Hi guys,
I investigate test failures in the Artemis test suite and I see many "Thread leaked" issues. From stack traces It is evident that leaking threads arise from some thread pool and they are waiting for a job. Problem is that I am not able to find which thread pool owns the threads. When the default thread factory is used for creation of a thread, the name and the stack trace of thread looks following.

Thread Thread[pool-4-thread-45,5,main] is still alive with the following 
stackTrace:
sun.misc.Unsafe.park(Native Method)
java.util.concurrent.locks.LockSupport.park(LockSupport.java:175)
java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.await(AbstractQueuedSynchronizer.java:2039)
java.util.concurrent.LinkedBlockingQueue.take(LinkedBlockingQueue.java:442)
java.util.concurrent.ThreadPoolExecutor.getTask(ThreadPoolExecutor.java:1067)
java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1127)
java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
java.lang.Thread.run(Thread.java:745)

I suggest to do not use the Java default thread factory but we should create own default thread factory which will set up name of thread's group in such way that we could find to which thread pool the thread belongs.

I have already created such thread factory and reconfigure all thread pools to use it. You can review my changes in the commit [1]. The default thread factory is implemented in the ActiveMQThreadFactory class [2]. The name and the stack trace of the thread created by this thread factory looks following.

Thread Thread[Thread-0 (org.apache.activemq.artemis.tests.unit.core.paging.impl.PagingStoreImplTest-32863545),5,org.apache.activemq.artemis.tests.unit.core.paging.impl.PagingStoreImplTest-32863545] is still alive with the following stackTrace: sun.misc.Unsafe.park(Native Method) java.util.concurrent.locks.LockSupport.park(LockSupport.java:175) java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.await(AbstractQueuedSynchronizer.java:2039) java.util.concurrent.LinkedBlockingQueue.take(LinkedBlockingQueue.java:442) java.util.concurrent.ThreadPoolExecutor.getTask(ThreadPoolExecutor.java:1067) java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1127) java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617) java.lang.Thread.run(Thread.java:745)

I ran full test suite and it seems that this changes did not break anything. What do you think about it? Would it be possible to merge the commit?

Thank you!

Erich

[1] https://github.com/dudaerich/activemq-artemis/commit/b1e48589acd9c1febd62105cc23fa4c04d673a5b [2] https://github.com/dudaerich/activemq-artemis/blob/b1e48589acd9c1febd62105cc23fa4c04d673a5b/artemis-commons/src/main/java/org/apache/activemq/artemis/utils/ActiveMQThreadFactory.java

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