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From "Lars Hofhansl (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-11695) PeriodicFlusher and WakeFrequency issues
Date Thu, 07 Aug 2014 22:27:13 GMT

    [ https://issues.apache.org/jira/browse/HBASE-11695?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14089955#comment-14089955
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Lars Hofhansl commented on HBASE-11695:
---------------------------------------

Based on the observation that a 128mb memstore can be send in about 1s across a 1ge link,
maybe the current jitter of 3-23s is good enough. 10-70s still seems a safer bet, but anything
between 5s and 5mins should be OK. :)
I still want adjust the wait-time to be greater than the expected jitter in order to avoid
confusion for folks in the future.


> 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: Minor
>             Fix For: 0.99.0, 2.0.0, 0.94.23, 0.98.6
>
>         Attachments: 11695-trunk.txt
>
>
> 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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