Hi all,

We're evaluating the use of Drools Fusion as rule engine for one of our projects, but after updating from version 5.0.1 to 5.1.0 to fix one persistence issue we faced new errors and some unexpected behavior changes in already tested parts of our code, and we aren't unsure if it's our fault due to incorrect assumptions or if it's resulting from a new bug introduced in last release. Here follows what we are doing:

1) we declared this in our Test_Rules.drl:

declare UserEvent

@role( event )

@expires( 30s )

end

query "get user by login" (String login)

user : UserEvent(user.login == login)

end

2) this is the code we use to retrieve the Drools session (implemented in a singleton):

public StatefulKnowledgeSession getKnowledgeSessionInstance() {

if (session == null) {

kbase = readKnowledgeBase();

KnowledgeSessionConfiguration conf = KnowledgeBaseFactory.newKnowledgeSessionConfiguration();

session = kbase.newStatefulKnowledgeSession(conf, null);

}

return session;

}

3) that's how we load the rules (some non-pertinent code was omitted):

private KnowledgeBase readKnowledgeBase() {

KnowledgeBuilder kbuilder = KnowledgeBuilderFactory.newKnowledgeBuilder();

KnowledgeBaseConfiguration config = KnowledgeBaseFactory.newKnowledgeBaseConfiguration();

config.setOption(EventProcessingOption.STREAM);

kbuilder.add(ResourceFactory.newClassPathResource("Test_Rules.drl"), ResourceType.DRL);

KnowledgeBuilderErrors errors = kbuilder.getErrors();

if (errors.size() > 0) {

// (...)

throw new IllegalArgumentException("Could not parse knowledge.");

}

KnowledgeBase kbase = KnowledgeBaseFactory.newKnowledgeBase(config);

kbase.addKnowledgePackages(kbuilder.getKnowledgePackages());

return kbase;

}

(NOTE: Up to this point the code behaves exactly the same way in both versions and everything works as expected.)

4) in this method we check our event expiration, and that's where things starts to behave different. In version 5.0.1, the code always worked in the same way, returning a null reference to userValidation if the expiration time is reached. Also, handleQuery is always an instance of EventFactHandle. Based in userValidation reference being null or not, we either retrieve it or update it. Again, non-related code was ommited:

private UserTrackForValidation assertDesktopEvent(DesktopDeviceEvent event) {

UserEvent userValidation = null;

StatefulKnowledgeSession session = sessionFactory.getKnowledgeSessionInstance(createEnviroment());

QueryResults results = session.getQueryResults("get user by login", new String[] {event.getLogin()});

if (results.size() > 0) {

QueryResultsRow row = results.iterator().next();

FactHandle handleQuery = row.getFactHandle("user");

userValidation = (UserTrackForValidation) row.get("user");

}

if (userValidation == null) {

try {

userValidation = entityDAO.getUserTrackByLogin(event.getLogin());

} catch (Exception e) {

e.printStackTrace();

}

// (...)

}

else {

// (...)

session.update(handleQuery, userValidation);

session.fireAllRules();

}

return userValidation;

}

However, starting with version 5.1.0, we observed some odd behaviors:

a) after time expiration, we may or may not receive a null reference to userValidation, which renders the test line "if (userValidation == null)" erratic;

b) even when we receive a (as far as we can tell) valid reference to userValidation, sometimes a NullPointerException is raised, as can be seen in the following stacktrace:

java.lang.NullPointerException

at org.drools.common.AbstractWorkingMemory.update(AbstractWorkingMemory.java:1329)

at org.drools.common.AbstractWorkingMemory.update(AbstractWorkingMemory.java:1288)

at org.drools.impl.StatefulKnowledgeSessionImpl.update(StatefulKnowledgeSessionImpl.java:248)

at br.com.todobpo.lam.ejb.session.ContactCenterRuleServiceImpl.assertSimpleEvent(ContactCenterRuleServiceImpl.java:191)

at br.com.todobpo.lam.ejb.session.ContactCenterRuleServiceImpl.insertEvent(ContactCenterRuleServiceImpl.java:89)

at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)

at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)

at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)

at java.lang.reflect.Method.invoke(Method.java:597)

