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https://issues.apache.org/jira/browse/HBASE-21440?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16680638#comment-16680638
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Josh Elser commented on HBASE-21440:
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Oh, one more tidbit of information from the environment which we saw this one:
The region in question that was "orphaned" was {{hbase:namespace}}. Thus,
putting us in a pickle as the Master would eventually take a nose-dive any time
it was started. Because we got the wires crossed (SCP saw the AP running,
called the remoteCallFailed which put the AP back on the queue, but its state
was already OPEN on the dead server, then the re-run of the AP did nothing),
that left us in this state where user-intervention was required.
> Assign procedure on the crashed server is not properly interrupted
> ------------------------------------------------------------------
>
> Key: HBASE-21440
> URL: https://issues.apache.org/jira/browse/HBASE-21440
> Project: HBase
> Issue Type: Bug
> Affects Versions: 2.0.2
> Reporter: Ankit Singhal
> Assignee: Ankit Singhal
> Priority: Major
> Attachments: HBASE-21440.branch-2.0.001.patch,
> HBASE-21440.branch-2.0.002.patch
>
>
> When the server crashes, it's SCP checks if there is already a procedure
> assigning the region on this crashed server. If we found one, SCP will just
> interrupt the already running AssignProcedure by calling remoteCallFailed
> which internally just changes the region node state to OFFLINE and send the
> procedure back with transition queue state for assignment with a new plan.
> But, due to the race condition between the calling of the remoteCallFailed
> and current state of the already running assign
> procedure(REGION_TRANSITION_FINISH: where the region is already opened), it
> is possible that assign procedure goes ahead in updating the regionStateNode
> to OPEN on a crashed server.
> As SCP had already skipped this region for assignment as it was relying on
> existing assign procedure to do the right thing, this whole confusion leads
> region to a not accessible state.
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