > > >>>>>>>>>>>>>>>>> Gauge should be irrelevant. So far we're using the
> > > >> metric
> > > >>>>>>>>>>>>>> type
> > > >>>>>>>>>>>>>>>>> that is
> > > >>>>>>>>>>>>>>>>> the most convenient at exposing a given value. If
> > there
> > > >>>>> is
> > > >>>>>>>>>>>>>>>>> some backing
> > > >>>>>>>>>>>>>>>>> data-structure that we want to expose some data
> from
> > we
> > > >>>>>>>>>>>>>>>>> typically opt
> > > >>>>>>>>>>>>>>>>> for a Gauge, as otherwise we're just mucking around
> > > with
> > > >>>>>>> the
> > > >>>>>>>>>>>>>>>>> Meter/Counter API to get it to match. Similarly, if
> > we
> > > >>>>> want
> > > >>>>>>>>>>>>>> to
> > > >>>>>>>>>>>>>>>>> count
> > > >>>>>>>>>>>>>>>>> something but no current count exists we typically
> > > added
> > > >>>>> a
> > > >>>>>>>>>>>>>>>>> Counter.
> > > >>>>>>>>>>>>>>>>> That's why attaching semantics to metric types
> makes
> > > >>>>> little
> > > >>>>>>>>>>>>>>>>> sense (but
> > > >>>>>>>>>>>>>>>>> unfortunately several reporters already do it); for
> > > >>>>>>>>>>>>>>>>> counters/meters
> > > >>>>>>>>>>>>>>>>> certainly, but the majority of metrics are gauges.
> > > >>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>> 2) I'm talking about time-series databases like
> > > >>>>> Prometheus.
> > > >>>>>>>>>>>>>> We
> > > >>>>>>>>>>>>>>>>> would
> > > >>>>>>>>>>>>>>>>> only have a gauge metric exposing the last
> > > >>>>>>>>> fetchTime/emitTime
> > > >>>>>>>>>>>>>>>>> that is
> > > >>>>>>>>>>>>>>>>> regularly reported to the backend (Prometheus),
> > where a
> > > >>>>>>> user
> > > >>>>>>>>>>>>>>>>> could build
> > > >>>>>>>>>>>>>>>>> a histogram of his choosing when/if he wants it.
> > > >>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>> On 22.02.2019 13:57, Becket Qin wrote:
> > > >>>>>>>>>>>>>>>>>> Hi Chesnay,
> > > >>>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>>> Thanks for the explanation.
> > > >>>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>>> ** Re: FLIP
> > > >>>>>>>>>>>>>>>>>> I might have misunderstood this, but it seems that
> > > "major
> > > >>>>>>>>>>>>>>>>> changes" are well
> > > >>>>>>>>>>>>>>>>>> defined in FLIP. The full contents is following:
> > > >>>>>>>>>>>>>>>>>> What is considered a "major change" that needs a
> FLIP?
> > > >>>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>>> Any of the following should be considered a major
> > > change:
> > > >>>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>>> - Any major new feature, subsystem, or piece of
> > > >>>>>>>>>>>>>>>>> functionality
> > > >>>>>>>>>>>>>>>>>> - *Any change that impacts the public interfaces of
> > the
> > > >>>>>>>>>>>>>>>>> project*
> > > >>>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>>> What are the "public interfaces" of the project?
> > > >>>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>>> *All of the following are public interfaces *that
> > people
> > > >>>>>>>>>>>>>>>>> build around:
> > > >>>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>>> - DataStream and DataSet API, including classes
> > related
> > > >>>>>>>>>>>>>>>>> to that, such as
> > > >>>>>>>>>>>>>>>>>> StreamExecutionEnvironment
> > > >>>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>>> - Classes marked with the @Public annotation
> > > >>>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>>> - On-disk binary formats, such as
> > > >>>>>>>>>>>>>> checkpoints/savepoints
> > > >>>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>>> - User-facing scripts/command-line tools, i.e.
> > > >>>>>>>>>>>>>>>>> bin/flink, Yarn scripts,
> > > >>>>>>>>>>>>>>>>>> Mesos scripts
> > > >>>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>>> - Configuration settings
> > > >>>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>>> - *Exposed monitoring information*
> > > >>>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>>> So any monitoring information change is considered
> as
> > > >>>>>>>>>>>>>> public
> > > >>>>>>>>>>>>>>>>> interface, and
> > > >>>>>>>>>>>>>>>>>> any public interface change is considered as a
> "major
> > > >>>>>>>>>>>>>>> change".
> > > >>>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>>> ** Re: over complication of implementation.
> > > >>>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>>> Although this is more of implementation details that
> > is
> > > >> not
> > > >>>>>>>>>>>>>>>>> covered by the
> > > >>>>>>>>>>>>>>>>>> FLIP. But it may be worth discussing.
> > > >>>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>>> First of all, I completely agree that we should use
> > the
> > > >>>>>>>>>>>>>>>>> simplest way to
> > > >>>>>>>>>>>>>>>>>> achieve our goal. To me the goal is the following:
> > > >>>>>>>>>>>>>>>>>> 1. Clear connector conventions and interfaces.
> > > >>>>>>>>>>>>>>>>>> 2. The easiness of creating a connector.
> > > >>>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>>> Both of them are important to the prosperity of the
> > > >>>>>>>>>>>>>>>>> connector ecosystem. So
> > > >>>>>>>>>>>>>>>>>> I'd rather abstract as much as possible on our side
> to
> > > >> make
> > > >>>>>>>>>>>>>>>>> the connector
> > > >>>>>>>>>>>>>>>>>> developer's work lighter. Given this goal, a static
> > util
> > > >>>>>>>>>>>>>>>>> method approach
> > > >>>>>>>>>>>>>>>>>> might have a few drawbacks:
> > > >>>>>>>>>>>>>>>>>> 1. Users still have to construct the metrics by
> > > >> themselves.
> > > >>>>>>>>>>>>>>>>> (And note that
> > > >>>>>>>>>>>>>>>>>> this might be erroneous by itself. For example, a
> > > customer
> > > >>>>>>>>>>>>>>>>> wrapper around
> > > >>>>>>>>>>>>>>>>>> dropwizard meter maybe used instead of MeterView).
> > > >>>>>>>>>>>>>>>>>> 2. When connector specific metrics are added, it is
> > > >>>>>>>>>>>>>>>>> difficult to enforce
> > > >>>>>>>>>>>>>>>>>> the scope to be the same as standard metrics.
> > > >>>>>>>>>>>>>>>>>> 3. It seems that a method proliferation is
> inevitable
> > if
> > > >> we
> > > >>>>>>>>>>>>>>>>> want to apply
> > > >>>>>>>>>>>>>>>>>> sanity checks. e.g. The metric of numBytesIn was not
> > > >>>>>>>>>>>>>>>>> registered for a meter.
> > > >>>>>>>>>>>>>>>>>> 4. Metrics are still defined in random places and
> hard
> > > to
> > > >>>>>>>>>>>>>>>> track.
> > > >>>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>>> The current PR I had was inspired by the Config
> system
> > > in
> > > >>>>>>>>>>>>>>>>> Kafka, which I
> > > >>>>>>>>>>>>>>>>>> found pretty handy. In fact it is not only used by
> > Kafka
> > > >>>>>>>>>>>>>>>>> itself but even
> > > >>>>>>>>>>>>>>>>>> some other projects that depend on Kafka. I am not
> > > saying
> > > >>>>>>>>>>>>>>>>> this approach is
> > > >>>>>>>>>>>>>>>>>> perfect. But I think it worths to save the work for
> > > >>>>>>>>>>>>>>>>> connector writers and
> > > >>>>>>>>>>>>>>>>>> encourage more systematic implementation. That being
> > > said,
> > > >>>>>>>>>>>>>> I
> > > >>>>>>>>>>>>>>>>> am fully open
> > > >>>>>>>>>>>>>>>>>> to suggestions.
> > > >>>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>>> Re: Histogram
> > > >>>>>>>>>>>>>>>>>> I think there are two orthogonal questions around
> > those
> > > >>>>>>>>>>>>>>>> metrics:
> > > >>>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>>> 1. Regardless of the metric type, by just looking at
> > the
> > > >>>>>>>>>>>>>>>>> meaning of a
> > > >>>>>>>>>>>>>>>>>> metric, is generic to all connectors? If the answer
> is
> > > >> yes,
> > > >>>>>>>>>>>>>>>>> we should
> > > >>>>>>>>>>>>>>>>>> include the metric into the convention. No matter
> > > whether
> > > >>>>>>>>>>>>>> we
> > > >>>>>>>>>>>>>>>>> include it
> > > >>>>>>>>>>>>>>>>>> into the convention or not, some connector
> > > implementations
> > > >>>>>>>>>>>>>>>>> will emit such
> > > >>>>>>>>>>>>>>>>>> metric. It is better to have a convention than
> letting
> > > >> each
> > > >>>>>>>>>>>>>>>>> connector do
> > > >>>>>>>>>>>>>>>>>> random things.
> > > >>>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>>> 2. If a standard metric is a histogram, what should
> we
> > > do?
> > > >>>>>>>>>>>>>>>>>> I agree that we should make it clear that using
> > > histograms
> > > >>>>>>>>>>>>>>>>> will have
> > > >>>>>>>>>>>>>>>>>> performance risk. But I do see histogram is useful
> in
> > > some
> > > >>>>>>>>>>>>>>>>> fine-granularity
> > > >>>>>>>>>>>>>>>>>> debugging where one do not have the luxury to stop
> the
> > > >>>>>>>>>>>>>>>>> system and inject
> > > >>>>>>>>>>>>>>>>>> more inspection code. So the workaround I am
> thinking
> > is
> > > >> to
> > > >>>>>>>>>>>>>>>>> provide some
> > > >>>>>>>>>>>>>>>>>> implementation suggestions. Assume later on we have
> a
> > > >>>>>>>>>>>>>>>>> mechanism of
> > > >>>>>>>>>>>>>>>>>> selective metrics. In the abstract metrics class we
> > can
> > > >>>>>>>>>>>>>>>>> disable those
> > > >>>>>>>>>>>>>>>>>> metrics by default individual connector writers does
> > not
> > > >>>>>>>>>>>>>>>>> have to do
> > > >>>>>>>>>>>>>>>>>> anything (this is another advantage of having an
> > > >>>>>>>>>>>>>>>>> AbstractMetrics instead of
> > > >>>>>>>>>>>>>>>>>> static util methods.)
> > > >>>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>>> I am not sure I fully understand the histogram in
> the
> > > >>>>>>>>>>>>>>>>> backend approach. Can
> > > >>>>>>>>>>>>>>>>>> you explain a bit more? Do you mean emitting the raw
> > > data,
> > > >>>>>>>>>>>>>>>>> e.g. fetchTime
> > > >>>>>>>>>>>>>>>>>> and emitTime with each record and let the histogram
> > > >>>>>>>>>>>>>>>>> computation happen in
> > > >>>>>>>>>>>>>>>>>> the background? Or let the processing thread putting
> > the
> > > >>>>>>>>>>>>>>>>> values into a
> > > >>>>>>>>>>>>>>>>>> queue and have a separate thread polling from the
> > queue
> > > >> and
> > > >>>>>>>>>>>>>>>>> add them into
> > > >>>>>>>>>>>>>>>>>> the histogram?
> > > >>>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>>> Thanks,
> > > >>>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>>> Jiangjie (Becket) Qin
> > > >>>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>>> On Fri, Feb 22, 2019 at 4:34 PM Chesnay Schepler
> > > >>>>>>>>>>>>>>>>> <chesnay@apache.org <ma...@apache.org>>
> > > wrote:
> > > >>>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>>>> Re: Flip
> > > >>>>>>>>>>>>>>>>>>> The very first line under both the main header and
> > > >> Purpose
> > > >>>>>>>>>>>>>>>>> section
> > > >>>>>>>>>>>>>>>>>>> describe Flips as "major changes", which this
> isn't.
> > > >>>>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>>>> Re: complication
> > > >>>>>>>>>>>>>>>>>>> I'm not arguing against standardization, but again
> an
> > > >>>>>>>>>>>>>>>>> over-complicated
> > > >>>>>>>>>>>>>>>>>>> implementation when a static utility method would
> be
> > > >>>>>>>>>>>>>>>>> sufficient.
> > > >>>>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>>>> public static void setupConnectorMetrics(
> > > >>>>>>>>>>>>>>>>>>> MetricGroup operatorMetricGroup,
> > > >>>>>>>>>>>>>>>>>>> String connectorName,
> > > >>>>>>>>>>>>>>>>>>> Optional<Gauge<Long>> numRecordsIn,
> > > >>>>>>>>>>>>>>>>>>> ...)
> > > >>>>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>>>> This gives you all you need:
> > > >>>>>>>>>>>>>>>>>>> * a well-defined set of metrics for a connector to
> > > opt-in
> > > >>>>>>>>>>>>>>>>>>> * standardized naming schemes for scope and
> > individual
> > > >>>>>>>>>>>>>>> metrics
> > > >>>>>>>>>>>>>>>>>>> * standardize metric types (although personally I'm
> > not
> > > >>>>>>>>>>>>>>>>> interested in that
> > > >>>>>>>>>>>>>>>>>>> since metric types should be considered syntactic
> > > sugar)
> > > >>>>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>>>> Re: Configurable Histogram
> > > >>>>>>>>>>>>>>>>>>> If anything they _must_ be turned off by default,
> but
> > > the
> > > >>>>>>>>>>>>>>>>> metric system is
> > > >>>>>>>>>>>>>>>>>>> already exposing so many options that I'm not too
> > keen
> > > on
> > > >>>>>>>>>>>>>>>>> adding even more.
> > > >>>>>>>>>>>>>>>>>>> You have also only addressed my first argument
> > against
> > > >>>>>>>>>>>>>>>>> histograms
> > > >>>>>>>>>>>>>>>>>>> (performance), the second one still stands
> (calculate
> > > >>>>>>>>>>>>>>>>> histogram in metric
> > > >>>>>>>>>>>>>>>>>>> backends instead).
> > > >>>>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>>>> On 21.02.2019 16:27, Becket Qin wrote:
> > > >>>>>>>>>>>>>>>>>>>> Hi Chesnay,
> > > >>>>>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>>>>> Thanks for the comments. I think this is worthy
> of a
> > > >> FLIP
> > > >>>>>>>>>>>>>>>>> because it is
> > > >>>>>>>>>>>>>>>>>>>> public API. According to the FLIP description a
> FlIP
> > > is
> > > >>>>>>>>>>>>>>>>> required in case
> > > >>>>>>>>>>>>>>>>>>> of:
> > > >>>>>>>>>>>>>>>>>>>> - Any change that impacts the public interfaces of
> > > >>>>>>>>>>>>>>>>> the project
> > > >>>>>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>>>>> and the following entry is found in the definition
> > of
> > > >>>>>>>>>>>>>>>>> "public interface".
> > > >>>>>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>>>>> - Exposed monitoring information
> > > >>>>>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>>>>> Metrics are critical to any production system. So
> a
> > > >> clear
> > > >>>>>>>>>>>>>>>>> metric
> > > >>>>>>>>>>>>>>>>>>> definition
> > > >>>>>>>>>>>>>>>>>>>> is important for any serious users. For an
> > > organization
> > > >>>>>>>>>>>>>>>>> with large Flink
> > > >>>>>>>>>>>>>>>>>>>> installation, change in metrics means great amount
> > of
> > > >>>>>>>>>>>>>>>>> work. So such
> > > >>>>>>>>>>>>>>>>>>> changes
> > > >>>>>>>>>>>>>>>>>>>> do need to be fully discussed and documented.
> > > >>>>>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>>>>> ** Re: Histogram.
> > > >>>>>>>>>>>>>>>>>>>> We can discuss whether there is a better way to
> > expose
> > > >>>>>>>>>>>>>>>>> metrics that are
> > > >>>>>>>>>>>>>>>>>>>> suitable for histograms. My micro-benchmark on
> > various
> > > >>>>>>>>>>>>>>>>> histogram
> > > >>>>>>>>>>>>>>>>>>>> implementations also indicates that they are
> > > >>>>>>>>>>>>>> significantly
> > > >>>>>>>>>>>>>>>>> slower than
> > > >>>>>>>>>>>>>>>>>>>> other metric types. But I don't think that means
> > never
> > > >>>>>>>>>>>>>> use
> > > >>>>>>>>>>>>>>>>> histogram, but
> > > >>>>>>>>>>>>>>>>>>>> means use it with caution. For example, we can
> > suggest
> > > >>>>>>>>>>>>>> the
> > > >>>>>>>>>>>>>>>>>>> implementations
> > > >>>>>>>>>>>>>>>>>>>> to turn them off by default and only turn it on
> for
> > a
> > > >>>>>>>>>>>>>>>>> small amount of
> > > >>>>>>>>>>>>>>>>>>> time
> > > >>>>>>>>>>>>>>>>>>>> when performing some micro-debugging.
> > > >>>>>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>>>>> ** Re: complication:
> > > >>>>>>>>>>>>>>>>>>>> Connector conventions are essential for Flink
> > > ecosystem.
> > > >>>>>>>>>>>>>>>>> Flink connectors
> > > >>>>>>>>>>>>>>>>>>>> pool is probably the most important part of Flink,
> > > just
> > > >>>>>>>>>>>>>>>>> like any other
> > > >>>>>>>>>>>>>>>>>>> data
> > > >>>>>>>>>>>>>>>>>>>> system. Clear conventions of connectors will help
> > > build
> > > >>>>>>>>>>>>>>>>> Flink ecosystem
> > > >>>>>>>>>>>>>>>>>>> in
> > > >>>>>>>>>>>>>>>>>>>> a more organic way.
> > > >>>>>>>>>>>>>>>>>>>> Take the metrics convention as an example, imagine
> > > >>>>>>>>>>>>>> someone
> > > >>>>>>>>>>>>>>>>> has developed
> > > >>>>>>>>>>>>>>>>>>> a
> > > >>>>>>>>>>>>>>>>>>>> Flink connector for System foo, and another
> > developer
> > > >> may
> > > >>>>>>>>>>>>>>>>> have developed
> > > >>>>>>>>>>>>>>>>>>> a
> > > >>>>>>>>>>>>>>>>>>>> monitoring and diagnostic framework for Flink
> which
> > > >>>>>>>>>>>>>>>>> analyzes the Flink
> > > >>>>>>>>>>>>>>>>>>> job
> > > >>>>>>>>>>>>>>>>>>>> performance based on metrics. With a clear metric
> > > >>>>>>>>>>>>>>>>> convention, those two
> > > >>>>>>>>>>>>>>>>>>>> projects could be developed independently. Once
> > users
> > > >> put
> > > >>>>>>>>>>>>>>>>> them together,
> > > >>>>>>>>>>>>>>>>>>>> it would work without additional modifications.
> This
> > > >>>>>>>>>>>>>>>>> cannot be easily
> > > >>>>>>>>>>>>>>>>>>>> achieved by just defining a few constants.
> > > >>>>>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>>>>> ** Re: selective metrics:
> > > >>>>>>>>>>>>>>>>>>>> Sure, we can discuss that in a separate thread.
> > > >>>>>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>>>>> @Dawid
> > > >>>>>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>>>>> ** Re: latency / fetchedLatency
> > > >>>>>>>>>>>>>>>>>>>> The primary purpose of establish such a convention
> > is
> > > to
> > > >>>>>>>>>>>>>>>>> help developers
> > > >>>>>>>>>>>>>>>>>>>> write connectors in a more compatible way. The
> > > >> convention
> > > >>>>>>>>>>>>>>>>> is supposed to
> > > >>>>>>>>>>>>>>>>>>> be
> > > >>>>>>>>>>>>>>>>>>>> defined more proactively. So when look at the
> > > >> convention,
> > > >>>>>>>>>>>>>>>>> it seems more
> > > >>>>>>>>>>>>>>>>>>>> important to see if the concept is applicable to
> > > >>>>>>>>>>>>>>>>> connectors in general.
> > > >>>>>>>>>>>>>>>>>>> It
> > > >>>>>>>>>>>>>>>>>>>> might be true so far only Kafka connector reports
> > > >>>>>>>>>>>>>> latency.
> > > >>>>>>>>>>>>>>>>> But there
> > > >>>>>>>>>>>>>>>>>>> might
> > > >>>>>>>>>>>>>>>>>>>> be hundreds of other connector implementations in
> > the
> > > >>>>>>>>>>>>>>>>> Flink ecosystem,
> > > >>>>>>>>>>>>>>>>>>>> though not in the Flink repo, and some of them
> also
> > > >> emits
> > > >>>>>>>>>>>>>>>>> latency. I
> > > >>>>>>>>>>>>>>>>>>> think
> > > >>>>>>>>>>>>>>>>>>>> a lot of other sources actually also has an append
> > > >>>>>>>>>>>>>>>>> timestamp. e.g.
> > > >>>>>>>>>>>>>>>>>>> database
> > > >>>>>>>>>>>>>>>>>>>> bin logs and some K-V stores. So I wouldn't be
> > > surprised
> > > >>>>>>>>>>>>>>>>> if some database
> > > >>>>>>>>>>>>>>>>>>>> connector can also emit latency metrics.
> > > >>>>>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>>>>> Thanks,
> > > >>>>>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>>>>> Jiangjie (Becket) Qin
> > > >>>>>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>>>>> On Thu, Feb 21, 2019 at 10:14 PM Chesnay Schepler
> > > >>>>>>>>>>>>>>>>> <chesnay@apache.org <ma...@apache.org>>
> > > >>>>>>>>>>>>>>>>>>>> wrote:
> > > >>>>>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>>>>>> Regarding 2) It doesn't make sense to investigate
> > > this
> > > >>>>>>>>>>>>>> as
> > > >>>>>>>>>>>>>>>>> part of this
> > > >>>>>>>>>>>>>>>>>>>>> FLIP. This is something that could be of interest
> > for
> > > >>>>>>>>>>>>>> the
> > > >>>>>>>>>>>>>>>>> entire metric
> > > >>>>>>>>>>>>>>>>>>>>> system, and should be designed for as such.
> > > >>>>>>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>>>>>> Regarding the proposal as a whole:
> > > >>>>>>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>>>>>> Histogram metrics shall not be added to the core
> of
> > > >>>>>>>>>>>>>>>>> Flink. They are
> > > >>>>>>>>>>>>>>>>>>>>> significantly more expensive than other metrics,
> > and
> > > >>>>>>>>>>>>>>>>> calculating
> > > >>>>>>>>>>>>>>>>>>>>> histograms in the application is regarded as an
> > > >>>>>>>>>>>>>>>>> anti-pattern by several
> > > >>>>>>>>>>>>>>>>>>>>> metric backends, who instead recommend to expose
> > the
> > > >> raw
> > > >>>>>>>>>>>>>>>>> data and
> > > >>>>>>>>>>>>>>>>>>>>> calculate the histogram in the backend.
> > > >>>>>>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>>>>>> Second, this seems overly complicated. Given that
> > we
> > > >>>>>>>>>>>>>>>>> already established
> > > >>>>>>>>>>>>>>>>>>>>> that not all connectors will export all metrics
> we
> > > are
> > > >>>>>>>>>>>>>>>>> effectively
> > > >>>>>>>>>>>>>>>>>>>>> reducing this down to a consistent naming scheme.
> > We
> > > >>>>>>>>>>>>>>>>> don't need anything
> > > >>>>>>>>>>>>>>>>>>>>> sophisticated for that; basically just a few
> > > constants
> > > >>>>>>>>>>>>>>>>> that all
> > > >>>>>>>>>>>>>>>>>>>>> connectors use.
> > > >>>>>>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>>>>>> I'm not convinced that this is worthy of a FLIP.
> > > >>>>>>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>>>>>> On 21.02.2019 14:26, Dawid Wysakowicz wrote:
> > > >>>>>>>>>>>>>>>>>>>>>> Hi,
> > > >>>>>>>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>>>>>>> Ad 1. In general I undestand and I agree. But
> > those
> > > >>>>>>>>>>>>>>>>> particular metrics
> > > >>>>>>>>>>>>>>>>>>>>>> (latency, fetchLatency), right now would only be
> > > >>>>>>>>>>>>>>>>> reported if user uses
> > > >>>>>>>>>>>>>>>>>>>>>> KafkaConsumer with internal timestampAssigner
> with
> > > >>>>>>>>>>>>>>>>> StreamCharacteristic
> > > >>>>>>>>>>>>>>>>>>>>>> set to EventTime, right? That sounds like a very
> > > >>>>>>>>>>>>>>>>> specific case. I am
> > > >>>>>>>>>>>>>>>>>>> not
> > > >>>>>>>>>>>>>>>>>>>>>> sure if we should introduce a generic metric
> that
> > > will
> > > >>>>>>>>>>>>>> be
> > > >>>>>>>>>>>>>>>>>>>>>> disabled/absent for most of implementations.
> > > >>>>>>>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>>>>>>> Ad.2 That sounds like an orthogonal issue, that
> > > might
> > > >>>>>>>>>>>>>>>>> make sense to
> > > >>>>>>>>>>>>>>>>>>>>>> investigate in the future.
> > > >>>>>>>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>>>>>>> Best,
> > > >>>>>>>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>>>>>>> Dawid
> > > >>>>>>>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>>>>>>> On 21/02/2019 13:20, Becket Qin wrote:
> > > >>>>>>>>>>>>>>>>>>>>>>> Hi Dawid,
> > > >>>>>>>>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>>>>>>>> Thanks for the feedback. That makes sense to
> me.
> > > >> There
> > > >>>>>>>>>>>>>>>>> are two cases
> > > >>>>>>>>>>>>>>>>>>> to
> > > >>>>>>>>>>>>>>>>>>>>> be
> > > >>>>>>>>>>>>>>>>>>>>>>> addressed.
> > > >>>>>>>>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>>>>>>>> 1. The metrics are supposed to be a guidance.
> It
> > is
> > > >>>>>>>>>>>>>>>>> likely that a
> > > >>>>>>>>>>>>>>>>>>>>> connector
> > > >>>>>>>>>>>>>>>>>>>>>>> only supports some but not all of the metrics.
> In
> > > >> that
> > > >>>>>>>>>>>>>>>>> case, each
> > > >>>>>>>>>>>>>>>>>>>>> connector
> > > >>>>>>>>>>>>>>>>>>>>>>> implementation should have the freedom to
> decide
> > > >> which
> > > >>>>>>>>>>>>>>>>> metrics are
> > > >>>>>>>>>>>>>>>>>>>>>>> reported. For the metrics that are supported,
> the
> > > >>>>>>>>>>>>>>>>> guidance should be
> > > >>>>>>>>>>>>>>>>>>>>>>> followed.
> > > >>>>>>>>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>>>>>>>> 2. Sometimes users may want to disable certain
> > > >> metrics
> > > >>>>>>>>>>>>>>>>> for some reason
> > > >>>>>>>>>>>>>>>>>>>>>>> (e.g. performance / reprocessing of data). A
> > > generic
> > > >>>>>>>>>>>>>>>>> mechanism should
> > > >>>>>>>>>>>>>>>>>>> be
> > > >>>>>>>>>>>>>>>>>>>>>>> provided to allow user choose which metrics are
> > > >>>>>>>>>>>>>>>>> reported. This
> > > >>>>>>>>>>>>>>>>>>> mechanism
> > > >>>>>>>>>>>>>>>>>>>>>>> should also be honored by the connector
> > > >>>>>>>>>>>>>> implementations.
> > > >>>>>>>>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>>>>>>>> Does this sound reasonable to you?
> > > >>>>>>>>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>>>>>>>> Thanks,
> > > >>>>>>>>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>>>>>>>> Jiangjie (Becket) Qin
> > > >>>>>>>>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>>>>>>>> On Thu, Feb 21, 2019 at 4:22 PM Dawid
> Wysakowicz
> > <
> > > >>>>>>>>>>>>>>>>>>>>> dwysakowicz@apache.org <mailto:
> > > dwysakowicz@apache.org
> > > >>>>
> > > >>>>>>>>>>>>>>>>>>>>>>> wrote:
> > > >>>>>>>>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>>>>>>>>> Hi,
> > > >>>>>>>>>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>>>>>>>>> Generally I like the idea of having a unified,
> > > >>>>>>>>>>>>>>>>> standard set of
> > > >>>>>>>>>>>>>>>>>>> metrics
> > > >>>>>>>>>>>>>>>>>>>>> for
> > > >>>>>>>>>>>>>>>>>>>>>>>> all connectors. I have some slight concerns
> > about
> > > >>>>>>>>>>>>>>>>> fetchLatency and
> > > >>>>>>>>>>>>>>>>>>>>>>>> latency though. They are computed based on
> > > EventTime
> > > >>>>>>>>>>>>>>>>> which is not a
> > > >>>>>>>>>>>>>>>>>>>>> purely
> > > >>>>>>>>>>>>>>>>>>>>>>>> technical feature. It depends often on some
> > > business
> > > >>>>>>>>>>>>>>>>> logic, might be
> > > >>>>>>>>>>>>>>>>>>>>> absent
> > > >>>>>>>>>>>>>>>>>>>>>>>> or defined after source. Those metrics could
> > also
> > > >>>>>>>>>>>>>>>>> behave in a weird
> > > >>>>>>>>>>>>>>>>>>>>> way in
> > > >>>>>>>>>>>>>>>>>>>>>>>> case of replaying backlog. Therefore I am not
> > sure
> > > >> if
> > > >>>>>>>>>>>>>>>>> we should
> > > >>>>>>>>>>>>>>>>>>> include
> > > >>>>>>>>>>>>>>>>>>>>>>>> those metrics by default. Maybe we could at
> > least
> > > >>>>>>>>>>>>>>>>> introduce a feature
> > > >>>>>>>>>>>>>>>>>>>>>>>> switch for them? What do you think?
> > > >>>>>>>>>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>>>>>>>>> Best,
> > > >>>>>>>>>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>>>>>>>>> Dawid
> > > >>>>>>>>>>>>>>>>>>>>>>>> On 21/02/2019 03:13, Becket Qin wrote:
> > > >>>>>>>>>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>>>>>>>>> Bump. If there is no objections to the
> proposed
> > > >>>>>>>>>>>>>>>>> metrics. I'll start a
> > > >>>>>>>>>>>>>>>>>>>>>>>> voting thread later toady.
> > > >>>>>>>>>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>>>>>>>>> Thanks,
> > > >>>>>>>>>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>>>>>>>>> Jiangjie (Becket) Qin
> > > >>>>>>>>>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>>>>>>>>> On Mon, Feb 11, 2019 at 8:17 PM Becket Qin
> > > >>>>>>>>>>>>>>>>> <becket.qin@gmail.com <mailto:becket.qin@gmail.com
> >>
> > <
> > > >>>>>>>>>>>>>>>>>>>>> becket.qin@gmail.com <mailto:
> becket.qin@gmail.com
> > >>
> > > >>>>>>>>>>>>>>> wrote:
> > > >>>>>>>>>>>>>>>>>>>>>>>> Hi folks,
> > > >>>>>>>>>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>>>>>>>>> I would like to start the FLIP discussion
> thread
> > > >>>>>>>>>>>>>> about
> > > >>>>>>>>>>>>>>>>> standardize
> > > >>>>>>>>>>>>>>>>>>> the
> > > >>>>>>>>>>>>>>>>>>>>>>>> connector metrics.
> > > >>>>>>>>>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>>>>>>>>> In short, we would like to provide a
> convention
> > of
> > > >>>>>>>>>>>>>>>>> Flink connector
> > > >>>>>>>>>>>>>>>>>>>>>>>> metrics. It will help simplify the monitoring
> > and
> > > >>>>>>>>>>>>>>>>> alerting on Flink
> > > >>>>>>>>>>>>>>>>>>>>> jobs.
> > > >>>>>>>>>>>>>>>>>>>>>>>> The FLIP link is following:
> > > >>>>>>>>>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>
> > > >>>>>>>>>>>>
> > > >>>>>>>>>
> > > >>>>>>>
> > > >>>>>
> > > >>
> > >
> >
> https://cwiki.apache.org/confluence/display/FLINK/FLIP-33%3A+Standardize+Connector+Metrics
> > > >>>>>>>>>>>>>>>>>>>>>>>> Thanks,
> > > >>>>>>>>>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>>>>>>>>> Jiangjie (Becket) Qin
> > > >>>>>>>>>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>>
> > > >>>>>>>>>>>>>>
> > > >>>>>>>>>>>>
> > > >>>>>>>>>>>>
> > > >>>>>>>>>
> > > >>>>>>>>>
> > > >>>>>>>>>
> > > >>>>>>>
> > > >>>>>>>
> > > >>>>>>>
> > > >>>>>
> > > >>>>>
> > > >>
> > > >>
> > >
> > >
> >
>
>
> --
>
> Konstantin Knauf
>
> https://twitter.com/snntrable
>
> https://github.com/knaufk
>
Re: [DISCUSS] FLIP-33: Standardize connector metrics
Posted by Konstantin Knauf <kn...@apache.org>.
Hi Becket,
Thank you for picking up this FLIP. I have a few questions:
* two thoughts on naming:
* idleTime: In the meantime, a similar metric "idleTimeMsPerSecond" has
been introduced in https://issues.apache.org/jira/browse/FLINK-16864. They
have a similar name, but different definitions of idleness,
e.g. "idleTimeMsPerSecond" considers the SourceTask idle, when it is
backpressured. Can we make it clearer that these two metrics mean different
things?
* "current(Fetch)Latency" I am wondering if "eventTimeLag(Before|After)"
is more descriptive/clear. What do others think?
* Current(Fetch)Latency implies that the timestamps are directly
extracted in the source connector, right? Will this be the default for
FLIP-27 sources anyway?
* Does FLIP-33 also include the implementation of these metrics (to the
extent possible) for all connectors currently available in Apache Flink or
is the "per-connector implementation" out-of-scope?
Thanks,
Konstantin
On Fri, Sep 4, 2020 at 4:56 PM Becket Qin <be...@gmail.com> wrote:
> Hi all,
>
> To complete the Source refactoring work, I'd like to revive this
> discussion. Since the mail thread has been dormant for more than a year,
> just to recap the motivation of the FLIP:
>
> 1. The FLIP proposes to standardize the connector metrics by giving
> guidance on the metric specifications, including the name, type and meaning
> of the metrics.
> 2. It is OK for a connector to not emit some of the metrics in the metric
> guidance, but if a metric of the same semantic is emitted, the
> implementation should follow the guidance.
> 3. It is OK for a connector to emit more metrics than what are listed in
> the FLIP. This includes having an alias for a metric specified in the FLIP.
> 4. We will implement some of the metrics out of the box in the default
> implementation of FLIP-27, as long as it is applicable.
>
> The FLIP wiki is following:
> https://cwiki.apache.org/confluence/display/FLINK/FLIP-33
> %3A+Standardize+Connector+Metrics
>
> Any thoughts?
>
> Thanks,
>
> Jiangjie (Becket) Qin
>
>
> On Fri, Jun 14, 2019 at 2:29 PM Piotr Nowojski <pi...@ververica.com>
> wrote:
>
> > > we will need to revisit the convention list and adjust them accordingly
> > when FLIP-27 is ready
> >
> >
> > Yes, this sounds good :)
> >
> > Piotrek
> >
> > > On 13 Jun 2019, at 13:35, Becket Qin <be...@gmail.com> wrote:
> > >
> > > Hi Piotr,
> > >
> > > That's great to know. Chances are that we will need to revisit the
> > > convention list and adjust them accordingly when FLIP-27 is ready, At
> > that
> > > point we can mark some of the metrics as available by default for
> > > connectors implementing the new interface.
> > >
> > > Thanks,
> > >
> > > Jiangjie (Becket) Qin
> > >
> > > On Thu, Jun 13, 2019 at 3:51 PM Piotr Nowojski <pi...@ververica.com>
> > wrote:
> > >
> > >> Thanks for driving this. I’ve just noticed one small thing. With new
> > >> SourceReader interface Flink will be able to provide `idleTime` metric
> > >> automatically.
> > >>
> > >> Piotrek
> > >>
> > >>> On 13 Jun 2019, at 03:30, Becket Qin <be...@gmail.com> wrote:
> > >>>
> > >>> Thanks all for the feedback and discussion.
> > >>>
> > >>> Since there wasn't any concern raised, I've started the voting thread
> > for
> > >>> this FLIP, but please feel free to continue the discussion here if
> you
> > >>> think something still needs to be addressed.
> > >>>
> > >>> Thanks,
> > >>>
> > >>> Jiangjie (Becket) Qin
> > >>>
> > >>>
> > >>>
> > >>> On Mon, Jun 10, 2019 at 9:10 AM Becket Qin <be...@gmail.com>
> > wrote:
> > >>>
> > >>>> Hi Piotr,
> > >>>>
> > >>>> Thanks for the comments. Yes, you are right. Users will have to look
> > at
> > >>>> other metrics to decide whether the pipeline is healthy or not in
> the
> > >> first
> > >>>> place before they can use the time-based metric to fix the
> bottleneck.
> > >>>>
> > >>>> I agree that once we have FLIP-27 ready, some of the metrics can
> just
> > be
> > >>>> reported by the abstract implementation.
> > >>>>
> > >>>> I've updated FLIP-33 wiki page to add the pendingBytes and
> > >> pendingRecords
> > >>>> metric. Please let me know if you have any concern over the updated
> > >> metric
> > >>>> convention proposal.
> > >>>>
> > >>>> @Chesnay Schepler <ch...@apache.org> @Stephan Ewen
> > >>>> <st...@ververica.com> will you also have time to take a look at
> the
> > >>>> proposed metric convention? If there is no further concern I'll
> start
> > a
> > >>>> voting thread for this FLIP in two days.
> > >>>>
> > >>>> Thanks,
> > >>>>
> > >>>> Jiangjie (Becket) Qin
> > >>>>
> > >>>>
> > >>>>
> > >>>> On Wed, Jun 5, 2019 at 6:54 PM Piotr Nowojski <pi...@ververica.com>
> > >> wrote:
> > >>>>
> > >>>>> Hi Becket,
> > >>>>>
> > >>>>> Thanks for the answer :)
> > >>>>>
> > >>>>>> By time-based metric, I meant the portion of time spent on
> producing
> > >> the
> > >>>>>> record to downstream. For example, a source connector can report
> > that
> > >>>>> it's
> > >>>>>> spending 80% of time to emit record to downstream processing
> > pipeline.
> > >>>>> In
> > >>>>>> another case, a sink connector may report that its spending 30% of
> > >> time
> > >>>>>> producing the records to the external system.
> > >>>>>>
> > >>>>>> This is in some sense equivalent to the buffer usage metric:
> > >>>>>
> > >>>>>> - 80% of time spent on emitting records to downstream --->
> > downstream
> > >>>>>> node is bottleneck ---> output buffer is probably full.
> > >>>>>> - 30% of time spent on emitting records to downstream --->
> > downstream
> > >>>>>> node is not bottleneck ---> output buffer is probably not full.
> > >>>>>
> > >>>>> If by “time spent on emitting records to downstream” you understand
> > >>>>> “waiting on back pressure”, then I see your point. And I agree that
> > >> some
> > >>>>> kind of ratio/time based metric gives you more information. However
> > >> under
> > >>>>> “time spent on emitting records to downstream” might be hidden the
> > >>>>> following (extreme) situation:
> > >>>>>
> > >>>>> 1. Job is barely able to handle influx of records, there is 99%
> > >>>>> CPU/resource usage in the cluster, but nobody is
> > >>>>> bottlenecked/backpressured, all output buffers are empty, everybody
> > is
> > >>>>> waiting in 1% of it’s time for more records to process.
> > >>>>> 2. 80% time can still be spent on "down stream operators”, because
> > they
> > >>>>> are the CPU intensive operations, but this doesn’t mean that
> > >> increasing the
> > >>>>> parallelism down the stream will help with anything there. To the
> > >> contrary,
> > >>>>> increasing parallelism of the source operator might help to
> increase
> > >>>>> resource utilisation up to 100%.
> > >>>>>
> > >>>>> However, this “time based/ratio” approach can be extended to
> > in/output
> > >>>>> buffer usage. Besides collecting an information that input/output
> > >> buffer is
> > >>>>> full/empty, we can probe profile how often are buffer empty/full.
> If
> > >> output
> > >>>>> buffer is full 1% of times, there is almost no back pressure. If
> it’s
> > >> full
> > >>>>> 80% of times, there is some back pressure, if it’s full 99.9% of
> > times,
> > >>>>> there is huge back pressure.
> > >>>>>
> > >>>>> Now for autoscaling you could compare the input & output buffers
> fill
> > >>>>> ratio:
> > >>>>>
> > >>>>> 1. Both are high, the source of bottleneck is down the stream
> > >>>>> 2. Output is low, input is high, this is the bottleneck and the
> > higher
> > >>>>> the difference, the bigger source of bottleneck is this is
> > >> operator/task
> > >>>>> 3. Output is high, input is low - there was some load spike that we
> > are
> > >>>>> currently finishing to process
> > >>>>>
> > >>>>>
> > >>>>>
> > >>>>> But long story short, we are probably diverging from the topic of
> > this
> > >>>>> discussion, and we can discuss this at some later point.
> > >>>>>
> > >>>>> For now, for sources:
> > >>>>>
> > >>>>> as I wrote before, +1 for:
> > >>>>> - pending.bytes, Gauge
> > >>>>> - pending.messages, Gauge
> > >>>>>
> > >>>>> When we will be developing/discussing SourceReader from FLIP-27 we
> > >> might
> > >>>>> then add:
> > >>>>>
> > >>>>> - in-memory.buffer.usage (0 - 100%)
> > >>>>>
> > >>>>> Which will be estimated automatically by Flink while user will be
> > able
> > >> to
> > >>>>> override/provide better estimation.
> > >>>>>
> > >>>>> Piotrek
> > >>>>>
> > >>>>>> On 5 Jun 2019, at 05:42, Becket Qin <be...@gmail.com> wrote:
> > >>>>>>
> > >>>>>> Hi Piotr,
> > >>>>>>
> > >>>>>> Thanks for the explanation. Please see some clarifications below.
> > >>>>>>
> > >>>>>> By time-based metric, I meant the portion of time spent on
> producing
> > >> the
> > >>>>>> record to downstream. For example, a source connector can report
> > that
> > >>>>> it's
> > >>>>>> spending 80% of time to emit record to downstream processing
> > pipeline.
> > >>>>> In
> > >>>>>> another case, a sink connector may report that its spending 30% of
> > >> time
> > >>>>>> producing the records to the external system.
> > >>>>>>
> > >>>>>> This is in some sense equivalent to the buffer usage metric:
> > >>>>>> - 80% of time spent on emitting records to downstream --->
> > downstream
> > >>>>>> node is bottleneck ---> output buffer is probably full.
> > >>>>>> - 30% of time spent on emitting records to downstream --->
> > downstream
> > >>>>>> node is not bottleneck ---> output buffer is probably not full.
> > >>>>>>
> > >>>>>> However, the time-based metric has a few advantages that the
> buffer
> > >>>>> usage
> > >>>>>> metric may not have.
> > >>>>>>
> > >>>>>> 1. Buffer usage metric may not be applicable to all the connector
> > >>>>>> implementations, while reporting time-based metric are always
> > doable.
> > >>>>>> Some source connectors may not have any input buffer, or they may
> > use
> > >>>>> some
> > >>>>>> third party library that does not expose the input buffer at all.
> > >>>>>> Similarly, for sink connectors, the implementation may not have
> any
> > >>>>> output
> > >>>>>> buffer, or the third party library does not expose such buffer.
> > >>>>>>
> > >>>>>> 2. Although both type of metrics can detect bottleneck, time-based
> > >>>>> metrics
> > >>>>>> can be used to generate a more informed action to remove the
> > >> bottleneck.
> > >>>>>> For example, when the downstream is bottleneck, the output buffer
> > >> usage
> > >>>>>> metric is likely to be 100%, and the input buffer usage might be
> 0%.
> > >>>>> That
> > >>>>>> means we don't know what is the suitable parallelism to lift the
> > >>>>>> bottleneck. The time-based metric, on the other hand, would give
> > >> useful
> > >>>>>> information, e.g. if 80% of time was spent on emitting records, we
> > can
> > >>>>>> roughly increase the downstream node parallelism by 4 times.
> > >>>>>>
> > >>>>>> Admittedly, the time-based metrics are more expensive than buffer
> > >>>>> usage. So
> > >>>>>> we may have to do some sampling to reduce the cost. But in
> general,
> > >>>>> using
> > >>>>>> time-based metrics seems worth adding.
> > >>>>>>
> > >>>>>> That being said, I don't think buffer usage metric and time-based
> > >>>>> metrics
> > >>>>>> are mutually exclusive. We can probably have both. It is just that
> > in
> > >>>>>> practice, features like auto-scaling might prefer time-based
> metrics
> > >> for
> > >>>>>> the reason stated above.
> > >>>>>>
> > >>>>>>> 1. Define the metrics that would allow us to manually detect
> > >>>>> bottlenecks.
> > >>>>>> As I wrote, we already have them in most of the places, except of
> > >>>>>> sources/sinks.
> > >>>>>>> 2. Use those metrics, to automatically detect bottlenecks.
> > Currently
> > >> we
> > >>>>>> are only automatically detecting back pressure and reporting it to
> > the
> > >>>>> user
> > >>>>>> in web UI (is it exposed as a metric at all?). Detecting the root
> > >> cause
> > >>>>> of
> > >>>>>> the back pressure (bottleneck) is one step further.
> > >>>>>>> 3. Use the knowledge about where exactly the bottleneck is
> located,
> > >> to
> > >>>>>> try to do something with it.
> > >>>>>>
> > >>>>>> As explained above, I think time-based metric also addresses item
> 1
> > >> and
> > >>>>>> item 2.
> > >>>>>>
> > >>>>>> Any thoughts？
> > >>>>>>
> > >>>>>> Thanks,
> > >>>>>>
> > >>>>>> Jiangjie (Becket) Qin
> > >>>>>>
> > >>>>>>
> > >>>>>>
> > >>>>>> On Mon, Jun 3, 2019 at 4:14 PM Piotr Nowojski <
> piotr@ververica.com>
> > >>>>> wrote:
> > >>>>>>
> > >>>>>>> Hi again :)
> > >>>>>>>
> > >>>>>>>> - pending.bytes, Gauge
> > >>>>>>>> - pending.messages, Gauge
> > >>>>>>>
> > >>>>>>>
> > >>>>>>> +1
> > >>>>>>>
> > >>>>>>> And true, instead of overloading one of the metric it is better
> > when
> > >>>>> user
> > >>>>>>> can choose to provide only one of them.
> > >>>>>>>
> > >>>>>>> Re 2:
> > >>>>>>>
> > >>>>>>>> If I understand correctly, this metric along with the pending
> > >> mesages
> > >>>>> /
> > >>>>>>>> bytes would answer the questions of:
> > >>>>>>>
> > >>>>>>>> - Does the connector consume fast enough? Lagging behind + empty
> > >>>>> buffer
> > >>>>>>> =
> > >>>>>>>> cannot consume fast enough.
> > >>>>>>>> - Does the connector emit fast enough? Lagging behind + full
> > buffer
> > >> =
> > >>>>>>>> cannot emit fast enough, i.e. the Flink pipeline is slow.
> > >>>>>>>
> > >>>>>>> Yes, exactly. This can also be used to support decisions like
> > >> changing
> > >>>>> the
> > >>>>>>> parallelism of the sources and/or down stream operators.
> > >>>>>>>
> > >>>>>>> I’m not sure if I understand your proposal with time based
> > >>>>> measurements.
> > >>>>>>> Maybe I’m missing something, but I do not see how measuring time
> > >> alone
> > >>>>>>> could answer the problem: where is the bottleneck. Time spent on
> > the
> > >>>>>>> next/emit might be short or long (depending on how heavy to
> process
> > >> the
> > >>>>>>> record is) and the source can still be bottlenecked/back
> pressured
> > or
> > >>>>> not.
> > >>>>>>> Usually the easiest and the most reliable way how to detect
> > >>>>> bottlenecks is
> > >>>>>>> by checking usage of input & output buffers, since when input
> > buffer
> > >> is
> > >>>>>>> full while output buffer is empty, that’s the definition of a
> > >>>>> bottleneck.
> > >>>>>>> Also this is usually very easy and cheap to measure (it works
> > >>>>> effectively
> > >>>>>>> the same way as current’s Flink back pressure monitoring, but
> more
> > >>>>> cleanly,
> > >>>>>>> without probing thread’s stack traces).
> > >>>>>>>
> > >>>>>>> Also keep in mind that we are already using the buffer usage
> > metrics
> > >>>>> for
> > >>>>>>> detecting the bottlenecks in Flink’s internal network exchanges
> > >> (manual
> > >>>>>>> work). That’s the reason why I wanted to extend this to
> > >> sources/sinks,
> > >>>>>>> since they are currently our blind spot.
> > >>>>>>>
> > >>>>>>>> One feature we are currently working on to scale Flink
> > automatically
> > >>>>>>> relies
> > >>>>>>>> on some metrics answering the same question
> > >>>>>>>
> > >>>>>>> That would be very helpful feature. I think in order to achieve
> > that
> > >> we
> > >>>>>>> would need to:
> > >>>>>>> 1. Define the metrics that would allow us to manually detect
> > >>>>> bottlenecks.
> > >>>>>>> As I wrote, we already have them in most of the places, except of
> > >>>>>>> sources/sinks.
> > >>>>>>> 2. Use those metrics, to automatically detect bottlenecks.
> > Currently
> > >> we
> > >>>>>>> are only automatically detecting back pressure and reporting it
> to
> > >> the
> > >>>>> user
> > >>>>>>> in web UI (is it exposed as a metric at all?). Detecting the root
> > >>>>> cause of
> > >>>>>>> the back pressure (bottleneck) is one step further.
> > >>>>>>> 3. Use the knowledge about where exactly the bottleneck is
> located,
> > >> to
> > >>>>> try
> > >>>>>>> to do something with it.
> > >>>>>>>
> > >>>>>>> I think you are aiming for point 3., but before we reach it, we
> are
> > >>>>> still
> > >>>>>>> missing 1. & 2. Also even if we have 3., there is a value in 1 &
> 2
> > >> for
> > >>>>>>> manual analysis/dashboards.
> > >>>>>>>
> > >>>>>>> However, having the knowledge of where the bottleneck is, doesn’t
> > >>>>>>> necessarily mean that we know what we can do about it. For
> example
> > >>>>>>> increasing parallelism might or might not help with anything
> (data
> > >>>>> skew,
> > >>>>>>> bottleneck on some resource that does not scale), but this remark
> > >>>>> applies
> > >>>>>>> always, regardless of the way how did we detect the bottleneck.
> > >>>>>>>
> > >>>>>>> Piotrek
> > >>>>>>>
> > >>>>>>>> On 3 Jun 2019, at 06:16, Becket Qin <be...@gmail.com>
> wrote:
> > >>>>>>>>
> > >>>>>>>> Hi Piotr,
> > >>>>>>>>
> > >>>>>>>> Thanks for the suggestion. Some thoughts below:
> > >>>>>>>>
> > >>>>>>>> Re 1: The pending messages / bytes.
> > >>>>>>>> I completely agree these are very useful metrics and we should
> > >> expect
> > >>>>> the
> > >>>>>>>> connector to report. WRT the way to expose them, it seems more
> > >>>>> consistent
> > >>>>>>>> to add two metrics instead of adding a method (unless there are
> > >> other
> > >>>>> use
> > >>>>>>>> cases other than metric reporting). So we can add the following
> > two
> > >>>>>>> metrics.
> > >>>>>>>> - pending.bytes, Gauge
> > >>>>>>>> - pending.messages, Gauge
> > >>>>>>>> Applicable connectors can choose to report them. These two
> metrics
> > >>>>> along
> > >>>>>>>> with latency should be sufficient for users to understand the
> > >> progress
> > >>>>>>> of a
> > >>>>>>>> connector.
> > >>>>>>>>
> > >>>>>>>>
> > >>>>>>>> Re 2: Number of buffered data in-memory of the connector
> > >>>>>>>> If I understand correctly, this metric along with the pending
> > >> mesages
> > >>>>> /
> > >>>>>>>> bytes would answer the questions of:
> > >>>>>>>> - Does the connector consume fast enough? Lagging behind + empty
> > >>>>> buffer
> > >>>>>>> =
> > >>>>>>>> cannot consume fast enough.
> > >>>>>>>> - Does the connector emit fast enough? Lagging behind + full
> > buffer
> > >> =
> > >>>>>>>> cannot emit fast enough, i.e. the Flink pipeline is slow.
> > >>>>>>>>
> > >>>>>>>> One feature we are currently working on to scale Flink
> > automatically
> > >>>>>>> relies
> > >>>>>>>> on some metrics answering the same question, more specifically,
> we
> > >> are
> > >>>>>>>> profiling the time spent on .next() method (time to consume) and
> > the
> > >>>>> time
> > >>>>>>>> spent on .collect() method (time to emit / process). One
> advantage
> > >> of
> > >>>>>>> such
> > >>>>>>>> method level time cost allows us to calculate the parallelism
> > >>>>> required to
> > >>>>>>>> keep up in case their is a lag.
> > >>>>>>>>
> > >>>>>>>> However, one concern I have regarding such metric is that they
> are
> > >>>>>>>> implementation specific. Either profiling on the method time, or
> > >>>>>>> reporting
> > >>>>>>>> buffer usage assumes the connector are implemented in such a
> way.
> > A
> > >>>>>>>> slightly better solution might be have the following metric:
> > >>>>>>>>
> > >>>>>>>> - EmitTimeRatio (or FetchTimeRatio): The time spent on emitting
> > >>>>>>>> records / Total time elapsed.
> > >>>>>>>>
> > >>>>>>>> This assumes that the source connectors have to emit the records
> > to
> > >>>>> the
> > >>>>>>>> downstream at some point. The emission may take some time ( e.g.
> > go
> > >>>>>>> through
> > >>>>>>>> chained operators). And the rest of the time are spent to
> prepare
> > >> the
> > >>>>>>>> record to emit, including time for consuming and format
> > conversion,
> > >>>>> etc.
> > >>>>>>>> Ideally, we'd like to see the time spent on record fetch and
> emit
> > to
> > >>>>> be
> > >>>>>>>> about the same, so no one is bottleneck for the other.
> > >>>>>>>>
> > >>>>>>>> The downside of these time based metrics is additional overhead
> to
> > >> get
> > >>>>>>> the
> > >>>>>>>> time, therefore sampling might be needed. But in practice I feel
> > >> such
> > >>>>>>> time
> > >>>>>>>> based metric might be more useful if we want to take action.
> > >>>>>>>>
> > >>>>>>>>
> > >>>>>>>> I think we should absolutely add metrics in (1) to the metric
> > >>>>> convention.
> > >>>>>>>> We could also add the metrics mentioned in (2) if we reach
> > consensus
> > >>>>> on
> > >>>>>>>> that. What do you think?
> > >>>>>>>>
> > >>>>>>>> Thanks,
> > >>>>>>>>
> > >>>>>>>> Jiangjie (Becket) Qin
> > >>>>>>>>
> > >>>>>>>>
> > >>>>>>>> On Fri, May 31, 2019 at 4:26 PM Piotr Nowojski <
> > piotr@ververica.com
> > >>>
> > >>>>>>> wrote:
> > >>>>>>>>
> > >>>>>>>>> Hey Becket,
> > >>>>>>>>>
> > >>>>>>>>> Re 1a) and 1b) +1 from my side.
> > >>>>>>>>>
> > >>>>>>>>> I’ve discussed this issue:
> > >>>>>>>>>
> > >>>>>>>>>>>>
> > >>>>>>>>>>>> 2. It would be nice to have metrics, that allow us to check
> > the
> > >>>>> cause
> > >>>>>>>>> of
> > >>>>>>>>>>>> back pressure:
> > >>>>>>>>>>>> a) for sources, length of input queue (in bytes? Or boolean
> > >>>>>>>>>>>> hasSomethingl/isEmpty)
> > >>>>>>>>>>>> b) for sinks, length of output queue (in bytes? Or boolean
> > >>>>>>>>>>>> hasSomething/isEmpty)
> > >>>>>>>>>
> > >>>>>>>>> With Nico at some lengths and he also saw the benefits of them.
> > We
> > >>>>> also
> > >>>>>>>>> have more concrete proposal for that.
> > >>>>>>>>>
> > >>>>>>>>> Actually there are two really useful metrics, that we are
> missing
> > >>>>>>>>> currently:
> > >>>>>>>>>
> > >>>>>>>>> 1. Number of data/records/bytes in the backlog to process. For
> > >>>>> example
> > >>>>>>>>> remaining number of bytes in unread files. Or pending data in
> > Kafka
> > >>>>>>> topics.
> > >>>>>>>>> 2. Number of buffered data in-memory of the connector, that are
> > >>>>> waiting
> > >>>>>>> to
> > >>>>>>>>> be processed pushed to Flink pipeline.
> > >>>>>>>>>
> > >>>>>>>>> Re 1:
> > >>>>>>>>> This would have to be a metric provided directly by a
> connector.
> > It
> > >>>>>>> could
> > >>>>>>>>> be an undefined `int`:
> > >>>>>>>>>
> > >>>>>>>>> `int backlog` - estimate of pending work.
> > >>>>>>>>>
> > >>>>>>>>> “Undefined” meaning that it would be up to a connector to
> decided
> > >>>>>>> whether
> > >>>>>>>>> it’s measured in bytes, records, pending files or whatever it
> is
> > >>>>>>> possible
> > >>>>>>>>> to provide by the connector. This is because I assume not every
> > >>>>>>> connector
> > >>>>>>>>> can provide exact number and for some of them it might be
> > >> impossible
> > >>>>> to
> > >>>>>>>>> provide records number of bytes count.
> > >>>>>>>>>
> > >>>>>>>>> Re 2:
> > >>>>>>>>> This metric could be either provided by a connector, or
> > calculated
> > >>>>>>> crudely
> > >>>>>>>>> by Flink:
> > >>>>>>>>>
> > >>>>>>>>> `float bufferUsage` - value from [0.0, 1.0] range
> > >>>>>>>>>
> > >>>>>>>>> Percentage of used in memory buffers, like in Kafka’s handover.
> > >>>>>>>>>
> > >>>>>>>>> It could be crudely implemented by Flink with FLIP-27
> > >>>>>>>>> SourceReader#isAvailable. If SourceReader is not available
> > reported
> > >>>>>>>>> `bufferUsage` could be 0.0. If it is available, it could be
> 1.0.
> > I
> > >>>>> think
> > >>>>>>>>> this would be a good enough estimation for most of the use
> cases
> > >>>>> (that
> > >>>>>>>>> could be overloaded and implemented better if desired).
> > Especially
> > >>>>>>> since we
> > >>>>>>>>> are reporting only probed values: if probed values are almost
> > >> always
> > >>>>>>> “1.0”,
> > >>>>>>>>> it would mean that we have a back pressure. If they are almost
> > >> always
> > >>>>>>>>> “0.0”, there is probably no back pressure at the sources.
> > >>>>>>>>>
> > >>>>>>>>> What do you think about this?
> > >>>>>>>>>
> > >>>>>>>>> Piotrek
> > >>>>>>>>>
> > >>>>>>>>>> On 30 May 2019, at 11:41, Becket Qin <be...@gmail.com>
> > >> wrote:
> > >>>>>>>>>>
> > >>>>>>>>>> Hi all,
> > >>>>>>>>>>
> > >>>>>>>>>> Thanks a lot for all the feedback and comments. I'd like to
> > >> continue
> > >>>>>>> the
> > >>>>>>>>>> discussion on this FLIP.
> > >>>>>>>>>>
> > >>>>>>>>>> I updated the FLIP-33 wiki to remove all the histogram metrics
> > >> from
> > >>>>> the
> > >>>>>>>>>> first version of metric convention due to the performance
> > concern.
> > >>>>> The
> > >>>>>>>>> plan
> > >>>>>>>>>> is to introduce them later when we have a mechanism to opt
> > in/out
> > >>>>>>>>> metrics.
> > >>>>>>>>>> At that point, users can decide whether they want to pay the
> > cost
> > >> to
> > >>>>>>> get
> > >>>>>>>>>> the metric or not.
> > >>>>>>>>>>
> > >>>>>>>>>> As Stephan suggested, for this FLIP, let's first try to agree
> on
> > >> the
> > >>>>>>>>> small
> > >>>>>>>>>> list of conventional metrics that connectors should follow.
> > >>>>>>>>>> Just to be clear, the purpose of the convention is not to
> > enforce
> > >>>>> every
> > >>>>>>>>>> connector to report all these metrics, but to provide a
> guidance
> > >> in
> > >>>>>>> case
> > >>>>>>>>>> these metrics are reported by some connectors.
> > >>>>>>>>>>
> > >>>>>>>>>>
> > >>>>>>>>>> @ Stephan & Chesnay,
> > >>>>>>>>>>
> > >>>>>>>>>> Regarding the duplication of `RecordsIn` metric in operator /
> > task
> > >>>>>>>>>> IOMetricGroups, from what I understand, for source operator,
> it
> > is
> > >>>>>>>>> actually
> > >>>>>>>>>> the SourceFunction that reports the operator level
> > >>>>>>>>>> RecordsIn/RecordsInPerSecond metric. So they are essentially
> the
> > >>>>> same
> > >>>>>>>>>> metric in the operator level IOMetricGroup. Similarly for the
> > Sink
> > >>>>>>>>>> operator, the operator level RecordsOut/RecordsOutPerSecond
> > >> metrics
> > >>>>> are
> > >>>>>>>>>> also reported by the Sink function. I marked them as existing
> in
> > >> the
> > >>>>>>>>>> FLIP-33 wiki page. Please let me know if I misunderstood.
> > >>>>>>>>>>
> > >>>>>>>>>> Thanks,
> > >>>>>>>>>>
> > >>>>>>>>>> Jiangjie (Becket) Qin
> > >>>>>>>>>>
> > >>>>>>>>>>
> > >>>>>>>>>> On Thu, May 30, 2019 at 5:16 PM Becket Qin <
> > becket.qin@gmail.com>
> > >>>>>>> wrote:
> > >>>>>>>>>>
> > >>>>>>>>>>> Hi Piotr,
> > >>>>>>>>>>>
> > >>>>>>>>>>> Thanks a lot for the feedback.
> > >>>>>>>>>>>
> > >>>>>>>>>>> 1a) I guess you are referring to the part that "original
> system
> > >>>>>>> specific
> > >>>>>>>>>>> metrics should also be reported". The performance impact
> > depends
> > >> on
> > >>>>>>> the
> > >>>>>>>>>>> implementation. An efficient implementation would only record
> > the
> > >>>>>>> metric
> > >>>>>>>>>>> once, but report them with two different metric names. This
> is
> > >>>>>>> unlikely
> > >>>>>>>>> to
> > >>>>>>>>>>> hurt performance.
> > >>>>>>>>>>>
> > >>>>>>>>>>> 1b) Yes, I agree that we should avoid adding overhead to the
> > >>>>> critical
> > >>>>>>>>> path
> > >>>>>>>>>>> by all means. This is sometimes a tradeoff, running blindly
> > >> without
> > >>>>>>> any
> > >>>>>>>>>>> metric gives best performance, but sometimes might be
> > frustrating
> > >>>>> when
> > >>>>>>>>> we
> > >>>>>>>>>>> debug some issues.
> > >>>>>>>>>>>
> > >>>>>>>>>>> 2. The metrics are indeed very useful. Are they supposed to
> be
> > >>>>>>> reported
> > >>>>>>>>> by
> > >>>>>>>>>>> the connectors or Flink itself? At this point FLIP-33 is more
> > >>>>> focused
> > >>>>>>> on
> > >>>>>>>>>>> provide a guidance to the connector authors on the metrics
> > >>>>> reporting.
> > >>>>>>>>> That
> > >>>>>>>>>>> said, after FLIP-27, I think we should absolutely report
> these
> > >>>>> metrics
> > >>>>>>>>> in
> > >>>>>>>>>>> the abstract implementation. In any case, the metric
> convention
> > >> in
> > >>>>>>> this
> > >>>>>>>>>>> list are expected to evolve over time.
> > >>>>>>>>>>>
> > >>>>>>>>>>> Thanks,
> > >>>>>>>>>>>
> > >>>>>>>>>>> Jiangjie (Becket) Qin
> > >>>>>>>>>>>
> > >>>>>>>>>>> On Tue, May 28, 2019 at 6:24 PM Piotr Nowojski <
> > >>>>> piotr@ververica.com>
> > >>>>>>>>>>> wrote:
> > >>>>>>>>>>>
> > >>>>>>>>>>>> Hi,
> > >>>>>>>>>>>>
> > >>>>>>>>>>>> Thanks for the proposal and driving the effort here Becket
> :)
> > >> I’ve
> > >>>>>>> read
> > >>>>>>>>>>>> through the FLIP-33 [1], and here are couple of my thoughts.
> > >>>>>>>>>>>>
> > >>>>>>>>>>>> Big +1 for standardising the metric names between
> connectors,
> > it
> > >>>>> will
> > >>>>>>>>>>>> definitely help us and users a lot.
> > >>>>>>>>>>>>
> > >>>>>>>>>>>> Issues/questions/things to discuss that I’ve thought of:
> > >>>>>>>>>>>>
> > >>>>>>>>>>>> 1a. If we are about to duplicate some metrics, can this
> > become a
> > >>>>>>>>>>>> performance issue?
> > >>>>>>>>>>>> 1b. Generally speaking, we should make sure that collecting
> > >> those
> > >>>>>>>>> metrics
> > >>>>>>>>>>>> is as non intrusive as possible, especially that they will
> > need
> > >>>>> to be
> > >>>>>>>>>>>> updated once per record. (They might be collected more
> rarely
> > >> with
> > >>>>>>> some
> > >>>>>>>>>>>> overhead, but the hot path of updating it per record will
> need
> > >> to
> > >>>>> be
> > >>>>>>> as
> > >>>>>>>>>>>> quick as possible). That includes both avoiding heavy
> > >> computation
> > >>>>> on
> > >>>>>>>>> per
> > >>>>>>>>>>>> record path: histograms?, measuring time for time based
> > metrics
> > >>>>> (per
> > >>>>>>>>>>>> second) (System.currentTimeMillis() depending on the
> > >>>>> implementation
> > >>>>>>> can
> > >>>>>>>>>>>> invoke a system call)
> > >>>>>>>>>>>>
> > >>>>>>>>>>>> 2. It would be nice to have metrics, that allow us to check
> > the
> > >>>>> cause
> > >>>>>>>>> of
> > >>>>>>>>>>>> back pressure:
> > >>>>>>>>>>>> a) for sources, length of input queue (in bytes? Or boolean
> > >>>>>>>>>>>> hasSomethingl/isEmpty)
> > >>>>>>>>>>>> b) for sinks, length of output queue (in bytes? Or boolean
> > >>>>>>>>>>>> hasSomething/isEmpty)
> > >>>>>>>>>>>>
> > >>>>>>>>>>>> a) is useful in a scenario when we are processing backlog of
> > >>>>> records,
> > >>>>>>>>> all
> > >>>>>>>>>>>> of the internal Flink’s input/output network buffers are
> > empty,
> > >>>>> and
> > >>>>>>> we
> > >>>>>>>>> want
> > >>>>>>>>>>>> to check whether the external source system is the
> bottleneck
> > >>>>>>> (source’s
> > >>>>>>>>>>>> input queue will be empty), or if the Flink’s connector is
> the
> > >>>>>>>>> bottleneck
> > >>>>>>>>>>>> (source’s input queues will be full).
> > >>>>>>>>>>>> b) similar story. Backlog of records, but this time all of
> the
> > >>>>>>> internal
> > >>>>>>>>>>>> Flink’s input/ouput network buffers are full, and we want o
> > >> check
> > >>>>>>>>> whether
> > >>>>>>>>>>>> the external sink system is the bottleneck (sink output
> queues
> > >> are
> > >>>>>>>>> full),
> > >>>>>>>>>>>> or if the Flink’s connector is the bottleneck (sink’s output
> > >>>>> queues
> > >>>>>>>>> will be
> > >>>>>>>>>>>> empty)
> > >>>>>>>>>>>>
> > >>>>>>>>>>>> It might be sometimes difficult to provide those metrics, so
> > >> they
> > >>>>>>> could
> > >>>>>>>>>>>> be optional, but if we could provide them, it would be
> really
> > >>>>>>> helpful.
> > >>>>>>>>>>>>
> > >>>>>>>>>>>> Piotrek
> > >>>>>>>>>>>>
> > >>>>>>>>>>>> [1]
> > >>>>>>>>>>>>
> > >>>>>>>>>
> > >>>>>>>
> > >>>>>
> > >>
> >
> https://cwiki.apache.org/confluence/display/FLINK/FLIP-33:+Standardize+Connector+Metrics
> > >>>>>>>>>>>> <
> > >>>>>>>>>>>>
> > >>>>>>>>>
> > >>>>>>>
> > >>>>>
> > >>
> >
> https://cwiki.apache.org/confluence/display/FLINK/FLIP-33:+Standardize+Connector+Metrics
> > >>>>>>>>>>>>>
> > >>>>>>>>>>>>
> > >>>>>>>>>>>>> On 24 Apr 2019, at 13:28, Stephan Ewen <se...@apache.org>
> > >> wrote:
> > >>>>>>>>>>>>>
> > >>>>>>>>>>>>> I think this sounds reasonable.
> > >>>>>>>>>>>>>
> > >>>>>>>>>>>>> Let's keep the "reconfiguration without stopping the job"
> out
> > >> of
> > >>>>>>> this,
> > >>>>>>>>>>>>> because that would be a super big effort and if we approach
> > >> that,
> > >>>>>>> then
> > >>>>>>>>>>>> in
> > >>>>>>>>>>>>> more generic way rather than specific to connector metrics.
> > >>>>>>>>>>>>>
> > >>>>>>>>>>>>> I would suggest to look at the following things before
> > starting
> > >>>>> with
> > >>>>>>>>> any
> > >>>>>>>>>>>>> implementation work:
> > >>>>>>>>>>>>>
> > >>>>>>>>>>>>> - Try and find a committer to support this, otherwise it
> will
> > >> be
> > >>>>>>> hard
> > >>>>>>>>>>>> to
> > >>>>>>>>>>>>> make progress
> > >>>>>>>>>>>>> - Start with defining a smaller set of "core metrics" and
> > >> extend
> > >>>>> the
> > >>>>>>>>>>>> set
> > >>>>>>>>>>>>> later. I think that is easier than now blocking on reaching
> > >>>>>>> consensus
> > >>>>>>>>>>>> on a
> > >>>>>>>>>>>>> large group of metrics.
> > >>>>>>>>>>>>> - Find a solution to the problem Chesnay mentioned, that
> the
> > >>>>>>> "records
> > >>>>>>>>>>>> in"
> > >>>>>>>>>>>>> metric is somehow overloaded and exists already in the IO
> > >> Metric
> > >>>>>>>>> group.
> > >>>>>>>>>>>>>
> > >>>>>>>>>>>>>
> > >>>>>>>>>>>>> On Mon, Mar 25, 2019 at 7:16 AM Becket Qin <
> > >> becket.qin@gmail.com
> > >>>>>>
> > >>>>>>>>>>>> wrote:
> > >>>>>>>>>>>>>
> > >>>>>>>>>>>>>> Hi Stephan,
> > >>>>>>>>>>>>>>
> > >>>>>>>>>>>>>> Thanks a lot for the feedback. All makes sense.
> > >>>>>>>>>>>>>>
> > >>>>>>>>>>>>>> It is a good suggestion to simply have an
> onRecord(numBytes,
> > >>>>>>>>> eventTime)
> > >>>>>>>>>>>>>> method for connector writers. It should meet most of the
> > >>>>>>>>> requirements,
> > >>>>>>>>>>>>>> individual
> > >>>>>>>>>>>>>>
> > >>>>>>>>>>>>>> The configurable metrics feature is something really
> useful,
> > >>>>>>>>>>>> especially if
> > >>>>>>>>>>>>>> we can somehow make it dynamically configurable without
> > >> stopping
> > >>>>>>> the
> > >>>>>>>>>>>> jobs.
> > >>>>>>>>>>>>>> It might be better to make it a separate discussion
> because
> > it
> > >>>>> is a
> > >>>>>>>>>>>> more
> > >>>>>>>>>>>>>> generic feature instead of only for connectors.
> > >>>>>>>>>>>>>>
> > >>>>>>>>>>>>>> So in order to make some progress, in this FLIP we can
> limit
> > >> the
> > >>>>>>>>>>>> discussion
> > >>>>>>>>>>>>>> scope to the connector related items:
> > >>>>>>>>>>>>>>
> > >>>>>>>>>>>>>> - the standard connector metric names and types.
> > >>>>>>>>>>>>>> - the abstract ConnectorMetricHandler interface
> > >>>>>>>>>>>>>>
> > >>>>>>>>>>>>>> I'll start a separate thread to discuss other general
> metric
> > >>>>>>> related
> > >>>>>>>>>>>>>> enhancement items including:
> > >>>>>>>>>>>>>>
> > >>>>>>>>>>>>>> - optional metrics
> > >>>>>>>>>>>>>> - dynamic metric configuration
> > >>>>>>>>>>>>>> - potential combination with rate limiter
> > >>>>>>>>>>>>>>
> > >>>>>>>>>>>>>> Does this plan sound reasonable?
> > >>>>>>>>>>>>>>
> > >>>>>>>>>>>>>> Thanks,
> > >>>>>>>>>>>>>>
> > >>>>>>>>>>>>>> Jiangjie (Becket) Qin
> > >>>>>>>>>>>>>>
> > >>>>>>>>>>>>>> On Sat, Mar 23, 2019 at 5:53 AM Stephan Ewen <
> > >> sewen@apache.org>
> > >>>>>>>>> wrote:
> > >>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>> Ignoring for a moment implementation details, this
> > connector
> > >>>>>>> metrics
> > >>>>>>>>>>>> work
> > >>>>>>>>>>>>>>> is a really good thing to do, in my opinion
> > >>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>> The questions "oh, my job seems to be doing nothing, I am
> > >>>>> looking
> > >>>>>>> at
> > >>>>>>>>>>>> the
> > >>>>>>>>>>>>>> UI
> > >>>>>>>>>>>>>>> and the 'records in' value is still zero" is in the top
> > three
> > >>>>>>>>> support
> > >>>>>>>>>>>>>>> questions I have been asked personally.
> > >>>>>>>>>>>>>>> Introspection into "how far is the consumer lagging
> behind"
> > >>>>> (event
> > >>>>>>>>>>>> time
> > >>>>>>>>>>>>>>> fetch latency) came up many times as well.
> > >>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>> So big +1 to solving this problem.
> > >>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>> About the exact design - I would try to go for the
> > following
> > >>>>>>>>>>>> properties:
> > >>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>> - keep complexity of of connectors. Ideally the metrics
> > >> handler
> > >>>>>>> has
> > >>>>>>>>> a
> > >>>>>>>>>>>>>>> single onRecord(numBytes, eventTime) method or so, and
> > >>>>> everything
> > >>>>>>>>>>>> else is
> > >>>>>>>>>>>>>>> internal to the handler. That makes it dead simple for
> the
> > >>>>>>>>> connector.
> > >>>>>>>>>>>> We
> > >>>>>>>>>>>>>>> can also think of an extensive scheme for connector
> > specific
> > >>>>>>>>> metrics.
> > >>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>> - make it configurable on the job it cluster level which
> > >>>>> metrics
> > >>>>>>> the
> > >>>>>>>>>>>>>>> handler internally creates when that method is invoked.
> > >>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>> What do you think?
> > >>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>> Best,
> > >>>>>>>>>>>>>>> Stephan
> > >>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>> On Thu, Mar 21, 2019 at 10:42 AM Chesnay Schepler <
> > >>>>>>>>> chesnay@apache.org
> > >>>>>>>>>>>>>
> > >>>>>>>>>>>>>>> wrote:
> > >>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>> As I said before, I believe this to be over-engineered
> and
> > >>>>> have
> > >>>>>>> no
> > >>>>>>>>>>>>>>>> interest in this implementation.
> > >>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>> There are conceptual issues like defining a duplicate
> > >>>>>>>>>>>>>> numBytesIn(PerSec)
> > >>>>>>>>>>>>>>>> metric that already exists for each operator.
> > >>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>> On 21.03.2019 06:13, Becket Qin wrote:
> > >>>>>>>>>>>>>>>>> A few updates to the thread. I uploaded a patch[1] as a
> > >>>>> complete
> > >>>>>>>>>>>>>>>>> example of how users can use the metrics in the future.
> > >>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>> Some thoughts below after taking a look at the
> > >>>>>>> AbstractMetricGroup
> > >>>>>>>>>>>>>> and
> > >>>>>>>>>>>>>>>>> its subclasses.
> > >>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>> This patch intends to provide convenience for Flink
> > >> connector
> > >>>>>>>>>>>>>>>>> implementations to follow metrics standards proposed in
> > >>>>> FLIP-33.
> > >>>>>>>>> It
> > >>>>>>>>>>>>>>>>> also try to enhance the metric management in general
> way
> > to
> > >>>>> help
> > >>>>>>>>>>>>>> users
> > >>>>>>>>>>>>>>>>> with:
> > >>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>> 1. metric definition
> > >>>>>>>>>>>>>>>>> 2. metric dependencies check
> > >>>>>>>>>>>>>>>>> 3. metric validation
> > >>>>>>>>>>>>>>>>> 4. metric control (turn on / off particular metrics)
> > >>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>> This patch wraps |MetricGroup| to extend the
> > functionality
> > >> of
> > >>>>>>>>>>>>>>>>> |AbstractMetricGroup| and its subclasses. The
> > >>>>>>>>>>>>>>>>> |AbstractMetricGroup| mainly focus on the metric group
> > >>>>>>> hierarchy,
> > >>>>>>>>>>>> but
> > >>>>>>>>>>>>>>>>> does not really manage the metrics other than keeping
> > them
> > >>>>> in a
> > >>>>>>>>> Map.
> > >>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>> Ideally we should only have one entry point for the
> > >> metrics.
> > >>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>> Right now the entry point is |AbstractMetricGroup|.
> > >> However,
> > >>>>>>>>> besides
> > >>>>>>>>>>>>>>>>> the missing functionality mentioned above,
> > >>>>> |AbstractMetricGroup|
> > >>>>>>>>>>>>>> seems
> > >>>>>>>>>>>>>>>>> deeply rooted in Flink runtime. We could extract it out
> > to
> > >>>>>>>>>>>>>>>>> flink-metrics in order to use it for generic purpose.
> > There
> > >>>>> will
> > >>>>>>>>> be
> > >>>>>>>>>>>>>>>>> some work, though.
> > >>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>> Another approach is to make |AbstractMetrics| in this
> > patch
> > >>>>> as
> > >>>>>>> the
> > >>>>>>>>>>>>>>>>> metric entry point. It wraps metric group and provides
> > the
> > >>>>>>> missing
> > >>>>>>>>>>>>>>>>> functionalities. Then we can roll out this pattern to
> > >> runtime
> > >>>>>>>>>>>>>>>>> components gradually as well.
> > >>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>> My first thought is that the latter approach gives a
> more
> > >>>>> smooth
> > >>>>>>>>>>>>>>>>> migration. But I am also OK with doing a refactoring on
> > the
> > >>>>>>>>>>>>>>>>> |AbstractMetricGroup| family.
> > >>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>> Thanks,
> > >>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>> Jiangjie (Becket) Qin
> > >>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>> [1] https://github.com/becketqin/flink/pull/1
> > >>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>> On Mon, Feb 25, 2019 at 2:32 PM Becket Qin <
> > >>>>>>> becket.qin@gmail.com
> > >>>>>>>>>>>>>>>>> <ma...@gmail.com>> wrote:
> > >>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>> Hi Chesnay,
> > >>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>> It might be easier to discuss some implementation
> details
> > >> in
> > >>>>>>> the
> > >>>>>>>>>>>>>>>>> PR review instead of in the FLIP discussion thread. I
> > have
> > >> a
> > >>>>>>>>>>>>>> patch
> > >>>>>>>>>>>>>>>>> for Kafka connectors ready but haven't submitted the PR
> > >> yet.
> > >>>>>>>>>>>>>>>>> Hopefully that will help explain a bit more.
> > >>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>> ** Re: metric type binding
> > >>>>>>>>>>>>>>>>> This is a valid point that worths discussing. If I
> > >> understand
> > >>>>>>>>>>>>>>>>> correctly, there are two points:
> > >>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>> 1. Metric type / interface does not matter as long as
> the
> > >>>>>>> metric
> > >>>>>>>>>>>>>>>>> semantic is clearly defined.
> > >>>>>>>>>>>>>>>>> Conceptually speaking, I agree that as long as the
> metric
> > >>>>>>>>>>>>>> semantic
> > >>>>>>>>>>>>>>>>> is defined, metric type does not matter. To some
> extent,
> > >>>>> Gauge
> > >>>>>>> /
> > >>>>>>>>>>>>>>>>> Counter / Meter / Histogram themselves can be think of
> as
> > >>>>> some
> > >>>>>>>>>>>>>>>>> well-recognized semantics, if you wish. In Flink, these
> > >>>>> metric
> > >>>>>>>>>>>>>>>>> semantics have their associated interface classes. In
> > >>>>> practice,
> > >>>>>>>>>>>>>>>>> such semantic to interface binding seems necessary for
> > >>>>>>> different
> > >>>>>>>>>>>>>>>>> components to communicate. Simply standardize the
> > semantic
> > >>>>> of
> > >>>>>>>>>>>>>> the
> > >>>>>>>>>>>>>>>>> connector metrics seems not sufficient for people to
> > build
> > >>>>>>>>>>>>>>>>> ecosystem on top of. At the end of the day, we still
> need
> > >> to
> > >>>>>>>>> have
> > >>>>>>>>>>>>>>>>> some embodiment of the metric semantics that people can
> > >>>>> program
> > >>>>>>>>>>>>>>>>> against.
> > >>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>> 2. Sometimes the same metric semantic can be exposed
> > using
> > >>>>>>>>>>>>>>>>> different metric types / interfaces.
> > >>>>>>>>>>>>>>>>> This is a good point. Counter and Gauge-as-a-Counter
> are
> > >>>>> pretty
> > >>>>>>>>>>>>>>>>> much interchangeable. This is more of a trade-off
> between
> > >> the
> > >>>>>>>>>>>>>> user
> > >>>>>>>>>>>>>>>>> experience of metric producers and consumers. The
> metric
> > >>>>>>>>>>>>>> producers
> > >>>>>>>>>>>>>>>>> want to use Counter or Gauge depending on whether the
> > >> counter
> > >>>>>>> is
> > >>>>>>>>>>>>>>>>> already tracked in code, while ideally the metric
> > consumers
> > >>>>>>> only
> > >>>>>>>>>>>>>>>>> want to see a single metric type for each metric. I am
> > >>>>> leaning
> > >>>>>>>>>>>>>>>>> towards to make the metric producers happy, i.e. allow
> > >> Gauge
> > >>>>> /
> > >>>>>>>>>>>>>>>>> Counter metric type, and the the metric consumers
> handle
> > >> the
> > >>>>>>>>> type
> > >>>>>>>>>>>>>>>>> variation. The reason is that in practice, there might
> be
> > >>>>> more
> > >>>>>>>>>>>>>>>>> connector implementations than metric reporter
> > >>>>> implementations.
> > >>>>>>>>>>>>>> We
> > >>>>>>>>>>>>>>>>> could also provide some helper method to facilitate
> > reading
> > >>>>>>> from
> > >>>>>>>>>>>>>>>>> such variable metric type.
> > >>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>> Just some quick replies to the comments around
> > >> implementation
> > >>>>>>>>>>>>>>>> details.
> > >>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>> 4) single place where metrics are registered except
> > >>>>>>>>>>>>>>>>> connector-specific
> > >>>>>>>>>>>>>>>>> ones (which we can't really avoid).
> > >>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>> Register connector specific ones in a single place is
> > >>>>> actually
> > >>>>>>>>>>>>>>>>> something that I want to achieve.
> > >>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>> 2) I'm talking about time-series databases like
> > >>>>> Prometheus.
> > >>>>>>>>>>>>>> We
> > >>>>>>>>>>>>>>>>> would
> > >>>>>>>>>>>>>>>>> only have a gauge metric exposing the last
> > >>>>>>>>> fetchTime/emitTime
> > >>>>>>>>>>>>>>>>> that is
> > >>>>>>>>>>>>>>>>> regularly reported to the backend (Prometheus),
> where a
> > >>>>>>> user
> > >>>>>>>>>>>>>>>>> could build
> > >>>>>>>>>>>>>>>>> a histogram of his choosing when/if he wants it.
> > >>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>> Not sure if such downsampling works. As an example, if
> a
> > >> user
> > >>>>>>>>>>>>>>>>> complains that there are some intermittent latency
> spikes
> > >>>>>>> (maybe
> > >>>>>>>>>>>>>> a
> > >>>>>>>>>>>>>>>>> few records in 10 seconds) in their processing system.
> > >>>>> Having a
> > >>>>>>>>>>>>>>>>> Gauge sampling instantaneous latency seems unlikely
> > useful.
> > >>>>>>>>>>>>>>>>> However by looking at actual 99.9 percentile latency
> > might
> > >>>>>>> help.
> > >>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>> Thanks,
> > >>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>> Jiangjie (Becket) Qin
> > >>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>> On Fri, Feb 22, 2019 at 9:30 PM Chesnay Schepler
> > >>>>>>>>>>>>>>>>> <chesnay@apache.org <ma...@apache.org>>
> wrote:
> > >>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>> Re: over complication of implementation.
> > >>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>> I think I get understand better know what you're
> > >> shooting
> > >>>>>>>>>>>>>> for,
> > >>>>>>>>>>>>>>>>> effectively something like the OperatorIOMetricGroup.
> > >>>>>>>>>>>>>>>>> But still, re-define setupConnectorMetrics() to
> accept
> > a
> > >>>>>>> set
> > >>>>>>>>>>>>>>>>> of flags
> > >>>>>>>>>>>>>>>>> for counters/meters(ans _possibly_ histograms) along
> > >>>>> with a
> > >>>>>>>>>>>>>>>>> set of
> > >>>>>>>>>>>>>>>>> well-defined Optional<Gauge<?>>, and return the
> group.
> > >>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>> Solves all issues as far as i can tell:
> > >>>>>>>>>>>>>>>>> 1) no metrics must be created manually (except
> Gauges,
> > >>>>>>> which
> > >>>>>>>>>>>>>>> are
> > >>>>>>>>>>>>>>>>> effectively just Suppliers and you can't get around
> > >>>>> this),
> > >>>>>>>>>>>>>>>>> 2) additional metrics can be registered on the
> returned
> > >>>>>>>>>>>>>> group,
> > >>>>>>>>>>>>>>>>> 3) see 1),
> > >>>>>>>>>>>>>>>>> 4) single place where metrics are registered except
> > >>>>>>>>>>>>>>>>> connector-specific
> > >>>>>>>>>>>>>>>>> ones (which we can't really avoid).
> > >>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>> Re: Histogram
> > >>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>> 1) As an example, whether "numRecordsIn" is exposed
> as
> > a
> > >>>>>>>>>>>>>>>>> Counter or a
> > >>>>>>>>>>>>>>>>> Gauge should be irrelevant. So far we're using the
> > >> metric
> > >>>>>>>>>>>>>> type
> > >>>>>>>>>>>>>>>>> that is
> > >>>>>>>>>>>>>>>>> the most convenient at exposing a given value. If
> there
> > >>>>> is
> > >>>>>>>>>>>>>>>>> some backing
> > >>>>>>>>>>>>>>>>> data-structure that we want to expose some data from
> we
> > >>>>>>>>>>>>>>>>> typically opt
> > >>>>>>>>>>>>>>>>> for a Gauge, as otherwise we're just mucking around
> > with
> > >>>>>>> the
> > >>>>>>>>>>>>>>>>> Meter/Counter API to get it to match. Similarly, if
> we
> > >>>>> want
> > >>>>>>>>>>>>>> to
> > >>>>>>>>>>>>>>>>> count
> > >>>>>>>>>>>>>>>>> something but no current count exists we typically
> > added
> > >>>>> a
> > >>>>>>>>>>>>>>>>> Counter.
> > >>>>>>>>>>>>>>>>> That's why attaching semantics to metric types makes
> > >>>>> little
> > >>>>>>>>>>>>>>>>> sense (but
> > >>>>>>>>>>>>>>>>> unfortunately several reporters already do it); for
> > >>>>>>>>>>>>>>>>> counters/meters
> > >>>>>>>>>>>>>>>>> certainly, but the majority of metrics are gauges.
> > >>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>> 2) I'm talking about time-series databases like
> > >>>>> Prometheus.
> > >>>>>>>>>>>>>> We
> > >>>>>>>>>>>>>>>>> would
> > >>>>>>>>>>>>>>>>> only have a gauge metric exposing the last
> > >>>>>>>>> fetchTime/emitTime
> > >>>>>>>>>>>>>>>>> that is
> > >>>>>>>>>>>>>>>>> regularly reported to the backend (Prometheus),
> where a
> > >>>>>>> user
> > >>>>>>>>>>>>>>>>> could build
> > >>>>>>>>>>>>>>>>> a histogram of his choosing when/if he wants it.
> > >>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>> On 22.02.2019 13:57, Becket Qin wrote:
> > >>>>>>>>>>>>>>>>>> Hi Chesnay,
> > >>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>> Thanks for the explanation.
> > >>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>> ** Re: FLIP
> > >>>>>>>>>>>>>>>>>> I might have misunderstood this, but it seems that
> > "major
> > >>>>>>>>>>>>>>>>> changes" are well
> > >>>>>>>>>>>>>>>>>> defined in FLIP. The full contents is following:
> > >>>>>>>>>>>>>>>>>> What is considered a "major change" that needs a FLIP?
> > >>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>> Any of the following should be considered a major
> > change:
> > >>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>> - Any major new feature, subsystem, or piece of
> > >>>>>>>>>>>>>>>>> functionality
> > >>>>>>>>>>>>>>>>>> - *Any change that impacts the public interfaces of
> the
> > >>>>>>>>>>>>>>>>> project*
> > >>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>> What are the "public interfaces" of the project?
> > >>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>> *All of the following are public interfaces *that
> people
> > >>>>>>>>>>>>>>>>> build around:
> > >>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>> - DataStream and DataSet API, including classes
> related
> > >>>>>>>>>>>>>>>>> to that, such as
> > >>>>>>>>>>>>>>>>>> StreamExecutionEnvironment
> > >>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>> - Classes marked with the @Public annotation
> > >>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>> - On-disk binary formats, such as
> > >>>>>>>>>>>>>> checkpoints/savepoints
> > >>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>> - User-facing scripts/command-line tools, i.e.
> > >>>>>>>>>>>>>>>>> bin/flink, Yarn scripts,
> > >>>>>>>>>>>>>>>>>> Mesos scripts
> > >>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>> - Configuration settings
> > >>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>> - *Exposed monitoring information*
> > >>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>> So any monitoring information change is considered as
> > >>>>>>>>>>>>>> public
> > >>>>>>>>>>>>>>>>> interface, and
> > >>>>>>>>>>>>>>>>>> any public interface change is considered as a "major
> > >>>>>>>>>>>>>>> change".
> > >>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>> ** Re: over complication of implementation.
> > >>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>> Although this is more of implementation details that
> is
> > >> not
> > >>>>>>>>>>>>>>>>> covered by the
> > >>>>>>>>>>>>>>>>>> FLIP. But it may be worth discussing.
> > >>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>> First of all, I completely agree that we should use
> the
> > >>>>>>>>>>>>>>>>> simplest way to
> > >>>>>>>>>>>>>>>>>> achieve our goal. To me the goal is the following:
> > >>>>>>>>>>>>>>>>>> 1. Clear connector conventions and interfaces.
> > >>>>>>>>>>>>>>>>>> 2. The easiness of creating a connector.
> > >>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>> Both of them are important to the prosperity of the
> > >>>>>>>>>>>>>>>>> connector ecosystem. So
> > >>>>>>>>>>>>>>>>>> I'd rather abstract as much as possible on our side to
> > >> make
> > >>>>>>>>>>>>>>>>> the connector
> > >>>>>>>>>>>>>>>>>> developer's work lighter. Given this goal, a static
> util
> > >>>>>>>>>>>>>>>>> method approach
> > >>>>>>>>>>>>>>>>>> might have a few drawbacks:
> > >>>>>>>>>>>>>>>>>> 1. Users still have to construct the metrics by
> > >> themselves.
> > >>>>>>>>>>>>>>>>> (And note that
> > >>>>>>>>>>>>>>>>>> this might be erroneous by itself. For example, a
> > customer
> > >>>>>>>>>>>>>>>>> wrapper around
> > >>>>>>>>>>>>>>>>>> dropwizard meter maybe used instead of MeterView).
> > >>>>>>>>>>>>>>>>>> 2. When connector specific metrics are added, it is
> > >>>>>>>>>>>>>>>>> difficult to enforce
> > >>>>>>>>>>>>>>>>>> the scope to be the same as standard metrics.
> > >>>>>>>>>>>>>>>>>> 3. It seems that a method proliferation is inevitable
> if
> > >> we
> > >>>>>>>>>>>>>>>>> want to apply
> > >>>>>>>>>>>>>>>>>> sanity checks. e.g. The metric of numBytesIn was not
> > >>>>>>>>>>>>>>>>> registered for a meter.
> > >>>>>>>>>>>>>>>>>> 4. Metrics are still defined in random places and hard
> > to
> > >>>>>>>>>>>>>>>> track.
> > >>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>> The current PR I had was inspired by the Config system
> > in
> > >>>>>>>>>>>>>>>>> Kafka, which I
> > >>>>>>>>>>>>>>>>>> found pretty handy. In fact it is not only used by
> Kafka
> > >>>>>>>>>>>>>>>>> itself but even
> > >>>>>>>>>>>>>>>>>> some other projects that depend on Kafka. I am not
> > saying
> > >>>>>>>>>>>>>>>>> this approach is
> > >>>>>>>>>>>>>>>>>> perfect. But I think it worths to save the work for
> > >>>>>>>>>>>>>>>>> connector writers and
> > >>>>>>>>>>>>>>>>>> encourage more systematic implementation. That being
> > said,
> > >>>>>>>>>>>>>> I
> > >>>>>>>>>>>>>>>>> am fully open
> > >>>>>>>>>>>>>>>>>> to suggestions.
> > >>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>> Re: Histogram
> > >>>>>>>>>>>>>>>>>> I think there are two orthogonal questions around
> those
> > >>>>>>>>>>>>>>>> metrics:
> > >>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>> 1. Regardless of the metric type, by just looking at
> the
> > >>>>>>>>>>>>>>>>> meaning of a
> > >>>>>>>>>>>>>>>>>> metric, is generic to all connectors? If the answer is
> > >> yes,
> > >>>>>>>>>>>>>>>>> we should
> > >>>>>>>>>>>>>>>>>> include the metric into the convention. No matter
> > whether
> > >>>>>>>>>>>>>> we
> > >>>>>>>>>>>>>>>>> include it
> > >>>>>>>>>>>>>>>>>> into the convention or not, some connector
> > implementations
> > >>>>>>>>>>>>>>>>> will emit such
> > >>>>>>>>>>>>>>>>>> metric. It is better to have a convention than letting
> > >> each
> > >>>>>>>>>>>>>>>>> connector do
> > >>>>>>>>>>>>>>>>>> random things.
> > >>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>> 2. If a standard metric is a histogram, what should we
> > do?
> > >>>>>>>>>>>>>>>>>> I agree that we should make it clear that using
> > histograms
> > >>>>>>>>>>>>>>>>> will have
> > >>>>>>>>>>>>>>>>>> performance risk. But I do see histogram is useful in
> > some
> > >>>>>>>>>>>>>>>>> fine-granularity
> > >>>>>>>>>>>>>>>>>> debugging where one do not have the luxury to stop the
> > >>>>>>>>>>>>>>>>> system and inject
> > >>>>>>>>>>>>>>>>>> more inspection code. So the workaround I am thinking
> is
> > >> to
> > >>>>>>>>>>>>>>>>> provide some
> > >>>>>>>>>>>>>>>>>> implementation suggestions. Assume later on we have a
> > >>>>>>>>>>>>>>>>> mechanism of
> > >>>>>>>>>>>>>>>>>> selective metrics. In the abstract metrics class we
> can
> > >>>>>>>>>>>>>>>>> disable those
> > >>>>>>>>>>>>>>>>>> metrics by default individual connector writers does
> not
> > >>>>>>>>>>>>>>>>> have to do
> > >>>>>>>>>>>>>>>>>> anything (this is another advantage of having an
> > >>>>>>>>>>>>>>>>> AbstractMetrics instead of
> > >>>>>>>>>>>>>>>>>> static util methods.)
> > >>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>> I am not sure I fully understand the histogram in the
> > >>>>>>>>>>>>>>>>> backend approach. Can
> > >>>>>>>>>>>>>>>>>> you explain a bit more? Do you mean emitting the raw
> > data,
> > >>>>>>>>>>>>>>>>> e.g. fetchTime
> > >>>>>>>>>>>>>>>>>> and emitTime with each record and let the histogram
> > >>>>>>>>>>>>>>>>> computation happen in
> > >>>>>>>>>>>>>>>>>> the background? Or let the processing thread putting
> the
> > >>>>>>>>>>>>>>>>> values into a
> > >>>>>>>>>>>>>>>>>> queue and have a separate thread polling from the
> queue
> > >> and
> > >>>>>>>>>>>>>>>>> add them into
> > >>>>>>>>>>>>>>>>>> the histogram?
> > >>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>> Thanks,
> > >>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>> Jiangjie (Becket) Qin
> > >>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>> On Fri, Feb 22, 2019 at 4:34 PM Chesnay Schepler
> > >>>>>>>>>>>>>>>>> <chesnay@apache.org <ma...@apache.org>>
> > wrote:
> > >>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>>> Re: Flip
> > >>>>>>>>>>>>>>>>>>> The very first line under both the main header and
> > >> Purpose
> > >>>>>>>>>>>>>>>>> section
> > >>>>>>>>>>>>>>>>>>> describe Flips as "major changes", which this isn't.
> > >>>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>>> Re: complication
> > >>>>>>>>>>>>>>>>>>> I'm not arguing against standardization, but again an
> > >>>>>>>>>>>>>>>>> over-complicated
> > >>>>>>>>>>>>>>>>>>> implementation when a static utility method would be
> > >>>>>>>>>>>>>>>>> sufficient.
> > >>>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>>> public static void setupConnectorMetrics(
> > >>>>>>>>>>>>>>>>>>> MetricGroup operatorMetricGroup,
> > >>>>>>>>>>>>>>>>>>> String connectorName,
> > >>>>>>>>>>>>>>>>>>> Optional<Gauge<Long>> numRecordsIn,
> > >>>>>>>>>>>>>>>>>>> ...)
> > >>>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>>> This gives you all you need:
> > >>>>>>>>>>>>>>>>>>> * a well-defined set of metrics for a connector to
> > opt-in
> > >>>>>>>>>>>>>>>>>>> * standardized naming schemes for scope and
> individual
> > >>>>>>>>>>>>>>> metrics
> > >>>>>>>>>>>>>>>>>>> * standardize metric types (although personally I'm
> not
> > >>>>>>>>>>>>>>>>> interested in that
> > >>>>>>>>>>>>>>>>>>> since metric types should be considered syntactic
> > sugar)
> > >>>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>>> Re: Configurable Histogram
> > >>>>>>>>>>>>>>>>>>> If anything they _must_ be turned off by default, but
> > the
> > >>>>>>>>>>>>>>>>> metric system is
> > >>>>>>>>>>>>>>>>>>> already exposing so many options that I'm not too
> keen
> > on
> > >>>>>>>>>>>>>>>>> adding even more.
> > >>>>>>>>>>>>>>>>>>> You have also only addressed my first argument
> against
> > >>>>>>>>>>>>>>>>> histograms
> > >>>>>>>>>>>>>>>>>>> (performance), the second one still stands (calculate
> > >>>>>>>>>>>>>>>>> histogram in metric
> > >>>>>>>>>>>>>>>>>>> backends instead).
> > >>>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>>> On 21.02.2019 16:27, Becket Qin wrote:
> > >>>>>>>>>>>>>>>>>>>> Hi Chesnay,
> > >>>>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>>>> Thanks for the comments. I think this is worthy of a
> > >> FLIP
> > >>>>>>>>>>>>>>>>> because it is
> > >>>>>>>>>>>>>>>>>>>> public API. According to the FLIP description a FlIP
> > is
> > >>>>>>>>>>>>>>>>> required in case
> > >>>>>>>>>>>>>>>>>>> of:
> > >>>>>>>>>>>>>>>>>>>> - Any change that impacts the public interfaces of
> > >>>>>>>>>>>>>>>>> the project
> > >>>>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>>>> and the following entry is found in the definition
> of
> > >>>>>>>>>>>>>>>>> "public interface".
> > >>>>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>>>> - Exposed monitoring information
> > >>>>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>>>> Metrics are critical to any production system. So a
> > >> clear
> > >>>>>>>>>>>>>>>>> metric
> > >>>>>>>>>>>>>>>>>>> definition
> > >>>>>>>>>>>>>>>>>>>> is important for any serious users. For an
> > organization
> > >>>>>>>>>>>>>>>>> with large Flink
> > >>>>>>>>>>>>>>>>>>>> installation, change in metrics means great amount
> of
> > >>>>>>>>>>>>>>>>> work. So such
> > >>>>>>>>>>>>>>>>>>> changes
> > >>>>>>>>>>>>>>>>>>>> do need to be fully discussed and documented.
> > >>>>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>>>> ** Re: Histogram.
> > >>>>>>>>>>>>>>>>>>>> We can discuss whether there is a better way to
> expose
> > >>>>>>>>>>>>>>>>> metrics that are
> > >>>>>>>>>>>>>>>>>>>> suitable for histograms. My micro-benchmark on
> various
> > >>>>>>>>>>>>>>>>> histogram
> > >>>>>>>>>>>>>>>>>>>> implementations also indicates that they are
> > >>>>>>>>>>>>>> significantly
> > >>>>>>>>>>>>>>>>> slower than
> > >>>>>>>>>>>>>>>>>>>> other metric types. But I don't think that means
> never
> > >>>>>>>>>>>>>> use
> > >>>>>>>>>>>>>>>>> histogram, but
> > >>>>>>>>>>>>>>>>>>>> means use it with caution. For example, we can
> suggest
> > >>>>>>>>>>>>>> the
> > >>>>>>>>>>>>>>>>>>> implementations
> > >>>>>>>>>>>>>>>>>>>> to turn them off by default and only turn it on for
> a
> > >>>>>>>>>>>>>>>>> small amount of
> > >>>>>>>>>>>>>>>>>>> time
> > >>>>>>>>>>>>>>>>>>>> when performing some micro-debugging.
> > >>>>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>>>> ** Re: complication:
> > >>>>>>>>>>>>>>>>>>>> Connector conventions are essential for Flink
> > ecosystem.
> > >>>>>>>>>>>>>>>>> Flink connectors
> > >>>>>>>>>>>>>>>>>>>> pool is probably the most important part of Flink,
> > just
> > >>>>>>>>>>>>>>>>> like any other
> > >>>>>>>>>>>>>>>>>>> data
> > >>>>>>>>>>>>>>>>>>>> system. Clear conventions of connectors will help
> > build
> > >>>>>>>>>>>>>>>>> Flink ecosystem
> > >>>>>>>>>>>>>>>>>>> in
> > >>>>>>>>>>>>>>>>>>>> a more organic way.
> > >>>>>>>>>>>>>>>>>>>> Take the metrics convention as an example, imagine
> > >>>>>>>>>>>>>> someone
> > >>>>>>>>>>>>>>>>> has developed
> > >>>>>>>>>>>>>>>>>>> a
> > >>>>>>>>>>>>>>>>>>>> Flink connector for System foo, and another
> developer
> > >> may
> > >>>>>>>>>>>>>>>>> have developed
> > >>>>>>>>>>>>>>>>>>> a
> > >>>>>>>>>>>>>>>>>>>> monitoring and diagnostic framework for Flink which
> > >>>>>>>>>>>>>>>>> analyzes the Flink
> > >>>>>>>>>>>>>>>>>>> job
> > >>>>>>>>>>>>>>>>>>>> performance based on metrics. With a clear metric
> > >>>>>>>>>>>>>>>>> convention, those two
> > >>>>>>>>>>>>>>>>>>>> projects could be developed independently. Once
> users
> > >> put
> > >>>>>>>>>>>>>>>>> them together,
> > >>>>>>>>>>>>>>>>>>>> it would work without additional modifications. This
> > >>>>>>>>>>>>>>>>> cannot be easily
> > >>>>>>>>>>>>>>>>>>>> achieved by just defining a few constants.
> > >>>>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>>>> ** Re: selective metrics:
> > >>>>>>>>>>>>>>>>>>>> Sure, we can discuss that in a separate thread.
> > >>>>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>>>> @Dawid
> > >>>>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>>>> ** Re: latency / fetchedLatency
> > >>>>>>>>>>>>>>>>>>>> The primary purpose of establish such a convention
> is
> > to
> > >>>>>>>>>>>>>>>>> help developers
> > >>>>>>>>>>>>>>>>>>>> write connectors in a more compatible way. The
> > >> convention
> > >>>>>>>>>>>>>>>>> is supposed to
> > >>>>>>>>>>>>>>>>>>> be
> > >>>>>>>>>>>>>>>>>>>> defined more proactively. So when look at the
> > >> convention,
> > >>>>>>>>>>>>>>>>> it seems more
> > >>>>>>>>>>>>>>>>>>>> important to see if the concept is applicable to
> > >>>>>>>>>>>>>>>>> connectors in general.
> > >>>>>>>>>>>>>>>>>>> It
> > >>>>>>>>>>>>>>>>>>>> might be true so far only Kafka connector reports
> > >>>>>>>>>>>>>> latency.
> > >>>>>>>>>>>>>>>>> But there
> > >>>>>>>>>>>>>>>>>>> might
> > >>>>>>>>>>>>>>>>>>>> be hundreds of other connector implementations in
> the
> > >>>>>>>>>>>>>>>>> Flink ecosystem,
> > >>>>>>>>>>>>>>>>>>>> though not in the Flink repo, and some of them also
> > >> emits
> > >>>>>>>>>>>>>>>>> latency. I
> > >>>>>>>>>>>>>>>>>>> think
> > >>>>>>>>>>>>>>>>>>>> a lot of other sources actually also has an append
> > >>>>>>>>>>>>>>>>> timestamp. e.g.
