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https://issues.apache.org/jira/browse/NIFI-1333?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15105509#comment-15105509
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ASF GitHub Bot commented on NIFI-1333:
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Github user olegz commented on the pull request:
https://github.com/apache/nifi/pull/148#issuecomment-172583777
I am not surprised, that's why I was against having a lock in a shutdown in
the first place. It doesn't bring any value since If you follow the logic of
shutting down executors we are shutting them down cold anyway if they have not
shut down in timely fashion.
> FlowController fails to shut down gracefully even though there is nothing
> going on in the flow
> ----------------------------------------------------------------------------------------------
>
> Key: NIFI-1333
> URL: https://issues.apache.org/jira/browse/NIFI-1333
> Project: Apache NiFi
> Issue Type: Bug
> Components: Core Framework
> Affects Versions: 0.4.1
> Reporter: Oleg Zhurakousky
> Assignee: Oleg Zhurakousky
> Priority: Trivial
> Fix For: 0.5.0
>
>
> Basically the following test fails:
> https://github.com/olegz/nifi/blob/int-test/nifi-integration-tests/src/test/java/org/apache/nifi/test/flowcontroll/FlowControllerTests.java#L50
> even though there is no compelling reason for it to fail based on what's in
> the flow.
> Also, the message in logs is confusing . . .
> {code}
> Initiated graceful shutdown of flow controller...waiting up to 10 seconds
> 2015-12-23 15:19:11,977 WARN [main] o.apache.nifi.controller.FlowController
> Controller hasn't terminated properly. There exists an uninterruptable
> thread that will take an indeterminate amount of time to stop. Might need to
> kill the program manually.
> {code}
> What actually happens is deadlock during the shutdown.
> Below are the relevant jstack:
> {code}
> java.lang.Thread.State: TIMED_WAITING (parking)
> at sun.misc.Unsafe.park(Native Method)
> - parking to wait for <0x00000007aeb20988> (a
> java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject)
> at
> java.util.concurrent.locks.LockSupport.parkNanos(LockSupport.java:226)
> at
> java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.awaitNanos(AbstractQueuedSynchronizer.java:2082)
> at
> java.util.concurrent.ThreadPoolExecutor.awaitTermination(ThreadPoolExecutor.java:1468)
> at
> org.apache.nifi.controller.FlowController.shutdown(FlowController.java:1124)
> at org.apache.nifi.test.s2s.SiteToSiteTests.bar(SiteToSiteTests.java:75)
> . . .
> "Framework Task Thread Thread-1" prio=5 tid=0x00007fc8a2064800 nid=0x6a03
> waiting on condition [0x0000700001ded000]
> java.lang.Thread.State: WAITING (parking)
> at sun.misc.Unsafe.park(Native Method)
> - parking to wait for <0x00000007aeb20288> (a
> java.util.concurrent.locks.ReentrantReadWriteLock$NonfairSync)
> at java.util.concurrent.locks.LockSupport.park(LockSupport.java:186)
> at
> java.util.concurrent.locks.AbstractQueuedSynchronizer.parkAndCheckInterrupt(AbstractQueuedSynchronizer.java:834)
> at
> java.util.concurrent.locks.AbstractQueuedSynchronizer.doAcquireShared(AbstractQueuedSynchronizer.java:964)
> at
> java.util.concurrent.locks.AbstractQueuedSynchronizer.acquireShared(AbstractQueuedSynchronizer.java:1282)
> at
> java.util.concurrent.locks.ReentrantReadWriteLock$ReadLock.lock(ReentrantReadWriteLock.java:731)
> at
> org.apache.nifi.controller.FlowController.getRootGroupId(FlowController.java:1262)
> at
> org.apache.nifi.controller.tasks.ExpireFlowFiles.run(ExpireFlowFiles.java:54)
> . . .
> "Timer-Driven Process Thread-1" prio=5 tid=0x00007fc8a3146800 nid=0x6c03
> waiting on condition [0x0000700001ef0000]
> java.lang.Thread.State: WAITING (parking)
> at sun.misc.Unsafe.park(Native Method)
> - parking to wait for <0x00000007aeb20288> (a
> java.util.concurrent.locks.ReentrantReadWriteLock$NonfairSync)
> at java.util.concurrent.locks.LockSupport.park(LockSupport.java:186)
> at
> java.util.concurrent.locks.AbstractQueuedSynchronizer.parkAndCheckInterrupt(AbstractQueuedSynchronizer.java:834)
> at
> java.util.concurrent.locks.AbstractQueuedSynchronizer.doAcquireShared(AbstractQueuedSynchronizer.java:964)
> at
> java.util.concurrent.locks.AbstractQueuedSynchronizer.acquireShared(AbstractQueuedSynchronizer.java:1282)
> at
> java.util.concurrent.locks.ReentrantReadWriteLock$ReadLock.lock(ReentrantReadWriteLock.java:731)
> at
> org.apache.nifi.controller.FlowController.isClustered(FlowController.java:2984)
> at
> org.apache.nifi.controller.FlowController.heartbeat(FlowController.java:3444)
> {code}
> The issue the way I see it is that FlowController's _shutdown_ routine is
> synchronized under the same lock as most of the FlowController callbacks made
> by other threads, hence those threads can't be shutdown since they are in
> dead-lock.
> I don't think there is any reason to synchronize the the shutdown routine
> since all we are trying to do is shut down the very same threads that are
> blocking. Removing synchronization resolves the issue.
> Will submit a patch in a few
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