NPE thrown intermittently in multi-threading environment -------------------------------------------------------- Key: DROOLS-635 URL: https://issues.jboss.org/browse/DROOLS-635 Project: Drools Issue Type: Bug Affects Versions: 6.1.0.Final, 6.2.0.Beta1, 6.2.0.CR1 Reporter: John Le Assignee: Mario Fusco Below is the stacktrace for the NPE, it appears to be an issue when accumulate function is called under multi-threading condition. Please look at the remove function in the RightTupleIndexHashTable.java file. The remove function does not appear to have proper null checking around the "current" object. public void remove(final RightTuple rightTuple) { RightTupleList memory = rightTuple.getMemory(); memory.remove( rightTuple ); this.factSize--; if ( memory.first == null ) { final int index = indexOf( memory.hashCode(), this.table.length ); RightTupleList previous = null; RightTupleList current = (RightTupleList) this.table[index]; while ( current != memory ) { previous = current; current = (RightTupleList) current.getNext(); } if ( previous != null ) { previous.next = current.next; } else { this.table[index] = current.next; } this.size--; } rightTuple.clear(); } Stacktrace: java.lang.NullPointerException org.drools.core.util.index.RightTupleIndexHashTable.remove(RightTupleIndexHashTable.java:389) org.drools.core.phreak.RuleNetworkEvaluator.doUpdatesReorderRightMemory(RuleNetworkEvaluator.java:855) org.drools.core.phreak.PhreakJoinNode.doNode(PhreakJoinNode.java:43) org.drools.core.phreak.RuleNetworkEvaluator.switchOnDoBetaNode(RuleNetworkEvaluator.java:548) org.drools.core.phreak.RuleNetworkEvaluator.evalBetaNode(RuleNetworkEvaluator.java:534) org.drools.core.phreak.RuleNetworkEvaluator.innerEval(RuleNetworkEvaluator.java:334) org.drools.core.phreak.RuleNetworkEvaluator.outerEval(RuleNetworkEvaluator.java:161) org.drools.core.phreak.RuleNetworkEvaluator.evaluateNetwork(RuleNetworkEvaluator.java:116) org.drools.core.phreak.RuleExecutor.reEvaluateNetwork(RuleExecutor.java:230) org.drools.core.phreak.RuleExecutor.evaluateNetworkAndFire(RuleExecutor.java:103) org.drools.core.common.DefaultAgenda.fireNextItem(DefaultAgenda.java:988) org.drools.core.common.DefaultAgenda.fireAllRules(DefaultAgenda.java:1274) org.drools.core.impl.StatefulKnowledgeSessionImpl.fireAllRules(StatefulKnowledgeSessionImpl.java:1284) org.drools.core.impl.StatefulKnowledgeSessionImpl.fireAllRules(StatefulKnowledgeSessionImpl.java:1257)