Davide and Wolfgang, thank you both for your time and feedback into my questions as well as to other's questions. I'm rather interested in learning more about the internals of drools in the hopes of making contribution when and where possible. I'd imagine there's a developer guide that talks to fusion's architecture that would act as a companion to reviewing the source code?
Sincerely,
Jason
Confirmed as a race condition, hopefully it will be fixed in 5.6
Thanks Jason and Wolfgang
Davide
On 05/14/2013 06:43 AM, Jason Barto wrote:
Thanks Wolfgang. I'll change over to the 5.3 libraries and carry on with my testing. I'll also enter this issue into jira if it doesn't yet exist.
Sincerely,
JasonOn May 14, 2013 11:30 AM, "Wolfgang Laun" <wolfgang.laun@gmail.com> wrote:
Looks like a bug in Drools to me. It has the classic hallmark of a
race condition: the NPE does not happen with every run (on my system),
perhaps only with 85%.
Moreover, with 5.4.0 I get a similar NPE and also:
Exception in thread "main" java.util.NoSuchElementException
at java.util.LinkedList.remove(LinkedList.java:788)
at java.util.LinkedList.removeFirst(LinkedList.java:134)
at org.drools.common.PropagationContextImpl.evaluateActionQueue(PropagationContextImpl.java:344)
at org.drools.common.NamedEntryPoint.insert(NamedEntryPoint.java:342)
at org.drools.common.NamedEntryPoint.insert(NamedEntryPoint.java:298)
at org.drools.common.NamedEntryPoint.insert(NamedEntryPoint.java:123)
at org.drools.common.NamedEntryPoint.insert(NamedEntryPoint.java:53)
at overrun.Main.main(Main.java:64)
5.3.0 is the last version without this bug.
-W
On 14/05/2013, jpbarto <Jason.P.Barto@gmail.com> wrote:
> First the specifics: JDK 1.6, Mac OSX, using Drools 5.5 Final
>
> The full source code and rules are pasted below but here's the gist, I have
> a stateful knowledge session to which I am inserting events and running an
> accumulate on the input events. I have a for loop generating the events
> and
> inserting them as rapidly as possible. In the rules I use an accumulator
> to
> calculate the average of the values contained within the events. The
> behavior I'm observing is that if I insert ~120 events without any waiting
> I
> receive an NPE. If I Thread.sleep for even just 1ms the test goes off
> without a hitch. Have I uncovered a bug which should be logged in JIRA? I
> would check through JIRA to see if something similar has been logged but
> I'm
> so unfamiliar with the codebase, not to mention it could all just be user
> error.
>
> The NPE is as follows:
> Exception in thread "main" java.lang.NullPointerException
> at
> org.drools.reteoo.AccumulateNode.getFirstMatch(AccumulateNode.java:1050)
> at
> org.drools.reteoo.AccumulateNode.modifyLeftTuple(AccumulateNode.java:345)
> at
> org.drools.reteoo.SingleLeftTupleSinkAdapter.propagateModifyChildLeftTuple(SingleLeftTupleSinkAdapter.java:259)
> at
> org.drools.reteoo.AccumulateNode.evaluateResultConstraints(AccumulateNode.java:676)
> at
> org.drools.reteoo.ReteooWorkingMemory$EvaluateResultConstraints.execute(ReteooWorkingMemory.java:590)
> at
> org.drools.common.PropagationContextImpl.evaluateActionQueue(PropagationContextImpl.java:350)
> at
> org.drools.rule.SlidingLengthWindow.assertFact(SlidingLengthWindow.java:119)
> at org.drools.rule.BehaviorManager.assertFact(BehaviorManager.java:94)
> at org.drools.reteoo.WindowNode.assertObject(WindowNode.java:167)
> at
> org.drools.reteoo.CompositeObjectSinkAdapter.doPropagateAssertObject(CompositeObjectSinkAdapter.java:497)
> at
> org.drools.reteoo.CompositeObjectSinkAdapter.propagateAssertObject(CompositeObjectSinkAdapter.java:382)
> at org.drools.reteoo.ObjectTypeNode.assertObject(ObjectTypeNode.java:235)
> at org.drools.reteoo.EntryPointNode.assertObject(EntryPointNode.java:240)
