Re: [wildfly-dev] NPE in finalizer of ThreadPoolExecutor

Hi all, I was investigating this issue which I believed initially to be a JDK bug, but it turns out it's caused by WildFly and I'm not really sure what problems it could cause. The symptom is a NullPointerException being thrown in the "Finalizer" Daemon System Thread, while attempting to shut down a ThreadPoolExecutor: Daemon System Thread [Finalizer] (Suspended (exception NullPointerException)) ThreadPoolExecutor.tryTerminate() line: 694 [local variables unavailable] ThreadPoolExecutor.shutdown() line: 1394 ThreadPoolExecutor.finalize() line: 1477 System$2.invokeFinalize(Object) line: 1267 Finalizer.runFinalizer(JavaLangAccess) line: 98 Finalizer.access$100(Finalizer, JavaLangAccess) line: 34 Finalizer$FinalizerThread.run() line: 210 That line 694 contains this line: (runStateOf(c) == SHUTDOWN && ! workQueue.isEmpty())) // NPE: workQueue==null The "workQueue" is final, and proper checks are in place in the constructor won't allow for it to be initialized with null. So I believe this is merely the "finalizer" being triggered for an instance of ThreadPoolExecutor which was not successfully constructed; indeed if I set a breakpoint on the "throw new IllegalArgumentException()" line of the constructor, this trips on a JMS/HornetQ related stack: Thread [ServerService Thread Pool -- 64] (Suspended (breakpoint at line 1307 in ThreadPoolExecutor)) owns: PostOfficeImpl (id=270) owns: HornetQServerImpl (id=271) owns: JMSServerManagerImpl (id=272) owns: JMSService (id=273) ThreadPoolExecutor.<init>(int, int, long, TimeUnit, BlockingQueue<Runnable>, ThreadFactory, RejectedExecutionHandler) line: 1307 ThreadPoolExecutor.<init>(int, int, long, TimeUnit, BlockingQueue<Runnable>) line: 1195 Executors.newFixedThreadPool(int) line: 89 UUIDGenerator.getHardwareAddress() line: 151 UUIDGenerator.getAddressBytes() line: 263 UUIDGenerator.generateStringUUID() line: 206 PostOfficeImpl.addBinding(Binding) line: 481 HornetQServerImpl.loadJournals() line: 1766 HornetQServerImpl.initialisePart2() line: 1593 HornetQServerImpl.access$1400(HornetQServerImpl) line: 178 HornetQServerImpl$SharedStoreLiveActivation.run() line: 2314 HornetQServerImpl.start() line: 435 JMSServerManagerImpl.start() line: 490 JMSService.doStart(StartContext) line: 155 JMSService.access$000(JMSService, StartContext) line: 60 JMSService$1.run() line: 94 Executors$RunnableAdapter<T>.call() line: 511 FutureTask<V>.run() line: 266 ThreadPoolExecutor.runWorker(ThreadPoolExecutor$Worker) line: 1142 ThreadPoolExecutor$Worker.run() line: 617 JBossThread(Thread).run() line: 745 JBossThread.run() line: 122 This doesn't seem to be a real problem for the finalizer thread as it ignores any RuntimeException, and also not a problem for the Executor so I guess the puzzle is far less exciting than the subject of this email might have made you believe :-) But still it would be nice to avoid constructing an illegal Executor, and I have no idea if this could be a real problem for those UUID Generator services which I see in the stacktrace. In my integration test I was updating versions of libraries and application server to EAP 6.4.0.Alpha, but still using an old "standalone.xml" file. I guess the outdated configuration file might have fooled some validation. Thanks, Sanne _______________________________________________ wildfly-dev mailing list wildfly-dev(a)lists.jboss.org https://lists.jboss.org/mailman/listinfo/wildfly-dev