From: Greg Barton <greg_barton(a)yahoo.com&gt; Subject: Re: [rules-users] is this kind of App right for DROOLS? To: "Rules Users List" <rules-users(a)lists.jboss.org&gt; Date: Wednesday, April 15, 2009, 11:26 PM Attached is an simple implementation of what I describe below. I was pleasantly surprised that it ran much faster than I expected, and using less memory. At times in pegged all four cpu cores on my workstation. It's nice to see such effective utilization of resources. (Though I did run it with UseParallelGC, so that may have helped.) The only complaint I have is getting it to stop. :) You've got to kill or ctrl-C to get it to halt. I am calling drools.halt() in a rule that is being executed. Is there another way to exit from fireUntilHalt? The console messages printed by the app show that fireUntilHalt does exit. I noticed on doing a thread dump that a drools thread is blocking after fireUntilHalt exits: Name: Thread-2 State: WAITING on java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject@4c7e8bf0 Total blocked: 0 Total waited: 414 Stack trace: sun.misc.Unsafe.park(Native Method) java.util.concurrent.locks.LockSupport.park(LockSupport.java:158) java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.await(AbstractQueuedSynchronizer.java:1925) java.util.concurrent.LinkedBlockingQueue.take(LinkedBlockingQueue.java:358) org.drools.concurrent.CommandExecutor.run(CommandExecutor.java:77) java.lang.Thread.run(Thread.java:619) CommandExecutor.java line 77 is this: Command executor = ( Command ) this.queue.take(); "queue" is a BlockingQueue, and BlockingQueue.take() will not exit until it returns an object from the queue or it's thread is interrupted. Dev d00ds, is there an official way to interrupt this thread?