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From "Chris Lohfink (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-8331) Expose rate of change of values in histograms
Date Tue, 18 Nov 2014 02:31:33 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-8331?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14215636#comment-14215636
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Chris Lohfink commented on CASSANDRA-8331:
------------------------------------------

I will be willing to give a shot at a patch for exposing Sum or adding a meter to a few choice
histograms if its a good idea.

> Expose rate of change of values in histograms
> ---------------------------------------------
>
>                 Key: CASSANDRA-8331
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-8331
>             Project: Cassandra
>          Issue Type: Improvement
>          Components: Core
>            Reporter: Chris Lohfink
>            Priority: Minor
>              Labels: metrics
>
> In the Metrics JMX Histograms, Sum has value for systems that want to get derivatives
of the data to find rates of change.  Particularly if the timing of collection is not perfect.
 The meters give some perspective to the rate of which things occur but not of the values
themselves.  This could be opened up in metrics but its been shot down:
> https://github.com/dropwizard/metrics/pull/304
> I think theres still value in this. He does have point on distribution of data within
the period, but in small windows with not very extreme values (ie sstables per read per second)
I think its moot.  
> Alternatively we can provide Meters for each of the histograms to use its implementation
of a exponentially weighted moving average to get this value.



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