at org.jboss.aop.joinpoint.MethodInvocation.invokeTarget(MethodInvocation.java:122)

at org.jboss.aop.joinpoint.MethodInvocation.invokeNext(MethodInvocation.java:111)

at org.jboss.ejb3.EJBContainerInvocationWrapper.invokeNext(EJBContainerInvocationWrapper.java:69)

at org.jboss.ejb3.interceptors.aop.InterceptorSequencer.invoke(InterceptorSequencer.java:73)

at org.jboss.ejb3.interceptors.aop.InterceptorSequencer.aroundInvoke(InterceptorSequencer.java:59)

at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)

at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)

at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)

at java.lang.reflect.Method.invoke(Method.java:597)

at org.jboss.aop.advice.PerJoinpointAdvice.invoke(PerJoinpointAdvice.java:174)

at org.jboss.aop.joinpoint.MethodInvocation.invokeNext(MethodInvocation.java:102)

at org.jboss.ejb3.interceptors.aop.InvocationContextInterceptor.fillMethod(InvocationContextInterceptor.java:72)

at org.jboss.aop.advice.org.jboss.ejb3.interceptors.aop.InvocationContextInterceptor_z_fillMethod_1000702.invoke(InvocationContextInterceptor_z_fillMethod_1000702.java)

at org.jboss.aop.joinpoint.MethodInvocation.invokeNext(MethodInvocation.java:102)

at org.jboss.ejb3.interceptors.aop.InvocationContextInterceptor.setup(InvocationContextInterceptor.java:88)

at org.jboss.aop.advice.org.jboss.ejb3.interceptors.aop.InvocationContextInterceptor_z_setup_1000702.invoke(InvocationContextInterceptor_z_setup_1000702.java)

at org.jboss.aop.joinpoint.MethodInvocation.invokeNext(MethodInvocation.java:102)

at org.jboss.ejb3.connectionmanager.CachedConnectionInterceptor.invoke(CachedConnectionInterceptor.java:62)

at org.jboss.aop.joinpoint.MethodInvocation.invokeNext(MethodInvocation.java:102)

at org.jboss.ejb3.entity.TransactionScopedEntityManagerInterceptor.invoke(TransactionScopedEntityManagerInterceptor.java:56)

at org.jboss.aop.joinpoint.MethodInvocation.invokeNext(MethodInvocation.java:102)

at org.jboss.ejb3.AllowedOperationsInterceptor.invoke(AllowedOperationsInterceptor.java:47)

at org.jboss.aop.joinpoint.MethodInvocation.invokeNext(MethodInvocation.java:102)

at org.jboss.ejb3.tx.StatelessBMTInterceptor.handleInvocation(StatelessBMTInterceptor.java:106)

at org.jboss.ejb3.tx.BMTInterceptor.invoke(BMTInterceptor.java:55)

at org.jboss.aop.joinpoint.MethodInvocation.invokeNext(MethodInvocation.java:102)

at org.jboss.ejb3.stateless.StatelessInstanceInterceptor.invoke(StatelessInstanceInterceptor.java:68)

at org.jboss.aop.joinpoint.MethodInvocation.invokeNext(MethodInvocation.java:102)

at org.jboss.ejb3.tx.NullInterceptor.invoke(NullInterceptor.java:42)

at org.jboss.aop.joinpoint.MethodInvocation.invokeNext(MethodInvocation.java:102)

at org.jboss.aspects.tx.TxPropagationInterceptor.invoke(TxPropagationInterceptor.java:76)

at org.jboss.aop.joinpoint.MethodInvocation.invokeNext(MethodInvocation.java:102)

at org.jboss.ejb3.tx.NullInterceptor.invoke(NullInterceptor.java:42)

at org.jboss.aop.joinpoint.MethodInvocation.invokeNext(MethodInvocation.java:102)

at org.jboss.ejb3.security.Ejb3AuthenticationInterceptorv2.invoke(Ejb3AuthenticationInterceptorv2.java:186)

at org.jboss.aop.joinpoint.MethodInvocation.invokeNext(MethodInvocation.java:102)

