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https://issues.apache.org/jira/browse/DRILL-6125?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16388572#comment-16388572
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ASF GitHub Bot commented on DRILL-6125:
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Github user ilooner commented on the issue:
https://github.com/apache/drill/pull/1105
@vrozov Thanks for catching this, I believe you are right.
hasClouseoutThread guarantees innerNext and close won't be called concurrently.
However, I still believe innerNext and receivingFragmentFinished could be
called concurrently, since the ControlMessageHandler thread executes
recievingFragmentFinished. Additionally in rare cases where a limit query is
cancelled recievingFragmentFinished and close could be called concurrently as
well. While reflecting on your comments I also saw another issue where the root
could be blocked on a next call but a Finished event would not cause root to
terminate.
In light of all of this I actually think the **synchronized** is not
sufficient. We will have to have some way to interrupt the execution of the
root when we received a finish signal and only close out the resources after
receivingFragmentFinished has been called. Similarly if we receive a finish
signal we should ignore any cancellation requests instead of trying to cancel
and finish simultaneously and vice versa.
I will rework the solution to address these issues and let you know when I
have an update.
> PartitionSenderRootExec can leak memory because close method is not
> synchronized
> --------------------------------------------------------------------------------
>
> Key: DRILL-6125
> URL: https://issues.apache.org/jira/browse/DRILL-6125
> Project: Apache Drill
> Issue Type: Bug
> Affects Versions: 1.13.0
> Reporter: Timothy Farkas
> Assignee: Timothy Farkas
> Priority: Minor
> Fix For: 1.13.0
>
>
> PartitionSenderRootExec creates a PartitionerDecorator and saves it in the
> *partitioner* field. The creation of the partitioner happens in the
> createPartitioner method. This method get's called by the main fragment
> thread. The partitioner field is accessed by the fragment thread during
> normal execution but it can also be accessed by the receivingFragmentFinished
> method which is a callback executed by the event processor thread. Because
> multiple threads can access the partitioner field synchronization is done on
> creation and on when receivingFragmentFinished. However, the close method can
> also be called by the event processor thread, and the close method does not
> synchronize before accessing the partitioner field. Since synchronization is
> not done the event processor thread may have an old reference to the
> partitioner when a query cancellation is done. Since it has an old reference
> the current partitioner can may not be cleared and a memory leak may occur.
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