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https://issues.apache.org/jira/browse/HBASE-20634?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16494524#comment-16494524
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Duo Zhang commented on HBASE-20634:
-----------------------------------
Add a SERVER_CRASH_HANDLE_RIT2 state can not solve the problem, even if we do
not hold the region lock on MoveRegionProcedure. It is possible that the
MoveRegionProcedure is created but never scheduled. And after we execute
SERVER_CRASH_HANDLE_RIT2 the UnassignProcedure is scheduled and then stuck...
I think if we can not add a task to a given RS, then it means the RS is already
dead, then we should finish the procedure. The problem is that whether we
should fail the procedure. For example, for a MoveRegionProcedure, if the
unassign and assign are both failed because of the region is not online, then
what should we do? If it is used for reopening a region then it seems OK as the
region has been reopened, but if it is used for moving a region...
> 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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