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Posted to user@cassandra.apache.org by "ZAIDI, ASAD A" <az...@att.com> on 2017/07/07 14:42:12 UTC
RE: Understanding of cassandra metrics
What exactly does mean CoordinatorScanLatency for example
CoordinatorScanLatency is a timer metric that present coordinator range scan latency for table.
Is it latency on full table scan or maybe range scan by clustering key?
It is range scan.. clustering key is used to only store data in sorted fashion – partition key along with chosen partitioner helps in range scan of data.
Can anybody write into partition while locked?
Writes are atomic – it depends on your chosen consistency level to determine if writes will fail or succeed.
From: Павел Сапежко [mailto:amelius0712@gmail.com]
Sent: Friday, July 07, 2017 8:23 AM
To: user@cassandra.apache.org
Subject: Re: Understanding of cassandra metrics
Are you really think that I don't read docs? Do you have enough information in the documentation? I think no. What exactly does mean CoordinatorScanLatency for example? Is it latency on full table scan or maybe range scan by clustering key? What exactly mean ViewLockAcquireTime? What is "partition lock"? Can anybody write into partition while locked? Etc.
пт, 7 июл. 2017 г. в 13:01, Ivan Iliev <iv...@gmail.com>>:
1st result on google returns:
http://cassandra.apache.org/doc/latest/operating/metrics.html<https://urldefense.proofpoint.com/v2/url?u=http-3A__cassandra.apache.org_doc_latest_operating_metrics.html&d=DwMFaQ&c=LFYZ-o9_HUMeMTSQicvjIg&r=FsmDztdsVuIKml8IDhdHdg&m=xLXSLhev337PLD18_DQUB610StqO2URoRumDH-UXdtk&s=xTDUr1_OtTvWNi15F4GNSYs6lzQHi-2wX7oa2T37RCY&e=>
On Fri, Jul 7, 2017 at 12:16 PM, Павел Сапежко <am...@gmail.com>> wrote:
Hello, I have several question about cassandra metrics. What does exactly mean the next metrics:
* CoordinatorReadLatency
* CoordinatorScanLatency
* ReadLatency
* RangeLatency
* ViewLockAcquireTime
* ViewReadTime
--
С уважением,
Павел Сапежко
skype: p.sapezhko
--
С уважением,
Павел Сапежко
skype: p.sapezhko
Re: Understanding of cassandra metrics
Posted by Павел Сапежко <am...@gmail.com>.
So, Range latency(or Scan in case of coordinator) appears only when we are
reading multiple partition key in the same query?
пт, 7 июл. 2017 г. в 20:29, Chris Lohfink <cl...@gmail.com>:
> The coordinator read/scan (Scan is just different naming for the Range, so
> coordinator view of RangeLatency) is the latencies from the coordinator
> perspective, so it includes network latency between replicas and such. This
> which is actually added for speculative retry (why there is no
> coordinatorWriteLatency). Only the CoordinatorReadLatency is used for it
> however.
>
> The Read/RangeLatency metrics are for local reads, basically just how long
> to read from disk and merge with sstables.
>
> The View* metrics are only relevant to materialized views. There actually
> is a partition lock for updates which ViewLockAcquireTime gives
> visibility too. Also there are sometimes reads required for updating
> materialized views, which ViewReadTime is for tracking. For more details id
> recommend
> https://opencredo.com/everything-need-know-cassandra-materialized-views/
>
> Chris
>
> On Fri, Jul 7, 2017 at 9:42 AM, ZAIDI, ASAD A <az...@att.com> wrote:
>
>> What exactly does mean CoordinatorScanLatency for example
>>
>> CoordinatorScanLatency is a timer metric that present coordinator range
>> scan latency for table.
>>
>> Is it latency on full table scan or maybe range scan by clustering key?
>>
>> It is range scan.. clustering key is used to only store
>> data in sorted fashion – partition key along with chosen partitioner helps
>> in range scan of data.
>>
>> Can anybody write into partition while locked?
>>
>> Writes are atomic – it depends on your chosen consistency
>> level to determine if writes will fail or succeed.
>>
>>
>>
>> *From:* Павел Сапежко [mailto:amelius0712@gmail.com]
>> *Sent:* Friday, July 07, 2017 8:23 AM
>> *To:* user@cassandra.apache.org
>> *Subject:* Re: Understanding of cassandra metrics
>>
>>
>>
>> Are you really think that I don't read docs? Do you have enough
>> information in the documentation? I think no. What exactly does mean CoordinatorScanLatency
>> for example? Is it latency on full table scan or maybe range scan by
>> clustering key? What exactly mean ViewLockAcquireTime? What is
>> "partition lock"? Can anybody write into partition while locked? Etc.
