Re: [rules-dev] Deadlock in the Drools core - Drools 5.0 - any suggestions for resolution?

From: Edward Archibald <edward.archibald(a)continuent.com&gt; Subject: [rules-dev] Deadlock in the Drools core - Drools 5.0 - any suggestions for resolution? To: &quot;rules-dev(a)lists.jboss.org&quot; <rules-dev(a)lists.jboss.org&gt; Date: Tuesday, November 3, 2009, 9:41 PM I found the following deadlock which is, apparently, due to the concurrent execution of a task for a 'delayed' rule with a concurrently executing application thread attempting to get access to a 'global'.  Any recommendations for avoiding this type of deadlock besides not using rules with 'duration()' etc. which cause asynchronous execution with respect to my main application thread? This problem is somewhat difficult to reproduce on demand but it does come up frequently when the 'delayed' rule "DETECT MONITORING HAS STOPPED" is activated as a result of the trigger conditions. =================================================================================== This thread, my application's EnterprisePolicyManager thread, is attempting to get access to a global, policyMgr, and is waiting for the 'lock.lock' on RetooStatefulSession It owns the 'ReteooStatefulSession.actionQueue' and is waiting for the ReteooStatefulSession.lock.lock owns: java.util.LinkedList<E>  (id=207) waited by: Thread [pool-3-thread-1] (Suspended) owns: com.continuent.tungsten.cluster.manager.rules.engine.RulesEngine  (id=208) sun.misc.Unsafe.park(boolean, long) line: not available [native method] [local variables unavailable] java.util.concurrent.locks.LockSupport.park() line: 118 [local variables unavailable] java.util.concurrent.locks.AbstractQueuedSynchronizer.parkAndCheckInterrupt() line: 681 [local variables unavailable] java.util.concurrent.locks.ReentrantLock$NonfairSync(java.util.concurrent.locks.AbstractQueuedSynchronizer).acquireQueued(java.util.concurrent.locks.AbstractQueuedSynchronizer$Node, int) line: 711 java.util.concurrent.locks.ReentrantLock$NonfairSync(java.util.concurrent.locks.AbstractQueuedSynchronizer).acquire(int) line: 1041 java.util.concurrent.locks.ReentrantLock$NonfairSync.lock() line: 184 [local variables unavailable] java.util.concurrent.locks.ReentrantLock.lock() line: 256 [local variables unavailable] org.drools.reteoo.ReteooStatefulSession(org.drools.common.AbstractWorkingMemory).getGlobal(java.lang.String) line: 587 com.continuent.tungsten.cluster.manager.policy.Rule_IF_IN_MAINTENANCE_MODE__CONSUME_ALL_NOTIFICATIONS_0Eval0Invoker.evaluate(org.drools.spi.Tuple, org.drools.rule.Declaration[], org.drools.WorkingMemory, java.lang.Object) line: not available org.drools.rule.EvalCondition.isAllowed(org.drools.spi.Tuple, org.drools.WorkingMemory, java.lang.Object) line: 117 org.drools.reteoo.EvalConditionNode.assertLeftTuple(org.drools.reteoo.LeftTuple, org.drools.spi.PropagationContext, org.drools.common.InternalWorkingMemory) line: 180 org.drools.reteoo.SingleLeftTupleSinkAdapter.doPropagateAssertLeftTuple(org.drools.spi.PropagationContext, org.drools.common.InternalWorkingMemory, org.drools.reteoo.LeftTuple) line: 117 org.drools.reteoo.SingleLeftTupleSinkAdapter.propagateAssertLeftTuple(org.drools.reteoo.LeftTuple, org.drools.reteoo.RightTuple, org.drools.spi.PropagationContext, org.drools.common.InternalWorkingMemory, boolean) line: 28 org.drools.reteoo.JoinNode.assertObject(org.drools.common.InternalFactHandle, org.drools.spi.PropagationContext, org.drools.common.InternalWorkingMemory) line: 175 org.drools.reteoo.SingleObjectSinkAdapter.propagateAssertObject(org.drools.common.InternalFactHandle, org.drools.spi.PropagationContext, org.drools.common.InternalWorkingMemory) line: 42 org.drools.reteoo.PropagationQueuingNode$AssertAction.execute(org.drools.reteoo.ObjectSinkPropagator, org.drools.common.InternalWorkingMemory) line: 326 org.drools.reteoo.PropagationQueuingNode.propagateActions(org.drools.common.InternalWorkingMemory) line: 221 org.drools.reteoo.PropagationQueuingNode$PropagateAction.execute(org.drools.common.InternalWorkingMemory) line: 394 org.drools.reteoo.ReteooStatefulSession(org.drools.common.AbstractWorkingMemory).executeQueuedActions() line: 1486 org.drools.common.NamedEntryPoint.insert(org.drools.common.InternalFactHandle, java.lang.Object, org.drools.rule.Rule, org.drools.spi.Activation) line: 158 org.drools.common.NamedEntryPoint.insert(java.lang.Object, boolean, boolean, org.drools.rule.Rule, org.drools.spi.Activation) line: 122 