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Posted to dev@kafka.apache.org by Kowshik Prakasam <kp...@confluent.io> on 2020/10/06 22:46:09 UTC
Re: [VOTE] KIP-584: Versioning scheme for features
Hi Jun,
I have added the following details in the KIP-584 write up:
1. Deployment, IBP deprecation and avoidance of double rolls. This section
talks about the various phases of work that would be required to use this
KIP to eventually avoid Broker double rolls in the cluster (whenever IBP
values are advanced). Link to section:
https://cwiki.apache.org/confluence/display/KAFKA/KIP-584%3A+Versioning+scheme+for+features#KIP584:Versioningschemeforfeatures-Deployment,IBPdeprecationandavoidanceofdoublerolls
.
2. Feature version deprecation. This section explains the idea for feature
version deprecation (using highest supported feature min version) which you
had proposed during code review:
https://cwiki.apache.org/confluence/display/KAFKA/KIP-584%3A+Versioning+scheme+for+features#KIP584:Versioningschemeforfeatures-Featureversiondeprecation
.
Please let me know if you have any questions.
Cheers,
Kowshik
On Tue, Sep 29, 2020 at 11:07 AM Jun Rao <ju...@confluent.io> wrote:
> Hi, Kowshik,
>
> Thanks for the update. Regarding enabling a single rolling restart in the
> future, could we sketch out a bit how this will work by treating IBP as a
> feature? For example, IBP currently uses the release version and this KIP
> uses an integer for versions. How do we bridge the gap between the two?
> Does min.version still make sense for IBP as a feature?
>
> Thanks,
>
> Jun
>
> On Fri, Sep 25, 2020 at 5:57 PM Kowshik Prakasam <kp...@confluent.io>
> wrote:
>
> > Hi Colin,
> >
> > Thanks for the feedback. Those are very good points. I have made the
> > following changes to the KIP as you had suggested:
> > 1. Included the `timeoutMs` field in the `UpdateFeaturesRequest` schema.
> > The initial implementation won't be making use of the field, but we can
> > always use it in the future as the need arises.
> > 2. Modified the `FinalizedFeaturesEpoch` field in `ApiVersionsResponse`
> to
> > use int64. This is to avoid overflow problems in the future once ZK is
> > gone.
> >
> > I have also incorporated these changes into the versioning write path PR
> > that is currently under review:
> https://github.com/apache/kafka/pull/9001.
> >
> >
> > Cheers,
> > Kowshik
> >
> >
> >
> > On Fri, Sep 25, 2020 at 4:57 PM Kowshik Prakasam <kprakasam@confluent.io
> >
> > wrote:
> >
> > > Hi Jun,
> > >
> > > Thanks for the feedback. It's a very good point. I have now modified
> the
> > > KIP-584 write-up "goals" section a bit. It now mentions one of the
> goals
> > as
> > > enabling rolling upgrades using a single restart (instead of 2). Also I
> > > have removed the text explicitly aiming for deprecation of IBP. Note
> that
> > > previously under "Potential features in Kafka" the IBP was mentioned
> > under
> > > point (4) as a possible coarse-grained feature. Hopefully, now the 2
> > > sections of the KIP align with each other well.
> > >
> > >
> > > Cheers,
> > > Kowshik
> > >
> > >
> > > On Fri, Sep 25, 2020 at 2:03 PM Colin McCabe <cm...@apache.org>
> wrote:
> > >
> > >> On Tue, Sep 22, 2020, at 00:43, Kowshik Prakasam wrote:
> > >> > Hi all,
> > >> >
> > >> > I wanted to let you know that I have made the following changes to
> the
> > >> > KIP-584 write up. The purpose is to ensure the design is correct
> for a
> > >> few
> > >> > things which came up during implementation:
> > >> >
> > >>
> > >> Hi Kowshik,
> > >>
> > >> Thanks for the updates.
> > >>
> > >> >
> > >> > 1. Per FeatureUpdate error code: The UPDATE_FEATURES controller API
> is
> > >> no
> > >> > longer transactional. Going forward, we allow for individual
> > >> FeatureUpdate
> > >> > to succeed/fail in the request. As a result, the response schema now
> > >> > contains an error code per FeatureUpdate as well as a top-level
> error
> > >> code.
> > >> > Overall this is a better design because it better represents the
> > nature
> > >> of
> > >> > the API: each FeatureUpdate in the request is independent of the
> other
> > >> > updates, and the controller can process/apply these independently to
> > ZK.
> > >> > When an UPDATE_FEATURES request fails, this new design provides
> better
> > >> > clarity to the caller on which FeatureUpdate could not be applied
> (via
> > >> the
> > >> > individual error codes). In the previous design, we were unable to
> > >> achieve
> > >> > such an increased level of clarity in communicating the error codes.
> > >> >
> > >>
> > >> OK
> > >>
> > >> >
> > >> > 2. Due to #1, there were some minor changes required to the proposed
> > >> Admin
> > >> > APIs (describeFeatures and updateFeatures). A few unnecessary public
> > >> APIs
> > >> > have been removed, and couple essential ones have been added. The
> > latest
> > >> > changes now represent the latest design.
> > >> >
> > >> > 3. The timeoutMs field has been removed from the the UPDATE_FEATURES
> > API
> > >> > request, since it was not found to be required during
> implementation.
> > >> >
> > >>
> > >> Please don't get rid of timeoutMs. timeoutMs is required if you want
> to
> > >> implement the ability to timeout the call if the controller can't get
> > to it
> > >> in time. This is important for avoiding congestion collapse where the
> > >> controller collapses under the weight of lots of retries of the same
> > set of
> > >> calls.
> > >>
> > >> We may not be able to do it in the initial implementation, but we will
> > >> eventually implement this for all the controller-bound RPCs.
> > >>
> > >> > >
> > >> > > 2. Finalized feature version epoch data type has been made to be
> > int32
> > >> > > (instead of int64). The reason is that the epoch value is the
> value
> > >> of ZK
> > >> > > node version, whose data type is int32.
> > >> > >
> > >>
> > >> Sorry, I missed this earlier. Using 16 bit feature levels seems fine.
> > >> However, please don't use a 32-bit epoch here. We deliberately made
> the
> > >> epoch 64 bits to avoid overflow problems in the future once ZK is
> gone.
> > >>
> > >> best,
> > >> Colin
> > >>
> > >> > > 3. Introduced a new 'status' field in the '/features' ZK node
> > schema.
> > >> The
> > >> > > purpose is to implement Colin's earlier point for the strategy for
> > >> > > transitioning from not having a /features znode to having one. An
> > >> > > explanation has been provided in the following section of the KIP
> > >> detailing
> > >> > > the different cases:
> > >> > >
> > >>
> >
> https://cwiki.apache.org/confluence/display/KAFKA/KIP-584%3A+Versioning+scheme+for+features#KIP584:Versioningschemeforfeatures-FeatureZKnodestatus
> > >> > > .
> > >> > >
> > >> > > Please let me know if you have any questions or concerns.
> > >> > >
> > >> > >
> > >> > > Cheers,
> > >> > > Kowshik
> > >> > >
> > >> > >
> > >> > >
> > >> > > Cheers,
> > >> > > Kowshik
> > >> > >
> > >> > > On Tue, Apr 28, 2020 at 11:24 PM Kowshik Prakasam <
> > >> kprakasam@confluent.io>
> > >> > > wrote:
> > >> > >
> > >> > >> Hi all,
> > >> > >>
> > >> > >> This KIP vote has been open for ~12 days. The summary of the
> votes
> > is
> > >> > >> that we have 3 binding votes (Colin, Guozhang, Jun), and 3
> > >> non-binding
> > >> > >> votes (David, Dhruvil, Boyang). Therefore, the KIP vote passes.
> > I'll
> > >> mark
> > >> > >> KIP as accepted and start working on the implementation.
> > >> > >>
> > >> > >> Thanks a lot!
> > >> > >>
> > >> > >>
> > >> > >> Cheers,
> > >> > >> Kowshik
> > >> > >>
> > >> > >> On Mon, Apr 27, 2020 at 12:15 PM Colin McCabe <
> cmccabe@apache.org>
> > >> wrote:
> > >> > >>
> > >> > >>> Thanks, Kowshik. +1 (binding)
> > >> > >>>
> > >> > >>> best,
> > >> > >>> Colin
> > >> > >>>
> > >> > >>> On Sat, Apr 25, 2020, at 13:20, Kowshik Prakasam wrote:
> > >> > >>> > Hi Colin,
> > >> > >>> >
> > >> > >>> > Thanks for the explanation! I agree with you, and I have
> updated
> > >> the
> > >> > >>> > KIP.
> > >> > >>> > Here is a link to relevant section:
> > >> > >>> >
> > >> > >>>
> > >>
> >
> https://cwiki.apache.org/confluence/display/KAFKA/KIP-584%3A+Versioning+scheme+for+features#KIP-584:Versioningschemeforfeatures-Controller:ZKnodebootstrapwithdefaultvalues
> > >> > >>> >
> > >> > >>> >
> > >> > >>> > Cheers,
> > >> > >>> > Kowshik
> > >> > >>> >
> > >> > >>> > On Fri, Apr 24, 2020 at 8:50 PM Colin McCabe <
> > cmccabe@apache.org>
> > >> > >>> wrote:
> > >> > >>> >
> > >> > >>> > > On Fri, Apr 24, 2020, at 00:01, Kowshik Prakasam wrote:
> > >> > >>> > > > (Kowshik): Great point! However for case #1, I'm not sure
> > why
> > >> we
> > >> > >>> need to
> > >> > >>> > > > create a '/features' ZK node with disabled features.
> > Instead,
> > >> do
> > >> > >>> you see
> > >> > >>> > > > any drawback if we just do not create it? i.e. if IBP is
> > less
> > >> than
> > >> > >>> 2.6,
> > >> > >>> > > the
> > >> > >>> > > > controller treats the case as though the versioning system
> > is
> > >> > >>> completely
> > >> > >>> > > > disabled, and would not create a non-existing '/features'
> > >> node.
> > >> > >>> > >
> > >> > >>> > > Hi Kowshik,
> > >> > >>> > >
> > >> > >>> > > When the IBP is less than 2.6, but the software has been
> > >> upgraded to
> > >> > >>> a
> > >> > >>> > > state where it supports this KIP, that
> > >> > >>> > > means the user is upgrading from an earlier version of the
> > >> > >>> software. In
> > >> > >>> > > this case, we want to start with all the features disabled
> and
> > >> allow
> > >> > >>> the
> > >> > >>> > > user to enable them when they are ready.
> > >> > >>> > >
> > >> > >>> > > Enabling all the possible features immediately after an
> > upgrade
> > >> > >>> could be
> > >> > >>> > > harmful to the cluster. On the other hand, for a new
> cluster,
> > >> we do
> > >> > >>> want
> > >> > >>> > > to enable all the possible features immediately . I was
> > >> proposing
> > >> > >>> this as a
> > >> > >>> > > way to distinguish the two cases (since the new cluster will
> > >> never be
> > >> > >>> > > started with an old IBP).
> > >> > >>> > >
> > >> > >>> > > > Colin MccCabe wrote:
> > >> > >>> > > > > And now, something a little bit bigger (sorry). For
> > >> finalized
> > >> > >>> > > features,
> > >> > >>> > > > > why do we need both min_version_level and
> > max_version_level?
> > >> > >>> Assuming
> > >> > >>> > > that
> > >> > >>> > > > > we want all the brokers to be on the same feature
> version
> > >> level,
> > >> > >>> we
> > >> > >>> > > really only care
> > >> > >>> > > > > about three numbers for each feature, right? The
> minimum
> > >> > >>> supported
> > >> > >>> > > version
> > >> > >>> > > > > level, the maximum supported version level, and the
> > current
> > >> > >>> active
> > >> > >>> > > version level.
> > >> > >>> > > >
> > >> > >>> > > > > We don't actually want different brokers to be on
> > different
> > >> > >>> versions of
> > >> > >>> > > > > the same feature, right? So we can just have one number
> > for
> > >> > >>> current
> > >> > >>> > > > > version level, rather than two. At least that's what I
> > was
> > >> > >>> thinking
> > >> > >>> > > -- let
> > >> > >>> > > > > me know if I missed something.
> > >> > >>> > > >
> > >> > >>> > > > (Kowshik): It is my understanding that the "current active
> > >> version
> > >> > >>> level"
> > >> > >>> > > > that you have mentioned, is the "max_version_level". But
> we
> > >> still
> > >> > >>> > > > maintain/publish both min and max version levels, because,
> > the
> > >> > >>> detail
> > >> > >>> > > about
> > >> > >>> > > > min level is useful to external clients. This is described
> > >> below.
> > >> > >>> > > >
> > >> > >>> > > > For any feature F, think of the closed range:
> > >> [min_version_level,
> > >> > >>> > > > max_version_level] as the range of finalized versions,
> > that's
> > >> > >>> guaranteed
> > >> > >>> > > to
> > >> > >>> > > > be supported by all brokers in the cluster.
> > >> > >>> > > > - "max_version_level" is the finalized highest common
> > version
> > >> > >>> among all
> > >> > >>> > > > brokers,
> > >> > >>> > > > - "min_version_level" is the finalized lowest common
> > version
> > >> > >>> among all
> > >> > >>> > > > brokers.
> > >> > >>> > > >
> > >> > >>> > > > Next, think of "client" here as the "user of the new
> feature
> > >> > >>> versions
> > >> > >>> > > > system". Imagine that such a client learns about finalized
> > >> feature
> > >> > >>> > > > versions, and exercises some logic based on the version.
> > These
> > >> > >>> clients
> > >> > >>> > > can
> > >> > >>> > > > be of 2 types:
> > >> > >>> > > > 1. Some part of the broker code itself could behave like a
> > >> client
> > >> > >>> trying
> > >> > >>> > > to
> > >> > >>> > > > use some feature that's "internal" to the broker cluster.
> > >> Such a
> > >> > >>> client
> > >> > >>> > > > would learn the latest finalized features via ZK.
> > >> > >>> > > > 2. An external system (ex: Streams) could behave like a
> > >> client,
> > >> > >>> trying to
> > >> > >>> > > > use some "external" facing feature. Such a client would
> > learn
> > >> > >>> latest
> > >> > >>> > > > finalized features via ApiVersionsRequest. Ex:
> > >> group_coordinator
> > >> > >>> feature
> > >> > >>> > > > described in the KIP.
> > >> > >>> > > >
> > >> > >>> > > > Next, imagine that for F, the max_version_level is
> > >> successfully
> > >> > >>> bumped by
> > >> > >>> > > > +1 (via Controller API). Now it is guaranteed that all
> > brokers
> > >> > >>> (i.e.
> > >> > >>> > > > internal clients) understand max_version_level + 1.
> However,
> > >> it is
> > >> > >>> still
> > >> > >>> > > > not guaranteed that all external clients have support for
> > (or
> > >> have
> > >> > >>> > > > activated) the logic for the newer version. Why? Because,
> > >> this is
> > >> > >>> > > > subjective as explained next:
> > >> > >>> > > >
> > >> > >>> > > > 1. On one hand, imagine F as an internal feature only
> > >> relevant to
> > >> > >>> > > Brokers.
> > >> > >>> > > > The binary for the internal client logic is controlled by
> > >> Broker
> > >> > >>> cluster
> > >> > >>> > > > deployments. When shipping a new Broker release, we
> wouldn't
> > >> bump
> > >> > >>> max
> > >> > >>> > > > "supported" feature version for F by 1, unless we have
> > >> introduced
> > >> > >>> some
> > >> > >>> > > new
> > >> > >>> > > > logic (with a potentially breaking change) in the Broker.
> > >> > >>> Furthermore,
> > >> > >>> > > such
> > >> > >>> > > > feature logic in the broker should/will not be implemented
> > in
> > >> a
> > >> > >>> way that
> > >> > >>> > > it
> > >> > >>> > > > would activate logic for an older feature version after it
> > has
> > >> > >>> migrated
> > >> > >>> > > to
> > >> > >>> > > > using the logic for a newer feature version (because this
> > >> could
> > >> > >>> break the
> > >> > >>> > > > cluster!). For these cases, max_version_level will be very
> > >> useful
> > >> > >>> for
> > >> > >>> > > > decision making.
> > >> > >>> > > >
> > >> > >>> > > > 2. On the other hand, imagine F as an external facing
> > feature.
> > >> > >>> External
> > >> > >>> > > > clients are not within the control of Broker cluster. An
> > >> external
> > >> > >>> client
> > >> > >>> > > > may not have upgraded it's code (yet) to use
> > >> 'max_version_level +
> > >> > >>> 1'.
> > >> > >>> > > But,
> > >> > >>> > > > the Kafka cluster could have been deployed with support
> for
> > >> > >>> > > > 'max_version_level + 1' of an external facing feature.
> Now,
> > >> these
> > >> > >>> > > external
> > >> > >>> > > > clients (until an upgrade) are benefitted in learning
> "what
> > >> is the
> > >> > >>> lowest
> > >> > >>> > > > common version for F among all brokers?". This is where
> the
> > >> > >>> > > > "min_version_level" becomes useful. Using this, a client
> > could
> > >> > >>> learn the
> > >> > >>> > > > specific supported versions that's lower than
> > >> max_version_level
> > >> > >>> (instead
> > >> > >>> > > of
> > >> > >>> > > > assuming that all brokers support the range: [1,
> > >> > >>> max_version_level]). For
> > >> > >>> > > > example, if the cluster deprecates "min_version_level",
> then
> > >> the
> > >> > >>> client
> > >> > >>> > > > becomes aware because it periodically learns the latest
> > >> > >>> > > "min_version_level"
> > >> > >>> > > > via ApiVersionsRequest.
> > >> > >>> > > >
> > >> > >>> > >
> > >> > >>> > > Thanks for the explanation. I agree that this does make
> sense
> > >> when
> > >> > >>> you
> > >> > >>> > > take the client perspective into account.
> > >> > >>> > >
> > >> > >>> > > best,
> > >> > >>> > > Colin
> > >> > >>> > >
> > >> > >>> > >
> > >> > >>> > > >
> > >> > >>> > > > Cheers,
> > >> > >>> > > > Kowshik
> > >> > >>> > > >
> > >> > >>> > > >
> > >> > >>> > > >
> > >> > >>> > > >
> > >> > >>> > > > On Thu, Apr 23, 2020 at 12:07 PM Colin McCabe <
> > >> cmccabe@apache.org>
> > >> > >>> > > wrote:
> > >> > >>> > > >
> > >> > >>> > > > > Hi Kowshik,
> > >> > >>> > > > >
> > >> > >>> > > > > Thanks again for working on this-- it looks great. I
> went
> > >> over
> > >> > >>> the KIP
> > >> > >>> > > > > again and have a few more comments.
> > >> > >>> > > > >
> > >> > >>> > > > > ===
> > >> > >>> > > > >
> > >> > >>> > > > > It would be good to note that deprecating a feature
> > version
> > >> (in
> > >> > >>> other
> > >> > >>> > > > > words, increasing minVersionLevel on the broker) is an
> > >> > >>> incompatible
> > >> > >>> > > change,
> > >> > >>> > > > > which requires a major release of Kafka.
> > >> > >>> > > > >
> > >> > >>> > > > > ===
> > >> > >>> > > > >
> > >> > >>> > > > > I think the strategy for transitioning from not having a
> > >> > >>> /features
> > >> > >>> > > znode
> > >> > >>> > > > > to having one could use some work. The current proposal
> is
> > >> to
> > >> > >>> wait for
> > >> > >>> > > all
> > >> > >>> > > > > the brokers to fill in their feature znodes and then
> pick
> > >> the
> > >> > >>> highest
> > >> > >>> > > > > common versions. But that requires blocking in the
> > >> controller
> > >> > >>> startup
> > >> > >>> > > code
> > >> > >>> > > > > until the whole cluster is active (technically, a point
> in
> > >> time
> > >> > >>> which
> > >> > >>> > > we
> > >> > >>> > > > > never really know that we have reached...)
> > >> > >>> > > > >
> > >> > >>> > > > > Instead, I think it would be better to have a strategy
> > like
> > >> this:
> > >> > >>> > > > > 1. If the controller comes up and there is no /features
> > >> znode
> > >> > >>> AND the
> > >> > >>> > > IBP
> > >> > >>> > > > > is less than 2.6, create a /features znode where all the
> > >> > >>> features are
> > >> > >>> > > > > disabled.
> > >> > >>> > > > > 2. If the controller comes up and there is no /features
> > >> znode
> > >> > >>> AND the
> > >> > >>> > > IBP
> > >> > >>> > > > > is greater than or equal to 2.6, create a /features
> znode
> > >> where
> > >> > >>> all the
> > >> > >>> > > > > features are enabled at the highest versions supported
> by
> > >> the
> > >> > >>> > > controller.
> > >> > >>> > > > >
> > >> > >>> > > > > People upgrading from the pre-KIP-584
> > >> > >>> <https://issues.apache.org/jira/browse/KIP-584>
> > >> > >>> > > > > <https://issues.apache.org/jira/browse/KIP-584> world
> > will
> > >> end
> > >> > >>> up in
> > >> > >>> > > case
> > >> > >>> > > > > #1 because they have to do a double roll to upgrade, and
> > >> during
> > >> > >>> the
> > >> > >>> > > first
> > >> > >>> > > > > roll, the IBP is unchanged. People creating new
> clusters
> > >> from
> > >> > >>> scratch
> > >> > >>> > > will
> > >> > >>> > > > > end up in case #2, which is what we want since we don't
> > >> want a
> > >> > >>> brand
> > >> > >>> > > new
> > >> > >>> > > > > cluster to be using old feature flag versions.
> > >> > >>> > > > >
> > >> > >>> > > > > ===
> > >> > >>> > > > >
> > >> > >>> > > > > UpdateFeaturesResponse#ErrorMessage should specify
> > >> > >>> nullableVersions
> > >> > >>> > > since
> > >> > >>> > > > > null is a valid value here
> > >> > >>> > > > >
> > >> > >>> > > > > Also, in the message format, the tags we use need to
> start
> > >> at 0.
> > >> > >>> > > > >
> > >> > >>> > > > > ===
> > >> > >>> > > > >
> > >> > >>> > > > > I don't think we need the FEATURE_UPDATE_IN_PROGRESS
> error
> > >> > >>> code. The
> > >> > >>> > > > > controller is basically single-threaded and will only do
> > >> one of
> > >> > >>> these
> > >> > >>> > > > > operations at once. Even if it weren't, though, we
> could
> > >> simply
> > >> > >>> block
> > >> > >>> > > the
> > >> > >>> > > > > second operation behind the first one.
> > >> > >>> > > > >
> > >> > >>> > > > > ===
> > >> > >>> > > > >
> > >> > >>> > > > > For updateFeatures, it would be good to specify that if
> a
> > >> single
> > >> > >>> > > feature
> > >> > >>> > > > > version update in the batch can't be done, none of them
> > are
> > >> > >>> done. I
> > >> > >>> > > think
> > >> > >>> > > > > this was the intention, but I wasn't able to find it
> > >> spelled out
> > >> > >>> > > (maybe i
> > >> > >>> > > > > missed it).
> > >> > >>> > > > >
> > >> > >>> > > > > ===
> > >> > >>> > > > >
> > >> > >>> > > > > And now, something a little bit bigger (sorry). For
> > >> finalized
> > >> > >>> > > features,
> > >> > >>> > > > > why do we need both min_version_level and
> > max_version_level?
> > >> > >>> Assuming
> > >> > >>> > > that
> > >> > >>> > > > > we want all the brokers to be on the same feature
> version
> > >> level,
> > >> > >>> we
> > >> > >>> > > really
> > >> > >>> > > > > only care about three numbers for each feature, right?
> > The
> > >> > >>> minimum
> > >> > >>> > > > > supported version level, the maximum supported version
> > >> level,
> > >> > >>> and the
> > >> > >>> > > > > current active version level.
> > >> > >>> > > > >
> > >> > >>> > > > > We don't actually want different brokers to be on
> > different
> > >> > >>> versions of
> > >> > >>> > > > > the same feature, right? So we can just have one number
> > for
> > >> > >>> current
> > >> > >>> > > > > version level, rather than two. At least that's what I
> > was
> > >> > >>> thinking
> > >> > >>> > > -- let
> > >> > >>> > > > > me know if I missed something.
> > >> > >>> > > > >
> > >> > >>> > > > > best,
> > >> > >>> > > > > Colin
> > >> > >>> > > > >
> > >> > >>> > > > >
> > >> > >>> > > > > On Tue, Apr 21, 2020, at 13:01, Dhruvil Shah wrote:
> > >> > >>> > > > > > Thanks for the KIP! +1 (non-binding)
> > >> > >>> > > > > >
> > >> > >>> > > > > > On Tue, Apr 21, 2020 at 6:09 AM David Jacot <
> > >> > >>> djacot@confluent.io>
> > >> > >>> > > wrote:
> > >> > >>> > > > > >
> > >> > >>> > > > > > > Great KIP, thanks! +1 (non-binding)
> > >> > >>> > > > > > >
> > >> > >>> > > > > > > On Fri, Apr 17, 2020 at 8:56 PM Guozhang Wang <
> > >> > >>> wangguoz@gmail.com>
> > >> > >>> > > > > wrote:
> > >> > >>> > > > > > >
> > >> > >>> > > > > > > > Thanks for the great KIP Kowshik, +1 (binding).
> > >> > >>> > > > > > > >
> > >> > >>> > > > > > > > On Fri, Apr 17, 2020 at 11:22 AM Jun Rao <
> > >> jun@confluent.io
> > >> > >>> >
> > >> > >>> > > wrote:
> > >> > >>> > > > > > > >
> > >> > >>> > > > > > > > > Hi, Kowshik,
> > >> > >>> > > > > > > > >
> > >> > >>> > > > > > > > > Thanks for the KIP. +1
> > >> > >>> > > > > > > > >
> > >> > >>> > > > > > > > > Jun
> > >> > >>> > > > > > > > >
> > >> > >>> > > > > > > > > On Thu, Apr 16, 2020 at 11:14 AM Kowshik
> Prakasam
> > <
> > >> > >>> > > > > > > > kprakasam@confluent.io>
> > >> > >>> > > > > > > > > wrote:
> > >> > >>> > > > > > > > >
> > >> > >>> > > > > > > > > > Hi all,
> > >> > >>> > > > > > > > > >
> > >> > >>> > > > > > > > > > I'd like to start a vote for KIP-584
> > >> > >>> <https://issues.apache.org/jira/browse/KIP-584>
> > >> > >>> > > > > <https://issues.apache.org/jira/browse/KIP-584>. The
> link
> > >> to
> > >> > >>> the KIP
> > >> > >>> > > can
> > >> > >>> > > > > be
> > >> > >>> > > > > > > found
> > >> > >>> > > > > > > > > > here:
> > >> > >>> > > > > > > > > >
> > >> > >>> > > > > > > > > >
> > >> > >>> > > > > > > > >
> > >> > >>> > > > > > > >
> > >> > >>> > > > > > >
> > >> > >>> > > > >
> > >> > >>> > >
> > >> > >>>
> > >>
> >
> https://cwiki.apache.org/confluence/display/KAFKA/KIP-584%3A+Versioning+scheme+for+features
> > >> > >>> > > > > > > > > > .
