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: Mario Fusco Fix For: 6.2.0.CR1 Attachments: drools-gc-causes-npe-example.zip 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.