> > >>>>>>>>>>>>>>>>>>> database
> > >>>>>>>>>>>>>>>>>>>> bin logs and some K-V stores. So I wouldn't be
> > surprised
> > >>>>>>>>>>>>>>>>> if some database
> > >>>>>>>>>>>>>>>>>>>> connector can also emit latency metrics.
> > >>>>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>>>> Thanks,
> > >>>>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>>>> Jiangjie (Becket) Qin
> > >>>>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>>>> On Thu, Feb 21, 2019 at 10:14 PM Chesnay Schepler
> > >>>>>>>>>>>>>>>>> <chesnay@apache.org <ma...@apache.org>>
> > >>>>>>>>>>>>>>>>>>>> wrote:
> > >>>>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>>>>> Regarding 2) It doesn't make sense to investigate
> > this
> > >>>>>>>>>>>>>> as
> > >>>>>>>>>>>>>>>>> part of this
> > >>>>>>>>>>>>>>>>>>>>> FLIP. This is something that could be of interest
> for
> > >>>>>>>>>>>>>> the
> > >>>>>>>>>>>>>>>>> entire metric
> > >>>>>>>>>>>>>>>>>>>>> system, and should be designed for as such.
> > >>>>>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>>>>> Regarding the proposal as a whole:
> > >>>>>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>>>>> Histogram metrics shall not be added to the core of
> > >>>>>>>>>>>>>>>>> Flink. They are
> > >>>>>>>>>>>>>>>>>>>>> significantly more expensive than other metrics,
> and
> > >>>>>>>>>>>>>>>>> calculating
> > >>>>>>>>>>>>>>>>>>>>> histograms in the application is regarded as an
> > >>>>>>>>>>>>>>>>> anti-pattern by several
> > >>>>>>>>>>>>>>>>>>>>> metric backends, who instead recommend to expose
> the
> > >> raw
> > >>>>>>>>>>>>>>>>> data and
> > >>>>>>>>>>>>>>>>>>>>> calculate the histogram in the backend.
> > >>>>>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>>>>> Second, this seems overly complicated. Given that
> we
> > >>>>>>>>>>>>>>>>> already established
> > >>>>>>>>>>>>>>>>>>>>> that not all connectors will export all metrics we
> > are
> > >>>>>>>>>>>>>>>>> effectively
> > >>>>>>>>>>>>>>>>>>>>> reducing this down to a consistent naming scheme.
> We
> > >>>>>>>>>>>>>>>>> don't need anything
> > >>>>>>>>>>>>>>>>>>>>> sophisticated for that; basically just a few
> > constants
> > >>>>>>>>>>>>>>>>> that all
> > >>>>>>>>>>>>>>>>>>>>> connectors use.
> > >>>>>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>>>>> I'm not convinced that this is worthy of a FLIP.
> > >>>>>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>>>>> On 21.02.2019 14:26, Dawid Wysakowicz wrote:
> > >>>>>>>>>>>>>>>>>>>>>> Hi,
> > >>>>>>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>>>>>> Ad 1. In general I undestand and I agree. But
> those
> > >>>>>>>>>>>>>>>>> particular metrics
> > >>>>>>>>>>>>>>>>>>>>>> (latency, fetchLatency), right now would only be
> > >>>>>>>>>>>>>>>>> reported if user uses
> > >>>>>>>>>>>>>>>>>>>>>> KafkaConsumer with internal timestampAssigner with
> > >>>>>>>>>>>>>>>>> StreamCharacteristic
> > >>>>>>>>>>>>>>>>>>>>>> set to EventTime, right? That sounds like a very
> > >>>>>>>>>>>>>>>>> specific case. I am
> > >>>>>>>>>>>>>>>>>>> not
> > >>>>>>>>>>>>>>>>>>>>>> sure if we should introduce a generic metric that
> > will
> > >>>>>>>>>>>>>> be
> > >>>>>>>>>>>>>>>>>>>>>> disabled/absent for most of implementations.
> > >>>>>>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>>>>>> Ad.2 That sounds like an orthogonal issue, that
> > might
> > >>>>>>>>>>>>>>>>> make sense to
> > >>>>>>>>>>>>>>>>>>>>>> investigate in the future.
> > >>>>>>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>>>>>> Best,
> > >>>>>>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>>>>>> Dawid
> > >>>>>>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>>>>>> On 21/02/2019 13:20, Becket Qin wrote:
> > >>>>>>>>>>>>>>>>>>>>>>> Hi Dawid,
> > >>>>>>>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>>>>>>> Thanks for the feedback. That makes sense to me.
> > >> There
> > >>>>>>>>>>>>>>>>> are two cases
> > >>>>>>>>>>>>>>>>>>> to
> > >>>>>>>>>>>>>>>>>>>>> be
> > >>>>>>>>>>>>>>>>>>>>>>> addressed.
> > >>>>>>>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>>>>>>> 1. The metrics are supposed to be a guidance. It
> is
> > >>>>>>>>>>>>>>>>> likely that a
> > >>>>>>>>>>>>>>>>>>>>> connector
> > >>>>>>>>>>>>>>>>>>>>>>> only supports some but not all of the metrics. In
> > >> that
> > >>>>>>>>>>>>>>>>> case, each
> > >>>>>>>>>>>>>>>>>>>>> connector
> > >>>>>>>>>>>>>>>>>>>>>>> implementation should have the freedom to decide
> > >> which
> > >>>>>>>>>>>>>>>>> metrics are
> > >>>>>>>>>>>>>>>>>>>>>>> reported. For the metrics that are supported, the
> > >>>>>>>>>>>>>>>>> guidance should be
> > >>>>>>>>>>>>>>>>>>>>>>> followed.
> > >>>>>>>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>>>>>>> 2. Sometimes users may want to disable certain
> > >> metrics
> > >>>>>>>>>>>>>>>>> for some reason
> > >>>>>>>>>>>>>>>>>>>>>>> (e.g. performance / reprocessing of data). A
> > generic
> > >>>>>>>>>>>>>>>>> mechanism should
> > >>>>>>>>>>>>>>>>>>> be
> > >>>>>>>>>>>>>>>>>>>>>>> provided to allow user choose which metrics are
> > >>>>>>>>>>>>>>>>> reported. This
> > >>>>>>>>>>>>>>>>>>> mechanism
> > >>>>>>>>>>>>>>>>>>>>>>> should also be honored by the connector
> > >>>>>>>>>>>>>> implementations.
> > >>>>>>>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>>>>>>> Does this sound reasonable to you?
> > >>>>>>>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>>>>>>> Thanks,
> > >>>>>>>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>>>>>>> Jiangjie (Becket) Qin
> > >>>>>>>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>>>>>>> On Thu, Feb 21, 2019 at 4:22 PM Dawid Wysakowicz
> <
> > >>>>>>>>>>>>>>>>>>>>> dwysakowicz@apache.org <mailto:
> > dwysakowicz@apache.org
> > >>>>
> > >>>>>>>>>>>>>>>>>>>>>>> wrote:
> > >>>>>>>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>>>>>>>> Hi,
> > >>>>>>>>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>>>>>>>> Generally I like the idea of having a unified,
> > >>>>>>>>>>>>>>>>> standard set of
> > >>>>>>>>>>>>>>>>>>> metrics
> > >>>>>>>>>>>>>>>>>>>>> for
> > >>>>>>>>>>>>>>>>>>>>>>>> all connectors. I have some slight concerns
> about
> > >>>>>>>>>>>>>>>>> fetchLatency and
> > >>>>>>>>>>>>>>>>>>>>>>>> latency though. They are computed based on
> > EventTime
> > >>>>>>>>>>>>>>>>> which is not a
> > >>>>>>>>>>>>>>>>>>>>> purely
> > >>>>>>>>>>>>>>>>>>>>>>>> technical feature. It depends often on some
> > business
> > >>>>>>>>>>>>>>>>> logic, might be
> > >>>>>>>>>>>>>>>>>>>>> absent
> > >>>>>>>>>>>>>>>>>>>>>>>> or defined after source. Those metrics could
> also
> > >>>>>>>>>>>>>>>>> behave in a weird
> > >>>>>>>>>>>>>>>>>>>>> way in
> > >>>>>>>>>>>>>>>>>>>>>>>> case of replaying backlog. Therefore I am not
> sure
> > >> if
> > >>>>>>>>>>>>>>>>> we should
> > >>>>>>>>>>>>>>>>>>> include
> > >>>>>>>>>>>>>>>>>>>>>>>> those metrics by default. Maybe we could at
> least
> > >>>>>>>>>>>>>>>>> introduce a feature
> > >>>>>>>>>>>>>>>>>>>>>>>> switch for them? What do you think?
> > >>>>>>>>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>>>>>>>> Best,
> > >>>>>>>>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>>>>>>>> Dawid
> > >>>>>>>>>>>>>>>>>>>>>>>> On 21/02/2019 03:13, Becket Qin wrote:
> > >>>>>>>>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>>>>>>>> Bump. If there is no objections to the proposed
> > >>>>>>>>>>>>>>>>> metrics. I'll start a
> > >>>>>>>>>>>>>>>>>>>>>>>> voting thread later toady.
> > >>>>>>>>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>>>>>>>> Thanks,
> > >>>>>>>>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>>>>>>>> Jiangjie (Becket) Qin
> > >>>>>>>>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>>>>>>>> On Mon, Feb 11, 2019 at 8:17 PM Becket Qin
> > >>>>>>>>>>>>>>>>> <becket.qin@gmail.com <ma...@gmail.com>>
> <
> > >>>>>>>>>>>>>>>>>>>>> becket.qin@gmail.com <mailto:becket.qin@gmail.com
> >>
> > >>>>>>>>>>>>>>> wrote:
> > >>>>>>>>>>>>>>>>>>>>>>>> Hi folks,
> > >>>>>>>>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>>>>>>>> I would like to start the FLIP discussion thread
> > >>>>>>>>>>>>>> about
> > >>>>>>>>>>>>>>>>> standardize
> > >>>>>>>>>>>>>>>>>>> the
> > >>>>>>>>>>>>>>>>>>>>>>>> connector metrics.
> > >>>>>>>>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>>>>>>>> In short, we would like to provide a convention
> of
> > >>>>>>>>>>>>>>>>> Flink connector
> > >>>>>>>>>>>>>>>>>>>>>>>> metrics. It will help simplify the monitoring
> and
> > >>>>>>>>>>>>>>>>> alerting on Flink
> > >>>>>>>>>>>>>>>>>>>>> jobs.
> > >>>>>>>>>>>>>>>>>>>>>>>> The FLIP link is following:
> > >>>>>>>>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>
> > >>>>>>>>>>>>
> > >>>>>>>>>
> > >>>>>>>
> > >>>>>
> > >>
> >
> https://cwiki.apache.org/confluence/display/FLINK/FLIP-33%3A+Standardize+Connector+Metrics
> > >>>>>>>>>>>>>>>>>>>>>>>> Thanks,
> > >>>>>>>>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>>>>>>>> Jiangjie (Becket) Qin
> > >>>>>>>>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>
> > >>>>>>>>>>>>
> > >>>>>>>>>>>>
> > >>>>>>>>>
> > >>>>>>>>>
> > >>>>>>>>>
> > >>>>>>>
> > >>>>>>>
> > >>>>>>>
> > >>>>>
> > >>>>>
> > >>
> > >>
> >
> >
>
--
Konstantin Knauf
https://twitter.com/snntrable
https://github.com/knaufk
Re: [DISCUSS] FLIP-33: Standardize connector metrics
Posted by Becket Qin <be...@gmail.com>.
Hi all,
To complete the Source refactoring work, I'd like to revive this
discussion. Since the mail thread has been dormant for more than a year,
just to recap the motivation of the FLIP:
1. The FLIP proposes to standardize the connector metrics by giving
guidance on the metric specifications, including the name, type and meaning
of the metrics.
2. It is OK for a connector to not emit some of the metrics in the metric
guidance, but if a metric of the same semantic is emitted, the
implementation should follow the guidance.
3. It is OK for a connector to emit more metrics than what are listed in
the FLIP. This includes having an alias for a metric specified in the FLIP.
4. We will implement some of the metrics out of the box in the default
implementation of FLIP-27, as long as it is applicable.
The FLIP wiki is following:
https://cwiki.apache.org/confluence/display/FLINK/FLIP-33
%3A+Standardize+Connector+Metrics
Any thoughts?
Thanks,
Jiangjie (Becket) Qin
On Fri, Jun 14, 2019 at 2:29 PM Piotr Nowojski <pi...@ververica.com> wrote:
> > we will need to revisit the convention list and adjust them accordingly
> when FLIP-27 is ready
>
>
> Yes, this sounds good :)
>
> Piotrek
>
> > On 13 Jun 2019, at 13:35, Becket Qin <be...@gmail.com> wrote:
> >
> > Hi Piotr,
> >
> > That's great to know. Chances are that we will need to revisit the
> > convention list and adjust them accordingly when FLIP-27 is ready, At
> that
> > point we can mark some of the metrics as available by default for
> > connectors implementing the new interface.
> >
> > Thanks,
> >
> > Jiangjie (Becket) Qin
> >
> > On Thu, Jun 13, 2019 at 3:51 PM Piotr Nowojski <pi...@ververica.com>
> wrote:
> >
> >> Thanks for driving this. I’ve just noticed one small thing. With new
> >> SourceReader interface Flink will be able to provide `idleTime` metric
> >> automatically.
> >>
> >> Piotrek
> >>
> >>> On 13 Jun 2019, at 03:30, Becket Qin <be...@gmail.com> wrote:
> >>>
> >>> Thanks all for the feedback and discussion.
> >>>
> >>> Since there wasn't any concern raised, I've started the voting thread
> for
> >>> this FLIP, but please feel free to continue the discussion here if you
> >>> think something still needs to be addressed.
> >>>
> >>> Thanks,
> >>>
> >>> Jiangjie (Becket) Qin
> >>>
> >>>
> >>>
> >>> On Mon, Jun 10, 2019 at 9:10 AM Becket Qin <be...@gmail.com>
> wrote:
> >>>
> >>>> Hi Piotr,
> >>>>
> >>>> Thanks for the comments. Yes, you are right. Users will have to look
> at
> >>>> other metrics to decide whether the pipeline is healthy or not in the
> >> first
> >>>> place before they can use the time-based metric to fix the bottleneck.
> >>>>
> >>>> I agree that once we have FLIP-27 ready, some of the metrics can just
> be
> >>>> reported by the abstract implementation.
> >>>>
> >>>> I've updated FLIP-33 wiki page to add the pendingBytes and
> >> pendingRecords
> >>>> metric. Please let me know if you have any concern over the updated
> >> metric
> >>>> convention proposal.
> >>>>
> >>>> @Chesnay Schepler <ch...@apache.org> @Stephan Ewen
> >>>> <st...@ververica.com> will you also have time to take a look at the
> >>>> proposed metric convention? If there is no further concern I'll start
> a
> >>>> voting thread for this FLIP in two days.
> >>>>
> >>>> Thanks,
> >>>>
> >>>> Jiangjie (Becket) Qin
> >>>>
> >>>>
> >>>>
> >>>> On Wed, Jun 5, 2019 at 6:54 PM Piotr Nowojski <pi...@ververica.com>
> >> wrote:
> >>>>
> >>>>> Hi Becket,
> >>>>>
> >>>>> Thanks for the answer :)
> >>>>>
> >>>>>> By time-based metric, I meant the portion of time spent on producing
> >> the
> >>>>>> record to downstream. For example, a source connector can report
> that
> >>>>> it's
> >>>>>> spending 80% of time to emit record to downstream processing
> pipeline.
> >>>>> In
> >>>>>> another case, a sink connector may report that its spending 30% of
> >> time
> >>>>>> producing the records to the external system.
> >>>>>>
> >>>>>> This is in some sense equivalent to the buffer usage metric:
> >>>>>
> >>>>>> - 80% of time spent on emitting records to downstream --->
> downstream
> >>>>>> node is bottleneck ---> output buffer is probably full.
> >>>>>> - 30% of time spent on emitting records to downstream --->
> downstream
> >>>>>> node is not bottleneck ---> output buffer is probably not full.
> >>>>>
> >>>>> If by “time spent on emitting records to downstream” you understand
> >>>>> “waiting on back pressure”, then I see your point. And I agree that
> >> some
> >>>>> kind of ratio/time based metric gives you more information. However
> >> under
> >>>>> “time spent on emitting records to downstream” might be hidden the
> >>>>> following (extreme) situation:
> >>>>>
> >>>>> 1. Job is barely able to handle influx of records, there is 99%
> >>>>> CPU/resource usage in the cluster, but nobody is
> >>>>> bottlenecked/backpressured, all output buffers are empty, everybody
> is
> >>>>> waiting in 1% of it’s time for more records to process.
> >>>>> 2. 80% time can still be spent on "down stream operators”, because
> they
> >>>>> are the CPU intensive operations, but this doesn’t mean that
> >> increasing the
> >>>>> parallelism down the stream will help with anything there. To the
> >> contrary,
> >>>>> increasing parallelism of the source operator might help to increase
> >>>>> resource utilisation up to 100%.
> >>>>>
> >>>>> However, this “time based/ratio” approach can be extended to
> in/output
> >>>>> buffer usage. Besides collecting an information that input/output
> >> buffer is
> >>>>> full/empty, we can probe profile how often are buffer empty/full. If
> >> output
> >>>>> buffer is full 1% of times, there is almost no back pressure. If it’s
> >> full
> >>>>> 80% of times, there is some back pressure, if it’s full 99.9% of
> times,
> >>>>> there is huge back pressure.
> >>>>>
> >>>>> Now for autoscaling you could compare the input & output buffers fill
> >>>>> ratio:
> >>>>>
> >>>>> 1. Both are high, the source of bottleneck is down the stream
> >>>>> 2. Output is low, input is high, this is the bottleneck and the
> higher
> >>>>> the difference, the bigger source of bottleneck is this is
> >> operator/task
> >>>>> 3. Output is high, input is low - there was some load spike that we
> are
> >>>>> currently finishing to process
> >>>>>
> >>>>>
> >>>>>
> >>>>> But long story short, we are probably diverging from the topic of
> this
> >>>>> discussion, and we can discuss this at some later point.
> >>>>>
> >>>>> For now, for sources:
> >>>>>
> >>>>> as I wrote before, +1 for:
> >>>>> - pending.bytes, Gauge
> >>>>> - pending.messages, Gauge
> >>>>>
> >>>>> When we will be developing/discussing SourceReader from FLIP-27 we
> >> might
> >>>>> then add:
> >>>>>
> >>>>> - in-memory.buffer.usage (0 - 100%)
> >>>>>
> >>>>> Which will be estimated automatically by Flink while user will be
> able
> >> to
> >>>>> override/provide better estimation.
> >>>>>
> >>>>> Piotrek
> >>>>>
> >>>>>> On 5 Jun 2019, at 05:42, Becket Qin <be...@gmail.com> wrote:
> >>>>>>
> >>>>>> Hi Piotr,
> >>>>>>
> >>>>>> Thanks for the explanation. Please see some clarifications below.
> >>>>>>
> >>>>>> By time-based metric, I meant the portion of time spent on producing
> >> the
> >>>>>> record to downstream. For example, a source connector can report
> that
> >>>>> it's
> >>>>>> spending 80% of time to emit record to downstream processing
> pipeline.
> >>>>> In
> >>>>>> another case, a sink connector may report that its spending 30% of
> >> time
> >>>>>> producing the records to the external system.
> >>>>>>
> >>>>>> This is in some sense equivalent to the buffer usage metric:
> >>>>>> - 80% of time spent on emitting records to downstream --->
> downstream
> >>>>>> node is bottleneck ---> output buffer is probably full.
> >>>>>> - 30% of time spent on emitting records to downstream --->
> downstream
> >>>>>> node is not bottleneck ---> output buffer is probably not full.
> >>>>>>
> >>>>>> However, the time-based metric has a few advantages that the buffer
> >>>>> usage
> >>>>>> metric may not have.
> >>>>>>
> >>>>>> 1. Buffer usage metric may not be applicable to all the connector
> >>>>>> implementations, while reporting time-based metric are always
> doable.
> >>>>>> Some source connectors may not have any input buffer, or they may
> use
> >>>>> some
> >>>>>> third party library that does not expose the input buffer at all.
> >>>>>> Similarly, for sink connectors, the implementation may not have any
> >>>>> output
> >>>>>> buffer, or the third party library does not expose such buffer.
> >>>>>>
> >>>>>> 2. Although both type of metrics can detect bottleneck, time-based
> >>>>> metrics
> >>>>>> can be used to generate a more informed action to remove the
> >> bottleneck.
> >>>>>> For example, when the downstream is bottleneck, the output buffer
> >> usage
> >>>>>> metric is likely to be 100%, and the input buffer usage might be 0%.
> >>>>> That
> >>>>>> means we don't know what is the suitable parallelism to lift the
> >>>>>> bottleneck. The time-based metric, on the other hand, would give
> >> useful
> >>>>>> information, e.g. if 80% of time was spent on emitting records, we
> can
> >>>>>> roughly increase the downstream node parallelism by 4 times.
> >>>>>>
> >>>>>> Admittedly, the time-based metrics are more expensive than buffer
> >>>>> usage. So
> >>>>>> we may have to do some sampling to reduce the cost. But in general,
> >>>>> using
> >>>>>> time-based metrics seems worth adding.
> >>>>>>
> >>>>>> That being said, I don't think buffer usage metric and time-based
> >>>>> metrics
> >>>>>> are mutually exclusive. We can probably have both. It is just that
> in
> >>>>>> practice, features like auto-scaling might prefer time-based metrics
> >> for
> >>>>>> the reason stated above.
> >>>>>>
> >>>>>>> 1. Define the metrics that would allow us to manually detect
> >>>>> bottlenecks.
> >>>>>> As I wrote, we already have them in most of the places, except of
> >>>>>> sources/sinks.
> >>>>>>> 2. Use those metrics, to automatically detect bottlenecks.
> Currently
> >> we
> >>>>>> are only automatically detecting back pressure and reporting it to
> the
> >>>>> user
> >>>>>> in web UI (is it exposed as a metric at all?). Detecting the root
> >> cause
> >>>>> of
> >>>>>> the back pressure (bottleneck) is one step further.
> >>>>>>> 3. Use the knowledge about where exactly the bottleneck is located,
> >> to
> >>>>>> try to do something with it.
> >>>>>>
> >>>>>> As explained above, I think time-based metric also addresses item 1
> >> and
> >>>>>> item 2.
> >>>>>>
> >>>>>> Any thoughts？
> >>>>>>
> >>>>>> Thanks,
> >>>>>>
> >>>>>> Jiangjie (Becket) Qin
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>>> On Mon, Jun 3, 2019 at 4:14 PM Piotr Nowojski <pi...@ververica.com>
> >>>>> wrote:
> >>>>>>
> >>>>>>> Hi again :)
> >>>>>>>
> >>>>>>>> - pending.bytes, Gauge
> >>>>>>>> - pending.messages, Gauge
> >>>>>>>
> >>>>>>>
> >>>>>>> +1
> >>>>>>>
> >>>>>>> And true, instead of overloading one of the metric it is better
> when
> >>>>> user
> >>>>>>> can choose to provide only one of them.
> >>>>>>>
> >>>>>>> Re 2:
> >>>>>>>
> >>>>>>>> If I understand correctly, this metric along with the pending
> >> mesages
> >>>>> /
> >>>>>>>> bytes would answer the questions of:
> >>>>>>>
> >>>>>>>> - Does the connector consume fast enough? Lagging behind + empty
> >>>>> buffer
> >>>>>>> =
> >>>>>>>> cannot consume fast enough.
> >>>>>>>> - Does the connector emit fast enough? Lagging behind + full
> buffer
> >> =
> >>>>>>>> cannot emit fast enough, i.e. the Flink pipeline is slow.
> >>>>>>>
> >>>>>>> Yes, exactly. This can also be used to support decisions like
> >> changing
> >>>>> the
> >>>>>>> parallelism of the sources and/or down stream operators.
> >>>>>>>
> >>>>>>> I’m not sure if I understand your proposal with time based
> >>>>> measurements.
> >>>>>>> Maybe I’m missing something, but I do not see how measuring time
> >> alone
> >>>>>>> could answer the problem: where is the bottleneck. Time spent on
> the
> >>>>>>> next/emit might be short or long (depending on how heavy to process
> >> the
> >>>>>>> record is) and the source can still be bottlenecked/back pressured
> or
> >>>>> not.
> >>>>>>> Usually the easiest and the most reliable way how to detect
> >>>>> bottlenecks is
> >>>>>>> by checking usage of input & output buffers, since when input
> buffer
> >> is
> >>>>>>> full while output buffer is empty, that’s the definition of a
> >>>>> bottleneck.
> >>>>>>> Also this is usually very easy and cheap to measure (it works
> >>>>> effectively
> >>>>>>> the same way as current’s Flink back pressure monitoring, but more
> >>>>> cleanly,
> >>>>>>> without probing thread’s stack traces).
> >>>>>>>
> >>>>>>> Also keep in mind that we are already using the buffer usage
> metrics
> >>>>> for
> >>>>>>> detecting the bottlenecks in Flink’s internal network exchanges
> >> (manual
> >>>>>>> work). That’s the reason why I wanted to extend this to
> >> sources/sinks,
> >>>>>>> since they are currently our blind spot.
> >>>>>>>
> >>>>>>>> One feature we are currently working on to scale Flink
> automatically
> >>>>>>> relies
> >>>>>>>> on some metrics answering the same question
> >>>>>>>
> >>>>>>> That would be very helpful feature. I think in order to achieve
> that
> >> we
> >>>>>>> would need to:
> >>>>>>> 1. Define the metrics that would allow us to manually detect
> >>>>> bottlenecks.
> >>>>>>> As I wrote, we already have them in most of the places, except of
> >>>>>>> sources/sinks.
> >>>>>>> 2. Use those metrics, to automatically detect bottlenecks.
> Currently
> >> we
> >>>>>>> are only automatically detecting back pressure and reporting it to
> >> the
> >>>>> user
> >>>>>>> in web UI (is it exposed as a metric at all?). Detecting the root
> >>>>> cause of
> >>>>>>> the back pressure (bottleneck) is one step further.
> >>>>>>> 3. Use the knowledge about where exactly the bottleneck is located,
> >> to
> >>>>> try
> >>>>>>> to do something with it.
> >>>>>>>
> >>>>>>> I think you are aiming for point 3., but before we reach it, we are
> >>>>> still
> >>>>>>> missing 1. & 2. Also even if we have 3., there is a value in 1 & 2
> >> for
> >>>>>>> manual analysis/dashboards.
> >>>>>>>
> >>>>>>> However, having the knowledge of where the bottleneck is, doesn’t
> >>>>>>> necessarily mean that we know what we can do about it. For example
> >>>>>>> increasing parallelism might or might not help with anything (data
> >>>>> skew,
> >>>>>>> bottleneck on some resource that does not scale), but this remark
> >>>>> applies
> >>>>>>> always, regardless of the way how did we detect the bottleneck.
> >>>>>>>
> >>>>>>> Piotrek
> >>>>>>>
> >>>>>>>> On 3 Jun 2019, at 06:16, Becket Qin <be...@gmail.com> wrote:
> >>>>>>>>
> >>>>>>>> Hi Piotr,
> >>>>>>>>
> >>>>>>>> Thanks for the suggestion. Some thoughts below:
> >>>>>>>>
> >>>>>>>> Re 1: The pending messages / bytes.
> >>>>>>>> I completely agree these are very useful metrics and we should
> >> expect
> >>>>> the
> >>>>>>>> connector to report. WRT the way to expose them, it seems more
> >>>>> consistent
> >>>>>>>> to add two metrics instead of adding a method (unless there are
> >> other
> >>>>> use
> >>>>>>>> cases other than metric reporting). So we can add the following
> two
> >>>>>>> metrics.
> >>>>>>>> - pending.bytes, Gauge
> >>>>>>>> - pending.messages, Gauge
> >>>>>>>> Applicable connectors can choose to report them. These two metrics
> >>>>> along
> >>>>>>>> with latency should be sufficient for users to understand the
> >> progress
> >>>>>>> of a
> >>>>>>>> connector.
> >>>>>>>>
> >>>>>>>>
> >>>>>>>> Re 2: Number of buffered data in-memory of the connector
> >>>>>>>> If I understand correctly, this metric along with the pending
> >> mesages
> >>>>> /
> >>>>>>>> bytes would answer the questions of:
> >>>>>>>> - Does the connector consume fast enough? Lagging behind + empty
> >>>>> buffer
> >>>>>>> =
> >>>>>>>> cannot consume fast enough.
> >>>>>>>> - Does the connector emit fast enough? Lagging behind + full
> buffer
> >> =
> >>>>>>>> cannot emit fast enough, i.e. the Flink pipeline is slow.
> >>>>>>>>
> >>>>>>>> One feature we are currently working on to scale Flink
> automatically
> >>>>>>> relies
> >>>>>>>> on some metrics answering the same question, more specifically, we
> >> are
> >>>>>>>> profiling the time spent on .next() method (time to consume) and
> the
> >>>>> time
> >>>>>>>> spent on .collect() method (time to emit / process). One advantage
> >> of
> >>>>>>> such
> >>>>>>>> method level time cost allows us to calculate the parallelism
> >>>>> required to
> >>>>>>>> keep up in case their is a lag.
> >>>>>>>>
> >>>>>>>> However, one concern I have regarding such metric is that they are
> >>>>>>>> implementation specific. Either profiling on the method time, or
> >>>>>>> reporting
> >>>>>>>> buffer usage assumes the connector are implemented in such a way.
> A
> >>>>>>>> slightly better solution might be have the following metric:
> >>>>>>>>
> >>>>>>>> - EmitTimeRatio (or FetchTimeRatio): The time spent on emitting
> >>>>>>>> records / Total time elapsed.
> >>>>>>>>
> >>>>>>>> This assumes that the source connectors have to emit the records
> to
> >>>>> the
> >>>>>>>> downstream at some point. The emission may take some time ( e.g.
> go
> >>>>>>> through
> >>>>>>>> chained operators). And the rest of the time are spent to prepare
> >> the
> >>>>>>>> record to emit, including time for consuming and format
> conversion,
> >>>>> etc.
> >>>>>>>> Ideally, we'd like to see the time spent on record fetch and emit
> to
> >>>>> be
> >>>>>>>> about the same, so no one is bottleneck for the other.
> >>>>>>>>
> >>>>>>>> The downside of these time based metrics is additional overhead to
> >> get
> >>>>>>> the
> >>>>>>>> time, therefore sampling might be needed. But in practice I feel
> >> such
> >>>>>>> time
> >>>>>>>> based metric might be more useful if we want to take action.
> >>>>>>>>
> >>>>>>>>
> >>>>>>>> I think we should absolutely add metrics in (1) to the metric
> >>>>> convention.
> >>>>>>>> We could also add the metrics mentioned in (2) if we reach
> consensus
> >>>>> on
> >>>>>>>> that. What do you think?
> >>>>>>>>
> >>>>>>>> Thanks,
> >>>>>>>>
> >>>>>>>> Jiangjie (Becket) Qin
> >>>>>>>>
> >>>>>>>>
> >>>>>>>> On Fri, May 31, 2019 at 4:26 PM Piotr Nowojski <
> piotr@ververica.com
> >>>
> >>>>>>> wrote:
> >>>>>>>>
> >>>>>>>>> Hey Becket,
> >>>>>>>>>
> >>>>>>>>> Re 1a) and 1b) +1 from my side.
> >>>>>>>>>
> >>>>>>>>> I’ve discussed this issue:
> >>>>>>>>>
> >>>>>>>>>>>>
> >>>>>>>>>>>> 2. It would be nice to have metrics, that allow us to check
> the
> >>>>> cause
> >>>>>>>>> of
> >>>>>>>>>>>> back pressure:
> >>>>>>>>>>>> a) for sources, length of input queue (in bytes? Or boolean
> >>>>>>>>>>>> hasSomethingl/isEmpty)
> >>>>>>>>>>>> b) for sinks, length of output queue (in bytes? Or boolean
> >>>>>>>>>>>> hasSomething/isEmpty)
> >>>>>>>>>
> >>>>>>>>> With Nico at some lengths and he also saw the benefits of them.
> We
> >>>>> also
> >>>>>>>>> have more concrete proposal for that.
> >>>>>>>>>
> >>>>>>>>> Actually there are two really useful metrics, that we are missing
> >>>>>>>>> currently:
> >>>>>>>>>
> >>>>>>>>> 1. Number of data/records/bytes in the backlog to process. For
> >>>>> example
> >>>>>>>>> remaining number of bytes in unread files. Or pending data in
> Kafka
> >>>>>>> topics.
> >>>>>>>>> 2. Number of buffered data in-memory of the connector, that are
> >>>>> waiting
> >>>>>>> to
> >>>>>>>>> be processed pushed to Flink pipeline.
> >>>>>>>>>
> >>>>>>>>> Re 1:
> >>>>>>>>> This would have to be a metric provided directly by a connector.
> It
> >>>>>>> could
> >>>>>>>>> be an undefined `int`:
> >>>>>>>>>
> >>>>>>>>> `int backlog` - estimate of pending work.
> >>>>>>>>>
> >>>>>>>>> “Undefined” meaning that it would be up to a connector to decided
> >>>>>>> whether
> >>>>>>>>> it’s measured in bytes, records, pending files or whatever it is
> >>>>>>> possible
> >>>>>>>>> to provide by the connector. This is because I assume not every
> >>>>>>> connector
> >>>>>>>>> can provide exact number and for some of them it might be
> >> impossible
> >>>>> to
> >>>>>>>>> provide records number of bytes count.
> >>>>>>>>>
> >>>>>>>>> Re 2:
> >>>>>>>>> This metric could be either provided by a connector, or
> calculated
> >>>>>>> crudely
> >>>>>>>>> by Flink:
> >>>>>>>>>
> >>>>>>>>> `float bufferUsage` - value from [0.0, 1.0] range
> >>>>>>>>>
> >>>>>>>>> Percentage of used in memory buffers, like in Kafka’s handover.
> >>>>>>>>>
> >>>>>>>>> It could be crudely implemented by Flink with FLIP-27
> >>>>>>>>> SourceReader#isAvailable. If SourceReader is not available
> reported
> >>>>>>>>> `bufferUsage` could be 0.0. If it is available, it could be 1.0.
> I
> >>>>> think
> >>>>>>>>> this would be a good enough estimation for most of the use cases
> >>>>> (that
> >>>>>>>>> could be overloaded and implemented better if desired).
> Especially
> >>>>>>> since we
> >>>>>>>>> are reporting only probed values: if probed values are almost
> >> always
> >>>>>>> “1.0”,
> >>>>>>>>> it would mean that we have a back pressure. If they are almost
> >> always
> >>>>>>>>> “0.0”, there is probably no back pressure at the sources.
> >>>>>>>>>
> >>>>>>>>> What do you think about this?
> >>>>>>>>>
> >>>>>>>>> Piotrek
> >>>>>>>>>
> >>>>>>>>>> On 30 May 2019, at 11:41, Becket Qin <be...@gmail.com>
> >> wrote:
> >>>>>>>>>>
> >>>>>>>>>> Hi all,
> >>>>>>>>>>
> >>>>>>>>>> Thanks a lot for all the feedback and comments. I'd like to
> >> continue
> >>>>>>> the
> >>>>>>>>>> discussion on this FLIP.
> >>>>>>>>>>
> >>>>>>>>>> I updated the FLIP-33 wiki to remove all the histogram metrics
> >> from
> >>>>> the
> >>>>>>>>>> first version of metric convention due to the performance
> concern.
> >>>>> The
> >>>>>>>>> plan
> >>>>>>>>>> is to introduce them later when we have a mechanism to opt
> in/out
> >>>>>>>>> metrics.
> >>>>>>>>>> At that point, users can decide whether they want to pay the
> cost
> >> to
> >>>>>>> get
> >>>>>>>>>> the metric or not.
> >>>>>>>>>>
> >>>>>>>>>> As Stephan suggested, for this FLIP, let's first try to agree on
> >> the
> >>>>>>>>> small
> >>>>>>>>>> list of conventional metrics that connectors should follow.
> >>>>>>>>>> Just to be clear, the purpose of the convention is not to
> enforce
> >>>>> every
> >>>>>>>>>> connector to report all these metrics, but to provide a guidance
> >> in
> >>>>>>> case
> >>>>>>>>>> these metrics are reported by some connectors.
> >>>>>>>>>>
> >>>>>>>>>>
> >>>>>>>>>> @ Stephan & Chesnay,
> >>>>>>>>>>
> >>>>>>>>>> Regarding the duplication of `RecordsIn` metric in operator /
> task
> >>>>>>>>>> IOMetricGroups, from what I understand, for source operator, it
> is
> >>>>>>>>> actually
> >>>>>>>>>> the SourceFunction that reports the operator level
> >>>>>>>>>> RecordsIn/RecordsInPerSecond metric. So they are essentially the
> >>>>> same
> >>>>>>>>>> metric in the operator level IOMetricGroup. Similarly for the
> Sink
> >>>>>>>>>> operator, the operator level RecordsOut/RecordsOutPerSecond
> >> metrics
> >>>>> are
> >>>>>>>>>> also reported by the Sink function. I marked them as existing in
> >> the
> >>>>>>>>>> FLIP-33 wiki page. Please let me know if I misunderstood.
> >>>>>>>>>>
> >>>>>>>>>> Thanks,
> >>>>>>>>>>
> >>>>>>>>>> Jiangjie (Becket) Qin
> >>>>>>>>>>
> >>>>>>>>>>
> >>>>>>>>>> On Thu, May 30, 2019 at 5:16 PM Becket Qin <
> becket.qin@gmail.com>
> >>>>>>> wrote:
> >>>>>>>>>>
> >>>>>>>>>>> Hi Piotr,
> >>>>>>>>>>>
> >>>>>>>>>>> Thanks a lot for the feedback.
> >>>>>>>>>>>
> >>>>>>>>>>> 1a) I guess you are referring to the part that "original system
> >>>>>>> specific
> >>>>>>>>>>> metrics should also be reported". The performance impact
> depends
> >> on
> >>>>>>> the
> >>>>>>>>>>> implementation. An efficient implementation would only record
> the
> >>>>>>> metric
> >>>>>>>>>>> once, but report them with two different metric names. This is
> >>>>>>> unlikely
> >>>>>>>>> to
> >>>>>>>>>>> hurt performance.
> >>>>>>>>>>>
> >>>>>>>>>>> 1b) Yes, I agree that we should avoid adding overhead to the
> >>>>> critical
> >>>>>>>>> path
> >>>>>>>>>>> by all means. This is sometimes a tradeoff, running blindly
> >> without
> >>>>>>> any
> >>>>>>>>>>> metric gives best performance, but sometimes might be
> frustrating
> >>>>> when
> >>>>>>>>> we
> >>>>>>>>>>> debug some issues.
> >>>>>>>>>>>
> >>>>>>>>>>> 2. The metrics are indeed very useful. Are they supposed to be
> >>>>>>> reported
> >>>>>>>>> by
> >>>>>>>>>>> the connectors or Flink itself? At this point FLIP-33 is more
> >>>>> focused
> >>>>>>> on
> >>>>>>>>>>> provide a guidance to the connector authors on the metrics
> >>>>> reporting.
> >>>>>>>>> That
> >>>>>>>>>>> said, after FLIP-27, I think we should absolutely report these
> >>>>> metrics
> >>>>>>>>> in
> >>>>>>>>>>> the abstract implementation. In any case, the metric convention
> >> in
> >>>>>>> this
> >>>>>>>>>>> list are expected to evolve over time.
> >>>>>>>>>>>
> >>>>>>>>>>> Thanks,
> >>>>>>>>>>>
> >>>>>>>>>>> Jiangjie (Becket) Qin
> >>>>>>>>>>>
> >>>>>>>>>>> On Tue, May 28, 2019 at 6:24 PM Piotr Nowojski <
> >>>>> piotr@ververica.com>
> >>>>>>>>>>> wrote:
> >>>>>>>>>>>
> >>>>>>>>>>>> Hi,
> >>>>>>>>>>>>
> >>>>>>>>>>>> Thanks for the proposal and driving the effort here Becket :)
> >> I’ve
> >>>>>>> read
> >>>>>>>>>>>> through the FLIP-33 [1], and here are couple of my thoughts.
> >>>>>>>>>>>>
> >>>>>>>>>>>> Big +1 for standardising the metric names between connectors,
> it
> >>>>> will
> >>>>>>>>>>>> definitely help us and users a lot.
> >>>>>>>>>>>>
> >>>>>>>>>>>> Issues/questions/things to discuss that I’ve thought of:
> >>>>>>>>>>>>
> >>>>>>>>>>>> 1a. If we are about to duplicate some metrics, can this
> become a
> >>>>>>>>>>>> performance issue?
> >>>>>>>>>>>> 1b. Generally speaking, we should make sure that collecting
> >> those
> >>>>>>>>> metrics
> >>>>>>>>>>>> is as non intrusive as possible, especially that they will
> need
> >>>>> to be
> >>>>>>>>>>>> updated once per record. (They might be collected more rarely
> >> with
> >>>>>>> some
> >>>>>>>>>>>> overhead, but the hot path of updating it per record will need
> >> to
> >>>>> be
> >>>>>>> as
> >>>>>>>>>>>> quick as possible). That includes both avoiding heavy
> >> computation
> >>>>> on
> >>>>>>>>> per
> >>>>>>>>>>>> record path: histograms?, measuring time for time based
> metrics
> >>>>> (per
> >>>>>>>>>>>> second) (System.currentTimeMillis() depending on the
> >>>>> implementation
> >>>>>>> can
> >>>>>>>>>>>> invoke a system call)
> >>>>>>>>>>>>
> >>>>>>>>>>>> 2. It would be nice to have metrics, that allow us to check
> the
> >>>>> cause
> >>>>>>>>> of
> >>>>>>>>>>>> back pressure:
> >>>>>>>>>>>> a) for sources, length of input queue (in bytes? Or boolean
> >>>>>>>>>>>> hasSomethingl/isEmpty)
> >>>>>>>>>>>> b) for sinks, length of output queue (in bytes? Or boolean
> >>>>>>>>>>>> hasSomething/isEmpty)
> >>>>>>>>>>>>
> >>>>>>>>>>>> a) is useful in a scenario when we are processing backlog of
> >>>>> records,
> >>>>>>>>> all
> >>>>>>>>>>>> of the internal Flink’s input/output network buffers are
> empty,
> >>>>> and
> >>>>>>> we
> >>>>>>>>> want
> >>>>>>>>>>>> to check whether the external source system is the bottleneck
> >>>>>>> (source’s
> >>>>>>>>>>>> input queue will be empty), or if the Flink’s connector is the
> >>>>>>>>> bottleneck
> >>>>>>>>>>>> (source’s input queues will be full).
> >>>>>>>>>>>> b) similar story. Backlog of records, but this time all of the
> >>>>>>> internal
> >>>>>>>>>>>> Flink’s input/ouput network buffers are full, and we want o
> >> check
> >>>>>>>>> whether
> >>>>>>>>>>>> the external sink system is the bottleneck (sink output queues
> >> are
> >>>>>>>>> full),
> >>>>>>>>>>>> or if the Flink’s connector is the bottleneck (sink’s output
> >>>>> queues
> >>>>>>>>> will be
> >>>>>>>>>>>> empty)
> >>>>>>>>>>>>
> >>>>>>>>>>>> It might be sometimes difficult to provide those metrics, so
> >> they
> >>>>>>> could
> >>>>>>>>>>>> be optional, but if we could provide them, it would be really
> >>>>>>> helpful.
> >>>>>>>>>>>>
> >>>>>>>>>>>> Piotrek
> >>>>>>>>>>>>
> >>>>>>>>>>>> [1]
> >>>>>>>>>>>>
> >>>>>>>>>
> >>>>>>>
> >>>>>
> >>
> https://cwiki.apache.org/confluence/display/FLINK/FLIP-33:+Standardize+Connector+Metrics
> >>>>>>>>>>>> <
> >>>>>>>>>>>>
> >>>>>>>>>
> >>>>>>>
> >>>>>
> >>
> https://cwiki.apache.org/confluence/display/FLINK/FLIP-33:+Standardize+Connector+Metrics
> >>>>>>>>>>>>>
> >>>>>>>>>>>>
> >>>>>>>>>>>>> On 24 Apr 2019, at 13:28, Stephan Ewen <se...@apache.org>
> >> wrote:
> >>>>>>>>>>>>>
> >>>>>>>>>>>>> I think this sounds reasonable.
> >>>>>>>>>>>>>
> >>>>>>>>>>>>> Let's keep the "reconfiguration without stopping the job" out
> >> of
> >>>>>>> this,
> >>>>>>>>>>>>> because that would be a super big effort and if we approach
> >> that,
> >>>>>>> then
> >>>>>>>>>>>> in
> >>>>>>>>>>>>> more generic way rather than specific to connector metrics.
> >>>>>>>>>>>>>
> >>>>>>>>>>>>> I would suggest to look at the following things before
> starting
> >>>>> with
> >>>>>>>>> any
> >>>>>>>>>>>>> implementation work:
> >>>>>>>>>>>>>
> >>>>>>>>>>>>> - Try and find a committer to support this, otherwise it will
> >> be
> >>>>>>> hard
> >>>>>>>>>>>> to
> >>>>>>>>>>>>> make progress
> >>>>>>>>>>>>> - Start with defining a smaller set of "core metrics" and
> >> extend
> >>>>> the
> >>>>>>>>>>>> set
> >>>>>>>>>>>>> later. I think that is easier than now blocking on reaching
> >>>>>>> consensus
> >>>>>>>>>>>> on a
> >>>>>>>>>>>>> large group of metrics.
> >>>>>>>>>>>>> - Find a solution to the problem Chesnay mentioned, that the
> >>>>>>> "records
> >>>>>>>>>>>> in"
> >>>>>>>>>>>>> metric is somehow overloaded and exists already in the IO
> >> Metric
> >>>>>>>>> group.
> >>>>>>>>>>>>>
> >>>>>>>>>>>>>
> >>>>>>>>>>>>> On Mon, Mar 25, 2019 at 7:16 AM Becket Qin <
> >> becket.qin@gmail.com
> >>>>>>
> >>>>>>>>>>>> wrote:
> >>>>>>>>>>>>>
> >>>>>>>>>>>>>> Hi Stephan,
> >>>>>>>>>>>>>>
> >>>>>>>>>>>>>> Thanks a lot for the feedback. All makes sense.
> >>>>>>>>>>>>>>
> >>>>>>>>>>>>>> It is a good suggestion to simply have an onRecord(numBytes,
> >>>>>>>>> eventTime)
> >>>>>>>>>>>>>> method for connector writers. It should meet most of the
> >>>>>>>>> requirements,
> >>>>>>>>>>>>>> individual
> >>>>>>>>>>>>>>
> >>>>>>>>>>>>>> The configurable metrics feature is something really useful,
> >>>>>>>>>>>> especially if
> >>>>>>>>>>>>>> we can somehow make it dynamically configurable without
> >> stopping
> >>>>>>> the
> >>>>>>>>>>>> jobs.
> >>>>>>>>>>>>>> It might be better to make it a separate discussion because
> it
> >>>>> is a
> >>>>>>>>>>>> more
> >>>>>>>>>>>>>> generic feature instead of only for connectors.
> >>>>>>>>>>>>>>
> >>>>>>>>>>>>>> So in order to make some progress, in this FLIP we can limit
> >> the
> >>>>>>>>>>>> discussion
> >>>>>>>>>>>>>> scope to the connector related items:
> >>>>>>>>>>>>>>
> >>>>>>>>>>>>>> - the standard connector metric names and types.
> >>>>>>>>>>>>>> - the abstract ConnectorMetricHandler interface
> >>>>>>>>>>>>>>
> >>>>>>>>>>>>>> I'll start a separate thread to discuss other general metric
> >>>>>>> related
> >>>>>>>>>>>>>> enhancement items including:
> >>>>>>>>>>>>>>
> >>>>>>>>>>>>>> - optional metrics
> >>>>>>>>>>>>>> - dynamic metric configuration
> >>>>>>>>>>>>>> - potential combination with rate limiter
> >>>>>>>>>>>>>>
> >>>>>>>>>>>>>> Does this plan sound reasonable?
> >>>>>>>>>>>>>>
> >>>>>>>>>>>>>> Thanks,
> >>>>>>>>>>>>>>
> >>>>>>>>>>>>>> Jiangjie (Becket) Qin
> >>>>>>>>>>>>>>
> >>>>>>>>>>>>>> On Sat, Mar 23, 2019 at 5:53 AM Stephan Ewen <
> >> sewen@apache.org>
> >>>>>>>>> wrote:
> >>>>>>>>>>>>>>
> >>>>>>>>>>>>>>> Ignoring for a moment implementation details, this
> connector
> >>>>>>> metrics
> >>>>>>>>>>>> work
> >>>>>>>>>>>>>>> is a really good thing to do, in my opinion
> >>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>> The questions "oh, my job seems to be doing nothing, I am
> >>>>> looking
> >>>>>>> at
> >>>>>>>>>>>> the
> >>>>>>>>>>>>>> UI
> >>>>>>>>>>>>>>> and the 'records in' value is still zero" is in the top
> three
> >>>>>>>>> support
> >>>>>>>>>>>>>>> questions I have been asked personally.
> >>>>>>>>>>>>>>> Introspection into "how far is the consumer lagging behind"
> >>>>> (event
> >>>>>>>>>>>> time
> >>>>>>>>>>>>>>> fetch latency) came up many times as well.
> >>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>> So big +1 to solving this problem.
> >>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>> About the exact design - I would try to go for the
> following
> >>>>>>>>>>>> properties:
> >>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>> - keep complexity of of connectors. Ideally the metrics
> >> handler
> >>>>>>> has
> >>>>>>>>> a
> >>>>>>>>>>>>>>> single onRecord(numBytes, eventTime) method or so, and
> >>>>> everything
> >>>>>>>>>>>> else is
> >>>>>>>>>>>>>>> internal to the handler. That makes it dead simple for the
> >>>>>>>>> connector.
> >>>>>>>>>>>> We
> >>>>>>>>>>>>>>> can also think of an extensive scheme for connector
> specific
> >>>>>>>>> metrics.
> >>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>> - make it configurable on the job it cluster level which
> >>>>> metrics
> >>>>>>> the
> >>>>>>>>>>>>>>> handler internally creates when that method is invoked.
> >>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>> What do you think?
> >>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>> Best,
> >>>>>>>>>>>>>>> Stephan
> >>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>> On Thu, Mar 21, 2019 at 10:42 AM Chesnay Schepler <
> >>>>>>>>> chesnay@apache.org
> >>>>>>>>>>>>>
> >>>>>>>>>>>>>>> wrote:
> >>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>> As I said before, I believe this to be over-engineered and
> >>>>> have
> >>>>>>> no
> >>>>>>>>>>>>>>>> interest in this implementation.
> >>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>> There are conceptual issues like defining a duplicate
> >>>>>>>>>>>>>> numBytesIn(PerSec)
> >>>>>>>>>>>>>>>> metric that already exists for each operator.
> >>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>> On 21.03.2019 06:13, Becket Qin wrote:
> >>>>>>>>>>>>>>>>> A few updates to the thread. I uploaded a patch[1] as a
> >>>>> complete
> >>>>>>>>>>>>>>>>> example of how users can use the metrics in the future.
> >>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>> Some thoughts below after taking a look at the
> >>>>>>> AbstractMetricGroup
> >>>>>>>>>>>>>> and
> >>>>>>>>>>>>>>>>> its subclasses.
> >>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>> This patch intends to provide convenience for Flink
> >> connector
> >>>>>>>>>>>>>>>>> implementations to follow metrics standards proposed in
> >>>>> FLIP-33.
> >>>>>>>>> It
> >>>>>>>>>>>>>>>>> also try to enhance the metric management in general way
> to
> >>>>> help
> >>>>>>>>>>>>>> users
> >>>>>>>>>>>>>>>>> with:
> >>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>> 1. metric definition
> >>>>>>>>>>>>>>>>> 2. metric dependencies check
> >>>>>>>>>>>>>>>>> 3. metric validation
> >>>>>>>>>>>>>>>>> 4. metric control (turn on / off particular metrics)
> >>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>> This patch wraps |MetricGroup| to extend the
> functionality
> >> of
> >>>>>>>>>>>>>>>>> |AbstractMetricGroup| and its subclasses. The
> >>>>>>>>>>>>>>>>> |AbstractMetricGroup| mainly focus on the metric group
> >>>>>>> hierarchy,
> >>>>>>>>>>>> but
> >>>>>>>>>>>>>>>>> does not really manage the metrics other than keeping
> them
> >>>>> in a
> >>>>>>>>> Map.
> >>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>> Ideally we should only have one entry point for the
> >> metrics.
> >>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>> Right now the entry point is |AbstractMetricGroup|.
> >> However,
> >>>>>>>>> besides
> >>>>>>>>>>>>>>>>> the missing functionality mentioned above,
> >>>>> |AbstractMetricGroup|
> >>>>>>>>>>>>>> seems
> >>>>>>>>>>>>>>>>> deeply rooted in Flink runtime. We could extract it out
> to
> >>>>>>>>>>>>>>>>> flink-metrics in order to use it for generic purpose.
> There
> >>>>> will
> >>>>>>>>> be
> >>>>>>>>>>>>>>>>> some work, though.
> >>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>> Another approach is to make |AbstractMetrics| in this
> patch
> >>>>> as
> >>>>>>> the
> >>>>>>>>>>>>>>>>> metric entry point. It wraps metric group and provides
> the
> >>>>>>> missing
> >>>>>>>>>>>>>>>>> functionalities. Then we can roll out this pattern to
> >> runtime
> >>>>>>>>>>>>>>>>> components gradually as well.
> >>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>> My first thought is that the latter approach gives a more
> >>>>> smooth
> >>>>>>>>>>>>>>>>> migration. But I am also OK with doing a refactoring on
> the
> >>>>>>>>>>>>>>>>> |AbstractMetricGroup| family.
> >>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>> Thanks,
> >>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>> Jiangjie (Becket) Qin
> >>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>> [1] https://github.com/becketqin/flink/pull/1
> >>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>> On Mon, Feb 25, 2019 at 2:32 PM Becket Qin <
> >>>>>>> becket.qin@gmail.com
> >>>>>>>>>>>>>>>>> <ma...@gmail.com>> wrote:
> >>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>> Hi Chesnay,
> >>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>> It might be easier to discuss some implementation details
> >> in
> >>>>>>> the
> >>>>>>>>>>>>>>>>> PR review instead of in the FLIP discussion thread. I
> have
> >> a
> >>>>>>>>>>>>>> patch
> >>>>>>>>>>>>>>>>> for Kafka connectors ready but haven't submitted the PR
> >> yet.
> >>>>>>>>>>>>>>>>> Hopefully that will help explain a bit more.
> >>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>> ** Re: metric type binding
> >>>>>>>>>>>>>>>>> This is a valid point that worths discussing. If I
> >> understand
> >>>>>>>>>>>>>>>>> correctly, there are two points:
> >>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>> 1. Metric type / interface does not matter as long as the
> >>>>>>> metric
> >>>>>>>>>>>>>>>>> semantic is clearly defined.
> >>>>>>>>>>>>>>>>> Conceptually speaking, I agree that as long as the metric
> >>>>>>>>>>>>>> semantic
> >>>>>>>>>>>>>>>>> is defined, metric type does not matter. To some extent,
> >>>>> Gauge
> >>>>>>> /
> >>>>>>>>>>>>>>>>> Counter / Meter / Histogram themselves can be think of as
> >>>>> some
> >>>>>>>>>>>>>>>>> well-recognized semantics, if you wish. In Flink, these
> >>>>> metric
> >>>>>>>>>>>>>>>>> semantics have their associated interface classes. In
> >>>>> practice,
> >>>>>>>>>>>>>>>>> such semantic to interface binding seems necessary for
> >>>>>>> different
> >>>>>>>>>>>>>>>>> components to communicate. Simply standardize the
> semantic
> >>>>> of
> >>>>>>>>>>>>>> the
> >>>>>>>>>>>>>>>>> connector metrics seems not sufficient for people to
> build
> >>>>>>>>>>>>>>>>> ecosystem on top of. At the end of the day, we still need
> >> to
> >>>>>>>>> have
> >>>>>>>>>>>>>>>>> some embodiment of the metric semantics that people can
> >>>>> program
> >>>>>>>>>>>>>>>>> against.
> >>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>> 2. Sometimes the same metric semantic can be exposed
> using
> >>>>>>>>>>>>>>>>> different metric types / interfaces.
> >>>>>>>>>>>>>>>>> This is a good point. Counter and Gauge-as-a-Counter are
> >>>>> pretty
> >>>>>>>>>>>>>>>>> much interchangeable. This is more of a trade-off between
> >> the
> >>>>>>>>>>>>>> user
> >>>>>>>>>>>>>>>>> experience of metric producers and consumers. The metric
> >>>>>>>>>>>>>> producers
> >>>>>>>>>>>>>>>>> want to use Counter or Gauge depending on whether the
> >> counter
> >>>>>>> is
> >>>>>>>>>>>>>>>>> already tracked in code, while ideally the metric
> consumers
> >>>>>>> only
> >>>>>>>>>>>>>>>>> want to see a single metric type for each metric. I am
> >>>>> leaning
> >>>>>>>>>>>>>>>>> towards to make the metric producers happy, i.e. allow
> >> Gauge
> >>>>> /
> >>>>>>>>>>>>>>>>> Counter metric type, and the the metric consumers handle
> >> the
> >>>>>>>>> type
> >>>>>>>>>>>>>>>>> variation. The reason is that in practice, there might be
> >>>>> more
> >>>>>>>>>>>>>>>>> connector implementations than metric reporter
> >>>>> implementations.
> >>>>>>>>>>>>>> We
> >>>>>>>>>>>>>>>>> could also provide some helper method to facilitate
> reading
> >>>>>>> from
> >>>>>>>>>>>>>>>>> such variable metric type.
> >>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>> Just some quick replies to the comments around
> >> implementation
> >>>>>>>>>>>>>>>> details.
> >>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>> 4) single place where metrics are registered except
> >>>>>>>>>>>>>>>>> connector-specific
> >>>>>>>>>>>>>>>>> ones (which we can't really avoid).
> >>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>> Register connector specific ones in a single place is
> >>>>> actually
> >>>>>>>>>>>>>>>>> something that I want to achieve.
> >>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>> 2) I'm talking about time-series databases like
> >>>>> Prometheus.
> >>>>>>>>>>>>>> We
> >>>>>>>>>>>>>>>>> would
> >>>>>>>>>>>>>>>>> only have a gauge metric exposing the last
> >>>>>>>>> fetchTime/emitTime
> >>>>>>>>>>>>>>>>> that is
> >>>>>>>>>>>>>>>>> regularly reported to the backend (Prometheus), where a
> >>>>>>> user
> >>>>>>>>>>>>>>>>> could build
> >>>>>>>>>>>>>>>>> a histogram of his choosing when/if he wants it.
> >>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>> Not sure if such downsampling works. As an example, if a
> >> user
> >>>>>>>>>>>>>>>>> complains that there are some intermittent latency spikes
> >>>>>>> (maybe
> >>>>>>>>>>>>>> a
> >>>>>>>>>>>>>>>>> few records in 10 seconds) in their processing system.
> >>>>> Having a
> >>>>>>>>>>>>>>>>> Gauge sampling instantaneous latency seems unlikely
> useful.
> >>>>>>>>>>>>>>>>> However by looking at actual 99.9 percentile latency
> might
> >>>>>>> help.
> >>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>> Thanks,
> >>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>> Jiangjie (Becket) Qin
> >>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>> On Fri, Feb 22, 2019 at 9:30 PM Chesnay Schepler
> >>>>>>>>>>>>>>>>> <chesnay@apache.org <ma...@apache.org>> wrote:
> >>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>> Re: over complication of implementation.
> >>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>> I think I get understand better know what you're
> >> shooting
> >>>>>>>>>>>>>> for,
> >>>>>>>>>>>>>>>>> effectively something like the OperatorIOMetricGroup.
> >>>>>>>>>>>>>>>>> But still, re-define setupConnectorMetrics() to accept
> a
> >>>>>>> set
> >>>>>>>>>>>>>>>>> of flags
> >>>>>>>>>>>>>>>>> for counters/meters(ans _possibly_ histograms) along
> >>>>> with a
> >>>>>>>>>>>>>>>>> set of
> >>>>>>>>>>>>>>>>> well-defined Optional<Gauge<?>>, and return the group.
> >>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>> Solves all issues as far as i can tell:
> >>>>>>>>>>>>>>>>> 1) no metrics must be created manually (except Gauges,
> >>>>>>> which
> >>>>>>>>>>>>>>> are
> >>>>>>>>>>>>>>>>> effectively just Suppliers and you can't get around
> >>>>> this),
> >>>>>>>>>>>>>>>>> 2) additional metrics can be registered on the returned
> >>>>>>>>>>>>>> group,
> >>>>>>>>>>>>>>>>> 3) see 1),
> >>>>>>>>>>>>>>>>> 4) single place where metrics are registered except
> >>>>>>>>>>>>>>>>> connector-specific
> >>>>>>>>>>>>>>>>> ones (which we can't really avoid).
> >>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>> Re: Histogram
> >>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>> 1) As an example, whether "numRecordsIn" is exposed as
> a
> >>>>>>>>>>>>>>>>> Counter or a
> >>>>>>>>>>>>>>>>> Gauge should be irrelevant. So far we're using the
> >> metric
> >>>>>>>>>>>>>> type
> >>>>>>>>>>>>>>>>> that is
> >>>>>>>>>>>>>>>>> the most convenient at exposing a given value. If there
> >>>>> is
> >>>>>>>>>>>>>>>>> some backing
> >>>>>>>>>>>>>>>>> data-structure that we want to expose some data from we
> >>>>>>>>>>>>>>>>> typically opt
> >>>>>>>>>>>>>>>>> for a Gauge, as otherwise we're just mucking around
> with
> >>>>>>> the
> >>>>>>>>>>>>>>>>> Meter/Counter API to get it to match. Similarly, if we
> >>>>> want
> >>>>>>>>>>>>>> to
> >>>>>>>>>>>>>>>>> count
> >>>>>>>>>>>>>>>>> something but no current count exists we typically
> added
> >>>>> a
> >>>>>>>>>>>>>>>>> Counter.
> >>>>>>>>>>>>>>>>> That's why attaching semantics to metric types makes
> >>>>> little
> >>>>>>>>>>>>>>>>> sense (but
> >>>>>>>>>>>>>>>>> unfortunately several reporters already do it); for
> >>>>>>>>>>>>>>>>> counters/meters
> >>>>>>>>>>>>>>>>> certainly, but the majority of metrics are gauges.
> >>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>> 2) I'm talking about time-series databases like
> >>>>> Prometheus.
> >>>>>>>>>>>>>> We
> >>>>>>>>>>>>>>>>> would
> >>>>>>>>>>>>>>>>> only have a gauge metric exposing the last
> >>>>>>>>> fetchTime/emitTime
> >>>>>>>>>>>>>>>>> that is
> >>>>>>>>>>>>>>>>> regularly reported to the backend (Prometheus), where a
> >>>>>>> user
> >>>>>>>>>>>>>>>>> could build
> >>>>>>>>>>>>>>>>> a histogram of his choosing when/if he wants it.
> >>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>> On 22.02.2019 13:57, Becket Qin wrote:
> >>>>>>>>>>>>>>>>>> Hi Chesnay,
> >>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>> Thanks for the explanation.
> >>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>> ** Re: FLIP
> >>>>>>>>>>>>>>>>>> I might have misunderstood this, but it seems that
> "major
> >>>>>>>>>>>>>>>>> changes" are well
> >>>>>>>>>>>>>>>>>> defined in FLIP. The full contents is following:
> >>>>>>>>>>>>>>>>>> What is considered a "major change" that needs a FLIP?
> >>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>> Any of the following should be considered a major
> change:
> >>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>> - Any major new feature, subsystem, or piece of
> >>>>>>>>>>>>>>>>> functionality
> >>>>>>>>>>>>>>>>>> - *Any change that impacts the public interfaces of the
> >>>>>>>>>>>>>>>>> project*
> >>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>> What are the "public interfaces" of the project?
> >>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>> *All of the following are public interfaces *that people
> >>>>>>>>>>>>>>>>> build around:
> >>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>> - DataStream and DataSet API, including classes related
> >>>>>>>>>>>>>>>>> to that, such as
> >>>>>>>>>>>>>>>>>> StreamExecutionEnvironment
> >>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>> - Classes marked with the @Public annotation
> >>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>> - On-disk binary formats, such as
> >>>>>>>>>>>>>> checkpoints/savepoints
> >>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>> - User-facing scripts/command-line tools, i.e.
> >>>>>>>>>>>>>>>>> bin/flink, Yarn scripts,
> >>>>>>>>>>>>>>>>>> Mesos scripts
> >>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>> - Configuration settings
> >>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>> - *Exposed monitoring information*
> >>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>> So any monitoring information change is considered as
> >>>>>>>>>>>>>> public
> >>>>>>>>>>>>>>>>> interface, and
> >>>>>>>>>>>>>>>>>> any public interface change is considered as a "major
> >>>>>>>>>>>>>>> change".
> >>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>> ** Re: over complication of implementation.
> >>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>> Although this is more of implementation details that is
> >> not
> >>>>>>>>>>>>>>>>> covered by the
> >>>>>>>>>>>>>>>>>> FLIP. But it may be worth discussing.
> >>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>> First of all, I completely agree that we should use the
> >>>>>>>>>>>>>>>>> simplest way to
> >>>>>>>>>>>>>>>>>> achieve our goal. To me the goal is the following:
> >>>>>>>>>>>>>>>>>> 1. Clear connector conventions and interfaces.
> >>>>>>>>>>>>>>>>>> 2. The easiness of creating a connector.
> >>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>> Both of them are important to the prosperity of the
> >>>>>>>>>>>>>>>>> connector ecosystem. So
> >>>>>>>>>>>>>>>>>> I'd rather abstract as much as possible on our side to
> >> make
> >>>>>>>>>>>>>>>>> the connector
> >>>>>>>>>>>>>>>>>> developer's work lighter. Given this goal, a static util
> >>>>>>>>>>>>>>>>> method approach
> >>>>>>>>>>>>>>>>>> might have a few drawbacks:
> >>>>>>>>>>>>>>>>>> 1. Users still have to construct the metrics by
> >> themselves.
> >>>>>>>>>>>>>>>>> (And note that
> >>>>>>>>>>>>>>>>>> this might be erroneous by itself. For example, a
> customer
> >>>>>>>>>>>>>>>>> wrapper around
> >>>>>>>>>>>>>>>>>> dropwizard meter maybe used instead of MeterView).
> >>>>>>>>>>>>>>>>>> 2. When connector specific metrics are added, it is
> >>>>>>>>>>>>>>>>> difficult to enforce
> >>>>>>>>>>>>>>>>>> the scope to be the same as standard metrics.
> >>>>>>>>>>>>>>>>>> 3. It seems that a method proliferation is inevitable if
> >> we
> >>>>>>>>>>>>>>>>> want to apply
> >>>>>>>>>>>>>>>>>> sanity checks. e.g. The metric of numBytesIn was not
> >>>>>>>>>>>>>>>>> registered for a meter.
> >>>>>>>>>>>>>>>>>> 4. Metrics are still defined in random places and hard
> to
> >>>>>>>>>>>>>>>> track.
> >>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>> The current PR I had was inspired by the Config system
> in
> >>>>>>>>>>>>>>>>> Kafka, which I
> >>>>>>>>>>>>>>>>>> found pretty handy. In fact it is not only used by Kafka
> >>>>>>>>>>>>>>>>> itself but even
> >>>>>>>>>>>>>>>>>> some other projects that depend on Kafka. I am not
> saying
> >>>>>>>>>>>>>>>>> this approach is
> >>>>>>>>>>>>>>>>>> perfect. But I think it worths to save the work for
> >>>>>>>>>>>>>>>>> connector writers and
> >>>>>>>>>>>>>>>>>> encourage more systematic implementation. That being
> said,
> >>>>>>>>>>>>>> I
> >>>>>>>>>>>>>>>>> am fully open
> >>>>>>>>>>>>>>>>>> to suggestions.
> >>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>> Re: Histogram
> >>>>>>>>>>>>>>>>>> I think there are two orthogonal questions around those
> >>>>>>>>>>>>>>>> metrics:
> >>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>> 1. Regardless of the metric type, by just looking at the
> >>>>>>>>>>>>>>>>> meaning of a
> >>>>>>>>>>>>>>>>>> metric, is generic to all connectors? If the answer is
> >> yes,
> >>>>>>>>>>>>>>>>> we should
> >>>>>>>>>>>>>>>>>> include the metric into the convention. No matter
> whether
> >>>>>>>>>>>>>> we
> >>>>>>>>>>>>>>>>> include it
> >>>>>>>>>>>>>>>>>> into the convention or not, some connector
> implementations
> >>>>>>>>>>>>>>>>> will emit such
> >>>>>>>>>>>>>>>>>> metric. It is better to have a convention than letting
> >> each
> >>>>>>>>>>>>>>>>> connector do
> >>>>>>>>>>>>>>>>>> random things.
> >>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>> 2. If a standard metric is a histogram, what should we
> do?
> >>>>>>>>>>>>>>>>>> I agree that we should make it clear that using
> histograms
> >>>>>>>>>>>>>>>>> will have
> >>>>>>>>>>>>>>>>>> performance risk. But I do see histogram is useful in
> some
> >>>>>>>>>>>>>>>>> fine-granularity
> >>>>>>>>>>>>>>>>>> debugging where one do not have the luxury to stop the
> >>>>>>>>>>>>>>>>> system and inject
> >>>>>>>>>>>>>>>>>> more inspection code. So the workaround I am thinking is
> >> to
> >>>>>>>>>>>>>>>>> provide some
> >>>>>>>>>>>>>>>>>> implementation suggestions. Assume later on we have a
> >>>>>>>>>>>>>>>>> mechanism of
> >>>>>>>>>>>>>>>>>> selective metrics. In the abstract metrics class we can
> >>>>>>>>>>>>>>>>> disable those
> >>>>>>>>>>>>>>>>>> metrics by default individual connector writers does not
> >>>>>>>>>>>>>>>>> have to do
> >>>>>>>>>>>>>>>>>> anything (this is another advantage of having an
> >>>>>>>>>>>>>>>>> AbstractMetrics instead of
> >>>>>>>>>>>>>>>>>> static util methods.)
> >>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>> I am not sure I fully understand the histogram in the
> >>>>>>>>>>>>>>>>> backend approach. Can
> >>>>>>>>>>>>>>>>>> you explain a bit more? Do you mean emitting the raw
> data,
> >>>>>>>>>>>>>>>>> e.g. fetchTime
> >>>>>>>>>>>>>>>>>> and emitTime with each record and let the histogram
> >>>>>>>>>>>>>>>>> computation happen in
> >>>>>>>>>>>>>>>>>> the background? Or let the processing thread putting the
> >>>>>>>>>>>>>>>>> values into a
> >>>>>>>>>>>>>>>>>> queue and have a separate thread polling from the queue
> >> and
> >>>>>>>>>>>>>>>>> add them into
> >>>>>>>>>>>>>>>>>> the histogram?
> >>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>> Thanks,
> >>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>> Jiangjie (Becket) Qin
> >>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>> On Fri, Feb 22, 2019 at 4:34 PM Chesnay Schepler
> >>>>>>>>>>>>>>>>> <chesnay@apache.org <ma...@apache.org>>
> wrote:
> >>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>> Re: Flip
> >>>>>>>>>>>>>>>>>>> The very first line under both the main header and
> >> Purpose
> >>>>>>>>>>>>>>>>> section
> >>>>>>>>>>>>>>>>>>> describe Flips as "major changes", which this isn't.
> >>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>> Re: complication
> >>>>>>>>>>>>>>>>>>> I'm not arguing against standardization, but again an
> >>>>>>>>>>>>>>>>> over-complicated
> >>>>>>>>>>>>>>>>>>> implementation when a static utility method would be
> >>>>>>>>>>>>>>>>> sufficient.
> >>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>> public static void setupConnectorMetrics(
> >>>>>>>>>>>>>>>>>>> MetricGroup operatorMetricGroup,
> >>>>>>>>>>>>>>>>>>> String connectorName,
> >>>>>>>>>>>>>>>>>>> Optional<Gauge<Long>> numRecordsIn,
> >>>>>>>>>>>>>>>>>>> ...)
> >>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>> This gives you all you need:
> >>>>>>>>>>>>>>>>>>> * a well-defined set of metrics for a connector to
> opt-in
> >>>>>>>>>>>>>>>>>>> * standardized naming schemes for scope and individual
> >>>>>>>>>>>>>>> metrics
> >>>>>>>>>>>>>>>>>>> * standardize metric types (although personally I'm not
> >>>>>>>>>>>>>>>>> interested in that
> >>>>>>>>>>>>>>>>>>> since metric types should be considered syntactic
> sugar)
> >>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>> Re: Configurable Histogram
> >>>>>>>>>>>>>>>>>>> If anything they _must_ be turned off by default, but
> the
> >>>>>>>>>>>>>>>>> metric system is
> >>>>>>>>>>>>>>>>>>> already exposing so many options that I'm not too keen
> on
> >>>>>>>>>>>>>>>>> adding even more.
> >>>>>>>>>>>>>>>>>>> You have also only addressed my first argument against
> >>>>>>>>>>>>>>>>> histograms
> >>>>>>>>>>>>>>>>>>> (performance), the second one still stands (calculate
> >>>>>>>>>>>>>>>>> histogram in metric
> >>>>>>>>>>>>>>>>>>> backends instead).
> >>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>> On 21.02.2019 16:27, Becket Qin wrote:
> >>>>>>>>>>>>>>>>>>>> Hi Chesnay,
> >>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>> Thanks for the comments. I think this is worthy of a
> >> FLIP
> >>>>>>>>>>>>>>>>> because it is
> >>>>>>>>>>>>>>>>>>>> public API. According to the FLIP description a FlIP
> is
> >>>>>>>>>>>>>>>>> required in case
> >>>>>>>>>>>>>>>>>>> of:
> >>>>>>>>>>>>>>>>>>>> - Any change that impacts the public interfaces of
> >>>>>>>>>>>>>>>>> the project
> >>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>> and the following entry is found in the definition of
> >>>>>>>>>>>>>>>>> "public interface".
> >>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>> - Exposed monitoring information
> >>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>> Metrics are critical to any production system. So a
> >> clear
> >>>>>>>>>>>>>>>>> metric
> >>>>>>>>>>>>>>>>>>> definition
> >>>>>>>>>>>>>>>>>>>> is important for any serious users. For an
> organization
> >>>>>>>>>>>>>>>>> with large Flink
> >>>>>>>>>>>>>>>>>>>> installation, change in metrics means great amount of
> >>>>>>>>>>>>>>>>> work. So such
> >>>>>>>>>>>>>>>>>>> changes
> >>>>>>>>>>>>>>>>>>>> do need to be fully discussed and documented.
> >>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>> ** Re: Histogram.
> >>>>>>>>>>>>>>>>>>>> We can discuss whether there is a better way to expose
> >>>>>>>>>>>>>>>>> metrics that are
> >>>>>>>>>>>>>>>>>>>> suitable for histograms. My micro-benchmark on various
> >>>>>>>>>>>>>>>>> histogram
> >>>>>>>>>>>>>>>>>>>> implementations also indicates that they are
> >>>>>>>>>>>>>> significantly
> >>>>>>>>>>>>>>>>> slower than
> >>>>>>>>>>>>>>>>>>>> other metric types. But I don't think that means never
> >>>>>>>>>>>>>> use
> >>>>>>>>>>>>>>>>> histogram, but
> >>>>>>>>>>>>>>>>>>>> means use it with caution. For example, we can suggest
> >>>>>>>>>>>>>> the
> >>>>>>>>>>>>>>>>>>> implementations
> >>>>>>>>>>>>>>>>>>>> to turn them off by default and only turn it on for a
> >>>>>>>>>>>>>>>>> small amount of
> >>>>>>>>>>>>>>>>>>> time
> >>>>>>>>>>>>>>>>>>>> when performing some micro-debugging.
> >>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>> ** Re: complication:
> >>>>>>>>>>>>>>>>>>>> Connector conventions are essential for Flink
> ecosystem.
> >>>>>>>>>>>>>>>>> Flink connectors
> >>>>>>>>>>>>>>>>>>>> pool is probably the most important part of Flink,
> just
> >>>>>>>>>>>>>>>>> like any other
> >>>>>>>>>>>>>>>>>>> data
> >>>>>>>>>>>>>>>>>>>> system. Clear conventions of connectors will help
> build
> >>>>>>>>>>>>>>>>> Flink ecosystem
> >>>>>>>>>>>>>>>>>>> in
> >>>>>>>>>>>>>>>>>>>> a more organic way.
> >>>>>>>>>>>>>>>>>>>> Take the metrics convention as an example, imagine
> >>>>>>>>>>>>>> someone
> >>>>>>>>>>>>>>>>> has developed
> >>>>>>>>>>>>>>>>>>> a
> >>>>>>>>>>>>>>>>>>>> Flink connector for System foo, and another developer
> >> may
> >>>>>>>>>>>>>>>>> have developed
> >>>>>>>>>>>>>>>>>>> a
> >>>>>>>>>>>>>>>>>>>> monitoring and diagnostic framework for Flink which
> >>>>>>>>>>>>>>>>> analyzes the Flink
> >>>>>>>>>>>>>>>>>>> job
> >>>>>>>>>>>>>>>>>>>> performance based on metrics. With a clear metric
> >>>>>>>>>>>>>>>>> convention, those two
> >>>>>>>>>>>>>>>>>>>> projects could be developed independently. Once users
> >> put
> >>>>>>>>>>>>>>>>> them together,
> >>>>>>>>>>>>>>>>>>>> it would work without additional modifications. This
> >>>>>>>>>>>>>>>>> cannot be easily
> >>>>>>>>>>>>>>>>>>>> achieved by just defining a few constants.
> >>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>> ** Re: selective metrics:
> >>>>>>>>>>>>>>>>>>>> Sure, we can discuss that in a separate thread.
> >>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>> @Dawid
> >>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>> ** Re: latency / fetchedLatency
> >>>>>>>>>>>>>>>>>>>> The primary purpose of establish such a convention is
> to
> >>>>>>>>>>>>>>>>> help developers
> >>>>>>>>>>>>>>>>>>>> write connectors in a more compatible way. The
> >> convention
> >>>>>>>>>>>>>>>>> is supposed to
> >>>>>>>>>>>>>>>>>>> be
> >>>>>>>>>>>>>>>>>>>> defined more proactively. So when look at the
> >> convention,
> >>>>>>>>>>>>>>>>> it seems more
> >>>>>>>>>>>>>>>>>>>> important to see if the concept is applicable to
> >>>>>>>>>>>>>>>>> connectors in general.
> >>>>>>>>>>>>>>>>>>> It
> >>>>>>>>>>>>>>>>>>>> might be true so far only Kafka connector reports
> >>>>>>>>>>>>>> latency.
> >>>>>>>>>>>>>>>>> But there
> >>>>>>>>>>>>>>>>>>> might
> >>>>>>>>>>>>>>>>>>>> be hundreds of other connector implementations in the
> >>>>>>>>>>>>>>>>> Flink ecosystem,
> >>>>>>>>>>>>>>>>>>>> though not in the Flink repo, and some of them also
> >> emits
> >>>>>>>>>>>>>>>>> latency. I
> >>>>>>>>>>>>>>>>>>> think
> >>>>>>>>>>>>>>>>>>>> a lot of other sources actually also has an append
> >>>>>>>>>>>>>>>>> timestamp. e.g.
> >>>>>>>>>>>>>>>>>>> database
> >>>>>>>>>>>>>>>>>>>> bin logs and some K-V stores. So I wouldn't be
> surprised
> >>>>>>>>>>>>>>>>> if some database
> >>>>>>>>>>>>>>>>>>>> connector can also emit latency metrics.
> >>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>> Thanks,
> >>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>> Jiangjie (Becket) Qin
> >>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>> On Thu, Feb 21, 2019 at 10:14 PM Chesnay Schepler
> >>>>>>>>>>>>>>>>> <chesnay@apache.org <ma...@apache.org>>
> >>>>>>>>>>>>>>>>>>>> wrote:
> >>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>>> Regarding 2) It doesn't make sense to investigate
> this
> >>>>>>>>>>>>>> as
> >>>>>>>>>>>>>>>>> part of this
> >>>>>>>>>>>>>>>>>>>>> FLIP. This is something that could be of interest for
> >>>>>>>>>>>>>> the
> >>>>>>>>>>>>>>>>> entire metric
> >>>>>>>>>>>>>>>>>>>>> system, and should be designed for as such.
> >>>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>>> Regarding the proposal as a whole:
> >>>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>>> Histogram metrics shall not be added to the core of
> >>>>>>>>>>>>>>>>> Flink. They are
> >>>>>>>>>>>>>>>>>>>>> significantly more expensive than other metrics, and
> >>>>>>>>>>>>>>>>> calculating
> >>>>>>>>>>>>>>>>>>>>> histograms in the application is regarded as an
> >>>>>>>>>>>>>>>>> anti-pattern by several
> >>>>>>>>>>>>>>>>>>>>> metric backends, who instead recommend to expose the
> >> raw
> >>>>>>>>>>>>>>>>> data and
> >>>>>>>>>>>>>>>>>>>>> calculate the histogram in the backend.
> >>>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>>> Second, this seems overly complicated. Given that we
> >>>>>>>>>>>>>>>>> already established
> >>>>>>>>>>>>>>>>>>>>> that not all connectors will export all metrics we
> are
> >>>>>>>>>>>>>>>>> effectively
> >>>>>>>>>>>>>>>>>>>>> reducing this down to a consistent naming scheme. We
> >>>>>>>>>>>>>>>>> don't need anything
> >>>>>>>>>>>>>>>>>>>>> sophisticated for that; basically just a few
> constants
> >>>>>>>>>>>>>>>>> that all
> >>>>>>>>>>>>>>>>>>>>> connectors use.
> >>>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>>> I'm not convinced that this is worthy of a FLIP.
> >>>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>>> On 21.02.2019 14:26, Dawid Wysakowicz wrote:
> >>>>>>>>>>>>>>>>>>>>>> Hi,
> >>>>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>>>> Ad 1. In general I undestand and I agree. But those
> >>>>>>>>>>>>>>>>> particular metrics
> >>>>>>>>>>>>>>>>>>>>>> (latency, fetchLatency), right now would only be
> >>>>>>>>>>>>>>>>> reported if user uses
> >>>>>>>>>>>>>>>>>>>>>> KafkaConsumer with internal timestampAssigner with
> >>>>>>>>>>>>>>>>> StreamCharacteristic
> >>>>>>>>>>>>>>>>>>>>>> set to EventTime, right? That sounds like a very
> >>>>>>>>>>>>>>>>> specific case. I am
> >>>>>>>>>>>>>>>>>>> not
> >>>>>>>>>>>>>>>>>>>>>> sure if we should introduce a generic metric that
> will
> >>>>>>>>>>>>>> be
> >>>>>>>>>>>>>>>>>>>>>> disabled/absent for most of implementations.
> >>>>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>>>> Ad.2 That sounds like an orthogonal issue, that
> might
> >>>>>>>>>>>>>>>>> make sense to
> >>>>>>>>>>>>>>>>>>>>>> investigate in the future.
> >>>>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>>>> Best,
> >>>>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>>>> Dawid
> >>>>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>>>> On 21/02/2019 13:20, Becket Qin wrote:
> >>>>>>>>>>>>>>>>>>>>>>> Hi Dawid,
> >>>>>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>>>>> Thanks for the feedback. That makes sense to me.
> >> There
> >>>>>>>>>>>>>>>>> are two cases
> >>>>>>>>>>>>>>>>>>> to
> >>>>>>>>>>>>>>>>>>>>> be
> >>>>>>>>>>>>>>>>>>>>>>> addressed.
> >>>>>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>>>>> 1. The metrics are supposed to be a guidance. It is
> >>>>>>>>>>>>>>>>> likely that a
> >>>>>>>>>>>>>>>>>>>>> connector
> >>>>>>>>>>>>>>>>>>>>>>> only supports some but not all of the metrics. In
> >> that
> >>>>>>>>>>>>>>>>> case, each
> >>>>>>>>>>>>>>>>>>>>> connector
> >>>>>>>>>>>>>>>>>>>>>>> implementation should have the freedom to decide
> >> which
> >>>>>>>>>>>>>>>>> metrics are
> >>>>>>>>>>>>>>>>>>>>>>> reported. For the metrics that are supported, the
> >>>>>>>>>>>>>>>>> guidance should be
> >>>>>>>>>>>>>>>>>>>>>>> followed.
> >>>>>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>>>>> 2. Sometimes users may want to disable certain
> >> metrics
> >>>>>>>>>>>>>>>>> for some reason
> >>>>>>>>>>>>>>>>>>>>>>> (e.g. performance / reprocessing of data). A
> generic
> >>>>>>>>>>>>>>>>> mechanism should
> >>>>>>>>>>>>>>>>>>> be
> >>>>>>>>>>>>>>>>>>>>>>> provided to allow user choose which metrics are
> >>>>>>>>>>>>>>>>> reported. This
> >>>>>>>>>>>>>>>>>>> mechanism
> >>>>>>>>>>>>>>>>>>>>>>> should also be honored by the connector
> >>>>>>>>>>>>>> implementations.
> >>>>>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>>>>> Does this sound reasonable to you?
> >>>>>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>>>>> Thanks,
> >>>>>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>>>>> Jiangjie (Becket) Qin
> >>>>>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>>>>> On Thu, Feb 21, 2019 at 4:22 PM Dawid Wysakowicz <
> >>>>>>>>>>>>>>>>>>>>> dwysakowicz@apache.org <mailto:
> dwysakowicz@apache.org
> >>>>
> >>>>>>>>>>>>>>>>>>>>>>> wrote:
> >>>>>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>>>>>> Hi,
> >>>>>>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>>>>>> Generally I like the idea of having a unified,
> >>>>>>>>>>>>>>>>> standard set of
> >>>>>>>>>>>>>>>>>>> metrics
> >>>>>>>>>>>>>>>>>>>>> for
> >>>>>>>>>>>>>>>>>>>>>>>> all connectors. I have some slight concerns about
> >>>>>>>>>>>>>>>>> fetchLatency and
> >>>>>>>>>>>>>>>>>>>>>>>> latency though. They are computed based on
> EventTime
> >>>>>>>>>>>>>>>>> which is not a
> >>>>>>>>>>>>>>>>>>>>> purely
> >>>>>>>>>>>>>>>>>>>>>>>> technical feature. It depends often on some
> business
> >>>>>>>>>>>>>>>>> logic, might be
> >>>>>>>>>>>>>>>>>>>>> absent
> >>>>>>>>>>>>>>>>>>>>>>>> or defined after source. Those metrics could also
> >>>>>>>>>>>>>>>>> behave in a weird
> >>>>>>>>>>>>>>>>>>>>> way in
> >>>>>>>>>>>>>>>>>>>>>>>> case of replaying backlog. Therefore I am not sure
> >> if
> >>>>>>>>>>>>>>>>> we should
> >>>>>>>>>>>>>>>>>>> include
> >>>>>>>>>>>>>>>>>>>>>>>> those metrics by default. Maybe we could at least
> >>>>>>>>>>>>>>>>> introduce a feature
> >>>>>>>>>>>>>>>>>>>>>>>> switch for them? What do you think?
> >>>>>>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>>>>>> Best,
> >>>>>>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>>>>>> Dawid
> >>>>>>>>>>>>>>>>>>>>>>>> On 21/02/2019 03:13, Becket Qin wrote:
> >>>>>>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>>>>>> Bump. If there is no objections to the proposed
> >>>>>>>>>>>>>>>>> metrics. I'll start a
> >>>>>>>>>>>>>>>>>>>>>>>> voting thread later toady.
> >>>>>>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>>>>>> Thanks,
> >>>>>>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>>>>>> Jiangjie (Becket) Qin
> >>>>>>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>>>>>> On Mon, Feb 11, 2019 at 8:17 PM Becket Qin
> >>>>>>>>>>>>>>>>> <becket.qin@gmail.com <ma...@gmail.com>> <
> >>>>>>>>>>>>>>>>>>>>> becket.qin@gmail.com <ma...@gmail.com>>
> >>>>>>>>>>>>>>> wrote:
> >>>>>>>>>>>>>>>>>>>>>>>> Hi folks,
> >>>>>>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>>>>>> I would like to start the FLIP discussion thread
> >>>>>>>>>>>>>> about
> >>>>>>>>>>>>>>>>> standardize
> >>>>>>>>>>>>>>>>>>> the
> >>>>>>>>>>>>>>>>>>>>>>>> connector metrics.
> >>>>>>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>>>>>> In short, we would like to provide a convention of
> >>>>>>>>>>>>>>>>> Flink connector
> >>>>>>>>>>>>>>>>>>>>>>>> metrics. It will help simplify the monitoring and
> >>>>>>>>>>>>>>>>> alerting on Flink
> >>>>>>>>>>>>>>>>>>>>> jobs.
> >>>>>>>>>>>>>>>>>>>>>>>> The FLIP link is following:
> >>>>>>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>
> >>>>>>>>>>>>
> >>>>>>>>>
> >>>>>>>
> >>>>>
> >>
> https://cwiki.apache.org/confluence/display/FLINK/FLIP-33%3A+Standardize+Connector+Metrics
> >>>>>>>>>>>>>>>>>>>>>>>> Thanks,
> >>>>>>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>>>>>> Jiangjie (Becket) Qin
> >>>>>>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>
> >>>>>>>>>>>>
> >>>>>>>>>>>>
> >>>>>>>>>
> >>>>>>>>>
> >>>>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>
> >>>>>
> >>
> >>
>
>
Re: [DISCUSS] FLIP-33: Standardize connector metrics
Posted by Piotr Nowojski <pi...@ververica.com>.
> we will need to revisit the convention list and adjust them accordingly when FLIP-27 is ready
Yes, this sounds good :)
Piotrek
> On 13 Jun 2019, at 13:35, Becket Qin <be...@gmail.com> wrote:
>
> Hi Piotr,
>
> That's great to know. Chances are that we will need to revisit the
> convention list and adjust them accordingly when FLIP-27 is ready, At that
> point we can mark some of the metrics as available by default for
> connectors implementing the new interface.
>
> Thanks,
>
> Jiangjie (Becket) Qin
>
> On Thu, Jun 13, 2019 at 3:51 PM Piotr Nowojski <pi...@ververica.com> wrote:
>
>> Thanks for driving this. I’ve just noticed one small thing. With new
>> SourceReader interface Flink will be able to provide `idleTime` metric
>> automatically.
>>
>> Piotrek
>>
>>> On 13 Jun 2019, at 03:30, Becket Qin <be...@gmail.com> wrote:
>>>
>>> Thanks all for the feedback and discussion.
>>>
>>> Since there wasn't any concern raised, I've started the voting thread for
>>> this FLIP, but please feel free to continue the discussion here if you
>>> think something still needs to be addressed.
>>>
>>> Thanks,
>>>
>>> Jiangjie (Becket) Qin
>>>
>>>
>>>
>>> On Mon, Jun 10, 2019 at 9:10 AM Becket Qin <be...@gmail.com> wrote:
>>>
>>>> Hi Piotr,
>>>>
>>>> Thanks for the comments. Yes, you are right. Users will have to look at
>>>> other metrics to decide whether the pipeline is healthy or not in the
>> first
>>>> place before they can use the time-based metric to fix the bottleneck.
>>>>
>>>> I agree that once we have FLIP-27 ready, some of the metrics can just be
>>>> reported by the abstract implementation.
>>>>
>>>> I've updated FLIP-33 wiki page to add the pendingBytes and
>> pendingRecords
>>>> metric. Please let me know if you have any concern over the updated
>> metric
>>>> convention proposal.
>>>>
>>>> @Chesnay Schepler <ch...@apache.org> @Stephan Ewen
>>>> <st...@ververica.com> will you also have time to take a look at the
>>>> proposed metric convention? If there is no further concern I'll start a
>>>> voting thread for this FLIP in two days.
>>>>
>>>> Thanks,
>>>>
>>>> Jiangjie (Becket) Qin
>>>>
>>>>
>>>>
>>>> On Wed, Jun 5, 2019 at 6:54 PM Piotr Nowojski <pi...@ververica.com>
>> wrote:
>>>>
>>>>> Hi Becket,
>>>>>
>>>>> Thanks for the answer :)
>>>>>
>>>>>> By time-based metric, I meant the portion of time spent on producing
>> the
>>>>>> record to downstream. For example, a source connector can report that
>>>>> it's
>>>>>> spending 80% of time to emit record to downstream processing pipeline.
>>>>> In
>>>>>> another case, a sink connector may report that its spending 30% of
>> time
>>>>>> producing the records to the external system.
>>>>>>
>>>>>> This is in some sense equivalent to the buffer usage metric:
>>>>>
>>>>>> - 80% of time spent on emitting records to downstream ---> downstream
>>>>>> node is bottleneck ---> output buffer is probably full.
>>>>>> - 30% of time spent on emitting records to downstream ---> downstream
>>>>>> node is not bottleneck ---> output buffer is probably not full.
>>>>>
>>>>> If by “time spent on emitting records to downstream” you understand
>>>>> “waiting on back pressure”, then I see your point. And I agree that
>> some
>>>>> kind of ratio/time based metric gives you more information. However
>> under
>>>>> “time spent on emitting records to downstream” might be hidden the
>>>>> following (extreme) situation:
>>>>>
>>>>> 1. Job is barely able to handle influx of records, there is 99%
>>>>> CPU/resource usage in the cluster, but nobody is
>>>>> bottlenecked/backpressured, all output buffers are empty, everybody is
>>>>> waiting in 1% of it’s time for more records to process.
>>>>> 2. 80% time can still be spent on "down stream operators”, because they
>>>>> are the CPU intensive operations, but this doesn’t mean that
>> increasing the
>>>>> parallelism down the stream will help with anything there. To the
>> contrary,
>>>>> increasing parallelism of the source operator might help to increase
>>>>> resource utilisation up to 100%.
>>>>>
>>>>> However, this “time based/ratio” approach can be extended to in/output
>>>>> buffer usage. Besides collecting an information that input/output
>> buffer is
>>>>> full/empty, we can probe profile how often are buffer empty/full. If
>> output
>>>>> buffer is full 1% of times, there is almost no back pressure. If it’s
>> full
>>>>> 80% of times, there is some back pressure, if it’s full 99.9% of times,
>>>>> there is huge back pressure.
>>>>>
>>>>> Now for autoscaling you could compare the input & output buffers fill
>>>>> ratio:
>>>>>
>>>>> 1. Both are high, the source of bottleneck is down the stream
>>>>> 2. Output is low, input is high, this is the bottleneck and the higher
>>>>> the difference, the bigger source of bottleneck is this is
>> operator/task
>>>>> 3. Output is high, input is low - there was some load spike that we are
>>>>> currently finishing to process
>>>>>
>>>>>
>>>>>
>>>>> But long story short, we are probably diverging from the topic of this
>>>>> discussion, and we can discuss this at some later point.
>>>>>
>>>>> For now, for sources:
>>>>>
>>>>> as I wrote before, +1 for:
>>>>> - pending.bytes, Gauge
>>>>> - pending.messages, Gauge
>>>>>
>>>>> When we will be developing/discussing SourceReader from FLIP-27 we
>> might
>>>>> then add:
>>>>>
>>>>> - in-memory.buffer.usage (0 - 100%)
>>>>>
>>>>> Which will be estimated automatically by Flink while user will be able
>> to
>>>>> override/provide better estimation.
>>>>>
>>>>> Piotrek
>>>>>
>>>>>> On 5 Jun 2019, at 05:42, Becket Qin <be...@gmail.com> wrote:
>>>>>>
>>>>>> Hi Piotr,
>>>>>>
>>>>>> Thanks for the explanation. Please see some clarifications below.
>>>>>>
>>>>>> By time-based metric, I meant the portion of time spent on producing
>> the
>>>>>> record to downstream. For example, a source connector can report that
>>>>> it's
>>>>>> spending 80% of time to emit record to downstream processing pipeline.
>>>>> In
>>>>>> another case, a sink connector may report that its spending 30% of
>> time
>>>>>> producing the records to the external system.
>>>>>>
>>>>>> This is in some sense equivalent to the buffer usage metric:
>>>>>> - 80% of time spent on emitting records to downstream ---> downstream
>>>>>> node is bottleneck ---> output buffer is probably full.
>>>>>> - 30% of time spent on emitting records to downstream ---> downstream
>>>>>> node is not bottleneck ---> output buffer is probably not full.
>>>>>>
>>>>>> However, the time-based metric has a few advantages that the buffer
>>>>> usage
>>>>>> metric may not have.
>>>>>>
>>>>>> 1. Buffer usage metric may not be applicable to all the connector
>>>>>> implementations, while reporting time-based metric are always doable.
>>>>>> Some source connectors may not have any input buffer, or they may use
>>>>> some
>>>>>> third party library that does not expose the input buffer at all.
>>>>>> Similarly, for sink connectors, the implementation may not have any
>>>>> output
>>>>>> buffer, or the third party library does not expose such buffer.
>>>>>>
>>>>>> 2. Although both type of metrics can detect bottleneck, time-based
>>>>> metrics
>>>>>> can be used to generate a more informed action to remove the
>> bottleneck.
>>>>>> For example, when the downstream is bottleneck, the output buffer
>> usage
>>>>>> metric is likely to be 100%, and the input buffer usage might be 0%.
>>>>> That
>>>>>> means we don't know what is the suitable parallelism to lift the
>>>>>> bottleneck. The time-based metric, on the other hand, would give
>> useful
>>>>>> information, e.g. if 80% of time was spent on emitting records, we can
>>>>>> roughly increase the downstream node parallelism by 4 times.
>>>>>>
>>>>>> Admittedly, the time-based metrics are more expensive than buffer
>>>>> usage. So
>>>>>> we may have to do some sampling to reduce the cost. But in general,
>>>>> using
>>>>>> time-based metrics seems worth adding.
>>>>>>
>>>>>> That being said, I don't think buffer usage metric and time-based
>>>>> metrics
>>>>>> are mutually exclusive. We can probably have both. It is just that in
>>>>>> practice, features like auto-scaling might prefer time-based metrics
>> for
>>>>>> the reason stated above.
>>>>>>
>>>>>>> 1. Define the metrics that would allow us to manually detect
>>>>> bottlenecks.
>>>>>> As I wrote, we already have them in most of the places, except of
>>>>>> sources/sinks.
>>>>>>> 2. Use those metrics, to automatically detect bottlenecks. Currently
>> we
>>>>>> are only automatically detecting back pressure and reporting it to the
>>>>> user
>>>>>> in web UI (is it exposed as a metric at all?). Detecting the root
>> cause
>>>>> of
>>>>>> the back pressure (bottleneck) is one step further.
>>>>>>> 3. Use the knowledge about where exactly the bottleneck is located,
>> to
>>>>>> try to do something with it.
>>>>>>
>>>>>> As explained above, I think time-based metric also addresses item 1
>> and
>>>>>> item 2.
>>>>>>
>>>>>> Any thoughts？
>>>>>>
>>>>>> Thanks,
>>>>>>
>>>>>> Jiangjie (Becket) Qin
>>>>>>
>>>>>>
>>>>>>
>>>>>> On Mon, Jun 3, 2019 at 4:14 PM Piotr Nowojski <pi...@ververica.com>
>>>>> wrote:
>>>>>>
>>>>>>> Hi again :)
>>>>>>>
>>>>>>>> - pending.bytes, Gauge
>>>>>>>> - pending.messages, Gauge
>>>>>>>
>>>>>>>
>>>>>>> +1
>>>>>>>
>>>>>>> And true, instead of overloading one of the metric it is better when
>>>>> user
>>>>>>> can choose to provide only one of them.
>>>>>>>
>>>>>>> Re 2:
>>>>>>>
>>>>>>>> If I understand correctly, this metric along with the pending
>> mesages
>>>>> /
>>>>>>>> bytes would answer the questions of:
>>>>>>>
>>>>>>>> - Does the connector consume fast enough? Lagging behind + empty
>>>>> buffer
>>>>>>> =
>>>>>>>> cannot consume fast enough.
>>>>>>>> - Does the connector emit fast enough? Lagging behind + full buffer
>> =
>>>>>>>> cannot emit fast enough, i.e. the Flink pipeline is slow.
>>>>>>>
>>>>>>> Yes, exactly. This can also be used to support decisions like
>> changing
>>>>> the
>>>>>>> parallelism of the sources and/or down stream operators.
>>>>>>>
>>>>>>> I’m not sure if I understand your proposal with time based
>>>>> measurements.
>>>>>>> Maybe I’m missing something, but I do not see how measuring time
>> alone
>>>>>>> could answer the problem: where is the bottleneck. Time spent on the
>>>>>>> next/emit might be short or long (depending on how heavy to process
>> the
>>>>>>> record is) and the source can still be bottlenecked/back pressured or
>>>>> not.
>>>>>>> Usually the easiest and the most reliable way how to detect
>>>>> bottlenecks is
>>>>>>> by checking usage of input & output buffers, since when input buffer
>> is
>>>>>>> full while output buffer is empty, that’s the definition of a
>>>>> bottleneck.
>>>>>>> Also this is usually very easy and cheap to measure (it works
>>>>> effectively
>>>>>>> the same way as current’s Flink back pressure monitoring, but more
>>>>> cleanly,
>>>>>>> without probing thread’s stack traces).
>>>>>>>
>>>>>>> Also keep in mind that we are already using the buffer usage metrics
>>>>> for
>>>>>>> detecting the bottlenecks in Flink’s internal network exchanges
>> (manual
>>>>>>> work). That’s the reason why I wanted to extend this to
>> sources/sinks,
>>>>>>> since they are currently our blind spot.
>>>>>>>
>>>>>>>> One feature we are currently working on to scale Flink automatically
>>>>>>> relies
>>>>>>>> on some metrics answering the same question
>>>>>>>
>>>>>>> That would be very helpful feature. I think in order to achieve that
>> we
>>>>>>> would need to:
>>>>>>> 1. Define the metrics that would allow us to manually detect
>>>>> bottlenecks.
>>>>>>> As I wrote, we already have them in most of the places, except of
>>>>>>> sources/sinks.
>>>>>>> 2. Use those metrics, to automatically detect bottlenecks. Currently
>> we
>>>>>>> are only automatically detecting back pressure and reporting it to
>> the
>>>>> user
>>>>>>> in web UI (is it exposed as a metric at all?). Detecting the root
>>>>> cause of
>>>>>>> the back pressure (bottleneck) is one step further.
>>>>>>> 3. Use the knowledge about where exactly the bottleneck is located,
>> to
>>>>> try
>>>>>>> to do something with it.
>>>>>>>
>>>>>>> I think you are aiming for point 3., but before we reach it, we are
>>>>> still
>>>>>>> missing 1. & 2. Also even if we have 3., there is a value in 1 & 2
>> for
>>>>>>> manual analysis/dashboards.
>>>>>>>
>>>>>>> However, having the knowledge of where the bottleneck is, doesn’t
>>>>>>> necessarily mean that we know what we can do about it. For example
>>>>>>> increasing parallelism might or might not help with anything (data
>>>>> skew,
>>>>>>> bottleneck on some resource that does not scale), but this remark
>>>>> applies
>>>>>>> always, regardless of the way how did we detect the bottleneck.
>>>>>>>
>>>>>>> Piotrek
>>>>>>>
>>>>>>>> On 3 Jun 2019, at 06:16, Becket Qin <be...@gmail.com> wrote:
>>>>>>>>
>>>>>>>> Hi Piotr,
>>>>>>>>
>>>>>>>> Thanks for the suggestion. Some thoughts below:
>>>>>>>>
>>>>>>>> Re 1: The pending messages / bytes.
>>>>>>>> I completely agree these are very useful metrics and we should
>> expect
>>>>> the
>>>>>>>> connector to report. WRT the way to expose them, it seems more
>>>>> consistent
>>>>>>>> to add two metrics instead of adding a method (unless there are
>> other
>>>>> use
>>>>>>>> cases other than metric reporting). So we can add the following two
>>>>>>> metrics.
>>>>>>>> - pending.bytes, Gauge
>>>>>>>> - pending.messages, Gauge
>>>>>>>> Applicable connectors can choose to report them. These two metrics
>>>>> along
>>>>>>>> with latency should be sufficient for users to understand the
>> progress
>>>>>>> of a
>>>>>>>> connector.
>>>>>>>>
>>>>>>>>
>>>>>>>> Re 2: Number of buffered data in-memory of the connector
>>>>>>>> If I understand correctly, this metric along with the pending
>> mesages
>>>>> /
>>>>>>>> bytes would answer the questions of:
>>>>>>>> - Does the connector consume fast enough? Lagging behind + empty
>>>>> buffer
>>>>>>> =
>>>>>>>> cannot consume fast enough.
>>>>>>>> - Does the connector emit fast enough? Lagging behind + full buffer
>> =
>>>>>>>> cannot emit fast enough, i.e. the Flink pipeline is slow.
>>>>>>>>
>>>>>>>> One feature we are currently working on to scale Flink automatically
>>>>>>> relies
>>>>>>>> on some metrics answering the same question, more specifically, we
>> are
>>>>>>>> profiling the time spent on .next() method (time to consume) and the
>>>>> time
>>>>>>>> spent on .collect() method (time to emit / process). One advantage
>> of
>>>>>>> such
>>>>>>>> method level time cost allows us to calculate the parallelism
>>>>> required to
>>>>>>>> keep up in case their is a lag.
>>>>>>>>
>>>>>>>> However, one concern I have regarding such metric is that they are
>>>>>>>> implementation specific. Either profiling on the method time, or
>>>>>>> reporting
>>>>>>>> buffer usage assumes the connector are implemented in such a way. A
>>>>>>>> slightly better solution might be have the following metric:
>>>>>>>>
>>>>>>>> - EmitTimeRatio (or FetchTimeRatio): The time spent on emitting
>>>>>>>> records / Total time elapsed.
>>>>>>>>
>>>>>>>> This assumes that the source connectors have to emit the records to
>>>>> the
>>>>>>>> downstream at some point. The emission may take some time ( e.g. go
>>>>>>> through
>>>>>>>> chained operators). And the rest of the time are spent to prepare
>> the
>>>>>>>> record to emit, including time for consuming and format conversion,
>>>>> etc.
>>>>>>>> Ideally, we'd like to see the time spent on record fetch and emit to
>>>>> be
>>>>>>>> about the same, so no one is bottleneck for the other.
>>>>>>>>
>>>>>>>> The downside of these time based metrics is additional overhead to
>> get
>>>>>>> the
>>>>>>>> time, therefore sampling might be needed. But in practice I feel
>> such
>>>>>>> time
>>>>>>>> based metric might be more useful if we want to take action.
>>>>>>>>
>>>>>>>>
>>>>>>>> I think we should absolutely add metrics in (1) to the metric
>>>>> convention.
>>>>>>>> We could also add the metrics mentioned in (2) if we reach consensus
>>>>> on
>>>>>>>> that. What do you think?
>>>>>>>>
>>>>>>>> Thanks,
>>>>>>>>
>>>>>>>> Jiangjie (Becket) Qin
>>>>>>>>
>>>>>>>>
>>>>>>>> On Fri, May 31, 2019 at 4:26 PM Piotr Nowojski <piotr@ververica.com
>>>
>>>>>>> wrote:
>>>>>>>>
>>>>>>>>> Hey Becket,
>>>>>>>>>
>>>>>>>>> Re 1a) and 1b) +1 from my side.
>>>>>>>>>
>>>>>>>>> I’ve discussed this issue:
>>>>>>>>>
>>>>>>>>>>>>
>>>>>>>>>>>> 2. It would be nice to have metrics, that allow us to check the
>>>>> cause
>>>>>>>>> of
>>>>>>>>>>>> back pressure:
>>>>>>>>>>>> a) for sources, length of input queue (in bytes? Or boolean
>>>>>>>>>>>> hasSomethingl/isEmpty)
>>>>>>>>>>>> b) for sinks, length of output queue (in bytes? Or boolean
>>>>>>>>>>>> hasSomething/isEmpty)
>>>>>>>>>
>>>>>>>>> With Nico at some lengths and he also saw the benefits of them. We
>>>>> also
>>>>>>>>> have more concrete proposal for that.
>>>>>>>>>
>>>>>>>>> Actually there are two really useful metrics, that we are missing
>>>>>>>>> currently:
>>>>>>>>>
>>>>>>>>> 1. Number of data/records/bytes in the backlog to process. For
>>>>> example
>>>>>>>>> remaining number of bytes in unread files. Or pending data in Kafka
>>>>>>> topics.
>>>>>>>>> 2. Number of buffered data in-memory of the connector, that are
>>>>> waiting
>>>>>>> to
>>>>>>>>> be processed pushed to Flink pipeline.
>>>>>>>>>
>>>>>>>>> Re 1:
>>>>>>>>> This would have to be a metric provided directly by a connector. It
>>>>>>> could
>>>>>>>>> be an undefined `int`:
>>>>>>>>>
>>>>>>>>> `int backlog` - estimate of pending work.
>>>>>>>>>
>>>>>>>>> “Undefined” meaning that it would be up to a connector to decided
>>>>>>> whether
>>>>>>>>> it’s measured in bytes, records, pending files or whatever it is
>>>>>>> possible
>>>>>>>>> to provide by the connector. This is because I assume not every
>>>>>>> connector
>>>>>>>>> can provide exact number and for some of them it might be
>> impossible
>>>>> to
>>>>>>>>> provide records number of bytes count.
>>>>>>>>>
>>>>>>>>> Re 2:
>>>>>>>>> This metric could be either provided by a connector, or calculated
>>>>>>> crudely
>>>>>>>>> by Flink:
>>>>>>>>>
>>>>>>>>> `float bufferUsage` - value from [0.0, 1.0] range
>>>>>>>>>
>>>>>>>>> Percentage of used in memory buffers, like in Kafka’s handover.
>>>>>>>>>
>>>>>>>>> It could be crudely implemented by Flink with FLIP-27
>>>>>>>>> SourceReader#isAvailable. If SourceReader is not available reported
>>>>>>>>> `bufferUsage` could be 0.0. If it is available, it could be 1.0. I
>>>>> think
>>>>>>>>> this would be a good enough estimation for most of the use cases
>>>>> (that
>>>>>>>>> could be overloaded and implemented better if desired). Especially
>>>>>>> since we
>>>>>>>>> are reporting only probed values: if probed values are almost
>> always
>>>>>>> “1.0”,
>>>>>>>>> it would mean that we have a back pressure. If they are almost
>> always
>>>>>>>>> “0.0”, there is probably no back pressure at the sources.
>>>>>>>>>
>>>>>>>>> What do you think about this?
>>>>>>>>>
>>>>>>>>> Piotrek
>>>>>>>>>
>>>>>>>>>> On 30 May 2019, at 11:41, Becket Qin <be...@gmail.com>
>> wrote:
>>>>>>>>>>
>>>>>>>>>> Hi all,
>>>>>>>>>>
>>>>>>>>>> Thanks a lot for all the feedback and comments. I'd like to
>> continue
>>>>>>> the
>>>>>>>>>> discussion on this FLIP.
>>>>>>>>>>
>>>>>>>>>> I updated the FLIP-33 wiki to remove all the histogram metrics
>> from
>>>>> the
>>>>>>>>>> first version of metric convention due to the performance concern.
>>>>> The
>>>>>>>>> plan
>>>>>>>>>> is to introduce them later when we have a mechanism to opt in/out
>>>>>>>>> metrics.
>>>>>>>>>> At that point, users can decide whether they want to pay the cost
>> to
>>>>>>> get
>>>>>>>>>> the metric or not.
>>>>>>>>>>
>>>>>>>>>> As Stephan suggested, for this FLIP, let's first try to agree on
>> the
>>>>>>>>> small
>>>>>>>>>> list of conventional metrics that connectors should follow.
>>>>>>>>>> Just to be clear, the purpose of the convention is not to enforce
>>>>> every
>>>>>>>>>> connector to report all these metrics, but to provide a guidance
>> in
>>>>>>> case
>>>>>>>>>> these metrics are reported by some connectors.
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>> @ Stephan & Chesnay,
>>>>>>>>>>
>>>>>>>>>> Regarding the duplication of `RecordsIn` metric in operator / task
>>>>>>>>>> IOMetricGroups, from what I understand, for source operator, it is
>>>>>>>>> actually
>>>>>>>>>> the SourceFunction that reports the operator level
>>>>>>>>>> RecordsIn/RecordsInPerSecond metric. So they are essentially the
>>>>> same
>>>>>>>>>> metric in the operator level IOMetricGroup. Similarly for the Sink
>>>>>>>>>> operator, the operator level RecordsOut/RecordsOutPerSecond
>> metrics
>>>>> are
>>>>>>>>>> also reported by the Sink function. I marked them as existing in
>> the
>>>>>>>>>> FLIP-33 wiki page. Please let me know if I misunderstood.
>>>>>>>>>>
>>>>>>>>>> Thanks,
>>>>>>>>>>
>>>>>>>>>> Jiangjie (Becket) Qin
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>> On Thu, May 30, 2019 at 5:16 PM Becket Qin <be...@gmail.com>
>>>>>>> wrote:
>>>>>>>>>>
>>>>>>>>>>> Hi Piotr,
>>>>>>>>>>>
>>>>>>>>>>> Thanks a lot for the feedback.
>>>>>>>>>>>
>>>>>>>>>>> 1a) I guess you are referring to the part that "original system
>>>>>>> specific
>>>>>>>>>>> metrics should also be reported". The performance impact depends
>> on
>>>>>>> the
>>>>>>>>>>> implementation. An efficient implementation would only record the
>>>>>>> metric
>>>>>>>>>>> once, but report them with two different metric names. This is
>>>>>>> unlikely
>>>>>>>>> to
>>>>>>>>>>> hurt performance.
>>>>>>>>>>>
>>>>>>>>>>> 1b) Yes, I agree that we should avoid adding overhead to the
>>>>> critical
>>>>>>>>> path
>>>>>>>>>>> by all means. This is sometimes a tradeoff, running blindly
>> without
>>>>>>> any
>>>>>>>>>>> metric gives best performance, but sometimes might be frustrating
>>>>> when
>>>>>>>>> we
>>>>>>>>>>> debug some issues.
>>>>>>>>>>>
>>>>>>>>>>> 2. The metrics are indeed very useful. Are they supposed to be
>>>>>>> reported
>>>>>>>>> by
>>>>>>>>>>> the connectors or Flink itself? At this point FLIP-33 is more
>>>>> focused
>>>>>>> on
>>>>>>>>>>> provide a guidance to the connector authors on the metrics
>>>>> reporting.
>>>>>>>>> That
>>>>>>>>>>> said, after FLIP-27, I think we should absolutely report these
>>>>> metrics
>>>>>>>>> in
>>>>>>>>>>> the abstract implementation. In any case, the metric convention
>> in
>>>>>>> this
>>>>>>>>>>> list are expected to evolve over time.
>>>>>>>>>>>
>>>>>>>>>>> Thanks,
>>>>>>>>>>>
>>>>>>>>>>> Jiangjie (Becket) Qin
>>>>>>>>>>>
>>>>>>>>>>> On Tue, May 28, 2019 at 6:24 PM Piotr Nowojski <
>>>>> piotr@ververica.com>
>>>>>>>>>>> wrote:
>>>>>>>>>>>
>>>>>>>>>>>> Hi,
>>>>>>>>>>>>
>>>>>>>>>>>> Thanks for the proposal and driving the effort here Becket :)
>> I’ve
>>>>>>> read
>>>>>>>>>>>> through the FLIP-33 [1], and here are couple of my thoughts.
>>>>>>>>>>>>
>>>>>>>>>>>> Big +1 for standardising the metric names between connectors, it
>>>>> will
>>>>>>>>>>>> definitely help us and users a lot.
>>>>>>>>>>>>
>>>>>>>>>>>> Issues/questions/things to discuss that I’ve thought of:
>>>>>>>>>>>>
>>>>>>>>>>>> 1a. If we are about to duplicate some metrics, can this become a
>>>>>>>>>>>> performance issue?
>>>>>>>>>>>> 1b. Generally speaking, we should make sure that collecting
>> those
>>>>>>>>> metrics
>>>>>>>>>>>> is as non intrusive as possible, especially that they will need
>>>>> to be
>>>>>>>>>>>> updated once per record. (They might be collected more rarely
>> with
>>>>>>> some
>>>>>>>>>>>> overhead, but the hot path of updating it per record will need
>> to
>>>>> be
>>>>>>> as
>>>>>>>>>>>> quick as possible). That includes both avoiding heavy
>> computation
>>>>> on
>>>>>>>>> per
>>>>>>>>>>>> record path: histograms?, measuring time for time based metrics
>>>>> (per
>>>>>>>>>>>> second) (System.currentTimeMillis() depending on the
>>>>> implementation
>>>>>>> can
>>>>>>>>>>>> invoke a system call)
>>>>>>>>>>>>
>>>>>>>>>>>> 2. It would be nice to have metrics, that allow us to check the
>>>>> cause
>>>>>>>>> of
>>>>>>>>>>>> back pressure:
>>>>>>>>>>>> a) for sources, length of input queue (in bytes? Or boolean
>>>>>>>>>>>> hasSomethingl/isEmpty)
>>>>>>>>>>>> b) for sinks, length of output queue (in bytes? Or boolean
>>>>>>>>>>>> hasSomething/isEmpty)
>>>>>>>>>>>>
>>>>>>>>>>>> a) is useful in a scenario when we are processing backlog of
>>>>> records,
>>>>>>>>> all
>>>>>>>>>>>> of the internal Flink’s input/output network buffers are empty,
>>>>> and
>>>>>>> we
>>>>>>>>> want
>>>>>>>>>>>> to check whether the external source system is the bottleneck
>>>>>>> (source’s
>>>>>>>>>>>> input queue will be empty), or if the Flink’s connector is the
>>>>>>>>> bottleneck
>>>>>>>>>>>> (source’s input queues will be full).
>>>>>>>>>>>> b) similar story. Backlog of records, but this time all of the
>>>>>>> internal
>>>>>>>>>>>> Flink’s input/ouput network buffers are full, and we want o
>> check
>>>>>>>>> whether
>>>>>>>>>>>> the external sink system is the bottleneck (sink output queues
>> are
>>>>>>>>> full),
>>>>>>>>>>>> or if the Flink’s connector is the bottleneck (sink’s output
>>>>> queues
>>>>>>>>> will be
>>>>>>>>>>>> empty)
>>>>>>>>>>>>
>>>>>>>>>>>> It might be sometimes difficult to provide those metrics, so
>> they
>>>>>>> could
>>>>>>>>>>>> be optional, but if we could provide them, it would be really
>>>>>>> helpful.
>>>>>>>>>>>>
>>>>>>>>>>>> Piotrek
>>>>>>>>>>>>
>>>>>>>>>>>> [1]
>>>>>>>>>>>>
>>>>>>>>>
>>>>>>>
>>>>>
>> https://cwiki.apache.org/confluence/display/FLINK/FLIP-33:+Standardize+Connector+Metrics
>>>>>>>>>>>> <
>>>>>>>>>>>>
>>>>>>>>>
>>>>>>>
>>>>>
>> https://cwiki.apache.org/confluence/display/FLINK/FLIP-33:+Standardize+Connector+Metrics
>>>>>>>>>>>>>
>>>>>>>>>>>>
>>>>>>>>>>>>> On 24 Apr 2019, at 13:28, Stephan Ewen <se...@apache.org>
>> wrote:
>>>>>>>>>>>>>
>>>>>>>>>>>>> I think this sounds reasonable.
>>>>>>>>>>>>>
>>>>>>>>>>>>> Let's keep the "reconfiguration without stopping the job" out
>> of
>>>>>>> this,
>>>>>>>>>>>>> because that would be a super big effort and if we approach
>> that,
>>>>>>> then
>>>>>>>>>>>> in
>>>>>>>>>>>>> more generic way rather than specific to connector metrics.
>>>>>>>>>>>>>
>>>>>>>>>>>>> I would suggest to look at the following things before starting
>>>>> with
>>>>>>>>> any
>>>>>>>>>>>>> implementation work:
>>>>>>>>>>>>>
>>>>>>>>>>>>> - Try and find a committer to support this, otherwise it will
>> be
>>>>>>> hard
>>>>>>>>>>>> to
>>>>>>>>>>>>> make progress
>>>>>>>>>>>>> - Start with defining a smaller set of "core metrics" and
>> extend
>>>>> the
>>>>>>>>>>>> set
>>>>>>>>>>>>> later. I think that is easier than now blocking on reaching
>>>>>>> consensus
>>>>>>>>>>>> on a
>>>>>>>>>>>>> large group of metrics.
>>>>>>>>>>>>> - Find a solution to the problem Chesnay mentioned, that the
>>>>>>> "records
>>>>>>>>>>>> in"
>>>>>>>>>>>>> metric is somehow overloaded and exists already in the IO
>> Metric
>>>>>>>>> group.
>>>>>>>>>>>>>
>>>>>>>>>>>>>
>>>>>>>>>>>>> On Mon, Mar 25, 2019 at 7:16 AM Becket Qin <
>> becket.qin@gmail.com
>>>>>>
>>>>>>>>>>>> wrote:
>>>>>>>>>>>>>
>>>>>>>>>>>>>> Hi Stephan,
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> Thanks a lot for the feedback. All makes sense.
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> It is a good suggestion to simply have an onRecord(numBytes,
>>>>>>>>> eventTime)
>>>>>>>>>>>>>> method for connector writers. It should meet most of the
>>>>>>>>> requirements,
>>>>>>>>>>>>>> individual
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> The configurable metrics feature is something really useful,
>>>>>>>>>>>> especially if
>>>>>>>>>>>>>> we can somehow make it dynamically configurable without
>> stopping
>>>>>>> the
>>>>>>>>>>>> jobs.
>>>>>>>>>>>>>> It might be better to make it a separate discussion because it
>>>>> is a
>>>>>>>>>>>> more
>>>>>>>>>>>>>> generic feature instead of only for connectors.
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> So in order to make some progress, in this FLIP we can limit
>> the
>>>>>>>>>>>> discussion
>>>>>>>>>>>>>> scope to the connector related items:
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> - the standard connector metric names and types.
>>>>>>>>>>>>>> - the abstract ConnectorMetricHandler interface
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> I'll start a separate thread to discuss other general metric
>>>>>>> related
>>>>>>>>>>>>>> enhancement items including:
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> - optional metrics
>>>>>>>>>>>>>> - dynamic metric configuration
>>>>>>>>>>>>>> - potential combination with rate limiter
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> Does this plan sound reasonable?
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> Thanks,
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> Jiangjie (Becket) Qin
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> On Sat, Mar 23, 2019 at 5:53 AM Stephan Ewen <
>> sewen@apache.org>
>>>>>>>>> wrote:
>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> Ignoring for a moment implementation details, this connector
>>>>>>> metrics
>>>>>>>>>>>> work
>>>>>>>>>>>>>>> is a really good thing to do, in my opinion
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> The questions "oh, my job seems to be doing nothing, I am
>>>>> looking
>>>>>>> at
>>>>>>>>>>>> the
>>>>>>>>>>>>>> UI
>>>>>>>>>>>>>>> and the 'records in' value is still zero" is in the top three
>>>>>>>>> support
>>>>>>>>>>>>>>> questions I have been asked personally.
>>>>>>>>>>>>>>> Introspection into "how far is the consumer lagging behind"
>>>>> (event
>>>>>>>>>>>> time
>>>>>>>>>>>>>>> fetch latency) came up many times as well.
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> So big +1 to solving this problem.
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> About the exact design - I would try to go for the following
>>>>>>>>>>>> properties:
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> - keep complexity of of connectors. Ideally the metrics
>> handler
>>>>>>> has
>>>>>>>>> a
>>>>>>>>>>>>>>> single onRecord(numBytes, eventTime) method or so, and
>>>>> everything
>>>>>>>>>>>> else is
>>>>>>>>>>>>>>> internal to the handler. That makes it dead simple for the
>>>>>>>>> connector.
>>>>>>>>>>>> We
>>>>>>>>>>>>>>> can also think of an extensive scheme for connector specific
>>>>>>>>> metrics.
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> - make it configurable on the job it cluster level which
>>>>> metrics
>>>>>>> the
>>>>>>>>>>>>>>> handler internally creates when that method is invoked.
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> What do you think?
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> Best,
>>>>>>>>>>>>>>> Stephan
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> On Thu, Mar 21, 2019 at 10:42 AM Chesnay Schepler <
>>>>>>>>> chesnay@apache.org
>>>>>>>>>>>>>
>>>>>>>>>>>>>>> wrote:
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>> As I said before, I believe this to be over-engineered and
>>>>> have
>>>>>>> no
>>>>>>>>>>>>>>>> interest in this implementation.
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>> There are conceptual issues like defining a duplicate
>>>>>>>>>>>>>> numBytesIn(PerSec)
>>>>>>>>>>>>>>>> metric that already exists for each operator.
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>> On 21.03.2019 06:13, Becket Qin wrote:
>>>>>>>>>>>>>>>>> A few updates to the thread. I uploaded a patch[1] as a
>>>>> complete
>>>>>>>>>>>>>>>>> example of how users can use the metrics in the future.
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>> Some thoughts below after taking a look at the
>>>>>>> AbstractMetricGroup
>>>>>>>>>>>>>> and
>>>>>>>>>>>>>>>>> its subclasses.
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>> This patch intends to provide convenience for Flink
>> connector
>>>>>>>>>>>>>>>>> implementations to follow metrics standards proposed in
>>>>> FLIP-33.
>>>>>>>>> It
>>>>>>>>>>>>>>>>> also try to enhance the metric management in general way to
>>>>> help
>>>>>>>>>>>>>> users
>>>>>>>>>>>>>>>>> with:
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>> 1. metric definition
>>>>>>>>>>>>>>>>> 2. metric dependencies check
>>>>>>>>>>>>>>>>> 3. metric validation
>>>>>>>>>>>>>>>>> 4. metric control (turn on / off particular metrics)
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>> This patch wraps |MetricGroup| to extend the functionality
>> of
>>>>>>>>>>>>>>>>> |AbstractMetricGroup| and its subclasses. The
>>>>>>>>>>>>>>>>> |AbstractMetricGroup| mainly focus on the metric group
>>>>>>> hierarchy,
>>>>>>>>>>>> but
>>>>>>>>>>>>>>>>> does not really manage the metrics other than keeping them
>>>>> in a
>>>>>>>>> Map.
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>> Ideally we should only have one entry point for the
>> metrics.
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>> Right now the entry point is |AbstractMetricGroup|.
>> However,
>>>>>>>>> besides
>>>>>>>>>>>>>>>>> the missing functionality mentioned above,
>>>>> |AbstractMetricGroup|
>>>>>>>>>>>>>> seems
>>>>>>>>>>>>>>>>> deeply rooted in Flink runtime. We could extract it out to
>>>>>>>>>>>>>>>>> flink-metrics in order to use it for generic purpose. There
>>>>> will
>>>>>>>>> be
>>>>>>>>>>>>>>>>> some work, though.
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>> Another approach is to make |AbstractMetrics| in this patch
>>>>> as
>>>>>>> the
>>>>>>>>>>>>>>>>> metric entry point. It wraps metric group and provides the
>>>>>>> missing
>>>>>>>>>>>>>>>>> functionalities. Then we can roll out this pattern to
>> runtime
>>>>>>>>>>>>>>>>> components gradually as well.
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>> My first thought is that the latter approach gives a more
>>>>> smooth
>>>>>>>>>>>>>>>>> migration. But I am also OK with doing a refactoring on the
>>>>>>>>>>>>>>>>> |AbstractMetricGroup| family.
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>> Thanks,
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>> Jiangjie (Becket) Qin
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>> [1] https://github.com/becketqin/flink/pull/1
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>> On Mon, Feb 25, 2019 at 2:32 PM Becket Qin <
>>>>>>> becket.qin@gmail.com
>>>>>>>>>>>>>>>>> <ma...@gmail.com>> wrote:
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>> Hi Chesnay,
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>> It might be easier to discuss some implementation details
>> in
>>>>>>> the
>>>>>>>>>>>>>>>>> PR review instead of in the FLIP discussion thread. I have
>> a
>>>>>>>>>>>>>> patch
>>>>>>>>>>>>>>>>> for Kafka connectors ready but haven't submitted the PR
>> yet.
>>>>>>>>>>>>>>>>> Hopefully that will help explain a bit more.
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>> ** Re: metric type binding
>>>>>>>>>>>>>>>>> This is a valid point that worths discussing. If I
>> understand
>>>>>>>>>>>>>>>>> correctly, there are two points:
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>> 1. Metric type / interface does not matter as long as the
>>>>>>> metric
>>>>>>>>>>>>>>>>> semantic is clearly defined.
>>>>>>>>>>>>>>>>> Conceptually speaking, I agree that as long as the metric
>>>>>>>>>>>>>> semantic
>>>>>>>>>>>>>>>>> is defined, metric type does not matter. To some extent,
>>>>> Gauge
>>>>>>> /
>>>>>>>>>>>>>>>>> Counter / Meter / Histogram themselves can be think of as
>>>>> some
>>>>>>>>>>>>>>>>> well-recognized semantics, if you wish. In Flink, these
>>>>> metric
>>>>>>>>>>>>>>>>> semantics have their associated interface classes. In
>>>>> practice,
>>>>>>>>>>>>>>>>> such semantic to interface binding seems necessary for
>>>>>>> different
>>>>>>>>>>>>>>>>> components to communicate. Simply standardize the semantic
>>>>> of
>>>>>>>>>>>>>> the
>>>>>>>>>>>>>>>>> connector metrics seems not sufficient for people to build
>>>>>>>>>>>>>>>>> ecosystem on top of. At the end of the day, we still need
>> to
>>>>>>>>> have
>>>>>>>>>>>>>>>>> some embodiment of the metric semantics that people can
>>>>> program
>>>>>>>>>>>>>>>>> against.
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>> 2. Sometimes the same metric semantic can be exposed using
>>>>>>>>>>>>>>>>> different metric types / interfaces.
>>>>>>>>>>>>>>>>> This is a good point. Counter and Gauge-as-a-Counter are
>>>>> pretty
>>>>>>>>>>>>>>>>> much interchangeable. This is more of a trade-off between
>> the
>>>>>>>>>>>>>> user
>>>>>>>>>>>>>>>>> experience of metric producers and consumers. The metric
>>>>>>>>>>>>>> producers
>>>>>>>>>>>>>>>>> want to use Counter or Gauge depending on whether the
>> counter
>>>>>>> is
>>>>>>>>>>>>>>>>> already tracked in code, while ideally the metric consumers
>>>>>>> only
>>>>>>>>>>>>>>>>> want to see a single metric type for each metric. I am
>>>>> leaning
>>>>>>>>>>>>>>>>> towards to make the metric producers happy, i.e. allow
>> Gauge
>>>>> /
>>>>>>>>>>>>>>>>> Counter metric type, and the the metric consumers handle
>> the
>>>>>>>>> type
>>>>>>>>>>>>>>>>> variation. The reason is that in practice, there might be
>>>>> more
>>>>>>>>>>>>>>>>> connector implementations than metric reporter
>>>>> implementations.
>>>>>>>>>>>>>> We
>>>>>>>>>>>>>>>>> could also provide some helper method to facilitate reading
>>>>>>> from
>>>>>>>>>>>>>>>>> such variable metric type.
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>> Just some quick replies to the comments around
>> implementation
>>>>>>>>>>>>>>>> details.
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>> 4) single place where metrics are registered except
>>>>>>>>>>>>>>>>> connector-specific
>>>>>>>>>>>>>>>>> ones (which we can't really avoid).
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>> Register connector specific ones in a single place is
>>>>> actually
>>>>>>>>>>>>>>>>> something that I want to achieve.
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>> 2) I'm talking about time-series databases like
>>>>> Prometheus.
>>>>>>>>>>>>>> We
>>>>>>>>>>>>>>>>> would
>>>>>>>>>>>>>>>>> only have a gauge metric exposing the last
>>>>>>>>> fetchTime/emitTime
>>>>>>>>>>>>>>>>> that is
>>>>>>>>>>>>>>>>> regularly reported to the backend (Prometheus), where a
>>>>>>> user
>>>>>>>>>>>>>>>>> could build
>>>>>>>>>>>>>>>>> a histogram of his choosing when/if he wants it.
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>> Not sure if such downsampling works. As an example, if a
>> user
>>>>>>>>>>>>>>>>> complains that there are some intermittent latency spikes
>>>>>>> (maybe
>>>>>>>>>>>>>> a
>>>>>>>>>>>>>>>>> few records in 10 seconds) in their processing system.
>>>>> Having a
>>>>>>>>>>>>>>>>> Gauge sampling instantaneous latency seems unlikely useful.
>>>>>>>>>>>>>>>>> However by looking at actual 99.9 percentile latency might
>>>>>>> help.
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>> Thanks,
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>> Jiangjie (Becket) Qin
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>> On Fri, Feb 22, 2019 at 9:30 PM Chesnay Schepler
>>>>>>>>>>>>>>>>> <chesnay@apache.org <ma...@apache.org>> wrote:
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>> Re: over complication of implementation.
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>> I think I get understand better know what you're
>> shooting
>>>>>>>>>>>>>> for,
>>>>>>>>>>>>>>>>> effectively something like the OperatorIOMetricGroup.
>>>>>>>>>>>>>>>>> But still, re-define setupConnectorMetrics() to accept a
>>>>>>> set
>>>>>>>>>>>>>>>>> of flags
>>>>>>>>>>>>>>>>> for counters/meters(ans _possibly_ histograms) along
>>>>> with a
>>>>>>>>>>>>>>>>> set of
>>>>>>>>>>>>>>>>> well-defined Optional<Gauge<?>>, and return the group.
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>> Solves all issues as far as i can tell:
>>>>>>>>>>>>>>>>> 1) no metrics must be created manually (except Gauges,
>>>>>>> which
>>>>>>>>>>>>>>> are
>>>>>>>>>>>>>>>>> effectively just Suppliers and you can't get around
>>>>> this),
>>>>>>>>>>>>>>>>> 2) additional metrics can be registered on the returned
>>>>>>>>>>>>>> group,
>>>>>>>>>>>>>>>>> 3) see 1),
>>>>>>>>>>>>>>>>> 4) single place where metrics are registered except
>>>>>>>>>>>>>>>>> connector-specific
>>>>>>>>>>>>>>>>> ones (which we can't really avoid).
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>> Re: Histogram
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>> 1) As an example, whether "numRecordsIn" is exposed as a
>>>>>>>>>>>>>>>>> Counter or a
>>>>>>>>>>>>>>>>> Gauge should be irrelevant. So far we're using the
>> metric
>>>>>>>>>>>>>> type
>>>>>>>>>>>>>>>>> that is
>>>>>>>>>>>>>>>>> the most convenient at exposing a given value. If there
>>>>> is
>>>>>>>>>>>>>>>>> some backing
>>>>>>>>>>>>>>>>> data-structure that we want to expose some data from we
>>>>>>>>>>>>>>>>> typically opt
>>>>>>>>>>>>>>>>> for a Gauge, as otherwise we're just mucking around with
>>>>>>> the
>>>>>>>>>>>>>>>>> Meter/Counter API to get it to match. Similarly, if we
>>>>> want
>>>>>>>>>>>>>> to
>>>>>>>>>>>>>>>>> count
>>>>>>>>>>>>>>>>> something but no current count exists we typically added
>>>>> a
>>>>>>>>>>>>>>>>> Counter.
>>>>>>>>>>>>>>>>> That's why attaching semantics to metric types makes
>>>>> little
>>>>>>>>>>>>>>>>> sense (but
>>>>>>>>>>>>>>>>> unfortunately several reporters already do it); for
>>>>>>>>>>>>>>>>> counters/meters
>>>>>>>>>>>>>>>>> certainly, but the majority of metrics are gauges.
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>> 2) I'm talking about time-series databases like
>>>>> Prometheus.
>>>>>>>>>>>>>> We
>>>>>>>>>>>>>>>>> would
>>>>>>>>>>>>>>>>> only have a gauge metric exposing the last
>>>>>>>>> fetchTime/emitTime
>>>>>>>>>>>>>>>>> that is
>>>>>>>>>>>>>>>>> regularly reported to the backend (Prometheus), where a
>>>>>>> user
>>>>>>>>>>>>>>>>> could build
>>>>>>>>>>>>>>>>> a histogram of his choosing when/if he wants it.
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>> On 22.02.2019 13:57, Becket Qin wrote:
>>>>>>>>>>>>>>>>>> Hi Chesnay,
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> Thanks for the explanation.
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> ** Re: FLIP
>>>>>>>>>>>>>>>>>> I might have misunderstood this, but it seems that "major
>>>>>>>>>>>>>>>>> changes" are well
>>>>>>>>>>>>>>>>>> defined in FLIP. The full contents is following:
>>>>>>>>>>>>>>>>>> What is considered a "major change" that needs a FLIP?
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> Any of the following should be considered a major change:
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> - Any major new feature, subsystem, or piece of
>>>>>>>>>>>>>>>>> functionality
>>>>>>>>>>>>>>>>>> - *Any change that impacts the public interfaces of the
>>>>>>>>>>>>>>>>> project*
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> What are the "public interfaces" of the project?
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> *All of the following are public interfaces *that people
>>>>>>>>>>>>>>>>> build around:
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> - DataStream and DataSet API, including classes related
>>>>>>>>>>>>>>>>> to that, such as
>>>>>>>>>>>>>>>>>> StreamExecutionEnvironment
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> - Classes marked with the @Public annotation
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> - On-disk binary formats, such as
>>>>>>>>>>>>>> checkpoints/savepoints
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> - User-facing scripts/command-line tools, i.e.
>>>>>>>>>>>>>>>>> bin/flink, Yarn scripts,
>>>>>>>>>>>>>>>>>> Mesos scripts
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> - Configuration settings
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> - *Exposed monitoring information*
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> So any monitoring information change is considered as
>>>>>>>>>>>>>> public
>>>>>>>>>>>>>>>>> interface, and
>>>>>>>>>>>>>>>>>> any public interface change is considered as a "major
>>>>>>>>>>>>>>> change".
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> ** Re: over complication of implementation.
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> Although this is more of implementation details that is
>> not
>>>>>>>>>>>>>>>>> covered by the
>>>>>>>>>>>>>>>>>> FLIP. But it may be worth discussing.
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> First of all, I completely agree that we should use the
>>>>>>>>>>>>>>>>> simplest way to
>>>>>>>>>>>>>>>>>> achieve our goal. To me the goal is the following:
>>>>>>>>>>>>>>>>>> 1. Clear connector conventions and interfaces.
>>>>>>>>>>>>>>>>>> 2. The easiness of creating a connector.
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> Both of them are important to the prosperity of the
>>>>>>>>>>>>>>>>> connector ecosystem. So
>>>>>>>>>>>>>>>>>> I'd rather abstract as much as possible on our side to
>> make
>>>>>>>>>>>>>>>>> the connector
>>>>>>>>>>>>>>>>>> developer's work lighter. Given this goal, a static util
>>>>>>>>>>>>>>>>> method approach
>>>>>>>>>>>>>>>>>> might have a few drawbacks:
>>>>>>>>>>>>>>>>>> 1. Users still have to construct the metrics by
>> themselves.
>>>>>>>>>>>>>>>>> (And note that
>>>>>>>>>>>>>>>>>> this might be erroneous by itself. For example, a customer
>>>>>>>>>>>>>>>>> wrapper around
>>>>>>>>>>>>>>>>>> dropwizard meter maybe used instead of MeterView).
>>>>>>>>>>>>>>>>>> 2. When connector specific metrics are added, it is
>>>>>>>>>>>>>>>>> difficult to enforce
>>>>>>>>>>>>>>>>>> the scope to be the same as standard metrics.
>>>>>>>>>>>>>>>>>> 3. It seems that a method proliferation is inevitable if
>> we
>>>>>>>>>>>>>>>>> want to apply
>>>>>>>>>>>>>>>>>> sanity checks. e.g. The metric of numBytesIn was not
>>>>>>>>>>>>>>>>> registered for a meter.
>>>>>>>>>>>>>>>>>> 4. Metrics are still defined in random places and hard to
>>>>>>>>>>>>>>>> track.
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> The current PR I had was inspired by the Config system in
>>>>>>>>>>>>>>>>> Kafka, which I
>>>>>>>>>>>>>>>>>> found pretty handy. In fact it is not only used by Kafka
>>>>>>>>>>>>>>>>> itself but even
>>>>>>>>>>>>>>>>>> some other projects that depend on Kafka. I am not saying
>>>>>>>>>>>>>>>>> this approach is
>>>>>>>>>>>>>>>>>> perfect. But I think it worths to save the work for
>>>>>>>>>>>>>>>>> connector writers and
>>>>>>>>>>>>>>>>>> encourage more systematic implementation. That being said,
>>>>>>>>>>>>>> I
>>>>>>>>>>>>>>>>> am fully open
>>>>>>>>>>>>>>>>>> to suggestions.
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> Re: Histogram
>>>>>>>>>>>>>>>>>> I think there are two orthogonal questions around those
>>>>>>>>>>>>>>>> metrics:
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> 1. Regardless of the metric type, by just looking at the
>>>>>>>>>>>>>>>>> meaning of a
>>>>>>>>>>>>>>>>>> metric, is generic to all connectors? If the answer is
>> yes,
>>>>>>>>>>>>>>>>> we should
>>>>>>>>>>>>>>>>>> include the metric into the convention. No matter whether
>>>>>>>>>>>>>> we
>>>>>>>>>>>>>>>>> include it
>>>>>>>>>>>>>>>>>> into the convention or not, some connector implementations
>>>>>>>>>>>>>>>>> will emit such
>>>>>>>>>>>>>>>>>> metric. It is better to have a convention than letting
>> each
>>>>>>>>>>>>>>>>> connector do
>>>>>>>>>>>>>>>>>> random things.
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> 2. If a standard metric is a histogram, what should we do?
>>>>>>>>>>>>>>>>>> I agree that we should make it clear that using histograms
>>>>>>>>>>>>>>>>> will have
>>>>>>>>>>>>>>>>>> performance risk. But I do see histogram is useful in some
>>>>>>>>>>>>>>>>> fine-granularity
>>>>>>>>>>>>>>>>>> debugging where one do not have the luxury to stop the
>>>>>>>>>>>>>>>>> system and inject
>>>>>>>>>>>>>>>>>> more inspection code. So the workaround I am thinking is
>> to
>>>>>>>>>>>>>>>>> provide some
>>>>>>>>>>>>>>>>>> implementation suggestions. Assume later on we have a
>>>>>>>>>>>>>>>>> mechanism of
>>>>>>>>>>>>>>>>>> selective metrics. In the abstract metrics class we can
>>>>>>>>>>>>>>>>> disable those
>>>>>>>>>>>>>>>>>> metrics by default individual connector writers does not
>>>>>>>>>>>>>>>>> have to do
>>>>>>>>>>>>>>>>>> anything (this is another advantage of having an
>>>>>>>>>>>>>>>>> AbstractMetrics instead of
>>>>>>>>>>>>>>>>>> static util methods.)
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> I am not sure I fully understand the histogram in the
>>>>>>>>>>>>>>>>> backend approach. Can
>>>>>>>>>>>>>>>>>> you explain a bit more? Do you mean emitting the raw data,
>>>>>>>>>>>>>>>>> e.g. fetchTime
>>>>>>>>>>>>>>>>>> and emitTime with each record and let the histogram
>>>>>>>>>>>>>>>>> computation happen in
>>>>>>>>>>>>>>>>>> the background? Or let the processing thread putting the
>>>>>>>>>>>>>>>>> values into a
>>>>>>>>>>>>>>>>>> queue and have a separate thread polling from the queue
>> and
>>>>>>>>>>>>>>>>> add them into
>>>>>>>>>>>>>>>>>> the histogram?
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> Thanks,
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> Jiangjie (Becket) Qin
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> On Fri, Feb 22, 2019 at 4:34 PM Chesnay Schepler
>>>>>>>>>>>>>>>>> <chesnay@apache.org <ma...@apache.org>> wrote:
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>> Re: Flip
>>>>>>>>>>>>>>>>>>> The very first line under both the main header and
>> Purpose
>>>>>>>>>>>>>>>>> section
>>>>>>>>>>>>>>>>>>> describe Flips as "major changes", which this isn't.
>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>> Re: complication
>>>>>>>>>>>>>>>>>>> I'm not arguing against standardization, but again an
>>>>>>>>>>>>>>>>> over-complicated
>>>>>>>>>>>>>>>>>>> implementation when a static utility method would be
>>>>>>>>>>>>>>>>> sufficient.
>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>> public static void setupConnectorMetrics(
>>>>>>>>>>>>>>>>>>> MetricGroup operatorMetricGroup,
>>>>>>>>>>>>>>>>>>> String connectorName,
>>>>>>>>>>>>>>>>>>> Optional<Gauge<Long>> numRecordsIn,
>>>>>>>>>>>>>>>>>>> ...)
>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>> This gives you all you need:
>>>>>>>>>>>>>>>>>>> * a well-defined set of metrics for a connector to opt-in
>>>>>>>>>>>>>>>>>>> * standardized naming schemes for scope and individual
>>>>>>>>>>>>>>> metrics
>>>>>>>>>>>>>>>>>>> * standardize metric types (although personally I'm not
>>>>>>>>>>>>>>>>> interested in that
>>>>>>>>>>>>>>>>>>> since metric types should be considered syntactic sugar)
>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>> Re: Configurable Histogram
>>>>>>>>>>>>>>>>>>> If anything they _must_ be turned off by default, but the
>>>>>>>>>>>>>>>>> metric system is
>>>>>>>>>>>>>>>>>>> already exposing so many options that I'm not too keen on
>>>>>>>>>>>>>>>>> adding even more.
>>>>>>>>>>>>>>>>>>> You have also only addressed my first argument against
>>>>>>>>>>>>>>>>> histograms
>>>>>>>>>>>>>>>>>>> (performance), the second one still stands (calculate
>>>>>>>>>>>>>>>>> histogram in metric
>>>>>>>>>>>>>>>>>>> backends instead).
>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>> On 21.02.2019 16:27, Becket Qin wrote:
>>>>>>>>>>>>>>>>>>>> Hi Chesnay,
>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>> Thanks for the comments. I think this is worthy of a
>> FLIP
>>>>>>>>>>>>>>>>> because it is
>>>>>>>>>>>>>>>>>>>> public API. According to the FLIP description a FlIP is
>>>>>>>>>>>>>>>>> required in case
>>>>>>>>>>>>>>>>>>> of:
>>>>>>>>>>>>>>>>>>>> - Any change that impacts the public interfaces of
>>>>>>>>>>>>>>>>> the project
>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>> and the following entry is found in the definition of
>>>>>>>>>>>>>>>>> "public interface".
>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>> - Exposed monitoring information
>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>> Metrics are critical to any production system. So a
>> clear
>>>>>>>>>>>>>>>>> metric
>>>>>>>>>>>>>>>>>>> definition
>>>>>>>>>>>>>>>>>>>> is important for any serious users. For an organization
>>>>>>>>>>>>>>>>> with large Flink
>>>>>>>>>>>>>>>>>>>> installation, change in metrics means great amount of
>>>>>>>>>>>>>>>>> work. So such
>>>>>>>>>>>>>>>>>>> changes
>>>>>>>>>>>>>>>>>>>> do need to be fully discussed and documented.
>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>> ** Re: Histogram.
>>>>>>>>>>>>>>>>>>>> We can discuss whether there is a better way to expose
>>>>>>>>>>>>>>>>> metrics that are
>>>>>>>>>>>>>>>>>>>> suitable for histograms. My micro-benchmark on various
>>>>>>>>>>>>>>>>> histogram
>>>>>>>>>>>>>>>>>>>> implementations also indicates that they are
>>>>>>>>>>>>>> significantly
>>>>>>>>>>>>>>>>> slower than
>>>>>>>>>>>>>>>>>>>> other metric types. But I don't think that means never
>>>>>>>>>>>>>> use
>>>>>>>>>>>>>>>>> histogram, but
>>>>>>>>>>>>>>>>>>>> means use it with caution. For example, we can suggest
>>>>>>>>>>>>>> the
>>>>>>>>>>>>>>>>>>> implementations
>>>>>>>>>>>>>>>>>>>> to turn them off by default and only turn it on for a
>>>>>>>>>>>>>>>>> small amount of
>>>>>>>>>>>>>>>>>>> time
>>>>>>>>>>>>>>>>>>>> when performing some micro-debugging.
>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>> ** Re: complication:
>>>>>>>>>>>>>>>>>>>> Connector conventions are essential for Flink ecosystem.
>>>>>>>>>>>>>>>>> Flink connectors
>>>>>>>>>>>>>>>>>>>> pool is probably the most important part of Flink, just
>>>>>>>>>>>>>>>>> like any other
>>>>>>>>>>>>>>>>>>> data
>>>>>>>>>>>>>>>>>>>> system. Clear conventions of connectors will help build
>>>>>>>>>>>>>>>>> Flink ecosystem
>>>>>>>>>>>>>>>>>>> in
>>>>>>>>>>>>>>>>>>>> a more organic way.
>>>>>>>>>>>>>>>>>>>> Take the metrics convention as an example, imagine
>>>>>>>>>>>>>> someone
>>>>>>>>>>>>>>>>> has developed
>>>>>>>>>>>>>>>>>>> a
>>>>>>>>>>>>>>>>>>>> Flink connector for System foo, and another developer
>> may
>>>>>>>>>>>>>>>>> have developed
>>>>>>>>>>>>>>>>>>> a
>>>>>>>>>>>>>>>>>>>> monitoring and diagnostic framework for Flink which
>>>>>>>>>>>>>>>>> analyzes the Flink
>>>>>>>>>>>>>>>>>>> job
>>>>>>>>>>>>>>>>>>>> performance based on metrics. With a clear metric
>>>>>>>>>>>>>>>>> convention, those two
>>>>>>>>>>>>>>>>>>>> projects could be developed independently. Once users
>> put
>>>>>>>>>>>>>>>>> them together,
>>>>>>>>>>>>>>>>>>>> it would work without additional modifications. This
>>>>>>>>>>>>>>>>> cannot be easily
>>>>>>>>>>>>>>>>>>>> achieved by just defining a few constants.
>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>> ** Re: selective metrics:
>>>>>>>>>>>>>>>>>>>> Sure, we can discuss that in a separate thread.
>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>> @Dawid
>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>> ** Re: latency / fetchedLatency
>>>>>>>>>>>>>>>>>>>> The primary purpose of establish such a convention is to
>>>>>>>>>>>>>>>>> help developers
>>>>>>>>>>>>>>>>>>>> write connectors in a more compatible way. The
>> convention
>>>>>>>>>>>>>>>>> is supposed to
>>>>>>>>>>>>>>>>>>> be
>>>>>>>>>>>>>>>>>>>> defined more proactively. So when look at the
>> convention,
>>>>>>>>>>>>>>>>> it seems more
>>>>>>>>>>>>>>>>>>>> important to see if the concept is applicable to
>>>>>>>>>>>>>>>>> connectors in general.
>>>>>>>>>>>>>>>>>>> It
>>>>>>>>>>>>>>>>>>>> might be true so far only Kafka connector reports
>>>>>>>>>>>>>> latency.
>>>>>>>>>>>>>>>>> But there
>>>>>>>>>>>>>>>>>>> might
>>>>>>>>>>>>>>>>>>>> be hundreds of other connector implementations in the
>>>>>>>>>>>>>>>>> Flink ecosystem,
>>>>>>>>>>>>>>>>>>>> though not in the Flink repo, and some of them also
>> emits
>>>>>>>>>>>>>>>>> latency. I
>>>>>>>>>>>>>>>>>>> think
>>>>>>>>>>>>>>>>>>>> a lot of other sources actually also has an append
>>>>>>>>>>>>>>>>> timestamp. e.g.
>>>>>>>>>>>>>>>>>>> database
>>>>>>>>>>>>>>>>>>>> bin logs and some K-V stores. So I wouldn't be surprised
>>>>>>>>>>>>>>>>> if some database
>>>>>>>>>>>>>>>>>>>> connector can also emit latency metrics.
>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>> Thanks,
>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>> Jiangjie (Becket) Qin
>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>> On Thu, Feb 21, 2019 at 10:14 PM Chesnay Schepler
>>>>>>>>>>>>>>>>> <chesnay@apache.org <ma...@apache.org>>
>>>>>>>>>>>>>>>>>>>> wrote:
>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>> Regarding 2) It doesn't make sense to investigate this
>>>>>>>>>>>>>> as
>>>>>>>>>>>>>>>>> part of this
>>>>>>>>>>>>>>>>>>>>> FLIP. This is something that could be of interest for
>>>>>>>>>>>>>> the
>>>>>>>>>>>>>>>>> entire metric
>>>>>>>>>>>>>>>>>>>>> system, and should be designed for as such.
>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>> Regarding the proposal as a whole:
>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>> Histogram metrics shall not be added to the core of
>>>>>>>>>>>>>>>>> Flink. They are
>>>>>>>>>>>>>>>>>>>>> significantly more expensive than other metrics, and
>>>>>>>>>>>>>>>>> calculating
>>>>>>>>>>>>>>>>>>>>> histograms in the application is regarded as an
>>>>>>>>>>>>>>>>> anti-pattern by several
>>>>>>>>>>>>>>>>>>>>> metric backends, who instead recommend to expose the
>> raw
>>>>>>>>>>>>>>>>> data and
>>>>>>>>>>>>>>>>>>>>> calculate the histogram in the backend.
>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>> Second, this seems overly complicated. Given that we
>>>>>>>>>>>>>>>>> already established
>>>>>>>>>>>>>>>>>>>>> that not all connectors will export all metrics we are
>>>>>>>>>>>>>>>>> effectively
>>>>>>>>>>>>>>>>>>>>> reducing this down to a consistent naming scheme. We
>>>>>>>>>>>>>>>>> don't need anything
>>>>>>>>>>>>>>>>>>>>> sophisticated for that; basically just a few constants
>>>>>>>>>>>>>>>>> that all
>>>>>>>>>>>>>>>>>>>>> connectors use.
>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>> I'm not convinced that this is worthy of a FLIP.
>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>> On 21.02.2019 14:26, Dawid Wysakowicz wrote:
>>>>>>>>>>>>>>>>>>>>>> Hi,
>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>> Ad 1. In general I undestand and I agree. But those
>>>>>>>>>>>>>>>>> particular metrics
>>>>>>>>>>>>>>>>>>>>>> (latency, fetchLatency), right now would only be
>>>>>>>>>>>>>>>>> reported if user uses
>>>>>>>>>>>>>>>>>>>>>> KafkaConsumer with internal timestampAssigner with
>>>>>>>>>>>>>>>>> StreamCharacteristic
>>>>>>>>>>>>>>>>>>>>>> set to EventTime, right? That sounds like a very
>>>>>>>>>>>>>>>>> specific case. I am
>>>>>>>>>>>>>>>>>>> not
>>>>>>>>>>>>>>>>>>>>>> sure if we should introduce a generic metric that will
>>>>>>>>>>>>>> be
>>>>>>>>>>>>>>>>>>>>>> disabled/absent for most of implementations.
>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>> Ad.2 That sounds like an orthogonal issue, that might
>>>>>>>>>>>>>>>>> make sense to
>>>>>>>>>>>>>>>>>>>>>> investigate in the future.
>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>> Best,
>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>> Dawid
>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>> On 21/02/2019 13:20, Becket Qin wrote:
>>>>>>>>>>>>>>>>>>>>>>> Hi Dawid,
>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>> Thanks for the feedback. That makes sense to me.
>> There
>>>>>>>>>>>>>>>>> are two cases
>>>>>>>>>>>>>>>>>>> to
>>>>>>>>>>>>>>>>>>>>> be
>>>>>>>>>>>>>>>>>>>>>>> addressed.
>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>> 1. The metrics are supposed to be a guidance. It is
>>>>>>>>>>>>>>>>> likely that a
>>>>>>>>>>>>>>>>>>>>> connector
>>>>>>>>>>>>>>>>>>>>>>> only supports some but not all of the metrics. In
>> that
>>>>>>>>>>>>>>>>> case, each
>>>>>>>>>>>>>>>>>>>>> connector
>>>>>>>>>>>>>>>>>>>>>>> implementation should have the freedom to decide
>> which
>>>>>>>>>>>>>>>>> metrics are
>>>>>>>>>>>>>>>>>>>>>>> reported. For the metrics that are supported, the
>>>>>>>>>>>>>>>>> guidance should be
>>>>>>>>>>>>>>>>>>>>>>> followed.
>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>> 2. Sometimes users may want to disable certain
>> metrics
>>>>>>>>>>>>>>>>> for some reason
>>>>>>>>>>>>>>>>>>>>>>> (e.g. performance / reprocessing of data). A generic
>>>>>>>>>>>>>>>>> mechanism should
>>>>>>>>>>>>>>>>>>> be
>>>>>>>>>>>>>>>>>>>>>>> provided to allow user choose which metrics are
>>>>>>>>>>>>>>>>> reported. This
>>>>>>>>>>>>>>>>>>> mechanism
>>>>>>>>>>>>>>>>>>>>>>> should also be honored by the connector
>>>>>>>>>>>>>> implementations.
>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>> Does this sound reasonable to you?
>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>> Thanks,
>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>> Jiangjie (Becket) Qin
>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>> On Thu, Feb 21, 2019 at 4:22 PM Dawid Wysakowicz <
>>>>>>>>>>>>>>>>>>>>> dwysakowicz@apache.org <mailto:dwysakowicz@apache.org
>>>>
>>>>>>>>>>>>>>>>>>>>>>> wrote:
>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>>> Hi,
>>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>>> Generally I like the idea of having a unified,
>>>>>>>>>>>>>>>>> standard set of
>>>>>>>>>>>>>>>>>>> metrics
>>>>>>>>>>>>>>>>>>>>> for
>>>>>>>>>>>>>>>>>>>>>>>> all connectors. I have some slight concerns about
>>>>>>>>>>>>>>>>> fetchLatency and
>>>>>>>>>>>>>>>>>>>>>>>> latency though. They are computed based on EventTime
>>>>>>>>>>>>>>>>> which is not a
>>>>>>>>>>>>>>>>>>>>> purely
>>>>>>>>>>>>>>>>>>>>>>>> technical feature. It depends often on some business
>>>>>>>>>>>>>>>>> logic, might be
>>>>>>>>>>>>>>>>>>>>> absent
>>>>>>>>>>>>>>>>>>>>>>>> or defined after source. Those metrics could also
>>>>>>>>>>>>>>>>> behave in a weird
>>>>>>>>>>>>>>>>>>>>> way in
>>>>>>>>>>>>>>>>>>>>>>>> case of replaying backlog. Therefore I am not sure
>> if
>>>>>>>>>>>>>>>>> we should
>>>>>>>>>>>>>>>>>>> include
>>>>>>>>>>>>>>>>>>>>>>>> those metrics by default. Maybe we could at least
>>>>>>>>>>>>>>>>> introduce a feature
>>>>>>>>>>>>>>>>>>>>>>>> switch for them? What do you think?
>>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>>> Best,
>>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>>> Dawid
>>>>>>>>>>>>>>>>>>>>>>>> On 21/02/2019 03:13, Becket Qin wrote:
>>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>>> Bump. If there is no objections to the proposed
>>>>>>>>>>>>>>>>> metrics. I'll start a
>>>>>>>>>>>>>>>>>>>>>>>> voting thread later toady.
>>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>>> Thanks,
>>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>>> Jiangjie (Becket) Qin
>>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>>> On Mon, Feb 11, 2019 at 8:17 PM Becket Qin
>>>>>>>>>>>>>>>>> <becket.qin@gmail.com <ma...@gmail.com>> <
>>>>>>>>>>>>>>>>>>>>> becket.qin@gmail.com <ma...@gmail.com>>
>>>>>>>>>>>>>>> wrote:
>>>>>>>>>>>>>>>>>>>>>>>> Hi folks,
>>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>>> I would like to start the FLIP discussion thread
>>>>>>>>>>>>>> about
>>>>>>>>>>>>>>>>> standardize
>>>>>>>>>>>>>>>>>>> the
>>>>>>>>>>>>>>>>>>>>>>>> connector metrics.
>>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>>> In short, we would like to provide a convention of
>>>>>>>>>>>>>>>>> Flink connector
>>>>>>>>>>>>>>>>>>>>>>>> metrics. It will help simplify the monitoring and
>>>>>>>>>>>>>>>>> alerting on Flink
>>>>>>>>>>>>>>>>>>>>> jobs.
>>>>>>>>>>>>>>>>>>>>>>>> The FLIP link is following:
>>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>
>>>>>>>>>>>>
>>>>>>>>>
>>>>>>>
>>>>>
>> https://cwiki.apache.org/confluence/display/FLINK/FLIP-33%3A+Standardize+Connector+Metrics
>>>>>>>>>>>>>>>>>>>>>>>> Thanks,
>>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>>> Jiangjie (Becket) Qin
>>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>
>>>>>>>>>>>>
>>>>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>
>>>>>
>>
>>
Re: [DISCUSS] FLIP-33: Standardize connector metrics
Posted by Becket Qin <be...@gmail.com>.
Hi Piotr,
That's great to know. Chances are that we will need to revisit the
convention list and adjust them accordingly when FLIP-27 is ready, At that
point we can mark some of the metrics as available by default for
connectors implementing the new interface.
Thanks,
Jiangjie (Becket) Qin
On Thu, Jun 13, 2019 at 3:51 PM Piotr Nowojski <pi...@ververica.com> wrote:
> Thanks for driving this. I’ve just noticed one small thing. With new
> SourceReader interface Flink will be able to provide `idleTime` metric
> automatically.
>
> Piotrek
>
> > On 13 Jun 2019, at 03:30, Becket Qin <be...@gmail.com> wrote:
> >
> > Thanks all for the feedback and discussion.
> >
> > Since there wasn't any concern raised, I've started the voting thread for
> > this FLIP, but please feel free to continue the discussion here if you
> > think something still needs to be addressed.
> >
> > Thanks,
> >
> > Jiangjie (Becket) Qin
> >
> >
> >
> > On Mon, Jun 10, 2019 at 9:10 AM Becket Qin <be...@gmail.com> wrote:
> >
> >> Hi Piotr,
> >>
> >> Thanks for the comments. Yes, you are right. Users will have to look at
> >> other metrics to decide whether the pipeline is healthy or not in the
> first
> >> place before they can use the time-based metric to fix the bottleneck.
> >>
> >> I agree that once we have FLIP-27 ready, some of the metrics can just be
> >> reported by the abstract implementation.
> >>
> >> I've updated FLIP-33 wiki page to add the pendingBytes and
> pendingRecords
> >> metric. Please let me know if you have any concern over the updated
> metric
> >> convention proposal.
> >>
> >> @Chesnay Schepler <ch...@apache.org> @Stephan Ewen
> >> <st...@ververica.com> will you also have time to take a look at the
> >> proposed metric convention? If there is no further concern I'll start a
> >> voting thread for this FLIP in two days.
> >>
> >> Thanks,
> >>
> >> Jiangjie (Becket) Qin
> >>
> >>
> >>
> >> On Wed, Jun 5, 2019 at 6:54 PM Piotr Nowojski <pi...@ververica.com>
> wrote:
> >>
> >>> Hi Becket,
> >>>
> >>> Thanks for the answer :)
> >>>
> >>>> By time-based metric, I meant the portion of time spent on producing
> the
> >>>> record to downstream. For example, a source connector can report that
> >>> it's
> >>>> spending 80% of time to emit record to downstream processing pipeline.
> >>> In
> >>>> another case, a sink connector may report that its spending 30% of
> time
> >>>> producing the records to the external system.
> >>>>
> >>>> This is in some sense equivalent to the buffer usage metric:
> >>>
> >>>> - 80% of time spent on emitting records to downstream ---> downstream
> >>>> node is bottleneck ---> output buffer is probably full.
> >>>> - 30% of time spent on emitting records to downstream ---> downstream
> >>>> node is not bottleneck ---> output buffer is probably not full.
> >>>
> >>> If by “time spent on emitting records to downstream” you understand
> >>> “waiting on back pressure”, then I see your point. And I agree that
> some
> >>> kind of ratio/time based metric gives you more information. However
> under
> >>> “time spent on emitting records to downstream” might be hidden the
> >>> following (extreme) situation:
> >>>
> >>> 1. Job is barely able to handle influx of records, there is 99%
> >>> CPU/resource usage in the cluster, but nobody is
> >>> bottlenecked/backpressured, all output buffers are empty, everybody is
> >>> waiting in 1% of it’s time for more records to process.
> >>> 2. 80% time can still be spent on "down stream operators”, because they
> >>> are the CPU intensive operations, but this doesn’t mean that
> increasing the
> >>> parallelism down the stream will help with anything there. To the
> contrary,
> >>> increasing parallelism of the source operator might help to increase
> >>> resource utilisation up to 100%.
> >>>
> >>> However, this “time based/ratio” approach can be extended to in/output
> >>> buffer usage. Besides collecting an information that input/output
> buffer is
> >>> full/empty, we can probe profile how often are buffer empty/full. If
> output
> >>> buffer is full 1% of times, there is almost no back pressure. If it’s
> full
> >>> 80% of times, there is some back pressure, if it’s full 99.9% of times,
> >>> there is huge back pressure.
> >>>
> >>> Now for autoscaling you could compare the input & output buffers fill
> >>> ratio:
> >>>
> >>> 1. Both are high, the source of bottleneck is down the stream
> >>> 2. Output is low, input is high, this is the bottleneck and the higher
> >>> the difference, the bigger source of bottleneck is this is
> operator/task
> >>> 3. Output is high, input is low - there was some load spike that we are
> >>> currently finishing to process
> >>>
> >>>
> >>>
> >>> But long story short, we are probably diverging from the topic of this
> >>> discussion, and we can discuss this at some later point.
> >>>
> >>> For now, for sources:
> >>>
> >>> as I wrote before, +1 for:
> >>> - pending.bytes, Gauge
> >>> - pending.messages, Gauge
> >>>
> >>> When we will be developing/discussing SourceReader from FLIP-27 we
> might
> >>> then add:
> >>>
> >>> - in-memory.buffer.usage (0 - 100%)
> >>>
> >>> Which will be estimated automatically by Flink while user will be able
> to
> >>> override/provide better estimation.
> >>>
> >>> Piotrek
> >>>
> >>>> On 5 Jun 2019, at 05:42, Becket Qin <be...@gmail.com> wrote:
> >>>>
> >>>> Hi Piotr,
> >>>>
> >>>> Thanks for the explanation. Please see some clarifications below.
> >>>>
> >>>> By time-based metric, I meant the portion of time spent on producing
> the
> >>>> record to downstream. For example, a source connector can report that
> >>> it's
> >>>> spending 80% of time to emit record to downstream processing pipeline.
> >>> In
> >>>> another case, a sink connector may report that its spending 30% of
> time
> >>>> producing the records to the external system.
> >>>>
> >>>> This is in some sense equivalent to the buffer usage metric:
> >>>> - 80% of time spent on emitting records to downstream ---> downstream
> >>>> node is bottleneck ---> output buffer is probably full.
> >>>> - 30% of time spent on emitting records to downstream ---> downstream
> >>>> node is not bottleneck ---> output buffer is probably not full.
> >>>>
> >>>> However, the time-based metric has a few advantages that the buffer
> >>> usage
> >>>> metric may not have.
> >>>>
> >>>> 1. Buffer usage metric may not be applicable to all the connector
> >>>> implementations, while reporting time-based metric are always doable.
> >>>> Some source connectors may not have any input buffer, or they may use
> >>> some
> >>>> third party library that does not expose the input buffer at all.
> >>>> Similarly, for sink connectors, the implementation may not have any
> >>> output
> >>>> buffer, or the third party library does not expose such buffer.
> >>>>
> >>>> 2. Although both type of metrics can detect bottleneck, time-based
> >>> metrics
> >>>> can be used to generate a more informed action to remove the
> bottleneck.
> >>>> For example, when the downstream is bottleneck, the output buffer
> usage
> >>>> metric is likely to be 100%, and the input buffer usage might be 0%.
> >>> That
> >>>> means we don't know what is the suitable parallelism to lift the
> >>>> bottleneck. The time-based metric, on the other hand, would give
> useful
> >>>> information, e.g. if 80% of time was spent on emitting records, we can
> >>>> roughly increase the downstream node parallelism by 4 times.
> >>>>
> >>>> Admittedly, the time-based metrics are more expensive than buffer
> >>> usage. So
> >>>> we may have to do some sampling to reduce the cost. But in general,
> >>> using
> >>>> time-based metrics seems worth adding.
> >>>>
> >>>> That being said, I don't think buffer usage metric and time-based
> >>> metrics
> >>>> are mutually exclusive. We can probably have both. It is just that in
> >>>> practice, features like auto-scaling might prefer time-based metrics
> for
> >>>> the reason stated above.
> >>>>
> >>>>> 1. Define the metrics that would allow us to manually detect
> >>> bottlenecks.
> >>>> As I wrote, we already have them in most of the places, except of
> >>>> sources/sinks.
> >>>>> 2. Use those metrics, to automatically detect bottlenecks. Currently
> we
> >>>> are only automatically detecting back pressure and reporting it to the
> >>> user
> >>>> in web UI (is it exposed as a metric at all?). Detecting the root
> cause
> >>> of
> >>>> the back pressure (bottleneck) is one step further.
> >>>>> 3. Use the knowledge about where exactly the bottleneck is located,
> to
> >>>> try to do something with it.
> >>>>
> >>>> As explained above, I think time-based metric also addresses item 1
> and
> >>>> item 2.
> >>>>
> >>>> Any thoughts？
> >>>>
> >>>> Thanks,
> >>>>
> >>>> Jiangjie (Becket) Qin
> >>>>
> >>>>
> >>>>
> >>>> On Mon, Jun 3, 2019 at 4:14 PM Piotr Nowojski <pi...@ververica.com>
> >>> wrote:
> >>>>
> >>>>> Hi again :)
> >>>>>
> >>>>>> - pending.bytes, Gauge
> >>>>>> - pending.messages, Gauge
> >>>>>
> >>>>>
> >>>>> +1
> >>>>>
> >>>>> And true, instead of overloading one of the metric it is better when
> >>> user
> >>>>> can choose to provide only one of them.
> >>>>>
> >>>>> Re 2:
> >>>>>
> >>>>>> If I understand correctly, this metric along with the pending
> mesages
> >>> /
> >>>>>> bytes would answer the questions of:
> >>>>>
> >>>>>> - Does the connector consume fast enough? Lagging behind + empty
> >>> buffer
> >>>>> =
> >>>>>> cannot consume fast enough.
> >>>>>> - Does the connector emit fast enough? Lagging behind + full buffer
> =
> >>>>>> cannot emit fast enough, i.e. the Flink pipeline is slow.
> >>>>>
> >>>>> Yes, exactly. This can also be used to support decisions like
> changing
> >>> the
> >>>>> parallelism of the sources and/or down stream operators.
> >>>>>
> >>>>> I’m not sure if I understand your proposal with time based
> >>> measurements.
> >>>>> Maybe I’m missing something, but I do not see how measuring time
> alone
> >>>>> could answer the problem: where is the bottleneck. Time spent on the
> >>>>> next/emit might be short or long (depending on how heavy to process
> the
> >>>>> record is) and the source can still be bottlenecked/back pressured or
> >>> not.
> >>>>> Usually the easiest and the most reliable way how to detect
> >>> bottlenecks is
> >>>>> by checking usage of input & output buffers, since when input buffer
> is
> >>>>> full while output buffer is empty, that’s the definition of a
> >>> bottleneck.
> >>>>> Also this is usually very easy and cheap to measure (it works
> >>> effectively
> >>>>> the same way as current’s Flink back pressure monitoring, but more
> >>> cleanly,
> >>>>> without probing thread’s stack traces).
> >>>>>
> >>>>> Also keep in mind that we are already using the buffer usage metrics
> >>> for
> >>>>> detecting the bottlenecks in Flink’s internal network exchanges
> (manual
> >>>>> work). That’s the reason why I wanted to extend this to
> sources/sinks,
> >>>>> since they are currently our blind spot.
> >>>>>
> >>>>>> One feature we are currently working on to scale Flink automatically
> >>>>> relies
> >>>>>> on some metrics answering the same question
> >>>>>
> >>>>> That would be very helpful feature. I think in order to achieve that
> we
> >>>>> would need to:
> >>>>> 1. Define the metrics that would allow us to manually detect
> >>> bottlenecks.
> >>>>> As I wrote, we already have them in most of the places, except of
> >>>>> sources/sinks.
> >>>>> 2. Use those metrics, to automatically detect bottlenecks. Currently
> we
> >>>>> are only automatically detecting back pressure and reporting it to
> the
> >>> user
> >>>>> in web UI (is it exposed as a metric at all?). Detecting the root
> >>> cause of
> >>>>> the back pressure (bottleneck) is one step further.
> >>>>> 3. Use the knowledge about where exactly the bottleneck is located,
> to
> >>> try
> >>>>> to do something with it.
> >>>>>
> >>>>> I think you are aiming for point 3., but before we reach it, we are
> >>> still
> >>>>> missing 1. & 2. Also even if we have 3., there is a value in 1 & 2
> for
> >>>>> manual analysis/dashboards.
> >>>>>
> >>>>> However, having the knowledge of where the bottleneck is, doesn’t
> >>>>> necessarily mean that we know what we can do about it. For example
> >>>>> increasing parallelism might or might not help with anything (data
> >>> skew,
> >>>>> bottleneck on some resource that does not scale), but this remark
> >>> applies
> >>>>> always, regardless of the way how did we detect the bottleneck.
> >>>>>
> >>>>> Piotrek
> >>>>>
> >>>>>> On 3 Jun 2019, at 06:16, Becket Qin <be...@gmail.com> wrote:
> >>>>>>
> >>>>>> Hi Piotr,
> >>>>>>
> >>>>>> Thanks for the suggestion. Some thoughts below:
> >>>>>>
> >>>>>> Re 1: The pending messages / bytes.
> >>>>>> I completely agree these are very useful metrics and we should
> expect
> >>> the
> >>>>>> connector to report. WRT the way to expose them, it seems more
> >>> consistent
> >>>>>> to add two metrics instead of adding a method (unless there are
> other
> >>> use
> >>>>>> cases other than metric reporting). So we can add the following two
> >>>>> metrics.
> >>>>>> - pending.bytes, Gauge
> >>>>>> - pending.messages, Gauge
> >>>>>> Applicable connectors can choose to report them. These two metrics
> >>> along
> >>>>>> with latency should be sufficient for users to understand the
> progress
> >>>>> of a
> >>>>>> connector.
> >>>>>>
> >>>>>>
> >>>>>> Re 2: Number of buffered data in-memory of the connector
> >>>>>> If I understand correctly, this metric along with the pending
> mesages
> >>> /
> >>>>>> bytes would answer the questions of:
> >>>>>> - Does the connector consume fast enough? Lagging behind + empty
> >>> buffer
> >>>>> =
> >>>>>> cannot consume fast enough.
> >>>>>> - Does the connector emit fast enough? Lagging behind + full buffer
> =
> >>>>>> cannot emit fast enough, i.e. the Flink pipeline is slow.
> >>>>>>
> >>>>>> One feature we are currently working on to scale Flink automatically
> >>>>> relies
> >>>>>> on some metrics answering the same question, more specifically, we
> are
> >>>>>> profiling the time spent on .next() method (time to consume) and the
> >>> time
> >>>>>> spent on .collect() method (time to emit / process). One advantage
> of
> >>>>> such
> >>>>>> method level time cost allows us to calculate the parallelism
> >>> required to
> >>>>>> keep up in case their is a lag.
> >>>>>>
> >>>>>> However, one concern I have regarding such metric is that they are
> >>>>>> implementation specific. Either profiling on the method time, or
> >>>>> reporting
> >>>>>> buffer usage assumes the connector are implemented in such a way. A
> >>>>>> slightly better solution might be have the following metric:
> >>>>>>
> >>>>>> - EmitTimeRatio (or FetchTimeRatio): The time spent on emitting
> >>>>>> records / Total time elapsed.
> >>>>>>
> >>>>>> This assumes that the source connectors have to emit the records to
> >>> the
> >>>>>> downstream at some point. The emission may take some time ( e.g. go
> >>>>> through
> >>>>>> chained operators). And the rest of the time are spent to prepare
> the
> >>>>>> record to emit, including time for consuming and format conversion,
> >>> etc.
> >>>>>> Ideally, we'd like to see the time spent on record fetch and emit to
> >>> be
> >>>>>> about the same, so no one is bottleneck for the other.
> >>>>>>
> >>>>>> The downside of these time based metrics is additional overhead to
> get
> >>>>> the
> >>>>>> time, therefore sampling might be needed. But in practice I feel
> such
> >>>>> time
> >>>>>> based metric might be more useful if we want to take action.
> >>>>>>
> >>>>>>
> >>>>>> I think we should absolutely add metrics in (1) to the metric
> >>> convention.
> >>>>>> We could also add the metrics mentioned in (2) if we reach consensus
> >>> on
> >>>>>> that. What do you think?
> >>>>>>
> >>>>>> Thanks,
> >>>>>>
> >>>>>> Jiangjie (Becket) Qin
> >>>>>>
> >>>>>>
> >>>>>> On Fri, May 31, 2019 at 4:26 PM Piotr Nowojski <piotr@ververica.com
> >
> >>>>> wrote:
> >>>>>>
> >>>>>>> Hey Becket,
> >>>>>>>
> >>>>>>> Re 1a) and 1b) +1 from my side.
> >>>>>>>
> >>>>>>> I’ve discussed this issue:
> >>>>>>>
> >>>>>>>>>>
> >>>>>>>>>> 2. It would be nice to have metrics, that allow us to check the
> >>> cause
> >>>>>>> of
> >>>>>>>>>> back pressure:
> >>>>>>>>>> a) for sources, length of input queue (in bytes? Or boolean
> >>>>>>>>>> hasSomethingl/isEmpty)
> >>>>>>>>>> b) for sinks, length of output queue (in bytes? Or boolean
> >>>>>>>>>> hasSomething/isEmpty)
> >>>>>>>
> >>>>>>> With Nico at some lengths and he also saw the benefits of them. We
> >>> also
> >>>>>>> have more concrete proposal for that.
> >>>>>>>
> >>>>>>> Actually there are two really useful metrics, that we are missing
> >>>>>>> currently:
> >>>>>>>
> >>>>>>> 1. Number of data/records/bytes in the backlog to process. For
> >>> example
> >>>>>>> remaining number of bytes in unread files. Or pending data in Kafka
> >>>>> topics.
> >>>>>>> 2. Number of buffered data in-memory of the connector, that are
> >>> waiting
> >>>>> to
> >>>>>>> be processed pushed to Flink pipeline.
> >>>>>>>
> >>>>>>> Re 1:
> >>>>>>> This would have to be a metric provided directly by a connector. It
> >>>>> could
> >>>>>>> be an undefined `int`:
> >>>>>>>
> >>>>>>> `int backlog` - estimate of pending work.
> >>>>>>>
> >>>>>>> “Undefined” meaning that it would be up to a connector to decided
> >>>>> whether
> >>>>>>> it’s measured in bytes, records, pending files or whatever it is
> >>>>> possible
> >>>>>>> to provide by the connector. This is because I assume not every
> >>>>> connector
> >>>>>>> can provide exact number and for some of them it might be
> impossible
> >>> to
> >>>>>>> provide records number of bytes count.
> >>>>>>>
> >>>>>>> Re 2:
> >>>>>>> This metric could be either provided by a connector, or calculated
> >>>>> crudely
> >>>>>>> by Flink:
> >>>>>>>
> >>>>>>> `float bufferUsage` - value from [0.0, 1.0] range
> >>>>>>>
> >>>>>>> Percentage of used in memory buffers, like in Kafka’s handover.
> >>>>>>>
> >>>>>>> It could be crudely implemented by Flink with FLIP-27
> >>>>>>> SourceReader#isAvailable. If SourceReader is not available reported
> >>>>>>> `bufferUsage` could be 0.0. If it is available, it could be 1.0. I
> >>> think
> >>>>>>> this would be a good enough estimation for most of the use cases
> >>> (that
> >>>>>>> could be overloaded and implemented better if desired). Especially
> >>>>> since we
> >>>>>>> are reporting only probed values: if probed values are almost
> always
> >>>>> “1.0”,
> >>>>>>> it would mean that we have a back pressure. If they are almost
> always
> >>>>>>> “0.0”, there is probably no back pressure at the sources.
> >>>>>>>
> >>>>>>> What do you think about this?
> >>>>>>>
> >>>>>>> Piotrek
> >>>>>>>
> >>>>>>>> On 30 May 2019, at 11:41, Becket Qin <be...@gmail.com>
> wrote:
> >>>>>>>>
> >>>>>>>> Hi all,
> >>>>>>>>
> >>>>>>>> Thanks a lot for all the feedback and comments. I'd like to
> continue
> >>>>> the
> >>>>>>>> discussion on this FLIP.
> >>>>>>>>
> >>>>>>>> I updated the FLIP-33 wiki to remove all the histogram metrics
> from
> >>> the
> >>>>>>>> first version of metric convention due to the performance concern.
> >>> The
> >>>>>>> plan
> >>>>>>>> is to introduce them later when we have a mechanism to opt in/out
> >>>>>>> metrics.
> >>>>>>>> At that point, users can decide whether they want to pay the cost
> to
> >>>>> get
> >>>>>>>> the metric or not.
> >>>>>>>>
> >>>>>>>> As Stephan suggested, for this FLIP, let's first try to agree on
> the
> >>>>>>> small
> >>>>>>>> list of conventional metrics that connectors should follow.
> >>>>>>>> Just to be clear, the purpose of the convention is not to enforce
> >>> every
> >>>>>>>> connector to report all these metrics, but to provide a guidance
> in
> >>>>> case
> >>>>>>>> these metrics are reported by some connectors.
> >>>>>>>>
> >>>>>>>>
> >>>>>>>> @ Stephan & Chesnay,
> >>>>>>>>
> >>>>>>>> Regarding the duplication of `RecordsIn` metric in operator / task
> >>>>>>>> IOMetricGroups, from what I understand, for source operator, it is
> >>>>>>> actually
> >>>>>>>> the SourceFunction that reports the operator level
> >>>>>>>> RecordsIn/RecordsInPerSecond metric. So they are essentially the
> >>> same
> >>>>>>>> metric in the operator level IOMetricGroup. Similarly for the Sink
> >>>>>>>> operator, the operator level RecordsOut/RecordsOutPerSecond
> metrics
> >>> are
> >>>>>>>> also reported by the Sink function. I marked them as existing in
> the
> >>>>>>>> FLIP-33 wiki page. Please let me know if I misunderstood.
> >>>>>>>>
> >>>>>>>> Thanks,
> >>>>>>>>
> >>>>>>>> Jiangjie (Becket) Qin
> >>>>>>>>
> >>>>>>>>
> >>>>>>>> On Thu, May 30, 2019 at 5:16 PM Becket Qin <be...@gmail.com>
> >>>>> wrote:
> >>>>>>>>
> >>>>>>>>> Hi Piotr,
> >>>>>>>>>
> >>>>>>>>> Thanks a lot for the feedback.
> >>>>>>>>>
> >>>>>>>>> 1a) I guess you are referring to the part that "original system
> >>>>> specific
> >>>>>>>>> metrics should also be reported". The performance impact depends
> on
> >>>>> the
> >>>>>>>>> implementation. An efficient implementation would only record the
> >>>>> metric
> >>>>>>>>> once, but report them with two different metric names. This is
> >>>>> unlikely
> >>>>>>> to
> >>>>>>>>> hurt performance.
> >>>>>>>>>
> >>>>>>>>> 1b) Yes, I agree that we should avoid adding overhead to the
> >>> critical
> >>>>>>> path
> >>>>>>>>> by all means. This is sometimes a tradeoff, running blindly
> without
> >>>>> any
> >>>>>>>>> metric gives best performance, but sometimes might be frustrating
> >>> when
> >>>>>>> we
> >>>>>>>>> debug some issues.
> >>>>>>>>>
> >>>>>>>>> 2. The metrics are indeed very useful. Are they supposed to be
> >>>>> reported
> >>>>>>> by
> >>>>>>>>> the connectors or Flink itself? At this point FLIP-33 is more
> >>> focused
> >>>>> on
> >>>>>>>>> provide a guidance to the connector authors on the metrics
> >>> reporting.
> >>>>>>> That
> >>>>>>>>> said, after FLIP-27, I think we should absolutely report these
> >>> metrics
> >>>>>>> in
> >>>>>>>>> the abstract implementation. In any case, the metric convention
> in
> >>>>> this
> >>>>>>>>> list are expected to evolve over time.
> >>>>>>>>>
> >>>>>>>>> Thanks,
> >>>>>>>>>
> >>>>>>>>> Jiangjie (Becket) Qin
> >>>>>>>>>
> >>>>>>>>> On Tue, May 28, 2019 at 6:24 PM Piotr Nowojski <
> >>> piotr@ververica.com>
> >>>>>>>>> wrote:
> >>>>>>>>>
> >>>>>>>>>> Hi,
> >>>>>>>>>>
> >>>>>>>>>> Thanks for the proposal and driving the effort here Becket :)
> I’ve
> >>>>> read
> >>>>>>>>>> through the FLIP-33 [1], and here are couple of my thoughts.
> >>>>>>>>>>
> >>>>>>>>>> Big +1 for standardising the metric names between connectors, it
> >>> will
> >>>>>>>>>> definitely help us and users a lot.
> >>>>>>>>>>
> >>>>>>>>>> Issues/questions/things to discuss that I’ve thought of:
> >>>>>>>>>>
> >>>>>>>>>> 1a. If we are about to duplicate some metrics, can this become a
> >>>>>>>>>> performance issue?
> >>>>>>>>>> 1b. Generally speaking, we should make sure that collecting
> those
> >>>>>>> metrics
> >>>>>>>>>> is as non intrusive as possible, especially that they will need
> >>> to be
> >>>>>>>>>> updated once per record. (They might be collected more rarely
> with
> >>>>> some
> >>>>>>>>>> overhead, but the hot path of updating it per record will need
> to
> >>> be
> >>>>> as
> >>>>>>>>>> quick as possible). That includes both avoiding heavy
> computation
> >>> on
> >>>>>>> per
> >>>>>>>>>> record path: histograms?, measuring time for time based metrics
> >>> (per
> >>>>>>>>>> second) (System.currentTimeMillis() depending on the
> >>> implementation
> >>>>> can
> >>>>>>>>>> invoke a system call)
> >>>>>>>>>>
> >>>>>>>>>> 2. It would be nice to have metrics, that allow us to check the
> >>> cause
> >>>>>>> of
> >>>>>>>>>> back pressure:
> >>>>>>>>>> a) for sources, length of input queue (in bytes? Or boolean
> >>>>>>>>>> hasSomethingl/isEmpty)
> >>>>>>>>>> b) for sinks, length of output queue (in bytes? Or boolean
> >>>>>>>>>> hasSomething/isEmpty)
> >>>>>>>>>>
> >>>>>>>>>> a) is useful in a scenario when we are processing backlog of
> >>> records,
> >>>>>>> all
> >>>>>>>>>> of the internal Flink’s input/output network buffers are empty,
> >>> and
> >>>>> we
> >>>>>>> want
> >>>>>>>>>> to check whether the external source system is the bottleneck
> >>>>> (source’s
> >>>>>>>>>> input queue will be empty), or if the Flink’s connector is the
> >>>>>>> bottleneck
> >>>>>>>>>> (source’s input queues will be full).
> >>>>>>>>>> b) similar story. Backlog of records, but this time all of the
> >>>>> internal
> >>>>>>>>>> Flink’s input/ouput network buffers are full, and we want o
> check
> >>>>>>> whether
> >>>>>>>>>> the external sink system is the bottleneck (sink output queues
> are
> >>>>>>> full),
> >>>>>>>>>> or if the Flink’s connector is the bottleneck (sink’s output
> >>> queues
> >>>>>>> will be
> >>>>>>>>>> empty)
> >>>>>>>>>>
> >>>>>>>>>> It might be sometimes difficult to provide those metrics, so
> they
> >>>>> could
> >>>>>>>>>> be optional, but if we could provide them, it would be really
> >>>>> helpful.
> >>>>>>>>>>
> >>>>>>>>>> Piotrek
> >>>>>>>>>>
> >>>>>>>>>> [1]
> >>>>>>>>>>
> >>>>>>>
> >>>>>
> >>>
> https://cwiki.apache.org/confluence/display/FLINK/FLIP-33:+Standardize+Connector+Metrics
> >>>>>>>>>> <
> >>>>>>>>>>
> >>>>>>>
> >>>>>
> >>>
> https://cwiki.apache.org/confluence/display/FLINK/FLIP-33:+Standardize+Connector+Metrics
> >>>>>>>>>>>
> >>>>>>>>>>
> >>>>>>>>>>> On 24 Apr 2019, at 13:28, Stephan Ewen <se...@apache.org>
> wrote:
> >>>>>>>>>>>
> >>>>>>>>>>> I think this sounds reasonable.
> >>>>>>>>>>>
> >>>>>>>>>>> Let's keep the "reconfiguration without stopping the job" out
> of
> >>>>> this,
> >>>>>>>>>>> because that would be a super big effort and if we approach
> that,
> >>>>> then
> >>>>>>>>>> in
> >>>>>>>>>>> more generic way rather than specific to connector metrics.
> >>>>>>>>>>>
> >>>>>>>>>>> I would suggest to look at the following things before starting
> >>> with
> >>>>>>> any
> >>>>>>>>>>> implementation work:
> >>>>>>>>>>>
> >>>>>>>>>>> - Try and find a committer to support this, otherwise it will
> be
> >>>>> hard
> >>>>>>>>>> to
> >>>>>>>>>>> make progress
> >>>>>>>>>>> - Start with defining a smaller set of "core metrics" and
> extend
> >>> the
> >>>>>>>>>> set
> >>>>>>>>>>> later. I think that is easier than now blocking on reaching
> >>>>> consensus
> >>>>>>>>>> on a
> >>>>>>>>>>> large group of metrics.
> >>>>>>>>>>> - Find a solution to the problem Chesnay mentioned, that the
> >>>>> "records
> >>>>>>>>>> in"
> >>>>>>>>>>> metric is somehow overloaded and exists already in the IO
> Metric
> >>>>>>> group.
> >>>>>>>>>>>
> >>>>>>>>>>>
> >>>>>>>>>>> On Mon, Mar 25, 2019 at 7:16 AM Becket Qin <
> becket.qin@gmail.com
> >>>>
> >>>>>>>>>> wrote:
> >>>>>>>>>>>
> >>>>>>>>>>>> Hi Stephan,
> >>>>>>>>>>>>
> >>>>>>>>>>>> Thanks a lot for the feedback. All makes sense.
> >>>>>>>>>>>>
> >>>>>>>>>>>> It is a good suggestion to simply have an onRecord(numBytes,
> >>>>>>> eventTime)
> >>>>>>>>>>>> method for connector writers. It should meet most of the
> >>>>>>> requirements,
> >>>>>>>>>>>> individual
> >>>>>>>>>>>>
> >>>>>>>>>>>> The configurable metrics feature is something really useful,
> >>>>>>>>>> especially if
> >>>>>>>>>>>> we can somehow make it dynamically configurable without
> stopping
> >>>>> the
> >>>>>>>>>> jobs.
> >>>>>>>>>>>> It might be better to make it a separate discussion because it
> >>> is a
> >>>>>>>>>> more
> >>>>>>>>>>>> generic feature instead of only for connectors.
> >>>>>>>>>>>>
> >>>>>>>>>>>> So in order to make some progress, in this FLIP we can limit
> the
> >>>>>>>>>> discussion
> >>>>>>>>>>>> scope to the connector related items:
> >>>>>>>>>>>>
> >>>>>>>>>>>> - the standard connector metric names and types.
> >>>>>>>>>>>> - the abstract ConnectorMetricHandler interface
> >>>>>>>>>>>>
> >>>>>>>>>>>> I'll start a separate thread to discuss other general metric
> >>>>> related
> >>>>>>>>>>>> enhancement items including:
> >>>>>>>>>>>>
> >>>>>>>>>>>> - optional metrics
> >>>>>>>>>>>> - dynamic metric configuration
> >>>>>>>>>>>> - potential combination with rate limiter
> >>>>>>>>>>>>
> >>>>>>>>>>>> Does this plan sound reasonable?
> >>>>>>>>>>>>
> >>>>>>>>>>>> Thanks,
> >>>>>>>>>>>>
> >>>>>>>>>>>> Jiangjie (Becket) Qin
> >>>>>>>>>>>>
> >>>>>>>>>>>> On Sat, Mar 23, 2019 at 5:53 AM Stephan Ewen <
> sewen@apache.org>
> >>>>>>> wrote:
> >>>>>>>>>>>>
> >>>>>>>>>>>>> Ignoring for a moment implementation details, this connector
> >>>>> metrics
> >>>>>>>>>> work
> >>>>>>>>>>>>> is a really good thing to do, in my opinion
> >>>>>>>>>>>>>
> >>>>>>>>>>>>> The questions "oh, my job seems to be doing nothing, I am
> >>> looking
> >>>>> at
> >>>>>>>>>> the
> >>>>>>>>>>>> UI
> >>>>>>>>>>>>> and the 'records in' value is still zero" is in the top three
> >>>>>>> support
> >>>>>>>>>>>>> questions I have been asked personally.
> >>>>>>>>>>>>> Introspection into "how far is the consumer lagging behind"
> >>> (event
> >>>>>>>>>> time
> >>>>>>>>>>>>> fetch latency) came up many times as well.
> >>>>>>>>>>>>>
> >>>>>>>>>>>>> So big +1 to solving this problem.
> >>>>>>>>>>>>>
> >>>>>>>>>>>>> About the exact design - I would try to go for the following
> >>>>>>>>>> properties:
> >>>>>>>>>>>>>
> >>>>>>>>>>>>> - keep complexity of of connectors. Ideally the metrics
> handler
> >>>>> has
> >>>>>>> a
> >>>>>>>>>>>>> single onRecord(numBytes, eventTime) method or so, and
> >>> everything
> >>>>>>>>>> else is
> >>>>>>>>>>>>> internal to the handler. That makes it dead simple for the
> >>>>>>> connector.
> >>>>>>>>>> We
> >>>>>>>>>>>>> can also think of an extensive scheme for connector specific
> >>>>>>> metrics.
> >>>>>>>>>>>>>
> >>>>>>>>>>>>> - make it configurable on the job it cluster level which
> >>> metrics
> >>>>> the
> >>>>>>>>>>>>> handler internally creates when that method is invoked.
> >>>>>>>>>>>>>
> >>>>>>>>>>>>> What do you think?
> >>>>>>>>>>>>>
> >>>>>>>>>>>>> Best,
> >>>>>>>>>>>>> Stephan
> >>>>>>>>>>>>>
> >>>>>>>>>>>>>
> >>>>>>>>>>>>> On Thu, Mar 21, 2019 at 10:42 AM Chesnay Schepler <
> >>>>>>> chesnay@apache.org
> >>>>>>>>>>>
> >>>>>>>>>>>>> wrote:
> >>>>>>>>>>>>>
> >>>>>>>>>>>>>> As I said before, I believe this to be over-engineered and
> >>> have
> >>>>> no
> >>>>>>>>>>>>>> interest in this implementation.
> >>>>>>>>>>>>>>
> >>>>>>>>>>>>>> There are conceptual issues like defining a duplicate
> >>>>>>>>>>>> numBytesIn(PerSec)
> >>>>>>>>>>>>>> metric that already exists for each operator.
> >>>>>>>>>>>>>>
> >>>>>>>>>>>>>> On 21.03.2019 06:13, Becket Qin wrote:
> >>>>>>>>>>>>>>> A few updates to the thread. I uploaded a patch[1] as a
> >>> complete
> >>>>>>>>>>>>>>> example of how users can use the metrics in the future.
> >>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>> Some thoughts below after taking a look at the
> >>>>> AbstractMetricGroup
> >>>>>>>>>>>> and
> >>>>>>>>>>>>>>> its subclasses.
> >>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>> This patch intends to provide convenience for Flink
> connector
> >>>>>>>>>>>>>>> implementations to follow metrics standards proposed in
> >>> FLIP-33.
> >>>>>>> It
> >>>>>>>>>>>>>>> also try to enhance the metric management in general way to
> >>> help
> >>>>>>>>>>>> users
> >>>>>>>>>>>>>>> with:
> >>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>> 1. metric definition
> >>>>>>>>>>>>>>> 2. metric dependencies check
> >>>>>>>>>>>>>>> 3. metric validation
> >>>>>>>>>>>>>>> 4. metric control (turn on / off particular metrics)
> >>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>> This patch wraps |MetricGroup| to extend the functionality
> of
> >>>>>>>>>>>>>>> |AbstractMetricGroup| and its subclasses. The
> >>>>>>>>>>>>>>> |AbstractMetricGroup| mainly focus on the metric group
> >>>>> hierarchy,
> >>>>>>>>>> but
> >>>>>>>>>>>>>>> does not really manage the metrics other than keeping them
> >>> in a
> >>>>>>> Map.
> >>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>> Ideally we should only have one entry point for the
> metrics.
> >>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>> Right now the entry point is |AbstractMetricGroup|.
> However,
> >>>>>>> besides
> >>>>>>>>>>>>>>> the missing functionality mentioned above,
> >>> |AbstractMetricGroup|
> >>>>>>>>>>>> seems
> >>>>>>>>>>>>>>> deeply rooted in Flink runtime. We could extract it out to
> >>>>>>>>>>>>>>> flink-metrics in order to use it for generic purpose. There
> >>> will
> >>>>>>> be
> >>>>>>>>>>>>>>> some work, though.
> >>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>> Another approach is to make |AbstractMetrics| in this patch
> >>> as
> >>>>> the
> >>>>>>>>>>>>>>> metric entry point. It wraps metric group and provides the
> >>>>> missing
> >>>>>>>>>>>>>>> functionalities. Then we can roll out this pattern to
> runtime
> >>>>>>>>>>>>>>> components gradually as well.
> >>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>> My first thought is that the latter approach gives a more
> >>> smooth
> >>>>>>>>>>>>>>> migration. But I am also OK with doing a refactoring on the
> >>>>>>>>>>>>>>> |AbstractMetricGroup| family.
> >>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>> Thanks,
> >>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>> Jiangjie (Becket) Qin
> >>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>> [1] https://github.com/becketqin/flink/pull/1
> >>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>> On Mon, Feb 25, 2019 at 2:32 PM Becket Qin <
> >>>>> becket.qin@gmail.com
> >>>>>>>>>>>>>>> <ma...@gmail.com>> wrote:
> >>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>> Hi Chesnay,
> >>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>> It might be easier to discuss some implementation details
> in
> >>>>> the
> >>>>>>>>>>>>>>> PR review instead of in the FLIP discussion thread. I have
> a
> >>>>>>>>>>>> patch
> >>>>>>>>>>>>>>> for Kafka connectors ready but haven't submitted the PR
> yet.
> >>>>>>>>>>>>>>> Hopefully that will help explain a bit more.
> >>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>> ** Re: metric type binding
> >>>>>>>>>>>>>>> This is a valid point that worths discussing. If I
> understand
> >>>>>>>>>>>>>>> correctly, there are two points:
> >>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>> 1. Metric type / interface does not matter as long as the
> >>>>> metric
> >>>>>>>>>>>>>>> semantic is clearly defined.
> >>>>>>>>>>>>>>> Conceptually speaking, I agree that as long as the metric
> >>>>>>>>>>>> semantic
> >>>>>>>>>>>>>>> is defined, metric type does not matter. To some extent,
> >>> Gauge
> >>>>> /
> >>>>>>>>>>>>>>> Counter / Meter / Histogram themselves can be think of as
> >>> some
> >>>>>>>>>>>>>>> well-recognized semantics, if you wish. In Flink, these
> >>> metric
> >>>>>>>>>>>>>>> semantics have their associated interface classes. In
> >>> practice,
> >>>>>>>>>>>>>>> such semantic to interface binding seems necessary for
> >>>>> different
> >>>>>>>>>>>>>>> components to communicate. Simply standardize the semantic
> >>> of
> >>>>>>>>>>>> the
> >>>>>>>>>>>>>>> connector metrics seems not sufficient for people to build
> >>>>>>>>>>>>>>> ecosystem on top of. At the end of the day, we still need
> to
> >>>>>>> have
> >>>>>>>>>>>>>>> some embodiment of the metric semantics that people can
> >>> program
> >>>>>>>>>>>>>>> against.
> >>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>> 2. Sometimes the same metric semantic can be exposed using
> >>>>>>>>>>>>>>> different metric types / interfaces.
> >>>>>>>>>>>>>>> This is a good point. Counter and Gauge-as-a-Counter are
> >>> pretty
> >>>>>>>>>>>>>>> much interchangeable. This is more of a trade-off between
> the
> >>>>>>>>>>>> user
> >>>>>>>>>>>>>>> experience of metric producers and consumers. The metric
> >>>>>>>>>>>> producers
> >>>>>>>>>>>>>>> want to use Counter or Gauge depending on whether the
> counter
> >>>>> is
> >>>>>>>>>>>>>>> already tracked in code, while ideally the metric consumers
> >>>>> only
> >>>>>>>>>>>>>>> want to see a single metric type for each metric. I am
> >>> leaning
> >>>>>>>>>>>>>>> towards to make the metric producers happy, i.e. allow
> Gauge
> >>> /
> >>>>>>>>>>>>>>> Counter metric type, and the the metric consumers handle
> the
> >>>>>>> type
> >>>>>>>>>>>>>>> variation. The reason is that in practice, there might be
> >>> more
> >>>>>>>>>>>>>>> connector implementations than metric reporter
> >>> implementations.
> >>>>>>>>>>>> We
> >>>>>>>>>>>>>>> could also provide some helper method to facilitate reading
> >>>>> from
> >>>>>>>>>>>>>>> such variable metric type.
> >>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>> Just some quick replies to the comments around
> implementation
> >>>>>>>>>>>>>> details.
> >>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>> 4) single place where metrics are registered except
> >>>>>>>>>>>>>>> connector-specific
> >>>>>>>>>>>>>>> ones (which we can't really avoid).
> >>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>> Register connector specific ones in a single place is
> >>> actually
> >>>>>>>>>>>>>>> something that I want to achieve.
> >>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>> 2) I'm talking about time-series databases like
> >>> Prometheus.
> >>>>>>>>>>>> We
> >>>>>>>>>>>>>>> would
> >>>>>>>>>>>>>>> only have a gauge metric exposing the last
> >>>>>>> fetchTime/emitTime
> >>>>>>>>>>>>>>> that is
> >>>>>>>>>>>>>>> regularly reported to the backend (Prometheus), where a
> >>>>> user
> >>>>>>>>>>>>>>> could build
> >>>>>>>>>>>>>>> a histogram of his choosing when/if he wants it.
> >>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>> Not sure if such downsampling works. As an example, if a
> user
> >>>>>>>>>>>>>>> complains that there are some intermittent latency spikes
> >>>>> (maybe
> >>>>>>>>>>>> a
> >>>>>>>>>>>>>>> few records in 10 seconds) in their processing system.
> >>> Having a
> >>>>>>>>>>>>>>> Gauge sampling instantaneous latency seems unlikely useful.
> >>>>>>>>>>>>>>> However by looking at actual 99.9 percentile latency might
> >>>>> help.
> >>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>> Thanks,
> >>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>> Jiangjie (Becket) Qin
> >>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>> On Fri, Feb 22, 2019 at 9:30 PM Chesnay Schepler
> >>>>>>>>>>>>>>> <chesnay@apache.org <ma...@apache.org>> wrote:
> >>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>> Re: over complication of implementation.
> >>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>> I think I get understand better know what you're
> shooting
> >>>>>>>>>>>> for,
> >>>>>>>>>>>>>>> effectively something like the OperatorIOMetricGroup.
> >>>>>>>>>>>>>>> But still, re-define setupConnectorMetrics() to accept a
> >>>>> set
> >>>>>>>>>>>>>>> of flags
> >>>>>>>>>>>>>>> for counters/meters(ans _possibly_ histograms) along
> >>> with a
> >>>>>>>>>>>>>>> set of
> >>>>>>>>>>>>>>> well-defined Optional<Gauge<?>>, and return the group.
> >>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>> Solves all issues as far as i can tell:
> >>>>>>>>>>>>>>> 1) no metrics must be created manually (except Gauges,
> >>>>> which
> >>>>>>>>>>>>> are
> >>>>>>>>>>>>>>> effectively just Suppliers and you can't get around
> >>> this),
> >>>>>>>>>>>>>>> 2) additional metrics can be registered on the returned
> >>>>>>>>>>>> group,
> >>>>>>>>>>>>>>> 3) see 1),
> >>>>>>>>>>>>>>> 4) single place where metrics are registered except
> >>>>>>>>>>>>>>> connector-specific
> >>>>>>>>>>>>>>> ones (which we can't really avoid).
> >>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>> Re: Histogram
> >>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>> 1) As an example, whether "numRecordsIn" is exposed as a
> >>>>>>>>>>>>>>> Counter or a
> >>>>>>>>>>>>>>> Gauge should be irrelevant. So far we're using the
> metric
> >>>>>>>>>>>> type
> >>>>>>>>>>>>>>> that is
> >>>>>>>>>>>>>>> the most convenient at exposing a given value. If there
> >>> is
> >>>>>>>>>>>>>>> some backing
> >>>>>>>>>>>>>>> data-structure that we want to expose some data from we
> >>>>>>>>>>>>>>> typically opt
> >>>>>>>>>>>>>>> for a Gauge, as otherwise we're just mucking around with
> >>>>> the
> >>>>>>>>>>>>>>> Meter/Counter API to get it to match. Similarly, if we
> >>> want
> >>>>>>>>>>>> to
> >>>>>>>>>>>>>>> count
> >>>>>>>>>>>>>>> something but no current count exists we typically added
> >>> a
> >>>>>>>>>>>>>>> Counter.
> >>>>>>>>>>>>>>> That's why attaching semantics to metric types makes
> >>> little
> >>>>>>>>>>>>>>> sense (but
> >>>>>>>>>>>>>>> unfortunately several reporters already do it); for
> >>>>>>>>>>>>>>> counters/meters
> >>>>>>>>>>>>>>> certainly, but the majority of metrics are gauges.
> >>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>> 2) I'm talking about time-series databases like
> >>> Prometheus.
> >>>>>>>>>>>> We
> >>>>>>>>>>>>>>> would
> >>>>>>>>>>>>>>> only have a gauge metric exposing the last
> >>>>>>> fetchTime/emitTime
> >>>>>>>>>>>>>>> that is
> >>>>>>>>>>>>>>> regularly reported to the backend (Prometheus), where a
> >>>>> user
> >>>>>>>>>>>>>>> could build
> >>>>>>>>>>>>>>> a histogram of his choosing when/if he wants it.
> >>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>> On 22.02.2019 13:57, Becket Qin wrote:
> >>>>>>>>>>>>>>>> Hi Chesnay,
> >>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>> Thanks for the explanation.
> >>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>> ** Re: FLIP
> >>>>>>>>>>>>>>>> I might have misunderstood this, but it seems that "major
> >>>>>>>>>>>>>>> changes" are well
> >>>>>>>>>>>>>>>> defined in FLIP. The full contents is following:
> >>>>>>>>>>>>>>>> What is considered a "major change" that needs a FLIP?
> >>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>> Any of the following should be considered a major change:
> >>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>> - Any major new feature, subsystem, or piece of
> >>>>>>>>>>>>>>> functionality
> >>>>>>>>>>>>>>>> - *Any change that impacts the public interfaces of the
> >>>>>>>>>>>>>>> project*
> >>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>> What are the "public interfaces" of the project?
> >>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>> *All of the following are public interfaces *that people
> >>>>>>>>>>>>>>> build around:
> >>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>> - DataStream and DataSet API, including classes related
> >>>>>>>>>>>>>>> to that, such as
> >>>>>>>>>>>>>>>> StreamExecutionEnvironment
> >>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>> - Classes marked with the @Public annotation
> >>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>> - On-disk binary formats, such as
> >>>>>>>>>>>> checkpoints/savepoints
> >>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>> - User-facing scripts/command-line tools, i.e.
> >>>>>>>>>>>>>>> bin/flink, Yarn scripts,
> >>>>>>>>>>>>>>>> Mesos scripts
> >>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>> - Configuration settings
> >>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>> - *Exposed monitoring information*
> >>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>> So any monitoring information change is considered as
> >>>>>>>>>>>> public
> >>>>>>>>>>>>>>> interface, and
> >>>>>>>>>>>>>>>> any public interface change is considered as a "major
> >>>>>>>>>>>>> change".
> >>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>> ** Re: over complication of implementation.
> >>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>> Although this is more of implementation details that is
> not
> >>>>>>>>>>>>>>> covered by the
> >>>>>>>>>>>>>>>> FLIP. But it may be worth discussing.
> >>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>> First of all, I completely agree that we should use the
> >>>>>>>>>>>>>>> simplest way to
> >>>>>>>>>>>>>>>> achieve our goal. To me the goal is the following:
> >>>>>>>>>>>>>>>> 1. Clear connector conventions and interfaces.
> >>>>>>>>>>>>>>>> 2. The easiness of creating a connector.
> >>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>> Both of them are important to the prosperity of the
> >>>>>>>>>>>>>>> connector ecosystem. So
> >>>>>>>>>>>>>>>> I'd rather abstract as much as possible on our side to
> make
> >>>>>>>>>>>>>>> the connector
> >>>>>>>>>>>>>>>> developer's work lighter. Given this goal, a static util
> >>>>>>>>>>>>>>> method approach
> >>>>>>>>>>>>>>>> might have a few drawbacks:
> >>>>>>>>>>>>>>>> 1. Users still have to construct the metrics by
> themselves.
> >>>>>>>>>>>>>>> (And note that
> >>>>>>>>>>>>>>>> this might be erroneous by itself. For example, a customer
> >>>>>>>>>>>>>>> wrapper around
> >>>>>>>>>>>>>>>> dropwizard meter maybe used instead of MeterView).
> >>>>>>>>>>>>>>>> 2. When connector specific metrics are added, it is
> >>>>>>>>>>>>>>> difficult to enforce
> >>>>>>>>>>>>>>>> the scope to be the same as standard metrics.
> >>>>>>>>>>>>>>>> 3. It seems that a method proliferation is inevitable if
> we
> >>>>>>>>>>>>>>> want to apply
> >>>>>>>>>>>>>>>> sanity checks. e.g. The metric of numBytesIn was not
> >>>>>>>>>>>>>>> registered for a meter.
> >>>>>>>>>>>>>>>> 4. Metrics are still defined in random places and hard to
> >>>>>>>>>>>>>> track.
> >>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>> The current PR I had was inspired by the Config system in
> >>>>>>>>>>>>>>> Kafka, which I
> >>>>>>>>>>>>>>>> found pretty handy. In fact it is not only used by Kafka
> >>>>>>>>>>>>>>> itself but even
> >>>>>>>>>>>>>>>> some other projects that depend on Kafka. I am not saying
> >>>>>>>>>>>>>>> this approach is
> >>>>>>>>>>>>>>>> perfect. But I think it worths to save the work for
> >>>>>>>>>>>>>>> connector writers and
> >>>>>>>>>>>>>>>> encourage more systematic implementation. That being said,
> >>>>>>>>>>>> I
> >>>>>>>>>>>>>>> am fully open
> >>>>>>>>>>>>>>>> to suggestions.
> >>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>> Re: Histogram
> >>>>>>>>>>>>>>>> I think there are two orthogonal questions around those
> >>>>>>>>>>>>>> metrics:
> >>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>> 1. Regardless of the metric type, by just looking at the
> >>>>>>>>>>>>>>> meaning of a
> >>>>>>>>>>>>>>>> metric, is generic to all connectors? If the answer is
> yes,
> >>>>>>>>>>>>>>> we should
> >>>>>>>>>>>>>>>> include the metric into the convention. No matter whether
> >>>>>>>>>>>> we
> >>>>>>>>>>>>>>> include it
> >>>>>>>>>>>>>>>> into the convention or not, some connector implementations
> >>>>>>>>>>>>>>> will emit such
> >>>>>>>>>>>>>>>> metric. It is better to have a convention than letting
> each
> >>>>>>>>>>>>>>> connector do
> >>>>>>>>>>>>>>>> random things.
> >>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>> 2. If a standard metric is a histogram, what should we do?
