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From "T Jake Luciani (JIRA)" <>
Subject [jira] [Commented] (CASSANDRA-11752) histograms/metrics in 2.2 do not appear recency biased
Date Wed, 06 Jul 2016 15:38:11 GMT


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:
>             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,
> 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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