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https://issues.apache.org/jira/browse/FLINK-22085?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17363298#comment-17363298
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Dong Lin commented on FLINK-22085:
----------------------------------
[~xintongsong] No... after spending 2+ hours over the weekend to look into
this, I don't think I will be able to find the answer to this bug any time soon.
Previously I spent considerable (from 4/11 to 4/26) to investigate this bug and
found 2+ issues. I couldn't not find any more Kafka-related bugs by reading the
code and the thread dump. It is not clear from the thread dump where the
deadlock comes from. In order for me to further figure this out, I would need
to have deeper understanding of Flink runtime works by reading the source Flink
code, which I have not had time to do since I joined the current team.
If anyone could help read the threadump from the log and give some idea
regarding why the test deadlocks, I would be happy to continue the
investigation.
> KafkaSourceLegacyITCase hangs/fails on azure
> --------------------------------------------
>
> Key: FLINK-22085
> URL: https://issues.apache.org/jira/browse/FLINK-22085
> Project: Flink
> Issue Type: Bug
> Components: Connectors / Kafka
> Affects Versions: 1.13.0, 1.14.0
> Reporter: Dawid Wysakowicz
> Assignee: Dong Lin
> Priority: Critical
> Labels: pull-request-available, test-stability
> Fix For: 1.14.0
>
>
> 1) Observations
> a) The Azure pipeline would occasionally hang without printing any test error
> information.
> [https://dev.azure.com/apache-flink/apache-flink/_build/results?buildId=15939&view=logs&j=c5f0071e-1851-543e-9a45-9ac140befc32&t=1fb1a56f-e8b5-5a82-00a0-a2db7757b4f5&l=8219]
> b) By running the test KafkaSourceLegacyITCase::testBrokerFailure() with INFO
> level logging, the the test would hang with the following error message
> printed repeatedly:
> {code:java}
> 20451 [New I/O boss #50] ERROR
> org.apache.flink.networking.NetworkFailureHandler [] - Closing communication
> channel because of an exception
> java.net.ConnectException: Connection refused: localhost/127.0.0.1:50073
> at sun.nio.ch.SocketChannelImpl.checkConnect(Native Method)
> ~[?:1.8.0_151]
> at
> sun.nio.ch.SocketChannelImpl.finishConnect(SocketChannelImpl.java:717)
> ~[?:1.8.0_151]
> at
> org.apache.flink.shaded.testutils.org.jboss.netty.channel.socket.nio.NioClientBoss.connect(NioClientBoss.java:152)
> ~[flink-test-utils_2.11-1.13-SNAPSHOT.jar:1.13-SNAPSHOT]
> at
> org.apache.flink.shaded.testutils.org.jboss.netty.channel.socket.nio.NioClientBoss.processSelectedKeys(NioClientBoss.java:105)
> [flink-test-utils_2.11-1.13-SNAPSHOT.jar:1.13-SNAPSHOT]
> at
> org.apache.flink.shaded.testutils.org.jboss.netty.channel.socket.nio.NioClientBoss.process(NioClientBoss.java:79)
> [flink-test-utils_2.11-1.13-SNAPSHOT.jar:1.13-SNAPSHOT]
> at
> org.apache.flink.shaded.testutils.org.jboss.netty.channel.socket.nio.AbstractNioSelector.run(AbstractNioSelector.java:337)
> [flink-test-utils_2.11-1.13-SNAPSHOT.jar:1.13-SNAPSHOT]
> at
> org.apache.flink.shaded.testutils.org.jboss.netty.channel.socket.nio.NioClientBoss.run(NioClientBoss.java:42)
> [flink-test-utils_2.11-1.13-SNAPSHOT.jar:1.13-SNAPSHOT]
> at
> org.apache.flink.shaded.testutils.org.jboss.netty.util.ThreadRenamingRunnable.run(ThreadRenamingRunnable.java:108)
> [flink-test-utils_2.11-1.13-SNAPSHOT.jar:1.13-SNAPSHOT]
> at
> org.apache.flink.shaded.testutils.org.jboss.netty.util.internal.DeadLockProofWorker$1.run(DeadLockProofWorker.java:42)
> [flink-test-utils_2.11-1.13-SNAPSHOT.jar:1.13-SNAPSHOT]
> at
> java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
> [?:1.8.0_151]
> at
> java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
> [?:1.8.0_151]
> at java.lang.Thread.run(Thread.java:748) [?:1.8.0_151]
> {code}
> *2) Root cause explanations*
> The test would hang because it enters the following loop:
> - closeOnFlush() is called for a given channel
> - closeOnFlush() calls channel.write(..)
> - channel.write() triggers the exceptionCaught(...) callback
> - closeOnFlush() is called for the same channel again.
> *3) Solution*
> Update closeOnFlush() so that, if a channel is being closed by this method,
> then closeOnFlush() would not try to write to this channel if it is called on
> this channel again.
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