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https://issues.apache.org/jira/browse/HBASE-20634?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16494378#comment-16494378
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stack commented on HBASE-20634:
-------------------------------
This is a good one. We've seen it before. In SCP we have a step
SERVER_CRASH_HANDLE_RIT2 that reruns the handleRIT for a case similar to this
where we've managed to assign AFTER SCP has called handleRIT and it has split
logs. What is interesting here is that SCP is locked out because of the
concurrent MoveProcedure's assign which has managed to grab the region lock
first.
> Reopen region while server crash can cause the procedure to be stuck
> --------------------------------------------------------------------
>
> Key: HBASE-20634
> URL: https://issues.apache.org/jira/browse/HBASE-20634
> Project: HBase
> Issue Type: Bug
> Reporter: Duo Zhang
> Assignee: stack
> Priority: Critical
> Fix For: 3.0.0, 2.1.0, 2.0.1
>
> Attachments: HBASE-20634-UT.patch
>
>
> Found this when implementing HBASE-20424, where we will transit the peer sync
> replication state while there is server crash.
> The problem is that, in ServerCrashAssign, we do not have the region lock, so
> it is possible that after we call handleRIT to clear the existing
> assign/unassign procedures related to this rs, and before we schedule the
> assign procedures, it is possible that that we schedule a unassign procedure
> for a region on the crashed rs. This procedure will not receive the
> ServerCrashException, instead, in addToRemoteDispatcher, it will find that it
> can not dispatch the remote call and then a FailedRemoteDispatchException
> will be raised. But we do not treat this exception the same with
> ServerCrashException, instead, we will try to expire the rs. Obviously the rs
> has already been marked as expired, so this is almost a no-op. Then the
> procedure will be stuck there for ever.
> A possible way to fix it is to treat FailedRemoteDispatchException the same
> with ServerCrashException, as it will be created in addToRemoteDispatcher
> only, and the only reason we can not dispatch a remote call is that the rs
> has already been dead. The nodeMap is a ConcurrentMap so I think we could use
> it as a guard.
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