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From "Chris Lohfink (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-8662) Switch cfhistograms from using yammer metrics in 2.1
Date Wed, 21 Jan 2015 19:22:35 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-8662?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14286105#comment-14286105
] 

Chris Lohfink commented on CASSANDRA-8662:
------------------------------------------

In attached patch the output would be the same, just changing from backing it with the Histogram
to using the EstimatedHistogram (which 2 of the 5 metrics used anyway).

> Switch cfhistograms from using yammer metrics in 2.1
> ----------------------------------------------------
>
>                 Key: CASSANDRA-8662
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-8662
>             Project: Cassandra
>          Issue Type: Improvement
>          Components: Core
>            Reporter: Chris Lohfink
>            Assignee: Chris Lohfink
>             Fix For: 2.1.3
>
>         Attachments: CASSANDRA-8662v1.txt
>
>
> cfhistograms was changed to use the yammer histograms CASSANDRA-5871.  Until CASSANDRA-5657's
change to metrics we shouldn't represent the yammer histogram for latency metrics.  Yammer's
histogram is based on assumption of a normal distribution and is bad at representing the tail
percentiles with skewed distributions.  So revert the change just in the 2.1 branch but leave
it for 3.0.



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