FYI: I tested my application with the latest Drools release 5.2.0.Final and I couldn't reproduce the problem described below. It seems that it is solved. Best regards, Wolfgang Von: rules-users-bounces(a)lists.jboss.org [mailto:rules-users-bounces@lists.jboss.org] Im Auftrag von Weiss, Wolfgang Gesendet: Dienstag, 21. Juni 2011 10:19 An: rules-users(a)lists.jboss.org Betreff: [rules-users] NullPointerException in RightTupleIndexHashTable.remove() Hi all! I encountered that null pointer exceptions occur when retracting an object from the working memory. Sometimes the problem occurs sooner sometimes later but it certainly happens. I think it also depends on the workload on the machine. Sometimes the NPE is thrown in 'LeftTupleIndexHashTable' but mainly in 'RightTupleIndexHashTable'. After the exception is thrown, the object to retract is still in the working memory. When I remove the line 'retract($obj)' in my rule, I don't get an exception. The problem occurs mainly in this rule, but also in other rules: rule "remove a cross talk" agenda-group "evaluation" activation-group "ag-crossTalk" lock-on-active true salience 40 when $ctf : CrossTalkFact($persID : uniquePersonID, $ctfTimestamp : timestamp) $pers : AnalysisCue(cueType == AnalysisCue.ACTION_STOP_TALKING, uniquePersonID == $persID, timestamp > $ctfTimestamp) from entry-point "LowLevelCueStream" then retract($ctf); //the suspicious line //... do some other things end My configuration: drools.dialect.java.compiler = JANINO EventProcessingOption = STREAM I was able to reproduce the problem with following versions: 5.1.1 5.2.0.M1 5.2.0.CR1 Stack trace from the version: 5.2.0.CR1 org.drools.runtime.rule.ConsequenceException: rule: remove a cross talk at org.drools.runtime.rule.impl.DefaultConsequenceExceptionHandler.handleException(DefaultConsequenceExceptionHandler.java:39) at org.drools.common.DefaultAgenda.fireActivation(DefaultAgenda.java:915) at org.drools.common.DefaultAgenda.fireNextItem(DefaultAgenda.java:844) at org.drools.common.DefaultAgenda.fireAllRules(DefaultAgenda.java:1055) at org.drools.common.AbstractWorkingMemory.fireAllRules(AbstractWorkingMemory.java:733) at org.drools.common.AbstractWorkingMemory.fireAllRules(AbstractWorkingMemory.java:699) at org.drools.impl.StatefulKnowledgeSessionImpl.fireAllRules(StatefulKnowledgeSessionImpl.java:218) ... Caused by: java.lang.NullPointerException at org.drools.core.util.RightTupleIndexHashTable.remove(RightTupleIndexHashTable.java:351) at org.drools.reteoo.NotNode.retractRightTuple(NotNode.java:178) at org.drools.reteoo.ObjectTypeNode.retractObject(ObjectTypeNode.java:235) at org.drools.reteoo.EntryPointNode.retractObject(EntryPointNode.java:229) at org.drools.common.NamedEntryPoint.retract(NamedEntryPoint.java:529) at org.drools.base.DefaultKnowledgeHelper.retract(DefaultKnowledgeHelper.java:226) at eu.ta2.orchestration.engine.cueLifter.Rule_remove_a_cross_talk_0.defaultConsequence(Unknown Source) at eu.ta2.orchestration.engine.cueLifter.Rule_remove_a_cross_talk_0DefaultConsequenceInvoker.evaluate(Unknown Source) at org.drools.common.DefaultAgenda.fireActivation(DefaultAgenda.java:905) ... 31 more Sometimes the exception occurs in the LeftTupleIndexHashTable: org.drools.runtime.rule.ConsequenceException: rule: remove a cross talk at org.drools.runtime.rule.impl.DefaultConsequenceExceptionHandler.handleException(DefaultConsequenceExceptionHandler.java:39) at org.drools.common.DefaultAgenda.fireActivation(DefaultAgenda.java:915) at org.drools.common.DefaultAgenda.fireNextItem(DefaultAgenda.java:844) at org.drools.common.DefaultAgenda.fireAllRules(DefaultAgenda.java:1055) at org.drools.common.AbstractWorkingMemory.fireAllRules(AbstractWorkingMemory.java:733) at org.drools.common.AbstractWorkingMemory.fireAllRules(AbstractWorkingMemory.java:699) at org.drools.impl.StatefulKnowledgeSessionImpl.fireAllRules(StatefulKnowledgeSessionImpl.java:218) ... Caused by: java.lang.NullPointerException at org.drools.core.util.LeftTupleIndexHashTable.remove(LeftTupleIndexHashTable.java:275) at org.drools.reteoo.NotNode.retractLeftTuple(NotNode.java:231) at org.drools.reteoo.SingleLeftTupleSinkAdapter.doPropagateRetractLeftTuple(SingleLeftTupleSinkAdapter.java:212) at org.drools.reteoo.SingleLeftTupleSinkAdapter.propagateRetractLeftTuple(SingleLeftTupleSinkAdapter.java:86) at org.drools.reteoo.JoinNode.retractLeftTuple(JoinNode.java:210) at org.drools.reteoo.SingleLeftTupleSinkAdapter.doPropagateRetractLeftTuple(SingleLeftTupleSinkAdapter.java:212) at org.drools.reteoo.SingleLeftTupleSinkAdapter.propagateRetractRightTuple(SingleLeftTupleSinkAdapter.java:119) at org.drools.reteoo.JoinNode.retractRightTuple(JoinNode.java:192) at org.drools.reteoo.ObjectTypeNode.retractObject(ObjectTypeNode.java:235) at org.drools.reteoo.EntryPointNode.retractObject(EntryPointNode.java:229) at org.drools.common.NamedEntryPoint.retract(NamedEntryPoint.java:529) at org.drools.base.DefaultKnowledgeHelper.retract(DefaultKnowledgeHelper.java:226) at eu.ta2.orchestration.engine.cueLifter.Rule_remove_a_cross_talk_0.defaultConsequence(Unknown Source) at eu.ta2.orchestration.engine.cueLifter.Rule_remove_a_cross_talk_0DefaultConsequenceInvoker.evaluate(Unknown Source) at org.drools.common.DefaultAgenda.fireActivation(DefaultAgenda.java:905) ... 31 more Any help is appreciated. Best regards, Wolfgang