> > >> > >>> > > > > > > > > >
> > >> > >>> > > > > > > > > > Thanks!
> > >> > >>> > > > > > > > > >
> > >> > >>> > > > > > > > > >
> > >> > >>> > > > > > > > > > Cheers,
> > >> > >>> > > > > > > > > > Kowshik
> > >> > >>> > > > > > > > > >
> > >> > >>> > > > > > > > >
> > >> > >>> > > > > > > >
> > >> > >>> > > > > > > >
> > >> > >>> > > > > > > > --
> > >> > >>> > > > > > > > -- Guozhang
> > >> > >>> > > > > > > >
> > >> > >>> > > > > > >
> > >> > >>> > > > > >
> > >> > >>> > > > >
> > >> > >>> > > >
> > >> > >>> > >
> > >> > >>> >
> > >> > >>>
> > >> > >>
> > >> >
> > >>
> > >
> >
>
Re: [VOTE] KIP-584: Versioning scheme for features
Posted by Kowshik Prakasam <kp...@confluent.io>.
Hi all,
I wanted to let you know that I have made the following small change to the
`kafka-features` CLI tool description in the KIP-584 write up. The purpose
is to ensure the design is compatible with post KIP-500 world. I have
eliminated the facility in Admin#describeFeatures API to be able to
optionally send a describeFeatures request to the controller. This facility
was originally seen useful for (1) debugability and (2) slightly better
consistency guarantees in the CLI tool that reads features before updating
them. But in hindsight it now poses a hindrance to post KIP-500 world where
no client would be able to access the controller directly. So, when looking
at cost vs benefit, this facility does not feel useful enough and therefore
I've removed it. We can discuss if it becomes necessary in the future, and
implement a suitable solution.
The corresponding PR containing this change is
https://github.com/apache/kafka/pull/9536 .
Please let me know if you have any questions or concerns.
Cheers,
Kowshik
On Thu, Oct 15, 2020 at 10:17 AM Jun Rao <ju...@confluent.io> wrote:
> Hi, Kowshik,
>
> Thanks for the update. Those changes look good to me.
>
> Jun
>
> On Tue, Oct 13, 2020 at 4:50 PM Kowshik Prakasam <kp...@confluent.io>
> wrote:
>
> > Hi all,
> >
> > I wanted to let you know that I have made the following minor changes to
> > the `kafka-features` CLI tool description in the KIP-584 write up. The
> > purpose is to ensure the design is correct for a few things which came up
> > during implementation:
> >
> > 1. The CLI tool now produces a tab-formatted output instead of JSON. This
> > aligns with the type of format produced by other admin CLI tools of
> Kafka,
> > ex: `kafka-topics`.
> > 2. Whenever feature updates are performed, the output of the CLI tool
> shows
> > the result of each feature update that was applied.
> > 3. The CLI tool accepts an optional argument `--dry-run` which lets the
> > user preview the feature updates before applying them.
> >
> > The following section of the KIP has been updated with the above changes:
> >
> >
> https://cwiki.apache.org/confluence/display/KAFKA/KIP-584%3A+Versioning+scheme+for+features#KIP584:Versioningschemeforfeatures-Toolingsupport
> >
> > Please let me know if you have any questions.
> >
> >
> > Cheers,
> > Kowshik
> >
> >
> > On Thu, Oct 8, 2020 at 1:12 AM Kowshik Prakasam <kp...@confluent.io>
> > wrote:
> >
> > > Hi Jun,
> > >
> > > This is a very good point. I have updated the feature version
> deprecation
> > > section mentioning the same:
> > >
> >
> https://cwiki.apache.org/confluence/display/KAFKA/KIP-584%3A+Versioning+scheme+for+features#KIP584:Versioningschemeforfeatures-Featureversiondeprecation
> > > .
> > >
> > > Thank you for the suggestion.
> > >
> > >
> > > Cheers,
> > > Kowshik
> > >
> > >
> > > On Tue, Oct 6, 2020 at 5:30 PM Jun Rao <ju...@confluent.io> wrote:
> > >
> > >> Hi, Kowshik,
> > >>
> > >> Thanks for the follow up. Both look good to me.
> > >>
> > >> For 2, it would be useful to also add that an admin should make sure
> > that
> > >> no clients are using a deprecated feature version (e.g. using the
> client
> > >> version metric) before deploying a release that deprecates it.
> > >>
> > >> Thanks,
> > >>
> > >> Jun
> > >>
> > >> On Tue, Oct 6, 2020 at 3:46 PM Kowshik Prakasam <
> kprakasam@confluent.io
> > >
> > >> wrote:
> > >>
> > >> > Hi Jun,
> > >> >
> > >> > I have added the following details in the KIP-584 write up:
> > >> >
> > >> > 1. Deployment, IBP deprecation and avoidance of double rolls. This
> > >> section
> > >> > talks about the various phases of work that would be required to use
> > >> this
> > >> > KIP to eventually avoid Broker double rolls in the cluster (whenever
> > IBP
> > >> > values are advanced). Link to section:
> > >> >
> > >> >
> > >>
> >
> https://cwiki.apache.org/confluence/display/KAFKA/KIP-584%3A+Versioning+scheme+for+features#KIP584:Versioningschemeforfeatures-Deployment,IBPdeprecationandavoidanceofdoublerolls
> > >> > .
> > >> >
> > >> > 2. Feature version deprecation. This section explains the idea for
> > >> feature
> > >> > version deprecation (using highest supported feature min version)
> > which
> > >> you
> > >> > had proposed during code review:
> > >> >
> > >> >
> > >>
> >
> https://cwiki.apache.org/confluence/display/KAFKA/KIP-584%3A+Versioning+scheme+for+features#KIP584:Versioningschemeforfeatures-Featureversiondeprecation
> > >> > .
> > >> >
> > >> > Please let me know if you have any questions.
> > >> >
> > >> >
> > >> > Cheers,
> > >> > Kowshik
> > >> >
> > >> >
> > >> > On Tue, Sep 29, 2020 at 11:07 AM Jun Rao <ju...@confluent.io> wrote:
> > >> >
> > >> > > Hi, Kowshik,
> > >> > >
> > >> > > Thanks for the update. Regarding enabling a single rolling restart
> > in
> > >> the
> > >> > > future, could we sketch out a bit how this will work by treating
> IBP
> > >> as a
> > >> > > feature? For example, IBP currently uses the release version and
> > this
> > >> KIP
> > >> > > uses an integer for versions. How do we bridge the gap between the
> > >> two?
> > >> > > Does min.version still make sense for IBP as a feature?
> > >> > >
> > >> > > Thanks,
> > >> > >
> > >> > > Jun
> > >> > >
> > >> > > On Fri, Sep 25, 2020 at 5:57 PM Kowshik Prakasam <
> > >> kprakasam@confluent.io
> > >> > >
> > >> > > wrote:
> > >> > >
> > >> > > > Hi Colin,
> > >> > > >
> > >> > > > Thanks for the feedback. Those are very good points. I have made
> > the
> > >> > > > following changes to the KIP as you had suggested:
> > >> > > > 1. Included the `timeoutMs` field in the `UpdateFeaturesRequest`
> > >> > schema.
> > >> > > > The initial implementation won't be making use of the field, but
> > we
> > >> can
> > >> > > > always use it in the future as the need arises.
> > >> > > > 2. Modified the `FinalizedFeaturesEpoch` field in
> > >> `ApiVersionsResponse`
> > >> > > to
> > >> > > > use int64. This is to avoid overflow problems in the future once
> > ZK
> > >> is
> > >> > > > gone.
> > >> > > >
> > >> > > > I have also incorporated these changes into the versioning write
> > >> path
> > >> > PR
> > >> > > > that is currently under review:
> > >> > > https://github.com/apache/kafka/pull/9001.
> > >> > > >
> > >> > > >
> > >> > > > Cheers,
> > >> > > > Kowshik
> > >> > > >
> > >> > > >
> > >> > > >
> > >> > > > On Fri, Sep 25, 2020 at 4:57 PM Kowshik Prakasam <
> > >> > kprakasam@confluent.io
> > >> > > >
> > >> > > > wrote:
> > >> > > >
> > >> > > > > Hi Jun,
> > >> > > > >
> > >> > > > > Thanks for the feedback. It's a very good point. I have now
> > >> modified
> > >> > > the
> > >> > > > > KIP-584 write-up "goals" section a bit. It now mentions one of
> > the
> > >> > > goals
> > >> > > > as
> > >> > > > > enabling rolling upgrades using a single restart (instead of
> 2).
> > >> > Also I
> > >> > > > > have removed the text explicitly aiming for deprecation of
> IBP.
> > >> Note
> > >> > > that
> > >> > > > > previously under "Potential features in Kafka" the IBP was
> > >> mentioned
> > >> > > > under
> > >> > > > > point (4) as a possible coarse-grained feature. Hopefully, now
> > >> the 2
> > >> > > > > sections of the KIP align with each other well.
> > >> > > > >
> > >> > > > >
> > >> > > > > Cheers,
> > >> > > > > Kowshik
> > >> > > > >
> > >> > > > >
> > >> > > > > On Fri, Sep 25, 2020 at 2:03 PM Colin McCabe <
> > cmccabe@apache.org>
> > >> > > wrote:
> > >> > > > >
> > >> > > > >> On Tue, Sep 22, 2020, at 00:43, Kowshik Prakasam wrote:
> > >> > > > >> > Hi all,
> > >> > > > >> >
> > >> > > > >> > I wanted to let you know that I have made the following
> > >> changes to
> > >> > > the
> > >> > > > >> > KIP-584 write up. The purpose is to ensure the design is
> > >> correct
> > >> > > for a
> > >> > > > >> few
> > >> > > > >> > things which came up during implementation:
> > >> > > > >> >
> > >> > > > >>
> > >> > > > >> Hi Kowshik,
> > >> > > > >>
> > >> > > > >> Thanks for the updates.
> > >> > > > >>
> > >> > > > >> >
> > >> > > > >> > 1. Per FeatureUpdate error code: The UPDATE_FEATURES
> > controller
> > >> > API
> > >> > > is
> > >> > > > >> no
> > >> > > > >> > longer transactional. Going forward, we allow for
> individual
> > >> > > > >> FeatureUpdate
> > >> > > > >> > to succeed/fail in the request. As a result, the response
> > >> schema
> > >> > now
> > >> > > > >> > contains an error code per FeatureUpdate as well as a
> > top-level
> > >> > > error
> > >> > > > >> code.
> > >> > > > >> > Overall this is a better design because it better
> represents
> > >> the
> > >> > > > nature
> > >> > > > >> of
> > >> > > > >> > the API: each FeatureUpdate in the request is independent
> of
> > >> the
> > >> > > other
> > >> > > > >> > updates, and the controller can process/apply these
> > >> independently
> > >> > to
> > >> > > > ZK.
> > >> > > > >> > When an UPDATE_FEATURES request fails, this new design
> > provides
> > >> > > better
> > >> > > > >> > clarity to the caller on which FeatureUpdate could not be
> > >> applied
> > >> > > (via
> > >> > > > >> the
> > >> > > > >> > individual error codes). In the previous design, we were
> > >> unable to
> > >> > > > >> achieve
> > >> > > > >> > such an increased level of clarity in communicating the
> error
> > >> > codes.
> > >> > > > >> >
> > >> > > > >>
> > >> > > > >> OK
> > >> > > > >>
> > >> > > > >> >
> > >> > > > >> > 2. Due to #1, there were some minor changes required to the
> > >> > proposed
> > >> > > > >> Admin
> > >> > > > >> > APIs (describeFeatures and updateFeatures). A few
> unnecessary
> > >> > public
> > >> > > > >> APIs
> > >> > > > >> > have been removed, and couple essential ones have been
> added.
> > >> The
> > >> > > > latest
> > >> > > > >> > changes now represent the latest design.
> > >> > > > >> >
> > >> > > > >> > 3. The timeoutMs field has been removed from the the
> > >> > UPDATE_FEATURES
> > >> > > > API
> > >> > > > >> > request, since it was not found to be required during
> > >> > > implementation.
> > >> > > > >> >
> > >> > > > >>
> > >> > > > >> Please don't get rid of timeoutMs. timeoutMs is required if
> > you
> > >> > want
> > >> > > to
> > >> > > > >> implement the ability to timeout the call if the controller
> > can't
> > >> > get
> > >> > > > to it
> > >> > > > >> in time. This is important for avoiding congestion collapse
> > >> where
> > >> > the
> > >> > > > >> controller collapses under the weight of lots of retries of
> the
> > >> same
> > >> > > > set of
> > >> > > > >> calls.
> > >> > > > >>
> > >> > > > >> We may not be able to do it in the initial implementation,
> but
> > we
> > >> > will
> > >> > > > >> eventually implement this for all the controller-bound RPCs.
> > >> > > > >>
> > >> > > > >> > >
> > >> > > > >> > > 2. Finalized feature version epoch data type has been
> made
> > >> to be
> > >> > > > int32
> > >> > > > >> > > (instead of int64). The reason is that the epoch value is
> > the
> > >> > > value
> > >> > > > >> of ZK
> > >> > > > >> > > node version, whose data type is int32.
> > >> > > > >> > >
> > >> > > > >>
> > >> > > > >> Sorry, I missed this earlier. Using 16 bit feature levels
> > seems
> > >> > fine.
> > >> > > > >> However, please don't use a 32-bit epoch here. We
> deliberately
> > >> made
> > >> > > the
> > >> > > > >> epoch 64 bits to avoid overflow problems in the future once
> ZK
> > is
> > >> > > gone.
> > >> > > > >>
> > >> > > > >> best,
> > >> > > > >> Colin
> > >> > > > >>
> > >> > > > >> > > 3. Introduced a new 'status' field in the '/features' ZK
> > node
> > >> > > > schema.
> > >> > > > >> The
> > >> > > > >> > > purpose is to implement Colin's earlier point for the
> > >> strategy
> > >> > for
> > >> > > > >> > > transitioning from not having a /features znode to having
> > >> one.
> > >> > An
> > >> > > > >> > > explanation has been provided in the following section of
> > the
> > >> > KIP
> > >> > > > >> detailing
> > >> > > > >> > > the different cases:
> > >> > > > >> > >
> > >> > > > >>
> > >> > > >
> > >> > >
> > >> >
> > >>
> >
> https://cwiki.apache.org/confluence/display/KAFKA/KIP-584%3A+Versioning+scheme+for+features#KIP584:Versioningschemeforfeatures-FeatureZKnodestatus
> > >> > > > >> > > .
> > >> > > > >> > >
> > >> > > > >> > > Please let me know if you have any questions or concerns.
> > >> > > > >> > >
> > >> > > > >> > >
> > >> > > > >> > > Cheers,
> > >> > > > >> > > Kowshik
> > >> > > > >> > >
> > >> > > > >> > >
> > >> > > > >> > >
> > >> > > > >> > > Cheers,
> > >> > > > >> > > Kowshik
> > >> > > > >> > >
> > >> > > > >> > > On Tue, Apr 28, 2020 at 11:24 PM Kowshik Prakasam <
> > >> > > > >> kprakasam@confluent.io>
> > >> > > > >> > > wrote:
> > >> > > > >> > >
> > >> > > > >> > >> Hi all,
> > >> > > > >> > >>
> > >> > > > >> > >> This KIP vote has been open for ~12 days. The summary of
> > the
> > >> > > votes
> > >> > > > is
> > >> > > > >> > >> that we have 3 binding votes (Colin, Guozhang, Jun),
> and 3
> > >> > > > >> non-binding
> > >> > > > >> > >> votes (David, Dhruvil, Boyang). Therefore, the KIP vote
> > >> passes.
> > >> > > > I'll
> > >> > > > >> mark
> > >> > > > >> > >> KIP as accepted and start working on the implementation.
> > >> > > > >> > >>
> > >> > > > >> > >> Thanks a lot!
> > >> > > > >> > >>
> > >> > > > >> > >>
> > >> > > > >> > >> Cheers,
> > >> > > > >> > >> Kowshik
> > >> > > > >> > >>
> > >> > > > >> > >> On Mon, Apr 27, 2020 at 12:15 PM Colin McCabe <
> > >> > > cmccabe@apache.org>
> > >> > > > >> wrote:
> > >> > > > >> > >>
> > >> > > > >> > >>> Thanks, Kowshik. +1 (binding)
> > >> > > > >> > >>>
> > >> > > > >> > >>> best,
> > >> > > > >> > >>> Colin
> > >> > > > >> > >>>
> > >> > > > >> > >>> On Sat, Apr 25, 2020, at 13:20, Kowshik Prakasam wrote:
> > >> > > > >> > >>> > Hi Colin,
> > >> > > > >> > >>> >
> > >> > > > >> > >>> > Thanks for the explanation! I agree with you, and I
> > have
> > >> > > updated
> > >> > > > >> the
> > >> > > > >> > >>> > KIP.
> > >> > > > >> > >>> > Here is a link to relevant section:
> > >> > > > >> > >>> >
> > >> > > > >> > >>>
> > >> > > > >>
> > >> > > >
> > >> > >
> > >> >
> > >>
> >
> https://cwiki.apache.org/confluence/display/KAFKA/KIP-584%3A+Versioning+scheme+for+features#KIP-584:Versioningschemeforfeatures-Controller:ZKnodebootstrapwithdefaultvalues
> > >> > > > >> > >>> >
> > >> > > > >> > >>> >
> > >> > > > >> > >>> > Cheers,
> > >> > > > >> > >>> > Kowshik
> > >> > > > >> > >>> >
> > >> > > > >> > >>> > On Fri, Apr 24, 2020 at 8:50 PM Colin McCabe <
> > >> > > > cmccabe@apache.org>
> > >> > > > >> > >>> wrote:
> > >> > > > >> > >>> >
> > >> > > > >> > >>> > > On Fri, Apr 24, 2020, at 00:01, Kowshik Prakasam
> > wrote:
> > >> > > > >> > >>> > > > (Kowshik): Great point! However for case #1, I'm
> > not
> > >> > sure
> > >> > > > why
> > >> > > > >> we
> > >> > > > >> > >>> need to
> > >> > > > >> > >>> > > > create a '/features' ZK node with disabled
> > features.
> > >> > > > Instead,
> > >> > > > >> do
> > >> > > > >> > >>> you see
> > >> > > > >> > >>> > > > any drawback if we just do not create it? i.e. if
> > >> IBP is
> > >> > > > less
> > >> > > > >> than
> > >> > > > >> > >>> 2.6,
> > >> > > > >> > >>> > > the
> > >> > > > >> > >>> > > > controller treats the case as though the
> versioning
> > >> > system
> > >> > > > is
> > >> > > > >> > >>> completely
> > >> > > > >> > >>> > > > disabled, and would not create a non-existing
> > >> > '/features'
> > >> > > > >> node.
> > >> > > > >> > >>> > >
> > >> > > > >> > >>> > > Hi Kowshik,
> > >> > > > >> > >>> > >
> > >> > > > >> > >>> > > When the IBP is less than 2.6, but the software has
> > >> been
> > >> > > > >> upgraded to
> > >> > > > >> > >>> a
> > >> > > > >> > >>> > > state where it supports this KIP, that
> > >> > > > >> > >>> > > means the user is upgrading from an earlier
> version
> > of
> > >> > the
> > >> > > > >> > >>> software. In
> > >> > > > >> > >>> > > this case, we want to start with all the features
> > >> disabled
> > >> > > and
> > >> > > > >> allow
> > >> > > > >> > >>> the
> > >> > > > >> > >>> > > user to enable them when they are ready.
> > >> > > > >> > >>> > >
> > >> > > > >> > >>> > > Enabling all the possible features immediately
> after
> > an
> > >> > > > upgrade
> > >> > > > >> > >>> could be
> > >> > > > >> > >>> > > harmful to the cluster. On the other hand, for a
> new
> > >> > > cluster,
> > >> > > > >> we do
> > >> > > > >> > >>> want
> > >> > > > >> > >>> > > to enable all the possible features immediately . I
> > was
> > >> > > > >> proposing
> > >> > > > >> > >>> this as a
> > >> > > > >> > >>> > > way to distinguish the two cases (since the new
> > cluster
> > >> > will
> > >> > > > >> never be
> > >> > > > >> > >>> > > started with an old IBP).
> > >> > > > >> > >>> > >
> > >> > > > >> > >>> > > > Colin MccCabe wrote:
> > >> > > > >> > >>> > > > > And now, something a little bit bigger (sorry).
> > >> For
> > >> > > > >> finalized
> > >> > > > >> > >>> > > features,
> > >> > > > >> > >>> > > > > why do we need both min_version_level and
> > >> > > > max_version_level?
> > >> > > > >> > >>> Assuming
> > >> > > > >> > >>> > > that
> > >> > > > >> > >>> > > > > we want all the brokers to be on the same
> feature
> > >> > > version
> > >> > > > >> level,
> > >> > > > >> > >>> we
> > >> > > > >> > >>> > > really only care
> > >> > > > >> > >>> > > > > about three numbers for each feature, right?
> The
> > >> > > minimum
> > >> > > > >> > >>> supported
> > >> > > > >> > >>> > > version
> > >> > > > >> > >>> > > > > level, the maximum supported version level, and
> > the
> > >> > > > current
> > >> > > > >> > >>> active
> > >> > > > >> > >>> > > version level.
> > >> > > > >> > >>> > > >
> > >> > > > >> > >>> > > > > We don't actually want different brokers to be
> on
> > >> > > > different
> > >> > > > >> > >>> versions of
> > >> > > > >> > >>> > > > > the same feature, right? So we can just have
> one
> > >> > number
> > >> > > > for
> > >> > > > >> > >>> current
> > >> > > > >> > >>> > > > > version level, rather than two. At least
> that's
> > >> what
> > >> > I
> > >> > > > was
> > >> > > > >> > >>> thinking
> > >> > > > >> > >>> > > -- let
> > >> > > > >> > >>> > > > > me know if I missed something.
> > >> > > > >> > >>> > > >
> > >> > > > >> > >>> > > > (Kowshik): It is my understanding that the
> "current
> > >> > active
> > >> > > > >> version
> > >> > > > >> > >>> level"
> > >> > > > >> > >>> > > > that you have mentioned, is the
> > "max_version_level".
> > >> But
> > >> > > we
> > >> > > > >> still
> > >> > > > >> > >>> > > > maintain/publish both min and max version levels,
> > >> > because,
> > >> > > > the
> > >> > > > >> > >>> detail
> > >> > > > >> > >>> > > about
> > >> > > > >> > >>> > > > min level is useful to external clients. This is
> > >> > described
> > >> > > > >> below.
> > >> > > > >> > >>> > > >
> > >> > > > >> > >>> > > > For any feature F, think of the closed range:
> > >> > > > >> [min_version_level,
> > >> > > > >> > >>> > > > max_version_level] as the range of finalized
> > >> versions,
> > >> > > > that's
> > >> > > > >> > >>> guaranteed
> > >> > > > >> > >>> > > to
> > >> > > > >> > >>> > > > be supported by all brokers in the cluster.
> > >> > > > >> > >>> > > > - "max_version_level" is the finalized highest
> > >> common
> > >> > > > version
> > >> > > > >> > >>> among all
> > >> > > > >> > >>> > > > brokers,
> > >> > > > >> > >>> > > > - "min_version_level" is the finalized lowest
> > common
> > >> > > > version
> > >> > > > >> > >>> among all
> > >> > > > >> > >>> > > > brokers.
> > >> > > > >> > >>> > > >
> > >> > > > >> > >>> > > > Next, think of "client" here as the "user of the
> > new
> > >> > > feature
> > >> > > > >> > >>> versions
> > >> > > > >> > >>> > > > system". Imagine that such a client learns about
> > >> > finalized
> > >> > > > >> feature
> > >> > > > >> > >>> > > > versions, and exercises some logic based on the
> > >> version.
> > >> > > > These
> > >> > > > >> > >>> clients
> > >> > > > >> > >>> > > can
> > >> > > > >> > >>> > > > be of 2 types:
> > >> > > > >> > >>> > > > 1. Some part of the broker code itself could
> behave
> > >> > like a
> > >> > > > >> client
> > >> > > > >> > >>> trying
> > >> > > > >> > >>> > > to
> > >> > > > >> > >>> > > > use some feature that's "internal" to the broker
> > >> > cluster.
> > >> > > > >> Such a
> > >> > > > >> > >>> client
> > >> > > > >> > >>> > > > would learn the latest finalized features via ZK.
> > >> > > > >> > >>> > > > 2. An external system (ex: Streams) could behave
> > >> like a
> > >> > > > >> client,
> > >> > > > >> > >>> trying to
> > >> > > > >> > >>> > > > use some "external" facing feature. Such a client
> > >> would
> > >> > > > learn
> > >> > > > >> > >>> latest
> > >> > > > >> > >>> > > > finalized features via ApiVersionsRequest. Ex:
> > >> > > > >> group_coordinator
> > >> > > > >> > >>> feature
> > >> > > > >> > >>> > > > described in the KIP.
> > >> > > > >> > >>> > > >
> > >> > > > >> > >>> > > > Next, imagine that for F, the max_version_level
> is
> > >> > > > >> successfully
> > >> > > > >> > >>> bumped by
> > >> > > > >> > >>> > > > +1 (via Controller API). Now it is guaranteed
> that
> > >> all
> > >> > > > brokers
> > >> > > > >> > >>> (i.e.
> > >> > > > >> > >>> > > > internal clients) understand max_version_level +
> 1.
> > >> > > However,
> > >> > > > >> it is
> > >> > > > >> > >>> still
> > >> > > > >> > >>> > > > not guaranteed that all external clients have
> > support
> > >> > for
> > >> > > > (or
> > >> > > > >> have
> > >> > > > >> > >>> > > > activated) the logic for the newer version. Why?
> > >> > Because,
> > >> > > > >> this is
> > >> > > > >> > >>> > > > subjective as explained next:
> > >> > > > >> > >>> > > >
> > >> > > > >> > >>> > > > 1. On one hand, imagine F as an internal feature
> > only
> > >> > > > >> relevant to
> > >> > > > >> > >>> > > Brokers.
> > >> > > > >> > >>> > > > The binary for the internal client logic is
> > >> controlled
> > >> > by
> > >> > > > >> Broker
> > >> > > > >> > >>> cluster
> > >> > > > >> > >>> > > > deployments. When shipping a new Broker release,
> we
> > >> > > wouldn't
> > >> > > > >> bump
> > >> > > > >> > >>> max
> > >> > > > >> > >>> > > > "supported" feature version for F by 1, unless we
> > >> have
> > >> > > > >> introduced
> > >> > > > >> > >>> some
> > >> > > > >> > >>> > > new
> > >> > > > >> > >>> > > > logic (with a potentially breaking change) in the
> > >> > Broker.
> > >> > > > >> > >>> Furthermore,
> > >> > > > >> > >>> > > such
> > >> > > > >> > >>> > > > feature logic in the broker should/will not be
> > >> > implemented
> > >> > > > in
> > >> > > > >> a
> > >> > > > >> > >>> way that
> > >> > > > >> > >>> > > it
> > >> > > > >> > >>> > > > would activate logic for an older feature version
> > >> after
> > >> > it
> > >> > > > has
> > >> > > > >> > >>> migrated
> > >> > > > >> > >>> > > to
> > >> > > > >> > >>> > > > using the logic for a newer feature version
> > (because
> > >> > this
> > >> > > > >> could
> > >> > > > >> > >>> break the
> > >> > > > >> > >>> > > > cluster!). For these cases, max_version_level
> will
> > be
> > >> > very
> > >> > > > >> useful
> > >> > > > >> > >>> for
> > >> > > > >> > >>> > > > decision making.
> > >> > > > >> > >>> > > >
> > >> > > > >> > >>> > > > 2. On the other hand, imagine F as an external
> > facing
> > >> > > > feature.
> > >> > > > >> > >>> External
> > >> > > > >> > >>> > > > clients are not within the control of Broker
> > >> cluster. An
> > >> > > > >> external
> > >> > > > >> > >>> client
> > >> > > > >> > >>> > > > may not have upgraded it's code (yet) to use
> > >> > > > >> 'max_version_level +
> > >> > > > >> > >>> 1'.
> > >> > > > >> > >>> > > But,
> > >> > > > >> > >>> > > > the Kafka cluster could have been deployed with
> > >> support
> > >> > > for
> > >> > > > >> > >>> > > > 'max_version_level + 1' of an external facing
> > >> feature.
> > >> > > Now,
> > >> > > > >> these
> > >> > > > >> > >>> > > external
> > >> > > > >> > >>> > > > clients (until an upgrade) are benefitted in
> > learning
> > >> > > "what
> > >> > > > >> is the
> > >> > > > >> > >>> lowest
> > >> > > > >> > >>> > > > common version for F among all brokers?". This is
> > >> where
> > >> > > the
> > >> > > > >> > >>> > > > "min_version_level" becomes useful. Using this, a
> > >> client
> > >> > > > could
> > >> > > > >> > >>> learn the
> > >> > > > >> > >>> > > > specific supported versions that's lower than
> > >> > > > >> max_version_level
> > >> > > > >> > >>> (instead
> > >> > > > >> > >>> > > of
> > >> > > > >> > >>> > > > assuming that all brokers support the range: [1,
> > >> > > > >> > >>> max_version_level]). For
> > >> > > > >> > >>> > > > example, if the cluster deprecates
> > >> "min_version_level",
> > >> > > then
> > >> > > > >> the
> > >> > > > >> > >>> client
> > >> > > > >> > >>> > > > becomes aware because it periodically learns the
> > >> latest
> > >> > > > >> > >>> > > "min_version_level"
> > >> > > > >> > >>> > > > via ApiVersionsRequest.
> > >> > > > >> > >>> > > >
> > >> > > > >> > >>> > >
> > >> > > > >> > >>> > > Thanks for the explanation. I agree that this does
> > >> make
> > >> > > sense
> > >> > > > >> when
> > >> > > > >> > >>> you
> > >> > > > >> > >>> > > take the client perspective into account.
> > >> > > > >> > >>> > >
> > >> > > > >> > >>> > > best,
> > >> > > > >> > >>> > > Colin
> > >> > > > >> > >>> > >
> > >> > > > >> > >>> > >
> > >> > > > >> > >>> > > >
> > >> > > > >> > >>> > > > Cheers,
> > >> > > > >> > >>> > > > Kowshik
> > >> > > > >> > >>> > > >
> > >> > > > >> > >>> > > >
> > >> > > > >> > >>> > > >
> > >> > > > >> > >>> > > >
> > >> > > > >> > >>> > > > On Thu, Apr 23, 2020 at 12:07 PM Colin McCabe <
> > >> > > > >> cmccabe@apache.org>
> > >> > > > >> > >>> > > wrote:
> > >> > > > >> > >>> > > >
> > >> > > > >> > >>> > > > > Hi Kowshik,
> > >> > > > >> > >>> > > > >
> > >> > > > >> > >>> > > > > Thanks again for working on this-- it looks
> > >> great. I
> > >> > > went
> > >> > > > >> over
> > >> > > > >> > >>> the KIP
> > >> > > > >> > >>> > > > > again and have a few more comments.
> > >> > > > >> > >>> > > > >
> > >> > > > >> > >>> > > > > ===
> > >> > > > >> > >>> > > > >
> > >> > > > >> > >>> > > > > It would be good to note that deprecating a
> > feature
> > >> > > > version
> > >> > > > >> (in
> > >> > > > >> > >>> other
> > >> > > > >> > >>> > > > > words, increasing minVersionLevel on the
> broker)
> > >> is an
> > >> > > > >> > >>> incompatible
> > >> > > > >> > >>> > > change,
> > >> > > > >> > >>> > > > > which requires a major release of Kafka.
> > >> > > > >> > >>> > > > >
> > >> > > > >> > >>> > > > > ===
> > >> > > > >> > >>> > > > >
> > >> > > > >> > >>> > > > > I think the strategy for transitioning from not
> > >> > having a
> > >> > > > >> > >>> /features
> > >> > > > >> > >>> > > znode
> > >> > > > >> > >>> > > > > to having one could use some work. The current
> > >> > proposal
> > >> > > is
> > >> > > > >> to
> > >> > > > >> > >>> wait for
> > >> > > > >> > >>> > > all
> > >> > > > >> > >>> > > > > the brokers to fill in their feature znodes and
> > >> then
> > >> > > pick
> > >> > > > >> the
> > >> > > > >> > >>> highest
> > >> > > > >> > >>> > > > > common versions. But that requires blocking in
> > the
> > >> > > > >> controller
> > >> > > > >> > >>> startup
> > >> > > > >> > >>> > > code
> > >> > > > >> > >>> > > > > until the whole cluster is active
> (technically, a
> > >> > point
> > >> > > in
> > >> > > > >> time
> > >> > > > >> > >>> which
> > >> > > > >> > >>> > > we
> > >> > > > >> > >>> > > > > never really know that we have reached...)
> > >> > > > >> > >>> > > > >
> > >> > > > >> > >>> > > > > Instead, I think it would be better to have a
> > >> strategy
> > >> > > > like
> > >> > > > >> this:
> > >> > > > >> > >>> > > > > 1. If the controller comes up and there is no
> > >> > /features
> > >> > > > >> znode
> > >> > > > >> > >>> AND the
> > >> > > > >> > >>> > > IBP
> > >> > > > >> > >>> > > > > is less than 2.6, create a /features znode
> where
> > >> all
> > >> > the
> > >> > > > >> > >>> features are
> > >> > > > >> > >>> > > > > disabled.
> > >> > > > >> > >>> > > > > 2. If the controller comes up and there is no
> > >> > /features
> > >> > > > >> znode
> > >> > > > >> > >>> AND the
> > >> > > > >> > >>> > > IBP
> > >> > > > >> > >>> > > > > is greater than or equal to 2.6, create a
> > /features
> > >> > > znode
> > >> > > > >> where
> > >> > > > >> > >>> all the
> > >> > > > >> > >>> > > > > features are enabled at the highest versions
> > >> supported
> > >> > > by
> > >> > > > >> the
> > >> > > > >> > >>> > > controller.
> > >> > > > >> > >>> > > > >
> > >> > > > >> > >>> > > > > People upgrading from the pre-KIP-584
> > >> > > > >> > >>> <https://issues.apache.org/jira/browse/KIP-584>
> > >> > > > >> > >>> > > > > <https://issues.apache.org/jira/browse/KIP-584
> >
> > >> world
> > >> > > > will
> > >> > > > >> end
> > >> > > > >> > >>> up in
> > >> > > > >> > >>> > > case
> > >> > > > >> > >>> > > > > #1 because they have to do a double roll to
> > >> upgrade,
> > >> > and
> > >> > > > >> during
> > >> > > > >> > >>> the
> > >> > > > >> > >>> > > first
> > >> > > > >> > >>> > > > > roll, the IBP is unchanged. People creating
> new
> > >> > > clusters
> > >> > > > >> from
> > >> > > > >> > >>> scratch
> > >> > > > >> > >>> > > will
> > >> > > > >> > >>> > > > > end up in case #2, which is what we want since
> we
> > >> > don't
> > >> > > > >> want a
> > >> > > > >> > >>> brand
> > >> > > > >> > >>> > > new
> > >> > > > >> > >>> > > > > cluster to be using old feature flag versions.
> > >> > > > >> > >>> > > > >
> > >> > > > >> > >>> > > > > ===
> > >> > > > >> > >>> > > > >
> > >> > > > >> > >>> > > > > UpdateFeaturesResponse#ErrorMessage should
> > specify
> > >> > > > >> > >>> nullableVersions
> > >> > > > >> > >>> > > since
> > >> > > > >> > >>> > > > > null is a valid value here
> > >> > > > >> > >>> > > > >
> > >> > > > >> > >>> > > > > Also, in the message format, the tags we use
> need
> > >> to
> > >> > > start
> > >> > > > >> at 0.
> > >> > > > >> > >>> > > > >
> > >> > > > >> > >>> > > > > ===
> > >> > > > >> > >>> > > > >
> > >> > > > >> > >>> > > > > I don't think we need the
> > >> FEATURE_UPDATE_IN_PROGRESS
> > >> > > error
> > >> > > > >> > >>> code. The
> > >> > > > >> > >>> > > > > controller is basically single-threaded and
> will
> > >> only
> > >> > do
> > >> > > > >> one of
> > >> > > > >> > >>> these
> > >> > > > >> > >>> > > > > operations at once. Even if it weren't,
> though,
> > we
> > >> > > could
> > >> > > > >> simply
> > >> > > > >> > >>> block
> > >> > > > >> > >>> > > the
> > >> > > > >> > >>> > > > > second operation behind the first one.
> > >> > > > >> > >>> > > > >
> > >> > > > >> > >>> > > > > ===
> > >> > > > >> > >>> > > > >
> > >> > > > >> > >>> > > > > For updateFeatures, it would be good to specify
> > >> that
> > >> > if
> > >> > > a
> > >> > > > >> single
> > >> > > > >> > >>> > > feature
> > >> > > > >> > >>> > > > > version update in the batch can't be done, none
> > of
> > >> > them
> > >> > > > are
> > >> > > > >> > >>> done. I
> > >> > > > >> > >>> > > think
> > >> > > > >> > >>> > > > > this was the intention, but I wasn't able to
> find
> > >> it
> > >> > > > >> spelled out
> > >> > > > >> > >>> > > (maybe i
> > >> > > > >> > >>> > > > > missed it).
> > >> > > > >> > >>> > > > >
> > >> > > > >> > >>> > > > > ===
> > >> > > > >> > >>> > > > >
> > >> > > > >> > >>> > > > > And now, something a little bit bigger (sorry).
> > >> For
> > >> > > > >> finalized
> > >> > > > >> > >>> > > features,
> > >> > > > >> > >>> > > > > why do we need both min_version_level and
> > >> > > > max_version_level?
> > >> > > > >> > >>> Assuming
> > >> > > > >> > >>> > > that
> > >> > > > >> > >>> > > > > we want all the brokers to be on the same
> feature
> > >> > > version
> > >> > > > >> level,
> > >> > > > >> > >>> we
> > >> > > > >> > >>> > > really
> > >> > > > >> > >>> > > > > only care about three numbers for each feature,
> > >> right?
> > >> > > > The
> > >> > > > >> > >>> minimum
> > >> > > > >> > >>> > > > > supported version level, the maximum supported
> > >> version
> > >> > > > >> level,
> > >> > > > >> > >>> and the
> > >> > > > >> > >>> > > > > current active version level.
> > >> > > > >> > >>> > > > >
> > >> > > > >> > >>> > > > > We don't actually want different brokers to be
> on
> > >> > > > different
> > >> > > > >> > >>> versions of
> > >> > > > >> > >>> > > > > the same feature, right? So we can just have
> one
> > >> > number
> > >> > > > for
> > >> > > > >> > >>> current
> > >> > > > >> > >>> > > > > version level, rather than two. At least
> that's
> > >> what
> > >> > I
> > >> > > > was
> > >> > > > >> > >>> thinking
> > >> > > > >> > >>> > > -- let
> > >> > > > >> > >>> > > > > me know if I missed something.
> > >> > > > >> > >>> > > > >
> > >> > > > >> > >>> > > > > best,
> > >> > > > >> > >>> > > > > Colin
> > >> > > > >> > >>> > > > >
> > >> > > > >> > >>> > > > >
> > >> > > > >> > >>> > > > > On Tue, Apr 21, 2020, at 13:01, Dhruvil Shah
> > wrote:
> > >> > > > >> > >>> > > > > > Thanks for the KIP! +1 (non-binding)
> > >> > > > >> > >>> > > > > >
> > >> > > > >> > >>> > > > > > On Tue, Apr 21, 2020 at 6:09 AM David Jacot <
> > >> > > > >> > >>> djacot@confluent.io>
> > >> > > > >> > >>> > > wrote:
> > >> > > > >> > >>> > > > > >
> > >> > > > >> > >>> > > > > > > Great KIP, thanks! +1 (non-binding)
> > >> > > > >> > >>> > > > > > >
> > >> > > > >> > >>> > > > > > > On Fri, Apr 17, 2020 at 8:56 PM Guozhang
> > Wang <
> > >> > > > >> > >>> wangguoz@gmail.com>
> > >> > > > >> > >>> > > > > wrote:
> > >> > > > >> > >>> > > > > > >
> > >> > > > >> > >>> > > > > > > > Thanks for the great KIP Kowshik, +1
> > >> (binding).
> > >> > > > >> > >>> > > > > > > >
> > >> > > > >> > >>> > > > > > > > On Fri, Apr 17, 2020 at 11:22 AM Jun Rao
> <
> > >> > > > >> jun@confluent.io
> > >> > > > >> > >>> >
> > >> > > > >> > >>> > > wrote:
> > >> > > > >> > >>> > > > > > > >
> > >> > > > >> > >>> > > > > > > > > Hi, Kowshik,
> > >> > > > >> > >>> > > > > > > > >
> > >> > > > >> > >>> > > > > > > > > Thanks for the KIP. +1
> > >> > > > >> > >>> > > > > > > > >
> > >> > > > >> > >>> > > > > > > > > Jun
> > >> > > > >> > >>> > > > > > > > >
> > >> > > > >> > >>> > > > > > > > > On Thu, Apr 16, 2020 at 11:14 AM
> Kowshik
> > >> > > Prakasam
> > >> > > > <
> > >> > > > >> > >>> > > > > > > > kprakasam@confluent.io>
> > >> > > > >> > >>> > > > > > > > > wrote:
> > >> > > > >> > >>> > > > > > > > >
> > >> > > > >> > >>> > > > > > > > > > Hi all,
> > >> > > > >> > >>> > > > > > > > > >
> > >> > > > >> > >>> > > > > > > > > > I'd like to start a vote for KIP-584
> > >> > > > >> > >>> <https://issues.apache.org/jira/browse/KIP-584>
> > >> > > > >> > >>> > > > > <https://issues.apache.org/jira/browse/KIP-584
> >.
> > >> The
> > >> > > link
> > >> > > > >> to
> > >> > > > >> > >>> the KIP
> > >> > > > >> > >>> > > can
> > >> > > > >> > >>> > > > > be
> > >> > > > >> > >>> > > > > > > found
> > >> > > > >> > >>> > > > > > > > > > here:
> > >> > > > >> > >>> > > > > > > > > >
> > >> > > > >> > >>> > > > > > > > > >
> > >> > > > >> > >>> > > > > > > > >
> > >> > > > >> > >>> > > > > > > >
> > >> > > > >> > >>> > > > > > >
> > >> > > > >> > >>> > > > >
> > >> > > > >> > >>> > >
> > >> > > > >> > >>>
> > >> > > > >>
> > >> > > >
> > >> > >
> > >> >
> > >>
> >
> https://cwiki.apache.org/confluence/display/KAFKA/KIP-584%3A+Versioning+scheme+for+features
> > >> > > > >> > >>> > > > > > > > > > .
> > >> > > > >> > >>> > > > > > > > > >
> > >> > > > >> > >>> > > > > > > > > > Thanks!
> > >> > > > >> > >>> > > > > > > > > >
> > >> > > > >> > >>> > > > > > > > > >
> > >> > > > >> > >>> > > > > > > > > > Cheers,
> > >> > > > >> > >>> > > > > > > > > > Kowshik
> > >> > > > >> > >>> > > > > > > > > >
> > >> > > > >> > >>> > > > > > > > >
> > >> > > > >> > >>> > > > > > > >
> > >> > > > >> > >>> > > > > > > >
> > >> > > > >> > >>> > > > > > > > --
> > >> > > > >> > >>> > > > > > > > -- Guozhang
> > >> > > > >> > >>> > > > > > > >
> > >> > > > >> > >>> > > > > > >
> > >> > > > >> > >>> > > > > >
> > >> > > > >> > >>> > > > >
> > >> > > > >> > >>> > > >
> > >> > > > >> > >>> > >
> > >> > > > >> > >>> >
> > >> > > > >> > >>>
> > >> > > > >> > >>
> > >> > > > >> >
> > >> > > > >>
> > >> > > > >
> > >> > > >
> > >> > >
> > >> >
> > >>
> > >
> >
>
Re: [VOTE] KIP-584: Versioning scheme for features
Posted by Jun Rao <ju...@confluent.io>.
Hi, Kowshik,
Thanks for the update. Those changes look good to me.
Jun
On Tue, Oct 13, 2020 at 4:50 PM Kowshik Prakasam <kp...@confluent.io>
wrote:
> Hi all,
>
> I wanted to let you know that I have made the following minor changes to
> the `kafka-features` CLI tool description in the KIP-584 write up. The
> purpose is to ensure the design is correct for a few things which came up
> during implementation:
>
> 1. The CLI tool now produces a tab-formatted output instead of JSON. This
> aligns with the type of format produced by other admin CLI tools of Kafka,
> ex: `kafka-topics`.
> 2. Whenever feature updates are performed, the output of the CLI tool shows
> the result of each feature update that was applied.
> 3. The CLI tool accepts an optional argument `--dry-run` which lets the
> user preview the feature updates before applying them.
>
> The following section of the KIP has been updated with the above changes:
>
> https://cwiki.apache.org/confluence/display/KAFKA/KIP-584%3A+Versioning+scheme+for+features#KIP584:Versioningschemeforfeatures-Toolingsupport
>
> Please let me know if you have any questions.
>
>
> Cheers,
> Kowshik
>
>
> On Thu, Oct 8, 2020 at 1:12 AM Kowshik Prakasam <kp...@confluent.io>
> wrote:
>
> > Hi Jun,
> >
> > This is a very good point. I have updated the feature version deprecation
> > section mentioning the same:
> >
> https://cwiki.apache.org/confluence/display/KAFKA/KIP-584%3A+Versioning+scheme+for+features#KIP584:Versioningschemeforfeatures-Featureversiondeprecation
> > .
> >
> > Thank you for the suggestion.
> >
> >
> > Cheers,
> > Kowshik
> >
> >
> > On Tue, Oct 6, 2020 at 5:30 PM Jun Rao <ju...@confluent.io> wrote:
> >
> >> Hi, Kowshik,
> >>
> >> Thanks for the follow up. Both look good to me.
> >>
> >> For 2, it would be useful to also add that an admin should make sure
> that
> >> no clients are using a deprecated feature version (e.g. using the client
> >> version metric) before deploying a release that deprecates it.
> >>
> >> Thanks,
> >>
> >> Jun
> >>
> >> On Tue, Oct 6, 2020 at 3:46 PM Kowshik Prakasam <kprakasam@confluent.io
> >
> >> wrote:
> >>
> >> > Hi Jun,
> >> >
> >> > I have added the following details in the KIP-584 write up:
> >> >
> >> > 1. Deployment, IBP deprecation and avoidance of double rolls. This
> >> section
> >> > talks about the various phases of work that would be required to use
> >> this
> >> > KIP to eventually avoid Broker double rolls in the cluster (whenever
> IBP
> >> > values are advanced). Link to section:
> >> >
> >> >
> >>
> https://cwiki.apache.org/confluence/display/KAFKA/KIP-584%3A+Versioning+scheme+for+features#KIP584:Versioningschemeforfeatures-Deployment,IBPdeprecationandavoidanceofdoublerolls
> >> > .
> >> >
> >> > 2. Feature version deprecation. This section explains the idea for
> >> feature
> >> > version deprecation (using highest supported feature min version)
> which
> >> you
> >> > had proposed during code review:
> >> >
> >> >
> >>
> https://cwiki.apache.org/confluence/display/KAFKA/KIP-584%3A+Versioning+scheme+for+features#KIP584:Versioningschemeforfeatures-Featureversiondeprecation
> >> > .
> >> >
> >> > Please let me know if you have any questions.
> >> >
> >> >
> >> > Cheers,
> >> > Kowshik
> >> >
> >> >
> >> > On Tue, Sep 29, 2020 at 11:07 AM Jun Rao <ju...@confluent.io> wrote:
> >> >
> >> > > Hi, Kowshik,
> >> > >
> >> > > Thanks for the update. Regarding enabling a single rolling restart
> in
> >> the
> >> > > future, could we sketch out a bit how this will work by treating IBP
> >> as a
> >> > > feature? For example, IBP currently uses the release version and
> this
> >> KIP
> >> > > uses an integer for versions. How do we bridge the gap between the
> >> two?
> >> > > Does min.version still make sense for IBP as a feature?
> >> > >
> >> > > Thanks,
> >> > >
> >> > > Jun
> >> > >
> >> > > On Fri, Sep 25, 2020 at 5:57 PM Kowshik Prakasam <
> >> kprakasam@confluent.io
> >> > >
> >> > > wrote:
> >> > >
> >> > > > Hi Colin,
> >> > > >
> >> > > > Thanks for the feedback. Those are very good points. I have made
> the
> >> > > > following changes to the KIP as you had suggested:
> >> > > > 1. Included the `timeoutMs` field in the `UpdateFeaturesRequest`
> >> > schema.
> >> > > > The initial implementation won't be making use of the field, but
> we
> >> can
> >> > > > always use it in the future as the need arises.
> >> > > > 2. Modified the `FinalizedFeaturesEpoch` field in
> >> `ApiVersionsResponse`
> >> > > to
> >> > > > use int64. This is to avoid overflow problems in the future once
> ZK
> >> is
> >> > > > gone.
> >> > > >
> >> > > > I have also incorporated these changes into the versioning write
> >> path
> >> > PR
> >> > > > that is currently under review:
> >> > > https://github.com/apache/kafka/pull/9001.
> >> > > >
> >> > > >
> >> > > > Cheers,
> >> > > > Kowshik
> >> > > >
> >> > > >
> >> > > >
> >> > > > On Fri, Sep 25, 2020 at 4:57 PM Kowshik Prakasam <
> >> > kprakasam@confluent.io
> >> > > >
> >> > > > wrote:
> >> > > >
> >> > > > > Hi Jun,
> >> > > > >
> >> > > > > Thanks for the feedback. It's a very good point. I have now
> >> modified
> >> > > the
> >> > > > > KIP-584 write-up "goals" section a bit. It now mentions one of
> the
> >> > > goals
> >> > > > as
> >> > > > > enabling rolling upgrades using a single restart (instead of 2).
> >> > Also I
> >> > > > > have removed the text explicitly aiming for deprecation of IBP.
> >> Note
> >> > > that
> >> > > > > previously under "Potential features in Kafka" the IBP was
> >> mentioned
> >> > > > under
> >> > > > > point (4) as a possible coarse-grained feature. Hopefully, now
> >> the 2
> >> > > > > sections of the KIP align with each other well.
> >> > > > >
> >> > > > >
> >> > > > > Cheers,
> >> > > > > Kowshik
> >> > > > >
> >> > > > >
> >> > > > > On Fri, Sep 25, 2020 at 2:03 PM Colin McCabe <
> cmccabe@apache.org>
> >> > > wrote:
> >> > > > >
> >> > > > >> On Tue, Sep 22, 2020, at 00:43, Kowshik Prakasam wrote:
> >> > > > >> > Hi all,
> >> > > > >> >
> >> > > > >> > I wanted to let you know that I have made the following
> >> changes to
> >> > > the
> >> > > > >> > KIP-584 write up. The purpose is to ensure the design is
> >> correct
> >> > > for a
> >> > > > >> few
> >> > > > >> > things which came up during implementation:
> >> > > > >> >
> >> > > > >>
> >> > > > >> Hi Kowshik,
> >> > > > >>
> >> > > > >> Thanks for the updates.
> >> > > > >>
> >> > > > >> >
> >> > > > >> > 1. Per FeatureUpdate error code: The UPDATE_FEATURES
> controller
> >> > API
> >> > > is
> >> > > > >> no
> >> > > > >> > longer transactional. Going forward, we allow for individual
> >> > > > >> FeatureUpdate
> >> > > > >> > to succeed/fail in the request. As a result, the response
> >> schema
> >> > now
> >> > > > >> > contains an error code per FeatureUpdate as well as a
> top-level
> >> > > error
> >> > > > >> code.