org.drools.common.NamedEntryPoint.insert(java.lang.Object) line: 80 com.continuent.tungsten.cluster.manager.rules.engine.RulesEngine.insertFact(com.continuent.tungsten.commons.cluster.resource.notification.NotificationStreamID, java.lang.Object, boolean) line: 162 com.continuent.tungsten.cluster.manager.policy.EnterprisePolicyManager.run() line: 249 java.lang.Thread.run() line: 595 The rule implicated in the above thread is: rule "IF IN MAINTENANCE MODE, CONSUME ALL NOTIFICATIONS" salience 999   when     notification : ClusterResourceNotification() from entry-point "MONITORING"     eval(policyMgr.getMode() == ClusterPolicyManagerMode.MAINTENANCE)   then      statistics.increment("IF IN MAINTENANCE MODE, CONSUME ALL NOTIFICATIONS");     retract(notification); end This other thread, apparently a scheduled thread for a rule with a 10 second duration, is attempting to insert a fact and owns the 'lock.lock' on ReteooStatefulSession and is waiting for the 'ReteooStatefulSession.actionQueue'. owns: org.drools.common.DefaultAgenda  (id=4046) waiting for: java.util.LinkedList<E>  (id=207) org.drools.reteoo.ReteooStatefulSession(org.drools.common.AbstractWorkingMemory).executeQueuedActions() line: 1480 org.drools.reteoo.ReteooStatefulSession(org.drools.common.AbstractWorkingMemory).insert(org.drools.common.InternalFactHandle, java.lang.Object, org.drools.rule.Rule, org.drools.spi.Activation, org.drools.reteoo.ObjectTypeConf) line: 1051 org.drools.reteoo.ReteooStatefulSession(org.drools.common.AbstractWorkingMemory).insert(java.lang.Object, boolean, boolean, org.drools.rule.Rule, org.drools.spi.Activation) line: 1001 org.drools.base.DefaultKnowledgeHelper.insert(java.lang.Object, boolean) line: 114 org.drools.base.DefaultKnowledgeHelper.insert(java.lang.Object) line: 108 com.continuent.tungsten.cluster.manager.policy.Rule_DETECT_MONITORING_HAS_STOPPED_0.consequence(org.drools.spi.KnowledgeHelper, com.continuent.tungsten.commons.cluster.resource.notification.DataServerNotification, org.drools.FactHandle, java.lang.String, org.drools.FactHandle, com.continuent.tungsten.cluster.manager.policy.EnterprisePolicyManager, org.apache.log4j.Logger) line: not available com.continuent.tungsten.cluster.manager.policy.Rule_DETECT_MONITORING_HAS_STOPPED_0ConsequenceInvoker.evaluate(org.drools.spi.KnowledgeHelper, org.drools.WorkingMemory) line: not available org.drools.common.DefaultAgenda.fireActivation(org.drools.spi.Activation) line: 934 org.drools.common.Scheduler$DuractionJob.execute(org.drools.time.JobContext) line: 70 org.drools.time.impl.JDKTimerService$JDKCallableJob.call() line: 132 org.drools.time.impl.JDKTimerService$JDKCallableJob.call() line: 110 java.util.concurrent.FutureTask$Sync.innerRun() line: 269 java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask<V>(java.util.concurrent.FutureTask<V>).run() line: 123 java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask<V>.access$301(java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask) line: 65 java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask<V>.run() line: 168 java.util.concurrent.ThreadPoolExecutor$Worker.runTask(java.lang.Runnable) line: 650 java.util.concurrent.ThreadPoolExecutor$Worker.run() line: 675 java.lang.Thread.run() line: 595 The rule for this task looks like: rule "DETECT MONITORING HAS STOPPED" duration(10s) salience 1000   when     lastNotification : DataServerNotification($resourceName : resourceName)                   from entry-point "MONITORING"     not (DataServerNotification(resourceName == $resourceName,                                  this after [10s] lastNotification)                   from entry-point "MONITORING")         not (ManagerFailedAlarm(expired == false,                    resourceName == $resourceName))     not (DataSource(name == $resourceName,                    state == ResourceState.SHUNNED ||                    state == ResourceState.FAILED))   then     Object[] params = {$resourceName};     if (policyMgr.getMode() != ClusterPolicyManagerMode.MAINTENANCE)     {       lastNotification.setResourceState(ResourceState.UNKNOWN);       ManagerFailedAlarm alarm =                         new ManagerFailedAlarm(lastNotification, "rule detected monitor stop",                                  6, AlarmSeverity.FAULT);       logger.info(alarm.toString());       insert(alarm);       update(lastNotification);      } end _______________________________________________ rules-dev mailing list rules-dev(a)lists.jboss.org https://lists.jboss.org/mailman/listinfo/rules-dev