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https://issues.apache.org/jira/browse/HBASE-21375?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Duo Zhang updated HBASE-21375:
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Description: The problem for the old implementation is that we will only
check the first procedure in a queue to see if it could run, if it can not, we
will remove the queue from run queue. So when adding procedure to the
scheduler, we have to try hard to put the procedure which can be executed in
front of the queue, if there are corner cases where we fail to do so, it will
likely lead to a dead lock, that's why we have the tricky code here, and also
lots of 'if' in the doAdd method of MasterProcedureScheduler. But this is still
not enough to make things right, so finally [~allan163] and I decided to change
the logic in doPoll method, where we use a loop to find whether there is a
procedure can be executed, not only the first one. (was: The problem for the
old implementation is that we will only check the first procedure in a queue to
see if it could run, if it can not, we will remove the queue from run queue. So
when adding procedure to the scheduler, we have to try hard to put the
procedure which can be executed in front of the queue, if there are corner
cases where we fail to do so, it will likely lead to a dead lock, that's why we
have the tricky code here, and also lots of 'if' in the doAdd method of
MasterProcedureScheduler. But this is still not enough to make things right, so
finally Allan and I decided to change the logic in doPoll method, where we use
a loop to find whether there is a procedure can be executed, not only the first
one.)
> Revisit the lock and queue implementation in MasterProcedureScheduler
> ---------------------------------------------------------------------
>
> Key: HBASE-21375
> URL: https://issues.apache.org/jira/browse/HBASE-21375
> Project: HBase
> Issue Type: Sub-task
> Components: proc-v2
> Reporter: Duo Zhang
> Assignee: Duo Zhang
> Priority: Major
> Fix For: 3.0.0, 2.2.0
>
> Attachments: HBASE-21375-UT.patch, HBASE-21375-UT2.patch,
> HBASE-21375-v1.patch, HBASE-21375-v2.patch, HBASE-21375.patch
>
>
> The problem for the old implementation is that we will only check the first
> procedure in a queue to see if it could run, if it can not, we will remove
> the queue from run queue. So when adding procedure to the scheduler, we have
> to try hard to put the procedure which can be executed in front of the queue,
> if there are corner cases where we fail to do so, it will likely lead to a
> dead lock, that's why we have the tricky code here, and also lots of 'if' in
> the doAdd method of MasterProcedureScheduler. But this is still not enough to
> make things right, so finally [~allan163] and I decided to change the logic
> in doPoll method, where we use a loop to find whether there is a procedure
> can be executed, not only the first one.
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