> >> > > > >> > Overall this is a better design because it better represents
> >> the
> >> > > > nature
> >> > > > >> of
> >> > > > >> > the API: each FeatureUpdate in the request is independent of
> >> the
> >> > > other
> >> > > > >> > updates, and the controller can process/apply these
> >> independently
> >> > to
> >> > > > ZK.
> >> > > > >> > When an UPDATE_FEATURES request fails, this new design
> provides
> >> > > better
> >> > > > >> > clarity to the caller on which FeatureUpdate could not be
> >> applied
> >> > > (via
> >> > > > >> the
> >> > > > >> > individual error codes). In the previous design, we were
> >> unable to
> >> > > > >> achieve
> >> > > > >> > such an increased level of clarity in communicating the error
> >> > codes.
> >> > > > >> >
> >> > > > >>
> >> > > > >> OK
> >> > > > >>
> >> > > > >> >
> >> > > > >> > 2. Due to #1, there were some minor changes required to the
> >> > proposed
> >> > > > >> Admin
> >> > > > >> > APIs (describeFeatures and updateFeatures). A few unnecessary
> >> > public
> >> > > > >> APIs
> >> > > > >> > have been removed, and couple essential ones have been added.
> >> The
> >> > > > latest
> >> > > > >> > changes now represent the latest design.
> >> > > > >> >
> >> > > > >> > 3. The timeoutMs field has been removed from the the
> >> > UPDATE_FEATURES
> >> > > > API
> >> > > > >> > request, since it was not found to be required during
> >> > > implementation.
> >> > > > >> >
> >> > > > >>
> >> > > > >> Please don't get rid of timeoutMs. timeoutMs is required if
> you
> >> > want
> >> > > to
> >> > > > >> implement the ability to timeout the call if the controller
> can't
> >> > get
> >> > > > to it
> >> > > > >> in time. This is important for avoiding congestion collapse
> >> where
> >> > the
> >> > > > >> controller collapses under the weight of lots of retries of the
> >> same
> >> > > > set of
> >> > > > >> calls.
> >> > > > >>
> >> > > > >> We may not be able to do it in the initial implementation, but
> we
> >> > will
> >> > > > >> eventually implement this for all the controller-bound RPCs.
> >> > > > >>
> >> > > > >> > >
> >> > > > >> > > 2. Finalized feature version epoch data type has been made
> >> to be
> >> > > > int32
> >> > > > >> > > (instead of int64). The reason is that the epoch value is
> the
> >> > > value
> >> > > > >> of ZK
> >> > > > >> > > node version, whose data type is int32.
> >> > > > >> > >
> >> > > > >>
> >> > > > >> Sorry, I missed this earlier. Using 16 bit feature levels
> seems
> >> > fine.
> >> > > > >> However, please don't use a 32-bit epoch here. We deliberately
> >> made
> >> > > the
> >> > > > >> epoch 64 bits to avoid overflow problems in the future once ZK
> is
> >> > > gone.
> >> > > > >>
> >> > > > >> best,
> >> > > > >> Colin
> >> > > > >>
> >> > > > >> > > 3. Introduced a new 'status' field in the '/features' ZK
> node
> >> > > > schema.
> >> > > > >> The
> >> > > > >> > > purpose is to implement Colin's earlier point for the
> >> strategy
> >> > for
> >> > > > >> > > transitioning from not having a /features znode to having
> >> one.
> >> > An
> >> > > > >> > > explanation has been provided in the following section of
> the
> >> > KIP
> >> > > > >> detailing
> >> > > > >> > > the different cases:
> >> > > > >> > >
> >> > > > >>
> >> > > >
> >> > >
> >> >
> >>
> https://cwiki.apache.org/confluence/display/KAFKA/KIP-584%3A+Versioning+scheme+for+features#KIP584:Versioningschemeforfeatures-FeatureZKnodestatus
> >> > > > >> > > .
> >> > > > >> > >
> >> > > > >> > > Please let me know if you have any questions or concerns.
> >> > > > >> > >
> >> > > > >> > >
> >> > > > >> > > Cheers,
> >> > > > >> > > Kowshik
> >> > > > >> > >
> >> > > > >> > >
> >> > > > >> > >
> >> > > > >> > > Cheers,
> >> > > > >> > > Kowshik
> >> > > > >> > >
> >> > > > >> > > On Tue, Apr 28, 2020 at 11:24 PM Kowshik Prakasam <
> >> > > > >> kprakasam@confluent.io>
> >> > > > >> > > wrote:
> >> > > > >> > >
> >> > > > >> > >> Hi all,
> >> > > > >> > >>
> >> > > > >> > >> This KIP vote has been open for ~12 days. The summary of
> the
> >> > > votes
> >> > > > is
> >> > > > >> > >> that we have 3 binding votes (Colin, Guozhang, Jun), and 3
> >> > > > >> non-binding
> >> > > > >> > >> votes (David, Dhruvil, Boyang). Therefore, the KIP vote
> >> passes.
> >> > > > I'll
> >> > > > >> mark
> >> > > > >> > >> KIP as accepted and start working on the implementation.
> >> > > > >> > >>
> >> > > > >> > >> Thanks a lot!
> >> > > > >> > >>
> >> > > > >> > >>
> >> > > > >> > >> Cheers,
> >> > > > >> > >> Kowshik
> >> > > > >> > >>
> >> > > > >> > >> On Mon, Apr 27, 2020 at 12:15 PM Colin McCabe <
> >> > > cmccabe@apache.org>
> >> > > > >> wrote:
> >> > > > >> > >>
> >> > > > >> > >>> Thanks, Kowshik. +1 (binding)
> >> > > > >> > >>>
> >> > > > >> > >>> best,
> >> > > > >> > >>> Colin
> >> > > > >> > >>>
> >> > > > >> > >>> On Sat, Apr 25, 2020, at 13:20, Kowshik Prakasam wrote:
> >> > > > >> > >>> > Hi Colin,
> >> > > > >> > >>> >
> >> > > > >> > >>> > Thanks for the explanation! I agree with you, and I
> have
> >> > > updated
> >> > > > >> the
> >> > > > >> > >>> > KIP.
> >> > > > >> > >>> > Here is a link to relevant section:
> >> > > > >> > >>> >
> >> > > > >> > >>>
> >> > > > >>
> >> > > >
> >> > >
> >> >
> >>
> https://cwiki.apache.org/confluence/display/KAFKA/KIP-584%3A+Versioning+scheme+for+features#KIP-584:Versioningschemeforfeatures-Controller:ZKnodebootstrapwithdefaultvalues
> >> > > > >> > >>> >
> >> > > > >> > >>> >
> >> > > > >> > >>> > Cheers,
> >> > > > >> > >>> > Kowshik
> >> > > > >> > >>> >
> >> > > > >> > >>> > On Fri, Apr 24, 2020 at 8:50 PM Colin McCabe <
> >> > > > cmccabe@apache.org>
> >> > > > >> > >>> wrote:
> >> > > > >> > >>> >
> >> > > > >> > >>> > > On Fri, Apr 24, 2020, at 00:01, Kowshik Prakasam
> wrote:
> >> > > > >> > >>> > > > (Kowshik): Great point! However for case #1, I'm
> not
> >> > sure
> >> > > > why
> >> > > > >> we
> >> > > > >> > >>> need to
> >> > > > >> > >>> > > > create a '/features' ZK node with disabled
> features.
> >> > > > Instead,
> >> > > > >> do
> >> > > > >> > >>> you see
> >> > > > >> > >>> > > > any drawback if we just do not create it? i.e. if
> >> IBP is
> >> > > > less
> >> > > > >> than
> >> > > > >> > >>> 2.6,
> >> > > > >> > >>> > > the
> >> > > > >> > >>> > > > controller treats the case as though the versioning
> >> > system
> >> > > > is
> >> > > > >> > >>> completely
> >> > > > >> > >>> > > > disabled, and would not create a non-existing
> >> > '/features'
> >> > > > >> node.
> >> > > > >> > >>> > >
> >> > > > >> > >>> > > Hi Kowshik,
> >> > > > >> > >>> > >
> >> > > > >> > >>> > > When the IBP is less than 2.6, but the software has
> >> been
> >> > > > >> upgraded to
> >> > > > >> > >>> a
> >> > > > >> > >>> > > state where it supports this KIP, that
> >> > > > >> > >>> > > means the user is upgrading from an earlier version
> of
> >> > the
> >> > > > >> > >>> software. In
> >> > > > >> > >>> > > this case, we want to start with all the features
> >> disabled
> >> > > and
> >> > > > >> allow
> >> > > > >> > >>> the
> >> > > > >> > >>> > > user to enable them when they are ready.
> >> > > > >> > >>> > >
> >> > > > >> > >>> > > Enabling all the possible features immediately after
> an
> >> > > > upgrade
> >> > > > >> > >>> could be
> >> > > > >> > >>> > > harmful to the cluster. On the other hand, for a new
> >> > > cluster,
> >> > > > >> we do
> >> > > > >> > >>> want
> >> > > > >> > >>> > > to enable all the possible features immediately . I
> was
> >> > > > >> proposing
> >> > > > >> > >>> this as a
> >> > > > >> > >>> > > way to distinguish the two cases (since the new
> cluster
> >> > will
> >> > > > >> never be
> >> > > > >> > >>> > > started with an old IBP).
> >> > > > >> > >>> > >
> >> > > > >> > >>> > > > Colin MccCabe wrote:
> >> > > > >> > >>> > > > > And now, something a little bit bigger (sorry).
> >> For
> >> > > > >> finalized
> >> > > > >> > >>> > > features,
> >> > > > >> > >>> > > > > why do we need both min_version_level and
> >> > > > max_version_level?
> >> > > > >> > >>> Assuming
> >> > > > >> > >>> > > that
> >> > > > >> > >>> > > > > we want all the brokers to be on the same feature
> >> > > version
> >> > > > >> level,
> >> > > > >> > >>> we
> >> > > > >> > >>> > > really only care
> >> > > > >> > >>> > > > > about three numbers for each feature, right? The
> >> > > minimum
> >> > > > >> > >>> supported
> >> > > > >> > >>> > > version
> >> > > > >> > >>> > > > > level, the maximum supported version level, and
> the
> >> > > > current
> >> > > > >> > >>> active
> >> > > > >> > >>> > > version level.
> >> > > > >> > >>> > > >
> >> > > > >> > >>> > > > > We don't actually want different brokers to be on
> >> > > > different
> >> > > > >> > >>> versions of
> >> > > > >> > >>> > > > > the same feature, right? So we can just have one
> >> > number
> >> > > > for
> >> > > > >> > >>> current
> >> > > > >> > >>> > > > > version level, rather than two. At least that's
> >> what
> >> > I
> >> > > > was
> >> > > > >> > >>> thinking
> >> > > > >> > >>> > > -- let
> >> > > > >> > >>> > > > > me know if I missed something.
> >> > > > >> > >>> > > >
> >> > > > >> > >>> > > > (Kowshik): It is my understanding that the "current
> >> > active
> >> > > > >> version
> >> > > > >> > >>> level"
> >> > > > >> > >>> > > > that you have mentioned, is the
> "max_version_level".
> >> But
> >> > > we
> >> > > > >> still
> >> > > > >> > >>> > > > maintain/publish both min and max version levels,
> >> > because,
> >> > > > the
> >> > > > >> > >>> detail
> >> > > > >> > >>> > > about
> >> > > > >> > >>> > > > min level is useful to external clients. This is
> >> > described
> >> > > > >> below.
> >> > > > >> > >>> > > >
> >> > > > >> > >>> > > > For any feature F, think of the closed range:
> >> > > > >> [min_version_level,
> >> > > > >> > >>> > > > max_version_level] as the range of finalized
> >> versions,
> >> > > > that's
> >> > > > >> > >>> guaranteed
> >> > > > >> > >>> > > to
> >> > > > >> > >>> > > > be supported by all brokers in the cluster.
> >> > > > >> > >>> > > > - "max_version_level" is the finalized highest
> >> common
> >> > > > version
> >> > > > >> > >>> among all
> >> > > > >> > >>> > > > brokers,
> >> > > > >> > >>> > > > - "min_version_level" is the finalized lowest
> common
> >> > > > version
> >> > > > >> > >>> among all
> >> > > > >> > >>> > > > brokers.
> >> > > > >> > >>> > > >
> >> > > > >> > >>> > > > Next, think of "client" here as the "user of the
> new
> >> > > feature
> >> > > > >> > >>> versions
> >> > > > >> > >>> > > > system". Imagine that such a client learns about
> >> > finalized
> >> > > > >> feature
> >> > > > >> > >>> > > > versions, and exercises some logic based on the
> >> version.
> >> > > > These
> >> > > > >> > >>> clients
> >> > > > >> > >>> > > can
> >> > > > >> > >>> > > > be of 2 types:
> >> > > > >> > >>> > > > 1. Some part of the broker code itself could behave
> >> > like a
> >> > > > >> client
> >> > > > >> > >>> trying
> >> > > > >> > >>> > > to
> >> > > > >> > >>> > > > use some feature that's "internal" to the broker
> >> > cluster.
> >> > > > >> Such a
> >> > > > >> > >>> client
> >> > > > >> > >>> > > > would learn the latest finalized features via ZK.
> >> > > > >> > >>> > > > 2. An external system (ex: Streams) could behave
> >> like a
> >> > > > >> client,
> >> > > > >> > >>> trying to
> >> > > > >> > >>> > > > use some "external" facing feature. Such a client
> >> would
> >> > > > learn
> >> > > > >> > >>> latest
> >> > > > >> > >>> > > > finalized features via ApiVersionsRequest. Ex:
> >> > > > >> group_coordinator
> >> > > > >> > >>> feature
> >> > > > >> > >>> > > > described in the KIP.
> >> > > > >> > >>> > > >
> >> > > > >> > >>> > > > Next, imagine that for F, the max_version_level is
> >> > > > >> successfully
> >> > > > >> > >>> bumped by
> >> > > > >> > >>> > > > +1 (via Controller API). Now it is guaranteed that
> >> all
> >> > > > brokers
> >> > > > >> > >>> (i.e.
> >> > > > >> > >>> > > > internal clients) understand max_version_level + 1.
> >> > > However,
> >> > > > >> it is
> >> > > > >> > >>> still
> >> > > > >> > >>> > > > not guaranteed that all external clients have
> support
> >> > for
> >> > > > (or
> >> > > > >> have
> >> > > > >> > >>> > > > activated) the logic for the newer version. Why?
> >> > Because,
> >> > > > >> this is
> >> > > > >> > >>> > > > subjective as explained next:
> >> > > > >> > >>> > > >
> >> > > > >> > >>> > > > 1. On one hand, imagine F as an internal feature
> only
> >> > > > >> relevant to
> >> > > > >> > >>> > > Brokers.
> >> > > > >> > >>> > > > The binary for the internal client logic is
> >> controlled
> >> > by
> >> > > > >> Broker
> >> > > > >> > >>> cluster
> >> > > > >> > >>> > > > deployments. When shipping a new Broker release, we
> >> > > wouldn't
> >> > > > >> bump
> >> > > > >> > >>> max
> >> > > > >> > >>> > > > "supported" feature version for F by 1, unless we
> >> have
> >> > > > >> introduced
> >> > > > >> > >>> some
> >> > > > >> > >>> > > new
> >> > > > >> > >>> > > > logic (with a potentially breaking change) in the
> >> > Broker.
> >> > > > >> > >>> Furthermore,
> >> > > > >> > >>> > > such
> >> > > > >> > >>> > > > feature logic in the broker should/will not be
> >> > implemented
> >> > > > in
> >> > > > >> a
> >> > > > >> > >>> way that
> >> > > > >> > >>> > > it
> >> > > > >> > >>> > > > would activate logic for an older feature version
> >> after
> >> > it
> >> > > > has
> >> > > > >> > >>> migrated
> >> > > > >> > >>> > > to
> >> > > > >> > >>> > > > using the logic for a newer feature version
> (because
> >> > this
> >> > > > >> could
> >> > > > >> > >>> break the
> >> > > > >> > >>> > > > cluster!). For these cases, max_version_level will
> be
> >> > very
> >> > > > >> useful
> >> > > > >> > >>> for
> >> > > > >> > >>> > > > decision making.
> >> > > > >> > >>> > > >
> >> > > > >> > >>> > > > 2. On the other hand, imagine F as an external
> facing
> >> > > > feature.
> >> > > > >> > >>> External
> >> > > > >> > >>> > > > clients are not within the control of Broker
> >> cluster. An
> >> > > > >> external
> >> > > > >> > >>> client
> >> > > > >> > >>> > > > may not have upgraded it's code (yet) to use
> >> > > > >> 'max_version_level +
> >> > > > >> > >>> 1'.
> >> > > > >> > >>> > > But,
> >> > > > >> > >>> > > > the Kafka cluster could have been deployed with
> >> support
> >> > > for
> >> > > > >> > >>> > > > 'max_version_level + 1' of an external facing
> >> feature.
> >> > > Now,
> >> > > > >> these
> >> > > > >> > >>> > > external
> >> > > > >> > >>> > > > clients (until an upgrade) are benefitted in
> learning
> >> > > "what
> >> > > > >> is the
> >> > > > >> > >>> lowest
> >> > > > >> > >>> > > > common version for F among all brokers?". This is
> >> where
> >> > > the
> >> > > > >> > >>> > > > "min_version_level" becomes useful. Using this, a
> >> client
> >> > > > could
> >> > > > >> > >>> learn the
> >> > > > >> > >>> > > > specific supported versions that's lower than
> >> > > > >> max_version_level
> >> > > > >> > >>> (instead
> >> > > > >> > >>> > > of
> >> > > > >> > >>> > > > assuming that all brokers support the range: [1,
> >> > > > >> > >>> max_version_level]). For
> >> > > > >> > >>> > > > example, if the cluster deprecates
> >> "min_version_level",
> >> > > then
> >> > > > >> the
> >> > > > >> > >>> client
> >> > > > >> > >>> > > > becomes aware because it periodically learns the
> >> latest
> >> > > > >> > >>> > > "min_version_level"
> >> > > > >> > >>> > > > via ApiVersionsRequest.
> >> > > > >> > >>> > > >
> >> > > > >> > >>> > >
> >> > > > >> > >>> > > Thanks for the explanation. I agree that this does
> >> make
> >> > > sense
> >> > > > >> when
> >> > > > >> > >>> you
> >> > > > >> > >>> > > take the client perspective into account.
> >> > > > >> > >>> > >
> >> > > > >> > >>> > > best,
> >> > > > >> > >>> > > Colin
> >> > > > >> > >>> > >
> >> > > > >> > >>> > >
> >> > > > >> > >>> > > >
> >> > > > >> > >>> > > > Cheers,
> >> > > > >> > >>> > > > Kowshik
> >> > > > >> > >>> > > >
> >> > > > >> > >>> > > >
> >> > > > >> > >>> > > >
> >> > > > >> > >>> > > >
> >> > > > >> > >>> > > > On Thu, Apr 23, 2020 at 12:07 PM Colin McCabe <
> >> > > > >> cmccabe@apache.org>
> >> > > > >> > >>> > > wrote:
> >> > > > >> > >>> > > >
> >> > > > >> > >>> > > > > Hi Kowshik,
> >> > > > >> > >>> > > > >
> >> > > > >> > >>> > > > > Thanks again for working on this-- it looks
> >> great. I
> >> > > went
> >> > > > >> over
> >> > > > >> > >>> the KIP
> >> > > > >> > >>> > > > > again and have a few more comments.
> >> > > > >> > >>> > > > >
> >> > > > >> > >>> > > > > ===
> >> > > > >> > >>> > > > >
> >> > > > >> > >>> > > > > It would be good to note that deprecating a
> feature
> >> > > > version
> >> > > > >> (in
> >> > > > >> > >>> other
> >> > > > >> > >>> > > > > words, increasing minVersionLevel on the broker)
> >> is an
> >> > > > >> > >>> incompatible
> >> > > > >> > >>> > > change,
> >> > > > >> > >>> > > > > which requires a major release of Kafka.
> >> > > > >> > >>> > > > >
> >> > > > >> > >>> > > > > ===
> >> > > > >> > >>> > > > >
> >> > > > >> > >>> > > > > I think the strategy for transitioning from not
> >> > having a
> >> > > > >> > >>> /features
> >> > > > >> > >>> > > znode
> >> > > > >> > >>> > > > > to having one could use some work. The current
> >> > proposal
> >> > > is
> >> > > > >> to
> >> > > > >> > >>> wait for
> >> > > > >> > >>> > > all
> >> > > > >> > >>> > > > > the brokers to fill in their feature znodes and
> >> then
> >> > > pick
> >> > > > >> the
> >> > > > >> > >>> highest
> >> > > > >> > >>> > > > > common versions. But that requires blocking in
> the
> >> > > > >> controller
> >> > > > >> > >>> startup
> >> > > > >> > >>> > > code
> >> > > > >> > >>> > > > > until the whole cluster is active (technically, a
> >> > point
> >> > > in
> >> > > > >> time
> >> > > > >> > >>> which
> >> > > > >> > >>> > > we
> >> > > > >> > >>> > > > > never really know that we have reached...)
> >> > > > >> > >>> > > > >
> >> > > > >> > >>> > > > > Instead, I think it would be better to have a
> >> strategy
> >> > > > like
> >> > > > >> this:
> >> > > > >> > >>> > > > > 1. If the controller comes up and there is no
> >> > /features
> >> > > > >> znode
> >> > > > >> > >>> AND the
> >> > > > >> > >>> > > IBP
> >> > > > >> > >>> > > > > is less than 2.6, create a /features znode where
> >> all
> >> > the
> >> > > > >> > >>> features are
> >> > > > >> > >>> > > > > disabled.
> >> > > > >> > >>> > > > > 2. If the controller comes up and there is no
> >> > /features
> >> > > > >> znode
> >> > > > >> > >>> AND the
> >> > > > >> > >>> > > IBP
> >> > > > >> > >>> > > > > is greater than or equal to 2.6, create a
> /features
> >> > > znode
> >> > > > >> where
> >> > > > >> > >>> all the
> >> > > > >> > >>> > > > > features are enabled at the highest versions
> >> supported
> >> > > by
> >> > > > >> the
> >> > > > >> > >>> > > controller.
> >> > > > >> > >>> > > > >
> >> > > > >> > >>> > > > > People upgrading from the pre-KIP-584
> >> > > > >> > >>> <https://issues.apache.org/jira/browse/KIP-584>
> >> > > > >> > >>> > > > > <https://issues.apache.org/jira/browse/KIP-584>
> >> world
> >> > > > will
> >> > > > >> end
> >> > > > >> > >>> up in
> >> > > > >> > >>> > > case
> >> > > > >> > >>> > > > > #1 because they have to do a double roll to
> >> upgrade,
> >> > and
> >> > > > >> during
> >> > > > >> > >>> the
> >> > > > >> > >>> > > first
> >> > > > >> > >>> > > > > roll, the IBP is unchanged. People creating new
> >> > > clusters
> >> > > > >> from
> >> > > > >> > >>> scratch
> >> > > > >> > >>> > > will
> >> > > > >> > >>> > > > > end up in case #2, which is what we want since we
> >> > don't
> >> > > > >> want a
> >> > > > >> > >>> brand
> >> > > > >> > >>> > > new
> >> > > > >> > >>> > > > > cluster to be using old feature flag versions.
> >> > > > >> > >>> > > > >
> >> > > > >> > >>> > > > > ===
> >> > > > >> > >>> > > > >
> >> > > > >> > >>> > > > > UpdateFeaturesResponse#ErrorMessage should
> specify
> >> > > > >> > >>> nullableVersions
> >> > > > >> > >>> > > since
> >> > > > >> > >>> > > > > null is a valid value here
> >> > > > >> > >>> > > > >
> >> > > > >> > >>> > > > > Also, in the message format, the tags we use need
> >> to
> >> > > start
> >> > > > >> at 0.
> >> > > > >> > >>> > > > >
> >> > > > >> > >>> > > > > ===
> >> > > > >> > >>> > > > >
> >> > > > >> > >>> > > > > I don't think we need the
> >> FEATURE_UPDATE_IN_PROGRESS
> >> > > error
> >> > > > >> > >>> code. The
> >> > > > >> > >>> > > > > controller is basically single-threaded and will
> >> only
> >> > do
> >> > > > >> one of
> >> > > > >> > >>> these
> >> > > > >> > >>> > > > > operations at once. Even if it weren't, though,
> we
> >> > > could
> >> > > > >> simply
> >> > > > >> > >>> block
> >> > > > >> > >>> > > the
> >> > > > >> > >>> > > > > second operation behind the first one.
> >> > > > >> > >>> > > > >
> >> > > > >> > >>> > > > > ===
> >> > > > >> > >>> > > > >
> >> > > > >> > >>> > > > > For updateFeatures, it would be good to specify
> >> that
> >> > if
> >> > > a
> >> > > > >> single
> >> > > > >> > >>> > > feature
> >> > > > >> > >>> > > > > version update in the batch can't be done, none
> of
> >> > them
> >> > > > are
> >> > > > >> > >>> done. I
> >> > > > >> > >>> > > think
> >> > > > >> > >>> > > > > this was the intention, but I wasn't able to find
> >> it
> >> > > > >> spelled out
> >> > > > >> > >>> > > (maybe i
> >> > > > >> > >>> > > > > missed it).
> >> > > > >> > >>> > > > >
> >> > > > >> > >>> > > > > ===
> >> > > > >> > >>> > > > >
> >> > > > >> > >>> > > > > And now, something a little bit bigger (sorry).
> >> For
> >> > > > >> finalized
> >> > > > >> > >>> > > features,
> >> > > > >> > >>> > > > > why do we need both min_version_level and
> >> > > > max_version_level?
> >> > > > >> > >>> Assuming
> >> > > > >> > >>> > > that
> >> > > > >> > >>> > > > > we want all the brokers to be on the same feature
> >> > > version
> >> > > > >> level,
> >> > > > >> > >>> we
> >> > > > >> > >>> > > really
> >> > > > >> > >>> > > > > only care about three numbers for each feature,
> >> right?
> >> > > > The
> >> > > > >> > >>> minimum
> >> > > > >> > >>> > > > > supported version level, the maximum supported
> >> version
> >> > > > >> level,
> >> > > > >> > >>> and the
> >> > > > >> > >>> > > > > current active version level.
