Looking at this test (“testCheckpointMarkSafety()"), I’m not sure that it’s 
thread-safe to use the same instance of JmsIO.UnboundedJmsReader in another 
thread. Probably, it may cause some race conditions there but seems it happens 
quite rarely.

—
Alexey



> On 5 Oct 2021, at 21:24, JB Onofré <[email protected]> wrote:
> 
> Hi
> 
> I will take a look. That’s probably a race condition with the broker service. 
> 
> Regards 
> JB
> 
>> Le 5 oct. 2021 à 21:21, Miguel Anzo Palomo <[email protected]> a 
>> écrit :
>> 
>> 
>> Hi, I've been working on checking out why is this issue 
>> <https://issues.apache.org/jira/browse/BEAM-8453> happening (flaky test in 
>> JmsIO). The logs in this example 
>> <https://ci-beam.apache.org/job/beam_PreCommit_Java_Commit/18732/testReport/org.apache.beam.sdk.io.jms/JmsIOTest/testCheckpointMarkSafety/>
>>  indicate that the problem is a NullPointerException, specifically in this 
>> receiveNoWait() operation 
>> <https://github.com/apache/beam/blob/9a4cdfba601bae9165928d1a4df8035785b4c871/sdks/java/io/jms/src/main/java/org/apache/beam/sdk/io/jms/JmsIO.java#L503>
>>  at this 
>> <https://github.com/apache/beam/blob/9a4cdfba601bae9165928d1a4df8035785b4c871/sdks/java/io/jms/src/test/java/org/apache/beam/sdk/io/jms/JmsIOTest.java#L386>
>>  line of the test. The only way I see that a NullPointerException is being 
>> caused there, is if the consumer is closed at that point, and the only way I 
>> have been able to reproduce a NullPointerException locally in the lines 
>> mentioned in the log is by closing the consumer before that read operation.
>> 
>> My idea right now is that there could be some intermittency with ActiveMQ 
>> that caused the flaky test at that moment, is there a way to know if that 
>> was the case? Right now I only have two known instances of the flake, this 
>> <https://ci-beam.apache.org/job/beam_PreCommit_Java_Commit/18732/> one on 
>> August 23, and another 
>> <https://ci-beam.apache.org/job/beam_PreCommit_Java_Cron/4447/> one on 
>> September 9 (that jenkins link is no longer available). From what I’ve been 
>> told it is running on the cloud compute instance apache-ci-beam-jenkins.
>> 
>> Thanks
>> 
>> -- 
>> Miguel Angel Anzo Palomo | WIZELINE
>> Software Engineer 
>> [email protected] <mailto:[email protected]>
>> Remote Office
>> 
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