[rules-users] Help debugging NPE

[Dirk Bergstrom]

Edson Tirelli was heard to exclaim, On 06/24/09 06:14:
>       The problem seems not related to shadow facts, but to constraint
> resolution and fact data extraction. It might be a bug or not... need
> more info.

I've also seen the following stacktrace:

java.lang.ArrayIndexOutOfBoundsException: 40440
        at org.drools.util.TupleIndexHashTable.toArray(TupleIndexHashTable.java:217)
        at org.drools.reteoo.CollectNode.retractObject(CollectNode.java:260)
        at
org.drools.reteoo.SingleObjectSinkAdapter.propagateRetractObject(SingleObjectSinkAdapter.java:32)
        at org.drools.reteoo.AlphaNode.retractObject(AlphaNode.java:164)
        at
org.drools.reteoo.SingleObjectSinkAdapter.propagateRetractObject(SingleObjectSinkAdapter.java:32)
        at org.drools.reteoo.AlphaNode.retractObject(AlphaNode.java:164)
        at
org.drools.reteoo.CompositeObjectSinkAdapter.propagateRetractObject(CompositeObjectSinkAdapter.java:366)
        at org.drools.reteoo.ObjectTypeNode.retractObject(ObjectTypeNode.java:189)
        at org.drools.reteoo.Rete.retractObject(Rete.java:215)
        at org.drools.reteoo.ReteooRuleBase.retractObject(ReteooRuleBase.java:211)
        at
org.drools.reteoo.ReteooWorkingMemory.doRetract(ReteooWorkingMemory.java:79)
        at
org.drools.common.AbstractWorkingMemory.retract(AbstractWorkingMemory.java:1023)
        at
org.drools.common.AbstractWorkingMemory.retract(AbstractWorkingMemory.java:982)
        at
net.juniper.dash.data.DataSource.reconcileAssertedRecords(DataSource.java:362)

>       In any case, the offending rule is not the one you showed. The
> offending rule contains a double beta constraint in a join:

I know it's not in that rule.  It must be in this one, since it's the only one
that uses rli_nums:

$npi : NPIRecord( )
$pr : PRRecord( npi == "", rli != "" )
$rli : RLIRecord( id memberOf $pr.rli_nums, npi_program == $npi.synopsis )

>       Can you narrow it down? Did you tried with Drools 5.0.1?

I haven't tried any of the 5.x series.  Is there a guide to migrating my code
from 4.0 to 5.0?  I looked on the jboss site, the wiki, the blog, and this
mailing list, but I didn't find anything.  I'm under a lot of time pressure, and
changing to 5.0 doesn't look like a quick fix...

> 2009/6/24 Dirk Bergstrom <dirk at juniper.net <mailto:dirk at juniper.net>>
> 
>     I'm running into an NPE using Drools 4.0.7, and I'm stumped by it
>     (stacktrace
>     below).  I made some changes to seemingly unrelated code, and this
>     error started
>     showing up.  It would help me to understand what's going on if
>     someone could
>     tell me roughly what's going on here.  Since the error is thrown by
>     generated
>     code (in what I assume is a shadow proxy), I can't tell what the
>     offending null
>     pointer is.  I'm not even entirely sure what's triggering the bug
>     (it happens
>     half an hour into the run of big multi-threaded application with
>     about 40K
>     objects in the working memory).
> 
>     Is this happening because:
> 
>     *) getRli_nums() in one of my PRRecord objects is returning a null
>     value?
> 
>     *) There is a null PRRecord object backing the shadow proxy?
> 
>     *) Some other thing is null?
> 
>     *) I'm running into a bug in Drools?
> 
>     I stuck in this rule:
> 
>     when
>      $pr : PRRecord( rli_nums == null )
>     then
>      System.out.println($pr.getId());
>     end
> 
>     And it didn't print anything, so I'm inclined to think that this is
>     not a simple
>     matter of something returning a null value...
> 
>     I'll be most appreciative of any help I can get.
> 
>     Here's the stacktrace:
> 
>     java.lang.NullPointerException
>            at
>     org.drools.base.net.juniper.dash.data.PRRecord13409648$getRli_nums.getValue(Unknown
>     Source)
>            at
>     org.drools.base.ClassFieldExtractor.getValue(ClassFieldExtractor.java:127)
>            at
>     org.drools.base.evaluators.BaseMemberOfEvaluator.evaluateCachedRight(BaseMemberOfEvaluator.java:45)
>            at
>     org.drools.rule.VariableRestriction.isAllowedCachedRight(VariableRestriction.java:89)
>            at
>     org.drools.rule.VariableConstraint.isAllowedCachedRight(VariableConstraint.java:81)
>            at
>     org.drools.common.DoubleBetaConstraints.isAllowedCachedRight(DoubleBetaConstraints.java:164)
>            at org.drools.reteoo.JoinNode.retractObject(JoinNode.java:189)
>            at
>     org.drools.reteoo.CompositeObjectSinkAdapter.propagateRetractObject(CompositeObjectSinkAdapter.java:375)
>            at
>     org.drools.reteoo.ObjectTypeNode.retractObject(ObjectTypeNode.java:189)
>            at org.drools.reteoo.Rete.retractObject(Rete.java:215)
>            at
>     org.drools.reteoo.ReteooRuleBase.retractObject(ReteooRuleBase.java:211)
>            at
>     org.drools.reteoo.ReteooWorkingMemory.doRetract(ReteooWorkingMemory.java:79)
>            at
>     org.drools.common.AbstractWorkingMemory.update(AbstractWorkingMemory.java:1250)
>            at
>     org.drools.common.AbstractWorkingMemory.update(AbstractWorkingMemory.java:1203)
>            at
>     net.juniper.dash.data.DataSource.reconcileAssertedRecords(DataSource.java:409)


-- 
Dirk Bergstrom               dirk at juniper.net
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Juniper Networks Inc.,          Computer Geek
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