> >>>>>>>>>>>>>>>> I agree that we should make it clear that using histograms
> >>>>>>>>>>>>>>> will have
> >>>>>>>>>>>>>>>> performance risk. But I do see histogram is useful in some
> >>>>>>>>>>>>>>> fine-granularity
> >>>>>>>>>>>>>>>> debugging where one do not have the luxury to stop the
> >>>>>>>>>>>>>>> system and inject
> >>>>>>>>>>>>>>>> more inspection code. So the workaround I am thinking is
> to
> >>>>>>>>>>>>>>> provide some
> >>>>>>>>>>>>>>>> implementation suggestions. Assume later on we have a
> >>>>>>>>>>>>>>> mechanism of
> >>>>>>>>>>>>>>>> selective metrics. In the abstract metrics class we can
> >>>>>>>>>>>>>>> disable those
> >>>>>>>>>>>>>>>> metrics by default individual connector writers does not
> >>>>>>>>>>>>>>> have to do
> >>>>>>>>>>>>>>>> anything (this is another advantage of having an
> >>>>>>>>>>>>>>> AbstractMetrics instead of
> >>>>>>>>>>>>>>>> static util methods.)
> >>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>> I am not sure I fully understand the histogram in the
> >>>>>>>>>>>>>>> backend approach. Can
> >>>>>>>>>>>>>>>> you explain a bit more? Do you mean emitting the raw data,
> >>>>>>>>>>>>>>> e.g. fetchTime
> >>>>>>>>>>>>>>>> and emitTime with each record and let the histogram
> >>>>>>>>>>>>>>> computation happen in
> >>>>>>>>>>>>>>>> the background? Or let the processing thread putting the
> >>>>>>>>>>>>>>> values into a
> >>>>>>>>>>>>>>>> queue and have a separate thread polling from the queue
> and
> >>>>>>>>>>>>>>> add them into
> >>>>>>>>>>>>>>>> the histogram?
> >>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>> Thanks,
> >>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>> Jiangjie (Becket) Qin
> >>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>> On Fri, Feb 22, 2019 at 4:34 PM Chesnay Schepler
> >>>>>>>>>>>>>>> <chesnay@apache.org <ma...@apache.org>> wrote:
> >>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>> Re: Flip
> >>>>>>>>>>>>>>>>> The very first line under both the main header and
> Purpose
> >>>>>>>>>>>>>>> section
> >>>>>>>>>>>>>>>>> describe Flips as "major changes", which this isn't.
> >>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>> Re: complication
> >>>>>>>>>>>>>>>>> I'm not arguing against standardization, but again an
> >>>>>>>>>>>>>>> over-complicated
> >>>>>>>>>>>>>>>>> implementation when a static utility method would be
> >>>>>>>>>>>>>>> sufficient.
> >>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>> public static void setupConnectorMetrics(
> >>>>>>>>>>>>>>>>> MetricGroup operatorMetricGroup,
> >>>>>>>>>>>>>>>>> String connectorName,
> >>>>>>>>>>>>>>>>> Optional<Gauge<Long>> numRecordsIn,
> >>>>>>>>>>>>>>>>> ...)
> >>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>> This gives you all you need:
> >>>>>>>>>>>>>>>>> * a well-defined set of metrics for a connector to opt-in
> >>>>>>>>>>>>>>>>> * standardized naming schemes for scope and individual
> >>>>>>>>>>>>> metrics
> >>>>>>>>>>>>>>>>> * standardize metric types (although personally I'm not
> >>>>>>>>>>>>>>> interested in that
> >>>>>>>>>>>>>>>>> since metric types should be considered syntactic sugar)
> >>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>> Re: Configurable Histogram
> >>>>>>>>>>>>>>>>> If anything they _must_ be turned off by default, but the
> >>>>>>>>>>>>>>> metric system is
> >>>>>>>>>>>>>>>>> already exposing so many options that I'm not too keen on
> >>>>>>>>>>>>>>> adding even more.
> >>>>>>>>>>>>>>>>> You have also only addressed my first argument against
> >>>>>>>>>>>>>>> histograms
> >>>>>>>>>>>>>>>>> (performance), the second one still stands (calculate
> >>>>>>>>>>>>>>> histogram in metric
> >>>>>>>>>>>>>>>>> backends instead).
> >>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>> On 21.02.2019 16:27, Becket Qin wrote:
> >>>>>>>>>>>>>>>>>> Hi Chesnay,
> >>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>> Thanks for the comments. I think this is worthy of a
> FLIP
> >>>>>>>>>>>>>>> because it is
> >>>>>>>>>>>>>>>>>> public API. According to the FLIP description a FlIP is
> >>>>>>>>>>>>>>> required in case
> >>>>>>>>>>>>>>>>> of:
> >>>>>>>>>>>>>>>>>> - Any change that impacts the public interfaces of
> >>>>>>>>>>>>>>> the project
> >>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>> and the following entry is found in the definition of
> >>>>>>>>>>>>>>> "public interface".
> >>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>> - Exposed monitoring information
> >>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>> Metrics are critical to any production system. So a
> clear
> >>>>>>>>>>>>>>> metric
> >>>>>>>>>>>>>>>>> definition
> >>>>>>>>>>>>>>>>>> is important for any serious users. For an organization
> >>>>>>>>>>>>>>> with large Flink
> >>>>>>>>>>>>>>>>>> installation, change in metrics means great amount of
> >>>>>>>>>>>>>>> work. So such
> >>>>>>>>>>>>>>>>> changes
> >>>>>>>>>>>>>>>>>> do need to be fully discussed and documented.
> >>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>> ** Re: Histogram.
> >>>>>>>>>>>>>>>>>> We can discuss whether there is a better way to expose
> >>>>>>>>>>>>>>> metrics that are
> >>>>>>>>>>>>>>>>>> suitable for histograms. My micro-benchmark on various
> >>>>>>>>>>>>>>> histogram
> >>>>>>>>>>>>>>>>>> implementations also indicates that they are
> >>>>>>>>>>>> significantly
> >>>>>>>>>>>>>>> slower than
> >>>>>>>>>>>>>>>>>> other metric types. But I don't think that means never
> >>>>>>>>>>>> use
> >>>>>>>>>>>>>>> histogram, but
> >>>>>>>>>>>>>>>>>> means use it with caution. For example, we can suggest
> >>>>>>>>>>>> the
> >>>>>>>>>>>>>>>>> implementations
> >>>>>>>>>>>>>>>>>> to turn them off by default and only turn it on for a
> >>>>>>>>>>>>>>> small amount of
> >>>>>>>>>>>>>>>>> time
> >>>>>>>>>>>>>>>>>> when performing some micro-debugging.
> >>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>> ** Re: complication:
> >>>>>>>>>>>>>>>>>> Connector conventions are essential for Flink ecosystem.
> >>>>>>>>>>>>>>> Flink connectors
> >>>>>>>>>>>>>>>>>> pool is probably the most important part of Flink, just
> >>>>>>>>>>>>>>> like any other
> >>>>>>>>>>>>>>>>> data
> >>>>>>>>>>>>>>>>>> system. Clear conventions of connectors will help build
> >>>>>>>>>>>>>>> Flink ecosystem
> >>>>>>>>>>>>>>>>> in
> >>>>>>>>>>>>>>>>>> a more organic way.
> >>>>>>>>>>>>>>>>>> Take the metrics convention as an example, imagine
> >>>>>>>>>>>> someone
> >>>>>>>>>>>>>>> has developed
> >>>>>>>>>>>>>>>>> a
> >>>>>>>>>>>>>>>>>> Flink connector for System foo, and another developer
> may
> >>>>>>>>>>>>>>> have developed
> >>>>>>>>>>>>>>>>> a
> >>>>>>>>>>>>>>>>>> monitoring and diagnostic framework for Flink which
> >>>>>>>>>>>>>>> analyzes the Flink
> >>>>>>>>>>>>>>>>> job
> >>>>>>>>>>>>>>>>>> performance based on metrics. With a clear metric
> >>>>>>>>>>>>>>> convention, those two
> >>>>>>>>>>>>>>>>>> projects could be developed independently. Once users
> put
> >>>>>>>>>>>>>>> them together,
> >>>>>>>>>>>>>>>>>> it would work without additional modifications. This
> >>>>>>>>>>>>>>> cannot be easily
> >>>>>>>>>>>>>>>>>> achieved by just defining a few constants.
> >>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>> ** Re: selective metrics:
> >>>>>>>>>>>>>>>>>> Sure, we can discuss that in a separate thread.
> >>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>> @Dawid
> >>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>> ** Re: latency / fetchedLatency
> >>>>>>>>>>>>>>>>>> The primary purpose of establish such a convention is to
> >>>>>>>>>>>>>>> help developers
> >>>>>>>>>>>>>>>>>> write connectors in a more compatible way. The
> convention
> >>>>>>>>>>>>>>> is supposed to
> >>>>>>>>>>>>>>>>> be
> >>>>>>>>>>>>>>>>>> defined more proactively. So when look at the
> convention,
> >>>>>>>>>>>>>>> it seems more
> >>>>>>>>>>>>>>>>>> important to see if the concept is applicable to
> >>>>>>>>>>>>>>> connectors in general.
> >>>>>>>>>>>>>>>>> It
> >>>>>>>>>>>>>>>>>> might be true so far only Kafka connector reports
> >>>>>>>>>>>> latency.
> >>>>>>>>>>>>>>> But there
> >>>>>>>>>>>>>>>>> might
> >>>>>>>>>>>>>>>>>> be hundreds of other connector implementations in the
> >>>>>>>>>>>>>>> Flink ecosystem,
> >>>>>>>>>>>>>>>>>> though not in the Flink repo, and some of them also
> emits
> >>>>>>>>>>>>>>> latency. I
> >>>>>>>>>>>>>>>>> think
> >>>>>>>>>>>>>>>>>> a lot of other sources actually also has an append
> >>>>>>>>>>>>>>> timestamp. e.g.
> >>>>>>>>>>>>>>>>> database
> >>>>>>>>>>>>>>>>>> bin logs and some K-V stores. So I wouldn't be surprised
> >>>>>>>>>>>>>>> if some database
> >>>>>>>>>>>>>>>>>> connector can also emit latency metrics.
> >>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>> Thanks,
> >>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>> Jiangjie (Becket) Qin
> >>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>> On Thu, Feb 21, 2019 at 10:14 PM Chesnay Schepler
> >>>>>>>>>>>>>>> <chesnay@apache.org <ma...@apache.org>>
> >>>>>>>>>>>>>>>>>> wrote:
> >>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>> Regarding 2) It doesn't make sense to investigate this
> >>>>>>>>>>>> as
> >>>>>>>>>>>>>>> part of this
> >>>>>>>>>>>>>>>>>>> FLIP. This is something that could be of interest for
> >>>>>>>>>>>> the
> >>>>>>>>>>>>>>> entire metric
> >>>>>>>>>>>>>>>>>>> system, and should be designed for as such.
> >>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>> Regarding the proposal as a whole:
> >>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>> Histogram metrics shall not be added to the core of
> >>>>>>>>>>>>>>> Flink. They are
> >>>>>>>>>>>>>>>>>>> significantly more expensive than other metrics, and
> >>>>>>>>>>>>>>> calculating
> >>>>>>>>>>>>>>>>>>> histograms in the application is regarded as an
> >>>>>>>>>>>>>>> anti-pattern by several
> >>>>>>>>>>>>>>>>>>> metric backends, who instead recommend to expose the
> raw
> >>>>>>>>>>>>>>> data and
> >>>>>>>>>>>>>>>>>>> calculate the histogram in the backend.
> >>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>> Second, this seems overly complicated. Given that we
> >>>>>>>>>>>>>>> already established
> >>>>>>>>>>>>>>>>>>> that not all connectors will export all metrics we are
> >>>>>>>>>>>>>>> effectively
> >>>>>>>>>>>>>>>>>>> reducing this down to a consistent naming scheme. We
> >>>>>>>>>>>>>>> don't need anything
> >>>>>>>>>>>>>>>>>>> sophisticated for that; basically just a few constants
> >>>>>>>>>>>>>>> that all
> >>>>>>>>>>>>>>>>>>> connectors use.
> >>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>> I'm not convinced that this is worthy of a FLIP.
> >>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>> On 21.02.2019 14:26, Dawid Wysakowicz wrote:
> >>>>>>>>>>>>>>>>>>>> Hi,
> >>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>> Ad 1. In general I undestand and I agree. But those
> >>>>>>>>>>>>>>> particular metrics
> >>>>>>>>>>>>>>>>>>>> (latency, fetchLatency), right now would only be
> >>>>>>>>>>>>>>> reported if user uses
> >>>>>>>>>>>>>>>>>>>> KafkaConsumer with internal timestampAssigner with
> >>>>>>>>>>>>>>> StreamCharacteristic
> >>>>>>>>>>>>>>>>>>>> set to EventTime, right? That sounds like a very
> >>>>>>>>>>>>>>> specific case. I am
> >>>>>>>>>>>>>>>>> not
> >>>>>>>>>>>>>>>>>>>> sure if we should introduce a generic metric that will
> >>>>>>>>>>>> be
> >>>>>>>>>>>>>>>>>>>> disabled/absent for most of implementations.
> >>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>> Ad.2 That sounds like an orthogonal issue, that might
> >>>>>>>>>>>>>>> make sense to
> >>>>>>>>>>>>>>>>>>>> investigate in the future.
> >>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>> Best,
> >>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>> Dawid
> >>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>> On 21/02/2019 13:20, Becket Qin wrote:
> >>>>>>>>>>>>>>>>>>>>> Hi Dawid,
> >>>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>>> Thanks for the feedback. That makes sense to me.
> There
> >>>>>>>>>>>>>>> are two cases
> >>>>>>>>>>>>>>>>> to
> >>>>>>>>>>>>>>>>>>> be
> >>>>>>>>>>>>>>>>>>>>> addressed.
> >>>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>>> 1. The metrics are supposed to be a guidance. It is
> >>>>>>>>>>>>>>> likely that a
> >>>>>>>>>>>>>>>>>>> connector
> >>>>>>>>>>>>>>>>>>>>> only supports some but not all of the metrics. In
> that
> >>>>>>>>>>>>>>> case, each
> >>>>>>>>>>>>>>>>>>> connector
> >>>>>>>>>>>>>>>>>>>>> implementation should have the freedom to decide
> which
> >>>>>>>>>>>>>>> metrics are
> >>>>>>>>>>>>>>>>>>>>> reported. For the metrics that are supported, the
> >>>>>>>>>>>>>>> guidance should be
> >>>>>>>>>>>>>>>>>>>>> followed.
> >>>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>>> 2. Sometimes users may want to disable certain
> metrics
> >>>>>>>>>>>>>>> for some reason
> >>>>>>>>>>>>>>>>>>>>> (e.g. performance / reprocessing of data). A generic
> >>>>>>>>>>>>>>> mechanism should
> >>>>>>>>>>>>>>>>> be
> >>>>>>>>>>>>>>>>>>>>> provided to allow user choose which metrics are
> >>>>>>>>>>>>>>> reported. This
> >>>>>>>>>>>>>>>>> mechanism
> >>>>>>>>>>>>>>>>>>>>> should also be honored by the connector
> >>>>>>>>>>>> implementations.
> >>>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>>> Does this sound reasonable to you?
> >>>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>>> Thanks,
> >>>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>>> Jiangjie (Becket) Qin
> >>>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>>> On Thu, Feb 21, 2019 at 4:22 PM Dawid Wysakowicz <
> >>>>>>>>>>>>>>>>>>> dwysakowicz@apache.org <mailto:dwysakowicz@apache.org
> >>
> >>>>>>>>>>>>>>>>>>>>> wrote:
> >>>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>>>> Hi,
> >>>>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>>>> Generally I like the idea of having a unified,
> >>>>>>>>>>>>>>> standard set of
> >>>>>>>>>>>>>>>>> metrics
> >>>>>>>>>>>>>>>>>>> for
> >>>>>>>>>>>>>>>>>>>>>> all connectors. I have some slight concerns about
> >>>>>>>>>>>>>>> fetchLatency and
> >>>>>>>>>>>>>>>>>>>>>> latency though. They are computed based on EventTime
> >>>>>>>>>>>>>>> which is not a
> >>>>>>>>>>>>>>>>>>> purely
> >>>>>>>>>>>>>>>>>>>>>> technical feature. It depends often on some business
> >>>>>>>>>>>>>>> logic, might be
> >>>>>>>>>>>>>>>>>>> absent
> >>>>>>>>>>>>>>>>>>>>>> or defined after source. Those metrics could also
> >>>>>>>>>>>>>>> behave in a weird
> >>>>>>>>>>>>>>>>>>> way in
> >>>>>>>>>>>>>>>>>>>>>> case of replaying backlog. Therefore I am not sure
> if
> >>>>>>>>>>>>>>> we should
> >>>>>>>>>>>>>>>>> include
> >>>>>>>>>>>>>>>>>>>>>> those metrics by default. Maybe we could at least
> >>>>>>>>>>>>>>> introduce a feature
> >>>>>>>>>>>>>>>>>>>>>> switch for them? What do you think?
> >>>>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>>>> Best,
> >>>>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>>>> Dawid
> >>>>>>>>>>>>>>>>>>>>>> On 21/02/2019 03:13, Becket Qin wrote:
> >>>>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>>>> Bump. If there is no objections to the proposed
> >>>>>>>>>>>>>>> metrics. I'll start a
> >>>>>>>>>>>>>>>>>>>>>> voting thread later toady.
> >>>>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>>>> Thanks,
> >>>>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>>>> Jiangjie (Becket) Qin
> >>>>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>>>> On Mon, Feb 11, 2019 at 8:17 PM Becket Qin
> >>>>>>>>>>>>>>> <becket.qin@gmail.com <ma...@gmail.com>> <
> >>>>>>>>>>>>>>>>>>> becket.qin@gmail.com <ma...@gmail.com>>
> >>>>>>>>>>>>> wrote:
> >>>>>>>>>>>>>>>>>>>>>> Hi folks,
> >>>>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>>>> I would like to start the FLIP discussion thread
> >>>>>>>>>>>> about
> >>>>>>>>>>>>>>> standardize
> >>>>>>>>>>>>>>>>> the
> >>>>>>>>>>>>>>>>>>>>>> connector metrics.
> >>>>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>>>> In short, we would like to provide a convention of
> >>>>>>>>>>>>>>> Flink connector
> >>>>>>>>>>>>>>>>>>>>>> metrics. It will help simplify the monitoring and
> >>>>>>>>>>>>>>> alerting on Flink
> >>>>>>>>>>>>>>>>>>> jobs.
> >>>>>>>>>>>>>>>>>>>>>> The FLIP link is following:
> >>>>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>
> >>>>>>>>>>>>>
> >>>>>>>>>>>>
> >>>>>>>>>>
> >>>>>>>
> >>>>>
> >>>
> https://cwiki.apache.org/confluence/display/FLINK/FLIP-33%3A+Standardize+Connector+Metrics
> >>>>>>>>>>>>>>>>>>>>>> Thanks,
> >>>>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>>>> Jiangjie (Becket) Qin
> >>>>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>
> >>>>>>>>>>>>>>
> >>>>>>>>>>>>>
> >>>>>>>>>>>>
> >>>>>>>>>>
> >>>>>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>
> >>>>>
> >>>>>
> >>>
> >>>
>
>
Re: [DISCUSS] FLIP-33: Standardize connector metrics
Posted by Piotr Nowojski <pi...@ververica.com>.
Thanks for driving this. I’ve just noticed one small thing. With new SourceReader interface Flink will be able to provide `idleTime` metric automatically.
Piotrek
> On 13 Jun 2019, at 03:30, Becket Qin <be...@gmail.com> wrote:
>
> Thanks all for the feedback and discussion.
>
> Since there wasn't any concern raised, I've started the voting thread for
> this FLIP, but please feel free to continue the discussion here if you
> think something still needs to be addressed.
>
> Thanks,
>
> Jiangjie (Becket) Qin
>
>
>
> On Mon, Jun 10, 2019 at 9:10 AM Becket Qin <be...@gmail.com> wrote:
>
>> Hi Piotr,
>>
>> Thanks for the comments. Yes, you are right. Users will have to look at
>> other metrics to decide whether the pipeline is healthy or not in the first
>> place before they can use the time-based metric to fix the bottleneck.
>>
>> I agree that once we have FLIP-27 ready, some of the metrics can just be
>> reported by the abstract implementation.
>>
>> I've updated FLIP-33 wiki page to add the pendingBytes and pendingRecords
>> metric. Please let me know if you have any concern over the updated metric
>> convention proposal.
>>
>> @Chesnay Schepler <ch...@apache.org> @Stephan Ewen
>> <st...@ververica.com> will you also have time to take a look at the
>> proposed metric convention? If there is no further concern I'll start a
>> voting thread for this FLIP in two days.
>>
>> Thanks,
>>
>> Jiangjie (Becket) Qin
>>
>>
>>
>> On Wed, Jun 5, 2019 at 6:54 PM Piotr Nowojski <pi...@ververica.com> wrote:
>>
>>> Hi Becket,
>>>
>>> Thanks for the answer :)
>>>
>>>> By time-based metric, I meant the portion of time spent on producing the
>>>> record to downstream. For example, a source connector can report that
>>> it's
>>>> spending 80% of time to emit record to downstream processing pipeline.
>>> In
>>>> another case, a sink connector may report that its spending 30% of time
>>>> producing the records to the external system.
>>>>
>>>> This is in some sense equivalent to the buffer usage metric:
>>>
>>>> - 80% of time spent on emitting records to downstream ---> downstream
>>>> node is bottleneck ---> output buffer is probably full.
>>>> - 30% of time spent on emitting records to downstream ---> downstream
>>>> node is not bottleneck ---> output buffer is probably not full.
>>>
>>> If by “time spent on emitting records to downstream” you understand
>>> “waiting on back pressure”, then I see your point. And I agree that some
>>> kind of ratio/time based metric gives you more information. However under
>>> “time spent on emitting records to downstream” might be hidden the
>>> following (extreme) situation:
>>>
>>> 1. Job is barely able to handle influx of records, there is 99%
>>> CPU/resource usage in the cluster, but nobody is
>>> bottlenecked/backpressured, all output buffers are empty, everybody is
>>> waiting in 1% of it’s time for more records to process.
>>> 2. 80% time can still be spent on "down stream operators”, because they
>>> are the CPU intensive operations, but this doesn’t mean that increasing the
>>> parallelism down the stream will help with anything there. To the contrary,
>>> increasing parallelism of the source operator might help to increase
>>> resource utilisation up to 100%.
>>>
>>> However, this “time based/ratio” approach can be extended to in/output
>>> buffer usage. Besides collecting an information that input/output buffer is
>>> full/empty, we can probe profile how often are buffer empty/full. If output
>>> buffer is full 1% of times, there is almost no back pressure. If it’s full
>>> 80% of times, there is some back pressure, if it’s full 99.9% of times,
>>> there is huge back pressure.
>>>
>>> Now for autoscaling you could compare the input & output buffers fill
>>> ratio:
>>>
>>> 1. Both are high, the source of bottleneck is down the stream
>>> 2. Output is low, input is high, this is the bottleneck and the higher
>>> the difference, the bigger source of bottleneck is this is operator/task
>>> 3. Output is high, input is low - there was some load spike that we are
>>> currently finishing to process
>>>
>>>
>>>
>>> But long story short, we are probably diverging from the topic of this
>>> discussion, and we can discuss this at some later point.
>>>
>>> For now, for sources:
>>>
>>> as I wrote before, +1 for:
>>> - pending.bytes, Gauge
>>> - pending.messages, Gauge
>>>
>>> When we will be developing/discussing SourceReader from FLIP-27 we might
>>> then add:
>>>
>>> - in-memory.buffer.usage (0 - 100%)
>>>
>>> Which will be estimated automatically by Flink while user will be able to
>>> override/provide better estimation.
>>>
>>> Piotrek
>>>
>>>> On 5 Jun 2019, at 05:42, Becket Qin <be...@gmail.com> wrote:
>>>>
>>>> Hi Piotr,
>>>>
>>>> Thanks for the explanation. Please see some clarifications below.
>>>>
>>>> By time-based metric, I meant the portion of time spent on producing the
>>>> record to downstream. For example, a source connector can report that
>>> it's
>>>> spending 80% of time to emit record to downstream processing pipeline.
>>> In
>>>> another case, a sink connector may report that its spending 30% of time
>>>> producing the records to the external system.
>>>>
>>>> This is in some sense equivalent to the buffer usage metric:
>>>> - 80% of time spent on emitting records to downstream ---> downstream
>>>> node is bottleneck ---> output buffer is probably full.
>>>> - 30% of time spent on emitting records to downstream ---> downstream
>>>> node is not bottleneck ---> output buffer is probably not full.
>>>>
>>>> However, the time-based metric has a few advantages that the buffer
>>> usage
>>>> metric may not have.
>>>>
>>>> 1. Buffer usage metric may not be applicable to all the connector
>>>> implementations, while reporting time-based metric are always doable.
>>>> Some source connectors may not have any input buffer, or they may use
>>> some
>>>> third party library that does not expose the input buffer at all.
>>>> Similarly, for sink connectors, the implementation may not have any
>>> output
>>>> buffer, or the third party library does not expose such buffer.
>>>>
>>>> 2. Although both type of metrics can detect bottleneck, time-based
>>> metrics
>>>> can be used to generate a more informed action to remove the bottleneck.
>>>> For example, when the downstream is bottleneck, the output buffer usage
>>>> metric is likely to be 100%, and the input buffer usage might be 0%.
>>> That
>>>> means we don't know what is the suitable parallelism to lift the
>>>> bottleneck. The time-based metric, on the other hand, would give useful
>>>> information, e.g. if 80% of time was spent on emitting records, we can
>>>> roughly increase the downstream node parallelism by 4 times.
>>>>
>>>> Admittedly, the time-based metrics are more expensive than buffer
>>> usage. So
>>>> we may have to do some sampling to reduce the cost. But in general,
>>> using
>>>> time-based metrics seems worth adding.
>>>>
>>>> That being said, I don't think buffer usage metric and time-based
>>> metrics
>>>> are mutually exclusive. We can probably have both. It is just that in
>>>> practice, features like auto-scaling might prefer time-based metrics for
>>>> the reason stated above.
>>>>
>>>>> 1. Define the metrics that would allow us to manually detect
>>> bottlenecks.
>>>> As I wrote, we already have them in most of the places, except of
>>>> sources/sinks.
>>>>> 2. Use those metrics, to automatically detect bottlenecks. Currently we
>>>> are only automatically detecting back pressure and reporting it to the
>>> user
>>>> in web UI (is it exposed as a metric at all?). Detecting the root cause
>>> of
>>>> the back pressure (bottleneck) is one step further.
>>>>> 3. Use the knowledge about where exactly the bottleneck is located, to
>>>> try to do something with it.
>>>>
>>>> As explained above, I think time-based metric also addresses item 1 and
>>>> item 2.
>>>>
>>>> Any thoughts？
>>>>
>>>> Thanks,
>>>>
>>>> Jiangjie (Becket) Qin
>>>>
>>>>
>>>>
>>>> On Mon, Jun 3, 2019 at 4:14 PM Piotr Nowojski <pi...@ververica.com>
>>> wrote:
>>>>
>>>>> Hi again :)
>>>>>
>>>>>> - pending.bytes, Gauge
>>>>>> - pending.messages, Gauge
>>>>>
>>>>>
>>>>> +1
>>>>>
>>>>> And true, instead of overloading one of the metric it is better when
>>> user
>>>>> can choose to provide only one of them.
>>>>>
>>>>> Re 2:
>>>>>
>>>>>> If I understand correctly, this metric along with the pending mesages
>>> /
>>>>>> bytes would answer the questions of:
>>>>>
>>>>>> - Does the connector consume fast enough? Lagging behind + empty
>>> buffer
>>>>> =
>>>>>> cannot consume fast enough.
>>>>>> - Does the connector emit fast enough? Lagging behind + full buffer =
>>>>>> cannot emit fast enough, i.e. the Flink pipeline is slow.
>>>>>
>>>>> Yes, exactly. This can also be used to support decisions like changing
>>> the
>>>>> parallelism of the sources and/or down stream operators.
>>>>>
>>>>> I’m not sure if I understand your proposal with time based
>>> measurements.
>>>>> Maybe I’m missing something, but I do not see how measuring time alone
>>>>> could answer the problem: where is the bottleneck. Time spent on the
>>>>> next/emit might be short or long (depending on how heavy to process the
>>>>> record is) and the source can still be bottlenecked/back pressured or
>>> not.
>>>>> Usually the easiest and the most reliable way how to detect
>>> bottlenecks is
>>>>> by checking usage of input & output buffers, since when input buffer is
>>>>> full while output buffer is empty, that’s the definition of a
>>> bottleneck.
>>>>> Also this is usually very easy and cheap to measure (it works
>>> effectively
>>>>> the same way as current’s Flink back pressure monitoring, but more
>>> cleanly,
>>>>> without probing thread’s stack traces).
>>>>>
>>>>> Also keep in mind that we are already using the buffer usage metrics
>>> for
>>>>> detecting the bottlenecks in Flink’s internal network exchanges (manual
>>>>> work). That’s the reason why I wanted to extend this to sources/sinks,
>>>>> since they are currently our blind spot.
>>>>>
>>>>>> One feature we are currently working on to scale Flink automatically
>>>>> relies
>>>>>> on some metrics answering the same question
>>>>>
>>>>> That would be very helpful feature. I think in order to achieve that we
>>>>> would need to:
>>>>> 1. Define the metrics that would allow us to manually detect
>>> bottlenecks.
>>>>> As I wrote, we already have them in most of the places, except of
>>>>> sources/sinks.
>>>>> 2. Use those metrics, to automatically detect bottlenecks. Currently we
>>>>> are only automatically detecting back pressure and reporting it to the
>>> user
>>>>> in web UI (is it exposed as a metric at all?). Detecting the root
>>> cause of
>>>>> the back pressure (bottleneck) is one step further.
>>>>> 3. Use the knowledge about where exactly the bottleneck is located, to
>>> try
>>>>> to do something with it.
>>>>>
>>>>> I think you are aiming for point 3., but before we reach it, we are
>>> still
>>>>> missing 1. & 2. Also even if we have 3., there is a value in 1 & 2 for
>>>>> manual analysis/dashboards.
>>>>>
>>>>> However, having the knowledge of where the bottleneck is, doesn’t
>>>>> necessarily mean that we know what we can do about it. For example
>>>>> increasing parallelism might or might not help with anything (data
>>> skew,
>>>>> bottleneck on some resource that does not scale), but this remark
>>> applies
>>>>> always, regardless of the way how did we detect the bottleneck.
>>>>>
>>>>> Piotrek
>>>>>
>>>>>> On 3 Jun 2019, at 06:16, Becket Qin <be...@gmail.com> wrote:
>>>>>>
>>>>>> Hi Piotr,
>>>>>>
>>>>>> Thanks for the suggestion. Some thoughts below:
>>>>>>
>>>>>> Re 1: The pending messages / bytes.
>>>>>> I completely agree these are very useful metrics and we should expect
>>> the
>>>>>> connector to report. WRT the way to expose them, it seems more
>>> consistent
>>>>>> to add two metrics instead of adding a method (unless there are other
>>> use
>>>>>> cases other than metric reporting). So we can add the following two
>>>>> metrics.
>>>>>> - pending.bytes, Gauge
>>>>>> - pending.messages, Gauge
>>>>>> Applicable connectors can choose to report them. These two metrics
>>> along
>>>>>> with latency should be sufficient for users to understand the progress
>>>>> of a
>>>>>> connector.
>>>>>>
>>>>>>
>>>>>> Re 2: Number of buffered data in-memory of the connector
>>>>>> If I understand correctly, this metric along with the pending mesages
>>> /
>>>>>> bytes would answer the questions of:
>>>>>> - Does the connector consume fast enough? Lagging behind + empty
>>> buffer
>>>>> =
>>>>>> cannot consume fast enough.
>>>>>> - Does the connector emit fast enough? Lagging behind + full buffer =
>>>>>> cannot emit fast enough, i.e. the Flink pipeline is slow.
>>>>>>
>>>>>> One feature we are currently working on to scale Flink automatically
>>>>> relies
>>>>>> on some metrics answering the same question, more specifically, we are
>>>>>> profiling the time spent on .next() method (time to consume) and the
>>> time
>>>>>> spent on .collect() method (time to emit / process). One advantage of
>>>>> such
>>>>>> method level time cost allows us to calculate the parallelism
>>> required to
>>>>>> keep up in case their is a lag.
>>>>>>
>>>>>> However, one concern I have regarding such metric is that they are
>>>>>> implementation specific. Either profiling on the method time, or
>>>>> reporting
>>>>>> buffer usage assumes the connector are implemented in such a way. A
>>>>>> slightly better solution might be have the following metric:
>>>>>>
>>>>>> - EmitTimeRatio (or FetchTimeRatio): The time spent on emitting
>>>>>> records / Total time elapsed.
>>>>>>
>>>>>> This assumes that the source connectors have to emit the records to
>>> the
>>>>>> downstream at some point. The emission may take some time ( e.g. go
>>>>> through
>>>>>> chained operators). And the rest of the time are spent to prepare the
>>>>>> record to emit, including time for consuming and format conversion,
>>> etc.
>>>>>> Ideally, we'd like to see the time spent on record fetch and emit to
>>> be
>>>>>> about the same, so no one is bottleneck for the other.
>>>>>>
>>>>>> The downside of these time based metrics is additional overhead to get
>>>>> the
>>>>>> time, therefore sampling might be needed. But in practice I feel such
>>>>> time
>>>>>> based metric might be more useful if we want to take action.
>>>>>>
>>>>>>
>>>>>> I think we should absolutely add metrics in (1) to the metric
>>> convention.
>>>>>> We could also add the metrics mentioned in (2) if we reach consensus
>>> on
>>>>>> that. What do you think?
>>>>>>
>>>>>> Thanks,
>>>>>>
>>>>>> Jiangjie (Becket) Qin
>>>>>>
>>>>>>
>>>>>> On Fri, May 31, 2019 at 4:26 PM Piotr Nowojski <pi...@ververica.com>
>>>>> wrote:
>>>>>>
>>>>>>> Hey Becket,
>>>>>>>
>>>>>>> Re 1a) and 1b) +1 from my side.
>>>>>>>
>>>>>>> I’ve discussed this issue:
>>>>>>>
>>>>>>>>>>
>>>>>>>>>> 2. It would be nice to have metrics, that allow us to check the
>>> cause
>>>>>>> of
>>>>>>>>>> back pressure:
>>>>>>>>>> a) for sources, length of input queue (in bytes? Or boolean
>>>>>>>>>> hasSomethingl/isEmpty)
>>>>>>>>>> b) for sinks, length of output queue (in bytes? Or boolean
>>>>>>>>>> hasSomething/isEmpty)
>>>>>>>
>>>>>>> With Nico at some lengths and he also saw the benefits of them. We
>>> also
>>>>>>> have more concrete proposal for that.
>>>>>>>
>>>>>>> Actually there are two really useful metrics, that we are missing
>>>>>>> currently:
>>>>>>>
>>>>>>> 1. Number of data/records/bytes in the backlog to process. For
>>> example
>>>>>>> remaining number of bytes in unread files. Or pending data in Kafka
>>>>> topics.
>>>>>>> 2. Number of buffered data in-memory of the connector, that are
>>> waiting
>>>>> to
>>>>>>> be processed pushed to Flink pipeline.
>>>>>>>
>>>>>>> Re 1:
>>>>>>> This would have to be a metric provided directly by a connector. It
>>>>> could
>>>>>>> be an undefined `int`:
>>>>>>>
>>>>>>> `int backlog` - estimate of pending work.
>>>>>>>
>>>>>>> “Undefined” meaning that it would be up to a connector to decided
>>>>> whether
>>>>>>> it’s measured in bytes, records, pending files or whatever it is
>>>>> possible
>>>>>>> to provide by the connector. This is because I assume not every
>>>>> connector
>>>>>>> can provide exact number and for some of them it might be impossible
>>> to
>>>>>>> provide records number of bytes count.
>>>>>>>
>>>>>>> Re 2:
>>>>>>> This metric could be either provided by a connector, or calculated
>>>>> crudely
>>>>>>> by Flink:
>>>>>>>
>>>>>>> `float bufferUsage` - value from [0.0, 1.0] range
>>>>>>>
>>>>>>> Percentage of used in memory buffers, like in Kafka’s handover.
>>>>>>>
>>>>>>> It could be crudely implemented by Flink with FLIP-27
>>>>>>> SourceReader#isAvailable. If SourceReader is not available reported
>>>>>>> `bufferUsage` could be 0.0. If it is available, it could be 1.0. I
>>> think
>>>>>>> this would be a good enough estimation for most of the use cases
>>> (that
>>>>>>> could be overloaded and implemented better if desired). Especially
>>>>> since we
>>>>>>> are reporting only probed values: if probed values are almost always
>>>>> “1.0”,
>>>>>>> it would mean that we have a back pressure. If they are almost always
>>>>>>> “0.0”, there is probably no back pressure at the sources.
>>>>>>>
>>>>>>> What do you think about this?
>>>>>>>
>>>>>>> Piotrek
>>>>>>>
>>>>>>>> On 30 May 2019, at 11:41, Becket Qin <be...@gmail.com> wrote:
>>>>>>>>
>>>>>>>> Hi all,
>>>>>>>>
>>>>>>>> Thanks a lot for all the feedback and comments. I'd like to continue
>>>>> the
>>>>>>>> discussion on this FLIP.
>>>>>>>>
>>>>>>>> I updated the FLIP-33 wiki to remove all the histogram metrics from
>>> the
>>>>>>>> first version of metric convention due to the performance concern.
>>> The
>>>>>>> plan
>>>>>>>> is to introduce them later when we have a mechanism to opt in/out
>>>>>>> metrics.
>>>>>>>> At that point, users can decide whether they want to pay the cost to
>>>>> get
>>>>>>>> the metric or not.
>>>>>>>>
>>>>>>>> As Stephan suggested, for this FLIP, let's first try to agree on the
>>>>>>> small
>>>>>>>> list of conventional metrics that connectors should follow.
>>>>>>>> Just to be clear, the purpose of the convention is not to enforce
>>> every
>>>>>>>> connector to report all these metrics, but to provide a guidance in
>>>>> case
>>>>>>>> these metrics are reported by some connectors.
>>>>>>>>
>>>>>>>>
>>>>>>>> @ Stephan & Chesnay,
>>>>>>>>
>>>>>>>> Regarding the duplication of `RecordsIn` metric in operator / task
>>>>>>>> IOMetricGroups, from what I understand, for source operator, it is
>>>>>>> actually
>>>>>>>> the SourceFunction that reports the operator level
>>>>>>>> RecordsIn/RecordsInPerSecond metric. So they are essentially the
>>> same
>>>>>>>> metric in the operator level IOMetricGroup. Similarly for the Sink
>>>>>>>> operator, the operator level RecordsOut/RecordsOutPerSecond metrics
>>> are
>>>>>>>> also reported by the Sink function. I marked them as existing in the
>>>>>>>> FLIP-33 wiki page. Please let me know if I misunderstood.
>>>>>>>>
>>>>>>>> Thanks,
>>>>>>>>
>>>>>>>> Jiangjie (Becket) Qin
>>>>>>>>
>>>>>>>>
>>>>>>>> On Thu, May 30, 2019 at 5:16 PM Becket Qin <be...@gmail.com>
>>>>> wrote:
>>>>>>>>
>>>>>>>>> Hi Piotr,
>>>>>>>>>
>>>>>>>>> Thanks a lot for the feedback.
>>>>>>>>>
>>>>>>>>> 1a) I guess you are referring to the part that "original system
>>>>> specific
>>>>>>>>> metrics should also be reported". The performance impact depends on
>>>>> the
>>>>>>>>> implementation. An efficient implementation would only record the
>>>>> metric
>>>>>>>>> once, but report them with two different metric names. This is
>>>>> unlikely
>>>>>>> to
>>>>>>>>> hurt performance.
>>>>>>>>>
>>>>>>>>> 1b) Yes, I agree that we should avoid adding overhead to the
>>> critical
>>>>>>> path
>>>>>>>>> by all means. This is sometimes a tradeoff, running blindly without
>>>>> any
>>>>>>>>> metric gives best performance, but sometimes might be frustrating
>>> when
>>>>>>> we
>>>>>>>>> debug some issues.
>>>>>>>>>
>>>>>>>>> 2. The metrics are indeed very useful. Are they supposed to be
>>>>> reported
>>>>>>> by
>>>>>>>>> the connectors or Flink itself? At this point FLIP-33 is more
>>> focused
>>>>> on
>>>>>>>>> provide a guidance to the connector authors on the metrics
>>> reporting.
>>>>>>> That
>>>>>>>>> said, after FLIP-27, I think we should absolutely report these
>>> metrics
>>>>>>> in
>>>>>>>>> the abstract implementation. In any case, the metric convention in
>>>>> this
>>>>>>>>> list are expected to evolve over time.
>>>>>>>>>
>>>>>>>>> Thanks,
>>>>>>>>>
>>>>>>>>> Jiangjie (Becket) Qin
>>>>>>>>>
>>>>>>>>> On Tue, May 28, 2019 at 6:24 PM Piotr Nowojski <
>>> piotr@ververica.com>
>>>>>>>>> wrote:
>>>>>>>>>
>>>>>>>>>> Hi,
>>>>>>>>>>
>>>>>>>>>> Thanks for the proposal and driving the effort here Becket :) I’ve
>>>>> read
>>>>>>>>>> through the FLIP-33 [1], and here are couple of my thoughts.
>>>>>>>>>>
>>>>>>>>>> Big +1 for standardising the metric names between connectors, it
>>> will
>>>>>>>>>> definitely help us and users a lot.
>>>>>>>>>>
>>>>>>>>>> Issues/questions/things to discuss that I’ve thought of:
>>>>>>>>>>
>>>>>>>>>> 1a. If we are about to duplicate some metrics, can this become a
>>>>>>>>>> performance issue?
>>>>>>>>>> 1b. Generally speaking, we should make sure that collecting those
>>>>>>> metrics
>>>>>>>>>> is as non intrusive as possible, especially that they will need
>>> to be
>>>>>>>>>> updated once per record. (They might be collected more rarely with
>>>>> some
>>>>>>>>>> overhead, but the hot path of updating it per record will need to
>>> be
>>>>> as
>>>>>>>>>> quick as possible). That includes both avoiding heavy computation
>>> on
>>>>>>> per
>>>>>>>>>> record path: histograms?, measuring time for time based metrics
>>> (per
>>>>>>>>>> second) (System.currentTimeMillis() depending on the
>>> implementation
>>>>> can
>>>>>>>>>> invoke a system call)
>>>>>>>>>>
>>>>>>>>>> 2. It would be nice to have metrics, that allow us to check the
>>> cause
>>>>>>> of
>>>>>>>>>> back pressure:
>>>>>>>>>> a) for sources, length of input queue (in bytes? Or boolean
>>>>>>>>>> hasSomethingl/isEmpty)
>>>>>>>>>> b) for sinks, length of output queue (in bytes? Or boolean
>>>>>>>>>> hasSomething/isEmpty)
>>>>>>>>>>
>>>>>>>>>> a) is useful in a scenario when we are processing backlog of
>>> records,
>>>>>>> all
>>>>>>>>>> of the internal Flink’s input/output network buffers are empty,
>>> and
>>>>> we
>>>>>>> want
>>>>>>>>>> to check whether the external source system is the bottleneck
>>>>> (source’s
>>>>>>>>>> input queue will be empty), or if the Flink’s connector is the
>>>>>>> bottleneck
>>>>>>>>>> (source’s input queues will be full).
>>>>>>>>>> b) similar story. Backlog of records, but this time all of the
>>>>> internal
>>>>>>>>>> Flink’s input/ouput network buffers are full, and we want o check
>>>>>>> whether
>>>>>>>>>> the external sink system is the bottleneck (sink output queues are
>>>>>>> full),
>>>>>>>>>> or if the Flink’s connector is the bottleneck (sink’s output
>>> queues
>>>>>>> will be
>>>>>>>>>> empty)
>>>>>>>>>>
>>>>>>>>>> It might be sometimes difficult to provide those metrics, so they
>>>>> could
>>>>>>>>>> be optional, but if we could provide them, it would be really
>>>>> helpful.
>>>>>>>>>>
>>>>>>>>>> Piotrek
>>>>>>>>>>
>>>>>>>>>> [1]
>>>>>>>>>>
>>>>>>>
>>>>>
>>> https://cwiki.apache.org/confluence/display/FLINK/FLIP-33:+Standardize+Connector+Metrics
>>>>>>>>>> <
>>>>>>>>>>
>>>>>>>
>>>>>
>>> https://cwiki.apache.org/confluence/display/FLINK/FLIP-33:+Standardize+Connector+Metrics
>>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>>> On 24 Apr 2019, at 13:28, Stephan Ewen <se...@apache.org> wrote:
>>>>>>>>>>>
>>>>>>>>>>> I think this sounds reasonable.
>>>>>>>>>>>
>>>>>>>>>>> Let's keep the "reconfiguration without stopping the job" out of
>>>>> this,
>>>>>>>>>>> because that would be a super big effort and if we approach that,
>>>>> then
>>>>>>>>>> in
>>>>>>>>>>> more generic way rather than specific to connector metrics.
>>>>>>>>>>>
>>>>>>>>>>> I would suggest to look at the following things before starting
>>> with
>>>>>>> any
>>>>>>>>>>> implementation work:
>>>>>>>>>>>
>>>>>>>>>>> - Try and find a committer to support this, otherwise it will be
>>>>> hard
>>>>>>>>>> to
>>>>>>>>>>> make progress
>>>>>>>>>>> - Start with defining a smaller set of "core metrics" and extend
>>> the
>>>>>>>>>> set
>>>>>>>>>>> later. I think that is easier than now blocking on reaching
>>>>> consensus
>>>>>>>>>> on a
>>>>>>>>>>> large group of metrics.
>>>>>>>>>>> - Find a solution to the problem Chesnay mentioned, that the
>>>>> "records
>>>>>>>>>> in"
>>>>>>>>>>> metric is somehow overloaded and exists already in the IO Metric
>>>>>>> group.
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>> On Mon, Mar 25, 2019 at 7:16 AM Becket Qin <becket.qin@gmail.com
>>>>
>>>>>>>>>> wrote:
>>>>>>>>>>>
>>>>>>>>>>>> Hi Stephan,
>>>>>>>>>>>>
>>>>>>>>>>>> Thanks a lot for the feedback. All makes sense.
>>>>>>>>>>>>
>>>>>>>>>>>> It is a good suggestion to simply have an onRecord(numBytes,
>>>>>>> eventTime)
>>>>>>>>>>>> method for connector writers. It should meet most of the
>>>>>>> requirements,
>>>>>>>>>>>> individual
>>>>>>>>>>>>
>>>>>>>>>>>> The configurable metrics feature is something really useful,
>>>>>>>>>> especially if
>>>>>>>>>>>> we can somehow make it dynamically configurable without stopping
>>>>> the
>>>>>>>>>> jobs.
>>>>>>>>>>>> It might be better to make it a separate discussion because it
>>> is a
>>>>>>>>>> more
>>>>>>>>>>>> generic feature instead of only for connectors.
>>>>>>>>>>>>
>>>>>>>>>>>> So in order to make some progress, in this FLIP we can limit the
>>>>>>>>>> discussion
>>>>>>>>>>>> scope to the connector related items:
>>>>>>>>>>>>
>>>>>>>>>>>> - the standard connector metric names and types.
>>>>>>>>>>>> - the abstract ConnectorMetricHandler interface
>>>>>>>>>>>>
>>>>>>>>>>>> I'll start a separate thread to discuss other general metric
>>>>> related
>>>>>>>>>>>> enhancement items including:
>>>>>>>>>>>>
>>>>>>>>>>>> - optional metrics
>>>>>>>>>>>> - dynamic metric configuration
>>>>>>>>>>>> - potential combination with rate limiter
>>>>>>>>>>>>
>>>>>>>>>>>> Does this plan sound reasonable?
>>>>>>>>>>>>
>>>>>>>>>>>> Thanks,
>>>>>>>>>>>>
>>>>>>>>>>>> Jiangjie (Becket) Qin
>>>>>>>>>>>>
>>>>>>>>>>>> On Sat, Mar 23, 2019 at 5:53 AM Stephan Ewen <se...@apache.org>
>>>>>>> wrote:
>>>>>>>>>>>>
>>>>>>>>>>>>> Ignoring for a moment implementation details, this connector
>>>>> metrics
>>>>>>>>>> work
>>>>>>>>>>>>> is a really good thing to do, in my opinion
>>>>>>>>>>>>>
>>>>>>>>>>>>> The questions "oh, my job seems to be doing nothing, I am
>>> looking
>>>>> at
>>>>>>>>>> the
>>>>>>>>>>>> UI
>>>>>>>>>>>>> and the 'records in' value is still zero" is in the top three
>>>>>>> support
>>>>>>>>>>>>> questions I have been asked personally.
>>>>>>>>>>>>> Introspection into "how far is the consumer lagging behind"
>>> (event
>>>>>>>>>> time
>>>>>>>>>>>>> fetch latency) came up many times as well.
>>>>>>>>>>>>>
>>>>>>>>>>>>> So big +1 to solving this problem.
>>>>>>>>>>>>>
>>>>>>>>>>>>> About the exact design - I would try to go for the following
>>>>>>>>>> properties:
>>>>>>>>>>>>>
>>>>>>>>>>>>> - keep complexity of of connectors. Ideally the metrics handler
>>>>> has
>>>>>>> a
>>>>>>>>>>>>> single onRecord(numBytes, eventTime) method or so, and
>>> everything
>>>>>>>>>> else is
>>>>>>>>>>>>> internal to the handler. That makes it dead simple for the
>>>>>>> connector.
>>>>>>>>>> We
>>>>>>>>>>>>> can also think of an extensive scheme for connector specific
>>>>>>> metrics.
>>>>>>>>>>>>>
>>>>>>>>>>>>> - make it configurable on the job it cluster level which
>>> metrics
>>>>> the
>>>>>>>>>>>>> handler internally creates when that method is invoked.
>>>>>>>>>>>>>
>>>>>>>>>>>>> What do you think?
>>>>>>>>>>>>>
>>>>>>>>>>>>> Best,
>>>>>>>>>>>>> Stephan
>>>>>>>>>>>>>
>>>>>>>>>>>>>
>>>>>>>>>>>>> On Thu, Mar 21, 2019 at 10:42 AM Chesnay Schepler <
>>>>>>> chesnay@apache.org
>>>>>>>>>>>
>>>>>>>>>>>>> wrote:
>>>>>>>>>>>>>
>>>>>>>>>>>>>> As I said before, I believe this to be over-engineered and
>>> have
>>>>> no
>>>>>>>>>>>>>> interest in this implementation.
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> There are conceptual issues like defining a duplicate
>>>>>>>>>>>> numBytesIn(PerSec)
>>>>>>>>>>>>>> metric that already exists for each operator.
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> On 21.03.2019 06:13, Becket Qin wrote:
>>>>>>>>>>>>>>> A few updates to the thread. I uploaded a patch[1] as a
>>> complete
>>>>>>>>>>>>>>> example of how users can use the metrics in the future.
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> Some thoughts below after taking a look at the
>>>>> AbstractMetricGroup
>>>>>>>>>>>> and
>>>>>>>>>>>>>>> its subclasses.
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> This patch intends to provide convenience for Flink connector
>>>>>>>>>>>>>>> implementations to follow metrics standards proposed in
>>> FLIP-33.
>>>>>>> It
>>>>>>>>>>>>>>> also try to enhance the metric management in general way to
>>> help
>>>>>>>>>>>> users
>>>>>>>>>>>>>>> with:
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> 1. metric definition
>>>>>>>>>>>>>>> 2. metric dependencies check
>>>>>>>>>>>>>>> 3. metric validation
>>>>>>>>>>>>>>> 4. metric control (turn on / off particular metrics)
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> This patch wraps |MetricGroup| to extend the functionality of
>>>>>>>>>>>>>>> |AbstractMetricGroup| and its subclasses. The
>>>>>>>>>>>>>>> |AbstractMetricGroup| mainly focus on the metric group
>>>>> hierarchy,
>>>>>>>>>> but
>>>>>>>>>>>>>>> does not really manage the metrics other than keeping them
>>> in a
>>>>>>> Map.
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> Ideally we should only have one entry point for the metrics.
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> Right now the entry point is |AbstractMetricGroup|. However,
>>>>>>> besides
>>>>>>>>>>>>>>> the missing functionality mentioned above,
>>> |AbstractMetricGroup|
>>>>>>>>>>>> seems
>>>>>>>>>>>>>>> deeply rooted in Flink runtime. We could extract it out to
>>>>>>>>>>>>>>> flink-metrics in order to use it for generic purpose. There
>>> will
>>>>>>> be
>>>>>>>>>>>>>>> some work, though.
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> Another approach is to make |AbstractMetrics| in this patch
>>> as
>>>>> the
>>>>>>>>>>>>>>> metric entry point. It wraps metric group and provides the
>>>>> missing
>>>>>>>>>>>>>>> functionalities. Then we can roll out this pattern to runtime
>>>>>>>>>>>>>>> components gradually as well.
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> My first thought is that the latter approach gives a more
>>> smooth
>>>>>>>>>>>>>>> migration. But I am also OK with doing a refactoring on the
>>>>>>>>>>>>>>> |AbstractMetricGroup| family.
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> Thanks,
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> Jiangjie (Becket) Qin
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> [1] https://github.com/becketqin/flink/pull/1
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> On Mon, Feb 25, 2019 at 2:32 PM Becket Qin <
>>>>> becket.qin@gmail.com
>>>>>>>>>>>>>>> <ma...@gmail.com>> wrote:
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> Hi Chesnay,
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> It might be easier to discuss some implementation details in
>>>>> the
>>>>>>>>>>>>>>> PR review instead of in the FLIP discussion thread. I have a
>>>>>>>>>>>> patch
>>>>>>>>>>>>>>> for Kafka connectors ready but haven't submitted the PR yet.
>>>>>>>>>>>>>>> Hopefully that will help explain a bit more.
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> ** Re: metric type binding
>>>>>>>>>>>>>>> This is a valid point that worths discussing. If I understand
>>>>>>>>>>>>>>> correctly, there are two points:
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> 1. Metric type / interface does not matter as long as the
>>>>> metric
>>>>>>>>>>>>>>> semantic is clearly defined.
>>>>>>>>>>>>>>> Conceptually speaking, I agree that as long as the metric
>>>>>>>>>>>> semantic
>>>>>>>>>>>>>>> is defined, metric type does not matter. To some extent,
>>> Gauge
>>>>> /
>>>>>>>>>>>>>>> Counter / Meter / Histogram themselves can be think of as
>>> some
>>>>>>>>>>>>>>> well-recognized semantics, if you wish. In Flink, these
>>> metric
>>>>>>>>>>>>>>> semantics have their associated interface classes. In
>>> practice,
>>>>>>>>>>>>>>> such semantic to interface binding seems necessary for
>>>>> different
>>>>>>>>>>>>>>> components to communicate. Simply standardize the semantic
>>> of
>>>>>>>>>>>> the
>>>>>>>>>>>>>>> connector metrics seems not sufficient for people to build
>>>>>>>>>>>>>>> ecosystem on top of. At the end of the day, we still need to
>>>>>>> have
>>>>>>>>>>>>>>> some embodiment of the metric semantics that people can
>>> program
>>>>>>>>>>>>>>> against.
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> 2. Sometimes the same metric semantic can be exposed using
>>>>>>>>>>>>>>> different metric types / interfaces.
>>>>>>>>>>>>>>> This is a good point. Counter and Gauge-as-a-Counter are
>>> pretty
>>>>>>>>>>>>>>> much interchangeable. This is more of a trade-off between the
>>>>>>>>>>>> user
>>>>>>>>>>>>>>> experience of metric producers and consumers. The metric
>>>>>>>>>>>> producers
>>>>>>>>>>>>>>> want to use Counter or Gauge depending on whether the counter
>>>>> is
>>>>>>>>>>>>>>> already tracked in code, while ideally the metric consumers
>>>>> only
>>>>>>>>>>>>>>> want to see a single metric type for each metric. I am
>>> leaning
>>>>>>>>>>>>>>> towards to make the metric producers happy, i.e. allow Gauge
>>> /
>>>>>>>>>>>>>>> Counter metric type, and the the metric consumers handle the
>>>>>>> type
>>>>>>>>>>>>>>> variation. The reason is that in practice, there might be
>>> more
>>>>>>>>>>>>>>> connector implementations than metric reporter
>>> implementations.
>>>>>>>>>>>> We
>>>>>>>>>>>>>>> could also provide some helper method to facilitate reading
>>>>> from
>>>>>>>>>>>>>>> such variable metric type.
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> Just some quick replies to the comments around implementation
>>>>>>>>>>>>>> details.
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> 4) single place where metrics are registered except
>>>>>>>>>>>>>>> connector-specific
>>>>>>>>>>>>>>> ones (which we can't really avoid).
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> Register connector specific ones in a single place is
>>> actually
>>>>>>>>>>>>>>> something that I want to achieve.
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> 2) I'm talking about time-series databases like
>>> Prometheus.
>>>>>>>>>>>> We
>>>>>>>>>>>>>>> would
>>>>>>>>>>>>>>> only have a gauge metric exposing the last
>>>>>>> fetchTime/emitTime
>>>>>>>>>>>>>>> that is
>>>>>>>>>>>>>>> regularly reported to the backend (Prometheus), where a
>>>>> user
>>>>>>>>>>>>>>> could build
>>>>>>>>>>>>>>> a histogram of his choosing when/if he wants it.
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> Not sure if such downsampling works. As an example, if a user
>>>>>>>>>>>>>>> complains that there are some intermittent latency spikes
>>>>> (maybe
>>>>>>>>>>>> a
>>>>>>>>>>>>>>> few records in 10 seconds) in their processing system.
>>> Having a
>>>>>>>>>>>>>>> Gauge sampling instantaneous latency seems unlikely useful.
>>>>>>>>>>>>>>> However by looking at actual 99.9 percentile latency might
>>>>> help.
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> Thanks,
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> Jiangjie (Becket) Qin
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> On Fri, Feb 22, 2019 at 9:30 PM Chesnay Schepler
>>>>>>>>>>>>>>> <chesnay@apache.org <ma...@apache.org>> wrote:
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> Re: over complication of implementation.
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> I think I get understand better know what you're shooting
>>>>>>>>>>>> for,
>>>>>>>>>>>>>>> effectively something like the OperatorIOMetricGroup.
>>>>>>>>>>>>>>> But still, re-define setupConnectorMetrics() to accept a
>>>>> set
>>>>>>>>>>>>>>> of flags
>>>>>>>>>>>>>>> for counters/meters(ans _possibly_ histograms) along
>>> with a
>>>>>>>>>>>>>>> set of
>>>>>>>>>>>>>>> well-defined Optional<Gauge<?>>, and return the group.
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> Solves all issues as far as i can tell:
>>>>>>>>>>>>>>> 1) no metrics must be created manually (except Gauges,
>>>>> which
>>>>>>>>>>>>> are
>>>>>>>>>>>>>>> effectively just Suppliers and you can't get around
>>> this),
>>>>>>>>>>>>>>> 2) additional metrics can be registered on the returned
>>>>>>>>>>>> group,
>>>>>>>>>>>>>>> 3) see 1),
>>>>>>>>>>>>>>> 4) single place where metrics are registered except
>>>>>>>>>>>>>>> connector-specific
>>>>>>>>>>>>>>> ones (which we can't really avoid).
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> Re: Histogram
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> 1) As an example, whether "numRecordsIn" is exposed as a
>>>>>>>>>>>>>>> Counter or a
>>>>>>>>>>>>>>> Gauge should be irrelevant. So far we're using the metric
>>>>>>>>>>>> type
>>>>>>>>>>>>>>> that is
>>>>>>>>>>>>>>> the most convenient at exposing a given value. If there
>>> is
>>>>>>>>>>>>>>> some backing
>>>>>>>>>>>>>>> data-structure that we want to expose some data from we
>>>>>>>>>>>>>>> typically opt
>>>>>>>>>>>>>>> for a Gauge, as otherwise we're just mucking around with
>>>>> the
>>>>>>>>>>>>>>> Meter/Counter API to get it to match. Similarly, if we
>>> want
>>>>>>>>>>>> to
>>>>>>>>>>>>>>> count
>>>>>>>>>>>>>>> something but no current count exists we typically added
>>> a
>>>>>>>>>>>>>>> Counter.
>>>>>>>>>>>>>>> That's why attaching semantics to metric types makes
>>> little
>>>>>>>>>>>>>>> sense (but
>>>>>>>>>>>>>>> unfortunately several reporters already do it); for
>>>>>>>>>>>>>>> counters/meters
>>>>>>>>>>>>>>> certainly, but the majority of metrics are gauges.
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> 2) I'm talking about time-series databases like
>>> Prometheus.
>>>>>>>>>>>> We
>>>>>>>>>>>>>>> would
>>>>>>>>>>>>>>> only have a gauge metric exposing the last
>>>>>>> fetchTime/emitTime
>>>>>>>>>>>>>>> that is
>>>>>>>>>>>>>>> regularly reported to the backend (Prometheus), where a
>>>>> user
>>>>>>>>>>>>>>> could build
>>>>>>>>>>>>>>> a histogram of his choosing when/if he wants it.
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> On 22.02.2019 13:57, Becket Qin wrote:
>>>>>>>>>>>>>>>> Hi Chesnay,
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>> Thanks for the explanation.
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>> ** Re: FLIP
>>>>>>>>>>>>>>>> I might have misunderstood this, but it seems that "major
>>>>>>>>>>>>>>> changes" are well
>>>>>>>>>>>>>>>> defined in FLIP. The full contents is following:
>>>>>>>>>>>>>>>> What is considered a "major change" that needs a FLIP?
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>> Any of the following should be considered a major change:
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>> - Any major new feature, subsystem, or piece of
>>>>>>>>>>>>>>> functionality
>>>>>>>>>>>>>>>> - *Any change that impacts the public interfaces of the
>>>>>>>>>>>>>>> project*
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>> What are the "public interfaces" of the project?
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>> *All of the following are public interfaces *that people
>>>>>>>>>>>>>>> build around:
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>> - DataStream and DataSet API, including classes related
>>>>>>>>>>>>>>> to that, such as
>>>>>>>>>>>>>>>> StreamExecutionEnvironment
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>> - Classes marked with the @Public annotation
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>> - On-disk binary formats, such as
>>>>>>>>>>>> checkpoints/savepoints
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>> - User-facing scripts/command-line tools, i.e.
>>>>>>>>>>>>>>> bin/flink, Yarn scripts,
>>>>>>>>>>>>>>>> Mesos scripts
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>> - Configuration settings
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>> - *Exposed monitoring information*
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>> So any monitoring information change is considered as
>>>>>>>>>>>> public
>>>>>>>>>>>>>>> interface, and
>>>>>>>>>>>>>>>> any public interface change is considered as a "major
>>>>>>>>>>>>> change".
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>> ** Re: over complication of implementation.
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>> Although this is more of implementation details that is not
>>>>>>>>>>>>>>> covered by the
>>>>>>>>>>>>>>>> FLIP. But it may be worth discussing.
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>> First of all, I completely agree that we should use the
>>>>>>>>>>>>>>> simplest way to
>>>>>>>>>>>>>>>> achieve our goal. To me the goal is the following:
>>>>>>>>>>>>>>>> 1. Clear connector conventions and interfaces.
>>>>>>>>>>>>>>>> 2. The easiness of creating a connector.
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>> Both of them are important to the prosperity of the
>>>>>>>>>>>>>>> connector ecosystem. So
>>>>>>>>>>>>>>>> I'd rather abstract as much as possible on our side to make
>>>>>>>>>>>>>>> the connector
>>>>>>>>>>>>>>>> developer's work lighter. Given this goal, a static util
>>>>>>>>>>>>>>> method approach
>>>>>>>>>>>>>>>> might have a few drawbacks:
>>>>>>>>>>>>>>>> 1. Users still have to construct the metrics by themselves.
>>>>>>>>>>>>>>> (And note that
>>>>>>>>>>>>>>>> this might be erroneous by itself. For example, a customer
>>>>>>>>>>>>>>> wrapper around
>>>>>>>>>>>>>>>> dropwizard meter maybe used instead of MeterView).
>>>>>>>>>>>>>>>> 2. When connector specific metrics are added, it is
>>>>>>>>>>>>>>> difficult to enforce
>>>>>>>>>>>>>>>> the scope to be the same as standard metrics.
>>>>>>>>>>>>>>>> 3. It seems that a method proliferation is inevitable if we
>>>>>>>>>>>>>>> want to apply
>>>>>>>>>>>>>>>> sanity checks. e.g. The metric of numBytesIn was not
>>>>>>>>>>>>>>> registered for a meter.
>>>>>>>>>>>>>>>> 4. Metrics are still defined in random places and hard to
>>>>>>>>>>>>>> track.
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>> The current PR I had was inspired by the Config system in
>>>>>>>>>>>>>>> Kafka, which I
>>>>>>>>>>>>>>>> found pretty handy. In fact it is not only used by Kafka
>>>>>>>>>>>>>>> itself but even
>>>>>>>>>>>>>>>> some other projects that depend on Kafka. I am not saying
>>>>>>>>>>>>>>> this approach is
>>>>>>>>>>>>>>>> perfect. But I think it worths to save the work for
>>>>>>>>>>>>>>> connector writers and
>>>>>>>>>>>>>>>> encourage more systematic implementation. That being said,
>>>>>>>>>>>> I
>>>>>>>>>>>>>>> am fully open
>>>>>>>>>>>>>>>> to suggestions.
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>> Re: Histogram
>>>>>>>>>>>>>>>> I think there are two orthogonal questions around those
>>>>>>>>>>>>>> metrics:
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>> 1. Regardless of the metric type, by just looking at the
>>>>>>>>>>>>>>> meaning of a
>>>>>>>>>>>>>>>> metric, is generic to all connectors? If the answer is yes,
>>>>>>>>>>>>>>> we should
>>>>>>>>>>>>>>>> include the metric into the convention. No matter whether
>>>>>>>>>>>> we
>>>>>>>>>>>>>>> include it
>>>>>>>>>>>>>>>> into the convention or not, some connector implementations
>>>>>>>>>>>>>>> will emit such
>>>>>>>>>>>>>>>> metric. It is better to have a convention than letting each
>>>>>>>>>>>>>>> connector do
>>>>>>>>>>>>>>>> random things.
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>> 2. If a standard metric is a histogram, what should we do?
>>>>>>>>>>>>>>>> I agree that we should make it clear that using histograms
>>>>>>>>>>>>>>> will have
>>>>>>>>>>>>>>>> performance risk. But I do see histogram is useful in some
>>>>>>>>>>>>>>> fine-granularity
>>>>>>>>>>>>>>>> debugging where one do not have the luxury to stop the
>>>>>>>>>>>>>>> system and inject
>>>>>>>>>>>>>>>> more inspection code. So the workaround I am thinking is to
>>>>>>>>>>>>>>> provide some
>>>>>>>>>>>>>>>> implementation suggestions. Assume later on we have a
>>>>>>>>>>>>>>> mechanism of
>>>>>>>>>>>>>>>> selective metrics. In the abstract metrics class we can
>>>>>>>>>>>>>>> disable those
>>>>>>>>>>>>>>>> metrics by default individual connector writers does not
>>>>>>>>>>>>>>> have to do
>>>>>>>>>>>>>>>> anything (this is another advantage of having an
>>>>>>>>>>>>>>> AbstractMetrics instead of
>>>>>>>>>>>>>>>> static util methods.)
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>> I am not sure I fully understand the histogram in the
>>>>>>>>>>>>>>> backend approach. Can
>>>>>>>>>>>>>>>> you explain a bit more? Do you mean emitting the raw data,
>>>>>>>>>>>>>>> e.g. fetchTime
>>>>>>>>>>>>>>>> and emitTime with each record and let the histogram
>>>>>>>>>>>>>>> computation happen in
>>>>>>>>>>>>>>>> the background? Or let the processing thread putting the
>>>>>>>>>>>>>>> values into a
>>>>>>>>>>>>>>>> queue and have a separate thread polling from the queue and
>>>>>>>>>>>>>>> add them into
>>>>>>>>>>>>>>>> the histogram?
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>> Thanks,
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>> Jiangjie (Becket) Qin
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>> On Fri, Feb 22, 2019 at 4:34 PM Chesnay Schepler
>>>>>>>>>>>>>>> <chesnay@apache.org <ma...@apache.org>> wrote:
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>> Re: Flip
>>>>>>>>>>>>>>>>> The very first line under both the main header and Purpose
>>>>>>>>>>>>>>> section
>>>>>>>>>>>>>>>>> describe Flips as "major changes", which this isn't.
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>> Re: complication
>>>>>>>>>>>>>>>>> I'm not arguing against standardization, but again an
>>>>>>>>>>>>>>> over-complicated
>>>>>>>>>>>>>>>>> implementation when a static utility method would be
>>>>>>>>>>>>>>> sufficient.
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>> public static void setupConnectorMetrics(
>>>>>>>>>>>>>>>>> MetricGroup operatorMetricGroup,
>>>>>>>>>>>>>>>>> String connectorName,
>>>>>>>>>>>>>>>>> Optional<Gauge<Long>> numRecordsIn,
>>>>>>>>>>>>>>>>> ...)
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>> This gives you all you need:
>>>>>>>>>>>>>>>>> * a well-defined set of metrics for a connector to opt-in
>>>>>>>>>>>>>>>>> * standardized naming schemes for scope and individual
>>>>>>>>>>>>> metrics
>>>>>>>>>>>>>>>>> * standardize metric types (although personally I'm not
>>>>>>>>>>>>>>> interested in that
>>>>>>>>>>>>>>>>> since metric types should be considered syntactic sugar)
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>> Re: Configurable Histogram
>>>>>>>>>>>>>>>>> If anything they _must_ be turned off by default, but the
>>>>>>>>>>>>>>> metric system is
>>>>>>>>>>>>>>>>> already exposing so many options that I'm not too keen on
>>>>>>>>>>>>>>> adding even more.
>>>>>>>>>>>>>>>>> You have also only addressed my first argument against
>>>>>>>>>>>>>>> histograms
>>>>>>>>>>>>>>>>> (performance), the second one still stands (calculate
>>>>>>>>>>>>>>> histogram in metric
>>>>>>>>>>>>>>>>> backends instead).
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>> On 21.02.2019 16:27, Becket Qin wrote:
>>>>>>>>>>>>>>>>>> Hi Chesnay,
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> Thanks for the comments. I think this is worthy of a FLIP
>>>>>>>>>>>>>>> because it is
>>>>>>>>>>>>>>>>>> public API. According to the FLIP description a FlIP is
>>>>>>>>>>>>>>> required in case
>>>>>>>>>>>>>>>>> of:
>>>>>>>>>>>>>>>>>> - Any change that impacts the public interfaces of
>>>>>>>>>>>>>>> the project
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> and the following entry is found in the definition of
>>>>>>>>>>>>>>> "public interface".
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> - Exposed monitoring information
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> Metrics are critical to any production system. So a clear
>>>>>>>>>>>>>>> metric
>>>>>>>>>>>>>>>>> definition
>>>>>>>>>>>>>>>>>> is important for any serious users. For an organization
>>>>>>>>>>>>>>> with large Flink
>>>>>>>>>>>>>>>>>> installation, change in metrics means great amount of
>>>>>>>>>>>>>>> work. So such
>>>>>>>>>>>>>>>>> changes
>>>>>>>>>>>>>>>>>> do need to be fully discussed and documented.
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> ** Re: Histogram.
>>>>>>>>>>>>>>>>>> We can discuss whether there is a better way to expose
>>>>>>>>>>>>>>> metrics that are
>>>>>>>>>>>>>>>>>> suitable for histograms. My micro-benchmark on various
>>>>>>>>>>>>>>> histogram
>>>>>>>>>>>>>>>>>> implementations also indicates that they are
>>>>>>>>>>>> significantly
>>>>>>>>>>>>>>> slower than
>>>>>>>>>>>>>>>>>> other metric types. But I don't think that means never
>>>>>>>>>>>> use
>>>>>>>>>>>>>>> histogram, but
>>>>>>>>>>>>>>>>>> means use it with caution. For example, we can suggest
>>>>>>>>>>>> the
>>>>>>>>>>>>>>>>> implementations
>>>>>>>>>>>>>>>>>> to turn them off by default and only turn it on for a
>>>>>>>>>>>>>>> small amount of
>>>>>>>>>>>>>>>>> time
>>>>>>>>>>>>>>>>>> when performing some micro-debugging.
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> ** Re: complication:
>>>>>>>>>>>>>>>>>> Connector conventions are essential for Flink ecosystem.
>>>>>>>>>>>>>>> Flink connectors
>>>>>>>>>>>>>>>>>> pool is probably the most important part of Flink, just
>>>>>>>>>>>>>>> like any other
>>>>>>>>>>>>>>>>> data
>>>>>>>>>>>>>>>>>> system. Clear conventions of connectors will help build
>>>>>>>>>>>>>>> Flink ecosystem
>>>>>>>>>>>>>>>>> in
>>>>>>>>>>>>>>>>>> a more organic way.
>>>>>>>>>>>>>>>>>> Take the metrics convention as an example, imagine
>>>>>>>>>>>> someone
>>>>>>>>>>>>>>> has developed
>>>>>>>>>>>>>>>>> a
>>>>>>>>>>>>>>>>>> Flink connector for System foo, and another developer may
>>>>>>>>>>>>>>> have developed
>>>>>>>>>>>>>>>>> a
>>>>>>>>>>>>>>>>>> monitoring and diagnostic framework for Flink which
>>>>>>>>>>>>>>> analyzes the Flink
>>>>>>>>>>>>>>>>> job
>>>>>>>>>>>>>>>>>> performance based on metrics. With a clear metric
>>>>>>>>>>>>>>> convention, those two
>>>>>>>>>>>>>>>>>> projects could be developed independently. Once users put
>>>>>>>>>>>>>>> them together,
>>>>>>>>>>>>>>>>>> it would work without additional modifications. This
>>>>>>>>>>>>>>> cannot be easily
>>>>>>>>>>>>>>>>>> achieved by just defining a few constants.
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> ** Re: selective metrics:
>>>>>>>>>>>>>>>>>> Sure, we can discuss that in a separate thread.
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> @Dawid
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> ** Re: latency / fetchedLatency
>>>>>>>>>>>>>>>>>> The primary purpose of establish such a convention is to
>>>>>>>>>>>>>>> help developers
>>>>>>>>>>>>>>>>>> write connectors in a more compatible way. The convention
>>>>>>>>>>>>>>> is supposed to
>>>>>>>>>>>>>>>>> be
>>>>>>>>>>>>>>>>>> defined more proactively. So when look at the convention,
>>>>>>>>>>>>>>> it seems more
>>>>>>>>>>>>>>>>>> important to see if the concept is applicable to
>>>>>>>>>>>>>>> connectors in general.
>>>>>>>>>>>>>>>>> It
>>>>>>>>>>>>>>>>>> might be true so far only Kafka connector reports
>>>>>>>>>>>> latency.
>>>>>>>>>>>>>>> But there
>>>>>>>>>>>>>>>>> might
>>>>>>>>>>>>>>>>>> be hundreds of other connector implementations in the
>>>>>>>>>>>>>>> Flink ecosystem,
>>>>>>>>>>>>>>>>>> though not in the Flink repo, and some of them also emits
>>>>>>>>>>>>>>> latency. I
>>>>>>>>>>>>>>>>> think
>>>>>>>>>>>>>>>>>> a lot of other sources actually also has an append
>>>>>>>>>>>>>>> timestamp. e.g.
>>>>>>>>>>>>>>>>> database
>>>>>>>>>>>>>>>>>> bin logs and some K-V stores. So I wouldn't be surprised
>>>>>>>>>>>>>>> if some database
>>>>>>>>>>>>>>>>>> connector can also emit latency metrics.
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> Thanks,
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> Jiangjie (Becket) Qin
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> On Thu, Feb 21, 2019 at 10:14 PM Chesnay Schepler
>>>>>>>>>>>>>>> <chesnay@apache.org <ma...@apache.org>>
>>>>>>>>>>>>>>>>>> wrote:
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>> Regarding 2) It doesn't make sense to investigate this
>>>>>>>>>>>> as
>>>>>>>>>>>>>>> part of this
>>>>>>>>>>>>>>>>>>> FLIP. This is something that could be of interest for
>>>>>>>>>>>> the
>>>>>>>>>>>>>>> entire metric
>>>>>>>>>>>>>>>>>>> system, and should be designed for as such.
>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>> Regarding the proposal as a whole:
>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>> Histogram metrics shall not be added to the core of
>>>>>>>>>>>>>>> Flink. They are
>>>>>>>>>>>>>>>>>>> significantly more expensive than other metrics, and
>>>>>>>>>>>>>>> calculating
>>>>>>>>>>>>>>>>>>> histograms in the application is regarded as an
>>>>>>>>>>>>>>> anti-pattern by several
>>>>>>>>>>>>>>>>>>> metric backends, who instead recommend to expose the raw
>>>>>>>>>>>>>>> data and
>>>>>>>>>>>>>>>>>>> calculate the histogram in the backend.
>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>> Second, this seems overly complicated. Given that we
>>>>>>>>>>>>>>> already established
>>>>>>>>>>>>>>>>>>> that not all connectors will export all metrics we are
>>>>>>>>>>>>>>> effectively
>>>>>>>>>>>>>>>>>>> reducing this down to a consistent naming scheme. We
>>>>>>>>>>>>>>> don't need anything
>>>>>>>>>>>>>>>>>>> sophisticated for that; basically just a few constants
>>>>>>>>>>>>>>> that all
>>>>>>>>>>>>>>>>>>> connectors use.
>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>> I'm not convinced that this is worthy of a FLIP.
>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>> On 21.02.2019 14:26, Dawid Wysakowicz wrote:
>>>>>>>>>>>>>>>>>>>> Hi,
>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>> Ad 1. In general I undestand and I agree. But those
>>>>>>>>>>>>>>> particular metrics
>>>>>>>>>>>>>>>>>>>> (latency, fetchLatency), right now would only be
>>>>>>>>>>>>>>> reported if user uses
>>>>>>>>>>>>>>>>>>>> KafkaConsumer with internal timestampAssigner with
>>>>>>>>>>>>>>> StreamCharacteristic
>>>>>>>>>>>>>>>>>>>> set to EventTime, right? That sounds like a very
>>>>>>>>>>>>>>> specific case. I am
>>>>>>>>>>>>>>>>> not
>>>>>>>>>>>>>>>>>>>> sure if we should introduce a generic metric that will
>>>>>>>>>>>> be
>>>>>>>>>>>>>>>>>>>> disabled/absent for most of implementations.
>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>> Ad.2 That sounds like an orthogonal issue, that might
>>>>>>>>>>>>>>> make sense to
>>>>>>>>>>>>>>>>>>>> investigate in the future.
>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>> Best,
>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>> Dawid
>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>> On 21/02/2019 13:20, Becket Qin wrote:
>>>>>>>>>>>>>>>>>>>>> Hi Dawid,
>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>> Thanks for the feedback. That makes sense to me. There
>>>>>>>>>>>>>>> are two cases
>>>>>>>>>>>>>>>>> to
>>>>>>>>>>>>>>>>>>> be
>>>>>>>>>>>>>>>>>>>>> addressed.
>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>> 1. The metrics are supposed to be a guidance. It is
>>>>>>>>>>>>>>> likely that a
>>>>>>>>>>>>>>>>>>> connector
>>>>>>>>>>>>>>>>>>>>> only supports some but not all of the metrics. In that
>>>>>>>>>>>>>>> case, each
>>>>>>>>>>>>>>>>>>> connector
>>>>>>>>>>>>>>>>>>>>> implementation should have the freedom to decide which
>>>>>>>>>>>>>>> metrics are
>>>>>>>>>>>>>>>>>>>>> reported. For the metrics that are supported, the
>>>>>>>>>>>>>>> guidance should be
>>>>>>>>>>>>>>>>>>>>> followed.
>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>> 2. Sometimes users may want to disable certain metrics
>>>>>>>>>>>>>>> for some reason
>>>>>>>>>>>>>>>>>>>>> (e.g. performance / reprocessing of data). A generic
>>>>>>>>>>>>>>> mechanism should
>>>>>>>>>>>>>>>>> be
>>>>>>>>>>>>>>>>>>>>> provided to allow user choose which metrics are
>>>>>>>>>>>>>>> reported. This
>>>>>>>>>>>>>>>>> mechanism
>>>>>>>>>>>>>>>>>>>>> should also be honored by the connector
>>>>>>>>>>>> implementations.
>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>> Does this sound reasonable to you?
>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>> Thanks,
>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>> Jiangjie (Becket) Qin
>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>> On Thu, Feb 21, 2019 at 4:22 PM Dawid Wysakowicz <
>>>>>>>>>>>>>>>>>>> dwysakowicz@apache.org <ma...@apache.org>>
>>>>>>>>>>>>>>>>>>>>> wrote:
>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>> Hi,
>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>> Generally I like the idea of having a unified,
>>>>>>>>>>>>>>> standard set of
>>>>>>>>>>>>>>>>> metrics
>>>>>>>>>>>>>>>>>>> for
>>>>>>>>>>>>>>>>>>>>>> all connectors. I have some slight concerns about
>>>>>>>>>>>>>>> fetchLatency and
>>>>>>>>>>>>>>>>>>>>>> latency though. They are computed based on EventTime
>>>>>>>>>>>>>>> which is not a
>>>>>>>>>>>>>>>>>>> purely
>>>>>>>>>>>>>>>>>>>>>> technical feature. It depends often on some business
>>>>>>>>>>>>>>> logic, might be
>>>>>>>>>>>>>>>>>>> absent
>>>>>>>>>>>>>>>>>>>>>> or defined after source. Those metrics could also
>>>>>>>>>>>>>>> behave in a weird
>>>>>>>>>>>>>>>>>>> way in
>>>>>>>>>>>>>>>>>>>>>> case of replaying backlog. Therefore I am not sure if
>>>>>>>>>>>>>>> we should
>>>>>>>>>>>>>>>>> include
>>>>>>>>>>>>>>>>>>>>>> those metrics by default. Maybe we could at least
>>>>>>>>>>>>>>> introduce a feature
>>>>>>>>>>>>>>>>>>>>>> switch for them? What do you think?
>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>> Best,
>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>> Dawid
>>>>>>>>>>>>>>>>>>>>>> On 21/02/2019 03:13, Becket Qin wrote:
>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>> Bump. If there is no objections to the proposed
>>>>>>>>>>>>>>> metrics. I'll start a
>>>>>>>>>>>>>>>>>>>>>> voting thread later toady.
>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>> Thanks,
>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>> Jiangjie (Becket) Qin
>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>> On Mon, Feb 11, 2019 at 8:17 PM Becket Qin
>>>>>>>>>>>>>>> <becket.qin@gmail.com <ma...@gmail.com>> <
>>>>>>>>>>>>>>>>>>> becket.qin@gmail.com <ma...@gmail.com>>
>>>>>>>>>>>>> wrote:
>>>>>>>>>>>>>>>>>>>>>> Hi folks,
>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>> I would like to start the FLIP discussion thread
>>>>>>>>>>>> about
>>>>>>>>>>>>>>> standardize
>>>>>>>>>>>>>>>>> the
>>>>>>>>>>>>>>>>>>>>>> connector metrics.
>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>> In short, we would like to provide a convention of
>>>>>>>>>>>>>>> Flink connector
>>>>>>>>>>>>>>>>>>>>>> metrics. It will help simplify the monitoring and
>>>>>>>>>>>>>>> alerting on Flink
>>>>>>>>>>>>>>>>>>> jobs.
>>>>>>>>>>>>>>>>>>>>>> The FLIP link is following:
>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>
>>>>>>>>>>>>>
>>>>>>>>>>>>
>>>>>>>>>>
>>>>>>>
>>>>>
>>> https://cwiki.apache.org/confluence/display/FLINK/FLIP-33%3A+Standardize+Connector+Metrics
>>>>>>>>>>>>>>>>>>>>>> Thanks,
>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>> Jiangjie (Becket) Qin
>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>
>>>>>>>>>>>>>>
>>>>>>>>>>>>>
>>>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>
>>>>>
>>>>>
>>>
>>>
Re: [DISCUSS] FLIP-33: Standardize connector metrics
Posted by Becket Qin <be...@gmail.com>.
Thanks all for the feedback and discussion.
Since there wasn't any concern raised, I've started the voting thread for
this FLIP, but please feel free to continue the discussion here if you
think something still needs to be addressed.
Thanks,
Jiangjie (Becket) Qin
On Mon, Jun 10, 2019 at 9:10 AM Becket Qin <be...@gmail.com> wrote:
> Hi Piotr,
>
> Thanks for the comments. Yes, you are right. Users will have to look at
> other metrics to decide whether the pipeline is healthy or not in the first
> place before they can use the time-based metric to fix the bottleneck.
>
> I agree that once we have FLIP-27 ready, some of the metrics can just be
> reported by the abstract implementation.
>
> I've updated FLIP-33 wiki page to add the pendingBytes and pendingRecords
> metric. Please let me know if you have any concern over the updated metric
> convention proposal.
>
> @Chesnay Schepler <ch...@apache.org> @Stephan Ewen
> <st...@ververica.com> will you also have time to take a look at the
> proposed metric convention? If there is no further concern I'll start a
> voting thread for this FLIP in two days.
>
> Thanks,
>
> Jiangjie (Becket) Qin
>
>
>
> On Wed, Jun 5, 2019 at 6:54 PM Piotr Nowojski <pi...@ververica.com> wrote:
>
>> Hi Becket,
>>
>> Thanks for the answer :)
>>
>> > By time-based metric, I meant the portion of time spent on producing the
>> > record to downstream. For example, a source connector can report that
>> it's
>> > spending 80% of time to emit record to downstream processing pipeline.
>> In
>> > another case, a sink connector may report that its spending 30% of time
>> > producing the records to the external system.
>> >
>> > This is in some sense equivalent to the buffer usage metric:
>>
>> > - 80% of time spent on emitting records to downstream ---> downstream
>> > node is bottleneck ---> output buffer is probably full.
>> > - 30% of time spent on emitting records to downstream ---> downstream
>> > node is not bottleneck ---> output buffer is probably not full.
>>
>> If by “time spent on emitting records to downstream” you understand
>> “waiting on back pressure”, then I see your point. And I agree that some
>> kind of ratio/time based metric gives you more information. However under
>> “time spent on emitting records to downstream” might be hidden the
>> following (extreme) situation:
>>
>> 1. Job is barely able to handle influx of records, there is 99%
>> CPU/resource usage in the cluster, but nobody is
>> bottlenecked/backpressured, all output buffers are empty, everybody is
>> waiting in 1% of it’s time for more records to process.
>> 2. 80% time can still be spent on "down stream operators”, because they
>> are the CPU intensive operations, but this doesn’t mean that increasing the
>> parallelism down the stream will help with anything there. To the contrary,
>> increasing parallelism of the source operator might help to increase
>> resource utilisation up to 100%.
>>
>> However, this “time based/ratio” approach can be extended to in/output
>> buffer usage. Besides collecting an information that input/output buffer is
>> full/empty, we can probe profile how often are buffer empty/full. If output
>> buffer is full 1% of times, there is almost no back pressure. If it’s full
>> 80% of times, there is some back pressure, if it’s full 99.9% of times,
>> there is huge back pressure.
>>
>> Now for autoscaling you could compare the input & output buffers fill
>> ratio:
>>
>> 1. Both are high, the source of bottleneck is down the stream
>> 2. Output is low, input is high, this is the bottleneck and the higher
>> the difference, the bigger source of bottleneck is this is operator/task
>> 3. Output is high, input is low - there was some load spike that we are
>> currently finishing to process
>>
>>
>>
>> But long story short, we are probably diverging from the topic of this
>> discussion, and we can discuss this at some later point.
>>
>> For now, for sources:
>>
>> as I wrote before, +1 for:
>> - pending.bytes, Gauge
>> - pending.messages, Gauge
>>
>> When we will be developing/discussing SourceReader from FLIP-27 we might
>> then add:
>>
>> - in-memory.buffer.usage (0 - 100%)
>>
>> Which will be estimated automatically by Flink while user will be able to
>> override/provide better estimation.
>>
>> Piotrek
>>
>> > On 5 Jun 2019, at 05:42, Becket Qin <be...@gmail.com> wrote:
>> >
>> > Hi Piotr,
>> >
>> > Thanks for the explanation. Please see some clarifications below.
>> >
>> > By time-based metric, I meant the portion of time spent on producing the
>> > record to downstream. For example, a source connector can report that
>> it's
>> > spending 80% of time to emit record to downstream processing pipeline.
>> In
>> > another case, a sink connector may report that its spending 30% of time
>> > producing the records to the external system.
>> >
>> > This is in some sense equivalent to the buffer usage metric:
>> > - 80% of time spent on emitting records to downstream ---> downstream
>> > node is bottleneck ---> output buffer is probably full.
>> > - 30% of time spent on emitting records to downstream ---> downstream
>> > node is not bottleneck ---> output buffer is probably not full.
>> >
>> > However, the time-based metric has a few advantages that the buffer
>> usage
>> > metric may not have.
>> >
>> > 1. Buffer usage metric may not be applicable to all the connector
>> > implementations, while reporting time-based metric are always doable.
>> > Some source connectors may not have any input buffer, or they may use
>> some
>> > third party library that does not expose the input buffer at all.
>> > Similarly, for sink connectors, the implementation may not have any
>> output
>> > buffer, or the third party library does not expose such buffer.
>> >
>> > 2. Although both type of metrics can detect bottleneck, time-based
>> metrics
>> > can be used to generate a more informed action to remove the bottleneck.
>> > For example, when the downstream is bottleneck, the output buffer usage
>> > metric is likely to be 100%, and the input buffer usage might be 0%.
>> That
>> > means we don't know what is the suitable parallelism to lift the
>> > bottleneck. The time-based metric, on the other hand, would give useful
>> > information, e.g. if 80% of time was spent on emitting records, we can
>> > roughly increase the downstream node parallelism by 4 times.
>> >
>> > Admittedly, the time-based metrics are more expensive than buffer
>> usage. So
>> > we may have to do some sampling to reduce the cost. But in general,
>> using
>> > time-based metrics seems worth adding.
>> >
>> > That being said, I don't think buffer usage metric and time-based
>> metrics
>> > are mutually exclusive. We can probably have both. It is just that in
>> > practice, features like auto-scaling might prefer time-based metrics for
>> > the reason stated above.
>> >
>> >> 1. Define the metrics that would allow us to manually detect
>> bottlenecks.
>> > As I wrote, we already have them in most of the places, except of
>> > sources/sinks.
>> >> 2. Use those metrics, to automatically detect bottlenecks. Currently we
>> > are only automatically detecting back pressure and reporting it to the
>> user
>> > in web UI (is it exposed as a metric at all?). Detecting the root cause
>> of
>> > the back pressure (bottleneck) is one step further.
>> >> 3. Use the knowledge about where exactly the bottleneck is located, to
>> > try to do something with it.
>> >
>> > As explained above, I think time-based metric also addresses item 1 and
>> > item 2.
>> >
>> > Any thoughts？
>> >
>> > Thanks,
>> >
>> > Jiangjie (Becket) Qin
>> >
>> >
>> >
>> > On Mon, Jun 3, 2019 at 4:14 PM Piotr Nowojski <pi...@ververica.com>
>> wrote:
>> >
>> >> Hi again :)
>> >>
>> >>> - pending.bytes, Gauge
>> >>> - pending.messages, Gauge
>> >>
>> >>
>> >> +1
>> >>
>> >> And true, instead of overloading one of the metric it is better when
>> user
>> >> can choose to provide only one of them.
>> >>
>> >> Re 2:
>> >>
>> >>> If I understand correctly, this metric along with the pending mesages
>> /
>> >>> bytes would answer the questions of:
>> >>
>> >>> - Does the connector consume fast enough? Lagging behind + empty
>> buffer
>> >> =
>> >>> cannot consume fast enough.
>> >>> - Does the connector emit fast enough? Lagging behind + full buffer =
>> >>> cannot emit fast enough, i.e. the Flink pipeline is slow.
>> >>
>> >> Yes, exactly. This can also be used to support decisions like changing
>> the
>> >> parallelism of the sources and/or down stream operators.
>> >>
>> >> I’m not sure if I understand your proposal with time based
>> measurements.
>> >> Maybe I’m missing something, but I do not see how measuring time alone
>> >> could answer the problem: where is the bottleneck. Time spent on the
>> >> next/emit might be short or long (depending on how heavy to process the
>> >> record is) and the source can still be bottlenecked/back pressured or
>> not.
>> >> Usually the easiest and the most reliable way how to detect
>> bottlenecks is
>> >> by checking usage of input & output buffers, since when input buffer is
>> >> full while output buffer is empty, that’s the definition of a
>> bottleneck.
>> >> Also this is usually very easy and cheap to measure (it works
>> effectively
>> >> the same way as current’s Flink back pressure monitoring, but more
>> cleanly,
>> >> without probing thread’s stack traces).
>> >>
>> >> Also keep in mind that we are already using the buffer usage metrics
>> for
>> >> detecting the bottlenecks in Flink’s internal network exchanges (manual
>> >> work). That’s the reason why I wanted to extend this to sources/sinks,
>> >> since they are currently our blind spot.
>> >>
>> >>> One feature we are currently working on to scale Flink automatically
>> >> relies
>> >>> on some metrics answering the same question
>> >>
>> >> That would be very helpful feature. I think in order to achieve that we
>> >> would need to:
>> >> 1. Define the metrics that would allow us to manually detect
>> bottlenecks.
>> >> As I wrote, we already have them in most of the places, except of
>> >> sources/sinks.
>> >> 2. Use those metrics, to automatically detect bottlenecks. Currently we
>> >> are only automatically detecting back pressure and reporting it to the
>> user
>> >> in web UI (is it exposed as a metric at all?). Detecting the root
>> cause of
>> >> the back pressure (bottleneck) is one step further.
>> >> 3. Use the knowledge about where exactly the bottleneck is located, to
>> try
>> >> to do something with it.
>> >>
>> >> I think you are aiming for point 3., but before we reach it, we are
>> still
>> >> missing 1. & 2. Also even if we have 3., there is a value in 1 & 2 for
>> >> manual analysis/dashboards.
>> >>
>> >> However, having the knowledge of where the bottleneck is, doesn’t
>> >> necessarily mean that we know what we can do about it. For example
>> >> increasing parallelism might or might not help with anything (data
>> skew,
>> >> bottleneck on some resource that does not scale), but this remark
>> applies
>> >> always, regardless of the way how did we detect the bottleneck.
>> >>
>> >> Piotrek
>> >>
>> >>> On 3 Jun 2019, at 06:16, Becket Qin <be...@gmail.com> wrote:
>> >>>
>> >>> Hi Piotr,
>> >>>
>> >>> Thanks for the suggestion. Some thoughts below:
>> >>>
>> >>> Re 1: The pending messages / bytes.
>> >>> I completely agree these are very useful metrics and we should expect
>> the
>> >>> connector to report. WRT the way to expose them, it seems more
>> consistent
>> >>> to add two metrics instead of adding a method (unless there are other
>> use
>> >>> cases other than metric reporting). So we can add the following two
>> >> metrics.
>> >>> - pending.bytes, Gauge
>> >>> - pending.messages, Gauge
>> >>> Applicable connectors can choose to report them. These two metrics
>> along
>> >>> with latency should be sufficient for users to understand the progress
>> >> of a
>> >>> connector.
>> >>>
>> >>>
>> >>> Re 2: Number of buffered data in-memory of the connector
>> >>> If I understand correctly, this metric along with the pending mesages
>> /
>> >>> bytes would answer the questions of:
>> >>> - Does the connector consume fast enough? Lagging behind + empty
>> buffer
>> >> =
>> >>> cannot consume fast enough.
>> >>> - Does the connector emit fast enough? Lagging behind + full buffer =
>> >>> cannot emit fast enough, i.e. the Flink pipeline is slow.
>> >>>
>> >>> One feature we are currently working on to scale Flink automatically
>> >> relies
>> >>> on some metrics answering the same question, more specifically, we are
>> >>> profiling the time spent on .next() method (time to consume) and the
>> time
>> >>> spent on .collect() method (time to emit / process). One advantage of
>> >> such
>> >>> method level time cost allows us to calculate the parallelism
>> required to
>> >>> keep up in case their is a lag.
>> >>>
>> >>> However, one concern I have regarding such metric is that they are
>> >>> implementation specific. Either profiling on the method time, or
>> >> reporting
>> >>> buffer usage assumes the connector are implemented in such a way. A
>> >>> slightly better solution might be have the following metric:
>> >>>
>> >>> - EmitTimeRatio (or FetchTimeRatio): The time spent on emitting
>> >>> records / Total time elapsed.
>> >>>
>> >>> This assumes that the source connectors have to emit the records to
>> the
>> >>> downstream at some point. The emission may take some time ( e.g. go
>> >> through
>> >>> chained operators). And the rest of the time are spent to prepare the
>> >>> record to emit, including time for consuming and format conversion,
>> etc.
>> >>> Ideally, we'd like to see the time spent on record fetch and emit to
>> be
>> >>> about the same, so no one is bottleneck for the other.
>> >>>
>> >>> The downside of these time based metrics is additional overhead to get
>> >> the
>> >>> time, therefore sampling might be needed. But in practice I feel such
>> >> time
>> >>> based metric might be more useful if we want to take action.
>> >>>
>> >>>
>> >>> I think we should absolutely add metrics in (1) to the metric
>> convention.
>> >>> We could also add the metrics mentioned in (2) if we reach consensus
>> on
>> >>> that. What do you think?
>> >>>
>> >>> Thanks,
>> >>>
>> >>> Jiangjie (Becket) Qin
>> >>>
>> >>>
>> >>> On Fri, May 31, 2019 at 4:26 PM Piotr Nowojski <pi...@ververica.com>
>> >> wrote:
>> >>>
>> >>>> Hey Becket,
>> >>>>
>> >>>> Re 1a) and 1b) +1 from my side.
>> >>>>
>> >>>> I’ve discussed this issue:
>> >>>>
>> >>>>>>>
>> >>>>>>> 2. It would be nice to have metrics, that allow us to check the
>> cause
>> >>>> of
>> >>>>>>> back pressure:
>> >>>>>>> a) for sources, length of input queue (in bytes? Or boolean
>> >>>>>>> hasSomethingl/isEmpty)
>> >>>>>>> b) for sinks, length of output queue (in bytes? Or boolean
>> >>>>>>> hasSomething/isEmpty)
>> >>>>
>> >>>> With Nico at some lengths and he also saw the benefits of them. We
>> also
>> >>>> have more concrete proposal for that.
>> >>>>
>> >>>> Actually there are two really useful metrics, that we are missing
>> >>>> currently:
>> >>>>
>> >>>> 1. Number of data/records/bytes in the backlog to process. For
>> example
>> >>>> remaining number of bytes in unread files. Or pending data in Kafka
>> >> topics.
>> >>>> 2. Number of buffered data in-memory of the connector, that are
>> waiting
>> >> to
>> >>>> be processed pushed to Flink pipeline.
>> >>>>
>> >>>> Re 1:
>> >>>> This would have to be a metric provided directly by a connector. It
>> >> could
>> >>>> be an undefined `int`:
>> >>>>
>> >>>> `int backlog` - estimate of pending work.
>> >>>>
>> >>>> “Undefined” meaning that it would be up to a connector to decided
>> >> whether
>> >>>> it’s measured in bytes, records, pending files or whatever it is
>> >> possible
>> >>>> to provide by the connector. This is because I assume not every
>> >> connector
>> >>>> can provide exact number and for some of them it might be impossible
>> to
>> >>>> provide records number of bytes count.
>> >>>>
>> >>>> Re 2:
>> >>>> This metric could be either provided by a connector, or calculated
>> >> crudely
>> >>>> by Flink:
>> >>>>
>> >>>> `float bufferUsage` - value from [0.0, 1.0] range
>> >>>>
>> >>>> Percentage of used in memory buffers, like in Kafka’s handover.
>> >>>>
>> >>>> It could be crudely implemented by Flink with FLIP-27
>> >>>> SourceReader#isAvailable. If SourceReader is not available reported
>> >>>> `bufferUsage` could be 0.0. If it is available, it could be 1.0. I
>> think
>> >>>> this would be a good enough estimation for most of the use cases
>> (that
>> >>>> could be overloaded and implemented better if desired). Especially
>> >> since we
>> >>>> are reporting only probed values: if probed values are almost always
>> >> “1.0”,
>> >>>> it would mean that we have a back pressure. If they are almost always
>> >>>> “0.0”, there is probably no back pressure at the sources.
>> >>>>
>> >>>> What do you think about this?
>> >>>>
>> >>>> Piotrek
>> >>>>
>> >>>>> On 30 May 2019, at 11:41, Becket Qin <be...@gmail.com> wrote:
>> >>>>>
>> >>>>> Hi all,
>> >>>>>
>> >>>>> Thanks a lot for all the feedback and comments. I'd like to continue
>> >> the
>> >>>>> discussion on this FLIP.
>> >>>>>
>> >>>>> I updated the FLIP-33 wiki to remove all the histogram metrics from
>> the
>> >>>>> first version of metric convention due to the performance concern.
>> The
>> >>>> plan
>> >>>>> is to introduce them later when we have a mechanism to opt in/out
>> >>>> metrics.
>> >>>>> At that point, users can decide whether they want to pay the cost to
>> >> get
>> >>>>> the metric or not.
>> >>>>>
>> >>>>> As Stephan suggested, for this FLIP, let's first try to agree on the
>> >>>> small
>> >>>>> list of conventional metrics that connectors should follow.
>> >>>>> Just to be clear, the purpose of the convention is not to enforce
>> every
>> >>>>> connector to report all these metrics, but to provide a guidance in
>> >> case
>> >>>>> these metrics are reported by some connectors.
>> >>>>>
>> >>>>>
>> >>>>> @ Stephan & Chesnay,
>> >>>>>
>> >>>>> Regarding the duplication of `RecordsIn` metric in operator / task
>> >>>>> IOMetricGroups, from what I understand, for source operator, it is
>> >>>> actually
>> >>>>> the SourceFunction that reports the operator level
>> >>>>> RecordsIn/RecordsInPerSecond metric. So they are essentially the
>> same
>> >>>>> metric in the operator level IOMetricGroup. Similarly for the Sink
>> >>>>> operator, the operator level RecordsOut/RecordsOutPerSecond metrics
>> are
>> >>>>> also reported by the Sink function. I marked them as existing in the
>> >>>>> FLIP-33 wiki page. Please let me know if I misunderstood.
>> >>>>>
>> >>>>> Thanks,
>> >>>>>
>> >>>>> Jiangjie (Becket) Qin
>> >>>>>
>> >>>>>
>> >>>>> On Thu, May 30, 2019 at 5:16 PM Becket Qin <be...@gmail.com>
>> >> wrote:
>> >>>>>
>> >>>>>> Hi Piotr,
>> >>>>>>
>> >>>>>> Thanks a lot for the feedback.
>> >>>>>>
>> >>>>>> 1a) I guess you are referring to the part that "original system
>> >> specific
>> >>>>>> metrics should also be reported". The performance impact depends on
>> >> the
>> >>>>>> implementation. An efficient implementation would only record the
>> >> metric
>> >>>>>> once, but report them with two different metric names. This is
>> >> unlikely
>> >>>> to
>> >>>>>> hurt performance.
>> >>>>>>
>> >>>>>> 1b) Yes, I agree that we should avoid adding overhead to the
>> critical
>> >>>> path
>> >>>>>> by all means. This is sometimes a tradeoff, running blindly without
>> >> any
>> >>>>>> metric gives best performance, but sometimes might be frustrating
>> when
>> >>>> we
>> >>>>>> debug some issues.
>> >>>>>>
>> >>>>>> 2. The metrics are indeed very useful. Are they supposed to be
>> >> reported
>> >>>> by
>> >>>>>> the connectors or Flink itself? At this point FLIP-33 is more
>> focused
>> >> on
>> >>>>>> provide a guidance to the connector authors on the metrics
>> reporting.
>> >>>> That
>> >>>>>> said, after FLIP-27, I think we should absolutely report these
>> metrics
>> >>>> in
>> >>>>>> the abstract implementation. In any case, the metric convention in
>> >> this
>> >>>>>> list are expected to evolve over time.
>> >>>>>>
>> >>>>>> Thanks,
>> >>>>>>
>> >>>>>> Jiangjie (Becket) Qin
>> >>>>>>
>> >>>>>> On Tue, May 28, 2019 at 6:24 PM Piotr Nowojski <
>> piotr@ververica.com>
>> >>>>>> wrote:
>> >>>>>>
>> >>>>>>> Hi,
>> >>>>>>>
>> >>>>>>> Thanks for the proposal and driving the effort here Becket :) I’ve
>> >> read
>> >>>>>>> through the FLIP-33 [1], and here are couple of my thoughts.
>> >>>>>>>
>> >>>>>>> Big +1 for standardising the metric names between connectors, it
>> will
>> >>>>>>> definitely help us and users a lot.
>> >>>>>>>
>> >>>>>>> Issues/questions/things to discuss that I’ve thought of:
>> >>>>>>>
>> >>>>>>> 1a. If we are about to duplicate some metrics, can this become a
>> >>>>>>> performance issue?
>> >>>>>>> 1b. Generally speaking, we should make sure that collecting those
>> >>>> metrics
>> >>>>>>> is as non intrusive as possible, especially that they will need
>> to be
>> >>>>>>> updated once per record. (They might be collected more rarely with
>> >> some
>> >>>>>>> overhead, but the hot path of updating it per record will need to
>> be
>> >> as
>> >>>>>>> quick as possible). That includes both avoiding heavy computation
>> on
>> >>>> per
>> >>>>>>> record path: histograms?, measuring time for time based metrics
>> (per
>> >>>>>>> second) (System.currentTimeMillis() depending on the
>> implementation
>> >> can
>> >>>>>>> invoke a system call)
>> >>>>>>>
>> >>>>>>> 2. It would be nice to have metrics, that allow us to check the
>> cause
>> >>>> of
>> >>>>>>> back pressure:
>> >>>>>>> a) for sources, length of input queue (in bytes? Or boolean
>> >>>>>>> hasSomethingl/isEmpty)
>> >>>>>>> b) for sinks, length of output queue (in bytes? Or boolean
>> >>>>>>> hasSomething/isEmpty)
>> >>>>>>>
>> >>>>>>> a) is useful in a scenario when we are processing backlog of
>> records,
>> >>>> all
>> >>>>>>> of the internal Flink’s input/output network buffers are empty,
>> and
>> >> we
>> >>>> want
>> >>>>>>> to check whether the external source system is the bottleneck
>> >> (source’s
>> >>>>>>> input queue will be empty), or if the Flink’s connector is the
>> >>>> bottleneck
>> >>>>>>> (source’s input queues will be full).
