Hi , I was using Chaos Monkey to test Flink's behavior against frequent killing of task manager nodes. I found that stopped/disposed StreamTask got retained by java finalizer. It is kind like a memory leak. Since each StreamTask retains 2.6 MB memory. With 20 kills (and job restarts) for 8-CPU container, there are 2.6 * 20 * 8 MB retained in heap.
[image: Inline image 1] finalize() is generally not recommended for cleanup, because "*Finalizers are unpredictable, often dangerous, and generally unnecessary*", quoted from Joshua Bloch's book. http://www.informit.com/articles/article.aspx?p=1216151&seqNum=7 This code from StreamTask.java seems to be the cause. Is it necessary? can it be removed? We are using flink-1.2 release branch. But I see the same code in flink-1.3 and master branch /** * The finalize method shuts down the timer. This is a fail-safe shutdown, in case the original * shutdown method was never called. * * <p> * This should not be relied upon! It will cause shutdown to happen much later than if manual * shutdown is attempted, and cause threads to linger for longer than needed. */ @Override protected void finalize() throws Throwable { super.finalize(); if (timerService != null) { if (!timerService.isTerminated()) { LOG.info("Timer service is shutting down."); timerService.shutdownService(); } } cancelables.close(); } Thanks, Steven