> >> > > > >> > >>> > > > >
> >> > > > >> > >>> > > > > We don't actually want different brokers to be on
> >> > > > different
> >> > > > >> > >>> versions of
> >> > > > >> > >>> > > > > the same feature, right? So we can just have one
> >> > number
> >> > > > for
> >> > > > >> > >>> current
> >> > > > >> > >>> > > > > version level, rather than two. At least that's
> >> what
> >> > I
> >> > > > was
> >> > > > >> > >>> thinking
> >> > > > >> > >>> > > -- let
> >> > > > >> > >>> > > > > me know if I missed something.
> >> > > > >> > >>> > > > >
> >> > > > >> > >>> > > > > best,
> >> > > > >> > >>> > > > > Colin
> >> > > > >> > >>> > > > >
> >> > > > >> > >>> > > > >
> >> > > > >> > >>> > > > > On Tue, Apr 21, 2020, at 13:01, Dhruvil Shah
> wrote:
> >> > > > >> > >>> > > > > > Thanks for the KIP! +1 (non-binding)
> >> > > > >> > >>> > > > > >
> >> > > > >> > >>> > > > > > On Tue, Apr 21, 2020 at 6:09 AM David Jacot <
> >> > > > >> > >>> djacot@confluent.io>
> >> > > > >> > >>> > > wrote:
> >> > > > >> > >>> > > > > >
> >> > > > >> > >>> > > > > > > Great KIP, thanks! +1 (non-binding)
> >> > > > >> > >>> > > > > > >
> >> > > > >> > >>> > > > > > > On Fri, Apr 17, 2020 at 8:56 PM Guozhang
> Wang <
> >> > > > >> > >>> wangguoz@gmail.com>
> >> > > > >> > >>> > > > > wrote:
> >> > > > >> > >>> > > > > > >
> >> > > > >> > >>> > > > > > > > Thanks for the great KIP Kowshik, +1
> >> (binding).
> >> > > > >> > >>> > > > > > > >
> >> > > > >> > >>> > > > > > > > On Fri, Apr 17, 2020 at 11:22 AM Jun Rao <
> >> > > > >> jun@confluent.io
> >> > > > >> > >>> >
> >> > > > >> > >>> > > wrote:
> >> > > > >> > >>> > > > > > > >
> >> > > > >> > >>> > > > > > > > > Hi, Kowshik,
> >> > > > >> > >>> > > > > > > > >
> >> > > > >> > >>> > > > > > > > > Thanks for the KIP. +1
> >> > > > >> > >>> > > > > > > > >
> >> > > > >> > >>> > > > > > > > > Jun
> >> > > > >> > >>> > > > > > > > >
> >> > > > >> > >>> > > > > > > > > On Thu, Apr 16, 2020 at 11:14 AM Kowshik
> >> > > Prakasam
> >> > > > <
> >> > > > >> > >>> > > > > > > > kprakasam@confluent.io>
> >> > > > >> > >>> > > > > > > > > wrote:
> >> > > > >> > >>> > > > > > > > >
> >> > > > >> > >>> > > > > > > > > > Hi all,
> >> > > > >> > >>> > > > > > > > > >
> >> > > > >> > >>> > > > > > > > > > I'd like to start a vote for KIP-584
> >> > > > >> > >>> <https://issues.apache.org/jira/browse/KIP-584>
> >> > > > >> > >>> > > > > <https://issues.apache.org/jira/browse/KIP-584>.
> >> The
> >> > > link
> >> > > > >> to
> >> > > > >> > >>> the KIP
> >> > > > >> > >>> > > can
> >> > > > >> > >>> > > > > be
> >> > > > >> > >>> > > > > > > found
> >> > > > >> > >>> > > > > > > > > > here:
> >> > > > >> > >>> > > > > > > > > >
> >> > > > >> > >>> > > > > > > > > >
> >> > > > >> > >>> > > > > > > > >
> >> > > > >> > >>> > > > > > > >
> >> > > > >> > >>> > > > > > >
> >> > > > >> > >>> > > > >
> >> > > > >> > >>> > >
> >> > > > >> > >>>
> >> > > > >>
> >> > > >
> >> > >
> >> >
> >>
> https://cwiki.apache.org/confluence/display/KAFKA/KIP-584%3A+Versioning+scheme+for+features
> >> > > > >> > >>> > > > > > > > > > .
> >> > > > >> > >>> > > > > > > > > >
> >> > > > >> > >>> > > > > > > > > > Thanks!
> >> > > > >> > >>> > > > > > > > > >
> >> > > > >> > >>> > > > > > > > > >
> >> > > > >> > >>> > > > > > > > > > Cheers,
> >> > > > >> > >>> > > > > > > > > > Kowshik
> >> > > > >> > >>> > > > > > > > > >
> >> > > > >> > >>> > > > > > > > >
> >> > > > >> > >>> > > > > > > >
> >> > > > >> > >>> > > > > > > >
> >> > > > >> > >>> > > > > > > > --
> >> > > > >> > >>> > > > > > > > -- Guozhang
> >> > > > >> > >>> > > > > > > >
> >> > > > >> > >>> > > > > > >
> >> > > > >> > >>> > > > > >
> >> > > > >> > >>> > > > >
> >> > > > >> > >>> > > >
> >> > > > >> > >>> > >
> >> > > > >> > >>> >
> >> > > > >> > >>>
> >> > > > >> > >>
> >> > > > >> >
> >> > > > >>
> >> > > > >
> >> > > >
> >> > >
> >> >
> >>
> >
>
Re: [VOTE] KIP-584: Versioning scheme for features
Posted by Kowshik Prakasam <kp...@confluent.io>.
Hi all,
I wanted to let you know that I have made the following minor changes to
the `kafka-features` CLI tool description in the KIP-584 write up. The
purpose is to ensure the design is correct for a few things which came up
during implementation:
1. The CLI tool now produces a tab-formatted output instead of JSON. This
aligns with the type of format produced by other admin CLI tools of Kafka,
ex: `kafka-topics`.
2. Whenever feature updates are performed, the output of the CLI tool shows
the result of each feature update that was applied.
3. The CLI tool accepts an optional argument `--dry-run` which lets the
user preview the feature updates before applying them.
The following section of the KIP has been updated with the above changes:
https://cwiki.apache.org/confluence/display/KAFKA/KIP-584%3A+Versioning+scheme+for+features#KIP584:Versioningschemeforfeatures-Toolingsupport
Please let me know if you have any questions.
Cheers,
Kowshik
On Thu, Oct 8, 2020 at 1:12 AM Kowshik Prakasam <kp...@confluent.io>
wrote:
> Hi Jun,
>
> This is a very good point. I have updated the feature version deprecation
> section mentioning the same:
> https://cwiki.apache.org/confluence/display/KAFKA/KIP-584%3A+Versioning+scheme+for+features#KIP584:Versioningschemeforfeatures-Featureversiondeprecation
> .
>
> Thank you for the suggestion.
>
>
> Cheers,
> Kowshik
>
>
> On Tue, Oct 6, 2020 at 5:30 PM Jun Rao <ju...@confluent.io> wrote:
>
>> Hi, Kowshik,
>>
>> Thanks for the follow up. Both look good to me.
>>
>> For 2, it would be useful to also add that an admin should make sure that
>> no clients are using a deprecated feature version (e.g. using the client
>> version metric) before deploying a release that deprecates it.
>>
>> Thanks,
>>
>> Jun
>>
>> On Tue, Oct 6, 2020 at 3:46 PM Kowshik Prakasam <kp...@confluent.io>
>> wrote:
>>
>> > Hi Jun,
>> >
>> > I have added the following details in the KIP-584 write up:
>> >
>> > 1. Deployment, IBP deprecation and avoidance of double rolls. This
>> section
>> > talks about the various phases of work that would be required to use
>> this
>> > KIP to eventually avoid Broker double rolls in the cluster (whenever IBP
>> > values are advanced). Link to section:
>> >
>> >
>> https://cwiki.apache.org/confluence/display/KAFKA/KIP-584%3A+Versioning+scheme+for+features#KIP584:Versioningschemeforfeatures-Deployment,IBPdeprecationandavoidanceofdoublerolls
>> > .
>> >
>> > 2. Feature version deprecation. This section explains the idea for
>> feature
>> > version deprecation (using highest supported feature min version) which
>> you
>> > had proposed during code review:
>> >
>> >
>> https://cwiki.apache.org/confluence/display/KAFKA/KIP-584%3A+Versioning+scheme+for+features#KIP584:Versioningschemeforfeatures-Featureversiondeprecation
>> > .
>> >
>> > Please let me know if you have any questions.
>> >
>> >
>> > Cheers,
>> > Kowshik
>> >
>> >
>> > On Tue, Sep 29, 2020 at 11:07 AM Jun Rao <ju...@confluent.io> wrote:
>> >
>> > > Hi, Kowshik,
>> > >
>> > > Thanks for the update. Regarding enabling a single rolling restart in
>> the
>> > > future, could we sketch out a bit how this will work by treating IBP
>> as a
>> > > feature? For example, IBP currently uses the release version and this
>> KIP
>> > > uses an integer for versions. How do we bridge the gap between the
>> two?
>> > > Does min.version still make sense for IBP as a feature?
>> > >
>> > > Thanks,
>> > >
>> > > Jun
>> > >
>> > > On Fri, Sep 25, 2020 at 5:57 PM Kowshik Prakasam <
>> kprakasam@confluent.io
>> > >
>> > > wrote:
>> > >
>> > > > Hi Colin,
>> > > >
>> > > > Thanks for the feedback. Those are very good points. I have made the
>> > > > following changes to the KIP as you had suggested:
>> > > > 1. Included the `timeoutMs` field in the `UpdateFeaturesRequest`
>> > schema.
>> > > > The initial implementation won't be making use of the field, but we
>> can
>> > > > always use it in the future as the need arises.
>> > > > 2. Modified the `FinalizedFeaturesEpoch` field in
>> `ApiVersionsResponse`
>> > > to
>> > > > use int64. This is to avoid overflow problems in the future once ZK
>> is
>> > > > gone.
>> > > >
>> > > > I have also incorporated these changes into the versioning write
>> path
>> > PR
>> > > > that is currently under review:
>> > > https://github.com/apache/kafka/pull/9001.
>> > > >
>> > > >
>> > > > Cheers,
>> > > > Kowshik
>> > > >
>> > > >
>> > > >
>> > > > On Fri, Sep 25, 2020 at 4:57 PM Kowshik Prakasam <
>> > kprakasam@confluent.io
>> > > >
>> > > > wrote:
>> > > >
>> > > > > Hi Jun,
>> > > > >
>> > > > > Thanks for the feedback. It's a very good point. I have now
>> modified
>> > > the
>> > > > > KIP-584 write-up "goals" section a bit. It now mentions one of the
>> > > goals
>> > > > as
>> > > > > enabling rolling upgrades using a single restart (instead of 2).
>> > Also I
>> > > > > have removed the text explicitly aiming for deprecation of IBP.
>> Note
>> > > that
>> > > > > previously under "Potential features in Kafka" the IBP was
>> mentioned
>> > > > under
>> > > > > point (4) as a possible coarse-grained feature. Hopefully, now
>> the 2
>> > > > > sections of the KIP align with each other well.
>> > > > >
>> > > > >
>> > > > > Cheers,
>> > > > > Kowshik
>> > > > >
>> > > > >
>> > > > > On Fri, Sep 25, 2020 at 2:03 PM Colin McCabe <cm...@apache.org>
>> > > wrote:
>> > > > >
>> > > > >> On Tue, Sep 22, 2020, at 00:43, Kowshik Prakasam wrote:
>> > > > >> > Hi all,
>> > > > >> >
>> > > > >> > I wanted to let you know that I have made the following
>> changes to
>> > > the
>> > > > >> > KIP-584 write up. The purpose is to ensure the design is
>> correct
>> > > for a
>> > > > >> few
>> > > > >> > things which came up during implementation:
>> > > > >> >
>> > > > >>
>> > > > >> Hi Kowshik,
>> > > > >>
>> > > > >> Thanks for the updates.
>> > > > >>
>> > > > >> >
>> > > > >> > 1. Per FeatureUpdate error code: The UPDATE_FEATURES controller
>> > API
>> > > is
>> > > > >> no
>> > > > >> > longer transactional. Going forward, we allow for individual
>> > > > >> FeatureUpdate
>> > > > >> > to succeed/fail in the request. As a result, the response
>> schema
>> > now
>> > > > >> > contains an error code per FeatureUpdate as well as a top-level
>> > > error
>> > > > >> code.
>> > > > >> > Overall this is a better design because it better represents
>> the
>> > > > nature
>> > > > >> of
>> > > > >> > the API: each FeatureUpdate in the request is independent of
>> the
>> > > other
>> > > > >> > updates, and the controller can process/apply these
>> independently
>> > to
>> > > > ZK.
>> > > > >> > When an UPDATE_FEATURES request fails, this new design provides
>> > > better
>> > > > >> > clarity to the caller on which FeatureUpdate could not be
>> applied
>> > > (via
>> > > > >> the
>> > > > >> > individual error codes). In the previous design, we were
>> unable to
>> > > > >> achieve
>> > > > >> > such an increased level of clarity in communicating the error
>> > codes.
>> > > > >> >
>> > > > >>
>> > > > >> OK
>> > > > >>
>> > > > >> >
>> > > > >> > 2. Due to #1, there were some minor changes required to the
>> > proposed
>> > > > >> Admin
>> > > > >> > APIs (describeFeatures and updateFeatures). A few unnecessary
>> > public
>> > > > >> APIs
>> > > > >> > have been removed, and couple essential ones have been added.
>> The
>> > > > latest
>> > > > >> > changes now represent the latest design.
>> > > > >> >
>> > > > >> > 3. The timeoutMs field has been removed from the the
>> > UPDATE_FEATURES
>> > > > API
>> > > > >> > request, since it was not found to be required during
>> > > implementation.
>> > > > >> >
>> > > > >>
>> > > > >> Please don't get rid of timeoutMs. timeoutMs is required if you
>> > want
>> > > to
>> > > > >> implement the ability to timeout the call if the controller can't
>> > get
>> > > > to it
>> > > > >> in time. This is important for avoiding congestion collapse
>> where
>> > the
>> > > > >> controller collapses under the weight of lots of retries of the
>> same
>> > > > set of
>> > > > >> calls.
>> > > > >>
>> > > > >> We may not be able to do it in the initial implementation, but we
>> > will
>> > > > >> eventually implement this for all the controller-bound RPCs.
>> > > > >>
>> > > > >> > >
>> > > > >> > > 2. Finalized feature version epoch data type has been made
>> to be
>> > > > int32
>> > > > >> > > (instead of int64). The reason is that the epoch value is the
>> > > value
>> > > > >> of ZK
>> > > > >> > > node version, whose data type is int32.
>> > > > >> > >
>> > > > >>
>> > > > >> Sorry, I missed this earlier. Using 16 bit feature levels seems
>> > fine.
>> > > > >> However, please don't use a 32-bit epoch here. We deliberately
>> made
>> > > the
>> > > > >> epoch 64 bits to avoid overflow problems in the future once ZK is
>> > > gone.
>> > > > >>
>> > > > >> best,
>> > > > >> Colin
>> > > > >>
>> > > > >> > > 3. Introduced a new 'status' field in the '/features' ZK node
>> > > > schema.
>> > > > >> The
>> > > > >> > > purpose is to implement Colin's earlier point for the
>> strategy
>> > for
>> > > > >> > > transitioning from not having a /features znode to having
>> one.
>> > An
>> > > > >> > > explanation has been provided in the following section of the
>> > KIP
>> > > > >> detailing
>> > > > >> > > the different cases:
>> > > > >> > >
>> > > > >>
>> > > >
>> > >
>> >
>> https://cwiki.apache.org/confluence/display/KAFKA/KIP-584%3A+Versioning+scheme+for+features#KIP584:Versioningschemeforfeatures-FeatureZKnodestatus
>> > > > >> > > .
>> > > > >> > >
>> > > > >> > > Please let me know if you have any questions or concerns.
>> > > > >> > >
>> > > > >> > >
>> > > > >> > > Cheers,
>> > > > >> > > Kowshik
>> > > > >> > >
>> > > > >> > >
>> > > > >> > >
>> > > > >> > > Cheers,
>> > > > >> > > Kowshik
>> > > > >> > >
>> > > > >> > > On Tue, Apr 28, 2020 at 11:24 PM Kowshik Prakasam <
>> > > > >> kprakasam@confluent.io>
>> > > > >> > > wrote:
>> > > > >> > >
>> > > > >> > >> Hi all,
>> > > > >> > >>
>> > > > >> > >> This KIP vote has been open for ~12 days. The summary of the
>> > > votes
>> > > > is
>> > > > >> > >> that we have 3 binding votes (Colin, Guozhang, Jun), and 3
>> > > > >> non-binding
>> > > > >> > >> votes (David, Dhruvil, Boyang). Therefore, the KIP vote
>> passes.
>> > > > I'll
>> > > > >> mark
>> > > > >> > >> KIP as accepted and start working on the implementation.
>> > > > >> > >>
>> > > > >> > >> Thanks a lot!
>> > > > >> > >>
>> > > > >> > >>
>> > > > >> > >> Cheers,
>> > > > >> > >> Kowshik
>> > > > >> > >>
>> > > > >> > >> On Mon, Apr 27, 2020 at 12:15 PM Colin McCabe <
>> > > cmccabe@apache.org>
>> > > > >> wrote:
>> > > > >> > >>
>> > > > >> > >>> Thanks, Kowshik. +1 (binding)
>> > > > >> > >>>
>> > > > >> > >>> best,
>> > > > >> > >>> Colin
>> > > > >> > >>>
>> > > > >> > >>> On Sat, Apr 25, 2020, at 13:20, Kowshik Prakasam wrote:
>> > > > >> > >>> > Hi Colin,
>> > > > >> > >>> >
>> > > > >> > >>> > Thanks for the explanation! I agree with you, and I have
>> > > updated
>> > > > >> the
>> > > > >> > >>> > KIP.
>> > > > >> > >>> > Here is a link to relevant section:
>> > > > >> > >>> >
>> > > > >> > >>>
>> > > > >>
>> > > >
>> > >
>> >
>> https://cwiki.apache.org/confluence/display/KAFKA/KIP-584%3A+Versioning+scheme+for+features#KIP-584:Versioningschemeforfeatures-Controller:ZKnodebootstrapwithdefaultvalues
>> > > > >> > >>> >
>> > > > >> > >>> >
>> > > > >> > >>> > Cheers,
>> > > > >> > >>> > Kowshik
>> > > > >> > >>> >
>> > > > >> > >>> > On Fri, Apr 24, 2020 at 8:50 PM Colin McCabe <
>> > > > cmccabe@apache.org>
>> > > > >> > >>> wrote:
>> > > > >> > >>> >
>> > > > >> > >>> > > On Fri, Apr 24, 2020, at 00:01, Kowshik Prakasam wrote:
>> > > > >> > >>> > > > (Kowshik): Great point! However for case #1, I'm not
>> > sure
>> > > > why
>> > > > >> we
>> > > > >> > >>> need to
>> > > > >> > >>> > > > create a '/features' ZK node with disabled features.
>> > > > Instead,
>> > > > >> do
>> > > > >> > >>> you see
>> > > > >> > >>> > > > any drawback if we just do not create it? i.e. if
>> IBP is
>> > > > less
>> > > > >> than
>> > > > >> > >>> 2.6,
>> > > > >> > >>> > > the
>> > > > >> > >>> > > > controller treats the case as though the versioning
>> > system
>> > > > is
>> > > > >> > >>> completely
>> > > > >> > >>> > > > disabled, and would not create a non-existing
>> > '/features'
>> > > > >> node.
>> > > > >> > >>> > >
>> > > > >> > >>> > > Hi Kowshik,
>> > > > >> > >>> > >
>> > > > >> > >>> > > When the IBP is less than 2.6, but the software has
>> been
>> > > > >> upgraded to
>> > > > >> > >>> a
>> > > > >> > >>> > > state where it supports this KIP, that
>> > > > >> > >>> > > means the user is upgrading from an earlier version of
>> > the
>> > > > >> > >>> software. In
>> > > > >> > >>> > > this case, we want to start with all the features
>> disabled
>> > > and
>> > > > >> allow
>> > > > >> > >>> the
>> > > > >> > >>> > > user to enable them when they are ready.
>> > > > >> > >>> > >
>> > > > >> > >>> > > Enabling all the possible features immediately after an
>> > > > upgrade
>> > > > >> > >>> could be
>> > > > >> > >>> > > harmful to the cluster. On the other hand, for a new
>> > > cluster,
>> > > > >> we do
>> > > > >> > >>> want
>> > > > >> > >>> > > to enable all the possible features immediately . I was
>> > > > >> proposing
>> > > > >> > >>> this as a
>> > > > >> > >>> > > way to distinguish the two cases (since the new cluster
>> > will
>> > > > >> never be
>> > > > >> > >>> > > started with an old IBP).
>> > > > >> > >>> > >
>> > > > >> > >>> > > > Colin MccCabe wrote:
>> > > > >> > >>> > > > > And now, something a little bit bigger (sorry).
>> For
>> > > > >> finalized
>> > > > >> > >>> > > features,
>> > > > >> > >>> > > > > why do we need both min_version_level and
>> > > > max_version_level?
>> > > > >> > >>> Assuming
>> > > > >> > >>> > > that
>> > > > >> > >>> > > > > we want all the brokers to be on the same feature
>> > > version
>> > > > >> level,
>> > > > >> > >>> we
>> > > > >> > >>> > > really only care
>> > > > >> > >>> > > > > about three numbers for each feature, right? The
>> > > minimum
>> > > > >> > >>> supported
>> > > > >> > >>> > > version
>> > > > >> > >>> > > > > level, the maximum supported version level, and the
>> > > > current
>> > > > >> > >>> active
>> > > > >> > >>> > > version level.
>> > > > >> > >>> > > >
>> > > > >> > >>> > > > > We don't actually want different brokers to be on
>> > > > different
>> > > > >> > >>> versions of
>> > > > >> > >>> > > > > the same feature, right? So we can just have one
>> > number
>> > > > for
>> > > > >> > >>> current
>> > > > >> > >>> > > > > version level, rather than two. At least that's
>> what
>> > I
>> > > > was
>> > > > >> > >>> thinking
>> > > > >> > >>> > > -- let
>> > > > >> > >>> > > > > me know if I missed something.
>> > > > >> > >>> > > >
>> > > > >> > >>> > > > (Kowshik): It is my understanding that the "current
>> > active
>> > > > >> version
>> > > > >> > >>> level"
>> > > > >> > >>> > > > that you have mentioned, is the "max_version_level".
>> But
>> > > we
>> > > > >> still
>> > > > >> > >>> > > > maintain/publish both min and max version levels,
>> > because,
>> > > > the
>> > > > >> > >>> detail
>> > > > >> > >>> > > about
>> > > > >> > >>> > > > min level is useful to external clients. This is
>> > described
>> > > > >> below.
>> > > > >> > >>> > > >
>> > > > >> > >>> > > > For any feature F, think of the closed range:
>> > > > >> [min_version_level,
>> > > > >> > >>> > > > max_version_level] as the range of finalized
>> versions,
>> > > > that's
>> > > > >> > >>> guaranteed
>> > > > >> > >>> > > to
>> > > > >> > >>> > > > be supported by all brokers in the cluster.
>> > > > >> > >>> > > > - "max_version_level" is the finalized highest
>> common
>> > > > version
>> > > > >> > >>> among all
>> > > > >> > >>> > > > brokers,
>> > > > >> > >>> > > > - "min_version_level" is the finalized lowest common
>> > > > version
>> > > > >> > >>> among all
>> > > > >> > >>> > > > brokers.
>> > > > >> > >>> > > >
>> > > > >> > >>> > > > Next, think of "client" here as the "user of the new
>> > > feature
>> > > > >> > >>> versions
>> > > > >> > >>> > > > system". Imagine that such a client learns about
>> > finalized
>> > > > >> feature
>> > > > >> > >>> > > > versions, and exercises some logic based on the
>> version.
>> > > > These
>> > > > >> > >>> clients
>> > > > >> > >>> > > can
>> > > > >> > >>> > > > be of 2 types:
>> > > > >> > >>> > > > 1. Some part of the broker code itself could behave
>> > like a
>> > > > >> client
>> > > > >> > >>> trying
>> > > > >> > >>> > > to
>> > > > >> > >>> > > > use some feature that's "internal" to the broker
>> > cluster.
>> > > > >> Such a
>> > > > >> > >>> client
>> > > > >> > >>> > > > would learn the latest finalized features via ZK.
>> > > > >> > >>> > > > 2. An external system (ex: Streams) could behave
>> like a
>> > > > >> client,
>> > > > >> > >>> trying to
>> > > > >> > >>> > > > use some "external" facing feature. Such a client
>> would
>> > > > learn
>> > > > >> > >>> latest
>> > > > >> > >>> > > > finalized features via ApiVersionsRequest. Ex:
>> > > > >> group_coordinator
>> > > > >> > >>> feature
>> > > > >> > >>> > > > described in the KIP.
>> > > > >> > >>> > > >
>> > > > >> > >>> > > > Next, imagine that for F, the max_version_level is
>> > > > >> successfully
>> > > > >> > >>> bumped by
>> > > > >> > >>> > > > +1 (via Controller API). Now it is guaranteed that
>> all
>> > > > brokers
>> > > > >> > >>> (i.e.
>> > > > >> > >>> > > > internal clients) understand max_version_level + 1.
>> > > However,
>> > > > >> it is
>> > > > >> > >>> still
>> > > > >> > >>> > > > not guaranteed that all external clients have support
>> > for
>> > > > (or
>> > > > >> have
>> > > > >> > >>> > > > activated) the logic for the newer version. Why?
>> > Because,
>> > > > >> this is
>> > > > >> > >>> > > > subjective as explained next:
>> > > > >> > >>> > > >
>> > > > >> > >>> > > > 1. On one hand, imagine F as an internal feature only
>> > > > >> relevant to
>> > > > >> > >>> > > Brokers.
>> > > > >> > >>> > > > The binary for the internal client logic is
>> controlled
>> > by
>> > > > >> Broker
>> > > > >> > >>> cluster
>> > > > >> > >>> > > > deployments. When shipping a new Broker release, we
>> > > wouldn't
>> > > > >> bump
>> > > > >> > >>> max
>> > > > >> > >>> > > > "supported" feature version for F by 1, unless we
>> have
>> > > > >> introduced
>> > > > >> > >>> some
>> > > > >> > >>> > > new
>> > > > >> > >>> > > > logic (with a potentially breaking change) in the
>> > Broker.