at org.jboss.ejb3.ENCPropagationInterceptor.invoke(ENCPropagationInterceptor.java:41)

at org.jboss.aop.joinpoint.MethodInvocation.invokeNext(MethodInvocation.java:102)

at org.jboss.ejb3.BlockContainerShutdownInterceptor.invoke(BlockContainerShutdownInterceptor.java:67)

at org.jboss.aop.joinpoint.MethodInvocation.invokeNext(MethodInvocation.java:102)

at org.jboss.aspects.currentinvocation.CurrentInvocationInterceptor.invoke(CurrentInvocationInterceptor.java:67)

at org.jboss.aop.joinpoint.MethodInvocation.invokeNext(MethodInvocation.java:102)

at org.jboss.ejb3.stateless.StatelessContainer.dynamicInvoke(StatelessContainer.java:421)

at org.jboss.ejb3.session.InvokableContextClassProxyHack._dynamicInvoke(InvokableContextClassProxyHack.java:53)

at org.jboss.aop.Dispatcher.invoke(Dispatcher.java:91)

at org.jboss.aspects.remoting.AOPRemotingInvocationHandler.invoke(AOPRemotingInvocationHandler.java:82)

at org.jboss.remoting.ServerInvoker.invoke(ServerInvoker.java:891)

at org.jboss.remoting.transport.socket.ServerThread.completeInvocation(ServerThread.java:744)

at org.jboss.remoting.transport.socket.ServerThread.processInvocation(ServerThread.java:697)

at org.jboss.remoting.transport.socket.ServerThread.dorun(ServerThread.java:524)

at org.jboss.remoting.transport.socket.ServerThread.run(ServerThread.java:232)

at org.jboss.remoting.MicroRemoteClientInvoker.invoke(MicroRemoteClientInvoker.java:211)

at org.jboss.remoting.Client.invoke(Client.java:1724)

at org.jboss.remoting.Client.invoke(Client.java:629)

at org.jboss.aspects.remoting.InvokeRemoteInterceptor.invoke(InvokeRemoteInterceptor.java:60)

at org.jboss.aop.joinpoint.MethodInvocation.invokeNext(MethodInvocation.java:102)

at org.jboss.aspects.tx.ClientTxPropagationInterceptor.invoke(ClientTxPropagationInterceptor.java:61)

at org.jboss.aop.joinpoint.MethodInvocation.invokeNext(MethodInvocation.java:102)

at org.jboss.ejb3.security.client.SecurityClientInterceptor.invoke(SecurityClientInterceptor.java:65)

at org.jboss.aop.joinpoint.MethodInvocation.invokeNext(MethodInvocation.java:102)

at org.jboss.ejb3.remoting.IsLocalInterceptor.invoke(IsLocalInterceptor.java:74)

at org.jboss.aop.joinpoint.MethodInvocation.invokeNext(MethodInvocation.java:102)

at org.jboss.aspects.remoting.PojiProxy.invoke(PojiProxy.java:62)

at $Proxy7.invoke(Unknown Source)

at org.jboss.ejb3.proxy.impl.handler.session.SessionProxyInvocationHandlerBase.invoke(SessionProxyInvocationHandlerBase.java:207)

at org.jboss.ejb3.proxy.impl.handler.session.SessionProxyInvocationHandlerBase.invoke(SessionProxyInvocationHandlerBase.java:164)

at $Proxy6.insertEvent(Unknown Source)

at br.com.todobpo.lam.ejb.test.Authenticate.authenticationOk(Authenticate.java:70)

at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)

at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)

at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)

at java.lang.reflect.Method.invoke(Method.java:597)

at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:44)

at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:15)

at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:41)

at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:20)

at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:76)

at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:50)

at org.junit.runners.ParentRunner$3.run(ParentRunner.java:193)

at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:52)

at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:191)

at org.junit.runners.ParentRunner.access$000(ParentRunner.java:42)

at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:184)

at org.junit.runners.ParentRunner.run(ParentRunner.java:236)

at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:46)

at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)

at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:467)

at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:683)

at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:390)

at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:197)

at org.jboss.aspects.remoting.InvokeRemoteInterceptor.invoke(InvokeRemoteInterceptor.java:72)