[jboss-jira] [JBoss JIRA] Created: (JBRULES-2098) Internal TupleSink list is not properly cleaned up when removing rules from a RuleBase

[Christian Nedregård (JIRA)]

Internal TupleSink list is not properly cleaned up when removing rules from a RuleBase
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                 Key: JBRULES-2098
                 URL: https://jira.jboss.org/jira/browse/JBRULES-2098
             Project: JBoss Drools
          Issue Type: Bug
      Security Level: Public (Everyone can see)
          Components: drools-core
    Affects Versions: 4.0.7
         Environment: Drools 4.0.7
Win XP
Sun JDK 1.4.2_11
            Reporter: Christian Nedregård
            Assignee: Mark Proctor


When a new rule is added to a rule base that has shareBetaNodes=true 'BuildUtils.attachNode' will iterate through existing TupleSink nodes and try to find an equal node to re-use.

In our production code we are seing NoClassDefFoundErrors from 'EvalConditionNode.equals' in scenarios where rules are both removed from and added to a rule base. The NoClassDefFoundErrors occours when a rule has recently been removed from the rule base and we are trying to add a new rule. When BuildUtils.attachNode'  iterates through the existing TupleSinks it also encounters TupleSinks that belongs to the rule that was removed. The call to the TupleSinks 'equal' method yields a NoClassDefFoundErrors because the target TupleSink are trying to reference the rule class that has been removed.

In this scenario we have removed rule 10418 and are adding 11140:
java.lang.NoClassDefFoundError: rules.subscriptiontype.Rule_RequiredSubscriptionTypes_10418_0
        at rules.subscriptiontype.Rule_RequiredSubscriptionTypes_10418_0Eval0Invoker.class$(Unknown Source)
        at rules.subscriptiontype.Rule_RequiredSubscriptionTypes_10418_0Eval0Invoker.getMethodBytecode(Unknown Source)
        at rules.subscriptiontype.Rule_RequiredSubscriptionTypes_11140_0Eval0Invoker.equals(Unknown Source)
        at org.drools.rule.EvalCondition.equals(EvalCondition.java:121)
        at org.drools.reteoo.EvalConditionNode.equals(EvalConditionNode.java:201)
        at org.drools.reteoo.builder.BuildUtils.attachNode(BuildUtils.java:101)


Attached is a stand-alone JUnit 4 testcase where the test 'testWithBetaNodeSharing' shows this problem. It does not produce a NoClassDefFoundError but we get a NPE from <removed rule>Eval0Invoker.getMethodBytecode instead (rule 1 has been removed, rule 3 is about to be added):
java.lang.NullPointerException
	at failure_on_removal.Rule_rule_1_0Eval0Invoker.getMethodBytecode(Unknown Source)
	at failure_on_removal.Rule_rule_3_0Eval0Invoker.equals(Unknown Source)
	at org.drools.rule.EvalCondition.equals(EvalCondition.java:121)
	at org.drools.reteoo.EvalConditionNode.equals(EvalConditionNode.java:201)
	at org.drools.reteoo.builder.BuildUtils.attachNode(BuildUtils.java:101)

We intepret this to be a symptom of the same problem.

The workaround is to disable beta node sharing wich will bypass the TupleSink  iteration alltogheter. This is shown in the test 'testWithoutBetaNodeSharing'.

Kind regards
Christian Nedregård

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