[rules-users] KnowledgeAgent and Pipeline

[Mark Proctor]

David Zeigler wrote:
> I opened a Jira and attached a patch for the unit test with my case
> that results in a NPE.
> https://jira.jboss.org/jira/browse/JBRULES-2090
>   
thanks for finding this, it's now fxed in trunk.

Mark
> Thanks,
> David
>
> 2009/5/12 Mark Proctor <mproctor at codehaus.org>:
>   
>> David Zeigler wrote:
>>
>> Hi Mark,
>> Thanks for the quick reply.
>>
>> Now I'm getting a NullPointerException when I insert the message into
>> the pipeline using 5.0.1.SNAPSHOT from today:
>> java.lang.NullPointerException
>> 	at
>> org.drools.runtime.pipeline.impl.StatelessKnowledgeSessionPipelineImpl.insert(StatelessKnowledgeSessionPipelineImpl.java:24)
>>
>> It looks like StatelessKnowledgeSession's ruleBase is null when
>> created by the KnowledgeAgent, which poses a problem since
>> StatelessKnowledgeSessionPipelineImpl invokes getRootClassLoader() on
>> the session's ruleBase.
>>
>> Here's what I'm doing:
>> StatelessKnowledgeSession ksession = kagent.newStatelessKnowledgeSession();
>> Pipeline pipeline =
>> PipelineFactory.newStatelessKnowledgeSessionPipeline(ksession);
>> pipeline.setReceiver(messageTransformer);
>> pipeline.insert(message);  // NPE here
>>
>>
>> I'm a bit busy to look into this in detail. But there is a unit test for
>> this:
>> http://anonsvn.labs.jboss.com/labs/jbossrules/trunk/drools-compiler/src/test/java/org/drools/agent/KnowledgeAgentTest.java
>> testModifyFileUrlWithStateless
>>
>> That test works, maybe you could do an adaption of that unit test to make it
>> fail and we can add it to the test framework, and which also means I'll fix
>> it asap, if it's a bug.
>>
>> Mark
>>
>> Thanks,
>> David
>>
>> 2009/5/12 Mark Proctor <mproctor at codehaus.org>:
>>
>>
>> David Zeigler wrote:
>>
>> Hi,
>> I've set up the KnowledgeAgent to automatically reload the rules
>> resources if they change.  If I use this with a Pipeline, it seems
>> that its StatelessKnowledgeSession is not reloaded automatically.  The
>> only way I've been able to get the Pipeline to reflect the rules
>> change is to do the following prior to each pipeline.insert():
>>
>> StatelessKnowledgeSession ksession =
>> kagent.getKnowledgeBase().newStatelessKnowledgeSession();
>> Pipeline pipeline =
>> PipelineFactory.newStatelessKnowledgeSessionPipeline(ksession);
>> pipeline.setReceiver( messageTransformer );
>>
>> Reloading the pipeline for each request adds a lot of overhead (halves
>> my transactions per second).  Is there a way to automatically reload
>> the Pipeline's session when its needed instead of recreating the
>> Pipeline prior to each insert?  I see there is a
>> ResourceChangeListener interface that I could probably use to
>> accomplish this, but I figured I'd ask in case there is a better way
>> to handle this case with pipelines.  What's the best approach?
>>
>>
>> Try trunk, it has a fix for this. Where if you get the
>> StatelessKnowledgeSession directly from the knowledgeagent every execute
>> will check for a new KnowledgeBase.
>> https://hudson.jboss.org/hudson/job/drools/lastSuccessfulBuild/artifact/trunk/target/
>>
>> https://hudson.jboss.org/hudson/job/drools/lastSuccessfulBuild/artifact/trunk/target/javadocs/stable/drools-api/org/drools/agent/KnowledgeAgent.html
>> KnowledgeAgent.newStatelessKnowledgeSession(KnowledgeSessionConfiguration conf)
>>  StatelessKnowledgeSession created from here will always have the execute()
>> method called against the latest built KnowledgeBase.
>>
>> So now you can just use that returned session with the pipeline and it
>> should always be using the latest rules.
>>
>> Mark
>>
>> I'm using 5.0.0.CR1.
>>
>> Thanks!
>> David
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