> at org.drools.common.NamedEntryPoint.insert(NamedEntryPoint.java:350)
> at org.drools.common.NamedEntryPoint.insert(NamedEntryPoint.java:311)
> at org.drools.common.NamedEntryPoint.insert(NamedEntryPoint.java:127)
> at org.drools.common.NamedEntryPoint.insert(NamedEntryPoint.java:55)
> at drools5fusioneval.Average.main(Average.java:66)
>
> ### Average.java ###
> package drools5fusioneval;
>
> import java.io.IOException;
> import java.util.Random;
> import org.drools.KnowledgeBase;
> import org.drools.KnowledgeBaseConfiguration;
> import org.drools.KnowledgeBaseFactory;
> import org.drools.builder.KnowledgeBuilder;
> import org.drools.builder.KnowledgeBuilderFactory;
> import org.drools.builder.ResourceType;
> import org.drools.conf.EventProcessingOption;
> import org.drools.io.ResourceFactory;
> import org.drools.runtime.StatefulKnowledgeSession;
> import org.drools.runtime.rule.WorkingMemoryEntryPoint;
>
> class AvgDFEChannel implements org.drools.runtime.Channel {
> @Override
> public void send(Object o) {
> System.err.println ("Recieved channel message: "+ o);
> }
> }
>
> public class Average {
> public static void main(String[] args) throws InterruptedException,
> IOException {
> KnowledgeBaseConfiguration kbconfig =
> KnowledgeBaseFactory.newKnowledgeBaseConfiguration();
> kbconfig.setOption(EventProcessingOption.STREAM);
>
> KnowledgeBase kbase =
> KnowledgeBaseFactory.newKnowledgeBase(kbconfig);
>
> KnowledgeBuilder kbuilder =
> KnowledgeBuilderFactory.newKnowledgeBuilder();
>
> kbuilder.add(ResourceFactory.newClassPathResource("drools5fusioneval/average.drl"),
> ResourceType.DRL);
> if (kbuilder.hasErrors()) {
> System.err.println(kbuilder.getErrors().toString());
> }
> kbase.addKnowledgePackages(kbuilder.getKnowledgePackages());
>
> final StatefulKnowledgeSession session =
> kbase.newStatefulKnowledgeSession();
> session.registerChannel("heartbeat", new AvgDFEChannel ());
> WorkingMemoryEntryPoint ep01 =
> session.getWorkingMemoryEntryPoint("ep01");
>
> new Thread() {
> public void run() {
> session.fireUntilHalt();
> }
> }.start();
>
> Thread.sleep (5000); // give the engine time to get setup
>
> Server hiwaesdk = new Server ("hiwaesdk");
> session.insert(hiwaesdk);
> long LIMIT = 120;
> Random rnd = new Random (System.nanoTime());
>
> for (long i = LIMIT; i > 0; i--) {
> int j = rnd.nextInt (212);
> ep01.insert (new IntEvent (j));
> //Thread.sleep (0x1);
> }
>
> System.out.println (hiwaesdk);
> }
> }
>
>
> ### average.drl ###
> package drools5fusioneval
>
> declare IntEvent
> @role ( event )
> @expires(15s)
> end
>
> declare Statistics
> opsec : long
> total : long
> end
> global Statistics stats;
>
> rule "Init engine"
> salience 100
> when
> then
> stats = new Statistics ();
> stats.setTotal (0);
> stats.setOpsec (0);
> drools.getWorkingMemory ().setGlobal ("stats", stats);
> System.out.println ("Engine initialized");
> end
>
> rule "number rule"
> when
> $e : IntEvent () from entry-point ep01
> $s : Server (hostname == "hiwaesdk")
> then
> $s.currentTemp = $e.data;
> stats.setOpsec (stats.getOpsec () + 1);
> stats.setTotal (stats.getTotal () + 1);
> end
>
> rule "average temp"
> when
> Number ($avg : intValue) from accumulate (
> IntEvent ($temp : data) over window:length(10) from entry-point
> ep01, average ($temp)
> )
> $s : Server (hostname == "hiwaesdk")
> then
> $s.avgTemp = $avg;
> end
>
> rule "Heartbeat"
> timer ( int: 5s 5s)
> when
> then
> channels["heartbeat"].send ("Heartbeat: "+ stats.getOpsec () / 5 +", "+
> stats.getTotal ());
> stats.setOpsec (0);
> end
>
>
>
> --
> View this message in context:
> http://drools.46999.n3.nabble.com/NPE-from-reteoo-AccumulateNode-tp4023810.html
> Sent from the Drools: User forum mailing list archive at Nabble.com.
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