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https://issues.apache.org/jira/browse/HBASE-21469?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16687028#comment-16687028
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Josh Elser commented on HBASE-21469:
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Thanks for the ping, Allan!
> Re-visit post* hooks in DDL operations
> --------------------------------------
>
> Key: HBASE-21469
> URL: https://issues.apache.org/jira/browse/HBASE-21469
> Project: HBase
> Issue Type: Bug
> Affects Versions: 2.1.1, 2.0.2
> Reporter: Allan Yang
> Assignee: Allan Yang
> Priority: Major
>
> I have some discuss in HBASE-19953 from
> [here|https://issues.apache.org/jira/browse/HBASE-19953?focusedCommentId=16673126&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-16673126]
> In HBASE-19953,[~elserj] want to make sure that the post* hooks are called
> only when the procedures finish.But it accidentally turns modifytable and
> truncate table request into a sync call, which make clients RPC timeout
> easily on big tables.
> We should re-visit those postxxx hooks in DDL operations, because they are
> now not consistent now:
> For DDLs other than modifytable and truncate table, although the call will
> wait on the latch, the latch is actually released just after prepare state,
> so we still call postxxx hooks before the operation finish.
> For DDLs of modifytable and truncate, the latch is only released after the
> whole procedure finish. So the effort works(but will cause RPC timeout)
> I think these latches are designed for compatibility with 1.x clients. Take
> ModifyTable for example, in 1.x, we use admin.getAlterStauts() to check the
> alter status, but in 2.x, this method is deprecated and returning inaccurate
> result, we have to make 1.x client in a sync wait.
> And for the semantics of postxxx hooks in 1.x, we will call them after the
> corresponding DDL request return, but actually, the DDL request may not
> finished also since we don't want for region assignment.
> So, here, we need to discuss the semantics of postxxx hooks in DDL
> operations, we need to make it consistent in every DDL operations, do we
> really need to make sure this hooks being called only after the operation
> finish? What's more, we have postCompletedxxx hooks for that need.
>
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