The shutdown sequence sometimes gets stuck after the thread's interrupted flag getting cleared within the drools application logic, or by a generic Throwable catch. Here is the stack trace using the 1.0.0 open source release.

"qtp111156771-19" #19 prio=5 os_prio=0 tid=0x00007f7444039800 nid=0x42d2 in Object.wait() [0x00007f743fffc000]
java.lang.Thread.State: WAITING (on object monitor)
at java.lang.Object.wait(Native Method)

waiting on <0x000000076c8ac830> (a org.openecomp.policy.drools.core.PolicySession$1)
at java.lang.Thread.join(Thread.java:1249)

locked <0x000000076c8ac830> (a org.openecomp.policy.drools.core.PolicySession$1)
at java.lang.Thread.join(Thread.java:1323)
at org.openecomp.policy.drools.core.PolicySession.stopThread(PolicySession.java:188)

locked <0x000000076c8a6590> (a org.openecomp.policy.drools.core.PolicySession)
at org.openecomp.policy.drools.core.PolicyContainer.stop(PolicyContainer.java:603)

locked <0x00000006c5260c78> (a org.openecomp.policy.drools.core.PolicyContainer)
at org.openecomp.policy.drools.controller.internal.MavenDroolsController.stop(MavenDroolsController.java:409)
at org.openecomp.policy.drools.system.internal.AggregatedPolicyController.stop(AggregatedPolicyController.java:286)
at org.openecomp.policy.drools.system.internal.AggregatedPolicyController.shutdown(AggregatedPolicyController.java:298)
at org.openecomp.policy.drools.system.IndexedPolicyControllerFactory.shutdown(PolicyControllerFactory.java:313)
at org.openecomp.policy.drools.system.PolicyEngineManager.shutdown(PolicyEngine.java:759)