>> > > > >> > >>> Furthermore,
>> > > > >> > >>> > > such
>> > > > >> > >>> > > > feature logic in the broker should/will not be
>> > implemented
>> > > > in
>> > > > >> a
>> > > > >> > >>> way that
>> > > > >> > >>> > > it
>> > > > >> > >>> > > > would activate logic for an older feature version
>> after
>> > it
>> > > > has
>> > > > >> > >>> migrated
>> > > > >> > >>> > > to
>> > > > >> > >>> > > > using the logic for a newer feature version (because
>> > this
>> > > > >> could
>> > > > >> > >>> break the
>> > > > >> > >>> > > > cluster!). For these cases, max_version_level will be
>> > very
>> > > > >> useful
>> > > > >> > >>> for
>> > > > >> > >>> > > > decision making.
>> > > > >> > >>> > > >
>> > > > >> > >>> > > > 2. On the other hand, imagine F as an external facing
>> > > > feature.
>> > > > >> > >>> External
>> > > > >> > >>> > > > clients are not within the control of Broker
>> cluster. An
>> > > > >> external
>> > > > >> > >>> client
>> > > > >> > >>> > > > may not have upgraded it's code (yet) to use
>> > > > >> 'max_version_level +
>> > > > >> > >>> 1'.
>> > > > >> > >>> > > But,
>> > > > >> > >>> > > > the Kafka cluster could have been deployed with
>> support
>> > > for
>> > > > >> > >>> > > > 'max_version_level + 1' of an external facing
>> feature.
>> > > Now,
>> > > > >> these
>> > > > >> > >>> > > external
>> > > > >> > >>> > > > clients (until an upgrade) are benefitted in learning
>> > > "what
>> > > > >> is the
>> > > > >> > >>> lowest
>> > > > >> > >>> > > > common version for F among all brokers?". This is
>> where
>> > > the
>> > > > >> > >>> > > > "min_version_level" becomes useful. Using this, a
>> client
>> > > > could
>> > > > >> > >>> learn the
>> > > > >> > >>> > > > specific supported versions that's lower than
>> > > > >> max_version_level
>> > > > >> > >>> (instead
>> > > > >> > >>> > > of
>> > > > >> > >>> > > > assuming that all brokers support the range: [1,
>> > > > >> > >>> max_version_level]). For
>> > > > >> > >>> > > > example, if the cluster deprecates
>> "min_version_level",
>> > > then
>> > > > >> the
>> > > > >> > >>> client
>> > > > >> > >>> > > > becomes aware because it periodically learns the
>> latest
>> > > > >> > >>> > > "min_version_level"
>> > > > >> > >>> > > > via ApiVersionsRequest.
>> > > > >> > >>> > > >
>> > > > >> > >>> > >
>> > > > >> > >>> > > Thanks for the explanation. I agree that this does
>> make
>> > > sense
>> > > > >> when
>> > > > >> > >>> you
>> > > > >> > >>> > > take the client perspective into account.
>> > > > >> > >>> > >
>> > > > >> > >>> > > best,
>> > > > >> > >>> > > Colin
>> > > > >> > >>> > >
>> > > > >> > >>> > >
>> > > > >> > >>> > > >
>> > > > >> > >>> > > > Cheers,
>> > > > >> > >>> > > > Kowshik
>> > > > >> > >>> > > >
>> > > > >> > >>> > > >
>> > > > >> > >>> > > >
>> > > > >> > >>> > > >
>> > > > >> > >>> > > > On Thu, Apr 23, 2020 at 12:07 PM Colin McCabe <
>> > > > >> cmccabe@apache.org>
>> > > > >> > >>> > > wrote:
>> > > > >> > >>> > > >
>> > > > >> > >>> > > > > Hi Kowshik,
>> > > > >> > >>> > > > >
>> > > > >> > >>> > > > > Thanks again for working on this-- it looks
>> great. I
>> > > went
>> > > > >> over
>> > > > >> > >>> the KIP
>> > > > >> > >>> > > > > again and have a few more comments.
>> > > > >> > >>> > > > >
>> > > > >> > >>> > > > > ===
>> > > > >> > >>> > > > >
>> > > > >> > >>> > > > > It would be good to note that deprecating a feature
>> > > > version
>> > > > >> (in
>> > > > >> > >>> other
>> > > > >> > >>> > > > > words, increasing minVersionLevel on the broker)
>> is an
>> > > > >> > >>> incompatible
>> > > > >> > >>> > > change,
>> > > > >> > >>> > > > > which requires a major release of Kafka.
>> > > > >> > >>> > > > >
>> > > > >> > >>> > > > > ===
>> > > > >> > >>> > > > >
>> > > > >> > >>> > > > > I think the strategy for transitioning from not
>> > having a
>> > > > >> > >>> /features
>> > > > >> > >>> > > znode
>> > > > >> > >>> > > > > to having one could use some work. The current
>> > proposal
>> > > is
>> > > > >> to
>> > > > >> > >>> wait for
>> > > > >> > >>> > > all
>> > > > >> > >>> > > > > the brokers to fill in their feature znodes and
>> then
>> > > pick
>> > > > >> the
>> > > > >> > >>> highest
>> > > > >> > >>> > > > > common versions. But that requires blocking in the
>> > > > >> controller
>> > > > >> > >>> startup
>> > > > >> > >>> > > code
>> > > > >> > >>> > > > > until the whole cluster is active (technically, a
>> > point
>> > > in
>> > > > >> time
>> > > > >> > >>> which
>> > > > >> > >>> > > we
>> > > > >> > >>> > > > > never really know that we have reached...)
>> > > > >> > >>> > > > >
>> > > > >> > >>> > > > > Instead, I think it would be better to have a
>> strategy
>> > > > like
>> > > > >> this:
>> > > > >> > >>> > > > > 1. If the controller comes up and there is no
>> > /features
>> > > > >> znode
>> > > > >> > >>> AND the
>> > > > >> > >>> > > IBP
>> > > > >> > >>> > > > > is less than 2.6, create a /features znode where
>> all
>> > the
>> > > > >> > >>> features are
>> > > > >> > >>> > > > > disabled.
>> > > > >> > >>> > > > > 2. If the controller comes up and there is no
>> > /features
>> > > > >> znode
>> > > > >> > >>> AND the
>> > > > >> > >>> > > IBP
>> > > > >> > >>> > > > > is greater than or equal to 2.6, create a /features
>> > > znode
>> > > > >> where
>> > > > >> > >>> all the
>> > > > >> > >>> > > > > features are enabled at the highest versions
>> supported
>> > > by
>> > > > >> the
>> > > > >> > >>> > > controller.
>> > > > >> > >>> > > > >
>> > > > >> > >>> > > > > People upgrading from the pre-KIP-584
>> > > > >> > >>> <https://issues.apache.org/jira/browse/KIP-584>
>> > > > >> > >>> > > > > <https://issues.apache.org/jira/browse/KIP-584>
>> world
>> > > > will
>> > > > >> end
>> > > > >> > >>> up in
>> > > > >> > >>> > > case
>> > > > >> > >>> > > > > #1 because they have to do a double roll to
>> upgrade,
>> > and
>> > > > >> during
>> > > > >> > >>> the
>> > > > >> > >>> > > first
>> > > > >> > >>> > > > > roll, the IBP is unchanged. People creating new
>> > > clusters
>> > > > >> from
>> > > > >> > >>> scratch
>> > > > >> > >>> > > will
>> > > > >> > >>> > > > > end up in case #2, which is what we want since we
>> > don't
>> > > > >> want a
>> > > > >> > >>> brand
>> > > > >> > >>> > > new
>> > > > >> > >>> > > > > cluster to be using old feature flag versions.
>> > > > >> > >>> > > > >
>> > > > >> > >>> > > > > ===
>> > > > >> > >>> > > > >
>> > > > >> > >>> > > > > UpdateFeaturesResponse#ErrorMessage should specify
>> > > > >> > >>> nullableVersions
>> > > > >> > >>> > > since
>> > > > >> > >>> > > > > null is a valid value here
>> > > > >> > >>> > > > >
>> > > > >> > >>> > > > > Also, in the message format, the tags we use need
>> to
>> > > start
>> > > > >> at 0.
>> > > > >> > >>> > > > >
>> > > > >> > >>> > > > > ===
>> > > > >> > >>> > > > >
>> > > > >> > >>> > > > > I don't think we need the
>> FEATURE_UPDATE_IN_PROGRESS
>> > > error
>> > > > >> > >>> code. The
>> > > > >> > >>> > > > > controller is basically single-threaded and will
>> only
>> > do
>> > > > >> one of
>> > > > >> > >>> these
>> > > > >> > >>> > > > > operations at once. Even if it weren't, though, we
>> > > could
>> > > > >> simply
>> > > > >> > >>> block
>> > > > >> > >>> > > the
>> > > > >> > >>> > > > > second operation behind the first one.
>> > > > >> > >>> > > > >
>> > > > >> > >>> > > > > ===
>> > > > >> > >>> > > > >
>> > > > >> > >>> > > > > For updateFeatures, it would be good to specify
>> that
>> > if
>> > > a
>> > > > >> single
>> > > > >> > >>> > > feature
>> > > > >> > >>> > > > > version update in the batch can't be done, none of
>> > them
>> > > > are
>> > > > >> > >>> done. I
>> > > > >> > >>> > > think
>> > > > >> > >>> > > > > this was the intention, but I wasn't able to find
>> it
>> > > > >> spelled out
>> > > > >> > >>> > > (maybe i
>> > > > >> > >>> > > > > missed it).
>> > > > >> > >>> > > > >
>> > > > >> > >>> > > > > ===
>> > > > >> > >>> > > > >
>> > > > >> > >>> > > > > And now, something a little bit bigger (sorry).
>> For
>> > > > >> finalized
>> > > > >> > >>> > > features,
>> > > > >> > >>> > > > > why do we need both min_version_level and
>> > > > max_version_level?
>> > > > >> > >>> Assuming
>> > > > >> > >>> > > that
>> > > > >> > >>> > > > > we want all the brokers to be on the same feature
>> > > version
>> > > > >> level,
>> > > > >> > >>> we
>> > > > >> > >>> > > really
>> > > > >> > >>> > > > > only care about three numbers for each feature,
>> right?
>> > > > The
>> > > > >> > >>> minimum
>> > > > >> > >>> > > > > supported version level, the maximum supported
>> version
>> > > > >> level,
>> > > > >> > >>> and the
>> > > > >> > >>> > > > > current active version level.
>> > > > >> > >>> > > > >
>> > > > >> > >>> > > > > We don't actually want different brokers to be on
>> > > > different
>> > > > >> > >>> versions of
>> > > > >> > >>> > > > > the same feature, right? So we can just have one
>> > number
>> > > > for
>> > > > >> > >>> current
>> > > > >> > >>> > > > > version level, rather than two. At least that's
>> what
>> > I
>> > > > was
>> > > > >> > >>> thinking
>> > > > >> > >>> > > -- let
>> > > > >> > >>> > > > > me know if I missed something.
>> > > > >> > >>> > > > >
>> > > > >> > >>> > > > > best,
>> > > > >> > >>> > > > > Colin
>> > > > >> > >>> > > > >
>> > > > >> > >>> > > > >
>> > > > >> > >>> > > > > On Tue, Apr 21, 2020, at 13:01, Dhruvil Shah wrote:
>> > > > >> > >>> > > > > > Thanks for the KIP! +1 (non-binding)
>> > > > >> > >>> > > > > >
>> > > > >> > >>> > > > > > On Tue, Apr 21, 2020 at 6:09 AM David Jacot <
>> > > > >> > >>> djacot@confluent.io>
>> > > > >> > >>> > > wrote:
>> > > > >> > >>> > > > > >
>> > > > >> > >>> > > > > > > Great KIP, thanks! +1 (non-binding)
>> > > > >> > >>> > > > > > >
>> > > > >> > >>> > > > > > > On Fri, Apr 17, 2020 at 8:56 PM Guozhang Wang <
>> > > > >> > >>> wangguoz@gmail.com>
>> > > > >> > >>> > > > > wrote:
>> > > > >> > >>> > > > > > >
>> > > > >> > >>> > > > > > > > Thanks for the great KIP Kowshik, +1
>> (binding).
>> > > > >> > >>> > > > > > > >
>> > > > >> > >>> > > > > > > > On Fri, Apr 17, 2020 at 11:22 AM Jun Rao <
>> > > > >> jun@confluent.io
>> > > > >> > >>> >
>> > > > >> > >>> > > wrote:
>> > > > >> > >>> > > > > > > >
>> > > > >> > >>> > > > > > > > > Hi, Kowshik,
>> > > > >> > >>> > > > > > > > >
>> > > > >> > >>> > > > > > > > > Thanks for the KIP. +1
>> > > > >> > >>> > > > > > > > >
>> > > > >> > >>> > > > > > > > > Jun
>> > > > >> > >>> > > > > > > > >
>> > > > >> > >>> > > > > > > > > On Thu, Apr 16, 2020 at 11:14 AM Kowshik
>> > > Prakasam
>> > > > <
>> > > > >> > >>> > > > > > > > kprakasam@confluent.io>
>> > > > >> > >>> > > > > > > > > wrote:
>> > > > >> > >>> > > > > > > > >
>> > > > >> > >>> > > > > > > > > > Hi all,
>> > > > >> > >>> > > > > > > > > >
>> > > > >> > >>> > > > > > > > > > I'd like to start a vote for KIP-584
>> > > > >> > >>> <https://issues.apache.org/jira/browse/KIP-584>
>> > > > >> > >>> > > > > <https://issues.apache.org/jira/browse/KIP-584>.
>> The
>> > > link
>> > > > >> to
>> > > > >> > >>> the KIP
>> > > > >> > >>> > > can
>> > > > >> > >>> > > > > be
>> > > > >> > >>> > > > > > > found
>> > > > >> > >>> > > > > > > > > > here:
>> > > > >> > >>> > > > > > > > > >
>> > > > >> > >>> > > > > > > > > >
>> > > > >> > >>> > > > > > > > >
>> > > > >> > >>> > > > > > > >
>> > > > >> > >>> > > > > > >
>> > > > >> > >>> > > > >
>> > > > >> > >>> > >
>> > > > >> > >>>
>> > > > >>
>> > > >
>> > >
>> >
>> https://cwiki.apache.org/confluence/display/KAFKA/KIP-584%3A+Versioning+scheme+for+features
>> > > > >> > >>> > > > > > > > > > .
>> > > > >> > >>> > > > > > > > > >
>> > > > >> > >>> > > > > > > > > > Thanks!
>> > > > >> > >>> > > > > > > > > >
>> > > > >> > >>> > > > > > > > > >
>> > > > >> > >>> > > > > > > > > > Cheers,
>> > > > >> > >>> > > > > > > > > > Kowshik
>> > > > >> > >>> > > > > > > > > >
>> > > > >> > >>> > > > > > > > >
>> > > > >> > >>> > > > > > > >
>> > > > >> > >>> > > > > > > >
>> > > > >> > >>> > > > > > > > --
>> > > > >> > >>> > > > > > > > -- Guozhang
>> > > > >> > >>> > > > > > > >
>> > > > >> > >>> > > > > > >
>> > > > >> > >>> > > > > >
>> > > > >> > >>> > > > >
>> > > > >> > >>> > > >
>> > > > >> > >>> > >
>> > > > >> > >>> >
>> > > > >> > >>>
>> > > > >> > >>
>> > > > >> >
>> > > > >>
>> > > > >
>> > > >
>> > >
>> >
>>
>
Re: [VOTE] KIP-584: Versioning scheme for features
Posted by Kowshik Prakasam <kp...@confluent.io>.
Hi Jun,
This is a very good point. I have updated the feature version deprecation
section mentioning the same:
https://cwiki.apache.org/confluence/display/KAFKA/KIP-584%3A+Versioning+scheme+for+features#KIP584:Versioningschemeforfeatures-Featureversiondeprecation
.
Thank you for the suggestion.
Cheers,
Kowshik
On Tue, Oct 6, 2020 at 5:30 PM Jun Rao <ju...@confluent.io> wrote:
> Hi, Kowshik,
>
> Thanks for the follow up. Both look good to me.
>
> For 2, it would be useful to also add that an admin should make sure that
> no clients are using a deprecated feature version (e.g. using the client
> version metric) before deploying a release that deprecates it.
>
> Thanks,
>
> Jun
>
> On Tue, Oct 6, 2020 at 3:46 PM Kowshik Prakasam <kp...@confluent.io>
> wrote:
>
> > Hi Jun,
> >
> > I have added the following details in the KIP-584 write up:
> >
> > 1. Deployment, IBP deprecation and avoidance of double rolls. This
> section
> > talks about the various phases of work that would be required to use this
> > KIP to eventually avoid Broker double rolls in the cluster (whenever IBP
> > values are advanced). Link to section:
> >
> >
> https://cwiki.apache.org/confluence/display/KAFKA/KIP-584%3A+Versioning+scheme+for+features#KIP584:Versioningschemeforfeatures-Deployment,IBPdeprecationandavoidanceofdoublerolls
> > .
> >
> > 2. Feature version deprecation. This section explains the idea for
> feature
> > version deprecation (using highest supported feature min version) which
> you
> > had proposed during code review:
> >
> >
> https://cwiki.apache.org/confluence/display/KAFKA/KIP-584%3A+Versioning+scheme+for+features#KIP584:Versioningschemeforfeatures-Featureversiondeprecation
> > .
> >
> > Please let me know if you have any questions.
> >
> >
> > Cheers,
> > Kowshik
> >
> >
> > On Tue, Sep 29, 2020 at 11:07 AM Jun Rao <ju...@confluent.io> wrote:
> >
> > > Hi, Kowshik,
> > >
> > > Thanks for the update. Regarding enabling a single rolling restart in
> the
> > > future, could we sketch out a bit how this will work by treating IBP
> as a
> > > feature? For example, IBP currently uses the release version and this
> KIP
> > > uses an integer for versions. How do we bridge the gap between the two?
> > > Does min.version still make sense for IBP as a feature?
> > >
> > > Thanks,
> > >
> > > Jun
> > >
> > > On Fri, Sep 25, 2020 at 5:57 PM Kowshik Prakasam <
> kprakasam@confluent.io
> > >
> > > wrote:
> > >
> > > > Hi Colin,
> > > >
> > > > Thanks for the feedback. Those are very good points. I have made the
> > > > following changes to the KIP as you had suggested:
> > > > 1. Included the `timeoutMs` field in the `UpdateFeaturesRequest`
> > schema.
> > > > The initial implementation won't be making use of the field, but we
> can
> > > > always use it in the future as the need arises.
> > > > 2. Modified the `FinalizedFeaturesEpoch` field in
> `ApiVersionsResponse`
> > > to
> > > > use int64. This is to avoid overflow problems in the future once ZK
> is
> > > > gone.
> > > >
> > > > I have also incorporated these changes into the versioning write path
> > PR
> > > > that is currently under review:
> > > https://github.com/apache/kafka/pull/9001.
> > > >
> > > >
> > > > Cheers,
> > > > Kowshik
> > > >
> > > >
> > > >
> > > > On Fri, Sep 25, 2020 at 4:57 PM Kowshik Prakasam <
> > kprakasam@confluent.io
> > > >
> > > > wrote:
> > > >
> > > > > Hi Jun,
> > > > >
> > > > > Thanks for the feedback. It's a very good point. I have now
> modified
> > > the
> > > > > KIP-584 write-up "goals" section a bit. It now mentions one of the
> > > goals
> > > > as
> > > > > enabling rolling upgrades using a single restart (instead of 2).
> > Also I
> > > > > have removed the text explicitly aiming for deprecation of IBP.
> Note
> > > that
> > > > > previously under "Potential features in Kafka" the IBP was
> mentioned
> > > > under
> > > > > point (4) as a possible coarse-grained feature. Hopefully, now the
> 2
> > > > > sections of the KIP align with each other well.
> > > > >
> > > > >
> > > > > Cheers,
> > > > > Kowshik
> > > > >
> > > > >
> > > > > On Fri, Sep 25, 2020 at 2:03 PM Colin McCabe <cm...@apache.org>
> > > wrote:
> > > > >
> > > > >> On Tue, Sep 22, 2020, at 00:43, Kowshik Prakasam wrote:
> > > > >> > Hi all,
> > > > >> >
> > > > >> > I wanted to let you know that I have made the following changes
> to
> > > the
> > > > >> > KIP-584 write up. The purpose is to ensure the design is correct
> > > for a
> > > > >> few
> > > > >> > things which came up during implementation:
> > > > >> >
> > > > >>
> > > > >> Hi Kowshik,
> > > > >>
> > > > >> Thanks for the updates.
> > > > >>
> > > > >> >
> > > > >> > 1. Per FeatureUpdate error code: The UPDATE_FEATURES controller
> > API
> > > is
> > > > >> no
> > > > >> > longer transactional. Going forward, we allow for individual
> > > > >> FeatureUpdate
> > > > >> > to succeed/fail in the request. As a result, the response schema
> > now
> > > > >> > contains an error code per FeatureUpdate as well as a top-level
> > > error
> > > > >> code.
> > > > >> > Overall this is a better design because it better represents the
> > > > nature
> > > > >> of
> > > > >> > the API: each FeatureUpdate in the request is independent of the
> > > other
> > > > >> > updates, and the controller can process/apply these
> independently
> > to
> > > > ZK.
> > > > >> > When an UPDATE_FEATURES request fails, this new design provides
> > > better
> > > > >> > clarity to the caller on which FeatureUpdate could not be
> applied
> > > (via
> > > > >> the
> > > > >> > individual error codes). In the previous design, we were unable
> to
> > > > >> achieve
> > > > >> > such an increased level of clarity in communicating the error
> > codes.
> > > > >> >
> > > > >>
> > > > >> OK
> > > > >>
> > > > >> >
> > > > >> > 2. Due to #1, there were some minor changes required to the
> > proposed
> > > > >> Admin
> > > > >> > APIs (describeFeatures and updateFeatures). A few unnecessary
> > public
> > > > >> APIs
> > > > >> > have been removed, and couple essential ones have been added.
> The
> > > > latest
> > > > >> > changes now represent the latest design.
> > > > >> >
> > > > >> > 3. The timeoutMs field has been removed from the the
> > UPDATE_FEATURES
> > > > API
> > > > >> > request, since it was not found to be required during
> > > implementation.
> > > > >> >
> > > > >>
> > > > >> Please don't get rid of timeoutMs. timeoutMs is required if you
> > want
> > > to
> > > > >> implement the ability to timeout the call if the controller can't
> > get
> > > > to it
> > > > >> in time. This is important for avoiding congestion collapse where
> > the
> > > > >> controller collapses under the weight of lots of retries of the
> same
> > > > set of
> > > > >> calls.
> > > > >>
> > > > >> We may not be able to do it in the initial implementation, but we
> > will
> > > > >> eventually implement this for all the controller-bound RPCs.
> > > > >>
> > > > >> > >
> > > > >> > > 2. Finalized feature version epoch data type has been made to
> be
> > > > int32
> > > > >> > > (instead of int64). The reason is that the epoch value is the
> > > value
> > > > >> of ZK
> > > > >> > > node version, whose data type is int32.
> > > > >> > >
> > > > >>
> > > > >> Sorry, I missed this earlier. Using 16 bit feature levels seems
> > fine.
> > > > >> However, please don't use a 32-bit epoch here. We deliberately
> made
> > > the
> > > > >> epoch 64 bits to avoid overflow problems in the future once ZK is
> > > gone.
> > > > >>
> > > > >> best,
> > > > >> Colin
> > > > >>
> > > > >> > > 3. Introduced a new 'status' field in the '/features' ZK node
> > > > schema.
> > > > >> The
> > > > >> > > purpose is to implement Colin's earlier point for the strategy
> > for
> > > > >> > > transitioning from not having a /features znode to having one.
> > An
> > > > >> > > explanation has been provided in the following section of the
> > KIP
> > > > >> detailing
> > > > >> > > the different cases:
> > > > >> > >
> > > > >>
> > > >
> > >
> >
> https://cwiki.apache.org/confluence/display/KAFKA/KIP-584%3A+Versioning+scheme+for+features#KIP584:Versioningschemeforfeatures-FeatureZKnodestatus
> > > > >> > > .
> > > > >> > >
> > > > >> > > Please let me know if you have any questions or concerns.
> > > > >> > >
> > > > >> > >
> > > > >> > > Cheers,
> > > > >> > > Kowshik
> > > > >> > >
> > > > >> > >
> > > > >> > >
> > > > >> > > Cheers,
> > > > >> > > Kowshik
> > > > >> > >
> > > > >> > > On Tue, Apr 28, 2020 at 11:24 PM Kowshik Prakasam <
> > > > >> kprakasam@confluent.io>
> > > > >> > > wrote:
> > > > >> > >
> > > > >> > >> Hi all,
> > > > >> > >>
> > > > >> > >> This KIP vote has been open for ~12 days. The summary of the
> > > votes
> > > > is
> > > > >> > >> that we have 3 binding votes (Colin, Guozhang, Jun), and 3
> > > > >> non-binding
> > > > >> > >> votes (David, Dhruvil, Boyang). Therefore, the KIP vote
> passes.
> > > > I'll
> > > > >> mark
> > > > >> > >> KIP as accepted and start working on the implementation.
> > > > >> > >>
> > > > >> > >> Thanks a lot!
> > > > >> > >>
> > > > >> > >>
> > > > >> > >> Cheers,
> > > > >> > >> Kowshik
> > > > >> > >>
> > > > >> > >> On Mon, Apr 27, 2020 at 12:15 PM Colin McCabe <
> > > cmccabe@apache.org>
> > > > >> wrote:
> > > > >> > >>
> > > > >> > >>> Thanks, Kowshik. +1 (binding)
> > > > >> > >>>
> > > > >> > >>> best,
> > > > >> > >>> Colin
> > > > >> > >>>
> > > > >> > >>> On Sat, Apr 25, 2020, at 13:20, Kowshik Prakasam wrote:
> > > > >> > >>> > Hi Colin,
> > > > >> > >>> >
> > > > >> > >>> > Thanks for the explanation! I agree with you, and I have
> > > updated
> > > > >> the
> > > > >> > >>> > KIP.
