[rules-users] Manuel's Analysis of JBRULES-2887 (NPE in AccumulateNode.java:967)

Sun Apr 3 02:46:43 EDT 2011

Thanks a lot, and I've added your analysis as a comment to JBRULES-2887.
Wolfgang

2011/4/3 Manuel Ortiz <manuel.ortizramos at gmail.com>

> 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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