[rules-users] Help with troubleshooting rules/Drools

[Robert Crawford]

Any advice on how to troubleshoot problems? I have a fairly simple set of
rules (a couple dozen), but keep having problems with fatal exceptions. The
most recent was:

org.drools.RuntimeDroolsException: Unexpected exception executing action
org.drools.reteoo.PropagationQueuingNode$PropagateAction at 1e60aa7
     at
org.drools.common.AbstractWorkingMemory.executeQueuedActions(AbstractWorkingMemory.java:977)
     at
org.drools.common.DefaultAgenda.fireUntilHalt(DefaultAgenda.java:1231)
     at
org.drools.common.AbstractWorkingMemory.fireUntilHalt(AbstractWorkingMemory.java:753)
     at
org.drools.common.AbstractWorkingMemory.fireUntilHalt(AbstractWorkingMemory.java:729)
     at
org.drools.impl.StatefulKnowledgeSessionImpl.fireUntilHalt(StatefulKnowledgeSessionImpl.java:234)
     at
com.kroger.tempmonitor.app.service.RuleService$1.run(RuleService.java:214)
     at java.lang.Thread.run(Thread.java:662)
Caused by: java.util.NoSuchElementException
     at java.util.LinkedList.remove(LinkedList.java:788)
     at java.util.LinkedList.removeFirst(LinkedList.java:134)
     at
org.drools.common.PropagationContextImpl.evaluateActionQueue(PropagationContextImpl.java:264)
     at
org.drools.reteoo.PropagationQueuingNode$AssertAction.execute(PropagationQueuingNode.java:357)
     at
org.drools.reteoo.PropagationQueuingNode.propagateActions(PropagationQueuingNode.java:238)
     at
org.drools.reteoo.PropagationQueuingNode$PropagateAction.execute(PropagationQueuingNode.java:502)
     at
org.drools.common.AbstractWorkingMemory.executeQueuedActions(AbstractWorkingMemory.java:975)
     ... 6 more


No mention of a rule name, so where do I begin?

My architecture is simple: one thread ran fireUntilHalt(), other (multiple)
threads inserting objects. Should I synchronize on the session so only one
thread is inserting at a time?

There's one rule that triggers a large number of inserts, and it used to
give me problems, but I've moved those inserts into Commands and those
problems seem to have gone away.

Any advice would be welcome, no matter how basic you think it is! Thanks!


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