[jboss-jira] [JBoss JIRA] (DROOLS-635) NPE thrown intermittently in multi-threading environment
[
https://issues.jboss.org/browse/DROOLS-635?page=com.atlassian.jira.plugin...
]
Mario Fusco commented on DROOLS-635:
------------------------------------
As the comment to that remove method says: "we assume that this rightTuple is
contained in this hash table" and this means that a null check there shouldn't be
necessary. More important we actually want that method to fail fast if we try to remove a
tuple that is not in that memory and for this reason we intentionally avoid to perform any
null check there.
Now I see that method is not thread-safe and then I understand how it could fail if
executed by multiple threads in parallel. What I don't understand is under which
cicumstances this race condition happens. In other terms the problem is not in the missing
null check but in a missing synchronization. Unfortunately at the moment I am not able to
reproduce this condition and then fix this bug. If you have a test case reproducing this
problem can you please attach it to this ticket? Thanks.
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)
--
This message was sent by Atlassian JIRA
(v6.3.1#6329)