skonto commented on a change in pull request #24796: [SPARK-27900][CORE] Add
uncaught exception handler to the driver
URL: https://github.com/apache/spark/pull/24796#discussion_r290532870
##########
File path: core/src/main/scala/org/apache/spark/util/ShutdownHookManager.scala
##########
@@ -204,6 +204,11 @@ private [util] class SparkShutdownHookManager {
hooks.synchronized { hooks.remove(ref) }
}
+ def clear(): Unit = {
Review comment:
@srowen here it is:
https://gist.github.com/skonto/74181e434a727901d4f3323461c1050b
I commented out the clear call. One other (indepedent) thing I noticed is
that the main thread is also stuck here:
https://github.com/apache/spark/blob/bfb3ffe9b33a403a1f3b6f5407d34a477ce62c85/core/src/main/scala/org/apache/spark/scheduler/DAGScheduler.scala#L736
Blocking for ever there might be a problem if something goes wrong.
Now if you check the output:
```
"Thread-1" #10 prio=5 os_prio=0 tid=0x000055d323902000 nid=0x7c in
Object.wait() [0x00007fdccd08a000]
java.lang.Thread.State: WAITING (on object monitor)
at java.lang.Object.wait(Native Method)
at java.lang.Thread.join(Thread.java:1252)
- locked <0x00000000ebe00e50> (a
org.apache.spark.util.EventLoop$$anon$1)
at java.lang.Thread.join(Thread.java:1326)
at org.apache.spark.util.EventLoop.stop(EventLoop.scala:81)
at org.apache.spark.scheduler.DAGScheduler.stop(DAGScheduler.scala:2100)
```
this will never finish and it waits at the join for
`dag-scheduler-event-loop`:
```
"dag-scheduler-event-loop" #45 daemon prio=5 os_prio=0
tid=0x000055d323a25000 nid=0x48 in Object.wait() [0x00007fdccd6d2000]
java.lang.Thread.State: WAITING (on object monitor)
at java.lang.Object.wait(Native Method)
at java.lang.Thread.join(Thread.java:1252)
- locked <0x00000000eb4f3b58> (a
org.apache.hadoop.util.ShutdownHookManager$1)
at java.lang.Thread.join(Thread.java:1326)
at
java.lang.ApplicationShutdownHooks.runHooks(ApplicationShutdownHooks.java:107)
at
java.lang.ApplicationShutdownHooks$1.run(ApplicationShutdownHooks.java:46)
at java.lang.Shutdown.runHooks(Shutdown.java:123)
at java.lang.Shutdown.sequence(Shutdown.java:167)
at java.lang.Shutdown.exit(Shutdown.java:212)
- locked <0x00000000eb3848b8> (a java.lang.Class for java.lang.Shutdown)
at java.lang.Runtime.exit(Runtime.java:109)
at java.lang.System.exit(System.java:971)
at
org.apache.spark.util.SparkUncaughtExceptionHandler.sysExit(SparkUncaughtExceptionHandler.scala:35)
at
org.apache.spark.util.SparkUncaughtExceptionHandler.uncaughtException(SparkUncaughtExceptionHandler.scala:53)
at java.lang.ThreadGroup.uncaughtException(ThreadGroup.java:1057)
at java.lang.ThreadGroup.uncaughtException(ThreadGroup.java:1052)
at java.lang.Thread.dispatchUncaughtException(Thread.java:1959)
```
which waits for the shutodwn hook to finish which is invoked by the oom
which was created by itself. So its a deadlock. If you check the log oom comes
for that thread which tries to submit 1M tasks ;). dag-scheduler-event-loop ->
shutdownHook -> calls join from the other thread and waits for
dag-scheduler-event-loop (deadlock).
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