>> >>>>>>> b) similar story. Backlog of records, but this time all of the
>> >> internal
>> >>>>>>> Flink’s input/ouput network buffers are full, and we want o check
>> >>>> whether
>> >>>>>>> the external sink system is the bottleneck (sink output queues are
>> >>>> full),
>> >>>>>>> or if the Flink’s connector is the bottleneck (sink’s output
>> queues
>> >>>> will be
>> >>>>>>> empty)
>> >>>>>>>
>> >>>>>>> It might be sometimes difficult to provide those metrics, so they
>> >> could
>> >>>>>>> be optional, but if we could provide them, it would be really
>> >> helpful.
>> >>>>>>>
>> >>>>>>> Piotrek
>> >>>>>>>
>> >>>>>>> [1]
>> >>>>>>>
>> >>>>
>> >>
>> https://cwiki.apache.org/confluence/display/FLINK/FLIP-33:+Standardize+Connector+Metrics
>> >>>>>>> <
>> >>>>>>>
>> >>>>
>> >>
>> https://cwiki.apache.org/confluence/display/FLINK/FLIP-33:+Standardize+Connector+Metrics
>> >>>>>>>>
>> >>>>>>>
>> >>>>>>>> On 24 Apr 2019, at 13:28, Stephan Ewen <se...@apache.org> wrote:
>> >>>>>>>>
>> >>>>>>>> I think this sounds reasonable.
>> >>>>>>>>
>> >>>>>>>> Let's keep the "reconfiguration without stopping the job" out of
>> >> this,
>> >>>>>>>> because that would be a super big effort and if we approach that,
>> >> then
>> >>>>>>> in
>> >>>>>>>> more generic way rather than specific to connector metrics.
>> >>>>>>>>
>> >>>>>>>> I would suggest to look at the following things before starting
>> with
>> >>>> any
>> >>>>>>>> implementation work:
>> >>>>>>>>
>> >>>>>>>> - Try and find a committer to support this, otherwise it will be
>> >> hard
>> >>>>>>> to
>> >>>>>>>> make progress
>> >>>>>>>> - Start with defining a smaller set of "core metrics" and extend
>> the
>> >>>>>>> set
>> >>>>>>>> later. I think that is easier than now blocking on reaching
>> >> consensus
>> >>>>>>> on a
>> >>>>>>>> large group of metrics.
>> >>>>>>>> - Find a solution to the problem Chesnay mentioned, that the
>> >> "records
>> >>>>>>> in"
>> >>>>>>>> metric is somehow overloaded and exists already in the IO Metric
>> >>>> group.
>> >>>>>>>>
>> >>>>>>>>
>> >>>>>>>> On Mon, Mar 25, 2019 at 7:16 AM Becket Qin <becket.qin@gmail.com
>> >
>> >>>>>>> wrote:
>> >>>>>>>>
>> >>>>>>>>> Hi Stephan,
>> >>>>>>>>>
>> >>>>>>>>> Thanks a lot for the feedback. All makes sense.
>> >>>>>>>>>
>> >>>>>>>>> It is a good suggestion to simply have an onRecord(numBytes,
>> >>>> eventTime)
>> >>>>>>>>> method for connector writers. It should meet most of the
>> >>>> requirements,
>> >>>>>>>>> individual
>> >>>>>>>>>
>> >>>>>>>>> The configurable metrics feature is something really useful,
>> >>>>>>> especially if
>> >>>>>>>>> we can somehow make it dynamically configurable without stopping
>> >> the
>> >>>>>>> jobs.
>> >>>>>>>>> It might be better to make it a separate discussion because it
>> is a
>> >>>>>>> more
>> >>>>>>>>> generic feature instead of only for connectors.
>> >>>>>>>>>
>> >>>>>>>>> So in order to make some progress, in this FLIP we can limit the
>> >>>>>>> discussion
>> >>>>>>>>> scope to the connector related items:
>> >>>>>>>>>
>> >>>>>>>>> - the standard connector metric names and types.
>> >>>>>>>>> - the abstract ConnectorMetricHandler interface
>> >>>>>>>>>
>> >>>>>>>>> I'll start a separate thread to discuss other general metric
>> >> related
>> >>>>>>>>> enhancement items including:
>> >>>>>>>>>
>> >>>>>>>>> - optional metrics
>> >>>>>>>>> - dynamic metric configuration
>> >>>>>>>>> - potential combination with rate limiter
>> >>>>>>>>>
>> >>>>>>>>> Does this plan sound reasonable?
>> >>>>>>>>>
>> >>>>>>>>> Thanks,
>> >>>>>>>>>
>> >>>>>>>>> Jiangjie (Becket) Qin
>> >>>>>>>>>
>> >>>>>>>>> On Sat, Mar 23, 2019 at 5:53 AM Stephan Ewen <se...@apache.org>
>> >>>> wrote:
>> >>>>>>>>>
>> >>>>>>>>>> Ignoring for a moment implementation details, this connector
>> >> metrics
>> >>>>>>> work
>> >>>>>>>>>> is a really good thing to do, in my opinion
>> >>>>>>>>>>
>> >>>>>>>>>> The questions "oh, my job seems to be doing nothing, I am
>> looking
>> >> at
>> >>>>>>> the
>> >>>>>>>>> UI
>> >>>>>>>>>> and the 'records in' value is still zero" is in the top three
>> >>>> support
>> >>>>>>>>>> questions I have been asked personally.
>> >>>>>>>>>> Introspection into "how far is the consumer lagging behind"
>> (event
>> >>>>>>> time
>> >>>>>>>>>> fetch latency) came up many times as well.
>> >>>>>>>>>>
>> >>>>>>>>>> So big +1 to solving this problem.
>> >>>>>>>>>>
>> >>>>>>>>>> About the exact design - I would try to go for the following
>> >>>>>>> properties:
>> >>>>>>>>>>
>> >>>>>>>>>> - keep complexity of of connectors. Ideally the metrics handler
>> >> has
>> >>>> a
>> >>>>>>>>>> single onRecord(numBytes, eventTime) method or so, and
>> everything
>> >>>>>>> else is
>> >>>>>>>>>> internal to the handler. That makes it dead simple for the
>> >>>> connector.
>> >>>>>>> We
>> >>>>>>>>>> can also think of an extensive scheme for connector specific
>> >>>> metrics.
>> >>>>>>>>>>
>> >>>>>>>>>> - make it configurable on the job it cluster level which
>> metrics
>> >> the
>> >>>>>>>>>> handler internally creates when that method is invoked.
>> >>>>>>>>>>
>> >>>>>>>>>> What do you think?
>> >>>>>>>>>>
>> >>>>>>>>>> Best,
>> >>>>>>>>>> Stephan
>> >>>>>>>>>>
>> >>>>>>>>>>
>> >>>>>>>>>> On Thu, Mar 21, 2019 at 10:42 AM Chesnay Schepler <
>> >>>> chesnay@apache.org
>> >>>>>>>>
>> >>>>>>>>>> wrote:
>> >>>>>>>>>>
>> >>>>>>>>>>> As I said before, I believe this to be over-engineered and
>> have
>> >> no
>> >>>>>>>>>>> interest in this implementation.
>> >>>>>>>>>>>
>> >>>>>>>>>>> There are conceptual issues like defining a duplicate
>> >>>>>>>>> numBytesIn(PerSec)
>> >>>>>>>>>>> metric that already exists for each operator.
>> >>>>>>>>>>>
>> >>>>>>>>>>> On 21.03.2019 06:13, Becket Qin wrote:
>> >>>>>>>>>>>> A few updates to the thread. I uploaded a patch[1] as a
>> complete
>> >>>>>>>>>>>> example of how users can use the metrics in the future.
>> >>>>>>>>>>>>
>> >>>>>>>>>>>> Some thoughts below after taking a look at the
>> >> AbstractMetricGroup
>> >>>>>>>>> and
>> >>>>>>>>>>>> its subclasses.
>> >>>>>>>>>>>>
>> >>>>>>>>>>>> This patch intends to provide convenience for Flink connector
>> >>>>>>>>>>>> implementations to follow metrics standards proposed in
>> FLIP-33.
>> >>>> It
>> >>>>>>>>>>>> also try to enhance the metric management in general way to
>> help
>> >>>>>>>>> users
>> >>>>>>>>>>>> with:
>> >>>>>>>>>>>>
>> >>>>>>>>>>>> 1. metric definition
>> >>>>>>>>>>>> 2. metric dependencies check
>> >>>>>>>>>>>> 3. metric validation
>> >>>>>>>>>>>> 4. metric control (turn on / off particular metrics)
>> >>>>>>>>>>>>
>> >>>>>>>>>>>> This patch wraps |MetricGroup| to extend the functionality of
>> >>>>>>>>>>>> |AbstractMetricGroup| and its subclasses. The
>> >>>>>>>>>>>> |AbstractMetricGroup| mainly focus on the metric group
>> >> hierarchy,
>> >>>>>>> but
>> >>>>>>>>>>>> does not really manage the metrics other than keeping them
>> in a
>> >>>> Map.
>> >>>>>>>>>>>>
>> >>>>>>>>>>>> Ideally we should only have one entry point for the metrics.
>> >>>>>>>>>>>>
>> >>>>>>>>>>>> Right now the entry point is |AbstractMetricGroup|. However,
>> >>>> besides
>> >>>>>>>>>>>> the missing functionality mentioned above,
>> |AbstractMetricGroup|
>> >>>>>>>>> seems
>> >>>>>>>>>>>> deeply rooted in Flink runtime. We could extract it out to
>> >>>>>>>>>>>> flink-metrics in order to use it for generic purpose. There
>> will
>> >>>> be
>> >>>>>>>>>>>> some work, though.
>> >>>>>>>>>>>>
>> >>>>>>>>>>>> Another approach is to make |AbstractMetrics| in this patch
>> as
>> >> the
>> >>>>>>>>>>>> metric entry point. It wraps metric group and provides the
>> >> missing
>> >>>>>>>>>>>> functionalities. Then we can roll out this pattern to runtime
>> >>>>>>>>>>>> components gradually as well.
>> >>>>>>>>>>>>
>> >>>>>>>>>>>> My first thought is that the latter approach gives a more
>> smooth
>> >>>>>>>>>>>> migration. But I am also OK with doing a refactoring on the
>> >>>>>>>>>>>> |AbstractMetricGroup| family.
>> >>>>>>>>>>>>
>> >>>>>>>>>>>>
>> >>>>>>>>>>>> Thanks,
>> >>>>>>>>>>>>
>> >>>>>>>>>>>> Jiangjie (Becket) Qin
>> >>>>>>>>>>>>
>> >>>>>>>>>>>> [1] https://github.com/becketqin/flink/pull/1
>> >>>>>>>>>>>>
>> >>>>>>>>>>>> On Mon, Feb 25, 2019 at 2:32 PM Becket Qin <
>> >> becket.qin@gmail.com
>> >>>>>>>>>>>> <ma...@gmail.com>> wrote:
>> >>>>>>>>>>>>
>> >>>>>>>>>>>> Hi Chesnay,
>> >>>>>>>>>>>>
>> >>>>>>>>>>>> It might be easier to discuss some implementation details in
>> >> the
>> >>>>>>>>>>>> PR review instead of in the FLIP discussion thread. I have a
>> >>>>>>>>> patch
>> >>>>>>>>>>>> for Kafka connectors ready but haven't submitted the PR yet.
>> >>>>>>>>>>>> Hopefully that will help explain a bit more.
>> >>>>>>>>>>>>
>> >>>>>>>>>>>> ** Re: metric type binding
>> >>>>>>>>>>>> This is a valid point that worths discussing. If I understand
>> >>>>>>>>>>>> correctly, there are two points:
>> >>>>>>>>>>>>
>> >>>>>>>>>>>> 1. Metric type / interface does not matter as long as the
>> >> metric
>> >>>>>>>>>>>> semantic is clearly defined.
>> >>>>>>>>>>>> Conceptually speaking, I agree that as long as the metric
>> >>>>>>>>> semantic
>> >>>>>>>>>>>> is defined, metric type does not matter. To some extent,
>> Gauge
>> >> /
>> >>>>>>>>>>>> Counter / Meter / Histogram themselves can be think of as
>> some
>> >>>>>>>>>>>> well-recognized semantics, if you wish. In Flink, these
>> metric
>> >>>>>>>>>>>> semantics have their associated interface classes. In
>> practice,
>> >>>>>>>>>>>> such semantic to interface binding seems necessary for
>> >> different
>> >>>>>>>>>>>> components to communicate. Simply standardize the semantic
>> of
>> >>>>>>>>> the
>> >>>>>>>>>>>> connector metrics seems not sufficient for people to build
>> >>>>>>>>>>>> ecosystem on top of. At the end of the day, we still need to
>> >>>> have
>> >>>>>>>>>>>> some embodiment of the metric semantics that people can
>> program
>> >>>>>>>>>>>> against.
>> >>>>>>>>>>>>
>> >>>>>>>>>>>> 2. Sometimes the same metric semantic can be exposed using
>> >>>>>>>>>>>> different metric types / interfaces.
>> >>>>>>>>>>>> This is a good point. Counter and Gauge-as-a-Counter are
>> pretty
>> >>>>>>>>>>>> much interchangeable. This is more of a trade-off between the
>> >>>>>>>>> user
>> >>>>>>>>>>>> experience of metric producers and consumers. The metric
>> >>>>>>>>> producers
>> >>>>>>>>>>>> want to use Counter or Gauge depending on whether the counter
>> >> is
>> >>>>>>>>>>>> already tracked in code, while ideally the metric consumers
>> >> only
>> >>>>>>>>>>>> want to see a single metric type for each metric. I am
>> leaning
>> >>>>>>>>>>>> towards to make the metric producers happy, i.e. allow Gauge
>> /
>> >>>>>>>>>>>> Counter metric type, and the the metric consumers handle the
>> >>>> type
>> >>>>>>>>>>>> variation. The reason is that in practice, there might be
>> more
>> >>>>>>>>>>>> connector implementations than metric reporter
>> implementations.
>> >>>>>>>>> We
>> >>>>>>>>>>>> could also provide some helper method to facilitate reading
>> >> from
>> >>>>>>>>>>>> such variable metric type.
>> >>>>>>>>>>>>
>> >>>>>>>>>>>>
>> >>>>>>>>>>>> Just some quick replies to the comments around implementation
>> >>>>>>>>>>> details.
>> >>>>>>>>>>>>
>> >>>>>>>>>>>> 4) single place where metrics are registered except
>> >>>>>>>>>>>> connector-specific
>> >>>>>>>>>>>> ones (which we can't really avoid).
>> >>>>>>>>>>>>
>> >>>>>>>>>>>> Register connector specific ones in a single place is
>> actually
>> >>>>>>>>>>>> something that I want to achieve.
>> >>>>>>>>>>>>
>> >>>>>>>>>>>> 2) I'm talking about time-series databases like
>> Prometheus.
>> >>>>>>>>> We
>> >>>>>>>>>>>> would
>> >>>>>>>>>>>> only have a gauge metric exposing the last
>> >>>> fetchTime/emitTime
>> >>>>>>>>>>>> that is
>> >>>>>>>>>>>> regularly reported to the backend (Prometheus), where a
>> >> user
>> >>>>>>>>>>>> could build
>> >>>>>>>>>>>> a histogram of his choosing when/if he wants it.
>> >>>>>>>>>>>>
>> >>>>>>>>>>>> Not sure if such downsampling works. As an example, if a user
>> >>>>>>>>>>>> complains that there are some intermittent latency spikes
>> >> (maybe
>> >>>>>>>>> a
>> >>>>>>>>>>>> few records in 10 seconds) in their processing system.
>> Having a
>> >>>>>>>>>>>> Gauge sampling instantaneous latency seems unlikely useful.
>> >>>>>>>>>>>> However by looking at actual 99.9 percentile latency might
>> >> help.
>> >>>>>>>>>>>>
>> >>>>>>>>>>>> Thanks,
>> >>>>>>>>>>>>
>> >>>>>>>>>>>> Jiangjie (Becket) Qin
>> >>>>>>>>>>>>
>> >>>>>>>>>>>>
>> >>>>>>>>>>>> On Fri, Feb 22, 2019 at 9:30 PM Chesnay Schepler
>> >>>>>>>>>>>> <chesnay@apache.org <ma...@apache.org>> wrote:
>> >>>>>>>>>>>>
>> >>>>>>>>>>>> Re: over complication of implementation.
>> >>>>>>>>>>>>
>> >>>>>>>>>>>> I think I get understand better know what you're shooting
>> >>>>>>>>> for,
>> >>>>>>>>>>>> effectively something like the OperatorIOMetricGroup.
>> >>>>>>>>>>>> But still, re-define setupConnectorMetrics() to accept a
>> >> set
>> >>>>>>>>>>>> of flags
>> >>>>>>>>>>>> for counters/meters(ans _possibly_ histograms) along
>> with a
>> >>>>>>>>>>>> set of
>> >>>>>>>>>>>> well-defined Optional<Gauge<?>>, and return the group.
>> >>>>>>>>>>>>
>> >>>>>>>>>>>> Solves all issues as far as i can tell:
>> >>>>>>>>>>>> 1) no metrics must be created manually (except Gauges,
>> >> which
>> >>>>>>>>>> are
>> >>>>>>>>>>>> effectively just Suppliers and you can't get around
>> this),
>> >>>>>>>>>>>> 2) additional metrics can be registered on the returned
>> >>>>>>>>> group,
>> >>>>>>>>>>>> 3) see 1),
>> >>>>>>>>>>>> 4) single place where metrics are registered except
>> >>>>>>>>>>>> connector-specific
>> >>>>>>>>>>>> ones (which we can't really avoid).
>> >>>>>>>>>>>>
>> >>>>>>>>>>>> Re: Histogram
>> >>>>>>>>>>>>
>> >>>>>>>>>>>> 1) As an example, whether "numRecordsIn" is exposed as a
>> >>>>>>>>>>>> Counter or a
>> >>>>>>>>>>>> Gauge should be irrelevant. So far we're using the metric
>> >>>>>>>>> type
>> >>>>>>>>>>>> that is
>> >>>>>>>>>>>> the most convenient at exposing a given value. If there
>> is
>> >>>>>>>>>>>> some backing
>> >>>>>>>>>>>> data-structure that we want to expose some data from we
>> >>>>>>>>>>>> typically opt
>> >>>>>>>>>>>> for a Gauge, as otherwise we're just mucking around with
>> >> the
>> >>>>>>>>>>>> Meter/Counter API to get it to match. Similarly, if we
>> want
>> >>>>>>>>> to
>> >>>>>>>>>>>> count
>> >>>>>>>>>>>> something but no current count exists we typically added
>> a
>> >>>>>>>>>>>> Counter.
>> >>>>>>>>>>>> That's why attaching semantics to metric types makes
>> little
>> >>>>>>>>>>>> sense (but
>> >>>>>>>>>>>> unfortunately several reporters already do it); for
>> >>>>>>>>>>>> counters/meters
>> >>>>>>>>>>>> certainly, but the majority of metrics are gauges.
>> >>>>>>>>>>>>
>> >>>>>>>>>>>> 2) I'm talking about time-series databases like
>> Prometheus.
>> >>>>>>>>> We
>> >>>>>>>>>>>> would
>> >>>>>>>>>>>> only have a gauge metric exposing the last
>> >>>> fetchTime/emitTime
>> >>>>>>>>>>>> that is
>> >>>>>>>>>>>> regularly reported to the backend (Prometheus), where a
>> >> user
>> >>>>>>>>>>>> could build
>> >>>>>>>>>>>> a histogram of his choosing when/if he wants it.
>> >>>>>>>>>>>>
>> >>>>>>>>>>>> On 22.02.2019 13:57, Becket Qin wrote:
>> >>>>>>>>>>>>> Hi Chesnay,
>> >>>>>>>>>>>>>
>> >>>>>>>>>>>>> Thanks for the explanation.
>> >>>>>>>>>>>>>
>> >>>>>>>>>>>>> ** Re: FLIP
>> >>>>>>>>>>>>> I might have misunderstood this, but it seems that "major
>> >>>>>>>>>>>> changes" are well
>> >>>>>>>>>>>>> defined in FLIP. The full contents is following:
>> >>>>>>>>>>>>> What is considered a "major change" that needs a FLIP?
>> >>>>>>>>>>>>>
>> >>>>>>>>>>>>> Any of the following should be considered a major change:
>> >>>>>>>>>>>>>
>> >>>>>>>>>>>>> - Any major new feature, subsystem, or piece of
>> >>>>>>>>>>>> functionality
>> >>>>>>>>>>>>> - *Any change that impacts the public interfaces of the
>> >>>>>>>>>>>> project*
>> >>>>>>>>>>>>>
>> >>>>>>>>>>>>> What are the "public interfaces" of the project?
>> >>>>>>>>>>>>>
>> >>>>>>>>>>>>>
>> >>>>>>>>>>>>>
>> >>>>>>>>>>>>> *All of the following are public interfaces *that people
>> >>>>>>>>>>>> build around:
>> >>>>>>>>>>>>>
>> >>>>>>>>>>>>> - DataStream and DataSet API, including classes related
>> >>>>>>>>>>>> to that, such as
>> >>>>>>>>>>>>> StreamExecutionEnvironment
>> >>>>>>>>>>>>>
>> >>>>>>>>>>>>>
>> >>>>>>>>>>>>> - Classes marked with the @Public annotation
>> >>>>>>>>>>>>>
>> >>>>>>>>>>>>>
>> >>>>>>>>>>>>> - On-disk binary formats, such as
>> >>>>>>>>> checkpoints/savepoints
>> >>>>>>>>>>>>>
>> >>>>>>>>>>>>>
>> >>>>>>>>>>>>> - User-facing scripts/command-line tools, i.e.
>> >>>>>>>>>>>> bin/flink, Yarn scripts,
>> >>>>>>>>>>>>> Mesos scripts
>> >>>>>>>>>>>>>
>> >>>>>>>>>>>>>
>> >>>>>>>>>>>>> - Configuration settings
>> >>>>>>>>>>>>>
>> >>>>>>>>>>>>>
>> >>>>>>>>>>>>> - *Exposed monitoring information*
>> >>>>>>>>>>>>>
>> >>>>>>>>>>>>>
>> >>>>>>>>>>>>> So any monitoring information change is considered as
>> >>>>>>>>> public
>> >>>>>>>>>>>> interface, and
>> >>>>>>>>>>>>> any public interface change is considered as a "major
>> >>>>>>>>>> change".
>> >>>>>>>>>>>>>
>> >>>>>>>>>>>>>
>> >>>>>>>>>>>>> ** Re: over complication of implementation.
>> >>>>>>>>>>>>>
>> >>>>>>>>>>>>> Although this is more of implementation details that is not
>> >>>>>>>>>>>> covered by the
>> >>>>>>>>>>>>> FLIP. But it may be worth discussing.
>> >>>>>>>>>>>>>
>> >>>>>>>>>>>>> First of all, I completely agree that we should use the
>> >>>>>>>>>>>> simplest way to
>> >>>>>>>>>>>>> achieve our goal. To me the goal is the following:
>> >>>>>>>>>>>>> 1. Clear connector conventions and interfaces.
>> >>>>>>>>>>>>> 2. The easiness of creating a connector.
>> >>>>>>>>>>>>>
>> >>>>>>>>>>>>> Both of them are important to the prosperity of the
>> >>>>>>>>>>>> connector ecosystem. So
>> >>>>>>>>>>>>> I'd rather abstract as much as possible on our side to make
>> >>>>>>>>>>>> the connector
>> >>>>>>>>>>>>> developer's work lighter. Given this goal, a static util
>> >>>>>>>>>>>> method approach
>> >>>>>>>>>>>>> might have a few drawbacks:
>> >>>>>>>>>>>>> 1. Users still have to construct the metrics by themselves.
>> >>>>>>>>>>>> (And note that
>> >>>>>>>>>>>>> this might be erroneous by itself. For example, a customer
>> >>>>>>>>>>>> wrapper around
>> >>>>>>>>>>>>> dropwizard meter maybe used instead of MeterView).
>> >>>>>>>>>>>>> 2. When connector specific metrics are added, it is
>> >>>>>>>>>>>> difficult to enforce
>> >>>>>>>>>>>>> the scope to be the same as standard metrics.
>> >>>>>>>>>>>>> 3. It seems that a method proliferation is inevitable if we
>> >>>>>>>>>>>> want to apply
>> >>>>>>>>>>>>> sanity checks. e.g. The metric of numBytesIn was not
>> >>>>>>>>>>>> registered for a meter.
>> >>>>>>>>>>>>> 4. Metrics are still defined in random places and hard to
>> >>>>>>>>>>> track.
>> >>>>>>>>>>>>>
>> >>>>>>>>>>>>> The current PR I had was inspired by the Config system in
>> >>>>>>>>>>>> Kafka, which I
>> >>>>>>>>>>>>> found pretty handy. In fact it is not only used by Kafka
>> >>>>>>>>>>>> itself but even
>> >>>>>>>>>>>>> some other projects that depend on Kafka. I am not saying
>> >>>>>>>>>>>> this approach is
>> >>>>>>>>>>>>> perfect. But I think it worths to save the work for
>> >>>>>>>>>>>> connector writers and
>> >>>>>>>>>>>>> encourage more systematic implementation. That being said,
>> >>>>>>>>> I
>> >>>>>>>>>>>> am fully open
>> >>>>>>>>>>>>> to suggestions.
>> >>>>>>>>>>>>>
>> >>>>>>>>>>>>>
>> >>>>>>>>>>>>> Re: Histogram
>> >>>>>>>>>>>>> I think there are two orthogonal questions around those
>> >>>>>>>>>>> metrics:
>> >>>>>>>>>>>>>
>> >>>>>>>>>>>>> 1. Regardless of the metric type, by just looking at the
>> >>>>>>>>>>>> meaning of a
>> >>>>>>>>>>>>> metric, is generic to all connectors? If the answer is yes,
>> >>>>>>>>>>>> we should
>> >>>>>>>>>>>>> include the metric into the convention. No matter whether
>> >>>>>>>>> we
>> >>>>>>>>>>>> include it
>> >>>>>>>>>>>>> into the convention or not, some connector implementations
>> >>>>>>>>>>>> will emit such
>> >>>>>>>>>>>>> metric. It is better to have a convention than letting each
>> >>>>>>>>>>>> connector do
>> >>>>>>>>>>>>> random things.
>> >>>>>>>>>>>>>
>> >>>>>>>>>>>>> 2. If a standard metric is a histogram, what should we do?
>> >>>>>>>>>>>>> I agree that we should make it clear that using histograms
>> >>>>>>>>>>>> will have
>> >>>>>>>>>>>>> performance risk. But I do see histogram is useful in some
>> >>>>>>>>>>>> fine-granularity
>> >>>>>>>>>>>>> debugging where one do not have the luxury to stop the
>> >>>>>>>>>>>> system and inject
>> >>>>>>>>>>>>> more inspection code. So the workaround I am thinking is to
>> >>>>>>>>>>>> provide some
>> >>>>>>>>>>>>> implementation suggestions. Assume later on we have a
>> >>>>>>>>>>>> mechanism of
>> >>>>>>>>>>>>> selective metrics. In the abstract metrics class we can
>> >>>>>>>>>>>> disable those
>> >>>>>>>>>>>>> metrics by default individual connector writers does not
>> >>>>>>>>>>>> have to do
>> >>>>>>>>>>>>> anything (this is another advantage of having an
>> >>>>>>>>>>>> AbstractMetrics instead of
>> >>>>>>>>>>>>> static util methods.)
>> >>>>>>>>>>>>>
>> >>>>>>>>>>>>> I am not sure I fully understand the histogram in the
>> >>>>>>>>>>>> backend approach. Can
>> >>>>>>>>>>>>> you explain a bit more? Do you mean emitting the raw data,
>> >>>>>>>>>>>> e.g. fetchTime
>> >>>>>>>>>>>>> and emitTime with each record and let the histogram
>> >>>>>>>>>>>> computation happen in
>> >>>>>>>>>>>>> the background? Or let the processing thread putting the
>> >>>>>>>>>>>> values into a
>> >>>>>>>>>>>>> queue and have a separate thread polling from the queue and
>> >>>>>>>>>>>> add them into
>> >>>>>>>>>>>>> the histogram?
>> >>>>>>>>>>>>>
>> >>>>>>>>>>>>> Thanks,
>> >>>>>>>>>>>>>
>> >>>>>>>>>>>>> Jiangjie (Becket) Qin
>> >>>>>>>>>>>>>
>> >>>>>>>>>>>>>
>> >>>>>>>>>>>>>
>> >>>>>>>>>>>>>
>> >>>>>>>>>>>>>
>> >>>>>>>>>>>>> On Fri, Feb 22, 2019 at 4:34 PM Chesnay Schepler
>> >>>>>>>>>>>> <chesnay@apache.org <ma...@apache.org>> wrote:
>> >>>>>>>>>>>>>
>> >>>>>>>>>>>>>> Re: Flip
>> >>>>>>>>>>>>>> The very first line under both the main header and Purpose
>> >>>>>>>>>>>> section
>> >>>>>>>>>>>>>> describe Flips as "major changes", which this isn't.
>> >>>>>>>>>>>>>>
>> >>>>>>>>>>>>>> Re: complication
>> >>>>>>>>>>>>>> I'm not arguing against standardization, but again an
>> >>>>>>>>>>>> over-complicated
>> >>>>>>>>>>>>>> implementation when a static utility method would be
>> >>>>>>>>>>>> sufficient.
>> >>>>>>>>>>>>>>
>> >>>>>>>>>>>>>> public static void setupConnectorMetrics(
>> >>>>>>>>>>>>>> MetricGroup operatorMetricGroup,
>> >>>>>>>>>>>>>> String connectorName,
>> >>>>>>>>>>>>>> Optional<Gauge<Long>> numRecordsIn,
>> >>>>>>>>>>>>>> ...)
>> >>>>>>>>>>>>>>
>> >>>>>>>>>>>>>> This gives you all you need:
>> >>>>>>>>>>>>>> * a well-defined set of metrics for a connector to opt-in
>> >>>>>>>>>>>>>> * standardized naming schemes for scope and individual
>> >>>>>>>>>> metrics
>> >>>>>>>>>>>>>> * standardize metric types (although personally I'm not
>> >>>>>>>>>>>> interested in that
>> >>>>>>>>>>>>>> since metric types should be considered syntactic sugar)
>> >>>>>>>>>>>>>>
>> >>>>>>>>>>>>>> Re: Configurable Histogram
>> >>>>>>>>>>>>>> If anything they _must_ be turned off by default, but the
>> >>>>>>>>>>>> metric system is
>> >>>>>>>>>>>>>> already exposing so many options that I'm not too keen on
>> >>>>>>>>>>>> adding even more.
>> >>>>>>>>>>>>>> You have also only addressed my first argument against
>> >>>>>>>>>>>> histograms
>> >>>>>>>>>>>>>> (performance), the second one still stands (calculate
>> >>>>>>>>>>>> histogram in metric
>> >>>>>>>>>>>>>> backends instead).
>> >>>>>>>>>>>>>>
>> >>>>>>>>>>>>>> On 21.02.2019 16:27, Becket Qin wrote:
>> >>>>>>>>>>>>>>> Hi Chesnay,
>> >>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>> Thanks for the comments. I think this is worthy of a FLIP
>> >>>>>>>>>>>> because it is
>> >>>>>>>>>>>>>>> public API. According to the FLIP description a FlIP is
>> >>>>>>>>>>>> required in case
>> >>>>>>>>>>>>>> of:
>> >>>>>>>>>>>>>>> - Any change that impacts the public interfaces of
>> >>>>>>>>>>>> the project
>> >>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>> and the following entry is found in the definition of
>> >>>>>>>>>>>> "public interface".
>> >>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>> - Exposed monitoring information
>> >>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>> Metrics are critical to any production system. So a clear
>> >>>>>>>>>>>> metric
>> >>>>>>>>>>>>>> definition
>> >>>>>>>>>>>>>>> is important for any serious users. For an organization
>> >>>>>>>>>>>> with large Flink
>> >>>>>>>>>>>>>>> installation, change in metrics means great amount of
>> >>>>>>>>>>>> work. So such
>> >>>>>>>>>>>>>> changes
>> >>>>>>>>>>>>>>> do need to be fully discussed and documented.
>> >>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>> ** Re: Histogram.
>> >>>>>>>>>>>>>>> We can discuss whether there is a better way to expose
>> >>>>>>>>>>>> metrics that are
>> >>>>>>>>>>>>>>> suitable for histograms. My micro-benchmark on various
>> >>>>>>>>>>>> histogram
>> >>>>>>>>>>>>>>> implementations also indicates that they are
>> >>>>>>>>> significantly
>> >>>>>>>>>>>> slower than
>> >>>>>>>>>>>>>>> other metric types. But I don't think that means never
>> >>>>>>>>> use
>> >>>>>>>>>>>> histogram, but
>> >>>>>>>>>>>>>>> means use it with caution. For example, we can suggest
>> >>>>>>>>> the
>> >>>>>>>>>>>>>> implementations
>> >>>>>>>>>>>>>>> to turn them off by default and only turn it on for a
>> >>>>>>>>>>>> small amount of
>> >>>>>>>>>>>>>> time
>> >>>>>>>>>>>>>>> when performing some micro-debugging.
>> >>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>> ** Re: complication:
>> >>>>>>>>>>>>>>> Connector conventions are essential for Flink ecosystem.
>> >>>>>>>>>>>> Flink connectors
>> >>>>>>>>>>>>>>> pool is probably the most important part of Flink, just
>> >>>>>>>>>>>> like any other
>> >>>>>>>>>>>>>> data
>> >>>>>>>>>>>>>>> system. Clear conventions of connectors will help build
>> >>>>>>>>>>>> Flink ecosystem
>> >>>>>>>>>>>>>> in
>> >>>>>>>>>>>>>>> a more organic way.
>> >>>>>>>>>>>>>>> Take the metrics convention as an example, imagine
>> >>>>>>>>> someone
>> >>>>>>>>>>>> has developed
>> >>>>>>>>>>>>>> a
>> >>>>>>>>>>>>>>> Flink connector for System foo, and another developer may
>> >>>>>>>>>>>> have developed
>> >>>>>>>>>>>>>> a
>> >>>>>>>>>>>>>>> monitoring and diagnostic framework for Flink which
>> >>>>>>>>>>>> analyzes the Flink
>> >>>>>>>>>>>>>> job
>> >>>>>>>>>>>>>>> performance based on metrics. With a clear metric
>> >>>>>>>>>>>> convention, those two
>> >>>>>>>>>>>>>>> projects could be developed independently. Once users put
>> >>>>>>>>>>>> them together,
>> >>>>>>>>>>>>>>> it would work without additional modifications. This
>> >>>>>>>>>>>> cannot be easily
>> >>>>>>>>>>>>>>> achieved by just defining a few constants.
>> >>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>> ** Re: selective metrics:
>> >>>>>>>>>>>>>>> Sure, we can discuss that in a separate thread.
>> >>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>> @Dawid
>> >>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>> ** Re: latency / fetchedLatency
>> >>>>>>>>>>>>>>> The primary purpose of establish such a convention is to
>> >>>>>>>>>>>> help developers
>> >>>>>>>>>>>>>>> write connectors in a more compatible way. The convention
>> >>>>>>>>>>>> is supposed to
>> >>>>>>>>>>>>>> be
>> >>>>>>>>>>>>>>> defined more proactively. So when look at the convention,
>> >>>>>>>>>>>> it seems more
>> >>>>>>>>>>>>>>> important to see if the concept is applicable to
>> >>>>>>>>>>>> connectors in general.
>> >>>>>>>>>>>>>> It
>> >>>>>>>>>>>>>>> might be true so far only Kafka connector reports
>> >>>>>>>>> latency.
>> >>>>>>>>>>>> But there
>> >>>>>>>>>>>>>> might
>> >>>>>>>>>>>>>>> be hundreds of other connector implementations in the
>> >>>>>>>>>>>> Flink ecosystem,
>> >>>>>>>>>>>>>>> though not in the Flink repo, and some of them also emits
>> >>>>>>>>>>>> latency. I
>> >>>>>>>>>>>>>> think
>> >>>>>>>>>>>>>>> a lot of other sources actually also has an append
>> >>>>>>>>>>>> timestamp. e.g.
>> >>>>>>>>>>>>>> database
>> >>>>>>>>>>>>>>> bin logs and some K-V stores. So I wouldn't be surprised
>> >>>>>>>>>>>> if some database
>> >>>>>>>>>>>>>>> connector can also emit latency metrics.
>> >>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>> Thanks,
>> >>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>> Jiangjie (Becket) Qin
>> >>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>> On Thu, Feb 21, 2019 at 10:14 PM Chesnay Schepler
>> >>>>>>>>>>>> <chesnay@apache.org <ma...@apache.org>>
>> >>>>>>>>>>>>>>> wrote:
>> >>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>> Regarding 2) It doesn't make sense to investigate this
>> >>>>>>>>> as
>> >>>>>>>>>>>> part of this
>> >>>>>>>>>>>>>>>> FLIP. This is something that could be of interest for
>> >>>>>>>>> the
>> >>>>>>>>>>>> entire metric
>> >>>>>>>>>>>>>>>> system, and should be designed for as such.
>> >>>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>> Regarding the proposal as a whole:
>> >>>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>> Histogram metrics shall not be added to the core of
>> >>>>>>>>>>>> Flink. They are
>> >>>>>>>>>>>>>>>> significantly more expensive than other metrics, and
>> >>>>>>>>>>>> calculating
>> >>>>>>>>>>>>>>>> histograms in the application is regarded as an
>> >>>>>>>>>>>> anti-pattern by several
>> >>>>>>>>>>>>>>>> metric backends, who instead recommend to expose the raw
>> >>>>>>>>>>>> data and
>> >>>>>>>>>>>>>>>> calculate the histogram in the backend.
>> >>>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>> Second, this seems overly complicated. Given that we
>> >>>>>>>>>>>> already established
>> >>>>>>>>>>>>>>>> that not all connectors will export all metrics we are
>> >>>>>>>>>>>> effectively
>> >>>>>>>>>>>>>>>> reducing this down to a consistent naming scheme. We
>> >>>>>>>>>>>> don't need anything
>> >>>>>>>>>>>>>>>> sophisticated for that; basically just a few constants
>> >>>>>>>>>>>> that all
>> >>>>>>>>>>>>>>>> connectors use.
>> >>>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>> I'm not convinced that this is worthy of a FLIP.
>> >>>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>> On 21.02.2019 14:26, Dawid Wysakowicz wrote:
>> >>>>>>>>>>>>>>>>> Hi,
>> >>>>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>>> Ad 1. In general I undestand and I agree. But those
>> >>>>>>>>>>>> particular metrics
>> >>>>>>>>>>>>>>>>> (latency, fetchLatency), right now would only be
>> >>>>>>>>>>>> reported if user uses
>> >>>>>>>>>>>>>>>>> KafkaConsumer with internal timestampAssigner with
>> >>>>>>>>>>>> StreamCharacteristic
>> >>>>>>>>>>>>>>>>> set to EventTime, right? That sounds like a very
>> >>>>>>>>>>>> specific case. I am
>> >>>>>>>>>>>>>> not
>> >>>>>>>>>>>>>>>>> sure if we should introduce a generic metric that will
>> >>>>>>>>> be
>> >>>>>>>>>>>>>>>>> disabled/absent for most of implementations.
>> >>>>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>>> Ad.2 That sounds like an orthogonal issue, that might
>> >>>>>>>>>>>> make sense to
>> >>>>>>>>>>>>>>>>> investigate in the future.
>> >>>>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>>> Best,
>> >>>>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>>> Dawid
>> >>>>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>>> On 21/02/2019 13:20, Becket Qin wrote:
>> >>>>>>>>>>>>>>>>>> Hi Dawid,
>> >>>>>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>>>> Thanks for the feedback. That makes sense to me. There
>> >>>>>>>>>>>> are two cases
>> >>>>>>>>>>>>>> to
>> >>>>>>>>>>>>>>>> be
>> >>>>>>>>>>>>>>>>>> addressed.
>> >>>>>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>>>> 1. The metrics are supposed to be a guidance. It is
>> >>>>>>>>>>>> likely that a
>> >>>>>>>>>>>>>>>> connector
>> >>>>>>>>>>>>>>>>>> only supports some but not all of the metrics. In that
>> >>>>>>>>>>>> case, each
>> >>>>>>>>>>>>>>>> connector
>> >>>>>>>>>>>>>>>>>> implementation should have the freedom to decide which
>> >>>>>>>>>>>> metrics are
>> >>>>>>>>>>>>>>>>>> reported. For the metrics that are supported, the
>> >>>>>>>>>>>> guidance should be
>> >>>>>>>>>>>>>>>>>> followed.
>> >>>>>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>>>> 2. Sometimes users may want to disable certain metrics
>> >>>>>>>>>>>> for some reason
>> >>>>>>>>>>>>>>>>>> (e.g. performance / reprocessing of data). A generic
>> >>>>>>>>>>>> mechanism should
>> >>>>>>>>>>>>>> be
>> >>>>>>>>>>>>>>>>>> provided to allow user choose which metrics are
>> >>>>>>>>>>>> reported. This
>> >>>>>>>>>>>>>> mechanism
>> >>>>>>>>>>>>>>>>>> should also be honored by the connector
>> >>>>>>>>> implementations.
>> >>>>>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>>>> Does this sound reasonable to you?
>> >>>>>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>>>> Thanks,
>> >>>>>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>>>> Jiangjie (Becket) Qin
>> >>>>>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>>>> On Thu, Feb 21, 2019 at 4:22 PM Dawid Wysakowicz <
>> >>>>>>>>>>>>>>>> dwysakowicz@apache.org <ma...@apache.org>>
>> >>>>>>>>>>>>>>>>>> wrote:
>> >>>>>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>>>>> Hi,
>> >>>>>>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>>>>> Generally I like the idea of having a unified,
>> >>>>>>>>>>>> standard set of
>> >>>>>>>>>>>>>> metrics
>> >>>>>>>>>>>>>>>> for
>> >>>>>>>>>>>>>>>>>>> all connectors. I have some slight concerns about
>> >>>>>>>>>>>> fetchLatency and
>> >>>>>>>>>>>>>>>>>>> latency though. They are computed based on EventTime
>> >>>>>>>>>>>> which is not a
>> >>>>>>>>>>>>>>>> purely
>> >>>>>>>>>>>>>>>>>>> technical feature. It depends often on some business
>> >>>>>>>>>>>> logic, might be
>> >>>>>>>>>>>>>>>> absent
>> >>>>>>>>>>>>>>>>>>> or defined after source. Those metrics could also
>> >>>>>>>>>>>> behave in a weird
>> >>>>>>>>>>>>>>>> way in
>> >>>>>>>>>>>>>>>>>>> case of replaying backlog. Therefore I am not sure if
>> >>>>>>>>>>>> we should
>> >>>>>>>>>>>>>> include
>> >>>>>>>>>>>>>>>>>>> those metrics by default. Maybe we could at least
>> >>>>>>>>>>>> introduce a feature
>> >>>>>>>>>>>>>>>>>>> switch for them? What do you think?
>> >>>>>>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>>>>> Best,
>> >>>>>>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>>>>> Dawid
>> >>>>>>>>>>>>>>>>>>> On 21/02/2019 03:13, Becket Qin wrote:
>> >>>>>>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>>>>> Bump. If there is no objections to the proposed
>> >>>>>>>>>>>> metrics. I'll start a
>> >>>>>>>>>>>>>>>>>>> voting thread later toady.
>> >>>>>>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>>>>> Thanks,
>> >>>>>>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>>>>> Jiangjie (Becket) Qin
>> >>>>>>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>>>>> On Mon, Feb 11, 2019 at 8:17 PM Becket Qin
>> >>>>>>>>>>>> <becket.qin@gmail.com <ma...@gmail.com>> <
>> >>>>>>>>>>>>>>>> becket.qin@gmail.com <ma...@gmail.com>>
>> >>>>>>>>>> wrote:
>> >>>>>>>>>>>>>>>>>>> Hi folks,
>> >>>>>>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>>>>> I would like to start the FLIP discussion thread
>> >>>>>>>>> about
>> >>>>>>>>>>>> standardize
>> >>>>>>>>>>>>>> the
>> >>>>>>>>>>>>>>>>>>> connector metrics.
>> >>>>>>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>>>>> In short, we would like to provide a convention of
>> >>>>>>>>>>>> Flink connector
>> >>>>>>>>>>>>>>>>>>> metrics. It will help simplify the monitoring and
>> >>>>>>>>>>>> alerting on Flink
>> >>>>>>>>>>>>>>>> jobs.
>> >>>>>>>>>>>>>>>>>>> The FLIP link is following:
>> >>>>>>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>
>> >>>>>>>>>>>>
>> >>>>>>>>>>>
>> >>>>>>>>>>
>> >>>>>>>>>
>> >>>>>>>
>> >>>>
>> >>
>> https://cwiki.apache.org/confluence/display/FLINK/FLIP-33%3A+Standardize+Connector+Metrics
>> >>>>>>>>>>>>>>>>>>> Thanks,
>> >>>>>>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>>>>> Jiangjie (Becket) Qin
>> >>>>>>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>
>> >>>>>>>>>>>>
>> >>>>>>>>>>>
>> >>>>>>>>>>>
>> >>>>>>>>>>
>> >>>>>>>>>
>> >>>>>>>
>> >>>>>>>
>> >>>>
>> >>>>
>> >>>>
>> >>
>> >>
>> >>
>>
>>
Re: [DISCUSS] FLIP-33: Standardize connector metrics
Posted by Becket Qin <be...@gmail.com>.
Hi Piotr,
Thanks for the comments. Yes, you are right. Users will have to look at
other metrics to decide whether the pipeline is healthy or not in the first
place before they can use the time-based metric to fix the bottleneck.
I agree that once we have FLIP-27 ready, some of the metrics can just be
reported by the abstract implementation.
I've updated FLIP-33 wiki page to add the pendingBytes and pendingRecords
metric. Please let me know if you have any concern over the updated metric
convention proposal.
@Chesnay Schepler <ch...@apache.org> @Stephan Ewen
<st...@ververica.com> will
you also have time to take a look at the proposed metric convention? If
there is no further concern I'll start a voting thread for this FLIP in two
days.
Thanks,
Jiangjie (Becket) Qin
On Wed, Jun 5, 2019 at 6:54 PM Piotr Nowojski <pi...@ververica.com> wrote:
> Hi Becket,
>
> Thanks for the answer :)
>
> > By time-based metric, I meant the portion of time spent on producing the
> > record to downstream. For example, a source connector can report that
> it's
> > spending 80% of time to emit record to downstream processing pipeline. In
> > another case, a sink connector may report that its spending 30% of time
> > producing the records to the external system.
> >
> > This is in some sense equivalent to the buffer usage metric:
>
> > - 80% of time spent on emitting records to downstream ---> downstream
> > node is bottleneck ---> output buffer is probably full.
> > - 30% of time spent on emitting records to downstream ---> downstream
> > node is not bottleneck ---> output buffer is probably not full.
>
> If by “time spent on emitting records to downstream” you understand
> “waiting on back pressure”, then I see your point. And I agree that some
> kind of ratio/time based metric gives you more information. However under
> “time spent on emitting records to downstream” might be hidden the
> following (extreme) situation:
>
> 1. Job is barely able to handle influx of records, there is 99%
> CPU/resource usage in the cluster, but nobody is
> bottlenecked/backpressured, all output buffers are empty, everybody is
> waiting in 1% of it’s time for more records to process.
> 2. 80% time can still be spent on "down stream operators”, because they
> are the CPU intensive operations, but this doesn’t mean that increasing the
> parallelism down the stream will help with anything there. To the contrary,
> increasing parallelism of the source operator might help to increase
> resource utilisation up to 100%.
>
> However, this “time based/ratio” approach can be extended to in/output
> buffer usage. Besides collecting an information that input/output buffer is
> full/empty, we can probe profile how often are buffer empty/full. If output
> buffer is full 1% of times, there is almost no back pressure. If it’s full
> 80% of times, there is some back pressure, if it’s full 99.9% of times,
> there is huge back pressure.
>
> Now for autoscaling you could compare the input & output buffers fill
> ratio:
>
> 1. Both are high, the source of bottleneck is down the stream
> 2. Output is low, input is high, this is the bottleneck and the higher the
> difference, the bigger source of bottleneck is this is operator/task
> 3. Output is high, input is low - there was some load spike that we are
> currently finishing to process
>
>
>
> But long story short, we are probably diverging from the topic of this
> discussion, and we can discuss this at some later point.
>
> For now, for sources:
>
> as I wrote before, +1 for:
> - pending.bytes, Gauge
> - pending.messages, Gauge
>
> When we will be developing/discussing SourceReader from FLIP-27 we might
> then add:
>
> - in-memory.buffer.usage (0 - 100%)
>
> Which will be estimated automatically by Flink while user will be able to
> override/provide better estimation.
>
> Piotrek
>
> > On 5 Jun 2019, at 05:42, Becket Qin <be...@gmail.com> wrote:
> >
> > Hi Piotr,
> >
> > Thanks for the explanation. Please see some clarifications below.
> >
> > By time-based metric, I meant the portion of time spent on producing the
> > record to downstream. For example, a source connector can report that
> it's
> > spending 80% of time to emit record to downstream processing pipeline. In
> > another case, a sink connector may report that its spending 30% of time
> > producing the records to the external system.
> >
> > This is in some sense equivalent to the buffer usage metric:
> > - 80% of time spent on emitting records to downstream ---> downstream
> > node is bottleneck ---> output buffer is probably full.
> > - 30% of time spent on emitting records to downstream ---> downstream
> > node is not bottleneck ---> output buffer is probably not full.
> >
> > However, the time-based metric has a few advantages that the buffer usage
> > metric may not have.
> >
> > 1. Buffer usage metric may not be applicable to all the connector
> > implementations, while reporting time-based metric are always doable.
> > Some source connectors may not have any input buffer, or they may use
> some
> > third party library that does not expose the input buffer at all.
> > Similarly, for sink connectors, the implementation may not have any
> output
> > buffer, or the third party library does not expose such buffer.
> >
> > 2. Although both type of metrics can detect bottleneck, time-based
> metrics
> > can be used to generate a more informed action to remove the bottleneck.
> > For example, when the downstream is bottleneck, the output buffer usage
> > metric is likely to be 100%, and the input buffer usage might be 0%. That
> > means we don't know what is the suitable parallelism to lift the
> > bottleneck. The time-based metric, on the other hand, would give useful
> > information, e.g. if 80% of time was spent on emitting records, we can
> > roughly increase the downstream node parallelism by 4 times.
> >
> > Admittedly, the time-based metrics are more expensive than buffer usage.
> So
> > we may have to do some sampling to reduce the cost. But in general, using
> > time-based metrics seems worth adding.
> >
> > That being said, I don't think buffer usage metric and time-based metrics
> > are mutually exclusive. We can probably have both. It is just that in
> > practice, features like auto-scaling might prefer time-based metrics for
> > the reason stated above.
> >
> >> 1. Define the metrics that would allow us to manually detect
> bottlenecks.
> > As I wrote, we already have them in most of the places, except of
> > sources/sinks.
> >> 2. Use those metrics, to automatically detect bottlenecks. Currently we
> > are only automatically detecting back pressure and reporting it to the
> user
> > in web UI (is it exposed as a metric at all?). Detecting the root cause
> of
> > the back pressure (bottleneck) is one step further.
> >> 3. Use the knowledge about where exactly the bottleneck is located, to
> > try to do something with it.
> >
> > As explained above, I think time-based metric also addresses item 1 and
> > item 2.
> >
> > Any thoughts？
> >
> > Thanks,
> >
> > Jiangjie (Becket) Qin
> >
> >
> >
> > On Mon, Jun 3, 2019 at 4:14 PM Piotr Nowojski <pi...@ververica.com>
> wrote:
> >
> >> Hi again :)
> >>
> >>> - pending.bytes, Gauge
> >>> - pending.messages, Gauge
> >>
> >>
> >> +1
> >>
> >> And true, instead of overloading one of the metric it is better when
> user
> >> can choose to provide only one of them.
> >>
> >> Re 2:
> >>
> >>> If I understand correctly, this metric along with the pending mesages /
> >>> bytes would answer the questions of:
> >>
> >>> - Does the connector consume fast enough? Lagging behind + empty buffer
> >> =
> >>> cannot consume fast enough.
> >>> - Does the connector emit fast enough? Lagging behind + full buffer =
> >>> cannot emit fast enough, i.e. the Flink pipeline is slow.
> >>
> >> Yes, exactly. This can also be used to support decisions like changing
> the
> >> parallelism of the sources and/or down stream operators.
> >>
> >> I’m not sure if I understand your proposal with time based measurements.
> >> Maybe I’m missing something, but I do not see how measuring time alone
> >> could answer the problem: where is the bottleneck. Time spent on the
> >> next/emit might be short or long (depending on how heavy to process the
> >> record is) and the source can still be bottlenecked/back pressured or
> not.
> >> Usually the easiest and the most reliable way how to detect bottlenecks
> is
> >> by checking usage of input & output buffers, since when input buffer is
> >> full while output buffer is empty, that’s the definition of a
> bottleneck.
> >> Also this is usually very easy and cheap to measure (it works
> effectively
> >> the same way as current’s Flink back pressure monitoring, but more
> cleanly,
> >> without probing thread’s stack traces).
> >>
> >> Also keep in mind that we are already using the buffer usage metrics for
> >> detecting the bottlenecks in Flink’s internal network exchanges (manual
> >> work). That’s the reason why I wanted to extend this to sources/sinks,
> >> since they are currently our blind spot.
> >>
> >>> One feature we are currently working on to scale Flink automatically
> >> relies
> >>> on some metrics answering the same question
> >>
> >> That would be very helpful feature. I think in order to achieve that we
> >> would need to:
> >> 1. Define the metrics that would allow us to manually detect
> bottlenecks.
> >> As I wrote, we already have them in most of the places, except of
> >> sources/sinks.
> >> 2. Use those metrics, to automatically detect bottlenecks. Currently we
> >> are only automatically detecting back pressure and reporting it to the
> user
> >> in web UI (is it exposed as a metric at all?). Detecting the root cause
> of
> >> the back pressure (bottleneck) is one step further.
> >> 3. Use the knowledge about where exactly the bottleneck is located, to
> try
> >> to do something with it.
> >>
> >> I think you are aiming for point 3., but before we reach it, we are
> still
> >> missing 1. & 2. Also even if we have 3., there is a value in 1 & 2 for
> >> manual analysis/dashboards.
> >>
> >> However, having the knowledge of where the bottleneck is, doesn’t
> >> necessarily mean that we know what we can do about it. For example
> >> increasing parallelism might or might not help with anything (data skew,
> >> bottleneck on some resource that does not scale), but this remark
> applies
> >> always, regardless of the way how did we detect the bottleneck.
> >>
> >> Piotrek
> >>
> >>> On 3 Jun 2019, at 06:16, Becket Qin <be...@gmail.com> wrote:
> >>>
> >>> Hi Piotr,
> >>>
> >>> Thanks for the suggestion. Some thoughts below:
> >>>
> >>> Re 1: The pending messages / bytes.
> >>> I completely agree these are very useful metrics and we should expect
> the
> >>> connector to report. WRT the way to expose them, it seems more
> consistent
> >>> to add two metrics instead of adding a method (unless there are other
> use
> >>> cases other than metric reporting). So we can add the following two
> >> metrics.
> >>> - pending.bytes, Gauge
> >>> - pending.messages, Gauge
> >>> Applicable connectors can choose to report them. These two metrics
> along
> >>> with latency should be sufficient for users to understand the progress
> >> of a
> >>> connector.
> >>>
> >>>
> >>> Re 2: Number of buffered data in-memory of the connector
> >>> If I understand correctly, this metric along with the pending mesages /
> >>> bytes would answer the questions of:
> >>> - Does the connector consume fast enough? Lagging behind + empty buffer
> >> =
> >>> cannot consume fast enough.
> >>> - Does the connector emit fast enough? Lagging behind + full buffer =
> >>> cannot emit fast enough, i.e. the Flink pipeline is slow.
> >>>
> >>> One feature we are currently working on to scale Flink automatically
> >> relies
> >>> on some metrics answering the same question, more specifically, we are
> >>> profiling the time spent on .next() method (time to consume) and the
> time
> >>> spent on .collect() method (time to emit / process). One advantage of
> >> such
> >>> method level time cost allows us to calculate the parallelism required
> to
> >>> keep up in case their is a lag.
> >>>
> >>> However, one concern I have regarding such metric is that they are
> >>> implementation specific. Either profiling on the method time, or
> >> reporting
> >>> buffer usage assumes the connector are implemented in such a way. A
> >>> slightly better solution might be have the following metric:
> >>>
> >>> - EmitTimeRatio (or FetchTimeRatio): The time spent on emitting
> >>> records / Total time elapsed.
> >>>
> >>> This assumes that the source connectors have to emit the records to the
> >>> downstream at some point. The emission may take some time ( e.g. go
> >> through
> >>> chained operators). And the rest of the time are spent to prepare the
> >>> record to emit, including time for consuming and format conversion,
> etc.
> >>> Ideally, we'd like to see the time spent on record fetch and emit to be
> >>> about the same, so no one is bottleneck for the other.
> >>>
> >>> The downside of these time based metrics is additional overhead to get
> >> the
> >>> time, therefore sampling might be needed. But in practice I feel such
> >> time
> >>> based metric might be more useful if we want to take action.
> >>>
> >>>
> >>> I think we should absolutely add metrics in (1) to the metric
> convention.
> >>> We could also add the metrics mentioned in (2) if we reach consensus on
> >>> that. What do you think?
> >>>
> >>> Thanks,
> >>>
> >>> Jiangjie (Becket) Qin
> >>>
> >>>
> >>> On Fri, May 31, 2019 at 4:26 PM Piotr Nowojski <pi...@ververica.com>
> >> wrote:
> >>>
> >>>> Hey Becket,
> >>>>
> >>>> Re 1a) and 1b) +1 from my side.
> >>>>
> >>>> I’ve discussed this issue:
> >>>>
> >>>>>>>
> >>>>>>> 2. It would be nice to have metrics, that allow us to check the
> cause
> >>>> of
> >>>>>>> back pressure:
> >>>>>>> a) for sources, length of input queue (in bytes? Or boolean
> >>>>>>> hasSomethingl/isEmpty)
> >>>>>>> b) for sinks, length of output queue (in bytes? Or boolean
> >>>>>>> hasSomething/isEmpty)
> >>>>
> >>>> With Nico at some lengths and he also saw the benefits of them. We
> also
> >>>> have more concrete proposal for that.
> >>>>
> >>>> Actually there are two really useful metrics, that we are missing
> >>>> currently:
> >>>>
> >>>> 1. Number of data/records/bytes in the backlog to process. For example
> >>>> remaining number of bytes in unread files. Or pending data in Kafka
> >> topics.
> >>>> 2. Number of buffered data in-memory of the connector, that are
> waiting
> >> to
> >>>> be processed pushed to Flink pipeline.
> >>>>
> >>>> Re 1:
> >>>> This would have to be a metric provided directly by a connector. It
> >> could
> >>>> be an undefined `int`:
> >>>>
> >>>> `int backlog` - estimate of pending work.
> >>>>
> >>>> “Undefined” meaning that it would be up to a connector to decided
> >> whether
> >>>> it’s measured in bytes, records, pending files or whatever it is
> >> possible
> >>>> to provide by the connector. This is because I assume not every
> >> connector
> >>>> can provide exact number and for some of them it might be impossible
> to
> >>>> provide records number of bytes count.
> >>>>
> >>>> Re 2:
> >>>> This metric could be either provided by a connector, or calculated
> >> crudely
> >>>> by Flink:
> >>>>
> >>>> `float bufferUsage` - value from [0.0, 1.0] range
> >>>>
> >>>> Percentage of used in memory buffers, like in Kafka’s handover.
> >>>>
> >>>> It could be crudely implemented by Flink with FLIP-27
> >>>> SourceReader#isAvailable. If SourceReader is not available reported
> >>>> `bufferUsage` could be 0.0. If it is available, it could be 1.0. I
> think
> >>>> this would be a good enough estimation for most of the use cases (that
> >>>> could be overloaded and implemented better if desired). Especially
> >> since we
> >>>> are reporting only probed values: if probed values are almost always
> >> “1.0”,
> >>>> it would mean that we have a back pressure. If they are almost always
> >>>> “0.0”, there is probably no back pressure at the sources.
> >>>>
> >>>> What do you think about this?
> >>>>
> >>>> Piotrek
> >>>>
> >>>>> On 30 May 2019, at 11:41, Becket Qin <be...@gmail.com> wrote:
> >>>>>
> >>>>> Hi all,
> >>>>>
> >>>>> Thanks a lot for all the feedback and comments. I'd like to continue
> >> the
> >>>>> discussion on this FLIP.
> >>>>>
> >>>>> I updated the FLIP-33 wiki to remove all the histogram metrics from
> the
> >>>>> first version of metric convention due to the performance concern.
> The
> >>>> plan
> >>>>> is to introduce them later when we have a mechanism to opt in/out
> >>>> metrics.
> >>>>> At that point, users can decide whether they want to pay the cost to
> >> get
> >>>>> the metric or not.
> >>>>>
> >>>>> As Stephan suggested, for this FLIP, let's first try to agree on the
> >>>> small
> >>>>> list of conventional metrics that connectors should follow.
> >>>>> Just to be clear, the purpose of the convention is not to enforce
> every
> >>>>> connector to report all these metrics, but to provide a guidance in
> >> case
> >>>>> these metrics are reported by some connectors.
> >>>>>
> >>>>>
> >>>>> @ Stephan & Chesnay,
> >>>>>
> >>>>> Regarding the duplication of `RecordsIn` metric in operator / task
> >>>>> IOMetricGroups, from what I understand, for source operator, it is
> >>>> actually
> >>>>> the SourceFunction that reports the operator level
> >>>>> RecordsIn/RecordsInPerSecond metric. So they are essentially the same
> >>>>> metric in the operator level IOMetricGroup. Similarly for the Sink
> >>>>> operator, the operator level RecordsOut/RecordsOutPerSecond metrics
> are
> >>>>> also reported by the Sink function. I marked them as existing in the
> >>>>> FLIP-33 wiki page. Please let me know if I misunderstood.
> >>>>>
> >>>>> Thanks,
> >>>>>
> >>>>> Jiangjie (Becket) Qin
> >>>>>
> >>>>>
> >>>>> On Thu, May 30, 2019 at 5:16 PM Becket Qin <be...@gmail.com>
> >> wrote:
> >>>>>
> >>>>>> Hi Piotr,
> >>>>>>
> >>>>>> Thanks a lot for the feedback.
> >>>>>>
> >>>>>> 1a) I guess you are referring to the part that "original system
> >> specific
> >>>>>> metrics should also be reported". The performance impact depends on
> >> the
> >>>>>> implementation. An efficient implementation would only record the
> >> metric
> >>>>>> once, but report them with two different metric names. This is
> >> unlikely
> >>>> to
> >>>>>> hurt performance.
> >>>>>>
> >>>>>> 1b) Yes, I agree that we should avoid adding overhead to the
> critical
> >>>> path
> >>>>>> by all means. This is sometimes a tradeoff, running blindly without
> >> any
> >>>>>> metric gives best performance, but sometimes might be frustrating
> when
> >>>> we
> >>>>>> debug some issues.
> >>>>>>
> >>>>>> 2. The metrics are indeed very useful. Are they supposed to be
> >> reported
> >>>> by
> >>>>>> the connectors or Flink itself? At this point FLIP-33 is more
> focused
> >> on
> >>>>>> provide a guidance to the connector authors on the metrics
> reporting.
> >>>> That
> >>>>>> said, after FLIP-27, I think we should absolutely report these
> metrics
> >>>> in
> >>>>>> the abstract implementation. In any case, the metric convention in
> >> this
> >>>>>> list are expected to evolve over time.
> >>>>>>
> >>>>>> Thanks,
> >>>>>>
> >>>>>> Jiangjie (Becket) Qin
> >>>>>>
> >>>>>> On Tue, May 28, 2019 at 6:24 PM Piotr Nowojski <piotr@ververica.com
> >
> >>>>>> wrote:
> >>>>>>
> >>>>>>> Hi,
> >>>>>>>
> >>>>>>> Thanks for the proposal and driving the effort here Becket :) I’ve
> >> read
> >>>>>>> through the FLIP-33 [1], and here are couple of my thoughts.
> >>>>>>>
> >>>>>>> Big +1 for standardising the metric names between connectors, it
> will
> >>>>>>> definitely help us and users a lot.
> >>>>>>>
> >>>>>>> Issues/questions/things to discuss that I’ve thought of:
> >>>>>>>
> >>>>>>> 1a. If we are about to duplicate some metrics, can this become a
> >>>>>>> performance issue?
> >>>>>>> 1b. Generally speaking, we should make sure that collecting those
> >>>> metrics
> >>>>>>> is as non intrusive as possible, especially that they will need to
> be
> >>>>>>> updated once per record. (They might be collected more rarely with
> >> some
> >>>>>>> overhead, but the hot path of updating it per record will need to
> be
> >> as
> >>>>>>> quick as possible). That includes both avoiding heavy computation
> on
> >>>> per
> >>>>>>> record path: histograms?, measuring time for time based metrics
> (per
> >>>>>>> second) (System.currentTimeMillis() depending on the implementation
> >> can
> >>>>>>> invoke a system call)
> >>>>>>>
> >>>>>>> 2. It would be nice to have metrics, that allow us to check the
> cause
> >>>> of
> >>>>>>> back pressure:
> >>>>>>> a) for sources, length of input queue (in bytes? Or boolean
> >>>>>>> hasSomethingl/isEmpty)
> >>>>>>> b) for sinks, length of output queue (in bytes? Or boolean
> >>>>>>> hasSomething/isEmpty)
> >>>>>>>
> >>>>>>> a) is useful in a scenario when we are processing backlog of
> records,
> >>>> all
> >>>>>>> of the internal Flink’s input/output network buffers are empty, and
> >> we
> >>>> want
> >>>>>>> to check whether the external source system is the bottleneck
> >> (source’s
> >>>>>>> input queue will be empty), or if the Flink’s connector is the
> >>>> bottleneck
> >>>>>>> (source’s input queues will be full).
> >>>>>>> b) similar story. Backlog of records, but this time all of the
> >> internal
> >>>>>>> Flink’s input/ouput network buffers are full, and we want o check
> >>>> whether
> >>>>>>> the external sink system is the bottleneck (sink output queues are
> >>>> full),
> >>>>>>> or if the Flink’s connector is the bottleneck (sink’s output queues
> >>>> will be
> >>>>>>> empty)
> >>>>>>>
> >>>>>>> It might be sometimes difficult to provide those metrics, so they
> >> could
> >>>>>>> be optional, but if we could provide them, it would be really
> >> helpful.
> >>>>>>>
> >>>>>>> Piotrek
> >>>>>>>
> >>>>>>> [1]
> >>>>>>>
> >>>>
> >>
> https://cwiki.apache.org/confluence/display/FLINK/FLIP-33:+Standardize+Connector+Metrics
> >>>>>>> <
> >>>>>>>
> >>>>
> >>
> https://cwiki.apache.org/confluence/display/FLINK/FLIP-33:+Standardize+Connector+Metrics
> >>>>>>>>
> >>>>>>>
> >>>>>>>> On 24 Apr 2019, at 13:28, Stephan Ewen <se...@apache.org> wrote:
> >>>>>>>>
> >>>>>>>> I think this sounds reasonable.
> >>>>>>>>
> >>>>>>>> Let's keep the "reconfiguration without stopping the job" out of
> >> this,
> >>>>>>>> because that would be a super big effort and if we approach that,
> >> then
> >>>>>>> in
> >>>>>>>> more generic way rather than specific to connector metrics.
> >>>>>>>>
> >>>>>>>> I would suggest to look at the following things before starting
> with
> >>>> any
> >>>>>>>> implementation work:
> >>>>>>>>
> >>>>>>>> - Try and find a committer to support this, otherwise it will be
> >> hard
> >>>>>>> to
> >>>>>>>> make progress
> >>>>>>>> - Start with defining a smaller set of "core metrics" and extend
> the
> >>>>>>> set
> >>>>>>>> later. I think that is easier than now blocking on reaching
> >> consensus
> >>>>>>> on a
> >>>>>>>> large group of metrics.
> >>>>>>>> - Find a solution to the problem Chesnay mentioned, that the
> >> "records
> >>>>>>> in"
> >>>>>>>> metric is somehow overloaded and exists already in the IO Metric
> >>>> group.
> >>>>>>>>
> >>>>>>>>
> >>>>>>>> On Mon, Mar 25, 2019 at 7:16 AM Becket Qin <be...@gmail.com>
> >>>>>>> wrote:
> >>>>>>>>
> >>>>>>>>> Hi Stephan,
> >>>>>>>>>
> >>>>>>>>> Thanks a lot for the feedback. All makes sense.
> >>>>>>>>>
> >>>>>>>>> It is a good suggestion to simply have an onRecord(numBytes,
> >>>> eventTime)
> >>>>>>>>> method for connector writers. It should meet most of the
> >>>> requirements,
> >>>>>>>>> individual
> >>>>>>>>>
> >>>>>>>>> The configurable metrics feature is something really useful,
> >>>>>>> especially if
> >>>>>>>>> we can somehow make it dynamically configurable without stopping
> >> the
> >>>>>>> jobs.
> >>>>>>>>> It might be better to make it a separate discussion because it
> is a
> >>>>>>> more
> >>>>>>>>> generic feature instead of only for connectors.
> >>>>>>>>>
> >>>>>>>>> So in order to make some progress, in this FLIP we can limit the
> >>>>>>> discussion
> >>>>>>>>> scope to the connector related items:
> >>>>>>>>>
> >>>>>>>>> - the standard connector metric names and types.
> >>>>>>>>> - the abstract ConnectorMetricHandler interface
> >>>>>>>>>
> >>>>>>>>> I'll start a separate thread to discuss other general metric
> >> related
> >>>>>>>>> enhancement items including:
> >>>>>>>>>
> >>>>>>>>> - optional metrics
> >>>>>>>>> - dynamic metric configuration
> >>>>>>>>> - potential combination with rate limiter
> >>>>>>>>>
> >>>>>>>>> Does this plan sound reasonable?
> >>>>>>>>>
> >>>>>>>>> Thanks,
> >>>>>>>>>
> >>>>>>>>> Jiangjie (Becket) Qin
> >>>>>>>>>
> >>>>>>>>> On Sat, Mar 23, 2019 at 5:53 AM Stephan Ewen <se...@apache.org>
> >>>> wrote:
> >>>>>>>>>
> >>>>>>>>>> Ignoring for a moment implementation details, this connector
> >> metrics
> >>>>>>> work
> >>>>>>>>>> is a really good thing to do, in my opinion
> >>>>>>>>>>
> >>>>>>>>>> The questions "oh, my job seems to be doing nothing, I am
> looking
> >> at
> >>>>>>> the
> >>>>>>>>> UI
> >>>>>>>>>> and the 'records in' value is still zero" is in the top three
> >>>> support
> >>>>>>>>>> questions I have been asked personally.
> >>>>>>>>>> Introspection into "how far is the consumer lagging behind"
> (event
> >>>>>>> time
> >>>>>>>>>> fetch latency) came up many times as well.
> >>>>>>>>>>
> >>>>>>>>>> So big +1 to solving this problem.
> >>>>>>>>>>
> >>>>>>>>>> About the exact design - I would try to go for the following
> >>>>>>> properties:
> >>>>>>>>>>
> >>>>>>>>>> - keep complexity of of connectors. Ideally the metrics handler
> >> has
> >>>> a
> >>>>>>>>>> single onRecord(numBytes, eventTime) method or so, and
> everything
> >>>>>>> else is
> >>>>>>>>>> internal to the handler. That makes it dead simple for the
> >>>> connector.
> >>>>>>> We
> >>>>>>>>>> can also think of an extensive scheme for connector specific
> >>>> metrics.
> >>>>>>>>>>
> >>>>>>>>>> - make it configurable on the job it cluster level which metrics
> >> the
> >>>>>>>>>> handler internally creates when that method is invoked.
> >>>>>>>>>>
> >>>>>>>>>> What do you think?
> >>>>>>>>>>
> >>>>>>>>>> Best,
> >>>>>>>>>> Stephan
> >>>>>>>>>>
> >>>>>>>>>>
> >>>>>>>>>> On Thu, Mar 21, 2019 at 10:42 AM Chesnay Schepler <
> >>>> chesnay@apache.org
> >>>>>>>>
> >>>>>>>>>> wrote:
> >>>>>>>>>>
> >>>>>>>>>>> As I said before, I believe this to be over-engineered and have
> >> no
> >>>>>>>>>>> interest in this implementation.
> >>>>>>>>>>>
> >>>>>>>>>>> There are conceptual issues like defining a duplicate
> >>>>>>>>> numBytesIn(PerSec)
> >>>>>>>>>>> metric that already exists for each operator.
> >>>>>>>>>>>
> >>>>>>>>>>> On 21.03.2019 06:13, Becket Qin wrote:
> >>>>>>>>>>>> A few updates to the thread. I uploaded a patch[1] as a
> complete
> >>>>>>>>>>>> example of how users can use the metrics in the future.
> >>>>>>>>>>>>
> >>>>>>>>>>>> Some thoughts below after taking a look at the
> >> AbstractMetricGroup
> >>>>>>>>> and
> >>>>>>>>>>>> its subclasses.
> >>>>>>>>>>>>
> >>>>>>>>>>>> This patch intends to provide convenience for Flink connector
> >>>>>>>>>>>> implementations to follow metrics standards proposed in
> FLIP-33.
> >>>> It
> >>>>>>>>>>>> also try to enhance the metric management in general way to
> help
> >>>>>>>>> users
> >>>>>>>>>>>> with:
> >>>>>>>>>>>>
> >>>>>>>>>>>> 1. metric definition
> >>>>>>>>>>>> 2. metric dependencies check
> >>>>>>>>>>>> 3. metric validation
> >>>>>>>>>>>> 4. metric control (turn on / off particular metrics)
> >>>>>>>>>>>>
> >>>>>>>>>>>> This patch wraps |MetricGroup| to extend the functionality of
> >>>>>>>>>>>> |AbstractMetricGroup| and its subclasses. The
> >>>>>>>>>>>> |AbstractMetricGroup| mainly focus on the metric group
> >> hierarchy,
> >>>>>>> but
> >>>>>>>>>>>> does not really manage the metrics other than keeping them in
> a
> >>>> Map.
> >>>>>>>>>>>>
> >>>>>>>>>>>> Ideally we should only have one entry point for the metrics.
> >>>>>>>>>>>>
> >>>>>>>>>>>> Right now the entry point is |AbstractMetricGroup|. However,
> >>>> besides
> >>>>>>>>>>>> the missing functionality mentioned above,
> |AbstractMetricGroup|
> >>>>>>>>> seems
> >>>>>>>>>>>> deeply rooted in Flink runtime. We could extract it out to
> >>>>>>>>>>>> flink-metrics in order to use it for generic purpose. There
> will
> >>>> be
> >>>>>>>>>>>> some work, though.
> >>>>>>>>>>>>
> >>>>>>>>>>>> Another approach is to make |AbstractMetrics| in this patch as
> >> the
> >>>>>>>>>>>> metric entry point. It wraps metric group and provides the
> >> missing
> >>>>>>>>>>>> functionalities. Then we can roll out this pattern to runtime
> >>>>>>>>>>>> components gradually as well.
> >>>>>>>>>>>>
> >>>>>>>>>>>> My first thought is that the latter approach gives a more
> smooth
> >>>>>>>>>>>> migration. But I am also OK with doing a refactoring on the
> >>>>>>>>>>>> |AbstractMetricGroup| family.
> >>>>>>>>>>>>
> >>>>>>>>>>>>
> >>>>>>>>>>>> Thanks,
> >>>>>>>>>>>>
> >>>>>>>>>>>> Jiangjie (Becket) Qin
> >>>>>>>>>>>>
> >>>>>>>>>>>> [1] https://github.com/becketqin/flink/pull/1
> >>>>>>>>>>>>
> >>>>>>>>>>>> On Mon, Feb 25, 2019 at 2:32 PM Becket Qin <
> >> becket.qin@gmail.com
> >>>>>>>>>>>> <ma...@gmail.com>> wrote:
> >>>>>>>>>>>>
> >>>>>>>>>>>> Hi Chesnay,
> >>>>>>>>>>>>
> >>>>>>>>>>>> It might be easier to discuss some implementation details in
> >> the
> >>>>>>>>>>>> PR review instead of in the FLIP discussion thread. I have a
> >>>>>>>>> patch
> >>>>>>>>>>>> for Kafka connectors ready but haven't submitted the PR yet.
> >>>>>>>>>>>> Hopefully that will help explain a bit more.
> >>>>>>>>>>>>
> >>>>>>>>>>>> ** Re: metric type binding
> >>>>>>>>>>>> This is a valid point that worths discussing. If I understand
> >>>>>>>>>>>> correctly, there are two points:
> >>>>>>>>>>>>
> >>>>>>>>>>>> 1. Metric type / interface does not matter as long as the
> >> metric
> >>>>>>>>>>>> semantic is clearly defined.
> >>>>>>>>>>>> Conceptually speaking, I agree that as long as the metric
> >>>>>>>>> semantic
> >>>>>>>>>>>> is defined, metric type does not matter. To some extent, Gauge
> >> /
> >>>>>>>>>>>> Counter / Meter / Histogram themselves can be think of as some
> >>>>>>>>>>>> well-recognized semantics, if you wish. In Flink, these metric
> >>>>>>>>>>>> semantics have their associated interface classes. In
> practice,
> >>>>>>>>>>>> such semantic to interface binding seems necessary for
> >> different
> >>>>>>>>>>>> components to communicate. Simply standardize the semantic of
> >>>>>>>>> the
> >>>>>>>>>>>> connector metrics seems not sufficient for people to build
> >>>>>>>>>>>> ecosystem on top of. At the end of the day, we still need to
> >>>> have
> >>>>>>>>>>>> some embodiment of the metric semantics that people can
> program
> >>>>>>>>>>>> against.
> >>>>>>>>>>>>
> >>>>>>>>>>>> 2. Sometimes the same metric semantic can be exposed using
> >>>>>>>>>>>> different metric types / interfaces.
> >>>>>>>>>>>> This is a good point. Counter and Gauge-as-a-Counter are
> pretty
> >>>>>>>>>>>> much interchangeable. This is more of a trade-off between the
> >>>>>>>>> user
> >>>>>>>>>>>> experience of metric producers and consumers. The metric
> >>>>>>>>> producers
> >>>>>>>>>>>> want to use Counter or Gauge depending on whether the counter
> >> is
> >>>>>>>>>>>> already tracked in code, while ideally the metric consumers
> >> only
> >>>>>>>>>>>> want to see a single metric type for each metric. I am leaning
> >>>>>>>>>>>> towards to make the metric producers happy, i.e. allow Gauge /
> >>>>>>>>>>>> Counter metric type, and the the metric consumers handle the
> >>>> type
> >>>>>>>>>>>> variation. The reason is that in practice, there might be more
> >>>>>>>>>>>> connector implementations than metric reporter
> implementations.
> >>>>>>>>> We
> >>>>>>>>>>>> could also provide some helper method to facilitate reading
> >> from
> >>>>>>>>>>>> such variable metric type.
> >>>>>>>>>>>>
> >>>>>>>>>>>>
> >>>>>>>>>>>> Just some quick replies to the comments around implementation
> >>>>>>>>>>> details.
> >>>>>>>>>>>>
> >>>>>>>>>>>> 4) single place where metrics are registered except
> >>>>>>>>>>>> connector-specific
> >>>>>>>>>>>> ones (which we can't really avoid).
> >>>>>>>>>>>>
> >>>>>>>>>>>> Register connector specific ones in a single place is actually
> >>>>>>>>>>>> something that I want to achieve.
> >>>>>>>>>>>>
> >>>>>>>>>>>> 2) I'm talking about time-series databases like
> Prometheus.
> >>>>>>>>> We
> >>>>>>>>>>>> would
> >>>>>>>>>>>> only have a gauge metric exposing the last
> >>>> fetchTime/emitTime
> >>>>>>>>>>>> that is
> >>>>>>>>>>>> regularly reported to the backend (Prometheus), where a
> >> user
> >>>>>>>>>>>> could build
> >>>>>>>>>>>> a histogram of his choosing when/if he wants it.
> >>>>>>>>>>>>
> >>>>>>>>>>>> Not sure if such downsampling works. As an example, if a user
> >>>>>>>>>>>> complains that there are some intermittent latency spikes
> >> (maybe
> >>>>>>>>> a
> >>>>>>>>>>>> few records in 10 seconds) in their processing system. Having
> a
> >>>>>>>>>>>> Gauge sampling instantaneous latency seems unlikely useful.
> >>>>>>>>>>>> However by looking at actual 99.9 percentile latency might
> >> help.
> >>>>>>>>>>>>
> >>>>>>>>>>>> Thanks,
> >>>>>>>>>>>>
> >>>>>>>>>>>> Jiangjie (Becket) Qin
> >>>>>>>>>>>>
> >>>>>>>>>>>>
> >>>>>>>>>>>> On Fri, Feb 22, 2019 at 9:30 PM Chesnay Schepler
> >>>>>>>>>>>> <chesnay@apache.org <ma...@apache.org>> wrote:
> >>>>>>>>>>>>
> >>>>>>>>>>>> Re: over complication of implementation.
> >>>>>>>>>>>>
> >>>>>>>>>>>> I think I get understand better know what you're shooting
> >>>>>>>>> for,
> >>>>>>>>>>>> effectively something like the OperatorIOMetricGroup.
> >>>>>>>>>>>> But still, re-define setupConnectorMetrics() to accept a
> >> set
> >>>>>>>>>>>> of flags
> >>>>>>>>>>>> for counters/meters(ans _possibly_ histograms) along with
> a
> >>>>>>>>>>>> set of
> >>>>>>>>>>>> well-defined Optional<Gauge<?>>, and return the group.
> >>>>>>>>>>>>
> >>>>>>>>>>>> Solves all issues as far as i can tell:
> >>>>>>>>>>>> 1) no metrics must be created manually (except Gauges,
> >> which
> >>>>>>>>>> are
> >>>>>>>>>>>> effectively just Suppliers and you can't get around this),
> >>>>>>>>>>>> 2) additional metrics can be registered on the returned
> >>>>>>>>> group,
> >>>>>>>>>>>> 3) see 1),
> >>>>>>>>>>>> 4) single place where metrics are registered except
> >>>>>>>>>>>> connector-specific
> >>>>>>>>>>>> ones (which we can't really avoid).
> >>>>>>>>>>>>
> >>>>>>>>>>>> Re: Histogram
> >>>>>>>>>>>>
> >>>>>>>>>>>> 1) As an example, whether "numRecordsIn" is exposed as a
> >>>>>>>>>>>> Counter or a
> >>>>>>>>>>>> Gauge should be irrelevant. So far we're using the metric
> >>>>>>>>> type
> >>>>>>>>>>>> that is
> >>>>>>>>>>>> the most convenient at exposing a given value. If there is
> >>>>>>>>>>>> some backing
> >>>>>>>>>>>> data-structure that we want to expose some data from we
> >>>>>>>>>>>> typically opt
> >>>>>>>>>>>> for a Gauge, as otherwise we're just mucking around with
> >> the
> >>>>>>>>>>>> Meter/Counter API to get it to match. Similarly, if we
> want
> >>>>>>>>> to
> >>>>>>>>>>>> count
> >>>>>>>>>>>> something but no current count exists we typically added a
> >>>>>>>>>>>> Counter.
> >>>>>>>>>>>> That's why attaching semantics to metric types makes
> little
> >>>>>>>>>>>> sense (but
> >>>>>>>>>>>> unfortunately several reporters already do it); for
> >>>>>>>>>>>> counters/meters
> >>>>>>>>>>>> certainly, but the majority of metrics are gauges.
> >>>>>>>>>>>>
> >>>>>>>>>>>> 2) I'm talking about time-series databases like
> Prometheus.
> >>>>>>>>> We
> >>>>>>>>>>>> would
> >>>>>>>>>>>> only have a gauge metric exposing the last
> >>>> fetchTime/emitTime
> >>>>>>>>>>>> that is
> >>>>>>>>>>>> regularly reported to the backend (Prometheus), where a
> >> user
> >>>>>>>>>>>> could build
> >>>>>>>>>>>> a histogram of his choosing when/if he wants it.
> >>>>>>>>>>>>
> >>>>>>>>>>>> On 22.02.2019 13:57, Becket Qin wrote:
> >>>>>>>>>>>>> Hi Chesnay,
> >>>>>>>>>>>>>
> >>>>>>>>>>>>> Thanks for the explanation.
> >>>>>>>>>>>>>
> >>>>>>>>>>>>> ** Re: FLIP
> >>>>>>>>>>>>> I might have misunderstood this, but it seems that "major
> >>>>>>>>>>>> changes" are well
> >>>>>>>>>>>>> defined in FLIP. The full contents is following:
> >>>>>>>>>>>>> What is considered a "major change" that needs a FLIP?
> >>>>>>>>>>>>>
> >>>>>>>>>>>>> Any of the following should be considered a major change:
> >>>>>>>>>>>>>
> >>>>>>>>>>>>> - Any major new feature, subsystem, or piece of
> >>>>>>>>>>>> functionality
> >>>>>>>>>>>>> - *Any change that impacts the public interfaces of the
> >>>>>>>>>>>> project*
> >>>>>>>>>>>>>
> >>>>>>>>>>>>> What are the "public interfaces" of the project?
> >>>>>>>>>>>>>
> >>>>>>>>>>>>>
> >>>>>>>>>>>>>
> >>>>>>>>>>>>> *All of the following are public interfaces *that people
> >>>>>>>>>>>> build around:
> >>>>>>>>>>>>>
> >>>>>>>>>>>>> - DataStream and DataSet API, including classes related
> >>>>>>>>>>>> to that, such as
> >>>>>>>>>>>>> StreamExecutionEnvironment
> >>>>>>>>>>>>>
> >>>>>>>>>>>>>
> >>>>>>>>>>>>> - Classes marked with the @Public annotation
> >>>>>>>>>>>>>
> >>>>>>>>>>>>>
> >>>>>>>>>>>>> - On-disk binary formats, such as
> >>>>>>>>> checkpoints/savepoints
> >>>>>>>>>>>>>
> >>>>>>>>>>>>>
> >>>>>>>>>>>>> - User-facing scripts/command-line tools, i.e.
> >>>>>>>>>>>> bin/flink, Yarn scripts,
> >>>>>>>>>>>>> Mesos scripts
> >>>>>>>>>>>>>
> >>>>>>>>>>>>>
> >>>>>>>>>>>>> - Configuration settings
> >>>>>>>>>>>>>
> >>>>>>>>>>>>>
> >>>>>>>>>>>>> - *Exposed monitoring information*
> >>>>>>>>>>>>>
> >>>>>>>>>>>>>
> >>>>>>>>>>>>> So any monitoring information change is considered as
> >>>>>>>>> public
> >>>>>>>>>>>> interface, and
> >>>>>>>>>>>>> any public interface change is considered as a "major
> >>>>>>>>>> change".
> >>>>>>>>>>>>>
> >>>>>>>>>>>>>
> >>>>>>>>>>>>> ** Re: over complication of implementation.
> >>>>>>>>>>>>>
> >>>>>>>>>>>>> Although this is more of implementation details that is not
> >>>>>>>>>>>> covered by the
> >>>>>>>>>>>>> FLIP. But it may be worth discussing.
> >>>>>>>>>>>>>
> >>>>>>>>>>>>> First of all, I completely agree that we should use the
> >>>>>>>>>>>> simplest way to
> >>>>>>>>>>>>> achieve our goal. To me the goal is the following:
> >>>>>>>>>>>>> 1. Clear connector conventions and interfaces.
> >>>>>>>>>>>>> 2. The easiness of creating a connector.
> >>>>>>>>>>>>>
> >>>>>>>>>>>>> Both of them are important to the prosperity of the
> >>>>>>>>>>>> connector ecosystem. So
> >>>>>>>>>>>>> I'd rather abstract as much as possible on our side to make
> >>>>>>>>>>>> the connector
> >>>>>>>>>>>>> developer's work lighter. Given this goal, a static util
> >>>>>>>>>>>> method approach
> >>>>>>>>>>>>> might have a few drawbacks:
> >>>>>>>>>>>>> 1. Users still have to construct the metrics by themselves.
> >>>>>>>>>>>> (And note that
> >>>>>>>>>>>>> this might be erroneous by itself. For example, a customer
> >>>>>>>>>>>> wrapper around
> >>>>>>>>>>>>> dropwizard meter maybe used instead of MeterView).
> >>>>>>>>>>>>> 2. When connector specific metrics are added, it is
> >>>>>>>>>>>> difficult to enforce
> >>>>>>>>>>>>> the scope to be the same as standard metrics.
> >>>>>>>>>>>>> 3. It seems that a method proliferation is inevitable if we
> >>>>>>>>>>>> want to apply
> >>>>>>>>>>>>> sanity checks. e.g. The metric of numBytesIn was not
> >>>>>>>>>>>> registered for a meter.
> >>>>>>>>>>>>> 4. Metrics are still defined in random places and hard to
> >>>>>>>>>>> track.
> >>>>>>>>>>>>>
> >>>>>>>>>>>>> The current PR I had was inspired by the Config system in
> >>>>>>>>>>>> Kafka, which I
> >>>>>>>>>>>>> found pretty handy. In fact it is not only used by Kafka
> >>>>>>>>>>>> itself but even
> >>>>>>>>>>>>> some other projects that depend on Kafka. I am not saying
> >>>>>>>>>>>> this approach is
> >>>>>>>>>>>>> perfect. But I think it worths to save the work for
> >>>>>>>>>>>> connector writers and
> >>>>>>>>>>>>> encourage more systematic implementation. That being said,
> >>>>>>>>> I
> >>>>>>>>>>>> am fully open
> >>>>>>>>>>>>> to suggestions.
> >>>>>>>>>>>>>
> >>>>>>>>>>>>>
> >>>>>>>>>>>>> Re: Histogram
> >>>>>>>>>>>>> I think there are two orthogonal questions around those
> >>>>>>>>>>> metrics:
> >>>>>>>>>>>>>
> >>>>>>>>>>>>> 1. Regardless of the metric type, by just looking at the
> >>>>>>>>>>>> meaning of a
> >>>>>>>>>>>>> metric, is generic to all connectors? If the answer is yes,
> >>>>>>>>>>>> we should
> >>>>>>>>>>>>> include the metric into the convention. No matter whether
> >>>>>>>>> we
> >>>>>>>>>>>> include it
> >>>>>>>>>>>>> into the convention or not, some connector implementations
> >>>>>>>>>>>> will emit such
> >>>>>>>>>>>>> metric. It is better to have a convention than letting each
> >>>>>>>>>>>> connector do
> >>>>>>>>>>>>> random things.
> >>>>>>>>>>>>>
> >>>>>>>>>>>>> 2. If a standard metric is a histogram, what should we do?
> >>>>>>>>>>>>> I agree that we should make it clear that using histograms
> >>>>>>>>>>>> will have
> >>>>>>>>>>>>> performance risk. But I do see histogram is useful in some
> >>>>>>>>>>>> fine-granularity
> >>>>>>>>>>>>> debugging where one do not have the luxury to stop the
> >>>>>>>>>>>> system and inject
> >>>>>>>>>>>>> more inspection code. So the workaround I am thinking is to
> >>>>>>>>>>>> provide some
> >>>>>>>>>>>>> implementation suggestions. Assume later on we have a
> >>>>>>>>>>>> mechanism of
> >>>>>>>>>>>>> selective metrics. In the abstract metrics class we can
> >>>>>>>>>>>> disable those
> >>>>>>>>>>>>> metrics by default individual connector writers does not
> >>>>>>>>>>>> have to do
> >>>>>>>>>>>>> anything (this is another advantage of having an
> >>>>>>>>>>>> AbstractMetrics instead of
> >>>>>>>>>>>>> static util methods.)
> >>>>>>>>>>>>>
> >>>>>>>>>>>>> I am not sure I fully understand the histogram in the
> >>>>>>>>>>>> backend approach. Can
> >>>>>>>>>>>>> you explain a bit more? Do you mean emitting the raw data,
> >>>>>>>>>>>> e.g. fetchTime
> >>>>>>>>>>>>> and emitTime with each record and let the histogram
> >>>>>>>>>>>> computation happen in
> >>>>>>>>>>>>> the background? Or let the processing thread putting the
> >>>>>>>>>>>> values into a
> >>>>>>>>>>>>> queue and have a separate thread polling from the queue and
> >>>>>>>>>>>> add them into
> >>>>>>>>>>>>> the histogram?
> >>>>>>>>>>>>>
> >>>>>>>>>>>>> Thanks,
> >>>>>>>>>>>>>
> >>>>>>>>>>>>> Jiangjie (Becket) Qin
> >>>>>>>>>>>>>
> >>>>>>>>>>>>>
> >>>>>>>>>>>>>
> >>>>>>>>>>>>>
> >>>>>>>>>>>>>
> >>>>>>>>>>>>> On Fri, Feb 22, 2019 at 4:34 PM Chesnay Schepler
> >>>>>>>>>>>> <chesnay@apache.org <ma...@apache.org>> wrote:
> >>>>>>>>>>>>>
> >>>>>>>>>>>>>> Re: Flip
> >>>>>>>>>>>>>> The very first line under both the main header and Purpose
> >>>>>>>>>>>> section
> >>>>>>>>>>>>>> describe Flips as "major changes", which this isn't.
> >>>>>>>>>>>>>>
> >>>>>>>>>>>>>> Re: complication
> >>>>>>>>>>>>>> I'm not arguing against standardization, but again an
> >>>>>>>>>>>> over-complicated
> >>>>>>>>>>>>>> implementation when a static utility method would be
> >>>>>>>>>>>> sufficient.
> >>>>>>>>>>>>>>
> >>>>>>>>>>>>>> public static void setupConnectorMetrics(
> >>>>>>>>>>>>>> MetricGroup operatorMetricGroup,
> >>>>>>>>>>>>>> String connectorName,
> >>>>>>>>>>>>>> Optional<Gauge<Long>> numRecordsIn,
> >>>>>>>>>>>>>> ...)
> >>>>>>>>>>>>>>
> >>>>>>>>>>>>>> This gives you all you need:
> >>>>>>>>>>>>>> * a well-defined set of metrics for a connector to opt-in
> >>>>>>>>>>>>>> * standardized naming schemes for scope and individual
> >>>>>>>>>> metrics
> >>>>>>>>>>>>>> * standardize metric types (although personally I'm not
> >>>>>>>>>>>> interested in that
> >>>>>>>>>>>>>> since metric types should be considered syntactic sugar)
> >>>>>>>>>>>>>>
> >>>>>>>>>>>>>> Re: Configurable Histogram
> >>>>>>>>>>>>>> If anything they _must_ be turned off by default, but the
> >>>>>>>>>>>> metric system is
> >>>>>>>>>>>>>> already exposing so many options that I'm not too keen on
> >>>>>>>>>>>> adding even more.
> >>>>>>>>>>>>>> You have also only addressed my first argument against
> >>>>>>>>>>>> histograms
> >>>>>>>>>>>>>> (performance), the second one still stands (calculate
> >>>>>>>>>>>> histogram in metric
> >>>>>>>>>>>>>> backends instead).
> >>>>>>>>>>>>>>
> >>>>>>>>>>>>>> On 21.02.2019 16:27, Becket Qin wrote:
> >>>>>>>>>>>>>>> Hi Chesnay,
> >>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>> Thanks for the comments. I think this is worthy of a FLIP
> >>>>>>>>>>>> because it is
> >>>>>>>>>>>>>>> public API. According to the FLIP description a FlIP is
> >>>>>>>>>>>> required in case
> >>>>>>>>>>>>>> of:
> >>>>>>>>>>>>>>> - Any change that impacts the public interfaces of
> >>>>>>>>>>>> the project
> >>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>> and the following entry is found in the definition of
> >>>>>>>>>>>> "public interface".
> >>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>> - Exposed monitoring information
> >>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>> Metrics are critical to any production system. So a clear
> >>>>>>>>>>>> metric
> >>>>>>>>>>>>>> definition
> >>>>>>>>>>>>>>> is important for any serious users. For an organization
> >>>>>>>>>>>> with large Flink
> >>>>>>>>>>>>>>> installation, change in metrics means great amount of
> >>>>>>>>>>>> work. So such
> >>>>>>>>>>>>>> changes
> >>>>>>>>>>>>>>> do need to be fully discussed and documented.
> >>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>> ** Re: Histogram.
> >>>>>>>>>>>>>>> We can discuss whether there is a better way to expose
> >>>>>>>>>>>> metrics that are
> >>>>>>>>>>>>>>> suitable for histograms. My micro-benchmark on various
> >>>>>>>>>>>> histogram
> >>>>>>>>>>>>>>> implementations also indicates that they are
> >>>>>>>>> significantly
> >>>>>>>>>>>> slower than
> >>>>>>>>>>>>>>> other metric types. But I don't think that means never
> >>>>>>>>> use
> >>>>>>>>>>>> histogram, but
> >>>>>>>>>>>>>>> means use it with caution. For example, we can suggest
> >>>>>>>>> the
> >>>>>>>>>>>>>> implementations
> >>>>>>>>>>>>>>> to turn them off by default and only turn it on for a
> >>>>>>>>>>>> small amount of
> >>>>>>>>>>>>>> time
> >>>>>>>>>>>>>>> when performing some micro-debugging.
> >>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>> ** Re: complication:
> >>>>>>>>>>>>>>> Connector conventions are essential for Flink ecosystem.
> >>>>>>>>>>>> Flink connectors
> >>>>>>>>>>>>>>> pool is probably the most important part of Flink, just
> >>>>>>>>>>>> like any other
> >>>>>>>>>>>>>> data
> >>>>>>>>>>>>>>> system. Clear conventions of connectors will help build
> >>>>>>>>>>>> Flink ecosystem
> >>>>>>>>>>>>>> in
> >>>>>>>>>>>>>>> a more organic way.
> >>>>>>>>>>>>>>> Take the metrics convention as an example, imagine
> >>>>>>>>> someone
> >>>>>>>>>>>> has developed
> >>>>>>>>>>>>>> a
> >>>>>>>>>>>>>>> Flink connector for System foo, and another developer may
> >>>>>>>>>>>> have developed
> >>>>>>>>>>>>>> a
> >>>>>>>>>>>>>>> monitoring and diagnostic framework for Flink which
> >>>>>>>>>>>> analyzes the Flink
> >>>>>>>>>>>>>> job
> >>>>>>>>>>>>>>> performance based on metrics. With a clear metric
> >>>>>>>>>>>> convention, those two
> >>>>>>>>>>>>>>> projects could be developed independently. Once users put
> >>>>>>>>>>>> them together,
> >>>>>>>>>>>>>>> it would work without additional modifications. This
> >>>>>>>>>>>> cannot be easily
> >>>>>>>>>>>>>>> achieved by just defining a few constants.
> >>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>> ** Re: selective metrics:
> >>>>>>>>>>>>>>> Sure, we can discuss that in a separate thread.
> >>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>> @Dawid
> >>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>> ** Re: latency / fetchedLatency
> >>>>>>>>>>>>>>> The primary purpose of establish such a convention is to
> >>>>>>>>>>>> help developers
> >>>>>>>>>>>>>>> write connectors in a more compatible way. The convention
> >>>>>>>>>>>> is supposed to
> >>>>>>>>>>>>>> be
> >>>>>>>>>>>>>>> defined more proactively. So when look at the convention,
> >>>>>>>>>>>> it seems more
> >>>>>>>>>>>>>>> important to see if the concept is applicable to
> >>>>>>>>>>>> connectors in general.
> >>>>>>>>>>>>>> It
> >>>>>>>>>>>>>>> might be true so far only Kafka connector reports
> >>>>>>>>> latency.
> >>>>>>>>>>>> But there
> >>>>>>>>>>>>>> might
> >>>>>>>>>>>>>>> be hundreds of other connector implementations in the
> >>>>>>>>>>>> Flink ecosystem,
> >>>>>>>>>>>>>>> though not in the Flink repo, and some of them also emits
> >>>>>>>>>>>> latency. I
> >>>>>>>>>>>>>> think
> >>>>>>>>>>>>>>> a lot of other sources actually also has an append
> >>>>>>>>>>>> timestamp. e.g.
> >>>>>>>>>>>>>> database
> >>>>>>>>>>>>>>> bin logs and some K-V stores. So I wouldn't be surprised
> >>>>>>>>>>>> if some database
> >>>>>>>>>>>>>>> connector can also emit latency metrics.
> >>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>> Thanks,
> >>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>> Jiangjie (Becket) Qin
> >>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>> On Thu, Feb 21, 2019 at 10:14 PM Chesnay Schepler
> >>>>>>>>>>>> <chesnay@apache.org <ma...@apache.org>>
> >>>>>>>>>>>>>>> wrote:
> >>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>> Regarding 2) It doesn't make sense to investigate this
> >>>>>>>>> as
> >>>>>>>>>>>> part of this
> >>>>>>>>>>>>>>>> FLIP. This is something that could be of interest for
> >>>>>>>>> the
> >>>>>>>>>>>> entire metric
> >>>>>>>>>>>>>>>> system, and should be designed for as such.
> >>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>> Regarding the proposal as a whole:
> >>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>> Histogram metrics shall not be added to the core of
> >>>>>>>>>>>> Flink. They are
> >>>>>>>>>>>>>>>> significantly more expensive than other metrics, and
> >>>>>>>>>>>> calculating
> >>>>>>>>>>>>>>>> histograms in the application is regarded as an
> >>>>>>>>>>>> anti-pattern by several
> >>>>>>>>>>>>>>>> metric backends, who instead recommend to expose the raw
> >>>>>>>>>>>> data and
> >>>>>>>>>>>>>>>> calculate the histogram in the backend.
> >>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>> Second, this seems overly complicated. Given that we
> >>>>>>>>>>>> already established
> >>>>>>>>>>>>>>>> that not all connectors will export all metrics we are
> >>>>>>>>>>>> effectively
> >>>>>>>>>>>>>>>> reducing this down to a consistent naming scheme. We
> >>>>>>>>>>>> don't need anything
> >>>>>>>>>>>>>>>> sophisticated for that; basically just a few constants
> >>>>>>>>>>>> that all
> >>>>>>>>>>>>>>>> connectors use.
> >>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>> I'm not convinced that this is worthy of a FLIP.
> >>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>> On 21.02.2019 14:26, Dawid Wysakowicz wrote:
> >>>>>>>>>>>>>>>>> Hi,
> >>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>> Ad 1. In general I undestand and I agree. But those
> >>>>>>>>>>>> particular metrics
> >>>>>>>>>>>>>>>>> (latency, fetchLatency), right now would only be
> >>>>>>>>>>>> reported if user uses
> >>>>>>>>>>>>>>>>> KafkaConsumer with internal timestampAssigner with
> >>>>>>>>>>>> StreamCharacteristic
> >>>>>>>>>>>>>>>>> set to EventTime, right? That sounds like a very
> >>>>>>>>>>>> specific case. I am
> >>>>>>>>>>>>>> not
> >>>>>>>>>>>>>>>>> sure if we should introduce a generic metric that will
> >>>>>>>>> be
> >>>>>>>>>>>>>>>>> disabled/absent for most of implementations.
> >>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>> Ad.2 That sounds like an orthogonal issue, that might
> >>>>>>>>>>>> make sense to
> >>>>>>>>>>>>>>>>> investigate in the future.
> >>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>> Best,
> >>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>> Dawid
> >>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>> On 21/02/2019 13:20, Becket Qin wrote:
> >>>>>>>>>>>>>>>>>> Hi Dawid,
> >>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>> Thanks for the feedback. That makes sense to me. There
> >>>>>>>>>>>> are two cases
> >>>>>>>>>>>>>> to
> >>>>>>>>>>>>>>>> be
> >>>>>>>>>>>>>>>>>> addressed.
> >>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>> 1. The metrics are supposed to be a guidance. It is
> >>>>>>>>>>>> likely that a
> >>>>>>>>>>>>>>>> connector
> >>>>>>>>>>>>>>>>>> only supports some but not all of the metrics. In that
> >>>>>>>>>>>> case, each
> >>>>>>>>>>>>>>>> connector
> >>>>>>>>>>>>>>>>>> implementation should have the freedom to decide which
> >>>>>>>>>>>> metrics are
> >>>>>>>>>>>>>>>>>> reported. For the metrics that are supported, the
> >>>>>>>>>>>> guidance should be
> >>>>>>>>>>>>>>>>>> followed.
> >>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>> 2. Sometimes users may want to disable certain metrics
> >>>>>>>>>>>> for some reason
> >>>>>>>>>>>>>>>>>> (e.g. performance / reprocessing of data). A generic
> >>>>>>>>>>>> mechanism should
> >>>>>>>>>>>>>> be
> >>>>>>>>>>>>>>>>>> provided to allow user choose which metrics are
> >>>>>>>>>>>> reported. This
> >>>>>>>>>>>>>> mechanism
> >>>>>>>>>>>>>>>>>> should also be honored by the connector
> >>>>>>>>> implementations.
> >>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>> Does this sound reasonable to you?
> >>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>> Thanks,
> >>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>> Jiangjie (Becket) Qin
> >>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>> On Thu, Feb 21, 2019 at 4:22 PM Dawid Wysakowicz <
> >>>>>>>>>>>>>>>> dwysakowicz@apache.org <ma...@apache.org>>
> >>>>>>>>>>>>>>>>>> wrote:
> >>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>> Hi,
> >>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>> Generally I like the idea of having a unified,
> >>>>>>>>>>>> standard set of
> >>>>>>>>>>>>>> metrics
> >>>>>>>>>>>>>>>> for
> >>>>>>>>>>>>>>>>>>> all connectors. I have some slight concerns about
> >>>>>>>>>>>> fetchLatency and
> >>>>>>>>>>>>>>>>>>> latency though. They are computed based on EventTime
> >>>>>>>>>>>> which is not a
> >>>>>>>>>>>>>>>> purely
> >>>>>>>>>>>>>>>>>>> technical feature. It depends often on some business
> >>>>>>>>>>>> logic, might be
> >>>>>>>>>>>>>>>> absent
> >>>>>>>>>>>>>>>>>>> or defined after source. Those metrics could also
> >>>>>>>>>>>> behave in a weird
> >>>>>>>>>>>>>>>> way in
> >>>>>>>>>>>>>>>>>>> case of replaying backlog. Therefore I am not sure if
> >>>>>>>>>>>> we should
> >>>>>>>>>>>>>> include
> >>>>>>>>>>>>>>>>>>> those metrics by default. Maybe we could at least
> >>>>>>>>>>>> introduce a feature
> >>>>>>>>>>>>>>>>>>> switch for them? What do you think?
