[jboss-jira] [JBoss JIRA] (DROOLS-629) NullPointerException thrown on next call to insert and fireAllRules after stream garbage collection runs

[Mike Wilson (JIRA)]

Mike Wilson created DROOLS-629:
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             Summary: NullPointerException thrown on next call to insert and fireAllRules after stream garbage collection runs
                 Key: DROOLS-629
                 URL: https://issues.jboss.org/browse/DROOLS-629
             Project: Drools
          Issue Type: Bug
    Affects Versions: 6.1.0.Final, 6.2.0.Beta3
            Reporter: Mike Wilson
            Assignee: Mark Proctor


I have observed that the following NullPointerException (NPE) occurs consistently with a very specific set of rules and a very specific set of inputs into a stream session:
{code}
java.lang.NullPointerException
    at org.drools.core.util.AbstractHashTable$SingleIndex.equal(AbstractHashTable.java:491)
    at org.drools.core.util.index.LeftTupleList.matches(LeftTupleList.java:266)
    at org.drools.core.util.index.LeftTupleIndexHashTable.get(LeftTupleIndexHashTable.java:434)
    at org.drools.core.util.index.LeftTupleIndexHashTable.getFirst(LeftTupleIndexHashTable.java:217)
    at org.drools.core.reteoo.BetaNode.getFirstLeftTuple(BetaNode.java:443)
    at org.drools.core.phreak.PhreakJoinNode.doRightInserts(PhreakJoinNode.java:144)
    at org.drools.core.phreak.PhreakJoinNode.doNode(PhreakJoinNode.java:56)
    at org.drools.core.phreak.RuleNetworkEvaluator.switchOnDoBetaNode(RuleNetworkEvaluator.java:548)
    at org.drools.core.phreak.RuleNetworkEvaluator.evalBetaNode(RuleNetworkEvaluator.java:534)
    at org.drools.core.phreak.RuleNetworkEvaluator.innerEval(RuleNetworkEvaluator.java:334)
    at org.drools.core.phreak.RuleNetworkEvaluator.outerEval(RuleNetworkEvaluator.java:161)
    at org.drools.core.phreak.RuleNetworkEvaluator.evaluateNetwork(RuleNetworkEvaluator.java:116)
    at org.drools.core.phreak.RuleExecutor.reEvaluateNetwork(RuleExecutor.java:229)
    at org.drools.core.phreak.RuleExecutor.evaluateNetworkAndFire(RuleExecutor.java:98)
    at org.drools.core.common.DefaultAgenda.fireNextItem(DefaultAgenda.java:988)
    at org.drools.core.common.DefaultAgenda.fireAllRules(DefaultAgenda.java:1274)
    at org.drools.core.impl.StatefulKnowledgeSessionImpl.fireAllRules(StatefulKnowledgeSessionImpl.java:1281)
    at org.drools.core.impl.StatefulKnowledgeSessionImpl.fireAllRules(StatefulKnowledgeSessionImpl.java:1254)
    ...
{code}

The exception always occurs on the next call to "insert" and "fireAllRules" after the following method is invoked within the session: org.drools.core.common.DefaultAgenda$DefaultGarbageCollector.forceGcUnlinkedRules().

I have attached a maven project that contains a JUnit test, which reproduces this exception using Drools version 6.2.0.Beta3.

A side effect of this exeption occurring in the middle of fireAllRules is that an extra fact is left over in working memory, which is essentially a memory leak. I assume this is because the evaluation of the LHS of the rules is what causes the NPE to occur, so the fact is not deleted, because the RHS of the rules don't execute.



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