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https://issues.apache.org/jira/browse/FLINK-29611?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17619810#comment-17619810
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Sopan Phaltankar commented on FLINK-29611:
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[~martijnvisser]
This test depends on the order of iteration in `HashMap.entrySet()` and can
fail for some orders. I am running this on my local machine. I have used a
maven plugin NonDex, which can be used to identify such tests. One can
reproduce it with the command `mvn
edu.illinois:nondex-maven-plugun:1.1.2:nondex
-Dtest=org.apache.flink.streaming.api.operators.co.CoBroadcastWithNonKeyedOperatorTest#testMultiStateSupport`.
Even if the test was not failing during the daily jobs, it'd be good to not
depend on the `HashMap.entrySet()` that gives back results in an undefined
manner
[JavaDoc|[https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html#entrySet--]]
for this. Therefore, to remove non-determinism completely, we can do this
change.
> 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
>
> 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.
> 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.
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