> > > > >> > >>> > Here is a link to relevant section:
> > > > >> > >>> >
> > > > >> > >>>
> > > > >>
> > > >
> > >
> >
> https://cwiki.apache.org/confluence/display/KAFKA/KIP-584%3A+Versioning+scheme+for+features#KIP-584:Versioningschemeforfeatures-Controller:ZKnodebootstrapwithdefaultvalues
> > > > >> > >>> >
> > > > >> > >>> >
> > > > >> > >>> > Cheers,
> > > > >> > >>> > Kowshik
> > > > >> > >>> >
> > > > >> > >>> > On Fri, Apr 24, 2020 at 8:50 PM Colin McCabe <
> > > > cmccabe@apache.org>
> > > > >> > >>> wrote:
> > > > >> > >>> >
> > > > >> > >>> > > On Fri, Apr 24, 2020, at 00:01, Kowshik Prakasam wrote:
> > > > >> > >>> > > > (Kowshik): Great point! However for case #1, I'm not
> > sure
> > > > why
> > > > >> we
> > > > >> > >>> need to
> > > > >> > >>> > > > create a '/features' ZK node with disabled features.
> > > > Instead,
> > > > >> do
> > > > >> > >>> you see
> > > > >> > >>> > > > any drawback if we just do not create it? i.e. if IBP
> is
> > > > less
> > > > >> than
> > > > >> > >>> 2.6,
> > > > >> > >>> > > the
> > > > >> > >>> > > > controller treats the case as though the versioning
> > system
> > > > is
> > > > >> > >>> completely
> > > > >> > >>> > > > disabled, and would not create a non-existing
> > '/features'
> > > > >> node.
> > > > >> > >>> > >
> > > > >> > >>> > > Hi Kowshik,
> > > > >> > >>> > >
> > > > >> > >>> > > When the IBP is less than 2.6, but the software has been
> > > > >> upgraded to
> > > > >> > >>> a
> > > > >> > >>> > > state where it supports this KIP, that
> > > > >> > >>> > > means the user is upgrading from an earlier version of
> > the
> > > > >> > >>> software. In
> > > > >> > >>> > > this case, we want to start with all the features
> disabled
> > > and
> > > > >> allow
> > > > >> > >>> the
> > > > >> > >>> > > user to enable them when they are ready.
> > > > >> > >>> > >
> > > > >> > >>> > > Enabling all the possible features immediately after an
> > > > upgrade
> > > > >> > >>> could be
> > > > >> > >>> > > harmful to the cluster. On the other hand, for a new
> > > cluster,
> > > > >> we do
> > > > >> > >>> want
> > > > >> > >>> > > to enable all the possible features immediately . I was
> > > > >> proposing
> > > > >> > >>> this as a
> > > > >> > >>> > > way to distinguish the two cases (since the new cluster
> > will
> > > > >> never be
> > > > >> > >>> > > started with an old IBP).
> > > > >> > >>> > >
> > > > >> > >>> > > > Colin MccCabe wrote:
> > > > >> > >>> > > > > And now, something a little bit bigger (sorry). For
> > > > >> finalized
> > > > >> > >>> > > features,
> > > > >> > >>> > > > > why do we need both min_version_level and
> > > > max_version_level?
> > > > >> > >>> Assuming
> > > > >> > >>> > > that
> > > > >> > >>> > > > > we want all the brokers to be on the same feature
> > > version
> > > > >> level,
> > > > >> > >>> we
> > > > >> > >>> > > really only care
> > > > >> > >>> > > > > about three numbers for each feature, right? The
> > > minimum
> > > > >> > >>> supported
> > > > >> > >>> > > version
> > > > >> > >>> > > > > level, the maximum supported version level, and the
> > > > current
> > > > >> > >>> active
> > > > >> > >>> > > version level.
> > > > >> > >>> > > >
> > > > >> > >>> > > > > We don't actually want different brokers to be on
> > > > different
> > > > >> > >>> versions of
> > > > >> > >>> > > > > the same feature, right? So we can just have one
> > number
> > > > for
> > > > >> > >>> current
> > > > >> > >>> > > > > version level, rather than two. At least that's
> what
> > I
> > > > was
> > > > >> > >>> thinking
> > > > >> > >>> > > -- let
> > > > >> > >>> > > > > me know if I missed something.
> > > > >> > >>> > > >
> > > > >> > >>> > > > (Kowshik): It is my understanding that the "current
> > active
> > > > >> version
> > > > >> > >>> level"
> > > > >> > >>> > > > that you have mentioned, is the "max_version_level".
> But
> > > we
> > > > >> still
> > > > >> > >>> > > > maintain/publish both min and max version levels,
> > because,
> > > > the
> > > > >> > >>> detail
> > > > >> > >>> > > about
> > > > >> > >>> > > > min level is useful to external clients. This is
> > described
> > > > >> below.
> > > > >> > >>> > > >
> > > > >> > >>> > > > For any feature F, think of the closed range:
> > > > >> [min_version_level,
> > > > >> > >>> > > > max_version_level] as the range of finalized versions,
> > > > that's
> > > > >> > >>> guaranteed
> > > > >> > >>> > > to
> > > > >> > >>> > > > be supported by all brokers in the cluster.
> > > > >> > >>> > > > - "max_version_level" is the finalized highest common
> > > > version
> > > > >> > >>> among all
> > > > >> > >>> > > > brokers,
> > > > >> > >>> > > > - "min_version_level" is the finalized lowest common
> > > > version
> > > > >> > >>> among all
> > > > >> > >>> > > > brokers.
> > > > >> > >>> > > >
> > > > >> > >>> > > > Next, think of "client" here as the "user of the new
> > > feature
> > > > >> > >>> versions
> > > > >> > >>> > > > system". Imagine that such a client learns about
> > finalized
> > > > >> feature
> > > > >> > >>> > > > versions, and exercises some logic based on the
> version.
> > > > These
> > > > >> > >>> clients
> > > > >> > >>> > > can
> > > > >> > >>> > > > be of 2 types:
> > > > >> > >>> > > > 1. Some part of the broker code itself could behave
> > like a
> > > > >> client
> > > > >> > >>> trying
> > > > >> > >>> > > to
> > > > >> > >>> > > > use some feature that's "internal" to the broker
> > cluster.
> > > > >> Such a
> > > > >> > >>> client
> > > > >> > >>> > > > would learn the latest finalized features via ZK.
> > > > >> > >>> > > > 2. An external system (ex: Streams) could behave like
> a
> > > > >> client,
> > > > >> > >>> trying to
> > > > >> > >>> > > > use some "external" facing feature. Such a client
> would
> > > > learn
> > > > >> > >>> latest
> > > > >> > >>> > > > finalized features via ApiVersionsRequest. Ex:
> > > > >> group_coordinator
> > > > >> > >>> feature
> > > > >> > >>> > > > described in the KIP.
> > > > >> > >>> > > >
> > > > >> > >>> > > > Next, imagine that for F, the max_version_level is
> > > > >> successfully
> > > > >> > >>> bumped by
> > > > >> > >>> > > > +1 (via Controller API). Now it is guaranteed that all
> > > > brokers
> > > > >> > >>> (i.e.
> > > > >> > >>> > > > internal clients) understand max_version_level + 1.
> > > However,
> > > > >> it is
> > > > >> > >>> still
> > > > >> > >>> > > > not guaranteed that all external clients have support
> > for
> > > > (or
> > > > >> have
> > > > >> > >>> > > > activated) the logic for the newer version. Why?
> > Because,
> > > > >> this is
> > > > >> > >>> > > > subjective as explained next:
> > > > >> > >>> > > >
> > > > >> > >>> > > > 1. On one hand, imagine F as an internal feature only
> > > > >> relevant to
> > > > >> > >>> > > Brokers.
> > > > >> > >>> > > > The binary for the internal client logic is controlled
> > by
> > > > >> Broker
> > > > >> > >>> cluster
> > > > >> > >>> > > > deployments. When shipping a new Broker release, we
> > > wouldn't
> > > > >> bump
> > > > >> > >>> max
> > > > >> > >>> > > > "supported" feature version for F by 1, unless we have
> > > > >> introduced
> > > > >> > >>> some
> > > > >> > >>> > > new
> > > > >> > >>> > > > logic (with a potentially breaking change) in the
> > Broker.
> > > > >> > >>> Furthermore,
> > > > >> > >>> > > such
> > > > >> > >>> > > > feature logic in the broker should/will not be
> > implemented
> > > > in
> > > > >> a
> > > > >> > >>> way that
> > > > >> > >>> > > it
> > > > >> > >>> > > > would activate logic for an older feature version
> after
> > it
> > > > has
> > > > >> > >>> migrated
> > > > >> > >>> > > to
> > > > >> > >>> > > > using the logic for a newer feature version (because
> > this
> > > > >> could
> > > > >> > >>> break the
> > > > >> > >>> > > > cluster!). For these cases, max_version_level will be
> > very
> > > > >> useful
> > > > >> > >>> for
> > > > >> > >>> > > > decision making.
> > > > >> > >>> > > >
> > > > >> > >>> > > > 2. On the other hand, imagine F as an external facing
> > > > feature.
> > > > >> > >>> External
> > > > >> > >>> > > > clients are not within the control of Broker cluster.
> An
> > > > >> external
> > > > >> > >>> client
> > > > >> > >>> > > > may not have upgraded it's code (yet) to use
> > > > >> 'max_version_level +
> > > > >> > >>> 1'.
> > > > >> > >>> > > But,
> > > > >> > >>> > > > the Kafka cluster could have been deployed with
> support
> > > for
> > > > >> > >>> > > > 'max_version_level + 1' of an external facing feature.
> > > Now,
> > > > >> these
> > > > >> > >>> > > external
> > > > >> > >>> > > > clients (until an upgrade) are benefitted in learning
> > > "what
> > > > >> is the
> > > > >> > >>> lowest
> > > > >> > >>> > > > common version for F among all brokers?". This is
> where
> > > the
> > > > >> > >>> > > > "min_version_level" becomes useful. Using this, a
> client
> > > > could
> > > > >> > >>> learn the
> > > > >> > >>> > > > specific supported versions that's lower than
> > > > >> max_version_level
> > > > >> > >>> (instead
> > > > >> > >>> > > of
> > > > >> > >>> > > > assuming that all brokers support the range: [1,
> > > > >> > >>> max_version_level]). For
> > > > >> > >>> > > > example, if the cluster deprecates
> "min_version_level",
> > > then
> > > > >> the
> > > > >> > >>> client
> > > > >> > >>> > > > becomes aware because it periodically learns the
> latest
> > > > >> > >>> > > "min_version_level"
> > > > >> > >>> > > > via ApiVersionsRequest.
> > > > >> > >>> > > >
> > > > >> > >>> > >
> > > > >> > >>> > > Thanks for the explanation. I agree that this does make
> > > sense
> > > > >> when
> > > > >> > >>> you
> > > > >> > >>> > > take the client perspective into account.
> > > > >> > >>> > >
> > > > >> > >>> > > best,
> > > > >> > >>> > > Colin
> > > > >> > >>> > >
> > > > >> > >>> > >
> > > > >> > >>> > > >
> > > > >> > >>> > > > Cheers,
> > > > >> > >>> > > > Kowshik
> > > > >> > >>> > > >
> > > > >> > >>> > > >
> > > > >> > >>> > > >
> > > > >> > >>> > > >
> > > > >> > >>> > > > On Thu, Apr 23, 2020 at 12:07 PM Colin McCabe <
> > > > >> cmccabe@apache.org>
> > > > >> > >>> > > wrote:
> > > > >> > >>> > > >
> > > > >> > >>> > > > > Hi Kowshik,
> > > > >> > >>> > > > >
> > > > >> > >>> > > > > Thanks again for working on this-- it looks great.
> I
> > > went
> > > > >> over
> > > > >> > >>> the KIP
> > > > >> > >>> > > > > again and have a few more comments.
> > > > >> > >>> > > > >
> > > > >> > >>> > > > > ===
> > > > >> > >>> > > > >
> > > > >> > >>> > > > > It would be good to note that deprecating a feature
> > > > version
> > > > >> (in
> > > > >> > >>> other
> > > > >> > >>> > > > > words, increasing minVersionLevel on the broker) is
> an
> > > > >> > >>> incompatible
> > > > >> > >>> > > change,
> > > > >> > >>> > > > > which requires a major release of Kafka.
> > > > >> > >>> > > > >
> > > > >> > >>> > > > > ===
> > > > >> > >>> > > > >
> > > > >> > >>> > > > > I think the strategy for transitioning from not
> > having a
> > > > >> > >>> /features
> > > > >> > >>> > > znode
> > > > >> > >>> > > > > to having one could use some work. The current
> > proposal
> > > is
> > > > >> to
> > > > >> > >>> wait for
> > > > >> > >>> > > all
> > > > >> > >>> > > > > the brokers to fill in their feature znodes and then
> > > pick
> > > > >> the
> > > > >> > >>> highest
> > > > >> > >>> > > > > common versions. But that requires blocking in the
> > > > >> controller
> > > > >> > >>> startup
> > > > >> > >>> > > code
> > > > >> > >>> > > > > until the whole cluster is active (technically, a
> > point
> > > in
> > > > >> time
> > > > >> > >>> which
> > > > >> > >>> > > we
> > > > >> > >>> > > > > never really know that we have reached...)
> > > > >> > >>> > > > >
> > > > >> > >>> > > > > Instead, I think it would be better to have a
> strategy
> > > > like
> > > > >> this:
> > > > >> > >>> > > > > 1. If the controller comes up and there is no
> > /features
> > > > >> znode
> > > > >> > >>> AND the
> > > > >> > >>> > > IBP
> > > > >> > >>> > > > > is less than 2.6, create a /features znode where all
> > the
> > > > >> > >>> features are
> > > > >> > >>> > > > > disabled.
> > > > >> > >>> > > > > 2. If the controller comes up and there is no
> > /features
> > > > >> znode
> > > > >> > >>> AND the
> > > > >> > >>> > > IBP
> > > > >> > >>> > > > > is greater than or equal to 2.6, create a /features
> > > znode
> > > > >> where
> > > > >> > >>> all the
> > > > >> > >>> > > > > features are enabled at the highest versions
> supported
> > > by
> > > > >> the
> > > > >> > >>> > > controller.
> > > > >> > >>> > > > >
> > > > >> > >>> > > > > People upgrading from the pre-KIP-584
> > > > >> > >>> <https://issues.apache.org/jira/browse/KIP-584>
> > > > >> > >>> > > > > <https://issues.apache.org/jira/browse/KIP-584>
> world
> > > > will
> > > > >> end
> > > > >> > >>> up in
> > > > >> > >>> > > case
> > > > >> > >>> > > > > #1 because they have to do a double roll to upgrade,
> > and
> > > > >> during
> > > > >> > >>> the
> > > > >> > >>> > > first
> > > > >> > >>> > > > > roll, the IBP is unchanged. People creating new
> > > clusters
> > > > >> from
> > > > >> > >>> scratch
> > > > >> > >>> > > will
> > > > >> > >>> > > > > end up in case #2, which is what we want since we
> > don't
> > > > >> want a
> > > > >> > >>> brand
> > > > >> > >>> > > new
> > > > >> > >>> > > > > cluster to be using old feature flag versions.
> > > > >> > >>> > > > >
> > > > >> > >>> > > > > ===
> > > > >> > >>> > > > >
> > > > >> > >>> > > > > UpdateFeaturesResponse#ErrorMessage should specify
> > > > >> > >>> nullableVersions
> > > > >> > >>> > > since
> > > > >> > >>> > > > > null is a valid value here
> > > > >> > >>> > > > >
> > > > >> > >>> > > > > Also, in the message format, the tags we use need to
> > > start
> > > > >> at 0.
> > > > >> > >>> > > > >
> > > > >> > >>> > > > > ===
> > > > >> > >>> > > > >
> > > > >> > >>> > > > > I don't think we need the FEATURE_UPDATE_IN_PROGRESS
> > > error
> > > > >> > >>> code. The
> > > > >> > >>> > > > > controller is basically single-threaded and will
> only
> > do
> > > > >> one of
> > > > >> > >>> these
> > > > >> > >>> > > > > operations at once. Even if it weren't, though, we
> > > could
> > > > >> simply
> > > > >> > >>> block
> > > > >> > >>> > > the
> > > > >> > >>> > > > > second operation behind the first one.
> > > > >> > >>> > > > >
> > > > >> > >>> > > > > ===
> > > > >> > >>> > > > >
> > > > >> > >>> > > > > For updateFeatures, it would be good to specify that
> > if
> > > a
> > > > >> single
> > > > >> > >>> > > feature
> > > > >> > >>> > > > > version update in the batch can't be done, none of
> > them
> > > > are
> > > > >> > >>> done. I
> > > > >> > >>> > > think
> > > > >> > >>> > > > > this was the intention, but I wasn't able to find it
> > > > >> spelled out
> > > > >> > >>> > > (maybe i
> > > > >> > >>> > > > > missed it).
> > > > >> > >>> > > > >
> > > > >> > >>> > > > > ===
> > > > >> > >>> > > > >
> > > > >> > >>> > > > > And now, something a little bit bigger (sorry). For
> > > > >> finalized
> > > > >> > >>> > > features,
> > > > >> > >>> > > > > why do we need both min_version_level and
> > > > max_version_level?
> > > > >> > >>> Assuming
> > > > >> > >>> > > that
> > > > >> > >>> > > > > we want all the brokers to be on the same feature
> > > version
> > > > >> level,
> > > > >> > >>> we
> > > > >> > >>> > > really
> > > > >> > >>> > > > > only care about three numbers for each feature,
> right?
> > > > The
> > > > >> > >>> minimum
> > > > >> > >>> > > > > supported version level, the maximum supported
> version
> > > > >> level,
> > > > >> > >>> and the
> > > > >> > >>> > > > > current active version level.
> > > > >> > >>> > > > >
> > > > >> > >>> > > > > We don't actually want different brokers to be on
> > > > different
> > > > >> > >>> versions of
> > > > >> > >>> > > > > the same feature, right? So we can just have one
> > number
> > > > for
> > > > >> > >>> current
> > > > >> > >>> > > > > version level, rather than two. At least that's
> what
> > I
> > > > was
> > > > >> > >>> thinking
> > > > >> > >>> > > -- let
> > > > >> > >>> > > > > me know if I missed something.
> > > > >> > >>> > > > >
> > > > >> > >>> > > > > best,
> > > > >> > >>> > > > > Colin
> > > > >> > >>> > > > >
> > > > >> > >>> > > > >
> > > > >> > >>> > > > > On Tue, Apr 21, 2020, at 13:01, Dhruvil Shah wrote:
> > > > >> > >>> > > > > > Thanks for the KIP! +1 (non-binding)
> > > > >> > >>> > > > > >
> > > > >> > >>> > > > > > On Tue, Apr 21, 2020 at 6:09 AM David Jacot <
> > > > >> > >>> djacot@confluent.io>
> > > > >> > >>> > > wrote:
> > > > >> > >>> > > > > >
> > > > >> > >>> > > > > > > Great KIP, thanks! +1 (non-binding)
> > > > >> > >>> > > > > > >
> > > > >> > >>> > > > > > > On Fri, Apr 17, 2020 at 8:56 PM Guozhang Wang <
> > > > >> > >>> wangguoz@gmail.com>
> > > > >> > >>> > > > > wrote:
> > > > >> > >>> > > > > > >
> > > > >> > >>> > > > > > > > Thanks for the great KIP Kowshik, +1
> (binding).
> > > > >> > >>> > > > > > > >
> > > > >> > >>> > > > > > > > On Fri, Apr 17, 2020 at 11:22 AM Jun Rao <
> > > > >> jun@confluent.io
> > > > >> > >>> >
> > > > >> > >>> > > wrote:
> > > > >> > >>> > > > > > > >
> > > > >> > >>> > > > > > > > > Hi, Kowshik,
> > > > >> > >>> > > > > > > > >
> > > > >> > >>> > > > > > > > > Thanks for the KIP. +1
> > > > >> > >>> > > > > > > > >
> > > > >> > >>> > > > > > > > > Jun
> > > > >> > >>> > > > > > > > >
> > > > >> > >>> > > > > > > > > On Thu, Apr 16, 2020 at 11:14 AM Kowshik
> > > Prakasam
> > > > <
> > > > >> > >>> > > > > > > > kprakasam@confluent.io>
> > > > >> > >>> > > > > > > > > wrote:
> > > > >> > >>> > > > > > > > >
> > > > >> > >>> > > > > > > > > > Hi all,
> > > > >> > >>> > > > > > > > > >
> > > > >> > >>> > > > > > > > > > I'd like to start a vote for KIP-584
> > > > >> > >>> <https://issues.apache.org/jira/browse/KIP-584>
> > > > >> > >>> > > > > <https://issues.apache.org/jira/browse/KIP-584>.
> The
> > > link
> > > > >> to
> > > > >> > >>> the KIP
> > > > >> > >>> > > can
> > > > >> > >>> > > > > be
> > > > >> > >>> > > > > > > found
> > > > >> > >>> > > > > > > > > > here:
> > > > >> > >>> > > > > > > > > >
> > > > >> > >>> > > > > > > > > >
> > > > >> > >>> > > > > > > > >
> > > > >> > >>> > > > > > > >
> > > > >> > >>> > > > > > >
> > > > >> > >>> > > > >
> > > > >> > >>> > >
> > > > >> > >>>
> > > > >>
> > > >
> > >
> >
> https://cwiki.apache.org/confluence/display/KAFKA/KIP-584%3A+Versioning+scheme+for+features
> > > > >> > >>> > > > > > > > > > .
> > > > >> > >>> > > > > > > > > >
> > > > >> > >>> > > > > > > > > > Thanks!
> > > > >> > >>> > > > > > > > > >
> > > > >> > >>> > > > > > > > > >
> > > > >> > >>> > > > > > > > > > Cheers,
> > > > >> > >>> > > > > > > > > > Kowshik
> > > > >> > >>> > > > > > > > > >
> > > > >> > >>> > > > > > > > >
> > > > >> > >>> > > > > > > >
> > > > >> > >>> > > > > > > >
> > > > >> > >>> > > > > > > > --
> > > > >> > >>> > > > > > > > -- Guozhang
> > > > >> > >>> > > > > > > >
> > > > >> > >>> > > > > > >
> > > > >> > >>> > > > > >
> > > > >> > >>> > > > >
> > > > >> > >>> > > >
> > > > >> > >>> > >
> > > > >> > >>> >
> > > > >> > >>>
> > > > >> > >>
> > > > >> >
> > > > >>
> > > > >
> > > >
> > >
> >
>
Re: [VOTE] KIP-584: Versioning scheme for features
Posted by Jun Rao <ju...@confluent.io>.
Hi, Kowshik,
Thanks for the follow up. Both look good to me.
For 2, it would be useful to also add that an admin should make sure that
no clients are using a deprecated feature version (e.g. using the client
version metric) before deploying a release that deprecates it.
Thanks,
Jun
On Tue, Oct 6, 2020 at 3:46 PM Kowshik Prakasam <kp...@confluent.io>
wrote:
> Hi Jun,
>
> I have added the following details in the KIP-584 write up:
>
> 1. Deployment, IBP deprecation and avoidance of double rolls. This section
> talks about the various phases of work that would be required to use this
> KIP to eventually avoid Broker double rolls in the cluster (whenever IBP
> values are advanced). Link to section:
>
> https://cwiki.apache.org/confluence/display/KAFKA/KIP-584%3A+Versioning+scheme+for+features#KIP584:Versioningschemeforfeatures-Deployment,IBPdeprecationandavoidanceofdoublerolls
> .
>
> 2. Feature version deprecation. This section explains the idea for feature
> version deprecation (using highest supported feature min version) which you
> had proposed during code review:
>
> https://cwiki.apache.org/confluence/display/KAFKA/KIP-584%3A+Versioning+scheme+for+features#KIP584:Versioningschemeforfeatures-Featureversiondeprecation
> .
>
> Please let me know if you have any questions.
>
>
> Cheers,
> Kowshik
>
>
> On Tue, Sep 29, 2020 at 11:07 AM Jun Rao <ju...@confluent.io> wrote:
>
> > Hi, Kowshik,
> >
> > Thanks for the update. Regarding enabling a single rolling restart in the
> > future, could we sketch out a bit how this will work by treating IBP as a
> > feature? For example, IBP currently uses the release version and this KIP
> > uses an integer for versions. How do we bridge the gap between the two?
> > Does min.version still make sense for IBP as a feature?
> >
> > Thanks,
> >
> > Jun
> >
> > On Fri, Sep 25, 2020 at 5:57 PM Kowshik Prakasam <kprakasam@confluent.io
> >
> > wrote:
> >
> > > Hi Colin,
> > >
> > > Thanks for the feedback. Those are very good points. I have made the
> > > following changes to the KIP as you had suggested:
> > > 1. Included the `timeoutMs` field in the `UpdateFeaturesRequest`
> schema.
> > > The initial implementation won't be making use of the field, but we can
> > > always use it in the future as the need arises.
> > > 2. Modified the `FinalizedFeaturesEpoch` field in `ApiVersionsResponse`
> > to
> > > use int64. This is to avoid overflow problems in the future once ZK is
> > > gone.
> > >
> > > I have also incorporated these changes into the versioning write path
> PR
> > > that is currently under review:
> > https://github.com/apache/kafka/pull/9001.
> > >
> > >
> > > Cheers,
> > > Kowshik
> > >
> > >
> > >
> > > On Fri, Sep 25, 2020 at 4:57 PM Kowshik Prakasam <
> kprakasam@confluent.io
> > >
> > > wrote:
> > >
> > > > Hi Jun,
> > > >
> > > > Thanks for the feedback. It's a very good point. I have now modified
> > the
> > > > KIP-584 write-up "goals" section a bit. It now mentions one of the
> > goals
> > > as
> > > > enabling rolling upgrades using a single restart (instead of 2).
> Also I
> > > > have removed the text explicitly aiming for deprecation of IBP. Note
> > that
> > > > previously under "Potential features in Kafka" the IBP was mentioned
> > > under
> > > > point (4) as a possible coarse-grained feature. Hopefully, now the 2
> > > > sections of the KIP align with each other well.
> > > >
> > > >
> > > > Cheers,
> > > > Kowshik
> > > >
> > > >
> > > > On Fri, Sep 25, 2020 at 2:03 PM Colin McCabe <cm...@apache.org>
> > wrote:
> > > >
> > > >> On Tue, Sep 22, 2020, at 00:43, Kowshik Prakasam wrote:
> > > >> > Hi all,
> > > >> >
> > > >> > I wanted to let you know that I have made the following changes to
> > the
> > > >> > KIP-584 write up. The purpose is to ensure the design is correct
> > for a
> > > >> few
> > > >> > things which came up during implementation:
> > > >> >
> > > >>
> > > >> Hi Kowshik,
> > > >>
> > > >> Thanks for the updates.
