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From Per Otterström (JIRA) <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-11752) histograms/metrics in 2.2 do not appear recency biased
Date Mon, 13 Jun 2016 19:36:30 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-11752?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15328026#comment-15328026
] 

Per Otterström commented on CASSANDRA-11752:
--------------------------------------------

Yes, I would like to give it a try.

Had a talk with [~cnlwsu] about it on NGCC. The idea is to create a separate DecayingEH implementation
based on forward decay.

> 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
>              Labels: metrics
>         Attachments: 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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