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https://issues.apache.org/jira/browse/FLINK-15687?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17133053#comment-17133053
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Xintong Song commented on FLINK-15687:
--------------------------------------

[~trohrmann],

Indeed, {{JobTable}} should also be accessed on the RPC main thread.

To guarantee that, we can add the {{MainThreadExecutable}} of the 
{{TaskExecutor}} as an argument of 
{{TaskSubmissionTestEnvironment#registerJobMasterConnection}}.

The method is called in:
* the constructor of {{TaskSubmissionTestEnvironment}}
* 
{{TaskExecutorPartitionLifecycleTest#testJobMasterConnectionTerminationAfterExternalReleaseOrPromotion}}

For both above, the {{MainThreadExecutable}} can be retrieved via 
{{TestingTaskExecutor#getMainThreadExecutableForTesting}}.

I'll try to provide a fix.

BTW, I think the concurrent access to {{JobTable}} exist before the changes of 
this ticket.

> Potential test instabilities due to concurrent access to TaskSlotTable.
> -----------------------------------------------------------------------
>
>                 Key: FLINK-15687
>                 URL: https://issues.apache.org/jira/browse/FLINK-15687
>             Project: Flink
>          Issue Type: Task
>          Components: Runtime / Coordination, Tests
>    Affects Versions: 1.10.0
>            Reporter: Kostas Kloudas
>            Assignee: Xintong Song
>            Priority: Critical
>              Labels: pull-request-available, test-stability
>             Fix For: 1.11.0
>
>
> Working on [FLINK-14742|https://issues.apache.org/jira/browse/FLINK-14742] 
> revealed that the problem with that test instability was the modification of 
> the {{taskSlotTable}} of the {{TaskManager}} under test from multiple 
> threads, namely the test thread and the main thread of the {{rpcEnpoint}}. 
> This data-structure is not thread-safe and this should not happen.
> This anti-pattern seems to be repeated in multiple tests like most of the 
> tests in the {{TaskExecutorSubmissionTest}} (look for the call to the 
> {{TaskSlotTable.allocateSlot()}}). There we seem to call 
> {{taskSlotTable.allocateSlot()}} and then \{{tmGateway.submitTask()}} which 
> is essentially accessing the slot table from within the main rpc-endpoint 
> thread.
> This JIRA is just to investigate if this is also a problem in those tests or 
> not.
> cc [~trohrmann], [~chesnay] , [~yangwang166]



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