[
https://issues.apache.org/jira/browse/HBASE-20846?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16533165#comment-16533165
]
Allan Yang commented on HBASE-20846:
------------------------------------
{quote}
I do not think we go to the correct direction...
In this case, the correct way is to make the parent procedure hold the shared
lock before executing its sub procedures when restarting.
{quote}
But, the problem is, we don't record the shared lock anywhere, when executing,
we don't know whether my parent has already acquire the shared lock or not.
> Table's shared lock is not held by sub-procedures after master restart
> ----------------------------------------------------------------------
>
> Key: HBASE-20846
> URL: https://issues.apache.org/jira/browse/HBASE-20846
> Project: HBase
> Issue Type: Bug
> Affects Versions: 2.1.0
> Reporter: Allan Yang
> Assignee: Allan Yang
> Priority: Major
> Fix For: 3.0.0, 2.0.2, 2.1.1
>
> Attachments: HBASE-20846.branch-2.0.002.patch,
> HBASE-20846.branch-2.0.patch
>
>
> Found this one when investigating ModifyTableProcedure got stuck while there
> was a MoveRegionProcedure going on after master restart.
> Though this issue can be solved by HBASE-20752. But I discovered something
> else.
> Before a MoveRegionProcedure can execute, it will hold the table's shared
> lock. so,, when a UnassignProcedure was spwaned, it will not check the
> table's shared lock since it is sure that its parent(MoveRegionProcedure) has
> aquired the table's lock.
> {code:java}
> // If there is parent procedure, it would have already taken xlock, so no
> need to take
> // shared lock here. Otherwise, take shared lock.
> if (!procedure.hasParent()
> && waitTableQueueSharedLock(procedure, table) == null) {
> return true;
> }
> {code}
> But, it is not the case when Master was restarted. The child
> procedure(UnassignProcedure) will be executed first after restart. Though it
> has a parent(MoveRegionProcedure), but apprently the parent didn't hold the
> table's lock.
> So, since it began to execute without hold the table's shared lock. A
> ModifyTableProcedure can aquire the table's exclusive lock and execute at the
> same time. Which is not possible if the master was not restarted.
> This will cause a stuck before HBASE-20752. But since HBASE-20752 has fixed,
> I wrote a simple UT to repo this case.
> I think we don't have to check the parent for table's shared lock. It is a
> shared lock, right? I think we can acquire it every time we need it.
--
This message was sent by Atlassian JIRA
(v7.6.3#76005)
