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https://issues.apache.org/jira/browse/CASSANDRA-12676?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15736166#comment-15736166
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Jay Zhuang commented on CASSANDRA-12676:
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Another reason to disable coalescing is it's blocking small messages after the
cluster running for serveral days:
https://lists.apache.org/thread.html/1439df9cd898ef78c866fa571f28ed1ba4caef889feb1530da941fdb@%3Cuser.cassandra.apache.org%3E
We saw this issue for a few clusters, we cannot consistently reproduce the
problem, as it's happened very randomly and took long time to happen. But after
the coalescing is disabled, we never see such issue.
> Message coalescing regression
> -----------------------------
>
> Key: CASSANDRA-12676
> URL: https://issues.apache.org/jira/browse/CASSANDRA-12676
> Project: Cassandra
> Issue Type: Bug
> Reporter: T Jake Luciani
> Assignee: Jeff Jirsa
> Labels: docs-impacting
> Fix For: 4.0, 3.x
>
> Attachments: 12676.diff, coalescing_disabled.png, result.html
>
>
> The default in 2.2+ was to enable TIMEHORIZON message coalescing. After
> reports of performance regressions after upgrading from 2.1 to 2.2/3.0 we
> have discovered the issue to be this default.
> We need to re-test our assumptions on this feature but in the meantime we
> should default back to disabled.
> Here is a performance run [with and without message
> coalescing|http://cstar.datastax.com/graph?command=one_job&stats=9a26b5f2-7f48-11e6-92e7-0256e416528f&metric=op_rate&operation=2_user&smoothing=1&show_aggregates=true&xmin=0&xmax=508.86&ymin=0&ymax=91223]
>
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