> >>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>> Best,
> >>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>> Dawid
> >>>>>>>>>>>>>>>>>>> On 21/02/2019 03:13, Becket Qin wrote:
> >>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>> Bump. If there is no objections to the proposed
> >>>>>>>>>>>> metrics. I'll start a
> >>>>>>>>>>>>>>>>>>> voting thread later toady.
> >>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>> Thanks,
> >>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>> Jiangjie (Becket) Qin
> >>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>> On Mon, Feb 11, 2019 at 8:17 PM Becket Qin
> >>>>>>>>>>>> <becket.qin@gmail.com <ma...@gmail.com>> <
> >>>>>>>>>>>>>>>> becket.qin@gmail.com <ma...@gmail.com>>
> >>>>>>>>>> wrote:
> >>>>>>>>>>>>>>>>>>> Hi folks,
> >>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>> I would like to start the FLIP discussion thread
> >>>>>>>>> about
> >>>>>>>>>>>> standardize
> >>>>>>>>>>>>>> the
> >>>>>>>>>>>>>>>>>>> connector metrics.
> >>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>> In short, we would like to provide a convention of
> >>>>>>>>>>>> Flink connector
> >>>>>>>>>>>>>>>>>>> metrics. It will help simplify the monitoring and
> >>>>>>>>>>>> alerting on Flink
> >>>>>>>>>>>>>>>> jobs.
> >>>>>>>>>>>>>>>>>>> The FLIP link is following:
> >>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>
> >>>>>>>>>>>>
> >>>>>>>>>>>
> >>>>>>>>>>
> >>>>>>>>>
> >>>>>>>
> >>>>
> >>
> https://cwiki.apache.org/confluence/display/FLINK/FLIP-33%3A+Standardize+Connector+Metrics
> >>>>>>>>>>>>>>>>>>> Thanks,
> >>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>> Jiangjie (Becket) Qin
> >>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>
> >>>>>>>>>>>>
> >>>>>>>>>>>
> >>>>>>>>>>>
> >>>>>>>>>>
> >>>>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>
> >>>>
> >>>>
> >>
> >>
> >>
>
>
Re: [DISCUSS] FLIP-33: Standardize connector metrics
Posted by Piotr Nowojski <pi...@ververica.com>.
Hi Becket,
Thanks for the answer :)
> By time-based metric, I meant the portion of time spent on producing the
> record to downstream. For example, a source connector can report that it's
> spending 80% of time to emit record to downstream processing pipeline. In
> another case, a sink connector may report that its spending 30% of time
> producing the records to the external system.
>
> This is in some sense equivalent to the buffer usage metric:
> - 80% of time spent on emitting records to downstream ---> downstream
> node is bottleneck ---> output buffer is probably full.
> - 30% of time spent on emitting records to downstream ---> downstream
> node is not bottleneck ---> output buffer is probably not full.
If by “time spent on emitting records to downstream” you understand “waiting on back pressure”, then I see your point. And I agree that some kind of ratio/time based metric gives you more information. However under “time spent on emitting records to downstream” might be hidden the following (extreme) situation:
1. Job is barely able to handle influx of records, there is 99% CPU/resource usage in the cluster, but nobody is bottlenecked/backpressured, all output buffers are empty, everybody is waiting in 1% of it’s time for more records to process.
2. 80% time can still be spent on "down stream operators”, because they are the CPU intensive operations, but this doesn’t mean that increasing the parallelism down the stream will help with anything there. To the contrary, increasing parallelism of the source operator might help to increase resource utilisation up to 100%.
However, this “time based/ratio” approach can be extended to in/output buffer usage. Besides collecting an information that input/output buffer is full/empty, we can probe profile how often are buffer empty/full. If output buffer is full 1% of times, there is almost no back pressure. If it’s full 80% of times, there is some back pressure, if it’s full 99.9% of times, there is huge back pressure.
Now for autoscaling you could compare the input & output buffers fill ratio:
1. Both are high, the source of bottleneck is down the stream
2. Output is low, input is high, this is the bottleneck and the higher the difference, the bigger source of bottleneck is this is operator/task
3. Output is high, input is low - there was some load spike that we are currently finishing to process
But long story short, we are probably diverging from the topic of this discussion, and we can discuss this at some later point.
For now, for sources:
as I wrote before, +1 for:
- pending.bytes, Gauge
- pending.messages, Gauge
When we will be developing/discussing SourceReader from FLIP-27 we might then add:
- in-memory.buffer.usage (0 - 100%)
Which will be estimated automatically by Flink while user will be able to override/provide better estimation.
Piotrek
> On 5 Jun 2019, at 05:42, Becket Qin <be...@gmail.com> wrote:
>
> Hi Piotr,
>
> Thanks for the explanation. Please see some clarifications below.
>
> By time-based metric, I meant the portion of time spent on producing the
> record to downstream. For example, a source connector can report that it's
> spending 80% of time to emit record to downstream processing pipeline. In
> another case, a sink connector may report that its spending 30% of time
> producing the records to the external system.
>
> This is in some sense equivalent to the buffer usage metric:
> - 80% of time spent on emitting records to downstream ---> downstream
> node is bottleneck ---> output buffer is probably full.
> - 30% of time spent on emitting records to downstream ---> downstream
> node is not bottleneck ---> output buffer is probably not full.
>
> However, the time-based metric has a few advantages that the buffer usage
> metric may not have.
>
> 1. Buffer usage metric may not be applicable to all the connector
> implementations, while reporting time-based metric are always doable.
> Some source connectors may not have any input buffer, or they may use some
> third party library that does not expose the input buffer at all.
> Similarly, for sink connectors, the implementation may not have any output
> buffer, or the third party library does not expose such buffer.
>
> 2. Although both type of metrics can detect bottleneck, time-based metrics
> can be used to generate a more informed action to remove the bottleneck.
> For example, when the downstream is bottleneck, the output buffer usage
> metric is likely to be 100%, and the input buffer usage might be 0%. That
> means we don't know what is the suitable parallelism to lift the
> bottleneck. The time-based metric, on the other hand, would give useful
> information, e.g. if 80% of time was spent on emitting records, we can
> roughly increase the downstream node parallelism by 4 times.
>
> Admittedly, the time-based metrics are more expensive than buffer usage. So
> we may have to do some sampling to reduce the cost. But in general, using
> time-based metrics seems worth adding.
>
> That being said, I don't think buffer usage metric and time-based metrics
> are mutually exclusive. We can probably have both. It is just that in
> practice, features like auto-scaling might prefer time-based metrics for
> the reason stated above.
>
>> 1. Define the metrics that would allow us to manually detect bottlenecks.
> As I wrote, we already have them in most of the places, except of
> sources/sinks.
>> 2. Use those metrics, to automatically detect bottlenecks. Currently we
> are only automatically detecting back pressure and reporting it to the user
> in web UI (is it exposed as a metric at all?). Detecting the root cause of
> the back pressure (bottleneck) is one step further.
>> 3. Use the knowledge about where exactly the bottleneck is located, to
> try to do something with it.
>
> As explained above, I think time-based metric also addresses item 1 and
> item 2.
>
> Any thoughts？
>
> Thanks,
>
> Jiangjie (Becket) Qin
>
>
>
> On Mon, Jun 3, 2019 at 4:14 PM Piotr Nowojski <pi...@ververica.com> wrote:
>
>> Hi again :)
>>
>>> - pending.bytes, Gauge
>>> - pending.messages, Gauge
>>
>>
>> +1
>>
>> And true, instead of overloading one of the metric it is better when user
>> can choose to provide only one of them.
>>
>> Re 2:
>>
>>> If I understand correctly, this metric along with the pending mesages /
>>> bytes would answer the questions of:
>>
>>> - Does the connector consume fast enough? Lagging behind + empty buffer
>> =
>>> cannot consume fast enough.
>>> - Does the connector emit fast enough? Lagging behind + full buffer =
>>> cannot emit fast enough, i.e. the Flink pipeline is slow.
>>
>> Yes, exactly. This can also be used to support decisions like changing the
>> parallelism of the sources and/or down stream operators.
>>
>> I’m not sure if I understand your proposal with time based measurements.
>> Maybe I’m missing something, but I do not see how measuring time alone
>> could answer the problem: where is the bottleneck. Time spent on the
>> next/emit might be short or long (depending on how heavy to process the
>> record is) and the source can still be bottlenecked/back pressured or not.
>> Usually the easiest and the most reliable way how to detect bottlenecks is
>> by checking usage of input & output buffers, since when input buffer is
>> full while output buffer is empty, that’s the definition of a bottleneck.
>> Also this is usually very easy and cheap to measure (it works effectively
>> the same way as current’s Flink back pressure monitoring, but more cleanly,
>> without probing thread’s stack traces).
>>
>> Also keep in mind that we are already using the buffer usage metrics for
>> detecting the bottlenecks in Flink’s internal network exchanges (manual
>> work). That’s the reason why I wanted to extend this to sources/sinks,
>> since they are currently our blind spot.
>>
>>> One feature we are currently working on to scale Flink automatically
>> relies
>>> on some metrics answering the same question
>>
>> That would be very helpful feature. I think in order to achieve that we
>> would need to:
>> 1. Define the metrics that would allow us to manually detect bottlenecks.
>> As I wrote, we already have them in most of the places, except of
>> sources/sinks.
>> 2. Use those metrics, to automatically detect bottlenecks. Currently we
>> are only automatically detecting back pressure and reporting it to the user
>> in web UI (is it exposed as a metric at all?). Detecting the root cause of
>> the back pressure (bottleneck) is one step further.
>> 3. Use the knowledge about where exactly the bottleneck is located, to try
>> to do something with it.
>>
>> I think you are aiming for point 3., but before we reach it, we are still
>> missing 1. & 2. Also even if we have 3., there is a value in 1 & 2 for
>> manual analysis/dashboards.
>>
>> However, having the knowledge of where the bottleneck is, doesn’t
>> necessarily mean that we know what we can do about it. For example
>> increasing parallelism might or might not help with anything (data skew,
>> bottleneck on some resource that does not scale), but this remark applies
>> always, regardless of the way how did we detect the bottleneck.
>>
>> Piotrek
>>
>>> On 3 Jun 2019, at 06:16, Becket Qin <be...@gmail.com> wrote:
>>>
>>> Hi Piotr,
>>>
>>> Thanks for the suggestion. Some thoughts below:
>>>
>>> Re 1: The pending messages / bytes.
>>> I completely agree these are very useful metrics and we should expect the
>>> connector to report. WRT the way to expose them, it seems more consistent
>>> to add two metrics instead of adding a method (unless there are other use
>>> cases other than metric reporting). So we can add the following two
>> metrics.
>>> - pending.bytes, Gauge
>>> - pending.messages, Gauge
>>> Applicable connectors can choose to report them. These two metrics along
>>> with latency should be sufficient for users to understand the progress
>> of a
>>> connector.
>>>
>>>
>>> Re 2: Number of buffered data in-memory of the connector
>>> If I understand correctly, this metric along with the pending mesages /
>>> bytes would answer the questions of:
>>> - Does the connector consume fast enough? Lagging behind + empty buffer
>> =
>>> cannot consume fast enough.
>>> - Does the connector emit fast enough? Lagging behind + full buffer =
>>> cannot emit fast enough, i.e. the Flink pipeline is slow.
>>>
>>> One feature we are currently working on to scale Flink automatically
>> relies
>>> on some metrics answering the same question, more specifically, we are
>>> profiling the time spent on .next() method (time to consume) and the time
>>> spent on .collect() method (time to emit / process). One advantage of
>> such
>>> method level time cost allows us to calculate the parallelism required to
>>> keep up in case their is a lag.
>>>
>>> However, one concern I have regarding such metric is that they are
>>> implementation specific. Either profiling on the method time, or
>> reporting
>>> buffer usage assumes the connector are implemented in such a way. A
>>> slightly better solution might be have the following metric:
>>>
>>> - EmitTimeRatio (or FetchTimeRatio): The time spent on emitting
>>> records / Total time elapsed.
>>>
>>> This assumes that the source connectors have to emit the records to the
>>> downstream at some point. The emission may take some time ( e.g. go
>> through
>>> chained operators). And the rest of the time are spent to prepare the
>>> record to emit, including time for consuming and format conversion, etc.
>>> Ideally, we'd like to see the time spent on record fetch and emit to be
>>> about the same, so no one is bottleneck for the other.
>>>
>>> The downside of these time based metrics is additional overhead to get
>> the
>>> time, therefore sampling might be needed. But in practice I feel such
>> time
>>> based metric might be more useful if we want to take action.
>>>
>>>
>>> I think we should absolutely add metrics in (1) to the metric convention.
>>> We could also add the metrics mentioned in (2) if we reach consensus on
>>> that. What do you think?
>>>
>>> Thanks,
>>>
>>> Jiangjie (Becket) Qin
>>>
>>>
>>> On Fri, May 31, 2019 at 4:26 PM Piotr Nowojski <pi...@ververica.com>
>> wrote:
>>>
>>>> Hey Becket,
>>>>
>>>> Re 1a) and 1b) +1 from my side.
>>>>
>>>> I’ve discussed this issue:
>>>>
>>>>>>>
>>>>>>> 2. It would be nice to have metrics, that allow us to check the cause
>>>> of
>>>>>>> back pressure:
>>>>>>> a) for sources, length of input queue (in bytes? Or boolean
>>>>>>> hasSomethingl/isEmpty)
>>>>>>> b) for sinks, length of output queue (in bytes? Or boolean
>>>>>>> hasSomething/isEmpty)
>>>>
>>>> With Nico at some lengths and he also saw the benefits of them. We also
>>>> have more concrete proposal for that.
>>>>
>>>> Actually there are two really useful metrics, that we are missing
>>>> currently:
>>>>
>>>> 1. Number of data/records/bytes in the backlog to process. For example
>>>> remaining number of bytes in unread files. Or pending data in Kafka
>> topics.
>>>> 2. Number of buffered data in-memory of the connector, that are waiting
>> to
>>>> be processed pushed to Flink pipeline.
>>>>
>>>> Re 1:
>>>> This would have to be a metric provided directly by a connector. It
>> could
>>>> be an undefined `int`:
>>>>
>>>> `int backlog` - estimate of pending work.
>>>>
>>>> “Undefined” meaning that it would be up to a connector to decided
>> whether
>>>> it’s measured in bytes, records, pending files or whatever it is
>> possible
>>>> to provide by the connector. This is because I assume not every
>> connector
>>>> can provide exact number and for some of them it might be impossible to
>>>> provide records number of bytes count.
>>>>
>>>> Re 2:
>>>> This metric could be either provided by a connector, or calculated
>> crudely
>>>> by Flink:
>>>>
>>>> `float bufferUsage` - value from [0.0, 1.0] range
>>>>
>>>> Percentage of used in memory buffers, like in Kafka’s handover.
>>>>
>>>> It could be crudely implemented by Flink with FLIP-27
>>>> SourceReader#isAvailable. If SourceReader is not available reported
>>>> `bufferUsage` could be 0.0. If it is available, it could be 1.0. I think
>>>> this would be a good enough estimation for most of the use cases (that
>>>> could be overloaded and implemented better if desired). Especially
>> since we
>>>> are reporting only probed values: if probed values are almost always
>> “1.0”,
>>>> it would mean that we have a back pressure. If they are almost always
>>>> “0.0”, there is probably no back pressure at the sources.
>>>>
>>>> What do you think about this?
>>>>
>>>> Piotrek
>>>>
>>>>> On 30 May 2019, at 11:41, Becket Qin <be...@gmail.com> wrote:
>>>>>
>>>>> Hi all,
>>>>>
>>>>> Thanks a lot for all the feedback and comments. I'd like to continue
>> the
>>>>> discussion on this FLIP.
>>>>>
>>>>> I updated the FLIP-33 wiki to remove all the histogram metrics from the
>>>>> first version of metric convention due to the performance concern. The
>>>> plan
>>>>> is to introduce them later when we have a mechanism to opt in/out
>>>> metrics.
>>>>> At that point, users can decide whether they want to pay the cost to
>> get
>>>>> the metric or not.
>>>>>
>>>>> As Stephan suggested, for this FLIP, let's first try to agree on the
>>>> small
>>>>> list of conventional metrics that connectors should follow.
>>>>> Just to be clear, the purpose of the convention is not to enforce every
>>>>> connector to report all these metrics, but to provide a guidance in
>> case
>>>>> these metrics are reported by some connectors.
>>>>>
>>>>>
>>>>> @ Stephan & Chesnay,
>>>>>
>>>>> Regarding the duplication of `RecordsIn` metric in operator / task
>>>>> IOMetricGroups, from what I understand, for source operator, it is
>>>> actually
>>>>> the SourceFunction that reports the operator level
>>>>> RecordsIn/RecordsInPerSecond metric. So they are essentially the same
>>>>> metric in the operator level IOMetricGroup. Similarly for the Sink
>>>>> operator, the operator level RecordsOut/RecordsOutPerSecond metrics are
>>>>> also reported by the Sink function. I marked them as existing in the
>>>>> FLIP-33 wiki page. Please let me know if I misunderstood.
>>>>>
>>>>> Thanks,
>>>>>
>>>>> Jiangjie (Becket) Qin
>>>>>
>>>>>
>>>>> On Thu, May 30, 2019 at 5:16 PM Becket Qin <be...@gmail.com>
>> wrote:
>>>>>
>>>>>> Hi Piotr,
>>>>>>
>>>>>> Thanks a lot for the feedback.
>>>>>>
>>>>>> 1a) I guess you are referring to the part that "original system
>> specific
>>>>>> metrics should also be reported". The performance impact depends on
>> the
>>>>>> implementation. An efficient implementation would only record the
>> metric
>>>>>> once, but report them with two different metric names. This is
>> unlikely
>>>> to
>>>>>> hurt performance.
>>>>>>
>>>>>> 1b) Yes, I agree that we should avoid adding overhead to the critical
>>>> path
>>>>>> by all means. This is sometimes a tradeoff, running blindly without
>> any
>>>>>> metric gives best performance, but sometimes might be frustrating when
>>>> we
>>>>>> debug some issues.
>>>>>>
>>>>>> 2. The metrics are indeed very useful. Are they supposed to be
>> reported
>>>> by
>>>>>> the connectors or Flink itself? At this point FLIP-33 is more focused
>> on
>>>>>> provide a guidance to the connector authors on the metrics reporting.
>>>> That
>>>>>> said, after FLIP-27, I think we should absolutely report these metrics
>>>> in
>>>>>> the abstract implementation. In any case, the metric convention in
>> this
>>>>>> list are expected to evolve over time.
>>>>>>
>>>>>> Thanks,
>>>>>>
>>>>>> Jiangjie (Becket) Qin
>>>>>>
>>>>>> On Tue, May 28, 2019 at 6:24 PM Piotr Nowojski <pi...@ververica.com>
>>>>>> wrote:
>>>>>>
>>>>>>> Hi,
>>>>>>>
>>>>>>> Thanks for the proposal and driving the effort here Becket :) I’ve
>> read
>>>>>>> through the FLIP-33 [1], and here are couple of my thoughts.
>>>>>>>
>>>>>>> Big +1 for standardising the metric names between connectors, it will
>>>>>>> definitely help us and users a lot.
>>>>>>>
>>>>>>> Issues/questions/things to discuss that I’ve thought of:
>>>>>>>
>>>>>>> 1a. If we are about to duplicate some metrics, can this become a
>>>>>>> performance issue?
>>>>>>> 1b. Generally speaking, we should make sure that collecting those
>>>> metrics
>>>>>>> is as non intrusive as possible, especially that they will need to be
>>>>>>> updated once per record. (They might be collected more rarely with
>> some
>>>>>>> overhead, but the hot path of updating it per record will need to be
>> as
>>>>>>> quick as possible). That includes both avoiding heavy computation on
>>>> per
>>>>>>> record path: histograms?, measuring time for time based metrics (per
>>>>>>> second) (System.currentTimeMillis() depending on the implementation
>> can
>>>>>>> invoke a system call)
>>>>>>>
>>>>>>> 2. It would be nice to have metrics, that allow us to check the cause
>>>> of
>>>>>>> back pressure:
>>>>>>> a) for sources, length of input queue (in bytes? Or boolean
>>>>>>> hasSomethingl/isEmpty)
>>>>>>> b) for sinks, length of output queue (in bytes? Or boolean
>>>>>>> hasSomething/isEmpty)
>>>>>>>
>>>>>>> a) is useful in a scenario when we are processing backlog of records,
>>>> all
>>>>>>> of the internal Flink’s input/output network buffers are empty, and
>> we
>>>> want
>>>>>>> to check whether the external source system is the bottleneck
>> (source’s
>>>>>>> input queue will be empty), or if the Flink’s connector is the
>>>> bottleneck
>>>>>>> (source’s input queues will be full).
>>>>>>> b) similar story. Backlog of records, but this time all of the
>> internal
>>>>>>> Flink’s input/ouput network buffers are full, and we want o check
>>>> whether
>>>>>>> the external sink system is the bottleneck (sink output queues are
>>>> full),
>>>>>>> or if the Flink’s connector is the bottleneck (sink’s output queues
>>>> will be
>>>>>>> empty)
>>>>>>>
>>>>>>> It might be sometimes difficult to provide those metrics, so they
>> could
>>>>>>> be optional, but if we could provide them, it would be really
>> helpful.
>>>>>>>
>>>>>>> Piotrek
>>>>>>>
>>>>>>> [1]
>>>>>>>
>>>>
>> https://cwiki.apache.org/confluence/display/FLINK/FLIP-33:+Standardize+Connector+Metrics
>>>>>>> <
>>>>>>>
>>>>
>> https://cwiki.apache.org/confluence/display/FLINK/FLIP-33:+Standardize+Connector+Metrics
>>>>>>>>
>>>>>>>
>>>>>>>> On 24 Apr 2019, at 13:28, Stephan Ewen <se...@apache.org> wrote:
>>>>>>>>
>>>>>>>> I think this sounds reasonable.
>>>>>>>>
>>>>>>>> Let's keep the "reconfiguration without stopping the job" out of
>> this,
>>>>>>>> because that would be a super big effort and if we approach that,
>> then
>>>>>>> in
>>>>>>>> more generic way rather than specific to connector metrics.
>>>>>>>>
>>>>>>>> I would suggest to look at the following things before starting with
>>>> any
>>>>>>>> implementation work:
>>>>>>>>
>>>>>>>> - Try and find a committer to support this, otherwise it will be
>> hard
>>>>>>> to
>>>>>>>> make progress
>>>>>>>> - Start with defining a smaller set of "core metrics" and extend the
>>>>>>> set
>>>>>>>> later. I think that is easier than now blocking on reaching
>> consensus
>>>>>>> on a
>>>>>>>> large group of metrics.
>>>>>>>> - Find a solution to the problem Chesnay mentioned, that the
>> "records
>>>>>>> in"
>>>>>>>> metric is somehow overloaded and exists already in the IO Metric
>>>> group.
>>>>>>>>
>>>>>>>>
>>>>>>>> On Mon, Mar 25, 2019 at 7:16 AM Becket Qin <be...@gmail.com>
>>>>>>> wrote:
>>>>>>>>
>>>>>>>>> Hi Stephan,
>>>>>>>>>
>>>>>>>>> Thanks a lot for the feedback. All makes sense.
>>>>>>>>>
>>>>>>>>> It is a good suggestion to simply have an onRecord(numBytes,
>>>> eventTime)
>>>>>>>>> method for connector writers. It should meet most of the
>>>> requirements,
>>>>>>>>> individual
>>>>>>>>>
>>>>>>>>> The configurable metrics feature is something really useful,
>>>>>>> especially if
>>>>>>>>> we can somehow make it dynamically configurable without stopping
>> the
>>>>>>> jobs.
>>>>>>>>> It might be better to make it a separate discussion because it is a
>>>>>>> more
>>>>>>>>> generic feature instead of only for connectors.
>>>>>>>>>
>>>>>>>>> So in order to make some progress, in this FLIP we can limit the
>>>>>>> discussion
>>>>>>>>> scope to the connector related items:
>>>>>>>>>
>>>>>>>>> - the standard connector metric names and types.
>>>>>>>>> - the abstract ConnectorMetricHandler interface
>>>>>>>>>
>>>>>>>>> I'll start a separate thread to discuss other general metric
>> related
>>>>>>>>> enhancement items including:
>>>>>>>>>
>>>>>>>>> - optional metrics
>>>>>>>>> - dynamic metric configuration
>>>>>>>>> - potential combination with rate limiter
>>>>>>>>>
>>>>>>>>> Does this plan sound reasonable?
>>>>>>>>>
>>>>>>>>> Thanks,
>>>>>>>>>
>>>>>>>>> Jiangjie (Becket) Qin
>>>>>>>>>
>>>>>>>>> On Sat, Mar 23, 2019 at 5:53 AM Stephan Ewen <se...@apache.org>
>>>> wrote:
>>>>>>>>>
>>>>>>>>>> Ignoring for a moment implementation details, this connector
>> metrics
>>>>>>> work
>>>>>>>>>> is a really good thing to do, in my opinion
>>>>>>>>>>
>>>>>>>>>> The questions "oh, my job seems to be doing nothing, I am looking
>> at
>>>>>>> the
>>>>>>>>> UI
>>>>>>>>>> and the 'records in' value is still zero" is in the top three
>>>> support
>>>>>>>>>> questions I have been asked personally.
>>>>>>>>>> Introspection into "how far is the consumer lagging behind" (event
>>>>>>> time
>>>>>>>>>> fetch latency) came up many times as well.
>>>>>>>>>>
>>>>>>>>>> So big +1 to solving this problem.
>>>>>>>>>>
>>>>>>>>>> About the exact design - I would try to go for the following
>>>>>>> properties:
>>>>>>>>>>
>>>>>>>>>> - keep complexity of of connectors. Ideally the metrics handler
>> has
>>>> a
>>>>>>>>>> single onRecord(numBytes, eventTime) method or so, and everything
>>>>>>> else is
>>>>>>>>>> internal to the handler. That makes it dead simple for the
>>>> connector.
>>>>>>> We
>>>>>>>>>> can also think of an extensive scheme for connector specific
>>>> metrics.
>>>>>>>>>>
>>>>>>>>>> - make it configurable on the job it cluster level which metrics
>> the
>>>>>>>>>> handler internally creates when that method is invoked.
>>>>>>>>>>
>>>>>>>>>> What do you think?
>>>>>>>>>>
>>>>>>>>>> Best,
>>>>>>>>>> Stephan
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>> On Thu, Mar 21, 2019 at 10:42 AM Chesnay Schepler <
>>>> chesnay@apache.org
>>>>>>>>
>>>>>>>>>> wrote:
>>>>>>>>>>
>>>>>>>>>>> As I said before, I believe this to be over-engineered and have
>> no
>>>>>>>>>>> interest in this implementation.
>>>>>>>>>>>
>>>>>>>>>>> There are conceptual issues like defining a duplicate
>>>>>>>>> numBytesIn(PerSec)
>>>>>>>>>>> metric that already exists for each operator.
>>>>>>>>>>>
>>>>>>>>>>> On 21.03.2019 06:13, Becket Qin wrote:
>>>>>>>>>>>> A few updates to the thread. I uploaded a patch[1] as a complete
>>>>>>>>>>>> example of how users can use the metrics in the future.
>>>>>>>>>>>>
>>>>>>>>>>>> Some thoughts below after taking a look at the
>> AbstractMetricGroup
>>>>>>>>> and
>>>>>>>>>>>> its subclasses.
>>>>>>>>>>>>
>>>>>>>>>>>> This patch intends to provide convenience for Flink connector
>>>>>>>>>>>> implementations to follow metrics standards proposed in FLIP-33.
>>>> It
>>>>>>>>>>>> also try to enhance the metric management in general way to help
>>>>>>>>> users
>>>>>>>>>>>> with:
>>>>>>>>>>>>
>>>>>>>>>>>> 1. metric definition
>>>>>>>>>>>> 2. metric dependencies check
>>>>>>>>>>>> 3. metric validation
>>>>>>>>>>>> 4. metric control (turn on / off particular metrics)
>>>>>>>>>>>>
>>>>>>>>>>>> This patch wraps |MetricGroup| to extend the functionality of
>>>>>>>>>>>> |AbstractMetricGroup| and its subclasses. The
>>>>>>>>>>>> |AbstractMetricGroup| mainly focus on the metric group
>> hierarchy,
>>>>>>> but
>>>>>>>>>>>> does not really manage the metrics other than keeping them in a
>>>> Map.
>>>>>>>>>>>>
>>>>>>>>>>>> Ideally we should only have one entry point for the metrics.
>>>>>>>>>>>>
>>>>>>>>>>>> Right now the entry point is |AbstractMetricGroup|. However,
>>>> besides
>>>>>>>>>>>> the missing functionality mentioned above, |AbstractMetricGroup|
>>>>>>>>> seems
>>>>>>>>>>>> deeply rooted in Flink runtime. We could extract it out to
>>>>>>>>>>>> flink-metrics in order to use it for generic purpose. There will
>>>> be
>>>>>>>>>>>> some work, though.
>>>>>>>>>>>>
>>>>>>>>>>>> Another approach is to make |AbstractMetrics| in this patch as
>> the
>>>>>>>>>>>> metric entry point. It wraps metric group and provides the
>> missing
>>>>>>>>>>>> functionalities. Then we can roll out this pattern to runtime
>>>>>>>>>>>> components gradually as well.
>>>>>>>>>>>>
>>>>>>>>>>>> My first thought is that the latter approach gives a more smooth
>>>>>>>>>>>> migration. But I am also OK with doing a refactoring on the
>>>>>>>>>>>> |AbstractMetricGroup| family.
>>>>>>>>>>>>
>>>>>>>>>>>>
>>>>>>>>>>>> Thanks,
>>>>>>>>>>>>
>>>>>>>>>>>> Jiangjie (Becket) Qin
>>>>>>>>>>>>
>>>>>>>>>>>> [1] https://github.com/becketqin/flink/pull/1
>>>>>>>>>>>>
>>>>>>>>>>>> On Mon, Feb 25, 2019 at 2:32 PM Becket Qin <
>> becket.qin@gmail.com
>>>>>>>>>>>> <ma...@gmail.com>> wrote:
>>>>>>>>>>>>
>>>>>>>>>>>> Hi Chesnay,
>>>>>>>>>>>>
>>>>>>>>>>>> It might be easier to discuss some implementation details in
>> the
>>>>>>>>>>>> PR review instead of in the FLIP discussion thread. I have a
>>>>>>>>> patch
>>>>>>>>>>>> for Kafka connectors ready but haven't submitted the PR yet.
>>>>>>>>>>>> Hopefully that will help explain a bit more.
>>>>>>>>>>>>
>>>>>>>>>>>> ** Re: metric type binding
>>>>>>>>>>>> This is a valid point that worths discussing. If I understand
>>>>>>>>>>>> correctly, there are two points:
>>>>>>>>>>>>
>>>>>>>>>>>> 1. Metric type / interface does not matter as long as the
>> metric
>>>>>>>>>>>> semantic is clearly defined.
>>>>>>>>>>>> Conceptually speaking, I agree that as long as the metric
>>>>>>>>> semantic
>>>>>>>>>>>> is defined, metric type does not matter. To some extent, Gauge
>> /
>>>>>>>>>>>> Counter / Meter / Histogram themselves can be think of as some
>>>>>>>>>>>> well-recognized semantics, if you wish. In Flink, these metric
>>>>>>>>>>>> semantics have their associated interface classes. In practice,
>>>>>>>>>>>> such semantic to interface binding seems necessary for
>> different
>>>>>>>>>>>> components to communicate. Simply standardize the semantic of
>>>>>>>>> the
>>>>>>>>>>>> connector metrics seems not sufficient for people to build
>>>>>>>>>>>> ecosystem on top of. At the end of the day, we still need to
>>>> have
>>>>>>>>>>>> some embodiment of the metric semantics that people can program
>>>>>>>>>>>> against.
>>>>>>>>>>>>
>>>>>>>>>>>> 2. Sometimes the same metric semantic can be exposed using
>>>>>>>>>>>> different metric types / interfaces.
>>>>>>>>>>>> This is a good point. Counter and Gauge-as-a-Counter are pretty
>>>>>>>>>>>> much interchangeable. This is more of a trade-off between the
>>>>>>>>> user
>>>>>>>>>>>> experience of metric producers and consumers. The metric
>>>>>>>>> producers
>>>>>>>>>>>> want to use Counter or Gauge depending on whether the counter
>> is
>>>>>>>>>>>> already tracked in code, while ideally the metric consumers
>> only
>>>>>>>>>>>> want to see a single metric type for each metric. I am leaning
>>>>>>>>>>>> towards to make the metric producers happy, i.e. allow Gauge /
>>>>>>>>>>>> Counter metric type, and the the metric consumers handle the
>>>> type
>>>>>>>>>>>> variation. The reason is that in practice, there might be more
>>>>>>>>>>>> connector implementations than metric reporter implementations.
>>>>>>>>> We
>>>>>>>>>>>> could also provide some helper method to facilitate reading
>> from
>>>>>>>>>>>> such variable metric type.
>>>>>>>>>>>>
>>>>>>>>>>>>
>>>>>>>>>>>> Just some quick replies to the comments around implementation
>>>>>>>>>>> details.
>>>>>>>>>>>>
>>>>>>>>>>>> 4) single place where metrics are registered except
>>>>>>>>>>>> connector-specific
>>>>>>>>>>>> ones (which we can't really avoid).
>>>>>>>>>>>>
>>>>>>>>>>>> Register connector specific ones in a single place is actually
>>>>>>>>>>>> something that I want to achieve.
>>>>>>>>>>>>
>>>>>>>>>>>> 2) I'm talking about time-series databases like Prometheus.
>>>>>>>>> We
>>>>>>>>>>>> would
>>>>>>>>>>>> only have a gauge metric exposing the last
>>>> fetchTime/emitTime
>>>>>>>>>>>> that is
>>>>>>>>>>>> regularly reported to the backend (Prometheus), where a
>> user
>>>>>>>>>>>> could build
>>>>>>>>>>>> a histogram of his choosing when/if he wants it.
>>>>>>>>>>>>
>>>>>>>>>>>> Not sure if such downsampling works. As an example, if a user
>>>>>>>>>>>> complains that there are some intermittent latency spikes
>> (maybe
>>>>>>>>> a
>>>>>>>>>>>> few records in 10 seconds) in their processing system. Having a
>>>>>>>>>>>> Gauge sampling instantaneous latency seems unlikely useful.
>>>>>>>>>>>> However by looking at actual 99.9 percentile latency might
>> help.
>>>>>>>>>>>>
>>>>>>>>>>>> Thanks,
>>>>>>>>>>>>
>>>>>>>>>>>> Jiangjie (Becket) Qin
>>>>>>>>>>>>
>>>>>>>>>>>>
>>>>>>>>>>>> On Fri, Feb 22, 2019 at 9:30 PM Chesnay Schepler
>>>>>>>>>>>> <chesnay@apache.org <ma...@apache.org>> wrote:
>>>>>>>>>>>>
>>>>>>>>>>>> Re: over complication of implementation.
>>>>>>>>>>>>
>>>>>>>>>>>> I think I get understand better know what you're shooting
>>>>>>>>> for,
>>>>>>>>>>>> effectively something like the OperatorIOMetricGroup.
>>>>>>>>>>>> But still, re-define setupConnectorMetrics() to accept a
>> set
>>>>>>>>>>>> of flags
>>>>>>>>>>>> for counters/meters(ans _possibly_ histograms) along with a
>>>>>>>>>>>> set of
>>>>>>>>>>>> well-defined Optional<Gauge<?>>, and return the group.
>>>>>>>>>>>>
>>>>>>>>>>>> Solves all issues as far as i can tell:
>>>>>>>>>>>> 1) no metrics must be created manually (except Gauges,
>> which
>>>>>>>>>> are
>>>>>>>>>>>> effectively just Suppliers and you can't get around this),
>>>>>>>>>>>> 2) additional metrics can be registered on the returned
>>>>>>>>> group,
>>>>>>>>>>>> 3) see 1),
>>>>>>>>>>>> 4) single place where metrics are registered except
>>>>>>>>>>>> connector-specific
>>>>>>>>>>>> ones (which we can't really avoid).
>>>>>>>>>>>>
>>>>>>>>>>>> Re: Histogram
>>>>>>>>>>>>
>>>>>>>>>>>> 1) As an example, whether "numRecordsIn" is exposed as a
>>>>>>>>>>>> Counter or a
>>>>>>>>>>>> Gauge should be irrelevant. So far we're using the metric
>>>>>>>>> type
>>>>>>>>>>>> that is
>>>>>>>>>>>> the most convenient at exposing a given value. If there is
>>>>>>>>>>>> some backing
>>>>>>>>>>>> data-structure that we want to expose some data from we
>>>>>>>>>>>> typically opt
>>>>>>>>>>>> for a Gauge, as otherwise we're just mucking around with
>> the
>>>>>>>>>>>> Meter/Counter API to get it to match. Similarly, if we want
>>>>>>>>> to
>>>>>>>>>>>> count
>>>>>>>>>>>> something but no current count exists we typically added a
>>>>>>>>>>>> Counter.
>>>>>>>>>>>> That's why attaching semantics to metric types makes little
>>>>>>>>>>>> sense (but
>>>>>>>>>>>> unfortunately several reporters already do it); for
>>>>>>>>>>>> counters/meters
>>>>>>>>>>>> certainly, but the majority of metrics are gauges.
>>>>>>>>>>>>
>>>>>>>>>>>> 2) I'm talking about time-series databases like Prometheus.
>>>>>>>>> We
>>>>>>>>>>>> would
>>>>>>>>>>>> only have a gauge metric exposing the last
>>>> fetchTime/emitTime
>>>>>>>>>>>> that is
>>>>>>>>>>>> regularly reported to the backend (Prometheus), where a
>> user
>>>>>>>>>>>> could build
>>>>>>>>>>>> a histogram of his choosing when/if he wants it.
>>>>>>>>>>>>
>>>>>>>>>>>> On 22.02.2019 13:57, Becket Qin wrote:
>>>>>>>>>>>>> Hi Chesnay,
>>>>>>>>>>>>>
>>>>>>>>>>>>> Thanks for the explanation.
>>>>>>>>>>>>>
>>>>>>>>>>>>> ** Re: FLIP
>>>>>>>>>>>>> I might have misunderstood this, but it seems that "major
>>>>>>>>>>>> changes" are well
>>>>>>>>>>>>> defined in FLIP. The full contents is following:
>>>>>>>>>>>>> What is considered a "major change" that needs a FLIP?
>>>>>>>>>>>>>
>>>>>>>>>>>>> Any of the following should be considered a major change:
>>>>>>>>>>>>>
>>>>>>>>>>>>> - Any major new feature, subsystem, or piece of
>>>>>>>>>>>> functionality
>>>>>>>>>>>>> - *Any change that impacts the public interfaces of the
>>>>>>>>>>>> project*
>>>>>>>>>>>>>
>>>>>>>>>>>>> What are the "public interfaces" of the project?
>>>>>>>>>>>>>
>>>>>>>>>>>>>
>>>>>>>>>>>>>
>>>>>>>>>>>>> *All of the following are public interfaces *that people
>>>>>>>>>>>> build around:
>>>>>>>>>>>>>
>>>>>>>>>>>>> - DataStream and DataSet API, including classes related
>>>>>>>>>>>> to that, such as
>>>>>>>>>>>>> StreamExecutionEnvironment
>>>>>>>>>>>>>
>>>>>>>>>>>>>
>>>>>>>>>>>>> - Classes marked with the @Public annotation
>>>>>>>>>>>>>
>>>>>>>>>>>>>
>>>>>>>>>>>>> - On-disk binary formats, such as
>>>>>>>>> checkpoints/savepoints
>>>>>>>>>>>>>
>>>>>>>>>>>>>
>>>>>>>>>>>>> - User-facing scripts/command-line tools, i.e.
>>>>>>>>>>>> bin/flink, Yarn scripts,
>>>>>>>>>>>>> Mesos scripts
>>>>>>>>>>>>>
>>>>>>>>>>>>>
>>>>>>>>>>>>> - Configuration settings
>>>>>>>>>>>>>
>>>>>>>>>>>>>
>>>>>>>>>>>>> - *Exposed monitoring information*
>>>>>>>>>>>>>
>>>>>>>>>>>>>
>>>>>>>>>>>>> So any monitoring information change is considered as
>>>>>>>>> public
>>>>>>>>>>>> interface, and
>>>>>>>>>>>>> any public interface change is considered as a "major
>>>>>>>>>> change".
>>>>>>>>>>>>>
>>>>>>>>>>>>>
>>>>>>>>>>>>> ** Re: over complication of implementation.
>>>>>>>>>>>>>
>>>>>>>>>>>>> Although this is more of implementation details that is not
>>>>>>>>>>>> covered by the
>>>>>>>>>>>>> FLIP. But it may be worth discussing.
>>>>>>>>>>>>>
>>>>>>>>>>>>> First of all, I completely agree that we should use the
>>>>>>>>>>>> simplest way to
>>>>>>>>>>>>> achieve our goal. To me the goal is the following:
>>>>>>>>>>>>> 1. Clear connector conventions and interfaces.
>>>>>>>>>>>>> 2. The easiness of creating a connector.
>>>>>>>>>>>>>
>>>>>>>>>>>>> Both of them are important to the prosperity of the
>>>>>>>>>>>> connector ecosystem. So
>>>>>>>>>>>>> I'd rather abstract as much as possible on our side to make
>>>>>>>>>>>> the connector
>>>>>>>>>>>>> developer's work lighter. Given this goal, a static util
>>>>>>>>>>>> method approach
>>>>>>>>>>>>> might have a few drawbacks:
>>>>>>>>>>>>> 1. Users still have to construct the metrics by themselves.
>>>>>>>>>>>> (And note that
>>>>>>>>>>>>> this might be erroneous by itself. For example, a customer
>>>>>>>>>>>> wrapper around
>>>>>>>>>>>>> dropwizard meter maybe used instead of MeterView).
>>>>>>>>>>>>> 2. When connector specific metrics are added, it is
>>>>>>>>>>>> difficult to enforce
>>>>>>>>>>>>> the scope to be the same as standard metrics.
>>>>>>>>>>>>> 3. It seems that a method proliferation is inevitable if we
>>>>>>>>>>>> want to apply
>>>>>>>>>>>>> sanity checks. e.g. The metric of numBytesIn was not
>>>>>>>>>>>> registered for a meter.
>>>>>>>>>>>>> 4. Metrics are still defined in random places and hard to
>>>>>>>>>>> track.
>>>>>>>>>>>>>
>>>>>>>>>>>>> The current PR I had was inspired by the Config system in
>>>>>>>>>>>> Kafka, which I
>>>>>>>>>>>>> found pretty handy. In fact it is not only used by Kafka
>>>>>>>>>>>> itself but even
>>>>>>>>>>>>> some other projects that depend on Kafka. I am not saying
>>>>>>>>>>>> this approach is
>>>>>>>>>>>>> perfect. But I think it worths to save the work for
>>>>>>>>>>>> connector writers and
>>>>>>>>>>>>> encourage more systematic implementation. That being said,
>>>>>>>>> I
>>>>>>>>>>>> am fully open
>>>>>>>>>>>>> to suggestions.
>>>>>>>>>>>>>
>>>>>>>>>>>>>
>>>>>>>>>>>>> Re: Histogram
>>>>>>>>>>>>> I think there are two orthogonal questions around those
>>>>>>>>>>> metrics:
>>>>>>>>>>>>>
>>>>>>>>>>>>> 1. Regardless of the metric type, by just looking at the
>>>>>>>>>>>> meaning of a
>>>>>>>>>>>>> metric, is generic to all connectors? If the answer is yes,
>>>>>>>>>>>> we should
>>>>>>>>>>>>> include the metric into the convention. No matter whether
>>>>>>>>> we
>>>>>>>>>>>> include it
>>>>>>>>>>>>> into the convention or not, some connector implementations
>>>>>>>>>>>> will emit such
>>>>>>>>>>>>> metric. It is better to have a convention than letting each
>>>>>>>>>>>> connector do
>>>>>>>>>>>>> random things.
>>>>>>>>>>>>>
>>>>>>>>>>>>> 2. If a standard metric is a histogram, what should we do?
>>>>>>>>>>>>> I agree that we should make it clear that using histograms
>>>>>>>>>>>> will have
>>>>>>>>>>>>> performance risk. But I do see histogram is useful in some
>>>>>>>>>>>> fine-granularity
>>>>>>>>>>>>> debugging where one do not have the luxury to stop the
>>>>>>>>>>>> system and inject
>>>>>>>>>>>>> more inspection code. So the workaround I am thinking is to
>>>>>>>>>>>> provide some
>>>>>>>>>>>>> implementation suggestions. Assume later on we have a
>>>>>>>>>>>> mechanism of
>>>>>>>>>>>>> selective metrics. In the abstract metrics class we can
>>>>>>>>>>>> disable those
>>>>>>>>>>>>> metrics by default individual connector writers does not
>>>>>>>>>>>> have to do
>>>>>>>>>>>>> anything (this is another advantage of having an
>>>>>>>>>>>> AbstractMetrics instead of
>>>>>>>>>>>>> static util methods.)
>>>>>>>>>>>>>
>>>>>>>>>>>>> I am not sure I fully understand the histogram in the
>>>>>>>>>>>> backend approach. Can
>>>>>>>>>>>>> you explain a bit more? Do you mean emitting the raw data,
>>>>>>>>>>>> e.g. fetchTime
>>>>>>>>>>>>> and emitTime with each record and let the histogram
>>>>>>>>>>>> computation happen in
>>>>>>>>>>>>> the background? Or let the processing thread putting the
>>>>>>>>>>>> values into a
>>>>>>>>>>>>> queue and have a separate thread polling from the queue and
>>>>>>>>>>>> add them into
>>>>>>>>>>>>> the histogram?
>>>>>>>>>>>>>
>>>>>>>>>>>>> Thanks,
>>>>>>>>>>>>>
>>>>>>>>>>>>> Jiangjie (Becket) Qin
>>>>>>>>>>>>>
>>>>>>>>>>>>>
>>>>>>>>>>>>>
>>>>>>>>>>>>>
>>>>>>>>>>>>>
>>>>>>>>>>>>> On Fri, Feb 22, 2019 at 4:34 PM Chesnay Schepler
>>>>>>>>>>>> <chesnay@apache.org <ma...@apache.org>> wrote:
>>>>>>>>>>>>>
>>>>>>>>>>>>>> Re: Flip
>>>>>>>>>>>>>> The very first line under both the main header and Purpose
>>>>>>>>>>>> section
>>>>>>>>>>>>>> describe Flips as "major changes", which this isn't.
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> Re: complication
>>>>>>>>>>>>>> I'm not arguing against standardization, but again an
>>>>>>>>>>>> over-complicated
>>>>>>>>>>>>>> implementation when a static utility method would be
>>>>>>>>>>>> sufficient.
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> public static void setupConnectorMetrics(
>>>>>>>>>>>>>> MetricGroup operatorMetricGroup,
>>>>>>>>>>>>>> String connectorName,
>>>>>>>>>>>>>> Optional<Gauge<Long>> numRecordsIn,
>>>>>>>>>>>>>> ...)
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> This gives you all you need:
>>>>>>>>>>>>>> * a well-defined set of metrics for a connector to opt-in
>>>>>>>>>>>>>> * standardized naming schemes for scope and individual
>>>>>>>>>> metrics
>>>>>>>>>>>>>> * standardize metric types (although personally I'm not
>>>>>>>>>>>> interested in that
>>>>>>>>>>>>>> since metric types should be considered syntactic sugar)
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> Re: Configurable Histogram
>>>>>>>>>>>>>> If anything they _must_ be turned off by default, but the
>>>>>>>>>>>> metric system is
>>>>>>>>>>>>>> already exposing so many options that I'm not too keen on
>>>>>>>>>>>> adding even more.
>>>>>>>>>>>>>> You have also only addressed my first argument against
>>>>>>>>>>>> histograms
>>>>>>>>>>>>>> (performance), the second one still stands (calculate
>>>>>>>>>>>> histogram in metric
>>>>>>>>>>>>>> backends instead).
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> On 21.02.2019 16:27, Becket Qin wrote:
>>>>>>>>>>>>>>> Hi Chesnay,
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> Thanks for the comments. I think this is worthy of a FLIP
>>>>>>>>>>>> because it is
>>>>>>>>>>>>>>> public API. According to the FLIP description a FlIP is
>>>>>>>>>>>> required in case
>>>>>>>>>>>>>> of:
>>>>>>>>>>>>>>> - Any change that impacts the public interfaces of
>>>>>>>>>>>> the project
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> and the following entry is found in the definition of
>>>>>>>>>>>> "public interface".
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> - Exposed monitoring information
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> Metrics are critical to any production system. So a clear
>>>>>>>>>>>> metric
>>>>>>>>>>>>>> definition
>>>>>>>>>>>>>>> is important for any serious users. For an organization
>>>>>>>>>>>> with large Flink
>>>>>>>>>>>>>>> installation, change in metrics means great amount of
>>>>>>>>>>>> work. So such
>>>>>>>>>>>>>> changes
>>>>>>>>>>>>>>> do need to be fully discussed and documented.
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> ** Re: Histogram.
>>>>>>>>>>>>>>> We can discuss whether there is a better way to expose
>>>>>>>>>>>> metrics that are
>>>>>>>>>>>>>>> suitable for histograms. My micro-benchmark on various
>>>>>>>>>>>> histogram
>>>>>>>>>>>>>>> implementations also indicates that they are
>>>>>>>>> significantly
>>>>>>>>>>>> slower than
>>>>>>>>>>>>>>> other metric types. But I don't think that means never
>>>>>>>>> use
>>>>>>>>>>>> histogram, but
>>>>>>>>>>>>>>> means use it with caution. For example, we can suggest
>>>>>>>>> the
>>>>>>>>>>>>>> implementations
>>>>>>>>>>>>>>> to turn them off by default and only turn it on for a
>>>>>>>>>>>> small amount of
>>>>>>>>>>>>>> time
>>>>>>>>>>>>>>> when performing some micro-debugging.
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> ** Re: complication:
>>>>>>>>>>>>>>> Connector conventions are essential for Flink ecosystem.
>>>>>>>>>>>> Flink connectors
>>>>>>>>>>>>>>> pool is probably the most important part of Flink, just
>>>>>>>>>>>> like any other
>>>>>>>>>>>>>> data
>>>>>>>>>>>>>>> system. Clear conventions of connectors will help build
>>>>>>>>>>>> Flink ecosystem
>>>>>>>>>>>>>> in
>>>>>>>>>>>>>>> a more organic way.
>>>>>>>>>>>>>>> Take the metrics convention as an example, imagine
>>>>>>>>> someone
>>>>>>>>>>>> has developed
>>>>>>>>>>>>>> a
>>>>>>>>>>>>>>> Flink connector for System foo, and another developer may
>>>>>>>>>>>> have developed
>>>>>>>>>>>>>> a
>>>>>>>>>>>>>>> monitoring and diagnostic framework for Flink which
>>>>>>>>>>>> analyzes the Flink
>>>>>>>>>>>>>> job
>>>>>>>>>>>>>>> performance based on metrics. With a clear metric
>>>>>>>>>>>> convention, those two
>>>>>>>>>>>>>>> projects could be developed independently. Once users put
>>>>>>>>>>>> them together,
>>>>>>>>>>>>>>> it would work without additional modifications. This
>>>>>>>>>>>> cannot be easily
>>>>>>>>>>>>>>> achieved by just defining a few constants.
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> ** Re: selective metrics:
>>>>>>>>>>>>>>> Sure, we can discuss that in a separate thread.
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> @Dawid
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> ** Re: latency / fetchedLatency
>>>>>>>>>>>>>>> The primary purpose of establish such a convention is to
>>>>>>>>>>>> help developers
>>>>>>>>>>>>>>> write connectors in a more compatible way. The convention
>>>>>>>>>>>> is supposed to
>>>>>>>>>>>>>> be
>>>>>>>>>>>>>>> defined more proactively. So when look at the convention,
>>>>>>>>>>>> it seems more
>>>>>>>>>>>>>>> important to see if the concept is applicable to
>>>>>>>>>>>> connectors in general.
>>>>>>>>>>>>>> It
>>>>>>>>>>>>>>> might be true so far only Kafka connector reports
>>>>>>>>> latency.
>>>>>>>>>>>> But there
>>>>>>>>>>>>>> might
>>>>>>>>>>>>>>> be hundreds of other connector implementations in the
>>>>>>>>>>>> Flink ecosystem,
>>>>>>>>>>>>>>> though not in the Flink repo, and some of them also emits
>>>>>>>>>>>> latency. I
>>>>>>>>>>>>>> think
>>>>>>>>>>>>>>> a lot of other sources actually also has an append
>>>>>>>>>>>> timestamp. e.g.
>>>>>>>>>>>>>> database
>>>>>>>>>>>>>>> bin logs and some K-V stores. So I wouldn't be surprised
>>>>>>>>>>>> if some database
>>>>>>>>>>>>>>> connector can also emit latency metrics.
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> Thanks,
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> Jiangjie (Becket) Qin
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> On Thu, Feb 21, 2019 at 10:14 PM Chesnay Schepler
>>>>>>>>>>>> <chesnay@apache.org <ma...@apache.org>>
>>>>>>>>>>>>>>> wrote:
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>> Regarding 2) It doesn't make sense to investigate this
>>>>>>>>> as
>>>>>>>>>>>> part of this
>>>>>>>>>>>>>>>> FLIP. This is something that could be of interest for
>>>>>>>>> the
>>>>>>>>>>>> entire metric
>>>>>>>>>>>>>>>> system, and should be designed for as such.
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>> Regarding the proposal as a whole:
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>> Histogram metrics shall not be added to the core of
>>>>>>>>>>>> Flink. They are
>>>>>>>>>>>>>>>> significantly more expensive than other metrics, and
>>>>>>>>>>>> calculating
>>>>>>>>>>>>>>>> histograms in the application is regarded as an
>>>>>>>>>>>> anti-pattern by several
>>>>>>>>>>>>>>>> metric backends, who instead recommend to expose the raw
>>>>>>>>>>>> data and
>>>>>>>>>>>>>>>> calculate the histogram in the backend.
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>> Second, this seems overly complicated. Given that we
>>>>>>>>>>>> already established
>>>>>>>>>>>>>>>> that not all connectors will export all metrics we are
>>>>>>>>>>>> effectively
>>>>>>>>>>>>>>>> reducing this down to a consistent naming scheme. We
>>>>>>>>>>>> don't need anything
>>>>>>>>>>>>>>>> sophisticated for that; basically just a few constants
>>>>>>>>>>>> that all
>>>>>>>>>>>>>>>> connectors use.
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>> I'm not convinced that this is worthy of a FLIP.
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>> On 21.02.2019 14:26, Dawid Wysakowicz wrote:
>>>>>>>>>>>>>>>>> Hi,
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>> Ad 1. In general I undestand and I agree. But those
>>>>>>>>>>>> particular metrics
>>>>>>>>>>>>>>>>> (latency, fetchLatency), right now would only be
>>>>>>>>>>>> reported if user uses
>>>>>>>>>>>>>>>>> KafkaConsumer with internal timestampAssigner with
>>>>>>>>>>>> StreamCharacteristic
>>>>>>>>>>>>>>>>> set to EventTime, right? That sounds like a very
>>>>>>>>>>>> specific case. I am
>>>>>>>>>>>>>> not
>>>>>>>>>>>>>>>>> sure if we should introduce a generic metric that will
>>>>>>>>> be
>>>>>>>>>>>>>>>>> disabled/absent for most of implementations.
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>> Ad.2 That sounds like an orthogonal issue, that might
>>>>>>>>>>>> make sense to
>>>>>>>>>>>>>>>>> investigate in the future.
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>> Best,
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>> Dawid
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>> On 21/02/2019 13:20, Becket Qin wrote:
>>>>>>>>>>>>>>>>>> Hi Dawid,
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> Thanks for the feedback. That makes sense to me. There
>>>>>>>>>>>> are two cases
>>>>>>>>>>>>>> to
>>>>>>>>>>>>>>>> be
>>>>>>>>>>>>>>>>>> addressed.
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> 1. The metrics are supposed to be a guidance. It is
>>>>>>>>>>>> likely that a
>>>>>>>>>>>>>>>> connector
>>>>>>>>>>>>>>>>>> only supports some but not all of the metrics. In that
>>>>>>>>>>>> case, each
>>>>>>>>>>>>>>>> connector
>>>>>>>>>>>>>>>>>> implementation should have the freedom to decide which
>>>>>>>>>>>> metrics are
>>>>>>>>>>>>>>>>>> reported. For the metrics that are supported, the
>>>>>>>>>>>> guidance should be
>>>>>>>>>>>>>>>>>> followed.
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> 2. Sometimes users may want to disable certain metrics
>>>>>>>>>>>> for some reason
>>>>>>>>>>>>>>>>>> (e.g. performance / reprocessing of data). A generic
>>>>>>>>>>>> mechanism should
>>>>>>>>>>>>>> be
>>>>>>>>>>>>>>>>>> provided to allow user choose which metrics are
>>>>>>>>>>>> reported. This
>>>>>>>>>>>>>> mechanism
>>>>>>>>>>>>>>>>>> should also be honored by the connector
>>>>>>>>> implementations.
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> Does this sound reasonable to you?
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> Thanks,
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> Jiangjie (Becket) Qin
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> On Thu, Feb 21, 2019 at 4:22 PM Dawid Wysakowicz <
>>>>>>>>>>>>>>>> dwysakowicz@apache.org <ma...@apache.org>>
>>>>>>>>>>>>>>>>>> wrote:
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>> Hi,
>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>> Generally I like the idea of having a unified,
>>>>>>>>>>>> standard set of
>>>>>>>>>>>>>> metrics
>>>>>>>>>>>>>>>> for
>>>>>>>>>>>>>>>>>>> all connectors. I have some slight concerns about
>>>>>>>>>>>> fetchLatency and
>>>>>>>>>>>>>>>>>>> latency though. They are computed based on EventTime
>>>>>>>>>>>> which is not a
>>>>>>>>>>>>>>>> purely
>>>>>>>>>>>>>>>>>>> technical feature. It depends often on some business
>>>>>>>>>>>> logic, might be
>>>>>>>>>>>>>>>> absent
>>>>>>>>>>>>>>>>>>> or defined after source. Those metrics could also
>>>>>>>>>>>> behave in a weird
>>>>>>>>>>>>>>>> way in
>>>>>>>>>>>>>>>>>>> case of replaying backlog. Therefore I am not sure if
>>>>>>>>>>>> we should
>>>>>>>>>>>>>> include
>>>>>>>>>>>>>>>>>>> those metrics by default. Maybe we could at least
>>>>>>>>>>>> introduce a feature
>>>>>>>>>>>>>>>>>>> switch for them? What do you think?
>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>> Best,
>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>> Dawid
>>>>>>>>>>>>>>>>>>> On 21/02/2019 03:13, Becket Qin wrote:
>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>> Bump. If there is no objections to the proposed
>>>>>>>>>>>> metrics. I'll start a
>>>>>>>>>>>>>>>>>>> voting thread later toady.
>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>> Thanks,
>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>> Jiangjie (Becket) Qin
>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>> On Mon, Feb 11, 2019 at 8:17 PM Becket Qin
>>>>>>>>>>>> <becket.qin@gmail.com <ma...@gmail.com>> <
>>>>>>>>>>>>>>>> becket.qin@gmail.com <ma...@gmail.com>>
>>>>>>>>>> wrote:
>>>>>>>>>>>>>>>>>>> Hi folks,
>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>> I would like to start the FLIP discussion thread
>>>>>>>>> about
>>>>>>>>>>>> standardize
>>>>>>>>>>>>>> the
>>>>>>>>>>>>>>>>>>> connector metrics.
>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>> In short, we would like to provide a convention of
>>>>>>>>>>>> Flink connector
>>>>>>>>>>>>>>>>>>> metrics. It will help simplify the monitoring and
>>>>>>>>>>>> alerting on Flink
>>>>>>>>>>>>>>>> jobs.
>>>>>>>>>>>>>>>>>>> The FLIP link is following:
>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>
>>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>
>>>>>>>
>>>>
>> https://cwiki.apache.org/confluence/display/FLINK/FLIP-33%3A+Standardize+Connector+Metrics
>>>>>>>>>>>>>>>>>>> Thanks,
>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>> Jiangjie (Becket) Qin
>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>
>>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>
>>>>>>>
>>>>>>>
>>>>
>>>>
>>>>
>>
>>
>>
Re: [DISCUSS] FLIP-33: Standardize connector metrics
Posted by Becket Qin <be...@gmail.com>.
Hi Piotr,
Thanks for the explanation. Please see some clarifications below.
By time-based metric, I meant the portion of time spent on producing the
record to downstream. For example, a source connector can report that it's
spending 80% of time to emit record to downstream processing pipeline. In
another case, a sink connector may report that its spending 30% of time
producing the records to the external system.
This is in some sense equivalent to the buffer usage metric:
- 80% of time spent on emitting records to downstream ---> downstream
node is bottleneck ---> output buffer is probably full.
- 30% of time spent on emitting records to downstream ---> downstream
node is not bottleneck ---> output buffer is probably not full.
However, the time-based metric has a few advantages that the buffer usage
metric may not have.
1. Buffer usage metric may not be applicable to all the connector
implementations, while reporting time-based metric are always doable.
Some source connectors may not have any input buffer, or they may use some
third party library that does not expose the input buffer at all.
Similarly, for sink connectors, the implementation may not have any output
buffer, or the third party library does not expose such buffer.
2. Although both type of metrics can detect bottleneck, time-based metrics
can be used to generate a more informed action to remove the bottleneck.
For example, when the downstream is bottleneck, the output buffer usage
metric is likely to be 100%, and the input buffer usage might be 0%. That
means we don't know what is the suitable parallelism to lift the
bottleneck. The time-based metric, on the other hand, would give useful
information, e.g. if 80% of time was spent on emitting records, we can
roughly increase the downstream node parallelism by 4 times.
Admittedly, the time-based metrics are more expensive than buffer usage. So
we may have to do some sampling to reduce the cost. But in general, using
time-based metrics seems worth adding.
That being said, I don't think buffer usage metric and time-based metrics
are mutually exclusive. We can probably have both. It is just that in
practice, features like auto-scaling might prefer time-based metrics for
the reason stated above.
> 1. Define the metrics that would allow us to manually detect bottlenecks.
As I wrote, we already have them in most of the places, except of
sources/sinks.
> 2. Use those metrics, to automatically detect bottlenecks. Currently we
are only automatically detecting back pressure and reporting it to the user
in web UI (is it exposed as a metric at all?). Detecting the root cause of
the back pressure (bottleneck) is one step further.
> 3. Use the knowledge about where exactly the bottleneck is located, to
try to do something with it.
As explained above, I think time-based metric also addresses item 1 and
item 2.
Any thoughts？
Thanks,
Jiangjie (Becket) Qin
On Mon, Jun 3, 2019 at 4:14 PM Piotr Nowojski <pi...@ververica.com> wrote:
> Hi again :)
>
> > - pending.bytes, Gauge
> > - pending.messages, Gauge
>
>
> +1
>
> And true, instead of overloading one of the metric it is better when user
> can choose to provide only one of them.
>
> Re 2:
>
> > If I understand correctly, this metric along with the pending mesages /
> > bytes would answer the questions of:
>
> > - Does the connector consume fast enough? Lagging behind + empty buffer
> =
> > cannot consume fast enough.
> > - Does the connector emit fast enough? Lagging behind + full buffer =
> > cannot emit fast enough, i.e. the Flink pipeline is slow.
>
> Yes, exactly. This can also be used to support decisions like changing the
> parallelism of the sources and/or down stream operators.
>
> I’m not sure if I understand your proposal with time based measurements.
> Maybe I’m missing something, but I do not see how measuring time alone
> could answer the problem: where is the bottleneck. Time spent on the
> next/emit might be short or long (depending on how heavy to process the
> record is) and the source can still be bottlenecked/back pressured or not.
> Usually the easiest and the most reliable way how to detect bottlenecks is
> by checking usage of input & output buffers, since when input buffer is
> full while output buffer is empty, that’s the definition of a bottleneck.
> Also this is usually very easy and cheap to measure (it works effectively
> the same way as current’s Flink back pressure monitoring, but more cleanly,
> without probing thread’s stack traces).
>
> Also keep in mind that we are already using the buffer usage metrics for
> detecting the bottlenecks in Flink’s internal network exchanges (manual
> work). That’s the reason why I wanted to extend this to sources/sinks,
> since they are currently our blind spot.
>
> > One feature we are currently working on to scale Flink automatically
> relies
> > on some metrics answering the same question
>
> That would be very helpful feature. I think in order to achieve that we
> would need to:
> 1. Define the metrics that would allow us to manually detect bottlenecks.
> As I wrote, we already have them in most of the places, except of
> sources/sinks.
> 2. Use those metrics, to automatically detect bottlenecks. Currently we
> are only automatically detecting back pressure and reporting it to the user
> in web UI (is it exposed as a metric at all?). Detecting the root cause of
> the back pressure (bottleneck) is one step further.
> 3. Use the knowledge about where exactly the bottleneck is located, to try
> to do something with it.
>
> I think you are aiming for point 3., but before we reach it, we are still
> missing 1. & 2. Also even if we have 3., there is a value in 1 & 2 for
> manual analysis/dashboards.
>
> However, having the knowledge of where the bottleneck is, doesn’t
> necessarily mean that we know what we can do about it. For example
> increasing parallelism might or might not help with anything (data skew,
> bottleneck on some resource that does not scale), but this remark applies
> always, regardless of the way how did we detect the bottleneck.
>
> Piotrek
>
> > On 3 Jun 2019, at 06:16, Becket Qin <be...@gmail.com> wrote:
> >
> > Hi Piotr,
> >
> > Thanks for the suggestion. Some thoughts below:
> >
> > Re 1: The pending messages / bytes.
> > I completely agree these are very useful metrics and we should expect the
> > connector to report. WRT the way to expose them, it seems more consistent
> > to add two metrics instead of adding a method (unless there are other use
> > cases other than metric reporting). So we can add the following two
> metrics.
> > - pending.bytes, Gauge
> > - pending.messages, Gauge
> > Applicable connectors can choose to report them. These two metrics along
> > with latency should be sufficient for users to understand the progress
> of a
> > connector.
> >
> >
> > Re 2: Number of buffered data in-memory of the connector
> > If I understand correctly, this metric along with the pending mesages /
> > bytes would answer the questions of:
> > - Does the connector consume fast enough? Lagging behind + empty buffer
> =
> > cannot consume fast enough.
> > - Does the connector emit fast enough? Lagging behind + full buffer =
> > cannot emit fast enough, i.e. the Flink pipeline is slow.
> >
> > One feature we are currently working on to scale Flink automatically
> relies
> > on some metrics answering the same question, more specifically, we are
> > profiling the time spent on .next() method (time to consume) and the time
> > spent on .collect() method (time to emit / process). One advantage of
> such
> > method level time cost allows us to calculate the parallelism required to
> > keep up in case their is a lag.
> >
> > However, one concern I have regarding such metric is that they are
> > implementation specific. Either profiling on the method time, or
> reporting
> > buffer usage assumes the connector are implemented in such a way. A
> > slightly better solution might be have the following metric:
> >
> > - EmitTimeRatio (or FetchTimeRatio): The time spent on emitting
> > records / Total time elapsed.
> >
> > This assumes that the source connectors have to emit the records to the
> > downstream at some point. The emission may take some time ( e.g. go
> through
> > chained operators). And the rest of the time are spent to prepare the
> > record to emit, including time for consuming and format conversion, etc.
> > Ideally, we'd like to see the time spent on record fetch and emit to be
> > about the same, so no one is bottleneck for the other.
> >
> > The downside of these time based metrics is additional overhead to get
> the
> > time, therefore sampling might be needed. But in practice I feel such
> time
> > based metric might be more useful if we want to take action.
> >
> >
> > I think we should absolutely add metrics in (1) to the metric convention.
> > We could also add the metrics mentioned in (2) if we reach consensus on
> > that. What do you think?
> >
> > Thanks,
> >
> > Jiangjie (Becket) Qin
> >
> >
> > On Fri, May 31, 2019 at 4:26 PM Piotr Nowojski <pi...@ververica.com>
> wrote:
> >
> >> Hey Becket,
> >>
> >> Re 1a) and 1b) +1 from my side.
> >>
> >> I’ve discussed this issue:
> >>
> >>>>>
> >>>>> 2. It would be nice to have metrics, that allow us to check the cause
> >> of
> >>>>> back pressure:
> >>>>> a) for sources, length of input queue (in bytes? Or boolean
> >>>>> hasSomethingl/isEmpty)
> >>>>> b) for sinks, length of output queue (in bytes? Or boolean
> >>>>> hasSomething/isEmpty)
> >>
> >> With Nico at some lengths and he also saw the benefits of them. We also
> >> have more concrete proposal for that.
> >>
> >> Actually there are two really useful metrics, that we are missing
> >> currently:
> >>
> >> 1. Number of data/records/bytes in the backlog to process. For example
> >> remaining number of bytes in unread files. Or pending data in Kafka
> topics.
> >> 2. Number of buffered data in-memory of the connector, that are waiting
> to
> >> be processed pushed to Flink pipeline.
> >>
> >> Re 1:
> >> This would have to be a metric provided directly by a connector. It
> could
> >> be an undefined `int`:
> >>
> >> `int backlog` - estimate of pending work.
> >>
> >> “Undefined” meaning that it would be up to a connector to decided
> whether
> >> it’s measured in bytes, records, pending files or whatever it is
> possible
> >> to provide by the connector. This is because I assume not every
> connector
> >> can provide exact number and for some of them it might be impossible to
> >> provide records number of bytes count.
> >>
> >> Re 2:
> >> This metric could be either provided by a connector, or calculated
> crudely
> >> by Flink:
> >>
> >> `float bufferUsage` - value from [0.0, 1.0] range
> >>
> >> Percentage of used in memory buffers, like in Kafka’s handover.
> >>
> >> It could be crudely implemented by Flink with FLIP-27
> >> SourceReader#isAvailable. If SourceReader is not available reported
> >> `bufferUsage` could be 0.0. If it is available, it could be 1.0. I think
> >> this would be a good enough estimation for most of the use cases (that
> >> could be overloaded and implemented better if desired). Especially
> since we
> >> are reporting only probed values: if probed values are almost always
> “1.0”,
> >> it would mean that we have a back pressure. If they are almost always
> >> “0.0”, there is probably no back pressure at the sources.
> >>
> >> What do you think about this?
> >>
> >> Piotrek
> >>
> >>> On 30 May 2019, at 11:41, Becket Qin <be...@gmail.com> wrote:
> >>>
> >>> Hi all,
> >>>
> >>> Thanks a lot for all the feedback and comments. I'd like to continue
> the
> >>> discussion on this FLIP.
> >>>
> >>> I updated the FLIP-33 wiki to remove all the histogram metrics from the
> >>> first version of metric convention due to the performance concern. The
> >> plan
> >>> is to introduce them later when we have a mechanism to opt in/out
> >> metrics.
> >>> At that point, users can decide whether they want to pay the cost to
> get
> >>> the metric or not.
> >>>
> >>> As Stephan suggested, for this FLIP, let's first try to agree on the
> >> small
> >>> list of conventional metrics that connectors should follow.
> >>> Just to be clear, the purpose of the convention is not to enforce every
> >>> connector to report all these metrics, but to provide a guidance in
> case
> >>> these metrics are reported by some connectors.
> >>>
> >>>
> >>> @ Stephan & Chesnay,
> >>>
> >>> Regarding the duplication of `RecordsIn` metric in operator / task
> >>> IOMetricGroups, from what I understand, for source operator, it is
> >> actually
> >>> the SourceFunction that reports the operator level
> >>> RecordsIn/RecordsInPerSecond metric. So they are essentially the same
> >>> metric in the operator level IOMetricGroup. Similarly for the Sink
> >>> operator, the operator level RecordsOut/RecordsOutPerSecond metrics are
> >>> also reported by the Sink function. I marked them as existing in the
> >>> FLIP-33 wiki page. Please let me know if I misunderstood.
> >>>
> >>> Thanks,
> >>>
> >>> Jiangjie (Becket) Qin
> >>>
> >>>
> >>> On Thu, May 30, 2019 at 5:16 PM Becket Qin <be...@gmail.com>
> wrote:
> >>>
> >>>> Hi Piotr,
> >>>>
> >>>> Thanks a lot for the feedback.
> >>>>
> >>>> 1a) I guess you are referring to the part that "original system
> specific
> >>>> metrics should also be reported". The performance impact depends on
> the
> >>>> implementation. An efficient implementation would only record the
> metric
> >>>> once, but report them with two different metric names. This is
> unlikely
> >> to
> >>>> hurt performance.
> >>>>
> >>>> 1b) Yes, I agree that we should avoid adding overhead to the critical
> >> path
> >>>> by all means. This is sometimes a tradeoff, running blindly without
> any
> >>>> metric gives best performance, but sometimes might be frustrating when
> >> we
> >>>> debug some issues.
> >>>>
> >>>> 2. The metrics are indeed very useful. Are they supposed to be
> reported
> >> by
> >>>> the connectors or Flink itself? At this point FLIP-33 is more focused
> on
> >>>> provide a guidance to the connector authors on the metrics reporting.
> >> That
> >>>> said, after FLIP-27, I think we should absolutely report these metrics
> >> in
> >>>> the abstract implementation. In any case, the metric convention in
> this
> >>>> list are expected to evolve over time.
> >>>>
> >>>> Thanks,
> >>>>
> >>>> Jiangjie (Becket) Qin
> >>>>
> >>>> On Tue, May 28, 2019 at 6:24 PM Piotr Nowojski <pi...@ververica.com>
> >>>> wrote:
> >>>>
> >>>>> Hi,
> >>>>>
> >>>>> Thanks for the proposal and driving the effort here Becket :) I’ve
> read
> >>>>> through the FLIP-33 [1], and here are couple of my thoughts.
> >>>>>
> >>>>> Big +1 for standardising the metric names between connectors, it will
> >>>>> definitely help us and users a lot.
> >>>>>
> >>>>> Issues/questions/things to discuss that I’ve thought of:
> >>>>>
> >>>>> 1a. If we are about to duplicate some metrics, can this become a
> >>>>> performance issue?
> >>>>> 1b. Generally speaking, we should make sure that collecting those
> >> metrics
> >>>>> is as non intrusive as possible, especially that they will need to be
> >>>>> updated once per record. (They might be collected more rarely with
> some
> >>>>> overhead, but the hot path of updating it per record will need to be
> as
> >>>>> quick as possible). That includes both avoiding heavy computation on
> >> per
> >>>>> record path: histograms?, measuring time for time based metrics (per
> >>>>> second) (System.currentTimeMillis() depending on the implementation
> can
> >>>>> invoke a system call)
> >>>>>
> >>>>> 2. It would be nice to have metrics, that allow us to check the cause
> >> of
> >>>>> back pressure:
> >>>>> a) for sources, length of input queue (in bytes? Or boolean
> >>>>> hasSomethingl/isEmpty)
> >>>>> b) for sinks, length of output queue (in bytes? Or boolean
> >>>>> hasSomething/isEmpty)
> >>>>>
> >>>>> a) is useful in a scenario when we are processing backlog of records,
> >> all
> >>>>> of the internal Flink’s input/output network buffers are empty, and
> we
> >> want
> >>>>> to check whether the external source system is the bottleneck
> (source’s
> >>>>> input queue will be empty), or if the Flink’s connector is the
> >> bottleneck
> >>>>> (source’s input queues will be full).
> >>>>> b) similar story. Backlog of records, but this time all of the
> internal
> >>>>> Flink’s input/ouput network buffers are full, and we want o check
> >> whether
> >>>>> the external sink system is the bottleneck (sink output queues are
> >> full),
> >>>>> or if the Flink’s connector is the bottleneck (sink’s output queues
> >> will be
> >>>>> empty)
> >>>>>
> >>>>> It might be sometimes difficult to provide those metrics, so they
> could
> >>>>> be optional, but if we could provide them, it would be really
> helpful.
> >>>>>
> >>>>> Piotrek
> >>>>>
> >>>>> [1]
> >>>>>
> >>
> https://cwiki.apache.org/confluence/display/FLINK/FLIP-33:+Standardize+Connector+Metrics
> >>>>> <
> >>>>>
> >>
> https://cwiki.apache.org/confluence/display/FLINK/FLIP-33:+Standardize+Connector+Metrics
> >>>>>>
> >>>>>
> >>>>>> On 24 Apr 2019, at 13:28, Stephan Ewen <se...@apache.org> wrote:
> >>>>>>
> >>>>>> I think this sounds reasonable.
> >>>>>>
> >>>>>> Let's keep the "reconfiguration without stopping the job" out of
> this,
> >>>>>> because that would be a super big effort and if we approach that,
> then
> >>>>> in
> >>>>>> more generic way rather than specific to connector metrics.
> >>>>>>
> >>>>>> I would suggest to look at the following things before starting with
> >> any
> >>>>>> implementation work:
> >>>>>>
> >>>>>> - Try and find a committer to support this, otherwise it will be
> hard
> >>>>> to
> >>>>>> make progress
> >>>>>> - Start with defining a smaller set of "core metrics" and extend the
> >>>>> set
> >>>>>> later. I think that is easier than now blocking on reaching
> consensus
> >>>>> on a
> >>>>>> large group of metrics.
> >>>>>> - Find a solution to the problem Chesnay mentioned, that the
> "records
> >>>>> in"
> >>>>>> metric is somehow overloaded and exists already in the IO Metric
> >> group.
> >>>>>>
> >>>>>>
> >>>>>> On Mon, Mar 25, 2019 at 7:16 AM Becket Qin <be...@gmail.com>
> >>>>> wrote:
> >>>>>>
> >>>>>>> Hi Stephan,
> >>>>>>>
> >>>>>>> Thanks a lot for the feedback. All makes sense.
> >>>>>>>
> >>>>>>> It is a good suggestion to simply have an onRecord(numBytes,
> >> eventTime)
> >>>>>>> method for connector writers. It should meet most of the
> >> requirements,
> >>>>>>> individual
> >>>>>>>
> >>>>>>> The configurable metrics feature is something really useful,
> >>>>> especially if
> >>>>>>> we can somehow make it dynamically configurable without stopping
> the
> >>>>> jobs.
> >>>>>>> It might be better to make it a separate discussion because it is a
> >>>>> more
> >>>>>>> generic feature instead of only for connectors.
> >>>>>>>
> >>>>>>> So in order to make some progress, in this FLIP we can limit the
> >>>>> discussion
> >>>>>>> scope to the connector related items:
> >>>>>>>
> >>>>>>> - the standard connector metric names and types.
> >>>>>>> - the abstract ConnectorMetricHandler interface
> >>>>>>>
> >>>>>>> I'll start a separate thread to discuss other general metric
> related
> >>>>>>> enhancement items including:
> >>>>>>>
> >>>>>>> - optional metrics
> >>>>>>> - dynamic metric configuration
> >>>>>>> - potential combination with rate limiter
> >>>>>>>
> >>>>>>> Does this plan sound reasonable?
> >>>>>>>
> >>>>>>> Thanks,
> >>>>>>>
> >>>>>>> Jiangjie (Becket) Qin
> >>>>>>>
> >>>>>>> On Sat, Mar 23, 2019 at 5:53 AM Stephan Ewen <se...@apache.org>
> >> wrote:
> >>>>>>>
> >>>>>>>> Ignoring for a moment implementation details, this connector
> metrics
> >>>>> work
> >>>>>>>> is a really good thing to do, in my opinion
> >>>>>>>>
> >>>>>>>> The questions "oh, my job seems to be doing nothing, I am looking
> at
> >>>>> the
> >>>>>>> UI
> >>>>>>>> and the 'records in' value is still zero" is in the top three
> >> support
> >>>>>>>> questions I have been asked personally.
> >>>>>>>> Introspection into "how far is the consumer lagging behind" (event
> >>>>> time
> >>>>>>>> fetch latency) came up many times as well.
> >>>>>>>>
> >>>>>>>> So big +1 to solving this problem.
> >>>>>>>>
> >>>>>>>> About the exact design - I would try to go for the following
> >>>>> properties:
> >>>>>>>>
> >>>>>>>> - keep complexity of of connectors. Ideally the metrics handler
> has
> >> a
> >>>>>>>> single onRecord(numBytes, eventTime) method or so, and everything
> >>>>> else is
> >>>>>>>> internal to the handler. That makes it dead simple for the
> >> connector.
> >>>>> We
> >>>>>>>> can also think of an extensive scheme for connector specific
> >> metrics.
> >>>>>>>>
> >>>>>>>> - make it configurable on the job it cluster level which metrics
> the
> >>>>>>>> handler internally creates when that method is invoked.
> >>>>>>>>
> >>>>>>>> What do you think?
> >>>>>>>>
> >>>>>>>> Best,
> >>>>>>>> Stephan
> >>>>>>>>
> >>>>>>>>
> >>>>>>>> On Thu, Mar 21, 2019 at 10:42 AM Chesnay Schepler <
> >> chesnay@apache.org
> >>>>>>
> >>>>>>>> wrote:
> >>>>>>>>
> >>>>>>>>> As I said before, I believe this to be over-engineered and have
> no
> >>>>>>>>> interest in this implementation.
> >>>>>>>>>
> >>>>>>>>> There are conceptual issues like defining a duplicate
> >>>>>>> numBytesIn(PerSec)
> >>>>>>>>> metric that already exists for each operator.
> >>>>>>>>>
> >>>>>>>>> On 21.03.2019 06:13, Becket Qin wrote:
> >>>>>>>>>> A few updates to the thread. I uploaded a patch[1] as a complete
> >>>>>>>>>> example of how users can use the metrics in the future.
> >>>>>>>>>>
> >>>>>>>>>> Some thoughts below after taking a look at the
> AbstractMetricGroup
> >>>>>>> and
> >>>>>>>>>> its subclasses.
> >>>>>>>>>>
> >>>>>>>>>> This patch intends to provide convenience for Flink connector
> >>>>>>>>>> implementations to follow metrics standards proposed in FLIP-33.
> >> It
> >>>>>>>>>> also try to enhance the metric management in general way to help
> >>>>>>> users
> >>>>>>>>>> with:
> >>>>>>>>>>
> >>>>>>>>>> 1. metric definition
> >>>>>>>>>> 2. metric dependencies check
> >>>>>>>>>> 3. metric validation
> >>>>>>>>>> 4. metric control (turn on / off particular metrics)
> >>>>>>>>>>
> >>>>>>>>>> This patch wraps |MetricGroup| to extend the functionality of
> >>>>>>>>>> |AbstractMetricGroup| and its subclasses. The
> >>>>>>>>>> |AbstractMetricGroup| mainly focus on the metric group
> hierarchy,
> >>>>> but
> >>>>>>>>>> does not really manage the metrics other than keeping them in a
> >> Map.
> >>>>>>>>>>
> >>>>>>>>>> Ideally we should only have one entry point for the metrics.
> >>>>>>>>>>
> >>>>>>>>>> Right now the entry point is |AbstractMetricGroup|. However,
> >> besides
> >>>>>>>>>> the missing functionality mentioned above, |AbstractMetricGroup|
> >>>>>>> seems
> >>>>>>>>>> deeply rooted in Flink runtime. We could extract it out to
> >>>>>>>>>> flink-metrics in order to use it for generic purpose. There will
> >> be
> >>>>>>>>>> some work, though.
> >>>>>>>>>>
> >>>>>>>>>> Another approach is to make |AbstractMetrics| in this patch as
> the
> >>>>>>>>>> metric entry point. It wraps metric group and provides the
> missing
> >>>>>>>>>> functionalities. Then we can roll out this pattern to runtime
> >>>>>>>>>> components gradually as well.
> >>>>>>>>>>
> >>>>>>>>>> My first thought is that the latter approach gives a more smooth
> >>>>>>>>>> migration. But I am also OK with doing a refactoring on the
> >>>>>>>>>> |AbstractMetricGroup| family.
> >>>>>>>>>>
> >>>>>>>>>>
> >>>>>>>>>> Thanks,
> >>>>>>>>>>
> >>>>>>>>>> Jiangjie (Becket) Qin
> >>>>>>>>>>
> >>>>>>>>>> [1] https://github.com/becketqin/flink/pull/1
> >>>>>>>>>>
> >>>>>>>>>> On Mon, Feb 25, 2019 at 2:32 PM Becket Qin <
> becket.qin@gmail.com
> >>>>>>>>>> <ma...@gmail.com>> wrote:
> >>>>>>>>>>
> >>>>>>>>>> Hi Chesnay,
> >>>>>>>>>>
> >>>>>>>>>> It might be easier to discuss some implementation details in
> the
> >>>>>>>>>> PR review instead of in the FLIP discussion thread. I have a
> >>>>>>> patch
> >>>>>>>>>> for Kafka connectors ready but haven't submitted the PR yet.
> >>>>>>>>>> Hopefully that will help explain a bit more.
> >>>>>>>>>>
> >>>>>>>>>> ** Re: metric type binding
> >>>>>>>>>> This is a valid point that worths discussing. If I understand
> >>>>>>>>>> correctly, there are two points:
> >>>>>>>>>>
> >>>>>>>>>> 1. Metric type / interface does not matter as long as the
> metric
> >>>>>>>>>> semantic is clearly defined.
> >>>>>>>>>> Conceptually speaking, I agree that as long as the metric
> >>>>>>> semantic
> >>>>>>>>>> is defined, metric type does not matter. To some extent, Gauge
> /
> >>>>>>>>>> Counter / Meter / Histogram themselves can be think of as some
> >>>>>>>>>> well-recognized semantics, if you wish. In Flink, these metric
> >>>>>>>>>> semantics have their associated interface classes. In practice,
> >>>>>>>>>> such semantic to interface binding seems necessary for
> different
> >>>>>>>>>> components to communicate. Simply standardize the semantic of
> >>>>>>> the
> >>>>>>>>>> connector metrics seems not sufficient for people to build
> >>>>>>>>>> ecosystem on top of. At the end of the day, we still need to
> >> have
> >>>>>>>>>> some embodiment of the metric semantics that people can program
> >>>>>>>>>> against.
> >>>>>>>>>>
> >>>>>>>>>> 2. Sometimes the same metric semantic can be exposed using
> >>>>>>>>>> different metric types / interfaces.
> >>>>>>>>>> This is a good point. Counter and Gauge-as-a-Counter are pretty
> >>>>>>>>>> much interchangeable. This is more of a trade-off between the
> >>>>>>> user
> >>>>>>>>>> experience of metric producers and consumers. The metric
> >>>>>>> producers
> >>>>>>>>>> want to use Counter or Gauge depending on whether the counter
> is
> >>>>>>>>>> already tracked in code, while ideally the metric consumers
> only
> >>>>>>>>>> want to see a single metric type for each metric. I am leaning
> >>>>>>>>>> towards to make the metric producers happy, i.e. allow Gauge /
> >>>>>>>>>> Counter metric type, and the the metric consumers handle the
> >> type
> >>>>>>>>>> variation. The reason is that in practice, there might be more
> >>>>>>>>>> connector implementations than metric reporter implementations.
> >>>>>>> We
> >>>>>>>>>> could also provide some helper method to facilitate reading
> from
> >>>>>>>>>> such variable metric type.
> >>>>>>>>>>
> >>>>>>>>>>
> >>>>>>>>>> Just some quick replies to the comments around implementation
> >>>>>>>>> details.
> >>>>>>>>>>
> >>>>>>>>>> 4) single place where metrics are registered except
> >>>>>>>>>> connector-specific
> >>>>>>>>>> ones (which we can't really avoid).
> >>>>>>>>>>
> >>>>>>>>>> Register connector specific ones in a single place is actually
> >>>>>>>>>> something that I want to achieve.
> >>>>>>>>>>
> >>>>>>>>>> 2) I'm talking about time-series databases like Prometheus.
> >>>>>>> We
> >>>>>>>>>> would
> >>>>>>>>>> only have a gauge metric exposing the last
> >> fetchTime/emitTime
> >>>>>>>>>> that is
> >>>>>>>>>> regularly reported to the backend (Prometheus), where a
> user
> >>>>>>>>>> could build
> >>>>>>>>>> a histogram of his choosing when/if he wants it.
> >>>>>>>>>>
> >>>>>>>>>> Not sure if such downsampling works. As an example, if a user
> >>>>>>>>>> complains that there are some intermittent latency spikes
> (maybe
> >>>>>>> a
> >>>>>>>>>> few records in 10 seconds) in their processing system. Having a
> >>>>>>>>>> Gauge sampling instantaneous latency seems unlikely useful.
> >>>>>>>>>> However by looking at actual 99.9 percentile latency might
> help.
> >>>>>>>>>>
> >>>>>>>>>> Thanks,
> >>>>>>>>>>
> >>>>>>>>>> Jiangjie (Becket) Qin
> >>>>>>>>>>
> >>>>>>>>>>
> >>>>>>>>>> On Fri, Feb 22, 2019 at 9:30 PM Chesnay Schepler
> >>>>>>>>>> <chesnay@apache.org <ma...@apache.org>> wrote:
> >>>>>>>>>>
> >>>>>>>>>> Re: over complication of implementation.
> >>>>>>>>>>
> >>>>>>>>>> I think I get understand better know what you're shooting
> >>>>>>> for,
> >>>>>>>>>> effectively something like the OperatorIOMetricGroup.
> >>>>>>>>>> But still, re-define setupConnectorMetrics() to accept a
> set
> >>>>>>>>>> of flags
> >>>>>>>>>> for counters/meters(ans _possibly_ histograms) along with a
> >>>>>>>>>> set of
> >>>>>>>>>> well-defined Optional<Gauge<?>>, and return the group.
> >>>>>>>>>>
> >>>>>>>>>> Solves all issues as far as i can tell:
> >>>>>>>>>> 1) no metrics must be created manually (except Gauges,
> which
> >>>>>>>> are
> >>>>>>>>>> effectively just Suppliers and you can't get around this),
> >>>>>>>>>> 2) additional metrics can be registered on the returned
> >>>>>>> group,
> >>>>>>>>>> 3) see 1),
> >>>>>>>>>> 4) single place where metrics are registered except
> >>>>>>>>>> connector-specific
> >>>>>>>>>> ones (which we can't really avoid).
> >>>>>>>>>>
> >>>>>>>>>> Re: Histogram
> >>>>>>>>>>
> >>>>>>>>>> 1) As an example, whether "numRecordsIn" is exposed as a
> >>>>>>>>>> Counter or a
> >>>>>>>>>> Gauge should be irrelevant. So far we're using the metric
> >>>>>>> type
> >>>>>>>>>> that is
> >>>>>>>>>> the most convenient at exposing a given value. If there is
> >>>>>>>>>> some backing
> >>>>>>>>>> data-structure that we want to expose some data from we
> >>>>>>>>>> typically opt
> >>>>>>>>>> for a Gauge, as otherwise we're just mucking around with
> the
> >>>>>>>>>> Meter/Counter API to get it to match. Similarly, if we want
> >>>>>>> to
> >>>>>>>>>> count
> >>>>>>>>>> something but no current count exists we typically added a
> >>>>>>>>>> Counter.
> >>>>>>>>>> That's why attaching semantics to metric types makes little
> >>>>>>>>>> sense (but
> >>>>>>>>>> unfortunately several reporters already do it); for
> >>>>>>>>>> counters/meters
> >>>>>>>>>> certainly, but the majority of metrics are gauges.
> >>>>>>>>>>
> >>>>>>>>>> 2) I'm talking about time-series databases like Prometheus.
> >>>>>>> We
> >>>>>>>>>> would
> >>>>>>>>>> only have a gauge metric exposing the last
> >> fetchTime/emitTime
> >>>>>>>>>> that is
> >>>>>>>>>> regularly reported to the backend (Prometheus), where a
> user
> >>>>>>>>>> could build
> >>>>>>>>>> a histogram of his choosing when/if he wants it.
> >>>>>>>>>>
> >>>>>>>>>> On 22.02.2019 13:57, Becket Qin wrote:
> >>>>>>>>>>> Hi Chesnay,
> >>>>>>>>>>>
> >>>>>>>>>>> Thanks for the explanation.
> >>>>>>>>>>>
> >>>>>>>>>>> ** Re: FLIP
> >>>>>>>>>>> I might have misunderstood this, but it seems that "major
> >>>>>>>>>> changes" are well
> >>>>>>>>>>> defined in FLIP. The full contents is following:
> >>>>>>>>>>> What is considered a "major change" that needs a FLIP?
> >>>>>>>>>>>
> >>>>>>>>>>> Any of the following should be considered a major change:
> >>>>>>>>>>>
> >>>>>>>>>>> - Any major new feature, subsystem, or piece of
> >>>>>>>>>> functionality
> >>>>>>>>>>> - *Any change that impacts the public interfaces of the
> >>>>>>>>>> project*
> >>>>>>>>>>>
> >>>>>>>>>>> What are the "public interfaces" of the project?
> >>>>>>>>>>>
> >>>>>>>>>>>
> >>>>>>>>>>>
> >>>>>>>>>>> *All of the following are public interfaces *that people
> >>>>>>>>>> build around:
> >>>>>>>>>>>
> >>>>>>>>>>> - DataStream and DataSet API, including classes related
> >>>>>>>>>> to that, such as
> >>>>>>>>>>> StreamExecutionEnvironment
> >>>>>>>>>>>
> >>>>>>>>>>>
> >>>>>>>>>>> - Classes marked with the @Public annotation
> >>>>>>>>>>>
> >>>>>>>>>>>
> >>>>>>>>>>> - On-disk binary formats, such as
> >>>>>>> checkpoints/savepoints
> >>>>>>>>>>>
> >>>>>>>>>>>
> >>>>>>>>>>> - User-facing scripts/command-line tools, i.e.
> >>>>>>>>>> bin/flink, Yarn scripts,
> >>>>>>>>>>> Mesos scripts
> >>>>>>>>>>>
> >>>>>>>>>>>
> >>>>>>>>>>> - Configuration settings
> >>>>>>>>>>>
> >>>>>>>>>>>
> >>>>>>>>>>> - *Exposed monitoring information*
> >>>>>>>>>>>
> >>>>>>>>>>>
> >>>>>>>>>>> So any monitoring information change is considered as
> >>>>>>> public
> >>>>>>>>>> interface, and
> >>>>>>>>>>> any public interface change is considered as a "major
> >>>>>>>> change".
> >>>>>>>>>>>
> >>>>>>>>>>>
> >>>>>>>>>>> ** Re: over complication of implementation.
> >>>>>>>>>>>
> >>>>>>>>>>> Although this is more of implementation details that is not
> >>>>>>>>>> covered by the
> >>>>>>>>>>> FLIP. But it may be worth discussing.
> >>>>>>>>>>>
> >>>>>>>>>>> First of all, I completely agree that we should use the
> >>>>>>>>>> simplest way to
> >>>>>>>>>>> achieve our goal. To me the goal is the following:
> >>>>>>>>>>> 1. Clear connector conventions and interfaces.
> >>>>>>>>>>> 2. The easiness of creating a connector.
> >>>>>>>>>>>
> >>>>>>>>>>> Both of them are important to the prosperity of the
> >>>>>>>>>> connector ecosystem. So
> >>>>>>>>>>> I'd rather abstract as much as possible on our side to make
> >>>>>>>>>> the connector
> >>>>>>>>>>> developer's work lighter. Given this goal, a static util
> >>>>>>>>>> method approach
> >>>>>>>>>>> might have a few drawbacks:
> >>>>>>>>>>> 1. Users still have to construct the metrics by themselves.
> >>>>>>>>>> (And note that
> >>>>>>>>>>> this might be erroneous by itself. For example, a customer
> >>>>>>>>>> wrapper around
> >>>>>>>>>>> dropwizard meter maybe used instead of MeterView).
> >>>>>>>>>>> 2. When connector specific metrics are added, it is
> >>>>>>>>>> difficult to enforce
> >>>>>>>>>>> the scope to be the same as standard metrics.
> >>>>>>>>>>> 3. It seems that a method proliferation is inevitable if we
> >>>>>>>>>> want to apply
> >>>>>>>>>>> sanity checks. e.g. The metric of numBytesIn was not
> >>>>>>>>>> registered for a meter.
> >>>>>>>>>>> 4. Metrics are still defined in random places and hard to
> >>>>>>>>> track.
> >>>>>>>>>>>
> >>>>>>>>>>> The current PR I had was inspired by the Config system in
> >>>>>>>>>> Kafka, which I
> >>>>>>>>>>> found pretty handy. In fact it is not only used by Kafka
> >>>>>>>>>> itself but even
> >>>>>>>>>>> some other projects that depend on Kafka. I am not saying
> >>>>>>>>>> this approach is
> >>>>>>>>>>> perfect. But I think it worths to save the work for
> >>>>>>>>>> connector writers and
> >>>>>>>>>>> encourage more systematic implementation. That being said,
> >>>>>>> I
> >>>>>>>>>> am fully open
> >>>>>>>>>>> to suggestions.
> >>>>>>>>>>>
> >>>>>>>>>>>
> >>>>>>>>>>> Re: Histogram
> >>>>>>>>>>> I think there are two orthogonal questions around those
> >>>>>>>>> metrics:
> >>>>>>>>>>>
> >>>>>>>>>>> 1. Regardless of the metric type, by just looking at the
> >>>>>>>>>> meaning of a
> >>>>>>>>>>> metric, is generic to all connectors? If the answer is yes,
> >>>>>>>>>> we should
> >>>>>>>>>>> include the metric into the convention. No matter whether
> >>>>>>> we
> >>>>>>>>>> include it
> >>>>>>>>>>> into the convention or not, some connector implementations
> >>>>>>>>>> will emit such
> >>>>>>>>>>> metric. It is better to have a convention than letting each
> >>>>>>>>>> connector do
> >>>>>>>>>>> random things.
> >>>>>>>>>>>
> >>>>>>>>>>> 2. If a standard metric is a histogram, what should we do?
> >>>>>>>>>>> I agree that we should make it clear that using histograms
> >>>>>>>>>> will have
> >>>>>>>>>>> performance risk. But I do see histogram is useful in some
> >>>>>>>>>> fine-granularity
> >>>>>>>>>>> debugging where one do not have the luxury to stop the
> >>>>>>>>>> system and inject
> >>>>>>>>>>> more inspection code. So the workaround I am thinking is to
> >>>>>>>>>> provide some
> >>>>>>>>>>> implementation suggestions. Assume later on we have a
> >>>>>>>>>> mechanism of
> >>>>>>>>>>> selective metrics. In the abstract metrics class we can
> >>>>>>>>>> disable those
> >>>>>>>>>>> metrics by default individual connector writers does not
> >>>>>>>>>> have to do
> >>>>>>>>>>> anything (this is another advantage of having an
> >>>>>>>>>> AbstractMetrics instead of
> >>>>>>>>>>> static util methods.)
> >>>>>>>>>>>
> >>>>>>>>>>> I am not sure I fully understand the histogram in the
> >>>>>>>>>> backend approach. Can
> >>>>>>>>>>> you explain a bit more? Do you mean emitting the raw data,
> >>>>>>>>>> e.g. fetchTime
> >>>>>>>>>>> and emitTime with each record and let the histogram
> >>>>>>>>>> computation happen in
> >>>>>>>>>>> the background? Or let the processing thread putting the
> >>>>>>>>>> values into a
> >>>>>>>>>>> queue and have a separate thread polling from the queue and
> >>>>>>>>>> add them into
> >>>>>>>>>>> the histogram?
> >>>>>>>>>>>
> >>>>>>>>>>> Thanks,
> >>>>>>>>>>>
> >>>>>>>>>>> Jiangjie (Becket) Qin
> >>>>>>>>>>>
> >>>>>>>>>>>
> >>>>>>>>>>>
> >>>>>>>>>>>
> >>>>>>>>>>>
> >>>>>>>>>>> On Fri, Feb 22, 2019 at 4:34 PM Chesnay Schepler
> >>>>>>>>>> <chesnay@apache.org <ma...@apache.org>> wrote:
> >>>>>>>>>>>
> >>>>>>>>>>>> Re: Flip
> >>>>>>>>>>>> The very first line under both the main header and Purpose
> >>>>>>>>>> section
> >>>>>>>>>>>> describe Flips as "major changes", which this isn't.
> >>>>>>>>>>>>
> >>>>>>>>>>>> Re: complication
> >>>>>>>>>>>> I'm not arguing against standardization, but again an
> >>>>>>>>>> over-complicated
> >>>>>>>>>>>> implementation when a static utility method would be
> >>>>>>>>>> sufficient.
> >>>>>>>>>>>>
> >>>>>>>>>>>> public static void setupConnectorMetrics(
> >>>>>>>>>>>> MetricGroup operatorMetricGroup,
> >>>>>>>>>>>> String connectorName,
> >>>>>>>>>>>> Optional<Gauge<Long>> numRecordsIn,
> >>>>>>>>>>>> ...)
> >>>>>>>>>>>>
> >>>>>>>>>>>> This gives you all you need:
> >>>>>>>>>>>> * a well-defined set of metrics for a connector to opt-in
> >>>>>>>>>>>> * standardized naming schemes for scope and individual
> >>>>>>>> metrics
> >>>>>>>>>>>> * standardize metric types (although personally I'm not
> >>>>>>>>>> interested in that
> >>>>>>>>>>>> since metric types should be considered syntactic sugar)
> >>>>>>>>>>>>
> >>>>>>>>>>>> Re: Configurable Histogram
> >>>>>>>>>>>> If anything they _must_ be turned off by default, but the
> >>>>>>>>>> metric system is
> >>>>>>>>>>>> already exposing so many options that I'm not too keen on
> >>>>>>>>>> adding even more.
> >>>>>>>>>>>> You have also only addressed my first argument against
> >>>>>>>>>> histograms
> >>>>>>>>>>>> (performance), the second one still stands (calculate
> >>>>>>>>>> histogram in metric
> >>>>>>>>>>>> backends instead).
> >>>>>>>>>>>>
> >>>>>>>>>>>> On 21.02.2019 16:27, Becket Qin wrote:
> >>>>>>>>>>>>> Hi Chesnay,
> >>>>>>>>>>>>>
> >>>>>>>>>>>>> Thanks for the comments. I think this is worthy of a FLIP
> >>>>>>>>>> because it is
> >>>>>>>>>>>>> public API. According to the FLIP description a FlIP is
> >>>>>>>>>> required in case
> >>>>>>>>>>>> of:
> >>>>>>>>>>>>> - Any change that impacts the public interfaces of
> >>>>>>>>>> the project
> >>>>>>>>>>>>>
> >>>>>>>>>>>>> and the following entry is found in the definition of
> >>>>>>>>>> "public interface".
> >>>>>>>>>>>>>
> >>>>>>>>>>>>> - Exposed monitoring information
> >>>>>>>>>>>>>
> >>>>>>>>>>>>> Metrics are critical to any production system. So a clear
> >>>>>>>>>> metric
> >>>>>>>>>>>> definition
> >>>>>>>>>>>>> is important for any serious users. For an organization
> >>>>>>>>>> with large Flink
> >>>>>>>>>>>>> installation, change in metrics means great amount of
> >>>>>>>>>> work. So such
> >>>>>>>>>>>> changes
> >>>>>>>>>>>>> do need to be fully discussed and documented.
> >>>>>>>>>>>>>
> >>>>>>>>>>>>> ** Re: Histogram.
> >>>>>>>>>>>>> We can discuss whether there is a better way to expose
> >>>>>>>>>> metrics that are
> >>>>>>>>>>>>> suitable for histograms. My micro-benchmark on various
> >>>>>>>>>> histogram
> >>>>>>>>>>>>> implementations also indicates that they are
> >>>>>>> significantly
> >>>>>>>>>> slower than
> >>>>>>>>>>>>> other metric types. But I don't think that means never
> >>>>>>> use
> >>>>>>>>>> histogram, but
> >>>>>>>>>>>>> means use it with caution. For example, we can suggest
> >>>>>>> the
> >>>>>>>>>>>> implementations
> >>>>>>>>>>>>> to turn them off by default and only turn it on for a
> >>>>>>>>>> small amount of
> >>>>>>>>>>>> time
> >>>>>>>>>>>>> when performing some micro-debugging.
> >>>>>>>>>>>>>
> >>>>>>>>>>>>> ** Re: complication:
> >>>>>>>>>>>>> Connector conventions are essential for Flink ecosystem.
> >>>>>>>>>> Flink connectors
> >>>>>>>>>>>>> pool is probably the most important part of Flink, just
> >>>>>>>>>> like any other
> >>>>>>>>>>>> data
> >>>>>>>>>>>>> system. Clear conventions of connectors will help build
> >>>>>>>>>> Flink ecosystem
> >>>>>>>>>>>> in
> >>>>>>>>>>>>> a more organic way.
> >>>>>>>>>>>>> Take the metrics convention as an example, imagine
> >>>>>>> someone
> >>>>>>>>>> has developed
> >>>>>>>>>>>> a
> >>>>>>>>>>>>> Flink connector for System foo, and another developer may
> >>>>>>>>>> have developed
> >>>>>>>>>>>> a
> >>>>>>>>>>>>> monitoring and diagnostic framework for Flink which
> >>>>>>>>>> analyzes the Flink
> >>>>>>>>>>>> job
> >>>>>>>>>>>>> performance based on metrics. With a clear metric
> >>>>>>>>>> convention, those two
> >>>>>>>>>>>>> projects could be developed independently. Once users put
> >>>>>>>>>> them together,
> >>>>>>>>>>>>> it would work without additional modifications. This
> >>>>>>>>>> cannot be easily
> >>>>>>>>>>>>> achieved by just defining a few constants.
> >>>>>>>>>>>>>
> >>>>>>>>>>>>> ** Re: selective metrics:
> >>>>>>>>>>>>> Sure, we can discuss that in a separate thread.
> >>>>>>>>>>>>>
> >>>>>>>>>>>>> @Dawid
> >>>>>>>>>>>>>
> >>>>>>>>>>>>> ** Re: latency / fetchedLatency
> >>>>>>>>>>>>> The primary purpose of establish such a convention is to
> >>>>>>>>>> help developers
> >>>>>>>>>>>>> write connectors in a more compatible way. The convention
> >>>>>>>>>> is supposed to
> >>>>>>>>>>>> be
> >>>>>>>>>>>>> defined more proactively. So when look at the convention,
> >>>>>>>>>> it seems more
> >>>>>>>>>>>>> important to see if the concept is applicable to
> >>>>>>>>>> connectors in general.
