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Date: Thu, 12 May 2016 14:31:12 +0000 (UTC)
From: "Chris Lohfink (JIRA)" <jira@apache.org>
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Subject: [jira] [Commented] (CASSANDRA-11752) histograms/metrics in 2.2 do
 not appear recency biased
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archived-at: Thu, 12 May 2016 14:31:15 -0000


    [ https://issues.apache.org/jira/browse/CASSANDRA-11752?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15281556#comment-15281556 ] 

Chris Lohfink commented on CASSANDRA-11752:
-------------------------------------------

You thinking keeping a snapshot of histogram around from 5 min ago or something and compute the percentile attributes from that instead of the total one? I think that would be pretty good approach

> 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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