[jboss-jira] [JBoss JIRA] Created: (JBRULES-2821) Race condition in MVELDialect

[Doug Pedrick (JIRA)]

Race condition in MVELDialect
-----------------------------

                 Key: JBRULES-2821
                 URL: https://jira.jboss.org/browse/JBRULES-2821
             Project: Drools
          Issue Type: Bug
      Security Level: Public (Everyone can see)
          Components: drools-compiler
    Affects Versions: 5.1.1.FINAL
         Environment: JDK 1.6.0_20  Mac OS X 10.6.5
            Reporter: Doug Pedrick
            Assignee: Mark Proctor


Multiple threads loading different rulesets (each having local copies of KnowledgeBuilderConfiguration, KnowledgeBuilder, KnowledgeBaseConfiguration, and KnowledgeBase) can result in a race condition with the AbstractParser.OPERATIONS hash map in MVEL.

MVELDialect and MVELExprAnalyzer both invoke ExpressionCompiler.compile.  MVELDialect.compile calls AbstractParser.setLanguageLevel which clears and reloads the OPERATIONS static HashMap.  It does so while holding COMPILER_LOCK.  MVELExprAnalyzer calls ExpressionCompiler.compile without holding COMPILER_LOCK, resulting in OPERATIONS sometimes being empty when called, causing an NPE when attempting to autobox an Operator Integer to primitive.

There are other areas in Drools code that ultimately depend on OPERATIONS and should be protected as well.

java.lang.NullPointerException
   at org.mvel2.compiler.ExpressionCompiler._compile(ExpressionCompiler.java:250)
   at org.mvel2.compiler.ExpressionCompiler.compile(ExpressionCompiler.java:68)
   at org.drools.rule.builder.dialect.mvel.MVELExprAnalyzer.analyzeExpression(MVELExprAnalyzer.java:86)
   at org.drools.rule.builder.dialect.mvel.MVELDialect.analyzeExpression(MVELDialect.java:461)
   at org.drools.rule.builder.dialect.mvel.MVELDialect.analyzeExpression(MVELDialect.java:446)
   at org.drools.rule.builder.dialect.mvel.MVELPredicateBuilder.build(MVELPredicateBuilder.java:50)
   at org.drools.rule.builder.PatternBuilder.build(PatternBuilder.java:654)
   at org.drools.rule.builder.PatternBuilder.rewriteToEval(PatternBuilder.java:482)
   at org.drools.rule.builder.PatternBuilder.build(PatternBuilder.java:340)
   at org.drools.rule.builder.PatternBuilder.buildConstraint(PatternBuilder.java:264)
   at org.drools.rule.builder.PatternBuilder.build(PatternBuilder.java:213)
   at org.drools.rule.builder.PatternBuilder.build(PatternBuilder.java:108)
   at org.drools.rule.builder.GroupElementBuilder.build(GroupElementBuilder.java:69)
   at org.drools.rule.builder.GroupElementBuilder.build(GroupElementBuilder.java:43)
   at org.drools.rule.builder.GroupElementBuilder.build(GroupElementBuilder.java:69)
   at org.drools.rule.builder.RuleBuilder.build(RuleBuilder.java:79)
   at org.drools.compiler.PackageBuilder.addRule(PackageBuilder.java:1154)
   at org.drools.compiler.PackageBuilder.addPackage(PackageBuilder.java:636)
   at org.drools.compiler.PackageBuilder.addPackageFromDrl(PackageBuilder.java:266)
   at org.drools.compiler.PackageBuilder.addKnowledgeResource(PackageBuilder.java:458)
   at org.drools.builder.impl.KnowledgeBuilderImpl.add(KnowledgeBuilderImpl.java:28)

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