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https://issues.apache.org/jira/browse/CASSANDRA-11752?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Per Otterström updated CASSANDRA-11752:
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Attachment: server-patch-v2.png
11752-2.2-v2.txt
I've executed a few tests on this and I'm not able to see any performance
impact caused by the exclusive lock every 30 minutes. In my opinion there is no
reason to implement a buffer solution.
Attaching a graph which show 50th percentile, 99,9th percentile and max. The
result is somewhat edgy since we are using buckets, but the graph is consistent
before and after rescale. The notable exception is of course the max value
which will dip a lot every time, but that is kind of expected when we are using
forward decay.
Also attaching an update of the patch which should make the graph somewhat more
smooth and responsive as the weight is calculated for each metric. Improved
documentation.
> histograms/metrics in 2.2 do not appear recency biased
> ------------------------------------------------------
>
> Key: CASSANDRA-11752
> URL: https://issues.apache.org/jira/browse/CASSANDRA-11752
> Project: Cassandra
> Issue Type: Bug
> Components: Core
> Reporter: Chris Burroughs
> Assignee: Per Otterström
> Labels: metrics
> Fix For: 2.2.8
>
> Attachments: 11752-2.2-v2.txt, 11752-2.2.txt, boost-metrics.png,
> c-jconsole-comparison.png, c-metrics.png, default-histogram.png,
> server-patch-v2.png
>
>
> In addition to upgrading to metrics3, CASSANDRA-5657 switched to using a
> custom histogram implementation. After upgrading to Cassandra 2.2
> histograms/timer metrics are not suspiciously flat. To be useful for
> graphing and alerting metrics need to be biased towards recent events.
> I have attached images that I think illustrate this.
> * The first two are a comparison between latency observed by a C* 2.2 (us)
> cluster shoring very flat lines and a client (using metrics 2.2.0, ms)
> showing server performance problems. We can't rule out with total certainty
> that something else isn't the cause (that's why we measure from both the
> client & server) but they very rarely disagree.
> * The 3rd image compares jconsole viewing of metrics on a 2.2 and 2.1
> cluster over several minutes. Not a single digit changed on the 2.2 cluster.
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