> >>>>>>>>>>>> It
> >>>>>>>>>>>>> might be true so far only Kafka connector reports
> >>>>>>> latency.
> >>>>>>>>>> But there
> >>>>>>>>>>>> might
> >>>>>>>>>>>>> be hundreds of other connector implementations in the
> >>>>>>>>>> Flink ecosystem,
> >>>>>>>>>>>>> though not in the Flink repo, and some of them also emits
> >>>>>>>>>> latency. I
> >>>>>>>>>>>> think
> >>>>>>>>>>>>> a lot of other sources actually also has an append
> >>>>>>>>>> timestamp. e.g.
> >>>>>>>>>>>> database
> >>>>>>>>>>>>> bin logs and some K-V stores. So I wouldn't be surprised
> >>>>>>>>>> if some database
> >>>>>>>>>>>>> connector can also emit latency metrics.
> >>>>>>>>>>>>>
> >>>>>>>>>>>>> Thanks,
> >>>>>>>>>>>>>
> >>>>>>>>>>>>> Jiangjie (Becket) Qin
> >>>>>>>>>>>>>
> >>>>>>>>>>>>>
> >>>>>>>>>>>>> On Thu, Feb 21, 2019 at 10:14 PM Chesnay Schepler
> >>>>>>>>>> <chesnay@apache.org <ma...@apache.org>>
> >>>>>>>>>>>>> wrote:
> >>>>>>>>>>>>>
> >>>>>>>>>>>>>> Regarding 2) It doesn't make sense to investigate this
> >>>>>>> as
> >>>>>>>>>> part of this
> >>>>>>>>>>>>>> FLIP. This is something that could be of interest for
> >>>>>>> the
> >>>>>>>>>> entire metric
> >>>>>>>>>>>>>> system, and should be designed for as such.
> >>>>>>>>>>>>>>
> >>>>>>>>>>>>>> Regarding the proposal as a whole:
> >>>>>>>>>>>>>>
> >>>>>>>>>>>>>> Histogram metrics shall not be added to the core of
> >>>>>>>>>> Flink. They are
> >>>>>>>>>>>>>> significantly more expensive than other metrics, and
> >>>>>>>>>> calculating
> >>>>>>>>>>>>>> histograms in the application is regarded as an
> >>>>>>>>>> anti-pattern by several
> >>>>>>>>>>>>>> metric backends, who instead recommend to expose the raw
> >>>>>>>>>> data and
> >>>>>>>>>>>>>> calculate the histogram in the backend.
> >>>>>>>>>>>>>>
> >>>>>>>>>>>>>> Second, this seems overly complicated. Given that we
> >>>>>>>>>> already established
> >>>>>>>>>>>>>> that not all connectors will export all metrics we are
> >>>>>>>>>> effectively
> >>>>>>>>>>>>>> reducing this down to a consistent naming scheme. We
> >>>>>>>>>> don't need anything
> >>>>>>>>>>>>>> sophisticated for that; basically just a few constants
> >>>>>>>>>> that all
> >>>>>>>>>>>>>> connectors use.
> >>>>>>>>>>>>>>
> >>>>>>>>>>>>>> I'm not convinced that this is worthy of a FLIP.
> >>>>>>>>>>>>>>
> >>>>>>>>>>>>>> On 21.02.2019 14:26, Dawid Wysakowicz wrote:
> >>>>>>>>>>>>>>> Hi,
> >>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>> Ad 1. In general I undestand and I agree. But those
> >>>>>>>>>> particular metrics
> >>>>>>>>>>>>>>> (latency, fetchLatency), right now would only be
> >>>>>>>>>> reported if user uses
> >>>>>>>>>>>>>>> KafkaConsumer with internal timestampAssigner with
> >>>>>>>>>> StreamCharacteristic
> >>>>>>>>>>>>>>> set to EventTime, right? That sounds like a very
> >>>>>>>>>> specific case. I am
> >>>>>>>>>>>> not
> >>>>>>>>>>>>>>> sure if we should introduce a generic metric that will
> >>>>>>> be
> >>>>>>>>>>>>>>> disabled/absent for most of implementations.
> >>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>> Ad.2 That sounds like an orthogonal issue, that might
> >>>>>>>>>> make sense to
> >>>>>>>>>>>>>>> investigate in the future.
> >>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>> Best,
> >>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>> Dawid
> >>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>> On 21/02/2019 13:20, Becket Qin wrote:
> >>>>>>>>>>>>>>>> Hi Dawid,
> >>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>> Thanks for the feedback. That makes sense to me. There
> >>>>>>>>>> are two cases
> >>>>>>>>>>>> to
> >>>>>>>>>>>>>> be
> >>>>>>>>>>>>>>>> addressed.
> >>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>> 1. The metrics are supposed to be a guidance. It is
> >>>>>>>>>> likely that a
> >>>>>>>>>>>>>> connector
> >>>>>>>>>>>>>>>> only supports some but not all of the metrics. In that
> >>>>>>>>>> case, each
> >>>>>>>>>>>>>> connector
> >>>>>>>>>>>>>>>> implementation should have the freedom to decide which
> >>>>>>>>>> metrics are
> >>>>>>>>>>>>>>>> reported. For the metrics that are supported, the
> >>>>>>>>>> guidance should be
> >>>>>>>>>>>>>>>> followed.
> >>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>> 2. Sometimes users may want to disable certain metrics
> >>>>>>>>>> for some reason
> >>>>>>>>>>>>>>>> (e.g. performance / reprocessing of data). A generic
> >>>>>>>>>> mechanism should
> >>>>>>>>>>>> be
> >>>>>>>>>>>>>>>> provided to allow user choose which metrics are
> >>>>>>>>>> reported. This
> >>>>>>>>>>>> mechanism
> >>>>>>>>>>>>>>>> should also be honored by the connector
> >>>>>>> implementations.
> >>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>> Does this sound reasonable to you?
> >>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>> Thanks,
> >>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>> Jiangjie (Becket) Qin
> >>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>> On Thu, Feb 21, 2019 at 4:22 PM Dawid Wysakowicz <
> >>>>>>>>>>>>>> dwysakowicz@apache.org <ma...@apache.org>>
> >>>>>>>>>>>>>>>> wrote:
> >>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>> Hi,
> >>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>> Generally I like the idea of having a unified,
> >>>>>>>>>> standard set of
> >>>>>>>>>>>> metrics
> >>>>>>>>>>>>>> for
> >>>>>>>>>>>>>>>>> all connectors. I have some slight concerns about
> >>>>>>>>>> fetchLatency and
> >>>>>>>>>>>>>>>>> latency though. They are computed based on EventTime
> >>>>>>>>>> which is not a
> >>>>>>>>>>>>>> purely
> >>>>>>>>>>>>>>>>> technical feature. It depends often on some business
> >>>>>>>>>> logic, might be
> >>>>>>>>>>>>>> absent
> >>>>>>>>>>>>>>>>> or defined after source. Those metrics could also
> >>>>>>>>>> behave in a weird
> >>>>>>>>>>>>>> way in
> >>>>>>>>>>>>>>>>> case of replaying backlog. Therefore I am not sure if
> >>>>>>>>>> we should
> >>>>>>>>>>>> include
> >>>>>>>>>>>>>>>>> those metrics by default. Maybe we could at least
> >>>>>>>>>> introduce a feature
> >>>>>>>>>>>>>>>>> switch for them? What do you think?
> >>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>> Best,
> >>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>> Dawid
> >>>>>>>>>>>>>>>>> On 21/02/2019 03:13, Becket Qin wrote:
> >>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>> Bump. If there is no objections to the proposed
> >>>>>>>>>> metrics. I'll start a
> >>>>>>>>>>>>>>>>> voting thread later toady.
> >>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>> Thanks,
> >>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>> Jiangjie (Becket) Qin
> >>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>> On Mon, Feb 11, 2019 at 8:17 PM Becket Qin
> >>>>>>>>>> <becket.qin@gmail.com <ma...@gmail.com>> <
> >>>>>>>>>>>>>> becket.qin@gmail.com <ma...@gmail.com>>
> >>>>>>>> wrote:
> >>>>>>>>>>>>>>>>> Hi folks,
> >>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>> I would like to start the FLIP discussion thread
> >>>>>>> about
> >>>>>>>>>> standardize
> >>>>>>>>>>>> the
> >>>>>>>>>>>>>>>>> connector metrics.
> >>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>> In short, we would like to provide a convention of
> >>>>>>>>>> Flink connector
> >>>>>>>>>>>>>>>>> metrics. It will help simplify the monitoring and
> >>>>>>>>>> alerting on Flink
> >>>>>>>>>>>>>> jobs.
> >>>>>>>>>>>>>>>>> The FLIP link is following:
> >>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>
> >>>>>>>>>>
> >>>>>>>>>
> >>>>>>>>
> >>>>>>>
> >>>>>
> >>
> https://cwiki.apache.org/confluence/display/FLINK/FLIP-33%3A+Standardize+Connector+Metrics
> >>>>>>>>>>>>>>>>> Thanks,
> >>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>> Jiangjie (Becket) Qin
> >>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>
> >>>>>>>>>>
> >>>>>>>>>
> >>>>>>>>>
> >>>>>>>>
> >>>>>>>
> >>>>>
> >>>>>
> >>
> >>
> >>
>
>
>
Re: [DISCUSS] FLIP-33: Standardize connector metrics
Posted by Piotr Nowojski <pi...@ververica.com>.
Hi again :)
> - pending.bytes, Gauge
> - pending.messages, Gauge
+1
And true, instead of overloading one of the metric it is better when user can choose to provide only one of them.
Re 2:
> If I understand correctly, this metric along with the pending mesages /
> bytes would answer the questions of:
> - Does the connector consume fast enough? Lagging behind + empty buffer =
> cannot consume fast enough.
> - Does the connector emit fast enough? Lagging behind + full buffer =
> cannot emit fast enough, i.e. the Flink pipeline is slow.
Yes, exactly. This can also be used to support decisions like changing the parallelism of the sources and/or down stream operators.
I’m not sure if I understand your proposal with time based measurements. Maybe I’m missing something, but I do not see how measuring time alone could answer the problem: where is the bottleneck. Time spent on the next/emit might be short or long (depending on how heavy to process the record is) and the source can still be bottlenecked/back pressured or not. Usually the easiest and the most reliable way how to detect bottlenecks is by checking usage of input & output buffers, since when input buffer is full while output buffer is empty, that’s the definition of a bottleneck. Also this is usually very easy and cheap to measure (it works effectively the same way as current’s Flink back pressure monitoring, but more cleanly, without probing thread’s stack traces).
Also keep in mind that we are already using the buffer usage metrics for detecting the bottlenecks in Flink’s internal network exchanges (manual work). That’s the reason why I wanted to extend this to sources/sinks, since they are currently our blind spot.
> One feature we are currently working on to scale Flink automatically relies
> on some metrics answering the same question
That would be very helpful feature. I think in order to achieve that we would need to:
1. Define the metrics that would allow us to manually detect bottlenecks. As I wrote, we already have them in most of the places, except of sources/sinks.
2. Use those metrics, to automatically detect bottlenecks. Currently we are only automatically detecting back pressure and reporting it to the user in web UI (is it exposed as a metric at all?). Detecting the root cause of the back pressure (bottleneck) is one step further.
3. Use the knowledge about where exactly the bottleneck is located, to try to do something with it.
I think you are aiming for point 3., but before we reach it, we are still missing 1. & 2. Also even if we have 3., there is a value in 1 & 2 for manual analysis/dashboards.
However, having the knowledge of where the bottleneck is, doesn’t necessarily mean that we know what we can do about it. For example increasing parallelism might or might not help with anything (data skew, bottleneck on some resource that does not scale), but this remark applies always, regardless of the way how did we detect the bottleneck.
Piotrek
> On 3 Jun 2019, at 06:16, Becket Qin <be...@gmail.com> wrote:
>
> Hi Piotr,
>
> Thanks for the suggestion. Some thoughts below:
>
> Re 1: The pending messages / bytes.
> I completely agree these are very useful metrics and we should expect the
> connector to report. WRT the way to expose them, it seems more consistent
> to add two metrics instead of adding a method (unless there are other use
> cases other than metric reporting). So we can add the following two metrics.
> - pending.bytes, Gauge
> - pending.messages, Gauge
> Applicable connectors can choose to report them. These two metrics along
> with latency should be sufficient for users to understand the progress of a
> connector.
>
>
> Re 2: Number of buffered data in-memory of the connector
> If I understand correctly, this metric along with the pending mesages /
> bytes would answer the questions of:
> - Does the connector consume fast enough? Lagging behind + empty buffer =
> cannot consume fast enough.
> - Does the connector emit fast enough? Lagging behind + full buffer =
> cannot emit fast enough, i.e. the Flink pipeline is slow.
>
> One feature we are currently working on to scale Flink automatically relies
> on some metrics answering the same question, more specifically, we are
> profiling the time spent on .next() method (time to consume) and the time
> spent on .collect() method (time to emit / process). One advantage of such
> method level time cost allows us to calculate the parallelism required to
> keep up in case their is a lag.
>
> However, one concern I have regarding such metric is that they are
> implementation specific. Either profiling on the method time, or reporting
> buffer usage assumes the connector are implemented in such a way. A
> slightly better solution might be have the following metric:
>
> - EmitTimeRatio (or FetchTimeRatio): The time spent on emitting
> records / Total time elapsed.
>
> This assumes that the source connectors have to emit the records to the
> downstream at some point. The emission may take some time ( e.g. go through
> chained operators). And the rest of the time are spent to prepare the
> record to emit, including time for consuming and format conversion, etc.
> Ideally, we'd like to see the time spent on record fetch and emit to be
> about the same, so no one is bottleneck for the other.
>
> The downside of these time based metrics is additional overhead to get the
> time, therefore sampling might be needed. But in practice I feel such time
> based metric might be more useful if we want to take action.
>
>
> I think we should absolutely add metrics in (1) to the metric convention.
> We could also add the metrics mentioned in (2) if we reach consensus on
> that. What do you think?
>
> Thanks,
>
> Jiangjie (Becket) Qin
>
>
> On Fri, May 31, 2019 at 4:26 PM Piotr Nowojski <pi...@ververica.com> wrote:
>
>> Hey Becket,
>>
>> Re 1a) and 1b) +1 from my side.
>>
>> I’ve discussed this issue:
>>
>>>>>
>>>>> 2. It would be nice to have metrics, that allow us to check the cause
>> of
>>>>> back pressure:
>>>>> a) for sources, length of input queue (in bytes? Or boolean
>>>>> hasSomethingl/isEmpty)
>>>>> b) for sinks, length of output queue (in bytes? Or boolean
>>>>> hasSomething/isEmpty)
>>
>> With Nico at some lengths and he also saw the benefits of them. We also
>> have more concrete proposal for that.
>>
>> Actually there are two really useful metrics, that we are missing
>> currently:
>>
>> 1. Number of data/records/bytes in the backlog to process. For example
>> remaining number of bytes in unread files. Or pending data in Kafka topics.
>> 2. Number of buffered data in-memory of the connector, that are waiting to
>> be processed pushed to Flink pipeline.
>>
>> Re 1:
>> This would have to be a metric provided directly by a connector. It could
>> be an undefined `int`:
>>
>> `int backlog` - estimate of pending work.
>>
>> “Undefined” meaning that it would be up to a connector to decided whether
>> it’s measured in bytes, records, pending files or whatever it is possible
>> to provide by the connector. This is because I assume not every connector
>> can provide exact number and for some of them it might be impossible to
>> provide records number of bytes count.
>>
>> Re 2:
>> This metric could be either provided by a connector, or calculated crudely
>> by Flink:
>>
>> `float bufferUsage` - value from [0.0, 1.0] range
>>
>> Percentage of used in memory buffers, like in Kafka’s handover.
>>
>> It could be crudely implemented by Flink with FLIP-27
>> SourceReader#isAvailable. If SourceReader is not available reported
>> `bufferUsage` could be 0.0. If it is available, it could be 1.0. I think
>> this would be a good enough estimation for most of the use cases (that
>> could be overloaded and implemented better if desired). Especially since we
>> are reporting only probed values: if probed values are almost always “1.0”,
>> it would mean that we have a back pressure. If they are almost always
>> “0.0”, there is probably no back pressure at the sources.
>>
>> What do you think about this?
>>
>> Piotrek
>>
>>> On 30 May 2019, at 11:41, Becket Qin <be...@gmail.com> wrote:
>>>
>>> Hi all,
>>>
>>> Thanks a lot for all the feedback and comments. I'd like to continue the
>>> discussion on this FLIP.
>>>
>>> I updated the FLIP-33 wiki to remove all the histogram metrics from the
>>> first version of metric convention due to the performance concern. The
>> plan
>>> is to introduce them later when we have a mechanism to opt in/out
>> metrics.
>>> At that point, users can decide whether they want to pay the cost to get
>>> the metric or not.
>>>
>>> As Stephan suggested, for this FLIP, let's first try to agree on the
>> small
>>> list of conventional metrics that connectors should follow.
>>> Just to be clear, the purpose of the convention is not to enforce every
>>> connector to report all these metrics, but to provide a guidance in case
>>> these metrics are reported by some connectors.
>>>
>>>
>>> @ Stephan & Chesnay,
>>>
>>> Regarding the duplication of `RecordsIn` metric in operator / task
>>> IOMetricGroups, from what I understand, for source operator, it is
>> actually
>>> the SourceFunction that reports the operator level
>>> RecordsIn/RecordsInPerSecond metric. So they are essentially the same
>>> metric in the operator level IOMetricGroup. Similarly for the Sink
>>> operator, the operator level RecordsOut/RecordsOutPerSecond metrics are
>>> also reported by the Sink function. I marked them as existing in the
>>> FLIP-33 wiki page. Please let me know if I misunderstood.
>>>
>>> Thanks,
>>>
>>> Jiangjie (Becket) Qin
>>>
>>>
>>> On Thu, May 30, 2019 at 5:16 PM Becket Qin <be...@gmail.com> wrote:
>>>
>>>> Hi Piotr,
>>>>
>>>> Thanks a lot for the feedback.
>>>>
>>>> 1a) I guess you are referring to the part that "original system specific
>>>> metrics should also be reported". The performance impact depends on the
>>>> implementation. An efficient implementation would only record the metric
>>>> once, but report them with two different metric names. This is unlikely
>> to
>>>> hurt performance.
>>>>
>>>> 1b) Yes, I agree that we should avoid adding overhead to the critical
>> path
>>>> by all means. This is sometimes a tradeoff, running blindly without any
>>>> metric gives best performance, but sometimes might be frustrating when
>> we
>>>> debug some issues.
>>>>
>>>> 2. The metrics are indeed very useful. Are they supposed to be reported
>> by
>>>> the connectors or Flink itself? At this point FLIP-33 is more focused on
>>>> provide a guidance to the connector authors on the metrics reporting.
>> That
>>>> said, after FLIP-27, I think we should absolutely report these metrics
>> in
>>>> the abstract implementation. In any case, the metric convention in this
>>>> list are expected to evolve over time.
>>>>
>>>> Thanks,
>>>>
>>>> Jiangjie (Becket) Qin
>>>>
>>>> On Tue, May 28, 2019 at 6:24 PM Piotr Nowojski <pi...@ververica.com>
>>>> wrote:
>>>>
>>>>> Hi,
>>>>>
>>>>> Thanks for the proposal and driving the effort here Becket :) I’ve read
>>>>> through the FLIP-33 [1], and here are couple of my thoughts.
>>>>>
>>>>> Big +1 for standardising the metric names between connectors, it will
>>>>> definitely help us and users a lot.
>>>>>
>>>>> Issues/questions/things to discuss that I’ve thought of:
>>>>>
>>>>> 1a. If we are about to duplicate some metrics, can this become a
>>>>> performance issue?
>>>>> 1b. Generally speaking, we should make sure that collecting those
>> metrics
>>>>> is as non intrusive as possible, especially that they will need to be
>>>>> updated once per record. (They might be collected more rarely with some
>>>>> overhead, but the hot path of updating it per record will need to be as
>>>>> quick as possible). That includes both avoiding heavy computation on
>> per
>>>>> record path: histograms?, measuring time for time based metrics (per
>>>>> second) (System.currentTimeMillis() depending on the implementation can
>>>>> invoke a system call)
>>>>>
>>>>> 2. It would be nice to have metrics, that allow us to check the cause
>> of
>>>>> back pressure:
>>>>> a) for sources, length of input queue (in bytes? Or boolean
>>>>> hasSomethingl/isEmpty)
>>>>> b) for sinks, length of output queue (in bytes? Or boolean
>>>>> hasSomething/isEmpty)
>>>>>
>>>>> a) is useful in a scenario when we are processing backlog of records,
>> all
>>>>> of the internal Flink’s input/output network buffers are empty, and we
>> want
>>>>> to check whether the external source system is the bottleneck (source’s
>>>>> input queue will be empty), or if the Flink’s connector is the
>> bottleneck
>>>>> (source’s input queues will be full).
>>>>> b) similar story. Backlog of records, but this time all of the internal
>>>>> Flink’s input/ouput network buffers are full, and we want o check
>> whether
>>>>> the external sink system is the bottleneck (sink output queues are
>> full),
>>>>> or if the Flink’s connector is the bottleneck (sink’s output queues
>> will be
>>>>> empty)
>>>>>
>>>>> It might be sometimes difficult to provide those metrics, so they could
>>>>> be optional, but if we could provide them, it would be really helpful.
>>>>>
>>>>> Piotrek
>>>>>
>>>>> [1]
>>>>>
>> https://cwiki.apache.org/confluence/display/FLINK/FLIP-33:+Standardize+Connector+Metrics
>>>>> <
>>>>>
>> https://cwiki.apache.org/confluence/display/FLINK/FLIP-33:+Standardize+Connector+Metrics
>>>>>>
>>>>>
>>>>>> On 24 Apr 2019, at 13:28, Stephan Ewen <se...@apache.org> wrote:
>>>>>>
>>>>>> I think this sounds reasonable.
>>>>>>
>>>>>> Let's keep the "reconfiguration without stopping the job" out of this,
>>>>>> because that would be a super big effort and if we approach that, then
>>>>> in
>>>>>> more generic way rather than specific to connector metrics.
>>>>>>
>>>>>> I would suggest to look at the following things before starting with
>> any
>>>>>> implementation work:
>>>>>>
>>>>>> - Try and find a committer to support this, otherwise it will be hard
>>>>> to
>>>>>> make progress
>>>>>> - Start with defining a smaller set of "core metrics" and extend the
>>>>> set
>>>>>> later. I think that is easier than now blocking on reaching consensus
>>>>> on a
>>>>>> large group of metrics.
>>>>>> - Find a solution to the problem Chesnay mentioned, that the "records
>>>>> in"
>>>>>> metric is somehow overloaded and exists already in the IO Metric
>> group.
>>>>>>
>>>>>>
>>>>>> On Mon, Mar 25, 2019 at 7:16 AM Becket Qin <be...@gmail.com>
>>>>> wrote:
>>>>>>
>>>>>>> Hi Stephan,
>>>>>>>
>>>>>>> Thanks a lot for the feedback. All makes sense.
>>>>>>>
>>>>>>> It is a good suggestion to simply have an onRecord(numBytes,
>> eventTime)
>>>>>>> method for connector writers. It should meet most of the
>> requirements,
>>>>>>> individual
>>>>>>>
>>>>>>> The configurable metrics feature is something really useful,
>>>>> especially if
>>>>>>> we can somehow make it dynamically configurable without stopping the
>>>>> jobs.
>>>>>>> It might be better to make it a separate discussion because it is a
>>>>> more
>>>>>>> generic feature instead of only for connectors.
>>>>>>>
>>>>>>> So in order to make some progress, in this FLIP we can limit the
>>>>> discussion
>>>>>>> scope to the connector related items:
>>>>>>>
>>>>>>> - the standard connector metric names and types.
>>>>>>> - the abstract ConnectorMetricHandler interface
>>>>>>>
>>>>>>> I'll start a separate thread to discuss other general metric related
>>>>>>> enhancement items including:
>>>>>>>
>>>>>>> - optional metrics
>>>>>>> - dynamic metric configuration
>>>>>>> - potential combination with rate limiter
>>>>>>>
>>>>>>> Does this plan sound reasonable?
>>>>>>>
>>>>>>> Thanks,
>>>>>>>
>>>>>>> Jiangjie (Becket) Qin
>>>>>>>
>>>>>>> On Sat, Mar 23, 2019 at 5:53 AM Stephan Ewen <se...@apache.org>
>> wrote:
>>>>>>>
>>>>>>>> Ignoring for a moment implementation details, this connector metrics
>>>>> work
>>>>>>>> is a really good thing to do, in my opinion
>>>>>>>>
>>>>>>>> The questions "oh, my job seems to be doing nothing, I am looking at
>>>>> the
>>>>>>> UI
>>>>>>>> and the 'records in' value is still zero" is in the top three
>> support
>>>>>>>> questions I have been asked personally.
>>>>>>>> Introspection into "how far is the consumer lagging behind" (event
>>>>> time
>>>>>>>> fetch latency) came up many times as well.
>>>>>>>>
>>>>>>>> So big +1 to solving this problem.
>>>>>>>>
>>>>>>>> About the exact design - I would try to go for the following
>>>>> properties:
>>>>>>>>
>>>>>>>> - keep complexity of of connectors. Ideally the metrics handler has
>> a
>>>>>>>> single onRecord(numBytes, eventTime) method or so, and everything
>>>>> else is
>>>>>>>> internal to the handler. That makes it dead simple for the
>> connector.
>>>>> We
>>>>>>>> can also think of an extensive scheme for connector specific
>> metrics.
>>>>>>>>
>>>>>>>> - make it configurable on the job it cluster level which metrics the
>>>>>>>> handler internally creates when that method is invoked.
>>>>>>>>
>>>>>>>> What do you think?
>>>>>>>>
>>>>>>>> Best,
>>>>>>>> Stephan
>>>>>>>>
>>>>>>>>
>>>>>>>> On Thu, Mar 21, 2019 at 10:42 AM Chesnay Schepler <
>> chesnay@apache.org
>>>>>>
>>>>>>>> wrote:
>>>>>>>>
>>>>>>>>> As I said before, I believe this to be over-engineered and have no
>>>>>>>>> interest in this implementation.
>>>>>>>>>
>>>>>>>>> There are conceptual issues like defining a duplicate
>>>>>>> numBytesIn(PerSec)
>>>>>>>>> metric that already exists for each operator.
>>>>>>>>>
>>>>>>>>> On 21.03.2019 06:13, Becket Qin wrote:
>>>>>>>>>> A few updates to the thread. I uploaded a patch[1] as a complete
>>>>>>>>>> example of how users can use the metrics in the future.
>>>>>>>>>>
>>>>>>>>>> Some thoughts below after taking a look at the AbstractMetricGroup
>>>>>>> and
>>>>>>>>>> its subclasses.
>>>>>>>>>>
>>>>>>>>>> This patch intends to provide convenience for Flink connector
>>>>>>>>>> implementations to follow metrics standards proposed in FLIP-33.
>> It
>>>>>>>>>> also try to enhance the metric management in general way to help
>>>>>>> users
>>>>>>>>>> with:
>>>>>>>>>>
>>>>>>>>>> 1. metric definition
>>>>>>>>>> 2. metric dependencies check
>>>>>>>>>> 3. metric validation
>>>>>>>>>> 4. metric control (turn on / off particular metrics)
>>>>>>>>>>
>>>>>>>>>> This patch wraps |MetricGroup| to extend the functionality of
>>>>>>>>>> |AbstractMetricGroup| and its subclasses. The
>>>>>>>>>> |AbstractMetricGroup| mainly focus on the metric group hierarchy,
>>>>> but
>>>>>>>>>> does not really manage the metrics other than keeping them in a
>> Map.
>>>>>>>>>>
>>>>>>>>>> Ideally we should only have one entry point for the metrics.
>>>>>>>>>>
>>>>>>>>>> Right now the entry point is |AbstractMetricGroup|. However,
>> besides
>>>>>>>>>> the missing functionality mentioned above, |AbstractMetricGroup|
>>>>>>> seems
>>>>>>>>>> deeply rooted in Flink runtime. We could extract it out to
>>>>>>>>>> flink-metrics in order to use it for generic purpose. There will
>> be
>>>>>>>>>> some work, though.
>>>>>>>>>>
>>>>>>>>>> Another approach is to make |AbstractMetrics| in this patch as the
>>>>>>>>>> metric entry point. It wraps metric group and provides the missing
>>>>>>>>>> functionalities. Then we can roll out this pattern to runtime
>>>>>>>>>> components gradually as well.
>>>>>>>>>>
>>>>>>>>>> My first thought is that the latter approach gives a more smooth
>>>>>>>>>> migration. But I am also OK with doing a refactoring on the
>>>>>>>>>> |AbstractMetricGroup| family.
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>> Thanks,
>>>>>>>>>>
>>>>>>>>>> Jiangjie (Becket) Qin
>>>>>>>>>>
>>>>>>>>>> [1] https://github.com/becketqin/flink/pull/1
>>>>>>>>>>
>>>>>>>>>> On Mon, Feb 25, 2019 at 2:32 PM Becket Qin <becket.qin@gmail.com
>>>>>>>>>> <ma...@gmail.com>> wrote:
>>>>>>>>>>
>>>>>>>>>> Hi Chesnay,
>>>>>>>>>>
>>>>>>>>>> It might be easier to discuss some implementation details in the
>>>>>>>>>> PR review instead of in the FLIP discussion thread. I have a
>>>>>>> patch
>>>>>>>>>> for Kafka connectors ready but haven't submitted the PR yet.
>>>>>>>>>> Hopefully that will help explain a bit more.
>>>>>>>>>>
>>>>>>>>>> ** Re: metric type binding
>>>>>>>>>> This is a valid point that worths discussing. If I understand
>>>>>>>>>> correctly, there are two points:
>>>>>>>>>>
>>>>>>>>>> 1. Metric type / interface does not matter as long as the metric
>>>>>>>>>> semantic is clearly defined.
>>>>>>>>>> Conceptually speaking, I agree that as long as the metric
>>>>>>> semantic
>>>>>>>>>> is defined, metric type does not matter. To some extent, Gauge /
>>>>>>>>>> Counter / Meter / Histogram themselves can be think of as some
>>>>>>>>>> well-recognized semantics, if you wish. In Flink, these metric
>>>>>>>>>> semantics have their associated interface classes. In practice,
>>>>>>>>>> such semantic to interface binding seems necessary for different
>>>>>>>>>> components to communicate. Simply standardize the semantic of
>>>>>>> the
>>>>>>>>>> connector metrics seems not sufficient for people to build
>>>>>>>>>> ecosystem on top of. At the end of the day, we still need to
>> have
>>>>>>>>>> some embodiment of the metric semantics that people can program
>>>>>>>>>> against.
>>>>>>>>>>
>>>>>>>>>> 2. Sometimes the same metric semantic can be exposed using
>>>>>>>>>> different metric types / interfaces.
>>>>>>>>>> This is a good point. Counter and Gauge-as-a-Counter are pretty
>>>>>>>>>> much interchangeable. This is more of a trade-off between the
>>>>>>> user
>>>>>>>>>> experience of metric producers and consumers. The metric
>>>>>>> producers
>>>>>>>>>> want to use Counter or Gauge depending on whether the counter is
>>>>>>>>>> already tracked in code, while ideally the metric consumers only
>>>>>>>>>> want to see a single metric type for each metric. I am leaning
>>>>>>>>>> towards to make the metric producers happy, i.e. allow Gauge /
>>>>>>>>>> Counter metric type, and the the metric consumers handle the
>> type
>>>>>>>>>> variation. The reason is that in practice, there might be more
>>>>>>>>>> connector implementations than metric reporter implementations.
>>>>>>> We
>>>>>>>>>> could also provide some helper method to facilitate reading from
>>>>>>>>>> such variable metric type.
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>> Just some quick replies to the comments around implementation
>>>>>>>>> details.
>>>>>>>>>>
>>>>>>>>>> 4) single place where metrics are registered except
>>>>>>>>>> connector-specific
>>>>>>>>>> ones (which we can't really avoid).
>>>>>>>>>>
>>>>>>>>>> Register connector specific ones in a single place is actually
>>>>>>>>>> something that I want to achieve.
>>>>>>>>>>
>>>>>>>>>> 2) I'm talking about time-series databases like Prometheus.
>>>>>>> We
>>>>>>>>>> would
>>>>>>>>>> only have a gauge metric exposing the last
>> fetchTime/emitTime
>>>>>>>>>> that is
>>>>>>>>>> regularly reported to the backend (Prometheus), where a user
>>>>>>>>>> could build
>>>>>>>>>> a histogram of his choosing when/if he wants it.
>>>>>>>>>>
>>>>>>>>>> Not sure if such downsampling works. As an example, if a user
>>>>>>>>>> complains that there are some intermittent latency spikes (maybe
>>>>>>> a
>>>>>>>>>> few records in 10 seconds) in their processing system. Having a
>>>>>>>>>> Gauge sampling instantaneous latency seems unlikely useful.
>>>>>>>>>> However by looking at actual 99.9 percentile latency might help.
>>>>>>>>>>
>>>>>>>>>> Thanks,
>>>>>>>>>>
>>>>>>>>>> Jiangjie (Becket) Qin
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>> On Fri, Feb 22, 2019 at 9:30 PM Chesnay Schepler
>>>>>>>>>> <chesnay@apache.org <ma...@apache.org>> wrote:
>>>>>>>>>>
>>>>>>>>>> Re: over complication of implementation.
>>>>>>>>>>
>>>>>>>>>> I think I get understand better know what you're shooting
>>>>>>> for,
>>>>>>>>>> effectively something like the OperatorIOMetricGroup.
>>>>>>>>>> But still, re-define setupConnectorMetrics() to accept a set
>>>>>>>>>> of flags
>>>>>>>>>> for counters/meters(ans _possibly_ histograms) along with a
>>>>>>>>>> set of
>>>>>>>>>> well-defined Optional<Gauge<?>>, and return the group.
>>>>>>>>>>
>>>>>>>>>> Solves all issues as far as i can tell:
>>>>>>>>>> 1) no metrics must be created manually (except Gauges, which
>>>>>>>> are
>>>>>>>>>> effectively just Suppliers and you can't get around this),
>>>>>>>>>> 2) additional metrics can be registered on the returned
>>>>>>> group,
>>>>>>>>>> 3) see 1),
>>>>>>>>>> 4) single place where metrics are registered except
>>>>>>>>>> connector-specific
>>>>>>>>>> ones (which we can't really avoid).
>>>>>>>>>>
>>>>>>>>>> Re: Histogram
>>>>>>>>>>
>>>>>>>>>> 1) As an example, whether "numRecordsIn" is exposed as a
>>>>>>>>>> Counter or a
>>>>>>>>>> Gauge should be irrelevant. So far we're using the metric
>>>>>>> type
>>>>>>>>>> that is
>>>>>>>>>> the most convenient at exposing a given value. If there is
>>>>>>>>>> some backing
>>>>>>>>>> data-structure that we want to expose some data from we
>>>>>>>>>> typically opt
>>>>>>>>>> for a Gauge, as otherwise we're just mucking around with the
>>>>>>>>>> Meter/Counter API to get it to match. Similarly, if we want
>>>>>>> to
>>>>>>>>>> count
>>>>>>>>>> something but no current count exists we typically added a
>>>>>>>>>> Counter.
>>>>>>>>>> That's why attaching semantics to metric types makes little
>>>>>>>>>> sense (but
>>>>>>>>>> unfortunately several reporters already do it); for
>>>>>>>>>> counters/meters
>>>>>>>>>> certainly, but the majority of metrics are gauges.
>>>>>>>>>>
>>>>>>>>>> 2) I'm talking about time-series databases like Prometheus.
>>>>>>> We
>>>>>>>>>> would
>>>>>>>>>> only have a gauge metric exposing the last
>> fetchTime/emitTime
>>>>>>>>>> that is
>>>>>>>>>> regularly reported to the backend (Prometheus), where a user
>>>>>>>>>> could build
>>>>>>>>>> a histogram of his choosing when/if he wants it.
>>>>>>>>>>
>>>>>>>>>> On 22.02.2019 13:57, Becket Qin wrote:
>>>>>>>>>>> Hi Chesnay,
>>>>>>>>>>>
>>>>>>>>>>> Thanks for the explanation.
>>>>>>>>>>>
>>>>>>>>>>> ** Re: FLIP
>>>>>>>>>>> I might have misunderstood this, but it seems that "major
>>>>>>>>>> changes" are well
>>>>>>>>>>> defined in FLIP. The full contents is following:
>>>>>>>>>>> What is considered a "major change" that needs a FLIP?
>>>>>>>>>>>
>>>>>>>>>>> Any of the following should be considered a major change:
>>>>>>>>>>>
>>>>>>>>>>> - Any major new feature, subsystem, or piece of
>>>>>>>>>> functionality
>>>>>>>>>>> - *Any change that impacts the public interfaces of the
>>>>>>>>>> project*
>>>>>>>>>>>
>>>>>>>>>>> What are the "public interfaces" of the project?
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>> *All of the following are public interfaces *that people
>>>>>>>>>> build around:
>>>>>>>>>>>
>>>>>>>>>>> - DataStream and DataSet API, including classes related
>>>>>>>>>> to that, such as
>>>>>>>>>>> StreamExecutionEnvironment
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>> - Classes marked with the @Public annotation
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>> - On-disk binary formats, such as
>>>>>>> checkpoints/savepoints
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>> - User-facing scripts/command-line tools, i.e.
>>>>>>>>>> bin/flink, Yarn scripts,
>>>>>>>>>>> Mesos scripts
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>> - Configuration settings
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>> - *Exposed monitoring information*
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>> So any monitoring information change is considered as
>>>>>>> public
>>>>>>>>>> interface, and
>>>>>>>>>>> any public interface change is considered as a "major
>>>>>>>> change".
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>> ** Re: over complication of implementation.
>>>>>>>>>>>
>>>>>>>>>>> Although this is more of implementation details that is not
>>>>>>>>>> covered by the
>>>>>>>>>>> FLIP. But it may be worth discussing.
>>>>>>>>>>>
>>>>>>>>>>> First of all, I completely agree that we should use the
>>>>>>>>>> simplest way to
>>>>>>>>>>> achieve our goal. To me the goal is the following:
>>>>>>>>>>> 1. Clear connector conventions and interfaces.
>>>>>>>>>>> 2. The easiness of creating a connector.
>>>>>>>>>>>
>>>>>>>>>>> Both of them are important to the prosperity of the
>>>>>>>>>> connector ecosystem. So
>>>>>>>>>>> I'd rather abstract as much as possible on our side to make
>>>>>>>>>> the connector
>>>>>>>>>>> developer's work lighter. Given this goal, a static util
>>>>>>>>>> method approach
>>>>>>>>>>> might have a few drawbacks:
>>>>>>>>>>> 1. Users still have to construct the metrics by themselves.
>>>>>>>>>> (And note that
>>>>>>>>>>> this might be erroneous by itself. For example, a customer
>>>>>>>>>> wrapper around
>>>>>>>>>>> dropwizard meter maybe used instead of MeterView).
>>>>>>>>>>> 2. When connector specific metrics are added, it is
>>>>>>>>>> difficult to enforce
>>>>>>>>>>> the scope to be the same as standard metrics.
>>>>>>>>>>> 3. It seems that a method proliferation is inevitable if we
>>>>>>>>>> want to apply
>>>>>>>>>>> sanity checks. e.g. The metric of numBytesIn was not
>>>>>>>>>> registered for a meter.
>>>>>>>>>>> 4. Metrics are still defined in random places and hard to
>>>>>>>>> track.
>>>>>>>>>>>
>>>>>>>>>>> The current PR I had was inspired by the Config system in
>>>>>>>>>> Kafka, which I
>>>>>>>>>>> found pretty handy. In fact it is not only used by Kafka
>>>>>>>>>> itself but even
>>>>>>>>>>> some other projects that depend on Kafka. I am not saying
>>>>>>>>>> this approach is
>>>>>>>>>>> perfect. But I think it worths to save the work for
>>>>>>>>>> connector writers and
>>>>>>>>>>> encourage more systematic implementation. That being said,
>>>>>>> I
>>>>>>>>>> am fully open
>>>>>>>>>>> to suggestions.
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>> Re: Histogram
>>>>>>>>>>> I think there are two orthogonal questions around those
>>>>>>>>> metrics:
>>>>>>>>>>>
>>>>>>>>>>> 1. Regardless of the metric type, by just looking at the
>>>>>>>>>> meaning of a
>>>>>>>>>>> metric, is generic to all connectors? If the answer is yes,
>>>>>>>>>> we should
>>>>>>>>>>> include the metric into the convention. No matter whether
>>>>>>> we
>>>>>>>>>> include it
>>>>>>>>>>> into the convention or not, some connector implementations
>>>>>>>>>> will emit such
>>>>>>>>>>> metric. It is better to have a convention than letting each
>>>>>>>>>> connector do
>>>>>>>>>>> random things.
>>>>>>>>>>>
>>>>>>>>>>> 2. If a standard metric is a histogram, what should we do?
>>>>>>>>>>> I agree that we should make it clear that using histograms
>>>>>>>>>> will have
>>>>>>>>>>> performance risk. But I do see histogram is useful in some
>>>>>>>>>> fine-granularity
>>>>>>>>>>> debugging where one do not have the luxury to stop the
>>>>>>>>>> system and inject
>>>>>>>>>>> more inspection code. So the workaround I am thinking is to
>>>>>>>>>> provide some
>>>>>>>>>>> implementation suggestions. Assume later on we have a
>>>>>>>>>> mechanism of
>>>>>>>>>>> selective metrics. In the abstract metrics class we can
>>>>>>>>>> disable those
>>>>>>>>>>> metrics by default individual connector writers does not
>>>>>>>>>> have to do
>>>>>>>>>>> anything (this is another advantage of having an
>>>>>>>>>> AbstractMetrics instead of
>>>>>>>>>>> static util methods.)
>>>>>>>>>>>
>>>>>>>>>>> I am not sure I fully understand the histogram in the
>>>>>>>>>> backend approach. Can
>>>>>>>>>>> you explain a bit more? Do you mean emitting the raw data,
>>>>>>>>>> e.g. fetchTime
>>>>>>>>>>> and emitTime with each record and let the histogram
>>>>>>>>>> computation happen in
>>>>>>>>>>> the background? Or let the processing thread putting the
>>>>>>>>>> values into a
>>>>>>>>>>> queue and have a separate thread polling from the queue and
>>>>>>>>>> add them into
>>>>>>>>>>> the histogram?
>>>>>>>>>>>
>>>>>>>>>>> Thanks,
>>>>>>>>>>>
>>>>>>>>>>> Jiangjie (Becket) Qin
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>> On Fri, Feb 22, 2019 at 4:34 PM Chesnay Schepler
>>>>>>>>>> <chesnay@apache.org <ma...@apache.org>> wrote:
>>>>>>>>>>>
>>>>>>>>>>>> Re: Flip
>>>>>>>>>>>> The very first line under both the main header and Purpose
>>>>>>>>>> section
>>>>>>>>>>>> describe Flips as "major changes", which this isn't.
>>>>>>>>>>>>
>>>>>>>>>>>> Re: complication
>>>>>>>>>>>> I'm not arguing against standardization, but again an
>>>>>>>>>> over-complicated
>>>>>>>>>>>> implementation when a static utility method would be
>>>>>>>>>> sufficient.
>>>>>>>>>>>>
>>>>>>>>>>>> public static void setupConnectorMetrics(
>>>>>>>>>>>> MetricGroup operatorMetricGroup,
>>>>>>>>>>>> String connectorName,
>>>>>>>>>>>> Optional<Gauge<Long>> numRecordsIn,
>>>>>>>>>>>> ...)
>>>>>>>>>>>>
>>>>>>>>>>>> This gives you all you need:
>>>>>>>>>>>> * a well-defined set of metrics for a connector to opt-in
>>>>>>>>>>>> * standardized naming schemes for scope and individual
>>>>>>>> metrics
>>>>>>>>>>>> * standardize metric types (although personally I'm not
>>>>>>>>>> interested in that
>>>>>>>>>>>> since metric types should be considered syntactic sugar)
>>>>>>>>>>>>
>>>>>>>>>>>> Re: Configurable Histogram
>>>>>>>>>>>> If anything they _must_ be turned off by default, but the
>>>>>>>>>> metric system is
>>>>>>>>>>>> already exposing so many options that I'm not too keen on
>>>>>>>>>> adding even more.
>>>>>>>>>>>> You have also only addressed my first argument against
>>>>>>>>>> histograms
>>>>>>>>>>>> (performance), the second one still stands (calculate
>>>>>>>>>> histogram in metric
>>>>>>>>>>>> backends instead).
>>>>>>>>>>>>
>>>>>>>>>>>> On 21.02.2019 16:27, Becket Qin wrote:
>>>>>>>>>>>>> Hi Chesnay,
>>>>>>>>>>>>>
>>>>>>>>>>>>> Thanks for the comments. I think this is worthy of a FLIP
>>>>>>>>>> because it is
>>>>>>>>>>>>> public API. According to the FLIP description a FlIP is
>>>>>>>>>> required in case
>>>>>>>>>>>> of:
>>>>>>>>>>>>> - Any change that impacts the public interfaces of
>>>>>>>>>> the project
>>>>>>>>>>>>>
>>>>>>>>>>>>> and the following entry is found in the definition of
>>>>>>>>>> "public interface".
>>>>>>>>>>>>>
>>>>>>>>>>>>> - Exposed monitoring information
>>>>>>>>>>>>>
>>>>>>>>>>>>> Metrics are critical to any production system. So a clear
>>>>>>>>>> metric
>>>>>>>>>>>> definition
>>>>>>>>>>>>> is important for any serious users. For an organization
>>>>>>>>>> with large Flink
>>>>>>>>>>>>> installation, change in metrics means great amount of
>>>>>>>>>> work. So such
>>>>>>>>>>>> changes
>>>>>>>>>>>>> do need to be fully discussed and documented.
>>>>>>>>>>>>>
>>>>>>>>>>>>> ** Re: Histogram.
>>>>>>>>>>>>> We can discuss whether there is a better way to expose
>>>>>>>>>> metrics that are
>>>>>>>>>>>>> suitable for histograms. My micro-benchmark on various
>>>>>>>>>> histogram
>>>>>>>>>>>>> implementations also indicates that they are
>>>>>>> significantly
>>>>>>>>>> slower than
>>>>>>>>>>>>> other metric types. But I don't think that means never
>>>>>>> use
>>>>>>>>>> histogram, but
>>>>>>>>>>>>> means use it with caution. For example, we can suggest
>>>>>>> the
>>>>>>>>>>>> implementations
>>>>>>>>>>>>> to turn them off by default and only turn it on for a
>>>>>>>>>> small amount of
>>>>>>>>>>>> time
>>>>>>>>>>>>> when performing some micro-debugging.
>>>>>>>>>>>>>
>>>>>>>>>>>>> ** Re: complication:
>>>>>>>>>>>>> Connector conventions are essential for Flink ecosystem.
>>>>>>>>>> Flink connectors
>>>>>>>>>>>>> pool is probably the most important part of Flink, just
>>>>>>>>>> like any other
>>>>>>>>>>>> data
>>>>>>>>>>>>> system. Clear conventions of connectors will help build
>>>>>>>>>> Flink ecosystem
>>>>>>>>>>>> in
>>>>>>>>>>>>> a more organic way.
>>>>>>>>>>>>> Take the metrics convention as an example, imagine
>>>>>>> someone
>>>>>>>>>> has developed
>>>>>>>>>>>> a
>>>>>>>>>>>>> Flink connector for System foo, and another developer may
>>>>>>>>>> have developed
>>>>>>>>>>>> a
>>>>>>>>>>>>> monitoring and diagnostic framework for Flink which
>>>>>>>>>> analyzes the Flink
>>>>>>>>>>>> job
>>>>>>>>>>>>> performance based on metrics. With a clear metric
>>>>>>>>>> convention, those two
>>>>>>>>>>>>> projects could be developed independently. Once users put
>>>>>>>>>> them together,
>>>>>>>>>>>>> it would work without additional modifications. This
>>>>>>>>>> cannot be easily
>>>>>>>>>>>>> achieved by just defining a few constants.
>>>>>>>>>>>>>
>>>>>>>>>>>>> ** Re: selective metrics:
>>>>>>>>>>>>> Sure, we can discuss that in a separate thread.
>>>>>>>>>>>>>
>>>>>>>>>>>>> @Dawid
>>>>>>>>>>>>>
>>>>>>>>>>>>> ** Re: latency / fetchedLatency
>>>>>>>>>>>>> The primary purpose of establish such a convention is to
>>>>>>>>>> help developers
>>>>>>>>>>>>> write connectors in a more compatible way. The convention
>>>>>>>>>> is supposed to
>>>>>>>>>>>> be
>>>>>>>>>>>>> defined more proactively. So when look at the convention,
>>>>>>>>>> it seems more
>>>>>>>>>>>>> important to see if the concept is applicable to
>>>>>>>>>> connectors in general.
>>>>>>>>>>>> It
>>>>>>>>>>>>> might be true so far only Kafka connector reports
>>>>>>> latency.
>>>>>>>>>> But there
>>>>>>>>>>>> might
>>>>>>>>>>>>> be hundreds of other connector implementations in the
>>>>>>>>>> Flink ecosystem,
>>>>>>>>>>>>> though not in the Flink repo, and some of them also emits
>>>>>>>>>> latency. I
>>>>>>>>>>>> think
>>>>>>>>>>>>> a lot of other sources actually also has an append
>>>>>>>>>> timestamp. e.g.
>>>>>>>>>>>> database
>>>>>>>>>>>>> bin logs and some K-V stores. So I wouldn't be surprised
>>>>>>>>>> if some database
>>>>>>>>>>>>> connector can also emit latency metrics.
>>>>>>>>>>>>>
>>>>>>>>>>>>> Thanks,
>>>>>>>>>>>>>
>>>>>>>>>>>>> Jiangjie (Becket) Qin
>>>>>>>>>>>>>
>>>>>>>>>>>>>
>>>>>>>>>>>>> On Thu, Feb 21, 2019 at 10:14 PM Chesnay Schepler
>>>>>>>>>> <chesnay@apache.org <ma...@apache.org>>
>>>>>>>>>>>>> wrote:
>>>>>>>>>>>>>
>>>>>>>>>>>>>> Regarding 2) It doesn't make sense to investigate this
>>>>>>> as
>>>>>>>>>> part of this
>>>>>>>>>>>>>> FLIP. This is something that could be of interest for
>>>>>>> the
>>>>>>>>>> entire metric
>>>>>>>>>>>>>> system, and should be designed for as such.
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> Regarding the proposal as a whole:
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> Histogram metrics shall not be added to the core of
>>>>>>>>>> Flink. They are
>>>>>>>>>>>>>> significantly more expensive than other metrics, and
>>>>>>>>>> calculating
>>>>>>>>>>>>>> histograms in the application is regarded as an
>>>>>>>>>> anti-pattern by several
>>>>>>>>>>>>>> metric backends, who instead recommend to expose the raw
>>>>>>>>>> data and
>>>>>>>>>>>>>> calculate the histogram in the backend.
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> Second, this seems overly complicated. Given that we
>>>>>>>>>> already established
>>>>>>>>>>>>>> that not all connectors will export all metrics we are
>>>>>>>>>> effectively
>>>>>>>>>>>>>> reducing this down to a consistent naming scheme. We
>>>>>>>>>> don't need anything
>>>>>>>>>>>>>> sophisticated for that; basically just a few constants
>>>>>>>>>> that all
>>>>>>>>>>>>>> connectors use.
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> I'm not convinced that this is worthy of a FLIP.
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> On 21.02.2019 14:26, Dawid Wysakowicz wrote:
>>>>>>>>>>>>>>> Hi,
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> Ad 1. In general I undestand and I agree. But those
>>>>>>>>>> particular metrics
>>>>>>>>>>>>>>> (latency, fetchLatency), right now would only be
>>>>>>>>>> reported if user uses
>>>>>>>>>>>>>>> KafkaConsumer with internal timestampAssigner with
>>>>>>>>>> StreamCharacteristic
>>>>>>>>>>>>>>> set to EventTime, right? That sounds like a very
>>>>>>>>>> specific case. I am
>>>>>>>>>>>> not
>>>>>>>>>>>>>>> sure if we should introduce a generic metric that will
>>>>>>> be
>>>>>>>>>>>>>>> disabled/absent for most of implementations.
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> Ad.2 That sounds like an orthogonal issue, that might
>>>>>>>>>> make sense to
>>>>>>>>>>>>>>> investigate in the future.
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> Best,
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> Dawid
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> On 21/02/2019 13:20, Becket Qin wrote:
>>>>>>>>>>>>>>>> Hi Dawid,
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>> Thanks for the feedback. That makes sense to me. There
>>>>>>>>>> are two cases
>>>>>>>>>>>> to
>>>>>>>>>>>>>> be
>>>>>>>>>>>>>>>> addressed.
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>> 1. The metrics are supposed to be a guidance. It is
>>>>>>>>>> likely that a
>>>>>>>>>>>>>> connector
>>>>>>>>>>>>>>>> only supports some but not all of the metrics. In that
>>>>>>>>>> case, each
>>>>>>>>>>>>>> connector
>>>>>>>>>>>>>>>> implementation should have the freedom to decide which
>>>>>>>>>> metrics are
>>>>>>>>>>>>>>>> reported. For the metrics that are supported, the
>>>>>>>>>> guidance should be
>>>>>>>>>>>>>>>> followed.
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>> 2. Sometimes users may want to disable certain metrics
>>>>>>>>>> for some reason
>>>>>>>>>>>>>>>> (e.g. performance / reprocessing of data). A generic
>>>>>>>>>> mechanism should
>>>>>>>>>>>> be
>>>>>>>>>>>>>>>> provided to allow user choose which metrics are
>>>>>>>>>> reported. This
>>>>>>>>>>>> mechanism
>>>>>>>>>>>>>>>> should also be honored by the connector
>>>>>>> implementations.
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>> Does this sound reasonable to you?
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>> Thanks,
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>> Jiangjie (Becket) Qin
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>> On Thu, Feb 21, 2019 at 4:22 PM Dawid Wysakowicz <
>>>>>>>>>>>>>> dwysakowicz@apache.org <ma...@apache.org>>
>>>>>>>>>>>>>>>> wrote:
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>> Hi,
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>> Generally I like the idea of having a unified,
>>>>>>>>>> standard set of
>>>>>>>>>>>> metrics
>>>>>>>>>>>>>> for
>>>>>>>>>>>>>>>>> all connectors. I have some slight concerns about
>>>>>>>>>> fetchLatency and
>>>>>>>>>>>>>>>>> latency though. They are computed based on EventTime
>>>>>>>>>> which is not a
>>>>>>>>>>>>>> purely
>>>>>>>>>>>>>>>>> technical feature. It depends often on some business
>>>>>>>>>> logic, might be
>>>>>>>>>>>>>> absent
>>>>>>>>>>>>>>>>> or defined after source. Those metrics could also
>>>>>>>>>> behave in a weird
>>>>>>>>>>>>>> way in
>>>>>>>>>>>>>>>>> case of replaying backlog. Therefore I am not sure if
>>>>>>>>>> we should
>>>>>>>>>>>> include
>>>>>>>>>>>>>>>>> those metrics by default. Maybe we could at least
>>>>>>>>>> introduce a feature
>>>>>>>>>>>>>>>>> switch for them? What do you think?
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>> Best,
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>> Dawid
>>>>>>>>>>>>>>>>> On 21/02/2019 03:13, Becket Qin wrote:
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>> Bump. If there is no objections to the proposed
>>>>>>>>>> metrics. I'll start a
>>>>>>>>>>>>>>>>> voting thread later toady.
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>> Thanks,
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>> Jiangjie (Becket) Qin
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>> On Mon, Feb 11, 2019 at 8:17 PM Becket Qin
>>>>>>>>>> <becket.qin@gmail.com <ma...@gmail.com>> <
>>>>>>>>>>>>>> becket.qin@gmail.com <ma...@gmail.com>>
>>>>>>>> wrote:
>>>>>>>>>>>>>>>>> Hi folks,
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>> I would like to start the FLIP discussion thread
>>>>>>> about
>>>>>>>>>> standardize
>>>>>>>>>>>> the
>>>>>>>>>>>>>>>>> connector metrics.
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>> In short, we would like to provide a convention of
>>>>>>>>>> Flink connector
>>>>>>>>>>>>>>>>> metrics. It will help simplify the monitoring and
>>>>>>>>>> alerting on Flink
>>>>>>>>>>>>>> jobs.
>>>>>>>>>>>>>>>>> The FLIP link is following:
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>
>>>>>>>>
>>>>>>>
>>>>>
>> https://cwiki.apache.org/confluence/display/FLINK/FLIP-33%3A+Standardize+Connector+Metrics
>>>>>>>>>>>>>>>>> Thanks,
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>> Jiangjie (Becket) Qin
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>
>>>>>>>
>>>>>
>>>>>
>>
>>
>>
Re: [DISCUSS] FLIP-33: Standardize connector metrics
Posted by Becket Qin <be...@gmail.com>.
Hi Piotr,
Thanks for the suggestion. Some thoughts below:
Re 1: The pending messages / bytes.
I completely agree these are very useful metrics and we should expect the
connector to report. WRT the way to expose them, it seems more consistent
to add two metrics instead of adding a method (unless there are other use
cases other than metric reporting). So we can add the following two metrics.
- pending.bytes, Gauge
- pending.messages, Gauge
Applicable connectors can choose to report them. These two metrics along
with latency should be sufficient for users to understand the progress of a
connector.
Re 2: Number of buffered data in-memory of the connector
If I understand correctly, this metric along with the pending mesages /
bytes would answer the questions of:
- Does the connector consume fast enough? Lagging behind + empty buffer =
cannot consume fast enough.
- Does the connector emit fast enough? Lagging behind + full buffer =
cannot emit fast enough, i.e. the Flink pipeline is slow.
One feature we are currently working on to scale Flink automatically relies
on some metrics answering the same question, more specifically, we are
profiling the time spent on .next() method (time to consume) and the time
spent on .collect() method (time to emit / process). One advantage of such
method level time cost allows us to calculate the parallelism required to
keep up in case their is a lag.
However, one concern I have regarding such metric is that they are
implementation specific. Either profiling on the method time, or reporting
buffer usage assumes the connector are implemented in such a way. A
slightly better solution might be have the following metric:
- EmitTimeRatio (or FetchTimeRatio): The time spent on emitting
records / Total time elapsed.
This assumes that the source connectors have to emit the records to the
downstream at some point. The emission may take some time ( e.g. go through
chained operators). And the rest of the time are spent to prepare the
record to emit, including time for consuming and format conversion, etc.
Ideally, we'd like to see the time spent on record fetch and emit to be
about the same, so no one is bottleneck for the other.
The downside of these time based metrics is additional overhead to get the
time, therefore sampling might be needed. But in practice I feel such time
based metric might be more useful if we want to take action.
I think we should absolutely add metrics in (1) to the metric convention.
We could also add the metrics mentioned in (2) if we reach consensus on
that. What do you think?
Thanks,
Jiangjie (Becket) Qin
On Fri, May 31, 2019 at 4:26 PM Piotr Nowojski <pi...@ververica.com> wrote:
> Hey Becket,
>
> Re 1a) and 1b) +1 from my side.
>
> I’ve discussed this issue:
>
> >>>
> >>> 2. It would be nice to have metrics, that allow us to check the cause
> of
> >>> back pressure:
> >>> a) for sources, length of input queue (in bytes? Or boolean
> >>> hasSomethingl/isEmpty)
> >>> b) for sinks, length of output queue (in bytes? Or boolean
> >>> hasSomething/isEmpty)
>
> With Nico at some lengths and he also saw the benefits of them. We also
> have more concrete proposal for that.
>
> Actually there are two really useful metrics, that we are missing
> currently:
>
> 1. Number of data/records/bytes in the backlog to process. For example
> remaining number of bytes in unread files. Or pending data in Kafka topics.
> 2. Number of buffered data in-memory of the connector, that are waiting to
> be processed pushed to Flink pipeline.
>
> Re 1:
> This would have to be a metric provided directly by a connector. It could
> be an undefined `int`:
>
> `int backlog` - estimate of pending work.
>
> “Undefined” meaning that it would be up to a connector to decided whether
> it’s measured in bytes, records, pending files or whatever it is possible
> to provide by the connector. This is because I assume not every connector
> can provide exact number and for some of them it might be impossible to
> provide records number of bytes count.
>
> Re 2:
> This metric could be either provided by a connector, or calculated crudely
> by Flink:
>
> `float bufferUsage` - value from [0.0, 1.0] range
>
> Percentage of used in memory buffers, like in Kafka’s handover.
>
> It could be crudely implemented by Flink with FLIP-27
> SourceReader#isAvailable. If SourceReader is not available reported
> `bufferUsage` could be 0.0. If it is available, it could be 1.0. I think
> this would be a good enough estimation for most of the use cases (that
> could be overloaded and implemented better if desired). Especially since we
> are reporting only probed values: if probed values are almost always “1.0”,
> it would mean that we have a back pressure. If they are almost always
> “0.0”, there is probably no back pressure at the sources.
>
> What do you think about this?
>
> Piotrek
>
> > On 30 May 2019, at 11:41, Becket Qin <be...@gmail.com> wrote:
> >
> > Hi all,
> >
> > Thanks a lot for all the feedback and comments. I'd like to continue the
> > discussion on this FLIP.
> >
> > I updated the FLIP-33 wiki to remove all the histogram metrics from the
> > first version of metric convention due to the performance concern. The
> plan
> > is to introduce them later when we have a mechanism to opt in/out
> metrics.
> > At that point, users can decide whether they want to pay the cost to get
> > the metric or not.
> >
> > As Stephan suggested, for this FLIP, let's first try to agree on the
> small
> > list of conventional metrics that connectors should follow.
> > Just to be clear, the purpose of the convention is not to enforce every
> > connector to report all these metrics, but to provide a guidance in case
> > these metrics are reported by some connectors.
> >
> >
> > @ Stephan & Chesnay,
> >
> > Regarding the duplication of `RecordsIn` metric in operator / task
> > IOMetricGroups, from what I understand, for source operator, it is
> actually
> > the SourceFunction that reports the operator level
> > RecordsIn/RecordsInPerSecond metric. So they are essentially the same
> > metric in the operator level IOMetricGroup. Similarly for the Sink
> > operator, the operator level RecordsOut/RecordsOutPerSecond metrics are
> > also reported by the Sink function. I marked them as existing in the
> > FLIP-33 wiki page. Please let me know if I misunderstood.
> >
> > Thanks,
> >
> > Jiangjie (Becket) Qin
> >
> >
> > On Thu, May 30, 2019 at 5:16 PM Becket Qin <be...@gmail.com> wrote:
> >
> >> Hi Piotr,
> >>
> >> Thanks a lot for the feedback.
> >>
> >> 1a) I guess you are referring to the part that "original system specific
> >> metrics should also be reported". The performance impact depends on the
> >> implementation. An efficient implementation would only record the metric
> >> once, but report them with two different metric names. This is unlikely
> to
> >> hurt performance.
> >>
> >> 1b) Yes, I agree that we should avoid adding overhead to the critical
> path
> >> by all means. This is sometimes a tradeoff, running blindly without any
> >> metric gives best performance, but sometimes might be frustrating when
> we
> >> debug some issues.
> >>
> >> 2. The metrics are indeed very useful. Are they supposed to be reported
> by
> >> the connectors or Flink itself? At this point FLIP-33 is more focused on
> >> provide a guidance to the connector authors on the metrics reporting.
> That
> >> said, after FLIP-27, I think we should absolutely report these metrics
> in
> >> the abstract implementation. In any case, the metric convention in this
> >> list are expected to evolve over time.
> >>
> >> Thanks,
> >>
> >> Jiangjie (Becket) Qin
> >>
> >> On Tue, May 28, 2019 at 6:24 PM Piotr Nowojski <pi...@ververica.com>
> >> wrote:
> >>
> >>> Hi,
> >>>
> >>> Thanks for the proposal and driving the effort here Becket :) I’ve read
> >>> through the FLIP-33 [1], and here are couple of my thoughts.
> >>>
> >>> Big +1 for standardising the metric names between connectors, it will
> >>> definitely help us and users a lot.
> >>>
> >>> Issues/questions/things to discuss that I’ve thought of:
> >>>
> >>> 1a. If we are about to duplicate some metrics, can this become a
> >>> performance issue?
> >>> 1b. Generally speaking, we should make sure that collecting those
> metrics
> >>> is as non intrusive as possible, especially that they will need to be
> >>> updated once per record. (They might be collected more rarely with some
> >>> overhead, but the hot path of updating it per record will need to be as
> >>> quick as possible). That includes both avoiding heavy computation on
> per
> >>> record path: histograms?, measuring time for time based metrics (per
> >>> second) (System.currentTimeMillis() depending on the implementation can
> >>> invoke a system call)
> >>>
> >>> 2. It would be nice to have metrics, that allow us to check the cause
> of
> >>> back pressure:
> >>> a) for sources, length of input queue (in bytes? Or boolean
> >>> hasSomethingl/isEmpty)
> >>> b) for sinks, length of output queue (in bytes? Or boolean
> >>> hasSomething/isEmpty)
> >>>
> >>> a) is useful in a scenario when we are processing backlog of records,
> all
> >>> of the internal Flink’s input/output network buffers are empty, and we
> want
> >>> to check whether the external source system is the bottleneck (source’s
> >>> input queue will be empty), or if the Flink’s connector is the
> bottleneck
> >>> (source’s input queues will be full).
> >>> b) similar story. Backlog of records, but this time all of the internal
> >>> Flink’s input/ouput network buffers are full, and we want o check
> whether
> >>> the external sink system is the bottleneck (sink output queues are
> full),
> >>> or if the Flink’s connector is the bottleneck (sink’s output queues
> will be
> >>> empty)
> >>>
> >>> It might be sometimes difficult to provide those metrics, so they could
> >>> be optional, but if we could provide them, it would be really helpful.
> >>>
> >>> Piotrek
> >>>
> >>> [1]
> >>>
> https://cwiki.apache.org/confluence/display/FLINK/FLIP-33:+Standardize+Connector+Metrics
> >>> <
> >>>
> https://cwiki.apache.org/confluence/display/FLINK/FLIP-33:+Standardize+Connector+Metrics
> >>>>
> >>>
> >>>> On 24 Apr 2019, at 13:28, Stephan Ewen <se...@apache.org> wrote:
> >>>>
> >>>> I think this sounds reasonable.
> >>>>
> >>>> Let's keep the "reconfiguration without stopping the job" out of this,
> >>>> because that would be a super big effort and if we approach that, then
> >>> in
> >>>> more generic way rather than specific to connector metrics.
> >>>>
> >>>> I would suggest to look at the following things before starting with
> any
> >>>> implementation work:
> >>>>
> >>>> - Try and find a committer to support this, otherwise it will be hard
> >>> to
> >>>> make progress
> >>>> - Start with defining a smaller set of "core metrics" and extend the
> >>> set
> >>>> later. I think that is easier than now blocking on reaching consensus
> >>> on a
> >>>> large group of metrics.
> >>>> - Find a solution to the problem Chesnay mentioned, that the "records
> >>> in"
> >>>> metric is somehow overloaded and exists already in the IO Metric
> group.
> >>>>
> >>>>
> >>>> On Mon, Mar 25, 2019 at 7:16 AM Becket Qin <be...@gmail.com>
> >>> wrote:
> >>>>
> >>>>> Hi Stephan,
> >>>>>
> >>>>> Thanks a lot for the feedback. All makes sense.
> >>>>>
> >>>>> It is a good suggestion to simply have an onRecord(numBytes,
> eventTime)
> >>>>> method for connector writers. It should meet most of the
> requirements,
> >>>>> individual
> >>>>>
> >>>>> The configurable metrics feature is something really useful,
> >>> especially if
> >>>>> we can somehow make it dynamically configurable without stopping the
> >>> jobs.
> >>>>> It might be better to make it a separate discussion because it is a
> >>> more
> >>>>> generic feature instead of only for connectors.
> >>>>>
> >>>>> So in order to make some progress, in this FLIP we can limit the
> >>> discussion
> >>>>> scope to the connector related items:
> >>>>>
> >>>>> - the standard connector metric names and types.
> >>>>> - the abstract ConnectorMetricHandler interface
> >>>>>
> >>>>> I'll start a separate thread to discuss other general metric related
> >>>>> enhancement items including:
> >>>>>
> >>>>> - optional metrics
> >>>>> - dynamic metric configuration
> >>>>> - potential combination with rate limiter
> >>>>>
> >>>>> Does this plan sound reasonable?
> >>>>>
> >>>>> Thanks,
> >>>>>
> >>>>> Jiangjie (Becket) Qin
> >>>>>
> >>>>> On Sat, Mar 23, 2019 at 5:53 AM Stephan Ewen <se...@apache.org>
> wrote:
> >>>>>
> >>>>>> Ignoring for a moment implementation details, this connector metrics
> >>> work
> >>>>>> is a really good thing to do, in my opinion
> >>>>>>
> >>>>>> The questions "oh, my job seems to be doing nothing, I am looking at
> >>> the
> >>>>> UI
> >>>>>> and the 'records in' value is still zero" is in the top three
> support
> >>>>>> questions I have been asked personally.
> >>>>>> Introspection into "how far is the consumer lagging behind" (event
> >>> time
> >>>>>> fetch latency) came up many times as well.
> >>>>>>
> >>>>>> So big +1 to solving this problem.
> >>>>>>
> >>>>>> About the exact design - I would try to go for the following
> >>> properties:
> >>>>>>
> >>>>>> - keep complexity of of connectors. Ideally the metrics handler has
> a
> >>>>>> single onRecord(numBytes, eventTime) method or so, and everything
> >>> else is
> >>>>>> internal to the handler. That makes it dead simple for the
> connector.
> >>> We
> >>>>>> can also think of an extensive scheme for connector specific
> metrics.
> >>>>>>
> >>>>>> - make it configurable on the job it cluster level which metrics the
> >>>>>> handler internally creates when that method is invoked.
> >>>>>>
> >>>>>> What do you think?
> >>>>>>
> >>>>>> Best,
> >>>>>> Stephan
> >>>>>>
> >>>>>>
> >>>>>> On Thu, Mar 21, 2019 at 10:42 AM Chesnay Schepler <
> chesnay@apache.org
> >>>>
> >>>>>> wrote:
> >>>>>>
> >>>>>>> As I said before, I believe this to be over-engineered and have no
> >>>>>>> interest in this implementation.
> >>>>>>>
> >>>>>>> There are conceptual issues like defining a duplicate
> >>>>> numBytesIn(PerSec)
> >>>>>>> metric that already exists for each operator.
> >>>>>>>
> >>>>>>> On 21.03.2019 06:13, Becket Qin wrote:
> >>>>>>>> A few updates to the thread. I uploaded a patch[1] as a complete
> >>>>>>>> example of how users can use the metrics in the future.
> >>>>>>>>
> >>>>>>>> Some thoughts below after taking a look at the AbstractMetricGroup
> >>>>> and
> >>>>>>>> its subclasses.
> >>>>>>>>
> >>>>>>>> This patch intends to provide convenience for Flink connector
> >>>>>>>> implementations to follow metrics standards proposed in FLIP-33.
> It
> >>>>>>>> also try to enhance the metric management in general way to help
> >>>>> users
> >>>>>>>> with:
> >>>>>>>>
> >>>>>>>> 1. metric definition
> >>>>>>>> 2. metric dependencies check
> >>>>>>>> 3. metric validation
> >>>>>>>> 4. metric control (turn on / off particular metrics)
> >>>>>>>>
> >>>>>>>> This patch wraps |MetricGroup| to extend the functionality of
> >>>>>>>> |AbstractMetricGroup| and its subclasses. The
> >>>>>>>> |AbstractMetricGroup| mainly focus on the metric group hierarchy,
> >>> but
> >>>>>>>> does not really manage the metrics other than keeping them in a
> Map.
> >>>>>>>>
> >>>>>>>> Ideally we should only have one entry point for the metrics.
> >>>>>>>>
> >>>>>>>> Right now the entry point is |AbstractMetricGroup|. However,
> besides
> >>>>>>>> the missing functionality mentioned above, |AbstractMetricGroup|
> >>>>> seems
> >>>>>>>> deeply rooted in Flink runtime. We could extract it out to
> >>>>>>>> flink-metrics in order to use it for generic purpose. There will
> be
> >>>>>>>> some work, though.
> >>>>>>>>
> >>>>>>>> Another approach is to make |AbstractMetrics| in this patch as the
> >>>>>>>> metric entry point. It wraps metric group and provides the missing
> >>>>>>>> functionalities. Then we can roll out this pattern to runtime
> >>>>>>>> components gradually as well.
> >>>>>>>>
> >>>>>>>> My first thought is that the latter approach gives a more smooth
> >>>>>>>> migration. But I am also OK with doing a refactoring on the
> >>>>>>>> |AbstractMetricGroup| family.
> >>>>>>>>
> >>>>>>>>
> >>>>>>>> Thanks,
> >>>>>>>>
> >>>>>>>> Jiangjie (Becket) Qin
> >>>>>>>>
> >>>>>>>> [1] https://github.com/becketqin/flink/pull/1
> >>>>>>>>
> >>>>>>>> On Mon, Feb 25, 2019 at 2:32 PM Becket Qin <becket.qin@gmail.com
> >>>>>>>> <ma...@gmail.com>> wrote:
> >>>>>>>>
> >>>>>>>> Hi Chesnay,
> >>>>>>>>
> >>>>>>>> It might be easier to discuss some implementation details in the
> >>>>>>>> PR review instead of in the FLIP discussion thread. I have a
> >>>>> patch
> >>>>>>>> for Kafka connectors ready but haven't submitted the PR yet.
> >>>>>>>> Hopefully that will help explain a bit more.
> >>>>>>>>
> >>>>>>>> ** Re: metric type binding
> >>>>>>>> This is a valid point that worths discussing. If I understand
> >>>>>>>> correctly, there are two points:
> >>>>>>>>
> >>>>>>>> 1. Metric type / interface does not matter as long as the metric
> >>>>>>>> semantic is clearly defined.
> >>>>>>>> Conceptually speaking, I agree that as long as the metric
> >>>>> semantic
> >>>>>>>> is defined, metric type does not matter. To some extent, Gauge /
> >>>>>>>> Counter / Meter / Histogram themselves can be think of as some
> >>>>>>>> well-recognized semantics, if you wish. In Flink, these metric
> >>>>>>>> semantics have their associated interface classes. In practice,
> >>>>>>>> such semantic to interface binding seems necessary for different
> >>>>>>>> components to communicate. Simply standardize the semantic of
> >>>>> the
> >>>>>>>> connector metrics seems not sufficient for people to build
> >>>>>>>> ecosystem on top of. At the end of the day, we still need to
> have
> >>>>>>>> some embodiment of the metric semantics that people can program
> >>>>>>>> against.
> >>>>>>>>
> >>>>>>>> 2. Sometimes the same metric semantic can be exposed using
> >>>>>>>> different metric types / interfaces.
> >>>>>>>> This is a good point. Counter and Gauge-as-a-Counter are pretty
> >>>>>>>> much interchangeable. This is more of a trade-off between the
> >>>>> user
> >>>>>>>> experience of metric producers and consumers. The metric
> >>>>> producers
> >>>>>>>> want to use Counter or Gauge depending on whether the counter is
> >>>>>>>> already tracked in code, while ideally the metric consumers only
> >>>>>>>> want to see a single metric type for each metric. I am leaning
> >>>>>>>> towards to make the metric producers happy, i.e. allow Gauge /
> >>>>>>>> Counter metric type, and the the metric consumers handle the
> type
> >>>>>>>> variation. The reason is that in practice, there might be more
> >>>>>>>> connector implementations than metric reporter implementations.
> >>>>> We
> >>>>>>>> could also provide some helper method to facilitate reading from
> >>>>>>>> such variable metric type.
> >>>>>>>>
> >>>>>>>>
> >>>>>>>> Just some quick replies to the comments around implementation
> >>>>>>> details.
> >>>>>>>>
> >>>>>>>> 4) single place where metrics are registered except
> >>>>>>>> connector-specific
> >>>>>>>> ones (which we can't really avoid).
> >>>>>>>>
> >>>>>>>> Register connector specific ones in a single place is actually
> >>>>>>>> something that I want to achieve.
> >>>>>>>>
> >>>>>>>> 2) I'm talking about time-series databases like Prometheus.
> >>>>> We
> >>>>>>>> would
> >>>>>>>> only have a gauge metric exposing the last
> fetchTime/emitTime
> >>>>>>>> that is
> >>>>>>>> regularly reported to the backend (Prometheus), where a user
> >>>>>>>> could build
> >>>>>>>> a histogram of his choosing when/if he wants it.
> >>>>>>>>
> >>>>>>>> Not sure if such downsampling works. As an example, if a user
> >>>>>>>> complains that there are some intermittent latency spikes (maybe
> >>>>> a
> >>>>>>>> few records in 10 seconds) in their processing system. Having a
> >>>>>>>> Gauge sampling instantaneous latency seems unlikely useful.
> >>>>>>>> However by looking at actual 99.9 percentile latency might help.
> >>>>>>>>
> >>>>>>>> Thanks,
> >>>>>>>>
> >>>>>>>> Jiangjie (Becket) Qin
> >>>>>>>>
> >>>>>>>>
> >>>>>>>> On Fri, Feb 22, 2019 at 9:30 PM Chesnay Schepler
> >>>>>>>> <chesnay@apache.org <ma...@apache.org>> wrote:
> >>>>>>>>
> >>>>>>>> Re: over complication of implementation.
> >>>>>>>>
> >>>>>>>> I think I get understand better know what you're shooting
> >>>>> for,
> >>>>>>>> effectively something like the OperatorIOMetricGroup.
> >>>>>>>> But still, re-define setupConnectorMetrics() to accept a set
> >>>>>>>> of flags
> >>>>>>>> for counters/meters(ans _possibly_ histograms) along with a
> >>>>>>>> set of
> >>>>>>>> well-defined Optional<Gauge<?>>, and return the group.
> >>>>>>>>
> >>>>>>>> Solves all issues as far as i can tell:
> >>>>>>>> 1) no metrics must be created manually (except Gauges, which
> >>>>>> are
> >>>>>>>> effectively just Suppliers and you can't get around this),
> >>>>>>>> 2) additional metrics can be registered on the returned
> >>>>> group,
> >>>>>>>> 3) see 1),
> >>>>>>>> 4) single place where metrics are registered except
> >>>>>>>> connector-specific
> >>>>>>>> ones (which we can't really avoid).
> >>>>>>>>
> >>>>>>>> Re: Histogram
> >>>>>>>>
> >>>>>>>> 1) As an example, whether "numRecordsIn" is exposed as a
> >>>>>>>> Counter or a
> >>>>>>>> Gauge should be irrelevant. So far we're using the metric
> >>>>> type
> >>>>>>>> that is
> >>>>>>>> the most convenient at exposing a given value. If there is
> >>>>>>>> some backing
> >>>>>>>> data-structure that we want to expose some data from we
> >>>>>>>> typically opt
> >>>>>>>> for a Gauge, as otherwise we're just mucking around with the
> >>>>>>>> Meter/Counter API to get it to match. Similarly, if we want
> >>>>> to
> >>>>>>>> count
> >>>>>>>> something but no current count exists we typically added a
> >>>>>>>> Counter.
> >>>>>>>> That's why attaching semantics to metric types makes little
> >>>>>>>> sense (but
> >>>>>>>> unfortunately several reporters already do it); for
> >>>>>>>> counters/meters
> >>>>>>>> certainly, but the majority of metrics are gauges.
> >>>>>>>>
> >>>>>>>> 2) I'm talking about time-series databases like Prometheus.
> >>>>> We
> >>>>>>>> would
> >>>>>>>> only have a gauge metric exposing the last
> fetchTime/emitTime
> >>>>>>>> that is
> >>>>>>>> regularly reported to the backend (Prometheus), where a user
> >>>>>>>> could build
> >>>>>>>> a histogram of his choosing when/if he wants it.
> >>>>>>>>
> >>>>>>>> On 22.02.2019 13:57, Becket Qin wrote:
> >>>>>>>>> Hi Chesnay,
> >>>>>>>>>
> >>>>>>>>> Thanks for the explanation.
> >>>>>>>>>
> >>>>>>>>> ** Re: FLIP
> >>>>>>>>> I might have misunderstood this, but it seems that "major
> >>>>>>>> changes" are well
> >>>>>>>>> defined in FLIP. The full contents is following:
> >>>>>>>>> What is considered a "major change" that needs a FLIP?
> >>>>>>>>>
> >>>>>>>>> Any of the following should be considered a major change:
> >>>>>>>>>
> >>>>>>>>> - Any major new feature, subsystem, or piece of
> >>>>>>>> functionality
> >>>>>>>>> - *Any change that impacts the public interfaces of the
> >>>>>>>> project*
> >>>>>>>>>
> >>>>>>>>> What are the "public interfaces" of the project?
> >>>>>>>>>
> >>>>>>>>>
> >>>>>>>>>
> >>>>>>>>> *All of the following are public interfaces *that people
> >>>>>>>> build around:
> >>>>>>>>>
> >>>>>>>>> - DataStream and DataSet API, including classes related
> >>>>>>>> to that, such as
> >>>>>>>>> StreamExecutionEnvironment
> >>>>>>>>>
> >>>>>>>>>
> >>>>>>>>> - Classes marked with the @Public annotation
> >>>>>>>>>
> >>>>>>>>>
> >>>>>>>>> - On-disk binary formats, such as
> >>>>> checkpoints/savepoints
> >>>>>>>>>
> >>>>>>>>>
> >>>>>>>>> - User-facing scripts/command-line tools, i.e.
> >>>>>>>> bin/flink, Yarn scripts,
> >>>>>>>>> Mesos scripts
> >>>>>>>>>
> >>>>>>>>>
> >>>>>>>>> - Configuration settings
> >>>>>>>>>
> >>>>>>>>>
> >>>>>>>>> - *Exposed monitoring information*
> >>>>>>>>>
> >>>>>>>>>
> >>>>>>>>> So any monitoring information change is considered as
> >>>>> public
> >>>>>>>> interface, and
> >>>>>>>>> any public interface change is considered as a "major
> >>>>>> change".
> >>>>>>>>>
> >>>>>>>>>
> >>>>>>>>> ** Re: over complication of implementation.
> >>>>>>>>>
> >>>>>>>>> Although this is more of implementation details that is not
> >>>>>>>> covered by the
> >>>>>>>>> FLIP. But it may be worth discussing.
> >>>>>>>>>
> >>>>>>>>> First of all, I completely agree that we should use the
> >>>>>>>> simplest way to
> >>>>>>>>> achieve our goal. To me the goal is the following:
> >>>>>>>>> 1. Clear connector conventions and interfaces.
> >>>>>>>>> 2. The easiness of creating a connector.
> >>>>>>>>>
> >>>>>>>>> Both of them are important to the prosperity of the
> >>>>>>>> connector ecosystem. So
> >>>>>>>>> I'd rather abstract as much as possible on our side to make
> >>>>>>>> the connector
> >>>>>>>>> developer's work lighter. Given this goal, a static util
> >>>>>>>> method approach
> >>>>>>>>> might have a few drawbacks:
> >>>>>>>>> 1. Users still have to construct the metrics by themselves.
> >>>>>>>> (And note that
> >>>>>>>>> this might be erroneous by itself. For example, a customer
> >>>>>>>> wrapper around
> >>>>>>>>> dropwizard meter maybe used instead of MeterView).
> >>>>>>>>> 2. When connector specific metrics are added, it is
> >>>>>>>> difficult to enforce
> >>>>>>>>> the scope to be the same as standard metrics.
> >>>>>>>>> 3. It seems that a method proliferation is inevitable if we
> >>>>>>>> want to apply
> >>>>>>>>> sanity checks. e.g. The metric of numBytesIn was not
> >>>>>>>> registered for a meter.
> >>>>>>>>> 4. Metrics are still defined in random places and hard to
> >>>>>>> track.
> >>>>>>>>>
> >>>>>>>>> The current PR I had was inspired by the Config system in
> >>>>>>>> Kafka, which I
> >>>>>>>>> found pretty handy. In fact it is not only used by Kafka
> >>>>>>>> itself but even
> >>>>>>>>> some other projects that depend on Kafka. I am not saying
> >>>>>>>> this approach is
> >>>>>>>>> perfect. But I think it worths to save the work for
> >>>>>>>> connector writers and
> >>>>>>>>> encourage more systematic implementation. That being said,
> >>>>> I
> >>>>>>>> am fully open
> >>>>>>>>> to suggestions.
> >>>>>>>>>
> >>>>>>>>>
> >>>>>>>>> Re: Histogram
> >>>>>>>>> I think there are two orthogonal questions around those
> >>>>>>> metrics:
> >>>>>>>>>
> >>>>>>>>> 1. Regardless of the metric type, by just looking at the
> >>>>>>>> meaning of a
> >>>>>>>>> metric, is generic to all connectors? If the answer is yes,
> >>>>>>>> we should
> >>>>>>>>> include the metric into the convention. No matter whether
> >>>>> we
> >>>>>>>> include it
> >>>>>>>>> into the convention or not, some connector implementations
> >>>>>>>> will emit such
> >>>>>>>>> metric. It is better to have a convention than letting each
> >>>>>>>> connector do
> >>>>>>>>> random things.
> >>>>>>>>>
> >>>>>>>>> 2. If a standard metric is a histogram, what should we do?
> >>>>>>>>> I agree that we should make it clear that using histograms
> >>>>>>>> will have
> >>>>>>>>> performance risk. But I do see histogram is useful in some
> >>>>>>>> fine-granularity
> >>>>>>>>> debugging where one do not have the luxury to stop the
> >>>>>>>> system and inject
> >>>>>>>>> more inspection code. So the workaround I am thinking is to
> >>>>>>>> provide some
> >>>>>>>>> implementation suggestions. Assume later on we have a
> >>>>>>>> mechanism of
> >>>>>>>>> selective metrics. In the abstract metrics class we can
> >>>>>>>> disable those
> >>>>>>>>> metrics by default individual connector writers does not
> >>>>>>>> have to do
> >>>>>>>>> anything (this is another advantage of having an
> >>>>>>>> AbstractMetrics instead of
> >>>>>>>>> static util methods.)
> >>>>>>>>>
> >>>>>>>>> I am not sure I fully understand the histogram in the
> >>>>>>>> backend approach. Can
> >>>>>>>>> you explain a bit more? Do you mean emitting the raw data,
> >>>>>>>> e.g. fetchTime
> >>>>>>>>> and emitTime with each record and let the histogram
> >>>>>>>> computation happen in
> >>>>>>>>> the background? Or let the processing thread putting the
> >>>>>>>> values into a
> >>>>>>>>> queue and have a separate thread polling from the queue and
> >>>>>>>> add them into
> >>>>>>>>> the histogram?
> >>>>>>>>>
> >>>>>>>>> Thanks,
> >>>>>>>>>
> >>>>>>>>> Jiangjie (Becket) Qin
> >>>>>>>>>
> >>>>>>>>>
> >>>>>>>>>
> >>>>>>>>>
> >>>>>>>>>
> >>>>>>>>> On Fri, Feb 22, 2019 at 4:34 PM Chesnay Schepler
> >>>>>>>> <chesnay@apache.org <ma...@apache.org>> wrote:
> >>>>>>>>>
> >>>>>>>>>> Re: Flip
> >>>>>>>>>> The very first line under both the main header and Purpose
> >>>>>>>> section
> >>>>>>>>>> describe Flips as "major changes", which this isn't.
> >>>>>>>>>>
> >>>>>>>>>> Re: complication
> >>>>>>>>>> I'm not arguing against standardization, but again an
> >>>>>>>> over-complicated
> >>>>>>>>>> implementation when a static utility method would be
> >>>>>>>> sufficient.
> >>>>>>>>>>
> >>>>>>>>>> public static void setupConnectorMetrics(
> >>>>>>>>>> MetricGroup operatorMetricGroup,
> >>>>>>>>>> String connectorName,
> >>>>>>>>>> Optional<Gauge<Long>> numRecordsIn,
> >>>>>>>>>> ...)
> >>>>>>>>>>
> >>>>>>>>>> This gives you all you need:
> >>>>>>>>>> * a well-defined set of metrics for a connector to opt-in
> >>>>>>>>>> * standardized naming schemes for scope and individual
> >>>>>> metrics
> >>>>>>>>>> * standardize metric types (although personally I'm not
> >>>>>>>> interested in that
> >>>>>>>>>> since metric types should be considered syntactic sugar)
> >>>>>>>>>>
> >>>>>>>>>> Re: Configurable Histogram
> >>>>>>>>>> If anything they _must_ be turned off by default, but the
> >>>>>>>> metric system is
> >>>>>>>>>> already exposing so many options that I'm not too keen on
> >>>>>>>> adding even more.
> >>>>>>>>>> You have also only addressed my first argument against
> >>>>>>>> histograms
> >>>>>>>>>> (performance), the second one still stands (calculate
> >>>>>>>> histogram in metric
> >>>>>>>>>> backends instead).
> >>>>>>>>>>
> >>>>>>>>>> On 21.02.2019 16:27, Becket Qin wrote:
> >>>>>>>>>>> Hi Chesnay,
> >>>>>>>>>>>
> >>>>>>>>>>> Thanks for the comments. I think this is worthy of a FLIP
> >>>>>>>> because it is
> >>>>>>>>>>> public API. According to the FLIP description a FlIP is
> >>>>>>>> required in case
> >>>>>>>>>> of:
> >>>>>>>>>>> - Any change that impacts the public interfaces of
> >>>>>>>> the project
> >>>>>>>>>>>
> >>>>>>>>>>> and the following entry is found in the definition of
> >>>>>>>> "public interface".
> >>>>>>>>>>>
> >>>>>>>>>>> - Exposed monitoring information
> >>>>>>>>>>>
> >>>>>>>>>>> Metrics are critical to any production system. So a clear
> >>>>>>>> metric
> >>>>>>>>>> definition
> >>>>>>>>>>> is important for any serious users. For an organization
> >>>>>>>> with large Flink
> >>>>>>>>>>> installation, change in metrics means great amount of
> >>>>>>>> work. So such
> >>>>>>>>>> changes
> >>>>>>>>>>> do need to be fully discussed and documented.
> >>>>>>>>>>>
> >>>>>>>>>>> ** Re: Histogram.
> >>>>>>>>>>> We can discuss whether there is a better way to expose
> >>>>>>>> metrics that are
> >>>>>>>>>>> suitable for histograms. My micro-benchmark on various
> >>>>>>>> histogram
> >>>>>>>>>>> implementations also indicates that they are
> >>>>> significantly
> >>>>>>>> slower than
> >>>>>>>>>>> other metric types. But I don't think that means never
> >>>>> use
> >>>>>>>> histogram, but
> >>>>>>>>>>> means use it with caution. For example, we can suggest
> >>>>> the
> >>>>>>>>>> implementations
> >>>>>>>>>>> to turn them off by default and only turn it on for a
> >>>>>>>> small amount of
> >>>>>>>>>> time
> >>>>>>>>>>> when performing some micro-debugging.
> >>>>>>>>>>>
> >>>>>>>>>>> ** Re: complication:
> >>>>>>>>>>> Connector conventions are essential for Flink ecosystem.
> >>>>>>>> Flink connectors
> >>>>>>>>>>> pool is probably the most important part of Flink, just
> >>>>>>>> like any other
> >>>>>>>>>> data
> >>>>>>>>>>> system. Clear conventions of connectors will help build
> >>>>>>>> Flink ecosystem
> >>>>>>>>>> in
> >>>>>>>>>>> a more organic way.
> >>>>>>>>>>> Take the metrics convention as an example, imagine
> >>>>> someone
> >>>>>>>> has developed
> >>>>>>>>>> a
> >>>>>>>>>>> Flink connector for System foo, and another developer may
> >>>>>>>> have developed
> >>>>>>>>>> a
> >>>>>>>>>>> monitoring and diagnostic framework for Flink which
> >>>>>>>> analyzes the Flink
> >>>>>>>>>> job
> >>>>>>>>>>> performance based on metrics. With a clear metric
> >>>>>>>> convention, those two
> >>>>>>>>>>> projects could be developed independently. Once users put
> >>>>>>>> them together,
> >>>>>>>>>>> it would work without additional modifications. This
> >>>>>>>> cannot be easily
> >>>>>>>>>>> achieved by just defining a few constants.
> >>>>>>>>>>>
> >>>>>>>>>>> ** Re: selective metrics:
> >>>>>>>>>>> Sure, we can discuss that in a separate thread.
> >>>>>>>>>>>
> >>>>>>>>>>> @Dawid
> >>>>>>>>>>>
> >>>>>>>>>>> ** Re: latency / fetchedLatency
> >>>>>>>>>>> The primary purpose of establish such a convention is to
> >>>>>>>> help developers
> >>>>>>>>>>> write connectors in a more compatible way. The convention
> >>>>>>>> is supposed to
> >>>>>>>>>> be
> >>>>>>>>>>> defined more proactively. So when look at the convention,
> >>>>>>>> it seems more
> >>>>>>>>>>> important to see if the concept is applicable to
> >>>>>>>> connectors in general.
> >>>>>>>>>> It
> >>>>>>>>>>> might be true so far only Kafka connector reports
> >>>>> latency.
> >>>>>>>> But there
> >>>>>>>>>> might
> >>>>>>>>>>> be hundreds of other connector implementations in the
> >>>>>>>> Flink ecosystem,
> >>>>>>>>>>> though not in the Flink repo, and some of them also emits
> >>>>>>>> latency. I
> >>>>>>>>>> think
> >>>>>>>>>>> a lot of other sources actually also has an append
> >>>>>>>> timestamp. e.g.
> >>>>>>>>>> database
> >>>>>>>>>>> bin logs and some K-V stores. So I wouldn't be surprised
> >>>>>>>> if some database
> >>>>>>>>>>> connector can also emit latency metrics.
> >>>>>>>>>>>
> >>>>>>>>>>> Thanks,
> >>>>>>>>>>>
> >>>>>>>>>>> Jiangjie (Becket) Qin
> >>>>>>>>>>>
> >>>>>>>>>>>
> >>>>>>>>>>> On Thu, Feb 21, 2019 at 10:14 PM Chesnay Schepler
> >>>>>>>> <chesnay@apache.org <ma...@apache.org>>
> >>>>>>>>>>> wrote:
> >>>>>>>>>>>
> >>>>>>>>>>>> Regarding 2) It doesn't make sense to investigate this
> >>>>> as
> >>>>>>>> part of this
> >>>>>>>>>>>> FLIP. This is something that could be of interest for
> >>>>> the
> >>>>>>>> entire metric
> >>>>>>>>>>>> system, and should be designed for as such.
> >>>>>>>>>>>>
> >>>>>>>>>>>> Regarding the proposal as a whole:
> >>>>>>>>>>>>
> >>>>>>>>>>>> Histogram metrics shall not be added to the core of
> >>>>>>>> Flink. They are
> >>>>>>>>>>>> significantly more expensive than other metrics, and
> >>>>>>>> calculating
> >>>>>>>>>>>> histograms in the application is regarded as an
> >>>>>>>> anti-pattern by several
> >>>>>>>>>>>> metric backends, who instead recommend to expose the raw
> >>>>>>>> data and
> >>>>>>>>>>>> calculate the histogram in the backend.
> >>>>>>>>>>>>
> >>>>>>>>>>>> Second, this seems overly complicated. Given that we
> >>>>>>>> already established
> >>>>>>>>>>>> that not all connectors will export all metrics we are
> >>>>>>>> effectively
> >>>>>>>>>>>> reducing this down to a consistent naming scheme. We
> >>>>>>>> don't need anything
> >>>>>>>>>>>> sophisticated for that; basically just a few constants
> >>>>>>>> that all
> >>>>>>>>>>>> connectors use.
> >>>>>>>>>>>>
> >>>>>>>>>>>> I'm not convinced that this is worthy of a FLIP.
> >>>>>>>>>>>>
> >>>>>>>>>>>> On 21.02.2019 14:26, Dawid Wysakowicz wrote:
> >>>>>>>>>>>>> Hi,
> >>>>>>>>>>>>>
> >>>>>>>>>>>>> Ad 1. In general I undestand and I agree. But those
> >>>>>>>> particular metrics
> >>>>>>>>>>>>> (latency, fetchLatency), right now would only be
> >>>>>>>> reported if user uses
> >>>>>>>>>>>>> KafkaConsumer with internal timestampAssigner with
> >>>>>>>> StreamCharacteristic
> >>>>>>>>>>>>> set to EventTime, right? That sounds like a very
> >>>>>>>> specific case. I am
> >>>>>>>>>> not
> >>>>>>>>>>>>> sure if we should introduce a generic metric that will
> >>>>> be
> >>>>>>>>>>>>> disabled/absent for most of implementations.
> >>>>>>>>>>>>>
> >>>>>>>>>>>>> Ad.2 That sounds like an orthogonal issue, that might
> >>>>>>>> make sense to
> >>>>>>>>>>>>> investigate in the future.
> >>>>>>>>>>>>>
> >>>>>>>>>>>>> Best,
> >>>>>>>>>>>>>
> >>>>>>>>>>>>> Dawid
> >>>>>>>>>>>>>
> >>>>>>>>>>>>> On 21/02/2019 13:20, Becket Qin wrote:
> >>>>>>>>>>>>>> Hi Dawid,
> >>>>>>>>>>>>>>
> >>>>>>>>>>>>>> Thanks for the feedback. That makes sense to me. There
> >>>>>>>> are two cases
> >>>>>>>>>> to
> >>>>>>>>>>>> be
> >>>>>>>>>>>>>> addressed.
> >>>>>>>>>>>>>>
> >>>>>>>>>>>>>> 1. The metrics are supposed to be a guidance. It is
> >>>>>>>> likely that a
> >>>>>>>>>>>> connector
> >>>>>>>>>>>>>> only supports some but not all of the metrics. In that
> >>>>>>>> case, each
> >>>>>>>>>>>> connector
> >>>>>>>>>>>>>> implementation should have the freedom to decide which
> >>>>>>>> metrics are
> >>>>>>>>>>>>>> reported. For the metrics that are supported, the
> >>>>>>>> guidance should be
> >>>>>>>>>>>>>> followed.
> >>>>>>>>>>>>>>
> >>>>>>>>>>>>>> 2. Sometimes users may want to disable certain metrics
> >>>>>>>> for some reason
> >>>>>>>>>>>>>> (e.g. performance / reprocessing of data). A generic
> >>>>>>>> mechanism should
> >>>>>>>>>> be
> >>>>>>>>>>>>>> provided to allow user choose which metrics are
> >>>>>>>> reported. This
> >>>>>>>>>> mechanism
> >>>>>>>>>>>>>> should also be honored by the connector
> >>>>> implementations.
> >>>>>>>>>>>>>>
> >>>>>>>>>>>>>> Does this sound reasonable to you?
> >>>>>>>>>>>>>>
> >>>>>>>>>>>>>> Thanks,
> >>>>>>>>>>>>>>
> >>>>>>>>>>>>>> Jiangjie (Becket) Qin
> >>>>>>>>>>>>>>
> >>>>>>>>>>>>>>
> >>>>>>>>>>>>>>
> >>>>>>>>>>>>>> On Thu, Feb 21, 2019 at 4:22 PM Dawid Wysakowicz <
> >>>>>>>>>>>> dwysakowicz@apache.org <ma...@apache.org>>
> >>>>>>>>>>>>>> wrote:
> >>>>>>>>>>>>>>
> >>>>>>>>>>>>>>> Hi,
> >>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>> Generally I like the idea of having a unified,
> >>>>>>>> standard set of
> >>>>>>>>>> metrics
> >>>>>>>>>>>> for
> >>>>>>>>>>>>>>> all connectors. I have some slight concerns about
> >>>>>>>> fetchLatency and
> >>>>>>>>>>>>>>> latency though. They are computed based on EventTime
> >>>>>>>> which is not a
> >>>>>>>>>>>> purely
> >>>>>>>>>>>>>>> technical feature. It depends often on some business
> >>>>>>>> logic, might be
> >>>>>>>>>>>> absent
> >>>>>>>>>>>>>>> or defined after source. Those metrics could also
> >>>>>>>> behave in a weird
> >>>>>>>>>>>> way in
> >>>>>>>>>>>>>>> case of replaying backlog. Therefore I am not sure if
> >>>>>>>> we should
> >>>>>>>>>> include
> >>>>>>>>>>>>>>> those metrics by default. Maybe we could at least
> >>>>>>>> introduce a feature
> >>>>>>>>>>>>>>> switch for them? What do you think?
> >>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>> Best,
> >>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>> Dawid
> >>>>>>>>>>>>>>> On 21/02/2019 03:13, Becket Qin wrote:
> >>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>> Bump. If there is no objections to the proposed
> >>>>>>>> metrics. I'll start a
> >>>>>>>>>>>>>>> voting thread later toady.
> >>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>> Thanks,
> >>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>> Jiangjie (Becket) Qin
> >>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>> On Mon, Feb 11, 2019 at 8:17 PM Becket Qin
> >>>>>>>> <becket.qin@gmail.com <ma...@gmail.com>> <
> >>>>>>>>>>>> becket.qin@gmail.com <ma...@gmail.com>>
> >>>>>> wrote:
> >>>>>>>>>>>>>>> Hi folks,
> >>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>> I would like to start the FLIP discussion thread
> >>>>> about
> >>>>>>>> standardize
> >>>>>>>>>> the
> >>>>>>>>>>>>>>> connector metrics.
> >>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>> In short, we would like to provide a convention of
> >>>>>>>> Flink connector
> >>>>>>>>>>>>>>> metrics. It will help simplify the monitoring and
> >>>>>>>> alerting on Flink
> >>>>>>>>>>>> jobs.
> >>>>>>>>>>>>>>> The FLIP link is following:
> >>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>
> >>>>>>>>>>
> >>>>>>>>
> >>>>>>>
> >>>>>>
> >>>>>
> >>>
> https://cwiki.apache.org/confluence/display/FLINK/FLIP-33%3A+Standardize+Connector+Metrics
> >>>>>>>>>>>>>>> Thanks,
> >>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>> Jiangjie (Becket) Qin
> >>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>
> >>>>>>>>>>
> >>>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>
> >>>>>
> >>>
> >>>
>
>
>
Re: [DISCUSS] FLIP-33: Standardize connector metrics
Posted by Piotr Nowojski <pi...@ververica.com>.
Hey Becket,
Re 1a) and 1b) +1 from my side.
I’ve discussed this issue:
>>>
>>> 2. It would be nice to have metrics, that allow us to check the cause of
>>> back pressure:
>>> a) for sources, length of input queue (in bytes? Or boolean
>>> hasSomethingl/isEmpty)
>>> b) for sinks, length of output queue (in bytes? Or boolean
>>> hasSomething/isEmpty)
With Nico at some lengths and he also saw the benefits of them. We also have more concrete proposal for that.
Actually there are two really useful metrics, that we are missing currently:
1. Number of data/records/bytes in the backlog to process. For example remaining number of bytes in unread files. Or pending data in Kafka topics.
2. Number of buffered data in-memory of the connector, that are waiting to be processed pushed to Flink pipeline.
Re 1:
This would have to be a metric provided directly by a connector. It could be an undefined `int`:
`int backlog` - estimate of pending work.
“Undefined” meaning that it would be up to a connector to decided whether it’s measured in bytes, records, pending files or whatever it is possible to provide by the connector. This is because I assume not every connector can provide exact number and for some of them it might be impossible to provide records number of bytes count.
Re 2:
This metric could be either provided by a connector, or calculated crudely by Flink:
`float bufferUsage` - value from [0.0, 1.0] range
Percentage of used in memory buffers, like in Kafka’s handover.
It could be crudely implemented by Flink with FLIP-27 SourceReader#isAvailable. If SourceReader is not available reported `bufferUsage` could be 0.0. If it is available, it could be 1.0. I think this would be a good enough estimation for most of the use cases (that could be overloaded and implemented better if desired). Especially since we are reporting only probed values: if probed values are almost always “1.0”, it would mean that we have a back pressure. If they are almost always “0.0”, there is probably no back pressure at the sources.
What do you think about this?
Piotrek
> On 30 May 2019, at 11:41, Becket Qin <be...@gmail.com> wrote:
>
> Hi all,
>
> Thanks a lot for all the feedback and comments. I'd like to continue the
> discussion on this FLIP.
>
> I updated the FLIP-33 wiki to remove all the histogram metrics from the
> first version of metric convention due to the performance concern. The plan
> is to introduce them later when we have a mechanism to opt in/out metrics.
> At that point, users can decide whether they want to pay the cost to get
> the metric or not.
>
> As Stephan suggested, for this FLIP, let's first try to agree on the small
> list of conventional metrics that connectors should follow.
> Just to be clear, the purpose of the convention is not to enforce every
> connector to report all these metrics, but to provide a guidance in case
> these metrics are reported by some connectors.
>
>
> @ Stephan & Chesnay,
>
> Regarding the duplication of `RecordsIn` metric in operator / task
> IOMetricGroups, from what I understand, for source operator, it is actually
> the SourceFunction that reports the operator level
> RecordsIn/RecordsInPerSecond metric. So they are essentially the same
> metric in the operator level IOMetricGroup. Similarly for the Sink
> operator, the operator level RecordsOut/RecordsOutPerSecond metrics are
> also reported by the Sink function. I marked them as existing in the
> FLIP-33 wiki page. Please let me know if I misunderstood.
>
> Thanks,
>
> Jiangjie (Becket) Qin
>
>
> On Thu, May 30, 2019 at 5:16 PM Becket Qin <be...@gmail.com> wrote:
>
>> Hi Piotr,
>>
>> Thanks a lot for the feedback.
>>
>> 1a) I guess you are referring to the part that "original system specific
>> metrics should also be reported". The performance impact depends on the
>> implementation. An efficient implementation would only record the metric
>> once, but report them with two different metric names. This is unlikely to
>> hurt performance.
>>
>> 1b) Yes, I agree that we should avoid adding overhead to the critical path
>> by all means. This is sometimes a tradeoff, running blindly without any
>> metric gives best performance, but sometimes might be frustrating when we
>> debug some issues.
>>
>> 2. The metrics are indeed very useful. Are they supposed to be reported by
>> the connectors or Flink itself? At this point FLIP-33 is more focused on
>> provide a guidance to the connector authors on the metrics reporting. That
>> said, after FLIP-27, I think we should absolutely report these metrics in
>> the abstract implementation. In any case, the metric convention in this
>> list are expected to evolve over time.
