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https://issues.apache.org/jira/browse/FLINK-16510?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17057885#comment-17057885
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Maximilian Michels commented on FLINK-16510:
--------------------------------------------
We haven't seen this particular problem after we replaced all graceful
shutdowns with hard exists. However, we've seen task managers freezing. Looks
like this is caused by lack of metaspace (we restrict it to 2GB). The meta
space fills up after many restarts due to lingering threads which hold on to
the classloader.
> Task manager safeguard shutdown may not be reliable
> ---------------------------------------------------
>
> Key: FLINK-16510
> URL: https://issues.apache.org/jira/browse/FLINK-16510
> Project: Flink
> Issue Type: Bug
> Components: Runtime / Task
> Reporter: Maximilian Michels
> Assignee: Maximilian Michels
> Priority: Major
>
> The {{JvmShutdownSafeguard}} does not always succeed but can hang when
> multiple threads attempt to shutdown the JVM. Apparently mixing
> {{System.exit()}} with ShutdownHooks and forcefully terminating the JVM via
> {{Runtime.halt()}} does not play together well:
> {noformat}
> "Jvm Terminator" #22 daemon prio=5 os_prio=0 tid=0x00007fb8e82f2800
> nid=0x5a96 runnable [0x00007fb35cffb000]
> java.lang.Thread.State: RUNNABLE
> at java.lang.Shutdown.$$YJP$$halt0(Native Method)
> at java.lang.Shutdown.halt0(Shutdown.java)
> at java.lang.Shutdown.halt(Shutdown.java:139)
> - locked <0x000000047ed67638> (a java.lang.Shutdown$Lock)
> at java.lang.Runtime.halt(Runtime.java:276)
> at
> org.apache.flink.runtime.util.JvmShutdownSafeguard$DelayedTerminator.run(JvmShutdownSafeguard.java:86)
> at java.lang.Thread.run(Thread.java:748)
> Locked ownable synchronizers:
> - None
> "FlinkCompletableFutureDelayScheduler-thread-1" #18154 daemon prio=5
> os_prio=0 tid=0x00007fb708a7d000 nid=0x5a8a waiting for monitor entry
> [0x00007fb289d49000]
> java.lang.Thread.State: BLOCKED (on object monitor)
> at java.lang.Shutdown.halt(Shutdown.java:139)
> - waiting to lock <0x000000047ed67638> (a java.lang.Shutdown$Lock)
> at java.lang.Shutdown.exit(Shutdown.java:213)
> - locked <0x000000047edb7348> (a java.lang.Class for java.lang.Shutdown)
> at java.lang.Runtime.exit(Runtime.java:110)
> at java.lang.System.exit(System.java:973)
> at
> org.apache.flink.runtime.taskexecutor.TaskManagerRunner.terminateJVM(TaskManagerRunner.java:266)
> at
> org.apache.flink.runtime.taskexecutor.TaskManagerRunner.lambda$onFatalError$1(TaskManagerRunner.java:260)
> at
> org.apache.flink.runtime.taskexecutor.TaskManagerRunner$$Lambda$27464/1464672548.accept(Unknown
> Source)
> at
> java.util.concurrent.CompletableFuture.uniWhenComplete(CompletableFuture.java:774)
> at
> java.util.concurrent.CompletableFuture$UniWhenComplete.tryFire(CompletableFuture.java:750)
> at
> java.util.concurrent.CompletableFuture.postComplete(CompletableFuture.java:488)
> at
> java.util.concurrent.CompletableFuture.completeExceptionally(CompletableFuture.java:1990)
> at
> org.apache.flink.runtime.concurrent.FutureUtils$Timeout.run(FutureUtils.java:943)
> at
> org.apache.flink.runtime.concurrent.DirectExecutorService.execute(DirectExecutorService.java:211)
> at
> org.apache.flink.runtime.concurrent.FutureUtils.lambda$orTimeout$11(FutureUtils.java:361)
> at
> org.apache.flink.runtime.concurrent.FutureUtils$$Lambda$27435/159015392.run(Unknown
> Source)
> at
> java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
> at java.util.concurrent.FutureTask.run(FutureTask.java:266)
> at
> java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$201(ScheduledThreadPoolExecutor.java:180)
> at
> java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:293)
> at
> java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
> at
> java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
> at java.lang.Thread.run(Thread.java:748)
> Locked ownable synchronizers:
> - <0x00000006d5e56bd0> (a
> java.util.concurrent.ThreadPoolExecutor$Worker)
> {noformat}
> Note that under this condition the JVM should terminate but it still hangs.
> Sometimes it quits after several minutes.
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