>>
>> пт, 7 июл. 2017 г. в 13:01, Ivan Iliev <iv...@gmail.com>:
>>
>> 1st result on google returns:
>>
>>
>>
>> http://cassandra.apache.org/doc/latest/operating/metrics.html
>> <https://urldefense.proofpoint.com/v2/url?u=http-3A__cassandra.apache.org_doc_latest_operating_metrics.html&d=DwMFaQ&c=LFYZ-o9_HUMeMTSQicvjIg&r=FsmDztdsVuIKml8IDhdHdg&m=xLXSLhev337PLD18_DQUB610StqO2URoRumDH-UXdtk&s=xTDUr1_OtTvWNi15F4GNSYs6lzQHi-2wX7oa2T37RCY&e=>
>>
>>
>>
>> On Fri, Jul 7, 2017 at 12:16 PM, Павел Сапежко <am...@gmail.com>
>> wrote:
>>
>> Hello, I have several question about cassandra metrics. What does exactly
>> mean the next metrics:
>>
>> - CoordinatorReadLatency
>> - CoordinatorScanLatency
>> - ReadLatency
>> - RangeLatency
>> - ViewLockAcquireTime
>> - ViewReadTime
>>
>> --
>>
>> С уважением,
>>
>> Павел Сапежко
>>
>> skype: p.sapezhko
>>
>>
>>
>> --
>>
>> С уважением,
>>
>> Павел Сапежко
>>
>> skype: p.sapezhko
>>
>
> --
С уважением,
Павел Сапежко
skype: p.sapezhko
Re: Understanding of cassandra metrics
Posted by Chris Lohfink <cl...@gmail.com>.
The coordinator read/scan (Scan is just different naming for the Range, so
coordinator view of RangeLatency) is the latencies from the coordinator
perspective, so it includes network latency between replicas and such. This
which is actually added for speculative retry (why there is no
coordinatorWriteLatency). Only the CoordinatorReadLatency is used for it
however.
The Read/RangeLatency metrics are for local reads, basically just how long
to read from disk and merge with sstables.
The View* metrics are only relevant to materialized views. There actually
is a partition lock for updates which ViewLockAcquireTime gives visibility
too. Also there are sometimes reads required for updating materialized
views, which ViewReadTime is for tracking. For more details id recommend
https://opencredo.com/everything-need-know-cassandra-materialized-views/
Chris
On Fri, Jul 7, 2017 at 9:42 AM, ZAIDI, ASAD A <az...@att.com> wrote:
> What exactly does mean CoordinatorScanLatency for example
>
> CoordinatorScanLatency is a timer metric that present coordinator range
> scan latency for table.
>
> Is it latency on full table scan or maybe range scan by clustering key?
>
> It is range scan.. clustering key is used to only store
> data in sorted fashion – partition key along with chosen partitioner helps
> in range scan of data.
>
> Can anybody write into partition while locked?
>
> Writes are atomic – it depends on your chosen consistency
> level to determine if writes will fail or succeed.
>
>
>
> *From:* Павел Сапежко [mailto:amelius0712@gmail.com]
> *Sent:* Friday, July 07, 2017 8:23 AM
> *To:* user@cassandra.apache.org
> *Subject:* Re: Understanding of cassandra metrics
>
>
>
> Are you really think that I don't read docs? Do you have enough
> information in the documentation? I think no. What exactly does mean CoordinatorScanLatency
> for example? Is it latency on full table scan or maybe range scan by
> clustering key? What exactly mean ViewLockAcquireTime? What is "partition
> lock"? Can anybody write into partition while locked? Etc.
>
> пт, 7 июл. 2017 г. в 13:01, Ivan Iliev <iv...@gmail.com>:
>
> 1st result on google returns:
>
>
>
> http://cassandra.apache.org/doc/latest/operating/metrics.html
> <https://urldefense.proofpoint.com/v2/url?u=http-3A__cassandra.apache.org_doc_latest_operating_metrics.html&d=DwMFaQ&c=LFYZ-o9_HUMeMTSQicvjIg&r=FsmDztdsVuIKml8IDhdHdg&m=xLXSLhev337PLD18_DQUB610StqO2URoRumDH-UXdtk&s=xTDUr1_OtTvWNi15F4GNSYs6lzQHi-2wX7oa2T37RCY&e=>
>
>
>
> On Fri, Jul 7, 2017 at 12:16 PM, Павел Сапежко <am...@gmail.com>
> wrote:
>
> Hello, I have several question about cassandra metrics. What does exactly
> mean the next metrics:
>
> - CoordinatorReadLatency
> - CoordinatorScanLatency
> - ReadLatency
> - RangeLatency
> - ViewLockAcquireTime
> - ViewReadTime
>
> --
>
> С уважением,
>
> Павел Сапежко
>
> skype: p.sapezhko
>
>
>
> --
>
> С уважением,
>
> Павел Сапежко
>
> skype: p.sapezhko
>