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Date: Thu, 12 May 2016 14:27:13 +0000 (UTC)
From: "Ariel Weisberg (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 14:27:20 -0000


    [ https://issues.apache.org/jira/browse/CASSANDRA-11752?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15281554#comment-15281554 ] 

Ariel Weisberg commented on CASSANDRA-11752:
--------------------------------------------

It is. My point is that requiring people to munge a histogram to get the a value when you aren't providing an integration for all the different monitoring frameworks is maybe not the best way to go about it.

The values provided by the percentiles are not useful so why not make them useful?

> 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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