Hi Kenneth, 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$PackageClassLoader override this method without the use of "synchronized". I would suggest you create a JIRA issue for this. Regards, Mattias ----- Ursprungligt meddelande ----- Från: "kennywest" <kenneth.westelinck(a)telenet.be&gt; Till: rules-users(a)lists.jboss.org Skickat: onsdag, 31 okt 2012 12:41:29 Ämne: [rules-users] java.lang.LinkageError, but only sometimes Dear list, We have an application (A) deployed on JBoss 7.1.1 accepting commands (CQRS, but only C and Q :) ). A console application (B) is sending a large volume of commands to create entities in A. Entities in A are validated by Drools (plain drl files, configured in spring using drools-spring). Most of the time this works just fine. But sometimes, we get the following exception: java.lang.LinkageError: loader (instance of org/drools/rule/JavaDialectRuntimeData$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_gg___unique___name_656ee3db19d34e689d95e2d6b2be67b6Eval0InvokerGenerated.evaluate(Unknown Source) at a.b.c.Rule_gg___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. We are using: - JBoss 7.1.1 - drools 5.4.0.Final - jdk 1.6u30 - Windows 7 64 bit regards, Kenneth -- View this message in context: http://drools.46999.n3.nabble.com/java-lang-LinkageError-but-only-sometim... Sent from the Drools: User forum mailing list archive at Nabble.com. _______________________________________________ rules-users mailing list rules-users(a)lists.jboss.org https://lists.jboss.org/mailman/listinfo/rules-users

Cried wolf too soon :( Linkage error also occurs in 5.5.0.CR1 -- View this message in context: http://drools.46999.n3.nabble.com/java-lang-LinkageError-but-only-sometim... Sent from the Drools: User forum mailing list archive at Nabble.com.

I tried the suggestion from: https://issues.jboss.org/browse/JBRULES-3675 by adding a synchronized to the loadClass method. After further testing the problem remains :( So adding synchronized does not solve the problem. Any bright ideas? I am willing to try everything :) -- View this message in context: http://drools.46999.n3.nabble.com/java-lang-LinkageError-but-only-sometim... Sent from the Drools: User forum mailing list archive at Nabble.com.

Hi, Thank you for your reply. My original post was wrongly obfuscated. This is the correct stacktrace: 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] Hmmm, I don't understand very well, can you please elaborate? I don't think I understand this either. The rules all have unique names. The name: "Rule_gg___unique___name_656ee3db19d34e689d95e2d6b2be67b6" is generated by drools itself. ----- Original Message ----- From: "Wolfgang Laun" <wolfgang.laun(a)gmail.com&gt; To: "Rules Users List" <rules-users(a)lists.jboss.org&gt; Sent: Thursday, November 22, 2012 10:51:57 AM Subject: Re: [rules-users] java.lang.LinkageError, but only sometimes Just in case this has been missed (and using some guesswork) I should point out that the generated name extensions for the classes containing the right hand side code in a method are identical for two different rules clashing in the load of the serialized knowledge base. a/b/c/Rule_person_unique___name_656ee3db19d34e689d95e2d6b2be67b6 a.b.c.Rule_gg___unique___name_656ee3db19d34e689d95e2d6b2be67b6 Has there been some mixture of compiled packages in a way as it should not be done? Is the procedure for generating these artificial names watertight? -W On 22/11/2012, kennywest <kenneth.westelinck(a)telenet.be&gt; wrote: _______________________________________________ rules-users mailing list rules-users(a)lists.jboss.org https://lists.jboss.org/mailman/listinfo/rules-users