> > > >>
> > > >> >
> > > >> > 1. Per FeatureUpdate error code: The UPDATE_FEATURES controller
> API
> > is
> > > >> no
> > > >> > longer transactional. Going forward, we allow for individual
> > > >> FeatureUpdate
> > > >> > to succeed/fail in the request. As a result, the response schema
> now
> > > >> > contains an error code per FeatureUpdate as well as a top-level
> > error
> > > >> code.
> > > >> > Overall this is a better design because it better represents the
> > > nature
> > > >> of
> > > >> > the API: each FeatureUpdate in the request is independent of the
> > other
> > > >> > updates, and the controller can process/apply these independently
> to
> > > ZK.
> > > >> > When an UPDATE_FEATURES request fails, this new design provides
> > better
> > > >> > clarity to the caller on which FeatureUpdate could not be applied
> > (via
> > > >> the
> > > >> > individual error codes). In the previous design, we were unable to
> > > >> achieve
> > > >> > such an increased level of clarity in communicating the error
> codes.
> > > >> >
> > > >>
> > > >> OK
> > > >>
> > > >> >
> > > >> > 2. Due to #1, there were some minor changes required to the
> proposed
> > > >> Admin
> > > >> > APIs (describeFeatures and updateFeatures). A few unnecessary
> public
> > > >> APIs
> > > >> > have been removed, and couple essential ones have been added. The
> > > latest
> > > >> > changes now represent the latest design.
> > > >> >
> > > >> > 3. The timeoutMs field has been removed from the the
> UPDATE_FEATURES
> > > API
> > > >> > request, since it was not found to be required during
> > implementation.
> > > >> >
> > > >>
> > > >> Please don't get rid of timeoutMs. timeoutMs is required if you
> want
> > to
> > > >> implement the ability to timeout the call if the controller can't
> get
> > > to it
> > > >> in time. This is important for avoiding congestion collapse where
> the
> > > >> controller collapses under the weight of lots of retries of the same
> > > set of
> > > >> calls.
> > > >>
> > > >> We may not be able to do it in the initial implementation, but we
> will
> > > >> eventually implement this for all the controller-bound RPCs.
> > > >>
> > > >> > >
> > > >> > > 2. Finalized feature version epoch data type has been made to be
> > > int32
> > > >> > > (instead of int64). The reason is that the epoch value is the
> > value
> > > >> of ZK
> > > >> > > node version, whose data type is int32.
> > > >> > >
> > > >>
> > > >> Sorry, I missed this earlier. Using 16 bit feature levels seems
> fine.
> > > >> However, please don't use a 32-bit epoch here. We deliberately made
> > the
> > > >> epoch 64 bits to avoid overflow problems in the future once ZK is
> > gone.
> > > >>
> > > >> best,
> > > >> Colin
> > > >>
> > > >> > > 3. Introduced a new 'status' field in the '/features' ZK node
> > > schema.
> > > >> The
> > > >> > > purpose is to implement Colin's earlier point for the strategy
> for
> > > >> > > transitioning from not having a /features znode to having one.
> An
> > > >> > > explanation has been provided in the following section of the
> KIP
> > > >> detailing
> > > >> > > the different cases:
> > > >> > >
> > > >>
> > >
> >
> https://cwiki.apache.org/confluence/display/KAFKA/KIP-584%3A+Versioning+scheme+for+features#KIP584:Versioningschemeforfeatures-FeatureZKnodestatus
> > > >> > > .
> > > >> > >
> > > >> > > Please let me know if you have any questions or concerns.
> > > >> > >
> > > >> > >
> > > >> > > Cheers,
> > > >> > > Kowshik
> > > >> > >
> > > >> > >
> > > >> > >
> > > >> > > Cheers,
> > > >> > > Kowshik
> > > >> > >
> > > >> > > On Tue, Apr 28, 2020 at 11:24 PM Kowshik Prakasam <
> > > >> kprakasam@confluent.io>
> > > >> > > wrote:
> > > >> > >
> > > >> > >> Hi all,
> > > >> > >>
> > > >> > >> This KIP vote has been open for ~12 days. The summary of the
> > votes
> > > is
> > > >> > >> that we have 3 binding votes (Colin, Guozhang, Jun), and 3
> > > >> non-binding
> > > >> > >> votes (David, Dhruvil, Boyang). Therefore, the KIP vote passes.
> > > I'll
> > > >> mark
> > > >> > >> KIP as accepted and start working on the implementation.
> > > >> > >>
> > > >> > >> Thanks a lot!
> > > >> > >>
> > > >> > >>
> > > >> > >> Cheers,
> > > >> > >> Kowshik
> > > >> > >>
> > > >> > >> On Mon, Apr 27, 2020 at 12:15 PM Colin McCabe <
> > cmccabe@apache.org>
> > > >> wrote:
> > > >> > >>
> > > >> > >>> Thanks, Kowshik. +1 (binding)
> > > >> > >>>
> > > >> > >>> best,
> > > >> > >>> Colin
> > > >> > >>>
> > > >> > >>> On Sat, Apr 25, 2020, at 13:20, Kowshik Prakasam wrote:
> > > >> > >>> > Hi Colin,
> > > >> > >>> >
> > > >> > >>> > Thanks for the explanation! I agree with you, and I have
> > updated
> > > >> the
> > > >> > >>> > KIP.
> > > >> > >>> > Here is a link to relevant section:
> > > >> > >>> >
> > > >> > >>>
> > > >>
> > >
> >
> https://cwiki.apache.org/confluence/display/KAFKA/KIP-584%3A+Versioning+scheme+for+features#KIP-584:Versioningschemeforfeatures-Controller:ZKnodebootstrapwithdefaultvalues
> > > >> > >>> >
> > > >> > >>> >
> > > >> > >>> > Cheers,
> > > >> > >>> > Kowshik
> > > >> > >>> >
> > > >> > >>> > On Fri, Apr 24, 2020 at 8:50 PM Colin McCabe <
> > > cmccabe@apache.org>
> > > >> > >>> wrote:
> > > >> > >>> >
> > > >> > >>> > > On Fri, Apr 24, 2020, at 00:01, Kowshik Prakasam wrote:
> > > >> > >>> > > > (Kowshik): Great point! However for case #1, I'm not
> sure
> > > why
> > > >> we
> > > >> > >>> need to
> > > >> > >>> > > > create a '/features' ZK node with disabled features.
> > > Instead,
> > > >> do
> > > >> > >>> you see
> > > >> > >>> > > > any drawback if we just do not create it? i.e. if IBP is
> > > less
> > > >> than
> > > >> > >>> 2.6,
> > > >> > >>> > > the
> > > >> > >>> > > > controller treats the case as though the versioning
> system
> > > is
> > > >> > >>> completely
> > > >> > >>> > > > disabled, and would not create a non-existing
> '/features'
> > > >> node.
> > > >> > >>> > >
> > > >> > >>> > > Hi Kowshik,
> > > >> > >>> > >
> > > >> > >>> > > When the IBP is less than 2.6, but the software has been
> > > >> upgraded to
> > > >> > >>> a
> > > >> > >>> > > state where it supports this KIP, that
> > > >> > >>> > > means the user is upgrading from an earlier version of
> the
> > > >> > >>> software. In
> > > >> > >>> > > this case, we want to start with all the features disabled
> > and
> > > >> allow
> > > >> > >>> the
> > > >> > >>> > > user to enable them when they are ready.
> > > >> > >>> > >
> > > >> > >>> > > Enabling all the possible features immediately after an
> > > upgrade
> > > >> > >>> could be
> > > >> > >>> > > harmful to the cluster. On the other hand, for a new
> > cluster,
> > > >> we do
> > > >> > >>> want
> > > >> > >>> > > to enable all the possible features immediately . I was
> > > >> proposing
> > > >> > >>> this as a
> > > >> > >>> > > way to distinguish the two cases (since the new cluster
> will
> > > >> never be
> > > >> > >>> > > started with an old IBP).
> > > >> > >>> > >
> > > >> > >>> > > > Colin MccCabe wrote:
> > > >> > >>> > > > > And now, something a little bit bigger (sorry). For
> > > >> finalized
> > > >> > >>> > > features,
> > > >> > >>> > > > > why do we need both min_version_level and
> > > max_version_level?
> > > >> > >>> Assuming
> > > >> > >>> > > that
> > > >> > >>> > > > > we want all the brokers to be on the same feature
> > version
> > > >> level,
> > > >> > >>> we
> > > >> > >>> > > really only care
> > > >> > >>> > > > > about three numbers for each feature, right? The
> > minimum
> > > >> > >>> supported
> > > >> > >>> > > version
> > > >> > >>> > > > > level, the maximum supported version level, and the
> > > current
> > > >> > >>> active
> > > >> > >>> > > version level.
> > > >> > >>> > > >
> > > >> > >>> > > > > We don't actually want different brokers to be on
> > > different
> > > >> > >>> versions of
> > > >> > >>> > > > > the same feature, right? So we can just have one
> number
> > > for
> > > >> > >>> current
> > > >> > >>> > > > > version level, rather than two. At least that's what
> I
> > > was
> > > >> > >>> thinking
> > > >> > >>> > > -- let
> > > >> > >>> > > > > me know if I missed something.
> > > >> > >>> > > >
> > > >> > >>> > > > (Kowshik): It is my understanding that the "current
> active
> > > >> version
> > > >> > >>> level"
> > > >> > >>> > > > that you have mentioned, is the "max_version_level". But
> > we
> > > >> still
> > > >> > >>> > > > maintain/publish both min and max version levels,
> because,
> > > the
> > > >> > >>> detail
> > > >> > >>> > > about
> > > >> > >>> > > > min level is useful to external clients. This is
> described
> > > >> below.
> > > >> > >>> > > >
> > > >> > >>> > > > For any feature F, think of the closed range:
> > > >> [min_version_level,
> > > >> > >>> > > > max_version_level] as the range of finalized versions,
> > > that's
> > > >> > >>> guaranteed
> > > >> > >>> > > to
> > > >> > >>> > > > be supported by all brokers in the cluster.
> > > >> > >>> > > > - "max_version_level" is the finalized highest common
> > > version
> > > >> > >>> among all
> > > >> > >>> > > > brokers,
> > > >> > >>> > > > - "min_version_level" is the finalized lowest common
> > > version
> > > >> > >>> among all
> > > >> > >>> > > > brokers.
> > > >> > >>> > > >
> > > >> > >>> > > > Next, think of "client" here as the "user of the new
> > feature
> > > >> > >>> versions
> > > >> > >>> > > > system". Imagine that such a client learns about
> finalized
> > > >> feature
> > > >> > >>> > > > versions, and exercises some logic based on the version.
> > > These
> > > >> > >>> clients
> > > >> > >>> > > can
> > > >> > >>> > > > be of 2 types:
> > > >> > >>> > > > 1. Some part of the broker code itself could behave
> like a
> > > >> client
> > > >> > >>> trying
> > > >> > >>> > > to
> > > >> > >>> > > > use some feature that's "internal" to the broker
> cluster.
> > > >> Such a
> > > >> > >>> client
> > > >> > >>> > > > would learn the latest finalized features via ZK.
> > > >> > >>> > > > 2. An external system (ex: Streams) could behave like a
> > > >> client,
> > > >> > >>> trying to
> > > >> > >>> > > > use some "external" facing feature. Such a client would
> > > learn
> > > >> > >>> latest
> > > >> > >>> > > > finalized features via ApiVersionsRequest. Ex:
> > > >> group_coordinator
> > > >> > >>> feature
> > > >> > >>> > > > described in the KIP.
> > > >> > >>> > > >
> > > >> > >>> > > > Next, imagine that for F, the max_version_level is
> > > >> successfully
> > > >> > >>> bumped by
> > > >> > >>> > > > +1 (via Controller API). Now it is guaranteed that all
> > > brokers
> > > >> > >>> (i.e.
> > > >> > >>> > > > internal clients) understand max_version_level + 1.
> > However,
> > > >> it is
> > > >> > >>> still
> > > >> > >>> > > > not guaranteed that all external clients have support
> for
> > > (or
> > > >> have
> > > >> > >>> > > > activated) the logic for the newer version. Why?
> Because,
> > > >> this is
> > > >> > >>> > > > subjective as explained next:
> > > >> > >>> > > >
> > > >> > >>> > > > 1. On one hand, imagine F as an internal feature only
> > > >> relevant to
> > > >> > >>> > > Brokers.
> > > >> > >>> > > > The binary for the internal client logic is controlled
> by
> > > >> Broker
> > > >> > >>> cluster
> > > >> > >>> > > > deployments. When shipping a new Broker release, we
> > wouldn't
> > > >> bump
> > > >> > >>> max
> > > >> > >>> > > > "supported" feature version for F by 1, unless we have
> > > >> introduced
> > > >> > >>> some
> > > >> > >>> > > new
> > > >> > >>> > > > logic (with a potentially breaking change) in the
> Broker.
> > > >> > >>> Furthermore,
> > > >> > >>> > > such
> > > >> > >>> > > > feature logic in the broker should/will not be
> implemented
> > > in
> > > >> a
> > > >> > >>> way that
> > > >> > >>> > > it
> > > >> > >>> > > > would activate logic for an older feature version after
> it
> > > has
> > > >> > >>> migrated
> > > >> > >>> > > to
> > > >> > >>> > > > using the logic for a newer feature version (because
> this
> > > >> could
> > > >> > >>> break the
> > > >> > >>> > > > cluster!). For these cases, max_version_level will be
> very
> > > >> useful
> > > >> > >>> for
> > > >> > >>> > > > decision making.
> > > >> > >>> > > >
> > > >> > >>> > > > 2. On the other hand, imagine F as an external facing
> > > feature.
> > > >> > >>> External
> > > >> > >>> > > > clients are not within the control of Broker cluster. An
> > > >> external
> > > >> > >>> client
> > > >> > >>> > > > may not have upgraded it's code (yet) to use
> > > >> 'max_version_level +
> > > >> > >>> 1'.
> > > >> > >>> > > But,
> > > >> > >>> > > > the Kafka cluster could have been deployed with support
> > for
> > > >> > >>> > > > 'max_version_level + 1' of an external facing feature.
> > Now,
> > > >> these
> > > >> > >>> > > external
> > > >> > >>> > > > clients (until an upgrade) are benefitted in learning
> > "what
> > > >> is the
> > > >> > >>> lowest
> > > >> > >>> > > > common version for F among all brokers?". This is where
> > the
> > > >> > >>> > > > "min_version_level" becomes useful. Using this, a client
> > > could
> > > >> > >>> learn the
> > > >> > >>> > > > specific supported versions that's lower than
> > > >> max_version_level
> > > >> > >>> (instead
> > > >> > >>> > > of
> > > >> > >>> > > > assuming that all brokers support the range: [1,
> > > >> > >>> max_version_level]). For
> > > >> > >>> > > > example, if the cluster deprecates "min_version_level",
> > then
> > > >> the
> > > >> > >>> client
> > > >> > >>> > > > becomes aware because it periodically learns the latest
> > > >> > >>> > > "min_version_level"
> > > >> > >>> > > > via ApiVersionsRequest.
> > > >> > >>> > > >
> > > >> > >>> > >
> > > >> > >>> > > Thanks for the explanation. I agree that this does make
> > sense
> > > >> when
> > > >> > >>> you
> > > >> > >>> > > take the client perspective into account.
> > > >> > >>> > >
> > > >> > >>> > > best,
> > > >> > >>> > > Colin
> > > >> > >>> > >
> > > >> > >>> > >
> > > >> > >>> > > >
> > > >> > >>> > > > Cheers,
> > > >> > >>> > > > Kowshik
> > > >> > >>> > > >
> > > >> > >>> > > >
> > > >> > >>> > > >
> > > >> > >>> > > >
> > > >> > >>> > > > On Thu, Apr 23, 2020 at 12:07 PM Colin McCabe <
> > > >> cmccabe@apache.org>
> > > >> > >>> > > wrote:
> > > >> > >>> > > >
> > > >> > >>> > > > > Hi Kowshik,
> > > >> > >>> > > > >
> > > >> > >>> > > > > Thanks again for working on this-- it looks great. I
> > went
> > > >> over
> > > >> > >>> the KIP
> > > >> > >>> > > > > again and have a few more comments.
> > > >> > >>> > > > >
> > > >> > >>> > > > > ===
> > > >> > >>> > > > >
> > > >> > >>> > > > > It would be good to note that deprecating a feature
> > > version
> > > >> (in
> > > >> > >>> other
> > > >> > >>> > > > > words, increasing minVersionLevel on the broker) is an
> > > >> > >>> incompatible
> > > >> > >>> > > change,
> > > >> > >>> > > > > which requires a major release of Kafka.
> > > >> > >>> > > > >
> > > >> > >>> > > > > ===
> > > >> > >>> > > > >
> > > >> > >>> > > > > I think the strategy for transitioning from not
> having a
> > > >> > >>> /features
> > > >> > >>> > > znode
> > > >> > >>> > > > > to having one could use some work. The current
> proposal
> > is
> > > >> to
> > > >> > >>> wait for
> > > >> > >>> > > all
> > > >> > >>> > > > > the brokers to fill in their feature znodes and then
> > pick
> > > >> the
> > > >> > >>> highest
> > > >> > >>> > > > > common versions. But that requires blocking in the
> > > >> controller
> > > >> > >>> startup
> > > >> > >>> > > code
> > > >> > >>> > > > > until the whole cluster is active (technically, a
> point
> > in
> > > >> time
> > > >> > >>> which
> > > >> > >>> > > we
> > > >> > >>> > > > > never really know that we have reached...)
> > > >> > >>> > > > >
> > > >> > >>> > > > > Instead, I think it would be better to have a strategy
> > > like
> > > >> this:
> > > >> > >>> > > > > 1. If the controller comes up and there is no
> /features
> > > >> znode
> > > >> > >>> AND the
> > > >> > >>> > > IBP
> > > >> > >>> > > > > is less than 2.6, create a /features znode where all
> the
> > > >> > >>> features are
> > > >> > >>> > > > > disabled.
> > > >> > >>> > > > > 2. If the controller comes up and there is no
> /features
> > > >> znode
> > > >> > >>> AND the
> > > >> > >>> > > IBP
> > > >> > >>> > > > > is greater than or equal to 2.6, create a /features
> > znode
> > > >> where
> > > >> > >>> all the
> > > >> > >>> > > > > features are enabled at the highest versions supported
> > by
> > > >> the
> > > >> > >>> > > controller.
> > > >> > >>> > > > >
> > > >> > >>> > > > > People upgrading from the pre-KIP-584
> > > >> > >>> <https://issues.apache.org/jira/browse/KIP-584>
> > > >> > >>> > > > > <https://issues.apache.org/jira/browse/KIP-584> world
> > > will
> > > >> end
> > > >> > >>> up in
> > > >> > >>> > > case
> > > >> > >>> > > > > #1 because they have to do a double roll to upgrade,
> and
> > > >> during
> > > >> > >>> the
> > > >> > >>> > > first
> > > >> > >>> > > > > roll, the IBP is unchanged. People creating new
> > clusters
> > > >> from
> > > >> > >>> scratch
> > > >> > >>> > > will
> > > >> > >>> > > > > end up in case #2, which is what we want since we
> don't
> > > >> want a
> > > >> > >>> brand
> > > >> > >>> > > new
> > > >> > >>> > > > > cluster to be using old feature flag versions.
> > > >> > >>> > > > >
> > > >> > >>> > > > > ===
> > > >> > >>> > > > >
> > > >> > >>> > > > > UpdateFeaturesResponse#ErrorMessage should specify
> > > >> > >>> nullableVersions
> > > >> > >>> > > since
> > > >> > >>> > > > > null is a valid value here
> > > >> > >>> > > > >
> > > >> > >>> > > > > Also, in the message format, the tags we use need to
> > start
> > > >> at 0.
> > > >> > >>> > > > >
> > > >> > >>> > > > > ===
> > > >> > >>> > > > >
> > > >> > >>> > > > > I don't think we need the FEATURE_UPDATE_IN_PROGRESS
> > error
> > > >> > >>> code. The
> > > >> > >>> > > > > controller is basically single-threaded and will only
> do
> > > >> one of
> > > >> > >>> these
> > > >> > >>> > > > > operations at once. Even if it weren't, though, we
> > could
> > > >> simply
> > > >> > >>> block
> > > >> > >>> > > the
> > > >> > >>> > > > > second operation behind the first one.
> > > >> > >>> > > > >
> > > >> > >>> > > > > ===
> > > >> > >>> > > > >
> > > >> > >>> > > > > For updateFeatures, it would be good to specify that
> if
> > a
> > > >> single
> > > >> > >>> > > feature
> > > >> > >>> > > > > version update in the batch can't be done, none of
> them
> > > are
> > > >> > >>> done. I
> > > >> > >>> > > think
> > > >> > >>> > > > > this was the intention, but I wasn't able to find it
> > > >> spelled out
> > > >> > >>> > > (maybe i
> > > >> > >>> > > > > missed it).
> > > >> > >>> > > > >
> > > >> > >>> > > > > ===
> > > >> > >>> > > > >
> > > >> > >>> > > > > And now, something a little bit bigger (sorry). For
> > > >> finalized
> > > >> > >>> > > features,
> > > >> > >>> > > > > why do we need both min_version_level and
> > > max_version_level?
> > > >> > >>> Assuming
> > > >> > >>> > > that
> > > >> > >>> > > > > we want all the brokers to be on the same feature
> > version
> > > >> level,
> > > >> > >>> we
> > > >> > >>> > > really
> > > >> > >>> > > > > only care about three numbers for each feature, right?
> > > The
> > > >> > >>> minimum
> > > >> > >>> > > > > supported version level, the maximum supported version
> > > >> level,
> > > >> > >>> and the
> > > >> > >>> > > > > current active version level.
> > > >> > >>> > > > >
> > > >> > >>> > > > > We don't actually want different brokers to be on
> > > different
> > > >> > >>> versions of
> > > >> > >>> > > > > the same feature, right? So we can just have one
> number
> > > for
> > > >> > >>> current
> > > >> > >>> > > > > version level, rather than two. At least that's what
> I
> > > was
> > > >> > >>> thinking
> > > >> > >>> > > -- let
> > > >> > >>> > > > > me know if I missed something.
> > > >> > >>> > > > >
> > > >> > >>> > > > > best,
> > > >> > >>> > > > > Colin
> > > >> > >>> > > > >
> > > >> > >>> > > > >
> > > >> > >>> > > > > On Tue, Apr 21, 2020, at 13:01, Dhruvil Shah wrote:
> > > >> > >>> > > > > > Thanks for the KIP! +1 (non-binding)
> > > >> > >>> > > > > >
> > > >> > >>> > > > > > On Tue, Apr 21, 2020 at 6:09 AM David Jacot <
> > > >> > >>> djacot@confluent.io>
> > > >> > >>> > > wrote:
> > > >> > >>> > > > > >
> > > >> > >>> > > > > > > Great KIP, thanks! +1 (non-binding)
> > > >> > >>> > > > > > >
> > > >> > >>> > > > > > > On Fri, Apr 17, 2020 at 8:56 PM Guozhang Wang <
> > > >> > >>> wangguoz@gmail.com>
> > > >> > >>> > > > > wrote:
> > > >> > >>> > > > > > >
> > > >> > >>> > > > > > > > Thanks for the great KIP Kowshik, +1 (binding).
> > > >> > >>> > > > > > > >
> > > >> > >>> > > > > > > > On Fri, Apr 17, 2020 at 11:22 AM Jun Rao <
> > > >> jun@confluent.io
> > > >> > >>> >
> > > >> > >>> > > wrote:
> > > >> > >>> > > > > > > >
> > > >> > >>> > > > > > > > > Hi, Kowshik,
> > > >> > >>> > > > > > > > >
> > > >> > >>> > > > > > > > > Thanks for the KIP. +1
> > > >> > >>> > > > > > > > >
> > > >> > >>> > > > > > > > > Jun
> > > >> > >>> > > > > > > > >
> > > >> > >>> > > > > > > > > On Thu, Apr 16, 2020 at 11:14 AM Kowshik
> > Prakasam
> > > <
> > > >> > >>> > > > > > > > kprakasam@confluent.io>
> > > >> > >>> > > > > > > > > wrote:
> > > >> > >>> > > > > > > > >
> > > >> > >>> > > > > > > > > > Hi all,
> > > >> > >>> > > > > > > > > >
> > > >> > >>> > > > > > > > > > I'd like to start a vote for KIP-584
> > > >> > >>> <https://issues.apache.org/jira/browse/KIP-584>
> > > >> > >>> > > > > <https://issues.apache.org/jira/browse/KIP-584>. The
> > link
> > > >> to
> > > >> > >>> the KIP
> > > >> > >>> > > can
> > > >> > >>> > > > > be
> > > >> > >>> > > > > > > found
> > > >> > >>> > > > > > > > > > here:
> > > >> > >>> > > > > > > > > >
> > > >> > >>> > > > > > > > > >
> > > >> > >>> > > > > > > > >
> > > >> > >>> > > > > > > >
> > > >> > >>> > > > > > >
> > > >> > >>> > > > >
> > > >> > >>> > >
> > > >> > >>>
> > > >>
> > >
> >
> https://cwiki.apache.org/confluence/display/KAFKA/KIP-584%3A+Versioning+scheme+for+features
> > > >> > >>> > > > > > > > > > .
> > > >> > >>> > > > > > > > > >
> > > >> > >>> > > > > > > > > > Thanks!
> > > >> > >>> > > > > > > > > >
> > > >> > >>> > > > > > > > > >
> > > >> > >>> > > > > > > > > > Cheers,
> > > >> > >>> > > > > > > > > > Kowshik
> > > >> > >>> > > > > > > > > >
> > > >> > >>> > > > > > > > >
> > > >> > >>> > > > > > > >
> > > >> > >>> > > > > > > >
> > > >> > >>> > > > > > > > --
> > > >> > >>> > > > > > > > -- Guozhang
> > > >> > >>> > > > > > > >
> > > >> > >>> > > > > > >
> > > >> > >>> > > > > >
> > > >> > >>> > > > >
> > > >> > >>> > > >
> > > >> > >>> > >
> > > >> > >>> >
> > > >> > >>>
> > > >> > >>
> > > >> >
> > > >>
> > > >
> > >
> >
>