[rules-users] New in Drools, java.lang.NullPointerException at org.drools.reteoo.AccumulateNode.getFirstMatch(AccumulateNode.java:967)

Sat Apr 2 22:37:23 EDT 2011

Hi Wolfgang:

I write to you concerning JIRA https://issues.jboss.org/browse/JBRULES-2887,
which the SampleAlarmRules scenario which was attached to this discussion
was added in.

I've executed several times the SampleAlarmRules scenario and found that the
problem in that scenario is the existence of a JoinNode (Node 18) which
feeds two nodes, a JoinNode (Node 20) and an AccumlateNode (Node 25, the one
in which NPE occurs). I've seen that the child tuples of a join node are
interconnected via pointers and that those connections must be updated every
time a parent tuple of the join node is modified, via reAddLeft and
reAddRight tuple methods. When a JoinNode feeds two or more nodes, the child
tuples are interconnected in a ordered way that mixes tuples with different
sinks.

In the SampleAlarmRules scenario, when JoinNode18 is right modified, the
CompositeLeftTupleSinkAdapter processes several child tuples, but only the
last one is returned and reAddLeft'ed, hence breaking the child tuple
relations which it seems necessary to keep rete coherence. After this right
modify, the next left modify fails because a child tuple related to one node
of the composite sink is used to check the next operation to do in another
sink node different from the first one. This leads to a chain of incorrect
assertions which ends in the AccumulateNode NPE.

I've rewriten my rules in order to JoinNode18 feeds only AccumulateNode25
thus avoiding the NPE and returning to my user role. However I am not sure
if any CompositeSink starting at a JoinNode will have this or other problems
when being left or right modified. I hope this information helps to solve
this problem.

Best regards,

Manuel Ortiz.

