[jira] [Commented] (CASSANDRA-11752) histograms/metrics in 2.2 do not appear recency biased

["T Jake Luciani (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/CASSANDRA-11752?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15364475#comment-15364475 ] 

T Jake Luciani commented on CASSANDRA-11752:
--------------------------------------------

Thanks for the patch [~eperott] 

I'm a little concerned about the impact of the lock every 30 minutes.  Do you think buffering during the period of locking would be possible to not interrupt the active workload?  Where did the 30 minute interval come from? (i.e why not 60) how does the decay look when plotting the quantiles before and after the interval?

I'll try running some stress tests and see if there is any meaningful impact as well as try and generate some charts from reporting live data (unless you have some)


> histograms/metrics in 2.2 do not appear recency biased
> ------------------------------------------------------
>
>                 Key: CASSANDRA-11752
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-11752
>             Project: Cassandra
>          Issue Type: Bug
>          Components: Core
>            Reporter: Chris Burroughs
>            Assignee: Per Otterström
>              Labels: metrics
>             Fix For: 2.2.8
>
>         Attachments: 11752-2.2.txt, boost-metrics.png, c-jconsole-comparison.png, c-metrics.png, default-histogram.png
>
>
> In addition to upgrading to metrics3, CASSANDRA-5657 switched to using  a custom histogram implementation.  After upgrading to Cassandra 2.2 histograms/timer metrics are not suspiciously flat.  To be useful for graphing and alerting metrics need to be biased towards recent events.
> I have attached images that I think illustrate this.
>  * The first two are a comparison between latency observed by a C* 2.2 (us) cluster shoring very flat lines and a client (using metrics 2.2.0, ms) showing server performance problems.  We can't rule out with total certainty that something else isn't the cause (that's why we measure from both the client & server) but they very rarely disagree.
>  * The 3rd image compares jconsole viewing of metrics on a 2.2 and 2.1 cluster over several minutes.  Not a single digit changed on the 2.2 cluster.



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