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Date: Fri, 17 Jan 2014 17:32:20 +0000 (UTC)
From: "Chris Burroughs (JIRA)" <jira@apache.org>
To: commits@cassandra.apache.org
Message-ID: <JIRA.12689065.1389813014099.24965.1389979940460@arcas>
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Subject: [jira] [Commented] (CASSANDRA-6591) un-deprecate cache
 recentHitRate and expose in o.a.c.metrics
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    [ https://issues.apache.org/jira/browse/CASSANDRA-6591?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13874981#comment-13874981 ] 

Chris Burroughs commented on CASSANDRA-6591:
--------------------------------------------

By fake events I meant that instead of updating a field each poll could update a meter.  That's "fake" because it's not measuring any real rate of things happening before unit time, just how often we happen to be polling.

I suppose though that that we could use the moving average class from metrics directly, and then expose 1/5/15m averages as guages on CacheMetrics.  Is that preferable?

> un-deprecate cache recentHitRate and expose in o.a.c.metrics
> ------------------------------------------------------------
>
>                 Key: CASSANDRA-6591
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-6591
>             Project: Cassandra
>          Issue Type: Improvement
>          Components: Core
>            Reporter: Chris Burroughs
>            Assignee: Chris Burroughs
>            Priority: Minor
>         Attachments: j6591-1.2-v1.txt, j6591-1.2-v2.txt
>
>
> recentHitRate metrics were not added as part of CASSANDRA-4009 because there is not an obvious way to do it with the Metrics library.  Instead hitRate was added as an all time measurement since node restart.
> This does allow changes in cache rate (aka production performance problems)  to be detected.  Ideally there would be 1/5/15 moving averages for the hit rate, but I'm not sure how to calculate that.  Instead I propose updating recentHitRate on a fixed interval and exposing that as a Gauge.


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