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From "Ravi Prasad (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (CASSANDRA-5947) Sampling bug in metrics-core-2.0.3.jar used by Cassandra
Date Tue, 10 Sep 2013 21:33:52 GMT

     [ https://issues.apache.org/jira/browse/CASSANDRA-5947?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Ravi Prasad updated CASSANDRA-5947:
-----------------------------------

    Attachment: Screen Shot 2013-09-10 at 2.23.11 PM.png

Screenshot of jconsole showing double quoted object names only for org.apache.cassandra.metrics
yammer metrics in cassandra-1.2.10(latest cassandra-1.2 branch) with metrics-core-2.2.0.jar
                
> Sampling bug in metrics-core-2.0.3.jar used by Cassandra
> --------------------------------------------------------
>
>                 Key: CASSANDRA-5947
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-5947
>             Project: Cassandra
>          Issue Type: Bug
>          Components: Tools
>            Reporter: J.B. Langston
>            Assignee: Jonathan Ellis
>            Priority: Minor
>             Fix For: 1.2.10, 2.0.1
>
>         Attachments: Screen Shot 2013-09-10 at 2.23.11 PM.png
>
>
> There is a sampling bug in the version of the metrics library we're using in Cassandra.
See https://github.com/codahale/metrics/issues/421. ExponentiallyDecayingSample is used by
the Timer's histogram that is used in stress tool, and according to [~brandon.williams] it
is also in a few other places like the dynamic snitch. The statistical theory involved in
this bug goes over my head so i'm not sure if this would bug would meaningfully affect its
usage by Cassandra.  One of the comments on the bug mentions that it affects slow sampling
rates (10 samples/min was the example given).  We're currently distributing metrics-core-2.0.3.jar
and according to the release nodes, this bug is fixed in 2.1.3: http://metrics.codahale.com/about/release-notes/#v2-1-3-aug-06-2012

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