[jboss-jira] [JBoss JIRA] (JBRULES-3675) java.lang.LinkageError, but only sometimes (multithreading issue)

[kenneth westelinck (JIRA)]

    [ https://issues.jboss.org/browse/JBRULES-3675?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12731809#comment-12731809 ] 

kenneth westelinck commented on JBRULES-3675:
---------------------------------------------

I have checked-out the 5.5.0.CR1 tag and patched drools-core by adding synchronized to the loadClass(String, boolean) method. First tests show this is working fine and we haven't encountered the LinkageError problem yet. Any chance this will be included in the 5.5.0 release?
                
> java.lang.LinkageError, but only sometimes (multithreading issue)
> -----------------------------------------------------------------
>
>                 Key: JBRULES-3675
>                 URL: https://issues.jboss.org/browse/JBRULES-3675
>             Project: Drools
>          Issue Type: Bug
>      Security Level: Public(Everyone can see) 
>          Components: drools-core
>    Affects Versions: 5.4.0.Final
>         Environment: - JBoss 7.1.1
> - drools 5.4.0.Final
> - jdk 1.6u30
> - Windows 7 64 bit
>            Reporter: kenneth westelinck
>            Assignee: Mark Proctor
>
> See mail on mailinglist:
> {noformat}
> We have an application (A) deployed on JBoss 7.1.1 accepting commands (CQRS,
> but only C and Q :) ). A console application (B) is sending a large volume
> of commands to create entities in A. Entities in A are validated by Drools
> (plain drl files, configured in spring using drools-spring). Most of the
> time this works just fine. But sometimes, we get the following exception:
> java.lang.LinkageError: loader (instance of
> org/drools/rule/JavaDialectRuntimeData$PackageClassLoader): attempted
> duplicate class definition for name:
> "a/b/c/Rule_person_unique___name_656ee3db19d34e689d95e2d6b2be67b6"
>         at java.lang.ClassLoader.defineClass1(Native Method) [rt.jar:1.6.0_30]
>         at java.lang.ClassLoader.defineClassCond(ClassLoader.java:631) [rt.jar:1.6.0_30]
>         at java.lang.ClassLoader.defineClass(ClassLoader.java:615) [rt.jar:1.6.0_30]
>         at org.drools.rule.JavaDialectRuntimeData$PackageClassLoader.fastFindClass(JavaDialectRuntimeData.java:615) [drools-core-5.4.0.Final.jar:5.4.0.Final]
>         at org.drools.util.CompositeClassLoader$CachingLoader.load(CompositeClassLoader.java:254) [knowledge-api-5.4.0.Final.jar:5.4.0.Final]
>         at org.drools.util.CompositeClassLoader$CachingLoader.load(CompositeClassLoader.java:237) [knowledge-api-5.4.0.Final.jar:5.4.0.Final]
>         at org.drools.util.CompositeClassLoader.loadClass(CompositeClassLoader.java:88) [knowledge-api-5.4.0.Final.jar:5.4.0.Final]
>         at java.lang.ClassLoader.loadClass(ClassLoader.java:295) [rt.jar:1.6.0_30]
>         at java.lang.ClassLoader.loadClass(ClassLoader.java:247) [rt.jar:1.6.0_30]
>         at a.b.c.Rule_person___unique___name_656ee3db19d34e689d95e2d6b2be67b6Eval0InvokerGenerated.evaluate(Unknown Source)
>         at a.b.c.Rule_person___unique___name_656ee3db19d34e689d95e2d6b2be67b6Eval0Invoker.evaluate(Unknown Source)
>         at org.drools.rule.EvalCondition.isAllowed(EvalCondition.java:114) [drools-core-5.4.0.Final.jar:5.4.0.Final]
> Any idea where this is coming from or what's causing this. 
> {noformat}
> And the answer:
> {noformat}
> I have never experienced this myself, but after having a quick look at the code I believe this could be a multi-threading problem.
> In the abstract class java.lang.ClassLoader the method loadClass(String, boolean) is synchronized, but both org.drools.util.CompositeClassLoader
> and org.drools.rule.JavaDialectRuntimeData$PackageClassLoader override this method without the use of "synchronized".
> I would suggest you create a JIRA issue for this.
> {noformat}
> We are now trying 5.5.0.CR1 and so far, we have not encountered this issue. I'll keep you posted should the same issue appear on 5.5.0.CR1

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