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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:
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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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