2011/3/31 Wolfgang Laun <wolfgang.laun at gmail.com>

>
>
> 2011/3/31 Manuel Ortiz <manuel.ortizramos at gmail.com>
>
>> Hi Wofgang:
>>
>> Thank youvery much for your response. I was replaying to Mauricio when
>> your email has arrived. I hope the test case is useful.
>>
>>
> Thanks. Files are attached to the JIRA and JIRA is now at "critical".
> -W
>
>
>> Best regards,
>>
>> Manuel Ortiz.
>>
>>
>> 2011/3/31 Wolfgang Laun <wolfgang.laun at gmail.com>
>>
>>> Manuel,
>>>
>>> I have reported this (or a very similar) problem
>>> https://issues.jboss.org/browse/JBRULES-2887  with a small example to
>>> reproduce.
>>>
>>> The stack trace is not identical, so please try to reproduce this with a
>>> small test case; it is bound to happen with a rule (Test Negativo Alarma
>>> Acceso Portal Ubicacion UM) that modifies some fact that is used in an
>>> "accumulate" phrase, (If this pattern is different from the one I gave, I'll
>>> raise the issue priority to "critical".)
>>>
>>> Cheers
>>> Wolfgang
>>>
>>>
>>> 2011/3/30 Manuel Ortiz <manuel.ortizramos at gmail.com>
>>>
>>>> Hello all!
>>>>
>>>> I am new in Drools but day by day, test by test, I think I get a bit
>>>> more knowledge of how the rule engine works from user point of view. I've
>>>> been adding rules to an alarm system, increasing the complexity and
>>>> functionality in several steps. Unfortunately in the last step I found the
>>>> following NullPointerException inside the rule engine...
>>>>
>>>> java.lang.NullPointerException
>>>> at
>>>> org.drools.reteoo.AccumulateNode.getFirstMatch(AccumulateNode.java:967)
>>>> at
>>>> org.drools.reteoo.AccumulateNode.modifyLeftTuple(AccumulateNode.java:329)
>>>>  at
>>>> org.drools.reteoo.SingleLeftTupleSinkAdapter.propagateModifyChildLeftTuple(SingleLeftTupleSinkAdapter.java:239)
>>>> at
>>>> org.drools.reteoo.AccumulateNode.evaluateResultConstraints(AccumulateNode.java:640)
>>>>  at
>>>> org.drools.reteoo.AccumulateNode.assertObject(AccumulateNode.java:270)
>>>> at org.drools.reteoo.BetaNode.modifyObject(BetaNode.java:312)
>>>>  at
>>>> org.drools.reteoo.CompositeObjectSinkAdapter.doPropagateModifyObject(CompositeObjectSinkAdapter.java:460)
>>>> at
>>>> org.drools.reteoo.CompositeObjectSinkAdapter.propagateModifyObject(CompositeObjectSinkAdapter.java:428)
>>>>  at org.drools.reteoo.AlphaNode.modifyObject(AlphaNode.java:160)
>>>> at
>>>> org.drools.reteoo.CompositeObjectSinkAdapter.doPropagateModifyObject(CompositeObjectSinkAdapter.java:460)
>>>>  at
>>>> org.drools.reteoo.CompositeObjectSinkAdapter.propagateModifyObject(CompositeObjectSinkAdapter.java:428)
>>>> at
>>>> org.drools.reteoo.ObjectTypeNode.modifyObject(ObjectTypeNode.java:263)
>>>>  at
>>>> org.drools.reteoo.EntryPointNode.modifyObject(EntryPointNode.java:172)
>>>> at
>>>> org.drools.common.AbstractWorkingMemory.update(AbstractWorkingMemory.java:1442)
>>>>  at
>>>> org.drools.common.AbstractWorkingMemory.update(AbstractWorkingMemory.java:1349)
>>>> at
>>>> org.drools.base.DefaultKnowledgeHelper.update(DefaultKnowledgeHelper.java:183)
>>>>  at
>>>> org.drools.base.DefaultKnowledgeHelper.update(DefaultKnowledgeHelper.java:196)
>>>> at
>>>> es.simcasva.alarmas.rules.Rule_Test_Negativo_Alarma_Acceso_Portal_Ubicacion_UM_0.defaultConsequence(Rule_Test_Negativo_Alarma_Acceso_Portal_Ubicacion_UM_0.java:18)
>>>>  at
>>>> es.simcasva.alarmas.rules.Rule_Test_Negativo_Alarma_Acceso_Portal_Ubicacion_UM_0DefaultConsequenceInvoker.evaluate(Rule_Test_Negativo_Alarma_Acceso_Portal_Ubicacion_UM_0DefaultConsequenceInvoker.java:44)
>>>>  at
>>>> org.drools.common.DefaultAgenda.fireActivation(DefaultAgenda.java:917)
>>>> at org.drools.common.DefaultAgenda.fireNextItem(DefaultAgenda.java:856)
>>>>  at
>>>> org.drools.common.DefaultAgenda.fireAllRules(DefaultAgenda.java:1071)
>>>> at
>>>> org.drools.common.AbstractWorkingMemory.fireAllRules(AbstractWorkingMemory.java:785)
>>>>  at
>>>> org.drools.common.AbstractWorkingMemory.fireAllRules(AbstractWorkingMemory.java:751)
>>>> at
>>>> org.drools.impl.StatefulKnowledgeSessionImpl.fireAllRules(StatefulKnowledgeSessionImpl.java:218)
>>>>
>>>> I've been trying to find the problem, and found a strange interaction
>>>> between three rules that makes the null pointer to appear. The alarm system
>>>> has many rules now and it is difficult to simplify the scenario, so I just
>>>> would like to know what is the funcion of AccumulateNode object in order to
>>>> have an idea of the NullPointerException possible cause.
>>>>
>>>> Can anyone help me?
>>>>
>>>> Thank you in advance for your time.
>>>>
>>>> Regards,
>>>>
>>>> Manuel Ortiz.
>>>>
>>>>
>>>> _______________________________________________
>>>> rules-users mailing list
>>>> rules-users at lists.jboss.org
>>>> https://lists.jboss.org/mailman/listinfo/rules-users
>>>>
>>>>
>>>
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