Re: [rules-users] threw error java.lang.ClassCastException: org.drools.reteoo.FromNode$FromMemory cannot be cast to org.drools.reteoo.BetaMemory

Ok, so there are two main possibilities.. either the locking mechanism does not work appropriately and there is a concurrency issue, or the particular rule structure exposes an edge case in node comparison and reuse. The former is more probable, but should be relatively easy to see. I need your help in testing this in the production environment where you get the exception. You should essentially add a org.drools.event.knowledgebase.KnowledgeBaseEventListener to the knowledge base : kb.addEventListener( new MyLoggingKBEventListener() ); and provide an implementation that suitably logs which thread is executing which action. The KnowledgeBaseEventListener is an interface with methods such as: void beforeKnowledgeBaseLocked(BeforeKnowledgeBaseLockedEvent event); void afterKnowledgeBaseLocked(AfterKnowledgeBaseLockedEvent event); void beforeRuleAdded(BeforeRuleAddedEvent event); void afterRuleAdded(AfterRuleAddedEvent event); etc... Can you try this solution? Thanks! Davide On 05/08/2013 10:57 AM, mohdejaz74 wrote: