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https://issues.apache.org/jira/browse/HBASE-16994?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15631044#comment-15631044
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binlijin commented on HBASE-16994:
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I am sorry to find HBASE-16721 later, and HBASE-16721 already addresses this
problem in branch-1, and as Enis Soztutar described the master version do not
have this problem.
> Region report a last flushed sequence id that is less than the previous last
> flushed sequence id
> -------------------------------------------------------------------------------------------------
>
> Key: HBASE-16994
> URL: https://issues.apache.org/jira/browse/HBASE-16994
> Project: HBase
> Issue Type: Bug
> Reporter: binlijin
> Attachments: HBASE-16994_master_v1.patch, HBASE-16994_master_v2.patch
>
>
> Since append will be published to RingBuffer and handled asynchronously, it's
> possible that one append (say append-X) of the region handled by
> RingBufferEventHandler between startCacheFlush and getNextSequenceId, and
> reset FSHLog#oldestUnflushedStoreSequenceIds which we just cleared in
> #startCacheFlush. This might disturb ServerManager#flushedSequenceIdByRegion
> like shown below (assume region-A has two CF: cfA and cfB)
>
> 1. flush-A runs to startCacheFlush and it will flush both cfA and cfB,
> oldestUnflushedStoreSequenceIds of regionA got cleared
> 2. append-X on cfB handled by RingBufferEventHandler,
> oldestUnflushedStoreSequenceIds set to 10, for example
> 3. flush-A runs to getNextSequenceId and returned 11
> 4. ServerManager#flushedSequenceIdByRegion for regionA set to 11
> 5. flush-A finishes
> 6. flush-B starts and only flush cfA, getNextSequenceId returned 10, and
> flushedSeqId will return 9, and cause warning in ServerManager
> Since this append-X will also got flushed, we should clear the
> oldestUnflushedStoreSequenceIds again to make sure we won't disturb
> ServerManager#flushedSequenceIdByRegion.
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