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@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@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: