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From "Chris Burroughs (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-6591) un-deprecate cache recentHitRate and expose in o.a.c.metrics
Date Fri, 17 Jan 2014 17:32:20 GMT

    [ 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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