Can drools work in multithreaded environment?

Hi,

While doing a load test with jmeter,my web service
application with drools
works fine for few clients(5 simultaneous hits for 10 times)

but when i increase my clients(120 simultanious hits for 100
times) i am
gettin the following exception for 
few client, (out of 12,000 hits 200 throws this exception)

problem encountered at node [11] 5{170,189}: unable to
resolve property:
null pointer exception in property: declr.identifier
org.mvel.TemplateInterpreter.execute(TemplateInterpreter.jav
a:528)
org.mvel.TemplateInterpreter.parse(TemplateInterpreter.java:
341)
org.drools.rule.builder.dialect.java.AbstractJavaBuilder.gen
eratTemplates(AbstractJavaBuilder.java:113)
org.drools.rule.builder.dialect.java.JavaConsequenceBuilder.
build(JavaConsequenceBuilder.java:95)
org.drools.rule.builder.RuleBuilder.build(RuleBuilder.java:6
7)
org.drools.compiler.PackageBuilder.addRule(PackageBuilder.ja
va:446)
org.drools.compiler.PackageBuilder.addPackage(PackageBuilder
.java:304)
org.drools.compiler.PackageBuilder.addPackageFromDrl(Package
Builder.java:167)
com.drools.util.RuleEngine.applyRule(RuleEngine.java:47)
com.drools.util.DroolsController.getAdvertisement(DroolsCont
roller.java:94)
com.drools.util.DroolsController.routeBusinessMethod(DroolsC
ontroller.java:67)
com.drools.util.DroolsController.getAdvertisement(DroolsCont
roller.java:43)
com.drools.MyEndpoint.getAdvertisement(MyEndpoint.java:237)
com.drools.MyEndpoint.process(MyEndpoint.java:144)
org.apache.servicemix.common.AsyncBaseLifeCycle.doProcess(As
yncBaseLifeCycle.java:489)
org.apache.servicemix.common.AsyncBaseLifeCycle.processExcha
nge(AsyncBaseLifeCycle.java:441)
org.apache.servicemix.common.BaseLifeCycle.onMessageExchange
(BaseLifeCycle.java:46)
org.apache.servicemix.jbi.messaging.DeliveryChannelImpl.proc
essInBound(DeliveryChannelImpl.java:595)
org.apache.servicemix.jbi.nmr.flow.AbstractFlow.doRouting(Ab
stractFlow.java:174)
org.apache.servicemix.jbi.nmr.flow.seda.SedaFlow.doRouting(S
edaFlow.java:176)
org.apache.servicemix.jbi.nmr.flow.seda.SedaQueue$1.run(Seda
Queue.java:134)
edu.emory.mathcs.backport.java.util.concurrent.ThreadPoolExe
cutor$Worker.runTask(ThreadPoolExecutor.java:665)
edu.emory.mathcs.backport.java.util.concurrent.ThreadPoolExe
cutor$Worker.run(ThreadPoolExecutor.java:690)
java.lang.Thread.run(Thread.java:619)

drl file has 6 rules,
5 rules                   - which retract facts which passes
the rule.
1 rule(low salience)  - will add the fact to java.util.List
(set as global)
which passes the rule.

1 . Am i getting this error bcoz of the global list? or any
other reason?
2 . How to solve this problem?

here the rules,

<code>
global java.util.List feasibleAdv;

rule " percentage rule "   
    when
        $adv : Advertisement( percentageLimit != 0 ,
percentageLimit <
playedPercentage )             		
    then
    	System.out.println("remove this adv (failed
percentage):
"+$adv.getAdvertisementID());               
       	retract($adv);
end

rule "per day rule"
    when
        $adv : Advertisement( limitperday != 0 , limitperday
<= playedperday
)        
    then                
        //System.out.println("remove this adv (failed
day):
"+$adv.getAdvertisementID());
        retract($adv);        
end

rule "per week rule"
    when
        $adv : Advertisement( limitperweek != 0 ,
limitperweek <=
playedperweek)        
    then        
        //System.out.println("remove this adv (failed
week):
"+$adv.getAdvertisementID());
        retract($adv);                   
end

rule "per month rule"
    when
        $adv : Advertisement( limitpermonth != 0 ,
limitpermonth <=
playedpermonth)        
    then                
        //System.out.println("remove this adv (failed
month) :
"+$adv.getAdvertisementID());
        retract($adv);                   
end

rule "total played rule"
    when
        $adv : Advertisement( totallimit != 0 , totallimit
<= totalplayed )        
    then                
        //System.out.println("remove this adv (failed
total played) :
"+$adv.getAdvertisementID());
        retract($adv);                   
end

rule "advertisement select rule"
salience -1
	when		
		$adv : Advertisement( $playedPercentPerAdvertisement :
playedPercentPerAdvertisement)		
		not( Advertisement( playedPercentPerAdvertisement <
$playedPercentPerAdvertisement ) )
		$advertisementCount : Integer()						
	then		
		boolean status = true;		
		if($advertisementCount-1 < 0){
			//System.out.println("halted");
			status = false;
			drools.halt();		
		}		
		if(status){			
			feasibleAdv.add($adv);		
			drools.update(
drools.getWorkingMemory().getFactHandle($advertisementCount)
, new
Integer($advertisementCount-1) );
			retract($adv);
		}		
end

</code>
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Can drools work in multithreaded environment?

Thread: Can drools work in multithreaded environment?