>>
>> Thanks,
>>
>> Jiangjie (Becket) Qin
>>
>> On Tue, May 28, 2019 at 6:24 PM Piotr Nowojski <pi...@ververica.com>
>> wrote:
>>
>>> Hi,
>>>
>>> Thanks for the proposal and driving the effort here Becket :) I’ve read
>>> through the FLIP-33 [1], and here are couple of my thoughts.
>>>
>>> Big +1 for standardising the metric names between connectors, it will
>>> definitely help us and users a lot.
>>>
>>> Issues/questions/things to discuss that I’ve thought of:
>>>
>>> 1a. If we are about to duplicate some metrics, can this become a
>>> performance issue?
>>> 1b. Generally speaking, we should make sure that collecting those metrics
>>> is as non intrusive as possible, especially that they will need to be
>>> updated once per record. (They might be collected more rarely with some
>>> overhead, but the hot path of updating it per record will need to be as
>>> quick as possible). That includes both avoiding heavy computation on per
>>> record path: histograms?, measuring time for time based metrics (per
>>> second) (System.currentTimeMillis() depending on the implementation can
>>> invoke a system call)
>>>
>>> 2. It would be nice to have metrics, that allow us to check the cause of
>>> back pressure:
>>> a) for sources, length of input queue (in bytes? Or boolean
>>> hasSomethingl/isEmpty)
>>> b) for sinks, length of output queue (in bytes? Or boolean
>>> hasSomething/isEmpty)
>>>
>>> a) is useful in a scenario when we are processing backlog of records, all
>>> of the internal Flink’s input/output network buffers are empty, and we want
>>> to check whether the external source system is the bottleneck (source’s
>>> input queue will be empty), or if the Flink’s connector is the bottleneck
>>> (source’s input queues will be full).
>>> b) similar story. Backlog of records, but this time all of the internal
>>> Flink’s input/ouput network buffers are full, and we want o check whether
>>> the external sink system is the bottleneck (sink output queues are full),
>>> or if the Flink’s connector is the bottleneck (sink’s output queues will be
>>> empty)
>>>
>>> It might be sometimes difficult to provide those metrics, so they could
>>> be optional, but if we could provide them, it would be really helpful.
>>>
>>> Piotrek
>>>
>>> [1]
>>> https://cwiki.apache.org/confluence/display/FLINK/FLIP-33:+Standardize+Connector+Metrics
>>> <
>>> https://cwiki.apache.org/confluence/display/FLINK/FLIP-33:+Standardize+Connector+Metrics
>>>>
>>>
>>>> On 24 Apr 2019, at 13:28, Stephan Ewen <se...@apache.org> wrote:
>>>>
>>>> I think this sounds reasonable.
>>>>
>>>> Let's keep the "reconfiguration without stopping the job" out of this,
>>>> because that would be a super big effort and if we approach that, then
>>> in
>>>> more generic way rather than specific to connector metrics.
>>>>
>>>> I would suggest to look at the following things before starting with any
>>>> implementation work:
>>>>
>>>> - Try and find a committer to support this, otherwise it will be hard
>>> to
>>>> make progress
>>>> - Start with defining a smaller set of "core metrics" and extend the
>>> set
>>>> later. I think that is easier than now blocking on reaching consensus
>>> on a
>>>> large group of metrics.
>>>> - Find a solution to the problem Chesnay mentioned, that the "records
>>> in"
>>>> metric is somehow overloaded and exists already in the IO Metric group.
>>>>
>>>>
>>>> On Mon, Mar 25, 2019 at 7:16 AM Becket Qin <be...@gmail.com>
>>> wrote:
>>>>
>>>>> Hi Stephan,
>>>>>
>>>>> Thanks a lot for the feedback. All makes sense.
>>>>>
>>>>> It is a good suggestion to simply have an onRecord(numBytes, eventTime)
>>>>> method for connector writers. It should meet most of the requirements,
>>>>> individual
>>>>>
>>>>> The configurable metrics feature is something really useful,
>>> especially if
>>>>> we can somehow make it dynamically configurable without stopping the
>>> jobs.
>>>>> It might be better to make it a separate discussion because it is a
>>> more
>>>>> generic feature instead of only for connectors.
>>>>>
>>>>> So in order to make some progress, in this FLIP we can limit the
>>> discussion
>>>>> scope to the connector related items:
>>>>>
>>>>> - the standard connector metric names and types.
>>>>> - the abstract ConnectorMetricHandler interface
>>>>>
>>>>> I'll start a separate thread to discuss other general metric related
>>>>> enhancement items including:
>>>>>
>>>>> - optional metrics
>>>>> - dynamic metric configuration
>>>>> - potential combination with rate limiter
>>>>>
>>>>> Does this plan sound reasonable?
>>>>>
>>>>> Thanks,
>>>>>
>>>>> Jiangjie (Becket) Qin
>>>>>
>>>>> On Sat, Mar 23, 2019 at 5:53 AM Stephan Ewen <se...@apache.org> wrote:
>>>>>
>>>>>> Ignoring for a moment implementation details, this connector metrics
>>> work
>>>>>> is a really good thing to do, in my opinion
>>>>>>
>>>>>> The questions "oh, my job seems to be doing nothing, I am looking at
>>> the
>>>>> UI
>>>>>> and the 'records in' value is still zero" is in the top three support
>>>>>> questions I have been asked personally.
>>>>>> Introspection into "how far is the consumer lagging behind" (event
>>> time
>>>>>> fetch latency) came up many times as well.
>>>>>>
>>>>>> So big +1 to solving this problem.
>>>>>>
>>>>>> About the exact design - I would try to go for the following
>>> properties:
>>>>>>
>>>>>> - keep complexity of of connectors. Ideally the metrics handler has a
>>>>>> single onRecord(numBytes, eventTime) method or so, and everything
>>> else is
>>>>>> internal to the handler. That makes it dead simple for the connector.
>>> We
>>>>>> can also think of an extensive scheme for connector specific metrics.
>>>>>>
>>>>>> - make it configurable on the job it cluster level which metrics the
>>>>>> handler internally creates when that method is invoked.
>>>>>>
>>>>>> What do you think?
>>>>>>
>>>>>> Best,
>>>>>> Stephan
>>>>>>
>>>>>>
>>>>>> On Thu, Mar 21, 2019 at 10:42 AM Chesnay Schepler <chesnay@apache.org
>>>>
>>>>>> wrote:
>>>>>>
>>>>>>> As I said before, I believe this to be over-engineered and have no
>>>>>>> interest in this implementation.
>>>>>>>
>>>>>>> There are conceptual issues like defining a duplicate
>>>>> numBytesIn(PerSec)
>>>>>>> metric that already exists for each operator.
>>>>>>>
>>>>>>> On 21.03.2019 06:13, Becket Qin wrote:
>>>>>>>> A few updates to the thread. I uploaded a patch[1] as a complete
>>>>>>>> example of how users can use the metrics in the future.
>>>>>>>>
>>>>>>>> Some thoughts below after taking a look at the AbstractMetricGroup
>>>>> and
>>>>>>>> its subclasses.
>>>>>>>>
>>>>>>>> This patch intends to provide convenience for Flink connector
>>>>>>>> implementations to follow metrics standards proposed in FLIP-33. It
>>>>>>>> also try to enhance the metric management in general way to help
>>>>> users
>>>>>>>> with:
>>>>>>>>
>>>>>>>> 1. metric definition
>>>>>>>> 2. metric dependencies check
>>>>>>>> 3. metric validation
>>>>>>>> 4. metric control (turn on / off particular metrics)
>>>>>>>>
>>>>>>>> This patch wraps |MetricGroup| to extend the functionality of
>>>>>>>> |AbstractMetricGroup| and its subclasses. The
>>>>>>>> |AbstractMetricGroup| mainly focus on the metric group hierarchy,
>>> but
>>>>>>>> does not really manage the metrics other than keeping them in a Map.
>>>>>>>>
>>>>>>>> Ideally we should only have one entry point for the metrics.
>>>>>>>>
>>>>>>>> Right now the entry point is |AbstractMetricGroup|. However, besides
>>>>>>>> the missing functionality mentioned above, |AbstractMetricGroup|
>>>>> seems
>>>>>>>> deeply rooted in Flink runtime. We could extract it out to
>>>>>>>> flink-metrics in order to use it for generic purpose. There will be
>>>>>>>> some work, though.
>>>>>>>>
>>>>>>>> Another approach is to make |AbstractMetrics| in this patch as the
>>>>>>>> metric entry point. It wraps metric group and provides the missing
>>>>>>>> functionalities. Then we can roll out this pattern to runtime
>>>>>>>> components gradually as well.
>>>>>>>>
>>>>>>>> My first thought is that the latter approach gives a more smooth
>>>>>>>> migration. But I am also OK with doing a refactoring on the
>>>>>>>> |AbstractMetricGroup| family.
>>>>>>>>
>>>>>>>>
>>>>>>>> Thanks,
>>>>>>>>
>>>>>>>> Jiangjie (Becket) Qin
>>>>>>>>
>>>>>>>> [1] https://github.com/becketqin/flink/pull/1
>>>>>>>>
>>>>>>>> On Mon, Feb 25, 2019 at 2:32 PM Becket Qin <becket.qin@gmail.com
>>>>>>>> <ma...@gmail.com>> wrote:
>>>>>>>>
>>>>>>>> Hi Chesnay,
>>>>>>>>
>>>>>>>> It might be easier to discuss some implementation details in the
>>>>>>>> PR review instead of in the FLIP discussion thread. I have a
>>>>> patch
>>>>>>>> for Kafka connectors ready but haven't submitted the PR yet.
>>>>>>>> Hopefully that will help explain a bit more.
>>>>>>>>
>>>>>>>> ** Re: metric type binding
>>>>>>>> This is a valid point that worths discussing. If I understand
>>>>>>>> correctly, there are two points:
>>>>>>>>
>>>>>>>> 1. Metric type / interface does not matter as long as the metric
>>>>>>>> semantic is clearly defined.
>>>>>>>> Conceptually speaking, I agree that as long as the metric
>>>>> semantic
>>>>>>>> is defined, metric type does not matter. To some extent, Gauge /
>>>>>>>> Counter / Meter / Histogram themselves can be think of as some
>>>>>>>> well-recognized semantics, if you wish. In Flink, these metric
>>>>>>>> semantics have their associated interface classes. In practice,
>>>>>>>> such semantic to interface binding seems necessary for different
>>>>>>>> components to communicate. Simply standardize the semantic of
>>>>> the
>>>>>>>> connector metrics seems not sufficient for people to build
>>>>>>>> ecosystem on top of. At the end of the day, we still need to have
>>>>>>>> some embodiment of the metric semantics that people can program
>>>>>>>> against.
>>>>>>>>
>>>>>>>> 2. Sometimes the same metric semantic can be exposed using
>>>>>>>> different metric types / interfaces.
>>>>>>>> This is a good point. Counter and Gauge-as-a-Counter are pretty
>>>>>>>> much interchangeable. This is more of a trade-off between the
>>>>> user
>>>>>>>> experience of metric producers and consumers. The metric
>>>>> producers
>>>>>>>> want to use Counter or Gauge depending on whether the counter is
>>>>>>>> already tracked in code, while ideally the metric consumers only
>>>>>>>> want to see a single metric type for each metric. I am leaning
>>>>>>>> towards to make the metric producers happy, i.e. allow Gauge /
>>>>>>>> Counter metric type, and the the metric consumers handle the type
>>>>>>>> variation. The reason is that in practice, there might be more
>>>>>>>> connector implementations than metric reporter implementations.
>>>>> We
>>>>>>>> could also provide some helper method to facilitate reading from
>>>>>>>> such variable metric type.
>>>>>>>>
>>>>>>>>
>>>>>>>> Just some quick replies to the comments around implementation
>>>>>>> details.
>>>>>>>>
>>>>>>>> 4) single place where metrics are registered except
>>>>>>>> connector-specific
>>>>>>>> ones (which we can't really avoid).
>>>>>>>>
>>>>>>>> Register connector specific ones in a single place is actually
>>>>>>>> something that I want to achieve.
>>>>>>>>
>>>>>>>> 2) I'm talking about time-series databases like Prometheus.
>>>>> We
>>>>>>>> would
>>>>>>>> only have a gauge metric exposing the last fetchTime/emitTime
>>>>>>>> that is
>>>>>>>> regularly reported to the backend (Prometheus), where a user
>>>>>>>> could build
>>>>>>>> a histogram of his choosing when/if he wants it.
>>>>>>>>
>>>>>>>> Not sure if such downsampling works. As an example, if a user
>>>>>>>> complains that there are some intermittent latency spikes (maybe
>>>>> a
>>>>>>>> few records in 10 seconds) in their processing system. Having a
>>>>>>>> Gauge sampling instantaneous latency seems unlikely useful.
>>>>>>>> However by looking at actual 99.9 percentile latency might help.
>>>>>>>>
>>>>>>>> Thanks,
>>>>>>>>
>>>>>>>> Jiangjie (Becket) Qin
>>>>>>>>
>>>>>>>>
>>>>>>>> On Fri, Feb 22, 2019 at 9:30 PM Chesnay Schepler
>>>>>>>> <chesnay@apache.org <ma...@apache.org>> wrote:
>>>>>>>>
>>>>>>>> Re: over complication of implementation.
>>>>>>>>
>>>>>>>> I think I get understand better know what you're shooting
>>>>> for,
>>>>>>>> effectively something like the OperatorIOMetricGroup.
>>>>>>>> But still, re-define setupConnectorMetrics() to accept a set
>>>>>>>> of flags
>>>>>>>> for counters/meters(ans _possibly_ histograms) along with a
>>>>>>>> set of
>>>>>>>> well-defined Optional<Gauge<?>>, and return the group.
>>>>>>>>
>>>>>>>> Solves all issues as far as i can tell:
>>>>>>>> 1) no metrics must be created manually (except Gauges, which
>>>>>> are
>>>>>>>> effectively just Suppliers and you can't get around this),
>>>>>>>> 2) additional metrics can be registered on the returned
>>>>> group,
>>>>>>>> 3) see 1),
>>>>>>>> 4) single place where metrics are registered except
>>>>>>>> connector-specific
>>>>>>>> ones (which we can't really avoid).
>>>>>>>>
>>>>>>>> Re: Histogram
>>>>>>>>
>>>>>>>> 1) As an example, whether "numRecordsIn" is exposed as a
>>>>>>>> Counter or a
>>>>>>>> Gauge should be irrelevant. So far we're using the metric
>>>>> type
>>>>>>>> that is
>>>>>>>> the most convenient at exposing a given value. If there is
>>>>>>>> some backing
>>>>>>>> data-structure that we want to expose some data from we
>>>>>>>> typically opt
>>>>>>>> for a Gauge, as otherwise we're just mucking around with the
>>>>>>>> Meter/Counter API to get it to match. Similarly, if we want
>>>>> to
>>>>>>>> count
>>>>>>>> something but no current count exists we typically added a
>>>>>>>> Counter.
>>>>>>>> That's why attaching semantics to metric types makes little
>>>>>>>> sense (but
>>>>>>>> unfortunately several reporters already do it); for
>>>>>>>> counters/meters
>>>>>>>> certainly, but the majority of metrics are gauges.
>>>>>>>>
>>>>>>>> 2) I'm talking about time-series databases like Prometheus.
>>>>> We
>>>>>>>> would
>>>>>>>> only have a gauge metric exposing the last fetchTime/emitTime
>>>>>>>> that is
>>>>>>>> regularly reported to the backend (Prometheus), where a user
>>>>>>>> could build
>>>>>>>> a histogram of his choosing when/if he wants it.
>>>>>>>>
>>>>>>>> On 22.02.2019 13:57, Becket Qin wrote:
>>>>>>>>> Hi Chesnay,
>>>>>>>>>
>>>>>>>>> Thanks for the explanation.
>>>>>>>>>
>>>>>>>>> ** Re: FLIP
>>>>>>>>> I might have misunderstood this, but it seems that "major
>>>>>>>> changes" are well
>>>>>>>>> defined in FLIP. The full contents is following:
>>>>>>>>> What is considered a "major change" that needs a FLIP?
>>>>>>>>>
>>>>>>>>> Any of the following should be considered a major change:
>>>>>>>>>
>>>>>>>>> - Any major new feature, subsystem, or piece of
>>>>>>>> functionality
>>>>>>>>> - *Any change that impacts the public interfaces of the
>>>>>>>> project*
>>>>>>>>>
>>>>>>>>> What are the "public interfaces" of the project?
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> *All of the following are public interfaces *that people
>>>>>>>> build around:
>>>>>>>>>
>>>>>>>>> - DataStream and DataSet API, including classes related
>>>>>>>> to that, such as
>>>>>>>>> StreamExecutionEnvironment
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> - Classes marked with the @Public annotation
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> - On-disk binary formats, such as
>>>>> checkpoints/savepoints
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> - User-facing scripts/command-line tools, i.e.
>>>>>>>> bin/flink, Yarn scripts,
>>>>>>>>> Mesos scripts
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> - Configuration settings
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> - *Exposed monitoring information*
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> So any monitoring information change is considered as
>>>>> public
>>>>>>>> interface, and
>>>>>>>>> any public interface change is considered as a "major
>>>>>> change".
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> ** Re: over complication of implementation.
>>>>>>>>>
>>>>>>>>> Although this is more of implementation details that is not
>>>>>>>> covered by the
>>>>>>>>> FLIP. But it may be worth discussing.
>>>>>>>>>
>>>>>>>>> First of all, I completely agree that we should use the
>>>>>>>> simplest way to
>>>>>>>>> achieve our goal. To me the goal is the following:
>>>>>>>>> 1. Clear connector conventions and interfaces.
>>>>>>>>> 2. The easiness of creating a connector.
>>>>>>>>>
>>>>>>>>> Both of them are important to the prosperity of the
>>>>>>>> connector ecosystem. So
>>>>>>>>> I'd rather abstract as much as possible on our side to make
>>>>>>>> the connector
>>>>>>>>> developer's work lighter. Given this goal, a static util
>>>>>>>> method approach
>>>>>>>>> might have a few drawbacks:
>>>>>>>>> 1. Users still have to construct the metrics by themselves.
>>>>>>>> (And note that
>>>>>>>>> this might be erroneous by itself. For example, a customer
>>>>>>>> wrapper around
>>>>>>>>> dropwizard meter maybe used instead of MeterView).
>>>>>>>>> 2. When connector specific metrics are added, it is
>>>>>>>> difficult to enforce
>>>>>>>>> the scope to be the same as standard metrics.
>>>>>>>>> 3. It seems that a method proliferation is inevitable if we
>>>>>>>> want to apply
>>>>>>>>> sanity checks. e.g. The metric of numBytesIn was not
>>>>>>>> registered for a meter.
>>>>>>>>> 4. Metrics are still defined in random places and hard to
>>>>>>> track.
>>>>>>>>>
>>>>>>>>> The current PR I had was inspired by the Config system in
>>>>>>>> Kafka, which I
>>>>>>>>> found pretty handy. In fact it is not only used by Kafka
>>>>>>>> itself but even
>>>>>>>>> some other projects that depend on Kafka. I am not saying
>>>>>>>> this approach is
>>>>>>>>> perfect. But I think it worths to save the work for
>>>>>>>> connector writers and
>>>>>>>>> encourage more systematic implementation. That being said,
>>>>> I
>>>>>>>> am fully open
>>>>>>>>> to suggestions.
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> Re: Histogram
>>>>>>>>> I think there are two orthogonal questions around those
>>>>>>> metrics:
>>>>>>>>>
>>>>>>>>> 1. Regardless of the metric type, by just looking at the
>>>>>>>> meaning of a
>>>>>>>>> metric, is generic to all connectors? If the answer is yes,
>>>>>>>> we should
>>>>>>>>> include the metric into the convention. No matter whether
>>>>> we
>>>>>>>> include it
>>>>>>>>> into the convention or not, some connector implementations
>>>>>>>> will emit such
>>>>>>>>> metric. It is better to have a convention than letting each
>>>>>>>> connector do
>>>>>>>>> random things.
>>>>>>>>>
>>>>>>>>> 2. If a standard metric is a histogram, what should we do?
>>>>>>>>> I agree that we should make it clear that using histograms
>>>>>>>> will have
>>>>>>>>> performance risk. But I do see histogram is useful in some
>>>>>>>> fine-granularity
>>>>>>>>> debugging where one do not have the luxury to stop the
>>>>>>>> system and inject
>>>>>>>>> more inspection code. So the workaround I am thinking is to
>>>>>>>> provide some
>>>>>>>>> implementation suggestions. Assume later on we have a
>>>>>>>> mechanism of
>>>>>>>>> selective metrics. In the abstract metrics class we can
>>>>>>>> disable those
>>>>>>>>> metrics by default individual connector writers does not
>>>>>>>> have to do
>>>>>>>>> anything (this is another advantage of having an
>>>>>>>> AbstractMetrics instead of
>>>>>>>>> static util methods.)
>>>>>>>>>
>>>>>>>>> I am not sure I fully understand the histogram in the
>>>>>>>> backend approach. Can
>>>>>>>>> you explain a bit more? Do you mean emitting the raw data,
>>>>>>>> e.g. fetchTime
>>>>>>>>> and emitTime with each record and let the histogram
>>>>>>>> computation happen in
>>>>>>>>> the background? Or let the processing thread putting the
>>>>>>>> values into a
>>>>>>>>> queue and have a separate thread polling from the queue and
>>>>>>>> add them into
>>>>>>>>> the histogram?
>>>>>>>>>
>>>>>>>>> Thanks,
>>>>>>>>>
>>>>>>>>> Jiangjie (Becket) Qin
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> On Fri, Feb 22, 2019 at 4:34 PM Chesnay Schepler
>>>>>>>> <chesnay@apache.org <ma...@apache.org>> wrote:
>>>>>>>>>
>>>>>>>>>> Re: Flip
>>>>>>>>>> The very first line under both the main header and Purpose
>>>>>>>> section
>>>>>>>>>> describe Flips as "major changes", which this isn't.
>>>>>>>>>>
>>>>>>>>>> Re: complication
>>>>>>>>>> I'm not arguing against standardization, but again an
>>>>>>>> over-complicated
>>>>>>>>>> implementation when a static utility method would be
>>>>>>>> sufficient.
>>>>>>>>>>
>>>>>>>>>> public static void setupConnectorMetrics(
>>>>>>>>>> MetricGroup operatorMetricGroup,
>>>>>>>>>> String connectorName,
>>>>>>>>>> Optional<Gauge<Long>> numRecordsIn,
>>>>>>>>>> ...)
>>>>>>>>>>
>>>>>>>>>> This gives you all you need:
>>>>>>>>>> * a well-defined set of metrics for a connector to opt-in
>>>>>>>>>> * standardized naming schemes for scope and individual
>>>>>> metrics
>>>>>>>>>> * standardize metric types (although personally I'm not
>>>>>>>> interested in that
>>>>>>>>>> since metric types should be considered syntactic sugar)
>>>>>>>>>>
>>>>>>>>>> Re: Configurable Histogram
>>>>>>>>>> If anything they _must_ be turned off by default, but the
>>>>>>>> metric system is
>>>>>>>>>> already exposing so many options that I'm not too keen on
>>>>>>>> adding even more.
>>>>>>>>>> You have also only addressed my first argument against
>>>>>>>> histograms
>>>>>>>>>> (performance), the second one still stands (calculate
>>>>>>>> histogram in metric
>>>>>>>>>> backends instead).
>>>>>>>>>>
>>>>>>>>>> On 21.02.2019 16:27, Becket Qin wrote:
>>>>>>>>>>> Hi Chesnay,
>>>>>>>>>>>
>>>>>>>>>>> Thanks for the comments. I think this is worthy of a FLIP
>>>>>>>> because it is
>>>>>>>>>>> public API. According to the FLIP description a FlIP is
>>>>>>>> required in case
>>>>>>>>>> of:
>>>>>>>>>>> - Any change that impacts the public interfaces of
>>>>>>>> the project
>>>>>>>>>>>
>>>>>>>>>>> and the following entry is found in the definition of
>>>>>>>> "public interface".
>>>>>>>>>>>
>>>>>>>>>>> - Exposed monitoring information
>>>>>>>>>>>
>>>>>>>>>>> Metrics are critical to any production system. So a clear
>>>>>>>> metric
>>>>>>>>>> definition
>>>>>>>>>>> is important for any serious users. For an organization
>>>>>>>> with large Flink
>>>>>>>>>>> installation, change in metrics means great amount of
>>>>>>>> work. So such
>>>>>>>>>> changes
>>>>>>>>>>> do need to be fully discussed and documented.
>>>>>>>>>>>
>>>>>>>>>>> ** Re: Histogram.
>>>>>>>>>>> We can discuss whether there is a better way to expose
>>>>>>>> metrics that are
>>>>>>>>>>> suitable for histograms. My micro-benchmark on various
>>>>>>>> histogram
>>>>>>>>>>> implementations also indicates that they are
>>>>> significantly
>>>>>>>> slower than
>>>>>>>>>>> other metric types. But I don't think that means never
>>>>> use
>>>>>>>> histogram, but
>>>>>>>>>>> means use it with caution. For example, we can suggest
>>>>> the
>>>>>>>>>> implementations
>>>>>>>>>>> to turn them off by default and only turn it on for a
>>>>>>>> small amount of
>>>>>>>>>> time
>>>>>>>>>>> when performing some micro-debugging.
>>>>>>>>>>>
>>>>>>>>>>> ** Re: complication:
>>>>>>>>>>> Connector conventions are essential for Flink ecosystem.
>>>>>>>> Flink connectors
>>>>>>>>>>> pool is probably the most important part of Flink, just
>>>>>>>> like any other
>>>>>>>>>> data
>>>>>>>>>>> system. Clear conventions of connectors will help build
>>>>>>>> Flink ecosystem
>>>>>>>>>> in
>>>>>>>>>>> a more organic way.
>>>>>>>>>>> Take the metrics convention as an example, imagine
>>>>> someone
>>>>>>>> has developed
>>>>>>>>>> a
>>>>>>>>>>> Flink connector for System foo, and another developer may
>>>>>>>> have developed
>>>>>>>>>> a
>>>>>>>>>>> monitoring and diagnostic framework for Flink which
>>>>>>>> analyzes the Flink
>>>>>>>>>> job
>>>>>>>>>>> performance based on metrics. With a clear metric
>>>>>>>> convention, those two
>>>>>>>>>>> projects could be developed independently. Once users put
>>>>>>>> them together,
>>>>>>>>>>> it would work without additional modifications. This
>>>>>>>> cannot be easily
>>>>>>>>>>> achieved by just defining a few constants.
>>>>>>>>>>>
>>>>>>>>>>> ** Re: selective metrics:
>>>>>>>>>>> Sure, we can discuss that in a separate thread.
>>>>>>>>>>>
>>>>>>>>>>> @Dawid
>>>>>>>>>>>
>>>>>>>>>>> ** Re: latency / fetchedLatency
>>>>>>>>>>> The primary purpose of establish such a convention is to
>>>>>>>> help developers
>>>>>>>>>>> write connectors in a more compatible way. The convention
>>>>>>>> is supposed to
>>>>>>>>>> be
>>>>>>>>>>> defined more proactively. So when look at the convention,
>>>>>>>> it seems more
>>>>>>>>>>> important to see if the concept is applicable to
>>>>>>>> connectors in general.
>>>>>>>>>> It
>>>>>>>>>>> might be true so far only Kafka connector reports
>>>>> latency.
>>>>>>>> But there
>>>>>>>>>> might
>>>>>>>>>>> be hundreds of other connector implementations in the
>>>>>>>> Flink ecosystem,
>>>>>>>>>>> though not in the Flink repo, and some of them also emits
>>>>>>>> latency. I
>>>>>>>>>> think
>>>>>>>>>>> a lot of other sources actually also has an append
>>>>>>>> timestamp. e.g.
>>>>>>>>>> database
>>>>>>>>>>> bin logs and some K-V stores. So I wouldn't be surprised
>>>>>>>> if some database
>>>>>>>>>>> connector can also emit latency metrics.
>>>>>>>>>>>
>>>>>>>>>>> Thanks,
>>>>>>>>>>>
>>>>>>>>>>> Jiangjie (Becket) Qin
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>> On Thu, Feb 21, 2019 at 10:14 PM Chesnay Schepler
>>>>>>>> <chesnay@apache.org <ma...@apache.org>>
>>>>>>>>>>> wrote:
>>>>>>>>>>>
>>>>>>>>>>>> Regarding 2) It doesn't make sense to investigate this
>>>>> as
>>>>>>>> part of this
>>>>>>>>>>>> FLIP. This is something that could be of interest for
>>>>> the
>>>>>>>> entire metric
>>>>>>>>>>>> system, and should be designed for as such.
>>>>>>>>>>>>
>>>>>>>>>>>> Regarding the proposal as a whole:
>>>>>>>>>>>>
>>>>>>>>>>>> Histogram metrics shall not be added to the core of
>>>>>>>> Flink. They are
>>>>>>>>>>>> significantly more expensive than other metrics, and
>>>>>>>> calculating
>>>>>>>>>>>> histograms in the application is regarded as an
>>>>>>>> anti-pattern by several
>>>>>>>>>>>> metric backends, who instead recommend to expose the raw
>>>>>>>> data and
>>>>>>>>>>>> calculate the histogram in the backend.
>>>>>>>>>>>>
>>>>>>>>>>>> Second, this seems overly complicated. Given that we
>>>>>>>> already established
>>>>>>>>>>>> that not all connectors will export all metrics we are
>>>>>>>> effectively
>>>>>>>>>>>> reducing this down to a consistent naming scheme. We
>>>>>>>> don't need anything
>>>>>>>>>>>> sophisticated for that; basically just a few constants
>>>>>>>> that all
>>>>>>>>>>>> connectors use.
>>>>>>>>>>>>
>>>>>>>>>>>> I'm not convinced that this is worthy of a FLIP.
>>>>>>>>>>>>
>>>>>>>>>>>> On 21.02.2019 14:26, Dawid Wysakowicz wrote:
>>>>>>>>>>>>> Hi,
>>>>>>>>>>>>>
>>>>>>>>>>>>> Ad 1. In general I undestand and I agree. But those
>>>>>>>> particular metrics
>>>>>>>>>>>>> (latency, fetchLatency), right now would only be
>>>>>>>> reported if user uses
>>>>>>>>>>>>> KafkaConsumer with internal timestampAssigner with
>>>>>>>> StreamCharacteristic
>>>>>>>>>>>>> set to EventTime, right? That sounds like a very
>>>>>>>> specific case. I am
>>>>>>>>>> not
>>>>>>>>>>>>> sure if we should introduce a generic metric that will
>>>>> be
>>>>>>>>>>>>> disabled/absent for most of implementations.
>>>>>>>>>>>>>
>>>>>>>>>>>>> Ad.2 That sounds like an orthogonal issue, that might
>>>>>>>> make sense to
>>>>>>>>>>>>> investigate in the future.
>>>>>>>>>>>>>
>>>>>>>>>>>>> Best,
>>>>>>>>>>>>>
>>>>>>>>>>>>> Dawid
>>>>>>>>>>>>>
>>>>>>>>>>>>> On 21/02/2019 13:20, Becket Qin wrote:
>>>>>>>>>>>>>> Hi Dawid,
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> Thanks for the feedback. That makes sense to me. There
>>>>>>>> are two cases
>>>>>>>>>> to
>>>>>>>>>>>> be
>>>>>>>>>>>>>> addressed.
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> 1. The metrics are supposed to be a guidance. It is
>>>>>>>> likely that a
>>>>>>>>>>>> connector
>>>>>>>>>>>>>> only supports some but not all of the metrics. In that
>>>>>>>> case, each
>>>>>>>>>>>> connector
>>>>>>>>>>>>>> implementation should have the freedom to decide which
>>>>>>>> metrics are
>>>>>>>>>>>>>> reported. For the metrics that are supported, the
>>>>>>>> guidance should be
>>>>>>>>>>>>>> followed.
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> 2. Sometimes users may want to disable certain metrics
>>>>>>>> for some reason
>>>>>>>>>>>>>> (e.g. performance / reprocessing of data). A generic
>>>>>>>> mechanism should
>>>>>>>>>> be
>>>>>>>>>>>>>> provided to allow user choose which metrics are
>>>>>>>> reported. This
>>>>>>>>>> mechanism
>>>>>>>>>>>>>> should also be honored by the connector
>>>>> implementations.
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> Does this sound reasonable to you?
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> Thanks,
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> Jiangjie (Becket) Qin
>>>>>>>>>>>>>>
>>>>>>>>>>>>>>
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> On Thu, Feb 21, 2019 at 4:22 PM Dawid Wysakowicz <
>>>>>>>>>>>> dwysakowicz@apache.org <ma...@apache.org>>
>>>>>>>>>>>>>> wrote:
>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> Hi,
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> Generally I like the idea of having a unified,
>>>>>>>> standard set of
>>>>>>>>>> metrics
>>>>>>>>>>>> for
>>>>>>>>>>>>>>> all connectors. I have some slight concerns about
>>>>>>>> fetchLatency and
>>>>>>>>>>>>>>> latency though. They are computed based on EventTime
>>>>>>>> which is not a
>>>>>>>>>>>> purely
>>>>>>>>>>>>>>> technical feature. It depends often on some business
>>>>>>>> logic, might be
>>>>>>>>>>>> absent
>>>>>>>>>>>>>>> or defined after source. Those metrics could also
>>>>>>>> behave in a weird
>>>>>>>>>>>> way in
>>>>>>>>>>>>>>> case of replaying backlog. Therefore I am not sure if
>>>>>>>> we should
>>>>>>>>>> include
>>>>>>>>>>>>>>> those metrics by default. Maybe we could at least
>>>>>>>> introduce a feature
>>>>>>>>>>>>>>> switch for them? What do you think?
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> Best,
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> Dawid
>>>>>>>>>>>>>>> On 21/02/2019 03:13, Becket Qin wrote:
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> Bump. If there is no objections to the proposed
>>>>>>>> metrics. I'll start a
>>>>>>>>>>>>>>> voting thread later toady.
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> Thanks,
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> Jiangjie (Becket) Qin
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> On Mon, Feb 11, 2019 at 8:17 PM Becket Qin
>>>>>>>> <becket.qin@gmail.com <ma...@gmail.com>> <
>>>>>>>>>>>> becket.qin@gmail.com <ma...@gmail.com>>
>>>>>> wrote:
>>>>>>>>>>>>>>> Hi folks,
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> I would like to start the FLIP discussion thread
>>>>> about
>>>>>>>> standardize
>>>>>>>>>> the
>>>>>>>>>>>>>>> connector metrics.
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> In short, we would like to provide a convention of
>>>>>>>> Flink connector
>>>>>>>>>>>>>>> metrics. It will help simplify the monitoring and
>>>>>>>> alerting on Flink
>>>>>>>>>>>> jobs.
>>>>>>>>>>>>>>> The FLIP link is following:
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>
>>>>>>>
>>>>>>
>>>>>
>>> https://cwiki.apache.org/confluence/display/FLINK/FLIP-33%3A+Standardize+Connector+Metrics
>>>>>>>>>>>>>>> Thanks,
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> Jiangjie (Becket) Qin
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>
>>>>>
>>>
>>>
Re: [DISCUSS] FLIP-33: Standardize connector metrics
Posted by Becket Qin <be...@gmail.com>.
Hi all,
Thanks a lot for all the feedback and comments. I'd like to continue the
discussion on this FLIP.
I updated the FLIP-33 wiki to remove all the histogram metrics from the
first version of metric convention due to the performance concern. The plan
is to introduce them later when we have a mechanism to opt in/out metrics.
At that point, users can decide whether they want to pay the cost to get
the metric or not.
As Stephan suggested, for this FLIP, let's first try to agree on the small
list of conventional metrics that connectors should follow.
Just to be clear, the purpose of the convention is not to enforce every
connector to report all these metrics, but to provide a guidance in case
these metrics are reported by some connectors.
@ Stephan & Chesnay,
Regarding the duplication of `RecordsIn` metric in operator / task
IOMetricGroups, from what I understand, for source operator, it is actually
the SourceFunction that reports the operator level
RecordsIn/RecordsInPerSecond metric. So they are essentially the same
metric in the operator level IOMetricGroup. Similarly for the Sink
operator, the operator level RecordsOut/RecordsOutPerSecond metrics are
also reported by the Sink function. I marked them as existing in the
FLIP-33 wiki page. Please let me know if I misunderstood.
Thanks,
Jiangjie (Becket) Qin
On Thu, May 30, 2019 at 5:16 PM Becket Qin <be...@gmail.com> wrote:
> Hi Piotr,
>
> Thanks a lot for the feedback.
>
> 1a) I guess you are referring to the part that "original system specific
> metrics should also be reported". The performance impact depends on the
> implementation. An efficient implementation would only record the metric
> once, but report them with two different metric names. This is unlikely to
> hurt performance.
>
> 1b) Yes, I agree that we should avoid adding overhead to the critical path
> by all means. This is sometimes a tradeoff, running blindly without any
> metric gives best performance, but sometimes might be frustrating when we
> debug some issues.
>
> 2. The metrics are indeed very useful. Are they supposed to be reported by
> the connectors or Flink itself? At this point FLIP-33 is more focused on
> provide a guidance to the connector authors on the metrics reporting. That
> said, after FLIP-27, I think we should absolutely report these metrics in
> the abstract implementation. In any case, the metric convention in this
> list are expected to evolve over time.
>
> Thanks,
>
> Jiangjie (Becket) Qin
>
> On Tue, May 28, 2019 at 6:24 PM Piotr Nowojski <pi...@ververica.com>
> wrote:
>
>> Hi,
>>
>> Thanks for the proposal and driving the effort here Becket :) I’ve read
>> through the FLIP-33 [1], and here are couple of my thoughts.
>>
>> Big +1 for standardising the metric names between connectors, it will
>> definitely help us and users a lot.
>>
>> Issues/questions/things to discuss that I’ve thought of:
>>
>> 1a. If we are about to duplicate some metrics, can this become a
>> performance issue?
>> 1b. Generally speaking, we should make sure that collecting those metrics
>> is as non intrusive as possible, especially that they will need to be
>> updated once per record. (They might be collected more rarely with some
>> overhead, but the hot path of updating it per record will need to be as
>> quick as possible). That includes both avoiding heavy computation on per
>> record path: histograms?, measuring time for time based metrics (per
>> second) (System.currentTimeMillis() depending on the implementation can
>> invoke a system call)
>>
>> 2. It would be nice to have metrics, that allow us to check the cause of
>> back pressure:
>> a) for sources, length of input queue (in bytes? Or boolean
>> hasSomethingl/isEmpty)
>> b) for sinks, length of output queue (in bytes? Or boolean
>> hasSomething/isEmpty)
>>
>> a) is useful in a scenario when we are processing backlog of records, all
>> of the internal Flink’s input/output network buffers are empty, and we want
>> to check whether the external source system is the bottleneck (source’s
>> input queue will be empty), or if the Flink’s connector is the bottleneck
>> (source’s input queues will be full).
>> b) similar story. Backlog of records, but this time all of the internal
>> Flink’s input/ouput network buffers are full, and we want o check whether
>> the external sink system is the bottleneck (sink output queues are full),
>> or if the Flink’s connector is the bottleneck (sink’s output queues will be
>> empty)
>>
>> It might be sometimes difficult to provide those metrics, so they could
>> be optional, but if we could provide them, it would be really helpful.
>>
>> Piotrek
>>
>> [1]
>> https://cwiki.apache.org/confluence/display/FLINK/FLIP-33:+Standardize+Connector+Metrics
>> <
>> https://cwiki.apache.org/confluence/display/FLINK/FLIP-33:+Standardize+Connector+Metrics
>> >
>>
>> > On 24 Apr 2019, at 13:28, Stephan Ewen <se...@apache.org> wrote:
>> >
>> > I think this sounds reasonable.
>> >
>> > Let's keep the "reconfiguration without stopping the job" out of this,
>> > because that would be a super big effort and if we approach that, then
>> in
>> > more generic way rather than specific to connector metrics.
>> >
>> > I would suggest to look at the following things before starting with any
>> > implementation work:
>> >
>> > - Try and find a committer to support this, otherwise it will be hard
>> to
>> > make progress
>> > - Start with defining a smaller set of "core metrics" and extend the
>> set
>> > later. I think that is easier than now blocking on reaching consensus
>> on a
>> > large group of metrics.
>> > - Find a solution to the problem Chesnay mentioned, that the "records
>> in"
>> > metric is somehow overloaded and exists already in the IO Metric group.
>> >
>> >
>> > On Mon, Mar 25, 2019 at 7:16 AM Becket Qin <be...@gmail.com>
>> wrote:
>> >
>> >> Hi Stephan,
>> >>
>> >> Thanks a lot for the feedback. All makes sense.
>> >>
>> >> It is a good suggestion to simply have an onRecord(numBytes, eventTime)
>> >> method for connector writers. It should meet most of the requirements,
>> >> individual
>> >>
>> >> The configurable metrics feature is something really useful,
>> especially if
>> >> we can somehow make it dynamically configurable without stopping the
>> jobs.
>> >> It might be better to make it a separate discussion because it is a
>> more
>> >> generic feature instead of only for connectors.
>> >>
>> >> So in order to make some progress, in this FLIP we can limit the
>> discussion
>> >> scope to the connector related items:
>> >>
>> >> - the standard connector metric names and types.
>> >> - the abstract ConnectorMetricHandler interface
>> >>
>> >> I'll start a separate thread to discuss other general metric related
>> >> enhancement items including:
>> >>
>> >> - optional metrics
>> >> - dynamic metric configuration
>> >> - potential combination with rate limiter
>> >>
>> >> Does this plan sound reasonable?
>> >>
>> >> Thanks,
>> >>
>> >> Jiangjie (Becket) Qin
>> >>
>> >> On Sat, Mar 23, 2019 at 5:53 AM Stephan Ewen <se...@apache.org> wrote:
>> >>
>> >>> Ignoring for a moment implementation details, this connector metrics
>> work
>> >>> is a really good thing to do, in my opinion
>> >>>
>> >>> The questions "oh, my job seems to be doing nothing, I am looking at
>> the
>> >> UI
>> >>> and the 'records in' value is still zero" is in the top three support
>> >>> questions I have been asked personally.
>> >>> Introspection into "how far is the consumer lagging behind" (event
>> time
>> >>> fetch latency) came up many times as well.
>> >>>
>> >>> So big +1 to solving this problem.
>> >>>
>> >>> About the exact design - I would try to go for the following
>> properties:
>> >>>
>> >>> - keep complexity of of connectors. Ideally the metrics handler has a
>> >>> single onRecord(numBytes, eventTime) method or so, and everything
>> else is
>> >>> internal to the handler. That makes it dead simple for the connector.
>> We
>> >>> can also think of an extensive scheme for connector specific metrics.
>> >>>
>> >>> - make it configurable on the job it cluster level which metrics the
>> >>> handler internally creates when that method is invoked.
>> >>>
>> >>> What do you think?
>> >>>
>> >>> Best,
>> >>> Stephan
>> >>>
>> >>>
>> >>> On Thu, Mar 21, 2019 at 10:42 AM Chesnay Schepler <chesnay@apache.org
>> >
>> >>> wrote:
>> >>>
>> >>>> As I said before, I believe this to be over-engineered and have no
>> >>>> interest in this implementation.
>> >>>>
>> >>>> There are conceptual issues like defining a duplicate
>> >> numBytesIn(PerSec)
>> >>>> metric that already exists for each operator.
>> >>>>
>> >>>> On 21.03.2019 06:13, Becket Qin wrote:
>> >>>>> A few updates to the thread. I uploaded a patch[1] as a complete
>> >>>>> example of how users can use the metrics in the future.
>> >>>>>
>> >>>>> Some thoughts below after taking a look at the AbstractMetricGroup
>> >> and
>> >>>>> its subclasses.
>> >>>>>
>> >>>>> This patch intends to provide convenience for Flink connector
>> >>>>> implementations to follow metrics standards proposed in FLIP-33. It
>> >>>>> also try to enhance the metric management in general way to help
>> >> users
>> >>>>> with:
>> >>>>>
>> >>>>> 1. metric definition
>> >>>>> 2. metric dependencies check
>> >>>>> 3. metric validation
>> >>>>> 4. metric control (turn on / off particular metrics)
>> >>>>>
>> >>>>> This patch wraps |MetricGroup| to extend the functionality of
>> >>>>> |AbstractMetricGroup| and its subclasses. The
>> >>>>> |AbstractMetricGroup| mainly focus on the metric group hierarchy,
>> but
>> >>>>> does not really manage the metrics other than keeping them in a Map.
>> >>>>>
>> >>>>> Ideally we should only have one entry point for the metrics.
>> >>>>>
>> >>>>> Right now the entry point is |AbstractMetricGroup|. However, besides
>> >>>>> the missing functionality mentioned above, |AbstractMetricGroup|
>> >> seems
>> >>>>> deeply rooted in Flink runtime. We could extract it out to
>> >>>>> flink-metrics in order to use it for generic purpose. There will be
>> >>>>> some work, though.
>> >>>>>
>> >>>>> Another approach is to make |AbstractMetrics| in this patch as the
>> >>>>> metric entry point. It wraps metric group and provides the missing
>> >>>>> functionalities. Then we can roll out this pattern to runtime
>> >>>>> components gradually as well.
>> >>>>>
>> >>>>> My first thought is that the latter approach gives a more smooth
>> >>>>> migration. But I am also OK with doing a refactoring on the
>> >>>>> |AbstractMetricGroup| family.
>> >>>>>
>> >>>>>
>> >>>>> Thanks,
>> >>>>>
>> >>>>> Jiangjie (Becket) Qin
>> >>>>>
>> >>>>> [1] https://github.com/becketqin/flink/pull/1
>> >>>>>
>> >>>>> On Mon, Feb 25, 2019 at 2:32 PM Becket Qin <becket.qin@gmail.com
>> >>>>> <ma...@gmail.com>> wrote:
>> >>>>>
>> >>>>> Hi Chesnay,
>> >>>>>
>> >>>>> It might be easier to discuss some implementation details in the
>> >>>>> PR review instead of in the FLIP discussion thread. I have a
>> >> patch
>> >>>>> for Kafka connectors ready but haven't submitted the PR yet.
>> >>>>> Hopefully that will help explain a bit more.
>> >>>>>
>> >>>>> ** Re: metric type binding
>> >>>>> This is a valid point that worths discussing. If I understand
>> >>>>> correctly, there are two points:
>> >>>>>
>> >>>>> 1. Metric type / interface does not matter as long as the metric
>> >>>>> semantic is clearly defined.
>> >>>>> Conceptually speaking, I agree that as long as the metric
>> >> semantic
>> >>>>> is defined, metric type does not matter. To some extent, Gauge /
>> >>>>> Counter / Meter / Histogram themselves can be think of as some
>> >>>>> well-recognized semantics, if you wish. In Flink, these metric
>> >>>>> semantics have their associated interface classes. In practice,
>> >>>>> such semantic to interface binding seems necessary for different
>> >>>>> components to communicate. Simply standardize the semantic of
>> >> the
>> >>>>> connector metrics seems not sufficient for people to build
>> >>>>> ecosystem on top of. At the end of the day, we still need to have
>> >>>>> some embodiment of the metric semantics that people can program
>> >>>>> against.
>> >>>>>
>> >>>>> 2. Sometimes the same metric semantic can be exposed using
>> >>>>> different metric types / interfaces.
>> >>>>> This is a good point. Counter and Gauge-as-a-Counter are pretty
>> >>>>> much interchangeable. This is more of a trade-off between the
>> >> user
>> >>>>> experience of metric producers and consumers. The metric
>> >> producers
>> >>>>> want to use Counter or Gauge depending on whether the counter is
>> >>>>> already tracked in code, while ideally the metric consumers only
>> >>>>> want to see a single metric type for each metric. I am leaning
>> >>>>> towards to make the metric producers happy, i.e. allow Gauge /
>> >>>>> Counter metric type, and the the metric consumers handle the type
>> >>>>> variation. The reason is that in practice, there might be more
>> >>>>> connector implementations than metric reporter implementations.
>> >> We
>> >>>>> could also provide some helper method to facilitate reading from
>> >>>>> such variable metric type.
>> >>>>>
>> >>>>>
>> >>>>> Just some quick replies to the comments around implementation
>> >>>> details.
>> >>>>>
>> >>>>> 4) single place where metrics are registered except
>> >>>>> connector-specific
>> >>>>> ones (which we can't really avoid).
>> >>>>>
>> >>>>> Register connector specific ones in a single place is actually
>> >>>>> something that I want to achieve.
>> >>>>>
>> >>>>> 2) I'm talking about time-series databases like Prometheus.
>> >> We
>> >>>>> would
>> >>>>> only have a gauge metric exposing the last fetchTime/emitTime
>> >>>>> that is
>> >>>>> regularly reported to the backend (Prometheus), where a user
>> >>>>> could build
>> >>>>> a histogram of his choosing when/if he wants it.
>> >>>>>
>> >>>>> Not sure if such downsampling works. As an example, if a user
>> >>>>> complains that there are some intermittent latency spikes (maybe
>> >> a
>> >>>>> few records in 10 seconds) in their processing system. Having a
>> >>>>> Gauge sampling instantaneous latency seems unlikely useful.
>> >>>>> However by looking at actual 99.9 percentile latency might help.
>> >>>>>
>> >>>>> Thanks,
>> >>>>>
>> >>>>> Jiangjie (Becket) Qin
>> >>>>>
>> >>>>>
>> >>>>> On Fri, Feb 22, 2019 at 9:30 PM Chesnay Schepler
>> >>>>> <chesnay@apache.org <ma...@apache.org>> wrote:
>> >>>>>
>> >>>>> Re: over complication of implementation.
>> >>>>>
>> >>>>> I think I get understand better know what you're shooting
>> >> for,
>> >>>>> effectively something like the OperatorIOMetricGroup.
>> >>>>> But still, re-define setupConnectorMetrics() to accept a set
>> >>>>> of flags
>> >>>>> for counters/meters(ans _possibly_ histograms) along with a
>> >>>>> set of
>> >>>>> well-defined Optional<Gauge<?>>, and return the group.
>> >>>>>
>> >>>>> Solves all issues as far as i can tell:
>> >>>>> 1) no metrics must be created manually (except Gauges, which
>> >>> are
>> >>>>> effectively just Suppliers and you can't get around this),
>> >>>>> 2) additional metrics can be registered on the returned
>> >> group,
>> >>>>> 3) see 1),
>> >>>>> 4) single place where metrics are registered except
>> >>>>> connector-specific
>> >>>>> ones (which we can't really avoid).
>> >>>>>
>> >>>>> Re: Histogram
>> >>>>>
>> >>>>> 1) As an example, whether "numRecordsIn" is exposed as a
>> >>>>> Counter or a
>> >>>>> Gauge should be irrelevant. So far we're using the metric
>> >> type
>> >>>>> that is
>> >>>>> the most convenient at exposing a given value. If there is
>> >>>>> some backing
>> >>>>> data-structure that we want to expose some data from we
>> >>>>> typically opt
>> >>>>> for a Gauge, as otherwise we're just mucking around with the
>> >>>>> Meter/Counter API to get it to match. Similarly, if we want
>> >> to
>> >>>>> count
>> >>>>> something but no current count exists we typically added a
>> >>>>> Counter.
>> >>>>> That's why attaching semantics to metric types makes little
>> >>>>> sense (but
>> >>>>> unfortunately several reporters already do it); for
>> >>>>> counters/meters
>> >>>>> certainly, but the majority of metrics are gauges.
>> >>>>>
>> >>>>> 2) I'm talking about time-series databases like Prometheus.
>> >> We
>> >>>>> would
>> >>>>> only have a gauge metric exposing the last fetchTime/emitTime
>> >>>>> that is
>> >>>>> regularly reported to the backend (Prometheus), where a user
>> >>>>> could build
>> >>>>> a histogram of his choosing when/if he wants it.
>> >>>>>
>> >>>>> On 22.02.2019 13:57, Becket Qin wrote:
>> >>>>>> Hi Chesnay,
>> >>>>>>
>> >>>>>> Thanks for the explanation.
>> >>>>>>
>> >>>>>> ** Re: FLIP
>> >>>>>> I might have misunderstood this, but it seems that "major
>> >>>>> changes" are well
>> >>>>>> defined in FLIP. The full contents is following:
>> >>>>>> What is considered a "major change" that needs a FLIP?
>> >>>>>>
>> >>>>>> Any of the following should be considered a major change:
>> >>>>>>
>> >>>>>> - Any major new feature, subsystem, or piece of
>> >>>>> functionality
>> >>>>>> - *Any change that impacts the public interfaces of the
>> >>>>> project*
>> >>>>>>
>> >>>>>> What are the "public interfaces" of the project?
>> >>>>>>
>> >>>>>>
>> >>>>>>
>> >>>>>> *All of the following are public interfaces *that people
>> >>>>> build around:
>> >>>>>>
>> >>>>>> - DataStream and DataSet API, including classes related
>> >>>>> to that, such as
>> >>>>>> StreamExecutionEnvironment
>> >>>>>>
>> >>>>>>
>> >>>>>> - Classes marked with the @Public annotation
>> >>>>>>
>> >>>>>>
>> >>>>>> - On-disk binary formats, such as
>> >> checkpoints/savepoints
>> >>>>>>
>> >>>>>>
>> >>>>>> - User-facing scripts/command-line tools, i.e.
>> >>>>> bin/flink, Yarn scripts,
>> >>>>>> Mesos scripts
>> >>>>>>
>> >>>>>>
>> >>>>>> - Configuration settings
>> >>>>>>
>> >>>>>>
>> >>>>>> - *Exposed monitoring information*
>> >>>>>>
>> >>>>>>
>> >>>>>> So any monitoring information change is considered as
>> >> public
>> >>>>> interface, and
>> >>>>>> any public interface change is considered as a "major
>> >>> change".
>> >>>>>>
>> >>>>>>
>> >>>>>> ** Re: over complication of implementation.
>> >>>>>>
>> >>>>>> Although this is more of implementation details that is not
>> >>>>> covered by the
>> >>>>>> FLIP. But it may be worth discussing.
>> >>>>>>
>> >>>>>> First of all, I completely agree that we should use the
>> >>>>> simplest way to
>> >>>>>> achieve our goal. To me the goal is the following:
>> >>>>>> 1. Clear connector conventions and interfaces.
>> >>>>>> 2. The easiness of creating a connector.
>> >>>>>>
>> >>>>>> Both of them are important to the prosperity of the
>> >>>>> connector ecosystem. So
>> >>>>>> I'd rather abstract as much as possible on our side to make
>> >>>>> the connector
>> >>>>>> developer's work lighter. Given this goal, a static util
>> >>>>> method approach
>> >>>>>> might have a few drawbacks:
>> >>>>>> 1. Users still have to construct the metrics by themselves.
>> >>>>> (And note that
>> >>>>>> this might be erroneous by itself. For example, a customer
>> >>>>> wrapper around
>> >>>>>> dropwizard meter maybe used instead of MeterView).
>> >>>>>> 2. When connector specific metrics are added, it is
>> >>>>> difficult to enforce
>> >>>>>> the scope to be the same as standard metrics.
>> >>>>>> 3. It seems that a method proliferation is inevitable if we
>> >>>>> want to apply
>> >>>>>> sanity checks. e.g. The metric of numBytesIn was not
>> >>>>> registered for a meter.
>> >>>>>> 4. Metrics are still defined in random places and hard to
>> >>>> track.
>> >>>>>>
>> >>>>>> The current PR I had was inspired by the Config system in
>> >>>>> Kafka, which I
>> >>>>>> found pretty handy. In fact it is not only used by Kafka
>> >>>>> itself but even
>> >>>>>> some other projects that depend on Kafka. I am not saying
>> >>>>> this approach is
>> >>>>>> perfect. But I think it worths to save the work for
>> >>>>> connector writers and
>> >>>>>> encourage more systematic implementation. That being said,
>> >> I
>> >>>>> am fully open
>> >>>>>> to suggestions.
>> >>>>>>
>> >>>>>>
>> >>>>>> Re: Histogram
>> >>>>>> I think there are two orthogonal questions around those
>> >>>> metrics:
>> >>>>>>
>> >>>>>> 1. Regardless of the metric type, by just looking at the
>> >>>>> meaning of a
>> >>>>>> metric, is generic to all connectors? If the answer is yes,
>> >>>>> we should
>> >>>>>> include the metric into the convention. No matter whether
>> >> we
>> >>>>> include it
>> >>>>>> into the convention or not, some connector implementations
>> >>>>> will emit such
>> >>>>>> metric. It is better to have a convention than letting each
>> >>>>> connector do
>> >>>>>> random things.
>> >>>>>>
>> >>>>>> 2. If a standard metric is a histogram, what should we do?
>> >>>>>> I agree that we should make it clear that using histograms
>> >>>>> will have
>> >>>>>> performance risk. But I do see histogram is useful in some
>> >>>>> fine-granularity
>> >>>>>> debugging where one do not have the luxury to stop the
>> >>>>> system and inject
>> >>>>>> more inspection code. So the workaround I am thinking is to
>> >>>>> provide some
>> >>>>>> implementation suggestions. Assume later on we have a
>> >>>>> mechanism of
>> >>>>>> selective metrics. In the abstract metrics class we can
>> >>>>> disable those
>> >>>>>> metrics by default individual connector writers does not
>> >>>>> have to do
>> >>>>>> anything (this is another advantage of having an
>> >>>>> AbstractMetrics instead of
>> >>>>>> static util methods.)
>> >>>>>>
>> >>>>>> I am not sure I fully understand the histogram in the
>> >>>>> backend approach. Can
>> >>>>>> you explain a bit more? Do you mean emitting the raw data,
>> >>>>> e.g. fetchTime
>> >>>>>> and emitTime with each record and let the histogram
>> >>>>> computation happen in
>> >>>>>> the background? Or let the processing thread putting the
>> >>>>> values into a
>> >>>>>> queue and have a separate thread polling from the queue and
>> >>>>> add them into
>> >>>>>> the histogram?
>> >>>>>>
>> >>>>>> Thanks,
>> >>>>>>
>> >>>>>> Jiangjie (Becket) Qin
>> >>>>>>
>> >>>>>>
>> >>>>>>
>> >>>>>>
>> >>>>>>
>> >>>>>> On Fri, Feb 22, 2019 at 4:34 PM Chesnay Schepler
>> >>>>> <chesnay@apache.org <ma...@apache.org>> wrote:
>> >>>>>>
>> >>>>>>> Re: Flip
>> >>>>>>> The very first line under both the main header and Purpose
>> >>>>> section
>> >>>>>>> describe Flips as "major changes", which this isn't.
>> >>>>>>>
>> >>>>>>> Re: complication
>> >>>>>>> I'm not arguing against standardization, but again an
>> >>>>> over-complicated
>> >>>>>>> implementation when a static utility method would be
>> >>>>> sufficient.
>> >>>>>>>
>> >>>>>>> public static void setupConnectorMetrics(
>> >>>>>>> MetricGroup operatorMetricGroup,
>> >>>>>>> String connectorName,
>> >>>>>>> Optional<Gauge<Long>> numRecordsIn,
>> >>>>>>> ...)
>> >>>>>>>
>> >>>>>>> This gives you all you need:
>> >>>>>>> * a well-defined set of metrics for a connector to opt-in
>> >>>>>>> * standardized naming schemes for scope and individual
>> >>> metrics
>> >>>>>>> * standardize metric types (although personally I'm not
>> >>>>> interested in that
>> >>>>>>> since metric types should be considered syntactic sugar)
>> >>>>>>>
>> >>>>>>> Re: Configurable Histogram
>> >>>>>>> If anything they _must_ be turned off by default, but the
>> >>>>> metric system is
>> >>>>>>> already exposing so many options that I'm not too keen on
>> >>>>> adding even more.
>> >>>>>>> You have also only addressed my first argument against
>> >>>>> histograms
>> >>>>>>> (performance), the second one still stands (calculate
>> >>>>> histogram in metric
>> >>>>>>> backends instead).
>> >>>>>>>
>> >>>>>>> On 21.02.2019 16:27, Becket Qin wrote:
>> >>>>>>>> Hi Chesnay,
>> >>>>>>>>
>> >>>>>>>> Thanks for the comments. I think this is worthy of a FLIP
>> >>>>> because it is
>> >>>>>>>> public API. According to the FLIP description a FlIP is
>> >>>>> required in case
>> >>>>>>> of:
>> >>>>>>>> - Any change that impacts the public interfaces of
>> >>>>> the project
>> >>>>>>>>
>> >>>>>>>> and the following entry is found in the definition of
>> >>>>> "public interface".
>> >>>>>>>>
>> >>>>>>>> - Exposed monitoring information
>> >>>>>>>>
>> >>>>>>>> Metrics are critical to any production system. So a clear
>> >>>>> metric
>> >>>>>>> definition
>> >>>>>>>> is important for any serious users. For an organization
>> >>>>> with large Flink
>> >>>>>>>> installation, change in metrics means great amount of
>> >>>>> work. So such
>> >>>>>>> changes
>> >>>>>>>> do need to be fully discussed and documented.
>> >>>>>>>>
>> >>>>>>>> ** Re: Histogram.
>> >>>>>>>> We can discuss whether there is a better way to expose
>> >>>>> metrics that are
>> >>>>>>>> suitable for histograms. My micro-benchmark on various
>> >>>>> histogram
>> >>>>>>>> implementations also indicates that they are
>> >> significantly
>> >>>>> slower than
>> >>>>>>>> other metric types. But I don't think that means never
>> >> use
>> >>>>> histogram, but
>> >>>>>>>> means use it with caution. For example, we can suggest
>> >> the
>> >>>>>>> implementations
>> >>>>>>>> to turn them off by default and only turn it on for a
>> >>>>> small amount of
>> >>>>>>> time
>> >>>>>>>> when performing some micro-debugging.
>> >>>>>>>>
>> >>>>>>>> ** Re: complication:
>> >>>>>>>> Connector conventions are essential for Flink ecosystem.
>> >>>>> Flink connectors
>> >>>>>>>> pool is probably the most important part of Flink, just
>> >>>>> like any other
>> >>>>>>> data
>> >>>>>>>> system. Clear conventions of connectors will help build
>> >>>>> Flink ecosystem
>> >>>>>>> in
>> >>>>>>>> a more organic way.
>> >>>>>>>> Take the metrics convention as an example, imagine
>> >> someone
>> >>>>> has developed
>> >>>>>>> a
>> >>>>>>>> Flink connector for System foo, and another developer may
>> >>>>> have developed
>> >>>>>>> a
>> >>>>>>>> monitoring and diagnostic framework for Flink which
>> >>>>> analyzes the Flink
>> >>>>>>> job
>> >>>>>>>> performance based on metrics. With a clear metric
>> >>>>> convention, those two
>> >>>>>>>> projects could be developed independently. Once users put
>> >>>>> them together,
>> >>>>>>>> it would work without additional modifications. This
>> >>>>> cannot be easily
>> >>>>>>>> achieved by just defining a few constants.
>> >>>>>>>>
>> >>>>>>>> ** Re: selective metrics:
>> >>>>>>>> Sure, we can discuss that in a separate thread.
>> >>>>>>>>
>> >>>>>>>> @Dawid
>> >>>>>>>>
>> >>>>>>>> ** Re: latency / fetchedLatency
>> >>>>>>>> The primary purpose of establish such a convention is to
>> >>>>> help developers
>> >>>>>>>> write connectors in a more compatible way. The convention
>> >>>>> is supposed to
>> >>>>>>> be
>> >>>>>>>> defined more proactively. So when look at the convention,
>> >>>>> it seems more
>> >>>>>>>> important to see if the concept is applicable to
>> >>>>> connectors in general.
>> >>>>>>> It
>> >>>>>>>> might be true so far only Kafka connector reports
>> >> latency.
>> >>>>> But there
>> >>>>>>> might
>> >>>>>>>> be hundreds of other connector implementations in the
>> >>>>> Flink ecosystem,
>> >>>>>>>> though not in the Flink repo, and some of them also emits
>> >>>>> latency. I
>> >>>>>>> think
>> >>>>>>>> a lot of other sources actually also has an append
>> >>>>> timestamp. e.g.
>> >>>>>>> database
>> >>>>>>>> bin logs and some K-V stores. So I wouldn't be surprised
>> >>>>> if some database
>> >>>>>>>> connector can also emit latency metrics.
>> >>>>>>>>
>> >>>>>>>> Thanks,
>> >>>>>>>>
>> >>>>>>>> Jiangjie (Becket) Qin
>> >>>>>>>>
>> >>>>>>>>
>> >>>>>>>> On Thu, Feb 21, 2019 at 10:14 PM Chesnay Schepler
>> >>>>> <chesnay@apache.org <ma...@apache.org>>
>> >>>>>>>> wrote:
>> >>>>>>>>
>> >>>>>>>>> Regarding 2) It doesn't make sense to investigate this
>> >> as
>> >>>>> part of this
>> >>>>>>>>> FLIP. This is something that could be of interest for
>> >> the
>> >>>>> entire metric
>> >>>>>>>>> system, and should be designed for as such.
>> >>>>>>>>>
>> >>>>>>>>> Regarding the proposal as a whole:
>> >>>>>>>>>
>> >>>>>>>>> Histogram metrics shall not be added to the core of
>> >>>>> Flink. They are
>> >>>>>>>>> significantly more expensive than other metrics, and
>> >>>>> calculating
>> >>>>>>>>> histograms in the application is regarded as an
>> >>>>> anti-pattern by several
>> >>>>>>>>> metric backends, who instead recommend to expose the raw
>> >>>>> data and
>> >>>>>>>>> calculate the histogram in the backend.
>> >>>>>>>>>
>> >>>>>>>>> Second, this seems overly complicated. Given that we
>> >>>>> already established
>> >>>>>>>>> that not all connectors will export all metrics we are
>> >>>>> effectively
>> >>>>>>>>> reducing this down to a consistent naming scheme. We
>> >>>>> don't need anything
>> >>>>>>>>> sophisticated for that; basically just a few constants
>> >>>>> that all
>> >>>>>>>>> connectors use.
>> >>>>>>>>>
>> >>>>>>>>> I'm not convinced that this is worthy of a FLIP.
>> >>>>>>>>>
>> >>>>>>>>> On 21.02.2019 14:26, Dawid Wysakowicz wrote:
>> >>>>>>>>>> Hi,
>> >>>>>>>>>>
>> >>>>>>>>>> Ad 1. In general I undestand and I agree. But those
>> >>>>> particular metrics
>> >>>>>>>>>> (latency, fetchLatency), right now would only be
>> >>>>> reported if user uses
>> >>>>>>>>>> KafkaConsumer with internal timestampAssigner with
>> >>>>> StreamCharacteristic
>> >>>>>>>>>> set to EventTime, right? That sounds like a very
>> >>>>> specific case. I am
>> >>>>>>> not
>> >>>>>>>>>> sure if we should introduce a generic metric that will
>> >> be
>> >>>>>>>>>> disabled/absent for most of implementations.
>> >>>>>>>>>>
>> >>>>>>>>>> Ad.2 That sounds like an orthogonal issue, that might
>> >>>>> make sense to
>> >>>>>>>>>> investigate in the future.
>> >>>>>>>>>>
>> >>>>>>>>>> Best,
>> >>>>>>>>>>
>> >>>>>>>>>> Dawid
>> >>>>>>>>>>
>> >>>>>>>>>> On 21/02/2019 13:20, Becket Qin wrote:
>> >>>>>>>>>>> Hi Dawid,
>> >>>>>>>>>>>
>> >>>>>>>>>>> Thanks for the feedback. That makes sense to me. There
>> >>>>> are two cases
>> >>>>>>> to
>> >>>>>>>>> be
>> >>>>>>>>>>> addressed.
>> >>>>>>>>>>>
>> >>>>>>>>>>> 1. The metrics are supposed to be a guidance. It is
>> >>>>> likely that a
>> >>>>>>>>> connector
>> >>>>>>>>>>> only supports some but not all of the metrics. In that
>> >>>>> case, each
>> >>>>>>>>> connector
>> >>>>>>>>>>> implementation should have the freedom to decide which
>> >>>>> metrics are
>> >>>>>>>>>>> reported. For the metrics that are supported, the
>> >>>>> guidance should be
>> >>>>>>>>>>> followed.
>> >>>>>>>>>>>
>> >>>>>>>>>>> 2. Sometimes users may want to disable certain metrics
>> >>>>> for some reason
>> >>>>>>>>>>> (e.g. performance / reprocessing of data). A generic
>> >>>>> mechanism should
>> >>>>>>> be
>> >>>>>>>>>>> provided to allow user choose which metrics are
>> >>>>> reported. This
>> >>>>>>> mechanism
>> >>>>>>>>>>> should also be honored by the connector
>> >> implementations.
>> >>>>>>>>>>>
>> >>>>>>>>>>> Does this sound reasonable to you?
>> >>>>>>>>>>>
>> >>>>>>>>>>> Thanks,
>> >>>>>>>>>>>
>> >>>>>>>>>>> Jiangjie (Becket) Qin
>> >>>>>>>>>>>
>> >>>>>>>>>>>
>> >>>>>>>>>>>
>> >>>>>>>>>>> On Thu, Feb 21, 2019 at 4:22 PM Dawid Wysakowicz <
>> >>>>>>>>> dwysakowicz@apache.org <ma...@apache.org>>
>> >>>>>>>>>>> wrote:
>> >>>>>>>>>>>
>> >>>>>>>>>>>> Hi,
>> >>>>>>>>>>>>
>> >>>>>>>>>>>> Generally I like the idea of having a unified,
>> >>>>> standard set of
>> >>>>>>> metrics
>> >>>>>>>>> for
>> >>>>>>>>>>>> all connectors. I have some slight concerns about
>> >>>>> fetchLatency and
>> >>>>>>>>>>>> latency though. They are computed based on EventTime
>> >>>>> which is not a
>> >>>>>>>>> purely
>> >>>>>>>>>>>> technical feature. It depends often on some business
>> >>>>> logic, might be
>> >>>>>>>>> absent
>> >>>>>>>>>>>> or defined after source. Those metrics could also
>> >>>>> behave in a weird
>> >>>>>>>>> way in
>> >>>>>>>>>>>> case of replaying backlog. Therefore I am not sure if
>> >>>>> we should
>> >>>>>>> include
>> >>>>>>>>>>>> those metrics by default. Maybe we could at least
>> >>>>> introduce a feature
>> >>>>>>>>>>>> switch for them? What do you think?
>> >>>>>>>>>>>>
>> >>>>>>>>>>>> Best,
>> >>>>>>>>>>>>
>> >>>>>>>>>>>> Dawid
>> >>>>>>>>>>>> On 21/02/2019 03:13, Becket Qin wrote:
>> >>>>>>>>>>>>
>> >>>>>>>>>>>> Bump. If there is no objections to the proposed
>> >>>>> metrics. I'll start a
>> >>>>>>>>>>>> voting thread later toady.
>> >>>>>>>>>>>>
>> >>>>>>>>>>>> Thanks,
>> >>>>>>>>>>>>
>> >>>>>>>>>>>> Jiangjie (Becket) Qin
>> >>>>>>>>>>>>
>> >>>>>>>>>>>> On Mon, Feb 11, 2019 at 8:17 PM Becket Qin
>> >>>>> <becket.qin@gmail.com <ma...@gmail.com>> <
>> >>>>>>>>> becket.qin@gmail.com <ma...@gmail.com>>
>> >>> wrote:
>> >>>>>>>>>>>> Hi folks,
>> >>>>>>>>>>>>
>> >>>>>>>>>>>> I would like to start the FLIP discussion thread
>> >> about
>> >>>>> standardize
>> >>>>>>> the
>> >>>>>>>>>>>> connector metrics.
>> >>>>>>>>>>>>
>> >>>>>>>>>>>> In short, we would like to provide a convention of
>> >>>>> Flink connector
>> >>>>>>>>>>>> metrics. It will help simplify the monitoring and
>> >>>>> alerting on Flink
>> >>>>>>>>> jobs.
>> >>>>>>>>>>>> The FLIP link is following:
>> >>>>>>>>>>>>
>> >>>>>>>>>>>>
>> >>>>>>>
>> >>>>>
>> >>>>
>> >>>
>> >>
>> https://cwiki.apache.org/confluence/display/FLINK/FLIP-33%3A+Standardize+Connector+Metrics
>> >>>>>>>>>>>> Thanks,
>> >>>>>>>>>>>>
>> >>>>>>>>>>>> Jiangjie (Becket) Qin
>> >>>>>>>>>>>>
>> >>>>>>>>>>>>
>> >>>>>>>>>>>>
>> >>>>>>>
>> >>>>>
>> >>>>
>> >>>>
>> >>>
>> >>
>>
>>
Re: [DISCUSS] FLIP-33: Standardize connector metrics
Posted by Becket Qin <be...@gmail.com>.
Hi Piotr,
Thanks a lot for the feedback.
1a) I guess you are referring to the part that "original system specific
metrics should also be reported". The performance impact depends on the
implementation. An efficient implementation would only record the metric
once, but report them with two different metric names. This is unlikely to
hurt performance.
1b) Yes, I agree that we should avoid adding overhead to the critical path
by all means. This is sometimes a tradeoff, running blindly without any
metric gives best performance, but sometimes might be frustrating when we
debug some issues.
2. The metrics are indeed very useful. Are they supposed to be reported by
the connectors or Flink itself? At this point FLIP-33 is more focused on
provide a guidance to the connector authors on the metrics reporting. That
said, after FLIP-27, I think we should absolutely report these metrics in
the abstract implementation. In any case, the metric convention in this
list are expected to evolve over time.
Thanks,
Jiangjie (Becket) Qin
On Tue, May 28, 2019 at 6:24 PM Piotr Nowojski <pi...@ververica.com> wrote:
> Hi,
>
> Thanks for the proposal and driving the effort here Becket :) I’ve read
> through the FLIP-33 [1], and here are couple of my thoughts.
>
> Big +1 for standardising the metric names between connectors, it will
> definitely help us and users a lot.
>
> Issues/questions/things to discuss that I’ve thought of:
>
> 1a. If we are about to duplicate some metrics, can this become a
> performance issue?
> 1b. Generally speaking, we should make sure that collecting those metrics
> is as non intrusive as possible, especially that they will need to be
> updated once per record. (They might be collected more rarely with some
> overhead, but the hot path of updating it per record will need to be as
> quick as possible). That includes both avoiding heavy computation on per
> record path: histograms?, measuring time for time based metrics (per
> second) (System.currentTimeMillis() depending on the implementation can
> invoke a system call)
>
> 2. It would be nice to have metrics, that allow us to check the cause of
> back pressure:
> a) for sources, length of input queue (in bytes? Or boolean
> hasSomethingl/isEmpty)
> b) for sinks, length of output queue (in bytes? Or boolean
> hasSomething/isEmpty)
>
> a) is useful in a scenario when we are processing backlog of records, all
> of the internal Flink’s input/output network buffers are empty, and we want
> to check whether the external source system is the bottleneck (source’s
> input queue will be empty), or if the Flink’s connector is the bottleneck
> (source’s input queues will be full).
> b) similar story. Backlog of records, but this time all of the internal
> Flink’s input/ouput network buffers are full, and we want o check whether
> the external sink system is the bottleneck (sink output queues are full),
> or if the Flink’s connector is the bottleneck (sink’s output queues will be
> empty)
>
> It might be sometimes difficult to provide those metrics, so they could be
> optional, but if we could provide them, it would be really helpful.
>
> Piotrek
>
> [1]
> https://cwiki.apache.org/confluence/display/FLINK/FLIP-33:+Standardize+Connector+Metrics
> <
> https://cwiki.apache.org/confluence/display/FLINK/FLIP-33:+Standardize+Connector+Metrics
> >
>
> > On 24 Apr 2019, at 13:28, Stephan Ewen <se...@apache.org> wrote:
> >
> > I think this sounds reasonable.
> >
> > Let's keep the "reconfiguration without stopping the job" out of this,
> > because that would be a super big effort and if we approach that, then in
> > more generic way rather than specific to connector metrics.
> >
> > I would suggest to look at the following things before starting with any
> > implementation work:
> >
> > - Try and find a committer to support this, otherwise it will be hard to
> > make progress
> > - Start with defining a smaller set of "core metrics" and extend the set
> > later. I think that is easier than now blocking on reaching consensus on
> a
> > large group of metrics.
> > - Find a solution to the problem Chesnay mentioned, that the "records
> in"
> > metric is somehow overloaded and exists already in the IO Metric group.
> >
> >
> > On Mon, Mar 25, 2019 at 7:16 AM Becket Qin <be...@gmail.com> wrote:
> >
> >> Hi Stephan,
> >>
> >> Thanks a lot for the feedback. All makes sense.
> >>
> >> It is a good suggestion to simply have an onRecord(numBytes, eventTime)
> >> method for connector writers. It should meet most of the requirements,
> >> individual
> >>
> >> The configurable metrics feature is something really useful, especially
> if
> >> we can somehow make it dynamically configurable without stopping the
> jobs.
> >> It might be better to make it a separate discussion because it is a more
> >> generic feature instead of only for connectors.
> >>
> >> So in order to make some progress, in this FLIP we can limit the
> discussion
> >> scope to the connector related items:
> >>
> >> - the standard connector metric names and types.
> >> - the abstract ConnectorMetricHandler interface
> >>
> >> I'll start a separate thread to discuss other general metric related
> >> enhancement items including:
> >>
> >> - optional metrics
> >> - dynamic metric configuration
> >> - potential combination with rate limiter
> >>
> >> Does this plan sound reasonable?
> >>
> >> Thanks,
> >>
> >> Jiangjie (Becket) Qin
> >>
> >> On Sat, Mar 23, 2019 at 5:53 AM Stephan Ewen <se...@apache.org> wrote:
> >>
> >>> Ignoring for a moment implementation details, this connector metrics
> work
> >>> is a really good thing to do, in my opinion
> >>>
> >>> The questions "oh, my job seems to be doing nothing, I am looking at
> the
> >> UI
> >>> and the 'records in' value is still zero" is in the top three support
> >>> questions I have been asked personally.
> >>> Introspection into "how far is the consumer lagging behind" (event time
> >>> fetch latency) came up many times as well.
> >>>
> >>> So big +1 to solving this problem.
> >>>
> >>> About the exact design - I would try to go for the following
> properties:
> >>>
> >>> - keep complexity of of connectors. Ideally the metrics handler has a
> >>> single onRecord(numBytes, eventTime) method or so, and everything else
> is
> >>> internal to the handler. That makes it dead simple for the connector.
> We
> >>> can also think of an extensive scheme for connector specific metrics.
> >>>
> >>> - make it configurable on the job it cluster level which metrics the
> >>> handler internally creates when that method is invoked.
> >>>
> >>> What do you think?
> >>>
> >>> Best,
> >>> Stephan
> >>>
> >>>
> >>> On Thu, Mar 21, 2019 at 10:42 AM Chesnay Schepler <ch...@apache.org>
> >>> wrote:
> >>>
> >>>> As I said before, I believe this to be over-engineered and have no
> >>>> interest in this implementation.
> >>>>
> >>>> There are conceptual issues like defining a duplicate
> >> numBytesIn(PerSec)
> >>>> metric that already exists for each operator.
> >>>>
> >>>> On 21.03.2019 06:13, Becket Qin wrote:
> >>>>> A few updates to the thread. I uploaded a patch[1] as a complete
> >>>>> example of how users can use the metrics in the future.
> >>>>>
> >>>>> Some thoughts below after taking a look at the AbstractMetricGroup
> >> and
> >>>>> its subclasses.
> >>>>>
> >>>>> This patch intends to provide convenience for Flink connector
> >>>>> implementations to follow metrics standards proposed in FLIP-33. It
> >>>>> also try to enhance the metric management in general way to help
> >> users
> >>>>> with:
> >>>>>
> >>>>> 1. metric definition
> >>>>> 2. metric dependencies check
> >>>>> 3. metric validation
> >>>>> 4. metric control (turn on / off particular metrics)
> >>>>>
> >>>>> This patch wraps |MetricGroup| to extend the functionality of
> >>>>> |AbstractMetricGroup| and its subclasses. The
> >>>>> |AbstractMetricGroup| mainly focus on the metric group hierarchy, but
> >>>>> does not really manage the metrics other than keeping them in a Map.
> >>>>>
> >>>>> Ideally we should only have one entry point for the metrics.
> >>>>>
> >>>>> Right now the entry point is |AbstractMetricGroup|. However, besides
> >>>>> the missing functionality mentioned above, |AbstractMetricGroup|
> >> seems
> >>>>> deeply rooted in Flink runtime. We could extract it out to
> >>>>> flink-metrics in order to use it for generic purpose. There will be
> >>>>> some work, though.
> >>>>>
> >>>>> Another approach is to make |AbstractMetrics| in this patch as the
> >>>>> metric entry point. It wraps metric group and provides the missing
> >>>>> functionalities. Then we can roll out this pattern to runtime
> >>>>> components gradually as well.
> >>>>>
> >>>>> My first thought is that the latter approach gives a more smooth
> >>>>> migration. But I am also OK with doing a refactoring on the
> >>>>> |AbstractMetricGroup| family.
> >>>>>
> >>>>>
> >>>>> Thanks,
> >>>>>
> >>>>> Jiangjie (Becket) Qin
> >>>>>
> >>>>> [1] https://github.com/becketqin/flink/pull/1
> >>>>>
> >>>>> On Mon, Feb 25, 2019 at 2:32 PM Becket Qin <becket.qin@gmail.com
> >>>>> <ma...@gmail.com>> wrote:
> >>>>>
> >>>>> Hi Chesnay,
> >>>>>
> >>>>> It might be easier to discuss some implementation details in the
> >>>>> PR review instead of in the FLIP discussion thread. I have a
> >> patch
> >>>>> for Kafka connectors ready but haven't submitted the PR yet.
> >>>>> Hopefully that will help explain a bit more.
> >>>>>
> >>>>> ** Re: metric type binding
> >>>>> This is a valid point that worths discussing. If I understand
> >>>>> correctly, there are two points:
> >>>>>
> >>>>> 1. Metric type / interface does not matter as long as the metric
> >>>>> semantic is clearly defined.
> >>>>> Conceptually speaking, I agree that as long as the metric
> >> semantic
> >>>>> is defined, metric type does not matter. To some extent, Gauge /
> >>>>> Counter / Meter / Histogram themselves can be think of as some
> >>>>> well-recognized semantics, if you wish. In Flink, these metric
> >>>>> semantics have their associated interface classes. In practice,
> >>>>> such semantic to interface binding seems necessary for different
> >>>>> components to communicate. Simply standardize the semantic of
> >> the
> >>>>> connector metrics seems not sufficient for people to build
> >>>>> ecosystem on top of. At the end of the day, we still need to have
> >>>>> some embodiment of the metric semantics that people can program
> >>>>> against.
> >>>>>
> >>>>> 2. Sometimes the same metric semantic can be exposed using
> >>>>> different metric types / interfaces.
> >>>>> This is a good point. Counter and Gauge-as-a-Counter are pretty
> >>>>> much interchangeable. This is more of a trade-off between the
> >> user
> >>>>> experience of metric producers and consumers. The metric
> >> producers
> >>>>> want to use Counter or Gauge depending on whether the counter is
> >>>>> already tracked in code, while ideally the metric consumers only
> >>>>> want to see a single metric type for each metric. I am leaning
> >>>>> towards to make the metric producers happy, i.e. allow Gauge /
> >>>>> Counter metric type, and the the metric consumers handle the type
> >>>>> variation. The reason is that in practice, there might be more
> >>>>> connector implementations than metric reporter implementations.
> >> We
> >>>>> could also provide some helper method to facilitate reading from
> >>>>> such variable metric type.
> >>>>>
> >>>>>
> >>>>> Just some quick replies to the comments around implementation
> >>>> details.
> >>>>>
> >>>>> 4) single place where metrics are registered except
> >>>>> connector-specific
> >>>>> ones (which we can't really avoid).
> >>>>>
> >>>>> Register connector specific ones in a single place is actually
> >>>>> something that I want to achieve.
> >>>>>
> >>>>> 2) I'm talking about time-series databases like Prometheus.
> >> We
> >>>>> would
> >>>>> only have a gauge metric exposing the last fetchTime/emitTime
> >>>>> that is
> >>>>> regularly reported to the backend (Prometheus), where a user
> >>>>> could build
> >>>>> a histogram of his choosing when/if he wants it.
> >>>>>
> >>>>> Not sure if such downsampling works. As an example, if a user
> >>>>> complains that there are some intermittent latency spikes (maybe
> >> a
> >>>>> few records in 10 seconds) in their processing system. Having a
> >>>>> Gauge sampling instantaneous latency seems unlikely useful.
> >>>>> However by looking at actual 99.9 percentile latency might help.
> >>>>>
> >>>>> Thanks,
> >>>>>
> >>>>> Jiangjie (Becket) Qin
> >>>>>
> >>>>>
> >>>>> On Fri, Feb 22, 2019 at 9:30 PM Chesnay Schepler
> >>>>> <chesnay@apache.org <ma...@apache.org>> wrote:
> >>>>>
> >>>>> Re: over complication of implementation.
> >>>>>
> >>>>> I think I get understand better know what you're shooting
> >> for,
> >>>>> effectively something like the OperatorIOMetricGroup.
> >>>>> But still, re-define setupConnectorMetrics() to accept a set
> >>>>> of flags
> >>>>> for counters/meters(ans _possibly_ histograms) along with a
> >>>>> set of
> >>>>> well-defined Optional<Gauge<?>>, and return the group.
> >>>>>
> >>>>> Solves all issues as far as i can tell:
> >>>>> 1) no metrics must be created manually (except Gauges, which
> >>> are
> >>>>> effectively just Suppliers and you can't get around this),
> >>>>> 2) additional metrics can be registered on the returned
> >> group,
> >>>>> 3) see 1),
> >>>>> 4) single place where metrics are registered except
> >>>>> connector-specific
> >>>>> ones (which we can't really avoid).
> >>>>>
> >>>>> Re: Histogram
> >>>>>
> >>>>> 1) As an example, whether "numRecordsIn" is exposed as a
> >>>>> Counter or a
> >>>>> Gauge should be irrelevant. So far we're using the metric
> >> type
> >>>>> that is
> >>>>> the most convenient at exposing a given value. If there is
> >>>>> some backing
> >>>>> data-structure that we want to expose some data from we
> >>>>> typically opt
> >>>>> for a Gauge, as otherwise we're just mucking around with the
> >>>>> Meter/Counter API to get it to match. Similarly, if we want
> >> to
> >>>>> count
> >>>>> something but no current count exists we typically added a
> >>>>> Counter.
> >>>>> That's why attaching semantics to metric types makes little
> >>>>> sense (but
> >>>>> unfortunately several reporters already do it); for
> >>>>> counters/meters
> >>>>> certainly, but the majority of metrics are gauges.
> >>>>>
> >>>>> 2) I'm talking about time-series databases like Prometheus.
> >> We
> >>>>> would
> >>>>> only have a gauge metric exposing the last fetchTime/emitTime
> >>>>> that is
> >>>>> regularly reported to the backend (Prometheus), where a user
> >>>>> could build
> >>>>> a histogram of his choosing when/if he wants it.
> >>>>>
> >>>>> On 22.02.2019 13:57, Becket Qin wrote:
> >>>>>> Hi Chesnay,
> >>>>>>
> >>>>>> Thanks for the explanation.
> >>>>>>
> >>>>>> ** Re: FLIP
> >>>>>> I might have misunderstood this, but it seems that "major
> >>>>> changes" are well
> >>>>>> defined in FLIP. The full contents is following:
> >>>>>> What is considered a "major change" that needs a FLIP?
> >>>>>>
> >>>>>> Any of the following should be considered a major change:
> >>>>>>
> >>>>>> - Any major new feature, subsystem, or piece of
> >>>>> functionality
> >>>>>> - *Any change that impacts the public interfaces of the
> >>>>> project*
> >>>>>>
> >>>>>> What are the "public interfaces" of the project?
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>>> *All of the following are public interfaces *that people
> >>>>> build around:
> >>>>>>
> >>>>>> - DataStream and DataSet API, including classes related
> >>>>> to that, such as
> >>>>>> StreamExecutionEnvironment
> >>>>>>
> >>>>>>
> >>>>>> - Classes marked with the @Public annotation
> >>>>>>
> >>>>>>
> >>>>>> - On-disk binary formats, such as
> >> checkpoints/savepoints
> >>>>>>
> >>>>>>
> >>>>>> - User-facing scripts/command-line tools, i.e.
> >>>>> bin/flink, Yarn scripts,
> >>>>>> Mesos scripts
> >>>>>>
> >>>>>>
> >>>>>> - Configuration settings
> >>>>>>
> >>>>>>
> >>>>>> - *Exposed monitoring information*
> >>>>>>
> >>>>>>
> >>>>>> So any monitoring information change is considered as
> >> public
> >>>>> interface, and
> >>>>>> any public interface change is considered as a "major
> >>> change".
> >>>>>>
> >>>>>>
> >>>>>> ** Re: over complication of implementation.
> >>>>>>
> >>>>>> Although this is more of implementation details that is not
> >>>>> covered by the
> >>>>>> FLIP. But it may be worth discussing.
> >>>>>>
> >>>>>> First of all, I completely agree that we should use the
> >>>>> simplest way to
> >>>>>> achieve our goal. To me the goal is the following:
> >>>>>> 1. Clear connector conventions and interfaces.
> >>>>>> 2. The easiness of creating a connector.
> >>>>>>
> >>>>>> Both of them are important to the prosperity of the
> >>>>> connector ecosystem. So
> >>>>>> I'd rather abstract as much as possible on our side to make
> >>>>> the connector
> >>>>>> developer's work lighter. Given this goal, a static util
> >>>>> method approach
> >>>>>> might have a few drawbacks:
> >>>>>> 1. Users still have to construct the metrics by themselves.
> >>>>> (And note that
> >>>>>> this might be erroneous by itself. For example, a customer
> >>>>> wrapper around
> >>>>>> dropwizard meter maybe used instead of MeterView).
> >>>>>> 2. When connector specific metrics are added, it is
> >>>>> difficult to enforce
> >>>>>> the scope to be the same as standard metrics.
> >>>>>> 3. It seems that a method proliferation is inevitable if we
> >>>>> want to apply
> >>>>>> sanity checks. e.g. The metric of numBytesIn was not
> >>>>> registered for a meter.
> >>>>>> 4. Metrics are still defined in random places and hard to
> >>>> track.
> >>>>>>
> >>>>>> The current PR I had was inspired by the Config system in
> >>>>> Kafka, which I
> >>>>>> found pretty handy. In fact it is not only used by Kafka
> >>>>> itself but even
> >>>>>> some other projects that depend on Kafka. I am not saying
> >>>>> this approach is
> >>>>>> perfect. But I think it worths to save the work for
> >>>>> connector writers and
> >>>>>> encourage more systematic implementation. That being said,
> >> I
> >>>>> am fully open
> >>>>>> to suggestions.
> >>>>>>
> >>>>>>
> >>>>>> Re: Histogram
> >>>>>> I think there are two orthogonal questions around those
> >>>> metrics:
> >>>>>>
> >>>>>> 1. Regardless of the metric type, by just looking at the
> >>>>> meaning of a
> >>>>>> metric, is generic to all connectors? If the answer is yes,
> >>>>> we should
> >>>>>> include the metric into the convention. No matter whether
> >> we
> >>>>> include it
> >>>>>> into the convention or not, some connector implementations
> >>>>> will emit such
> >>>>>> metric. It is better to have a convention than letting each
> >>>>> connector do
> >>>>>> random things.
> >>>>>>
> >>>>>> 2. If a standard metric is a histogram, what should we do?
> >>>>>> I agree that we should make it clear that using histograms
> >>>>> will have
> >>>>>> performance risk. But I do see histogram is useful in some
> >>>>> fine-granularity
> >>>>>> debugging where one do not have the luxury to stop the
> >>>>> system and inject
> >>>>>> more inspection code. So the workaround I am thinking is to
> >>>>> provide some
> >>>>>> implementation suggestions. Assume later on we have a
> >>>>> mechanism of
> >>>>>> selective metrics. In the abstract metrics class we can
> >>>>> disable those
> >>>>>> metrics by default individual connector writers does not
> >>>>> have to do
> >>>>>> anything (this is another advantage of having an
> >>>>> AbstractMetrics instead of
> >>>>>> static util methods.)
> >>>>>>
> >>>>>> I am not sure I fully understand the histogram in the
> >>>>> backend approach. Can
> >>>>>> you explain a bit more? Do you mean emitting the raw data,
> >>>>> e.g. fetchTime
> >>>>>> and emitTime with each record and let the histogram
> >>>>> computation happen in
> >>>>>> the background? Or let the processing thread putting the
> >>>>> values into a
> >>>>>> queue and have a separate thread polling from the queue and
> >>>>> add them into
> >>>>>> the histogram?
> >>>>>>
> >>>>>> Thanks,
> >>>>>>
> >>>>>> Jiangjie (Becket) Qin
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>>> On Fri, Feb 22, 2019 at 4:34 PM Chesnay Schepler
> >>>>> <chesnay@apache.org <ma...@apache.org>> wrote:
> >>>>>>
> >>>>>>> Re: Flip
> >>>>>>> The very first line under both the main header and Purpose
> >>>>> section
> >>>>>>> describe Flips as "major changes", which this isn't.
> >>>>>>>
> >>>>>>> Re: complication
> >>>>>>> I'm not arguing against standardization, but again an
> >>>>> over-complicated
> >>>>>>> implementation when a static utility method would be
> >>>>> sufficient.
> >>>>>>>
> >>>>>>> public static void setupConnectorMetrics(
> >>>>>>> MetricGroup operatorMetricGroup,
> >>>>>>> String connectorName,
> >>>>>>> Optional<Gauge<Long>> numRecordsIn,
> >>>>>>> ...)
> >>>>>>>
> >>>>>>> This gives you all you need:
> >>>>>>> * a well-defined set of metrics for a connector to opt-in
> >>>>>>> * standardized naming schemes for scope and individual
> >>> metrics
> >>>>>>> * standardize metric types (although personally I'm not
> >>>>> interested in that
> >>>>>>> since metric types should be considered syntactic sugar)
> >>>>>>>
> >>>>>>> Re: Configurable Histogram
> >>>>>>> If anything they _must_ be turned off by default, but the
> >>>>> metric system is
> >>>>>>> already exposing so many options that I'm not too keen on
> >>>>> adding even more.
> >>>>>>> You have also only addressed my first argument against
> >>>>> histograms
> >>>>>>> (performance), the second one still stands (calculate
> >>>>> histogram in metric
> >>>>>>> backends instead).
> >>>>>>>
> >>>>>>> On 21.02.2019 16:27, Becket Qin wrote:
> >>>>>>>> Hi Chesnay,
> >>>>>>>>
> >>>>>>>> Thanks for the comments. I think this is worthy of a FLIP
> >>>>> because it is
> >>>>>>>> public API. According to the FLIP description a FlIP is
> >>>>> required in case
> >>>>>>> of:
> >>>>>>>> - Any change that impacts the public interfaces of
> >>>>> the project
> >>>>>>>>
> >>>>>>>> and the following entry is found in the definition of
> >>>>> "public interface".
> >>>>>>>>
> >>>>>>>> - Exposed monitoring information
> >>>>>>>>
> >>>>>>>> Metrics are critical to any production system. So a clear
> >>>>> metric
> >>>>>>> definition
> >>>>>>>> is important for any serious users. For an organization
> >>>>> with large Flink
> >>>>>>>> installation, change in metrics means great amount of
> >>>>> work. So such
> >>>>>>> changes
> >>>>>>>> do need to be fully discussed and documented.
> >>>>>>>>
> >>>>>>>> ** Re: Histogram.
> >>>>>>>> We can discuss whether there is a better way to expose
> >>>>> metrics that are
> >>>>>>>> suitable for histograms. My micro-benchmark on various
> >>>>> histogram
> >>>>>>>> implementations also indicates that they are
> >> significantly
> >>>>> slower than
> >>>>>>>> other metric types. But I don't think that means never
> >> use
> >>>>> histogram, but
> >>>>>>>> means use it with caution. For example, we can suggest
> >> the
> >>>>>>> implementations
> >>>>>>>> to turn them off by default and only turn it on for a
> >>>>> small amount of
> >>>>>>> time
> >>>>>>>> when performing some micro-debugging.
> >>>>>>>>
> >>>>>>>> ** Re: complication:
> >>>>>>>> Connector conventions are essential for Flink ecosystem.
> >>>>> Flink connectors
> >>>>>>>> pool is probably the most important part of Flink, just
> >>>>> like any other
> >>>>>>> data
> >>>>>>>> system. Clear conventions of connectors will help build
> >>>>> Flink ecosystem
> >>>>>>> in
> >>>>>>>> a more organic way.
> >>>>>>>> Take the metrics convention as an example, imagine
> >> someone
> >>>>> has developed
> >>>>>>> a
> >>>>>>>> Flink connector for System foo, and another developer may
> >>>>> have developed
> >>>>>>> a
> >>>>>>>> monitoring and diagnostic framework for Flink which
> >>>>> analyzes the Flink
> >>>>>>> job
> >>>>>>>> performance based on metrics. With a clear metric
> >>>>> convention, those two
> >>>>>>>> projects could be developed independently. Once users put
> >>>>> them together,
> >>>>>>>> it would work without additional modifications. This
> >>>>> cannot be easily
> >>>>>>>> achieved by just defining a few constants.
> >>>>>>>>
> >>>>>>>> ** Re: selective metrics:
> >>>>>>>> Sure, we can discuss that in a separate thread.
> >>>>>>>>
> >>>>>>>> @Dawid
> >>>>>>>>
> >>>>>>>> ** Re: latency / fetchedLatency
> >>>>>>>> The primary purpose of establish such a convention is to
> >>>>> help developers
> >>>>>>>> write connectors in a more compatible way. The convention
> >>>>> is supposed to
> >>>>>>> be
> >>>>>>>> defined more proactively. So when look at the convention,
> >>>>> it seems more
> >>>>>>>> important to see if the concept is applicable to
> >>>>> connectors in general.
> >>>>>>> It
> >>>>>>>> might be true so far only Kafka connector reports
> >> latency.
> >>>>> But there
> >>>>>>> might
> >>>>>>>> be hundreds of other connector implementations in the
> >>>>> Flink ecosystem,
> >>>>>>>> though not in the Flink repo, and some of them also emits
> >>>>> latency. I
> >>>>>>> think
> >>>>>>>> a lot of other sources actually also has an append
> >>>>> timestamp. e.g.
> >>>>>>> database
> >>>>>>>> bin logs and some K-V stores. So I wouldn't be surprised
> >>>>> if some database
> >>>>>>>> connector can also emit latency metrics.
> >>>>>>>>
> >>>>>>>> Thanks,
> >>>>>>>>
> >>>>>>>> Jiangjie (Becket) Qin
> >>>>>>>>
> >>>>>>>>
> >>>>>>>> On Thu, Feb 21, 2019 at 10:14 PM Chesnay Schepler
> >>>>> <chesnay@apache.org <ma...@apache.org>>
> >>>>>>>> wrote:
> >>>>>>>>
> >>>>>>>>> Regarding 2) It doesn't make sense to investigate this
> >> as
> >>>>> part of this
> >>>>>>>>> FLIP. This is something that could be of interest for
> >> the
> >>>>> entire metric
> >>>>>>>>> system, and should be designed for as such.
> >>>>>>>>>
> >>>>>>>>> Regarding the proposal as a whole:
> >>>>>>>>>
> >>>>>>>>> Histogram metrics shall not be added to the core of
> >>>>> Flink. They are
> >>>>>>>>> significantly more expensive than other metrics, and
> >>>>> calculating
> >>>>>>>>> histograms in the application is regarded as an
> >>>>> anti-pattern by several
> >>>>>>>>> metric backends, who instead recommend to expose the raw
> >>>>> data and
> >>>>>>>>> calculate the histogram in the backend.
> >>>>>>>>>
> >>>>>>>>> Second, this seems overly complicated. Given that we
> >>>>> already established
> >>>>>>>>> that not all connectors will export all metrics we are
> >>>>> effectively
> >>>>>>>>> reducing this down to a consistent naming scheme. We
> >>>>> don't need anything
> >>>>>>>>> sophisticated for that; basically just a few constants
> >>>>> that all
> >>>>>>>>> connectors use.
> >>>>>>>>>
> >>>>>>>>> I'm not convinced that this is worthy of a FLIP.
> >>>>>>>>>
> >>>>>>>>> On 21.02.2019 14:26, Dawid Wysakowicz wrote:
> >>>>>>>>>> Hi,
> >>>>>>>>>>
> >>>>>>>>>> Ad 1. In general I undestand and I agree. But those
> >>>>> particular metrics
> >>>>>>>>>> (latency, fetchLatency), right now would only be
> >>>>> reported if user uses
> >>>>>>>>>> KafkaConsumer with internal timestampAssigner with
> >>>>> StreamCharacteristic
> >>>>>>>>>> set to EventTime, right? That sounds like a very
> >>>>> specific case. I am
> >>>>>>> not
> >>>>>>>>>> sure if we should introduce a generic metric that will
> >> be
> >>>>>>>>>> disabled/absent for most of implementations.
> >>>>>>>>>>
> >>>>>>>>>> Ad.2 That sounds like an orthogonal issue, that might
> >>>>> make sense to
> >>>>>>>>>> investigate in the future.
> >>>>>>>>>>
> >>>>>>>>>> Best,
> >>>>>>>>>>
> >>>>>>>>>> Dawid
> >>>>>>>>>>
> >>>>>>>>>> On 21/02/2019 13:20, Becket Qin wrote:
> >>>>>>>>>>> Hi Dawid,
> >>>>>>>>>>>
> >>>>>>>>>>> Thanks for the feedback. That makes sense to me. There
> >>>>> are two cases
> >>>>>>> to
> >>>>>>>>> be
> >>>>>>>>>>> addressed.
> >>>>>>>>>>>
> >>>>>>>>>>> 1. The metrics are supposed to be a guidance. It is
> >>>>> likely that a
> >>>>>>>>> connector
> >>>>>>>>>>> only supports some but not all of the metrics. In that
> >>>>> case, each
> >>>>>>>>> connector
> >>>>>>>>>>> implementation should have the freedom to decide which
> >>>>> metrics are
> >>>>>>>>>>> reported. For the metrics that are supported, the
> >>>>> guidance should be
> >>>>>>>>>>> followed.
> >>>>>>>>>>>
> >>>>>>>>>>> 2. Sometimes users may want to disable certain metrics
> >>>>> for some reason
> >>>>>>>>>>> (e.g. performance / reprocessing of data). A generic
> >>>>> mechanism should
> >>>>>>> be
> >>>>>>>>>>> provided to allow user choose which metrics are
> >>>>> reported. This
> >>>>>>> mechanism
> >>>>>>>>>>> should also be honored by the connector
> >> implementations.
> >>>>>>>>>>>
> >>>>>>>>>>> Does this sound reasonable to you?
> >>>>>>>>>>>
> >>>>>>>>>>> Thanks,
> >>>>>>>>>>>
> >>>>>>>>>>> Jiangjie (Becket) Qin
> >>>>>>>>>>>
> >>>>>>>>>>>
> >>>>>>>>>>>
> >>>>>>>>>>> On Thu, Feb 21, 2019 at 4:22 PM Dawid Wysakowicz <
> >>>>>>>>> dwysakowicz@apache.org <ma...@apache.org>>
> >>>>>>>>>>> wrote:
> >>>>>>>>>>>
> >>>>>>>>>>>> Hi,
> >>>>>>>>>>>>
> >>>>>>>>>>>> Generally I like the idea of having a unified,
> >>>>> standard set of
> >>>>>>> metrics
> >>>>>>>>> for
> >>>>>>>>>>>> all connectors. I have some slight concerns about
> >>>>> fetchLatency and
> >>>>>>>>>>>> latency though. They are computed based on EventTime
> >>>>> which is not a
> >>>>>>>>> purely
> >>>>>>>>>>>> technical feature. It depends often on some business
> >>>>> logic, might be
> >>>>>>>>> absent
> >>>>>>>>>>>> or defined after source. Those metrics could also
> >>>>> behave in a weird
> >>>>>>>>> way in
> >>>>>>>>>>>> case of replaying backlog. Therefore I am not sure if
> >>>>> we should
> >>>>>>> include
> >>>>>>>>>>>> those metrics by default. Maybe we could at least
> >>>>> introduce a feature
> >>>>>>>>>>>> switch for them? What do you think?
> >>>>>>>>>>>>
> >>>>>>>>>>>> Best,
> >>>>>>>>>>>>
> >>>>>>>>>>>> Dawid
> >>>>>>>>>>>> On 21/02/2019 03:13, Becket Qin wrote:
> >>>>>>>>>>>>
> >>>>>>>>>>>> Bump. If there is no objections to the proposed
> >>>>> metrics. I'll start a
> >>>>>>>>>>>> voting thread later toady.
> >>>>>>>>>>>>
> >>>>>>>>>>>> Thanks,
> >>>>>>>>>>>>
> >>>>>>>>>>>> Jiangjie (Becket) Qin
> >>>>>>>>>>>>
> >>>>>>>>>>>> On Mon, Feb 11, 2019 at 8:17 PM Becket Qin
> >>>>> <becket.qin@gmail.com <ma...@gmail.com>> <
> >>>>>>>>> becket.qin@gmail.com <ma...@gmail.com>>
> >>> wrote:
> >>>>>>>>>>>> Hi folks,
> >>>>>>>>>>>>
> >>>>>>>>>>>> I would like to start the FLIP discussion thread
> >> about
> >>>>> standardize
> >>>>>>> the
> >>>>>>>>>>>> connector metrics.
> >>>>>>>>>>>>
> >>>>>>>>>>>> In short, we would like to provide a convention of
> >>>>> Flink connector
> >>>>>>>>>>>> metrics. It will help simplify the monitoring and
> >>>>> alerting on Flink
> >>>>>>>>> jobs.
> >>>>>>>>>>>> The FLIP link is following:
> >>>>>>>>>>>>
> >>>>>>>>>>>>
> >>>>>>>
> >>>>>
> >>>>
> >>>
> >>
> https://cwiki.apache.org/confluence/display/FLINK/FLIP-33%3A+Standardize+Connector+Metrics
> >>>>>>>>>>>> Thanks,
> >>>>>>>>>>>>
> >>>>>>>>>>>> Jiangjie (Becket) Qin
> >>>>>>>>>>>>
> >>>>>>>>>>>>
> >>>>>>>>>>>>
> >>>>>>>
> >>>>>
> >>>>
> >>>>
> >>>
> >>
>
>