Hi.
We hit serious PermGen leak when used akka in war/ear application. We used
this pattern for shutting down ActorSystem while destroying application:
actorSystem.shutdown();
actorSystem.awaitTermination();
Redeploying application then caused java.lang.OutOfMemoryError: PermGen
space. Root cause was leaked thread ForkJoinPool-3-worker-3, which
prevented WebappClassLoader from being garbage collected. All dispatcher
threads have been destroyed. After hours of debugging and by elemination we
identified source of this leaked thread. Leak is caused by Remoting#shutdown
method which imports scala.concurrent.ExecutionContext.Implicits.global.
When shutting down remoting, new ForkJoinPool (ForkJoinPool-3) is created
and one thread remains, which holds ClassLoader in field contextClassLoader.
ForkJoinPool-1 and ForkJoinPool-2 were created by default-dispatcher and
default-remote-dispatcher.
Our current workaround is termination callback which is responsible for
shutting down global ExecutionContext. I'm not sure, if this is 100%
working solution (or rather call executorService.shutdown() after
actorSystem.awaitTermination()), but at least leaking thread is no longer
present after shutting down application.
actorSystem.registerOnTermination(new Runnable() {
@Override
public void run() {
ExecutionContextImpl executorImpl = (ExecutionContextImpl)
ExecutionContext.Implicits$.MODULE$.global();
AbstractExecutorService executorService = (AbstractExecutorService)
executorImpl.executor();
executorService.shutdown();
try {
executorService.awaitTermination(10, TimeUnit.SECONDS);
LOGGER.info("Shutting down ExecutionContext.Implicits.global
completed.");
} catch (InterruptedException e) {
LOGGER.error("Shutting down ExecutionContext.Implicits.global
failed.", e);
}
}
});
Is there some reason why is Remoting#shutdown using
scala.concurrent.ExecutionContext.Implicits.global instead of some thread
created by akka (e.g. dispatcher thread)? Who is then responsible for
shutting down global ExecutionContext thread pool?
Thanks
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