[jira] [Commented] (CASSANDRA-5947) Sampling bug in metrics-core-2.0.3.jar used by Cassandra

["Chris Burroughs (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/CASSANDRA-5947?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13759169#comment-13759169 ] 

Chris Burroughs commented on CASSANDRA-5947:
--------------------------------------------

Obligatory "you forget to update build.xml".

One thing that might be worth noting is that this introduces annoying "quoting" in jconsole https://github.com/codahale/metrics/commit/e2336060816ad339676c0e162359c17381ded99f  so it's

{noformat}
"org.apache.cassandra.metrics"
{noformat}

instead of 

{noformat}
org.apache.cassandra.metrics
{noformat}

But unless there is some JMX voodoo I'm missing I think that's just a cosmetic issue.  cc [~yukim]
                
> 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
>
>
> 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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