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https://issues.apache.org/jira/browse/FLINK-29611?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17626538#comment-17626538
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Chesnay Schepler commented on FLINK-29611:
------------------------------------------

Sorry but we are busy enough without chasing theoretical test instabilities. 
Closing this issue and PR.

> Fix flaky tests in CoBroadcastWithNonKeyedOperatorTest
> ------------------------------------------------------
>
>                 Key: FLINK-29611
>                 URL: https://issues.apache.org/jira/browse/FLINK-29611
>             Project: Flink
>          Issue Type: Bug
>            Reporter: Sopan Phaltankar
>            Priority: Minor
>              Labels: pull-request-available
>
> The test 
> _org.apache.flink.streaming.api.operators.co.CoBroadcastWithNonKeyedOperatorTest.testMultiStateSupport_
>  has the following failure:
> Failures:
> [ERROR]   CoBroadcastWithNonKeyedOperatorTest.testMultiStateSupport:74 
> Wrong Side Output: arrays first differed at element [0]; expected:<Record @ 
> 15 : 9:key.6->6> but was:<Record @ 15 : 9:key.5->5>
> I used the tool [NonDex|https://github.com/TestingResearchIllinois/NonDex] to 
> find this flaky test. 
> Command: mvn edu.illinois:nondex-maven-plugun:1.1.2:nondex -Dtest='Fully 
> Qualified Test Name'
> I analyzed the assertion failure and found that the root cause is because the 
> test method calls ctx.getBroadcastState(STATE_DESCRIPTOR).immutableEntries() 
> which calls the entrySet() method of the underlying HashMap. entrySet() 
> returns the entries in a non-deterministic way, causing the test to be flaky. 
> The fix would be to change _HashMap_ to _LinkedHashMap_ where the Map is 
> getting initialized.
> On further analysis, it was found that the Map is getting initialized on line 
> 53 of org.apache.flink.runtime.state.HeapBroadcastState class.
> After changing from HashMap to LinkedHashMap, the above test is passing.
> Edit: Upon making this change and running the CI, it was found that the tests 
> org.apache.flink.api.datastream.DataStreamBatchExecutionITCase.batchKeyedBroadcastExecution
>  and 
> org.apache.flink.api.datastream.DataStreamBatchExecutionITCase.batchBroadcastExecution
>  were failing. Upon further investigation, I found that these tests were also 
> flaky and depended on the earlier made change.



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