[jira] [Created] (CASSANDRA-11752) histograms/metrics in 2.2 do not appear recency biased

["Chris Burroughs (JIRA)" <ji...@apache.org>]

Chris Burroughs created CASSANDRA-11752:
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             Summary: 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
         Attachments: boost-metrics.png, c-jconsole-comparison.png, c-metrics.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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