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From "Nicolas Liochon (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-11695) PeriodicFlusher and WakeFrequency issues
Date Thu, 07 Aug 2014 08:56:12 GMT

    [ https://issues.apache.org/jira/browse/HBASE-11695?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14089023#comment-14089023
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Nicolas Liochon commented on HBASE-11695:
-----------------------------------------

When we request a flush, we check that there is not already a request by checking regionsInQueue.
Should we remove the region from regionsInQueue once the flush is done and not just before
doing it?


> PeriodicFlusher and WakeFrequency issues
> ----------------------------------------
>
>                 Key: HBASE-11695
>                 URL: https://issues.apache.org/jira/browse/HBASE-11695
>             Project: HBase
>          Issue Type: Bug
>    Affects Versions: 0.94.21
>            Reporter: Lars Hofhansl
>            Assignee: Lars Hofhansl
>            Priority: Critical
>             Fix For: 0.99.0, 2.0.0, 0.94.23, 0.98.6
>
>
> We just ran into a flush storm caused by the PeriodicFlusher.
> Many memstore became eligible for flushing at exactly the same time, the effect we've
seen is that the exact same region was flushed multiple times, because the flusher wakes up
too often (every 10s). The jitter of 20s is larger than that and it takes some time to actually
flush the memstore.
> Here's one example. We've seen 100's of these, monopolizing the flush queue and preventing
"important" flushes from happening.
> {code}
> 06-Aug-2014 20:11:56  [regionserver60020.periodicFlusher] INFO  org.apache.hadoop.hbase.regionserver.HRegionServer[1397]--
regionserver60020.periodicFlusher requesting flush for region tsdb,\x00\x00\x0AO\xCF* \x00\x00\x01\x00\x01\x1F\x00\x00\x03\x00\x00\x0C,1340147003629.ef4a680b962592de910d0fdeb376dfc2.
after a delay of 13449
> 06-Aug-2014 20:12:06  [regionserver60020.periodicFlusher] INFO  org.apache.hadoop.hbase.regionserver.HRegionServer[1397]--
regionserver60020.periodicFlusher requesting flush for region tsdb,\x00\x00\x0AO\xCF* \x00\x00\x01\x00\x01\x1F\x00\x00\x03\x00\x00\x0C,1340147003629.ef4a680b962592de910d0fdeb376dfc2.
after a delay of 14060
> {code}
> So we need to increase the period of the PeriodicFlusher to at least the random jitter,
also increase the default random jitter (20s does not help with many regions).



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