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https://issues.apache.org/jira/browse/HBASE-21480?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16688985#comment-16688985
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Duo Zhang commented on HBASE-21480:
-----------------------------------
Changed the title, let's focus on the most critical problem first. The UT will
hang there, because we hold the exclusive lock for the table all the time when
taking a snapshot, and it prevents the SCP to bring the regions online, which
causes a dead lock.
I think we can first acquire the exclusive lock, to let the previous
merge/split procedures to finish, and then change to acquire a shared lock, to
prevent other operations on the table, such as ModifyTableProcedure or
DisableTableProcedure. And for merge/split procedures, we first check if there
is a snapshot operation on going, if so, we give up and rollback.
> Taking snapshot when RS crashes may hang
> ----------------------------------------
>
> Key: HBASE-21480
> URL: https://issues.apache.org/jira/browse/HBASE-21480
> Project: HBase
> Issue Type: Improvement
> Components: snapshots
> Reporter: Duo Zhang
> Priority: Major
> Fix For: 3.0.0, 2.2.0
>
> Attachments: HBASE-21480-UT.patch
>
>
> The current implementation is not good enough. It will take the exclusive
> lock all the time which could hurt the availability, as we need to hold the
> shared lock when assigning regions.
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