For whoever is interested, I determined why StatefulKnowledgeSession.dispose threw an IllegalStateException for a persisted session. The error message refers to the thread, which led me to discover that the dispose would work if it was executed on the same thread where it had been created. The org.springframework.transaction.support.TransactionSynchronizationManager.unbindResource method at the top of the stack trace attempts to look up the resource in ThreadLocal storage. My shutdown hook was running on a different thread, so this lookup was failing.

I used the standard Java wait/notify mechanism to fix this. I now suspend my main thread after it creates the knowledge session with Object.wait. When the shutdown hook thread runs, it calls Object.notifyAll to release the main thread, which then disposes of the session successfully. The rest of my application runs in other threads, so suspending the main thread causes no harm.

I still would appreciate some clarification of how the “Configuring JTA DataSource” code in the documentation is meant to be used.

Thanks,

Tom

From: rules-users-bounces@lists.jboss.org [mailto:rules-users-bounces@lists.jboss.org] On Behalf Of Thomas Grayson
Sent: Wednesday, June 12, 2013 3:42 PM
To: Rules Users List
Subject: [rules-users] IllegalStateException when disposing of a persisted session

We are using Drools persistence with a StatefulKnowledgeSession. The persistence itself works fine, but I am encountering an IllegalStateException when disposing of the StatefulKnowledgeSession. This happens with either a brand new session with no facts or one that has had facts added to it. It also happens with sessions that have been restored from the persistent store. The code does no explicit transaction management and relies on Drools to do this under the covers. We are using Drools 5.5.0 Final. How do I dispose of a session correctly?

The documentation includes Example 3.66, “Configuring JTA DataSource.” My code does not include code like this anywhere. Do I need it? It’s not clear from the example where the PoolingDataSource instance would be used or when this code should be called. If this configuration is required, can it be done via Spring instead of programmatically?

I’ll provide some supporting information below. I’ve edited these excerpts to redact some private details and eliminate distracting code, but the substance is intact.

Here is the stack trace created by invoking the “dispose” method from a shutdown hook:

java.lang.IllegalStateException: No value for key [org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean@732e3e73] bound to thread [Thread-3]

at org.springframework.transaction.support.TransactionSynchronizationManager.unbindResource(TransactionSynchronizationManager.java:209)

at org.drools.container.spring.beans.persistence.DroolsSpringJpaManager.dispose(DroolsSpringJpaManager.java:135)

at org.drools.persistence.SingleSessionCommandService.execute(SingleSessionCommandService.java:345)

at org.drools.command.impl.CommandBasedStatefulKnowledgeSession.dispose(CommandBasedStatefulKnowledgeSession.java:241)

at MyClass1.stop

at MyClass2$1.run

at java.lang.Thread.run(Unknown Source)

The code uses Drools-Spring to configure the knowledge base and Java code to initialize the knowledge session. We’re using JPA, the Bitronix transaction manager, and the H2 database, basically as described in the documentation. Here is the code for creating the session:

ApplicationContext context = new ClassPathXmlApplicationContext(APPLICATION_CONTEXT_XML);

KnowledgeStoreService kstore = (KnowledgeStoreService) context.getBean("myAppKnowledgeStore");

KnowledgeBase kbase = ...; // initialized by Spring configuration

Environment env = KnowledgeBaseFactory.newEnvironment();

env.set(EnvironmentName.ENTITY_MANAGER_FACTORY, context.getBean("entityManagerFactory"));

env.set(EnvironmentName.TRANSACTION_MANAGER, context.getBean("txManager"));

StatefulKnowledgeSession ksession = kstore.newStatefulKnowledgeSession(kbase, null, env);

Here is the relevant portion of the Spring ApplicationContext.xml file:

<bean id="dataSourceH2"

class="org.springframework.jdbc.datasource.DriverManagerDataSource">

</bean>

<bean id="entityManagerFactory"

class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean">

</bean>

</bean>

<drools:grid-node id="myAppEngineNode" />

<drools:kstore id="myAppKnowledgeStore" />

<drools:kbase id="myAppEngineKBase" node="MyAppEngineNode">

<drools:configuration>

<drools:assert-behavior mode="EQUALITY" />

</drools:configuration>

<drools:resources>

<drools:resource type="DRL" source="classpath:MyAppInternalRules.drl" />

<drools:resource type="DTABLE" source="classpath:MyAppRules.xls" >

<drools:decisiontable-conf input-type="XLS" worksheet-name="Sheet 1" />

</drools:resource>

<drools:resource type="DTABLE" source="classpath:MyAppRules.xls" >

<drools:decisiontable-conf input-type="XLS" worksheet-name="Sheet 2" />

</drools:resource>

</drools:resources>

</drools:kbase>

Here is the relevant part of the persistence.xml file:

<persistence-unit name="myAppH2">

<provider>org.hibernate.ejb.HibernatePersistence</provider>

<class>org.drools.persistence.info.SessionInfo</class>

</properties>

</persistence-unit>

I have a jndi.properties that’s identical to what’s in the documentation.

I noticed in the documentation (Example 3.65, Configuring JPA) that the persistence-unit block is defined a bit differently. In particular, transaction-type is specified and a jta-data-source are defined, unlike in my file:

<persistence-unit name="org.drools.persistence.jpa" transaction-type="JTA">

<provider>org.hibernate.ejb.HibernatePersistence</provider>

<jta-data-source>jdbc/BitronixJTADataSource</jta-data-source>

...

</persistence-unit>

I tried defining these as shown, but then the code failed on startup when it tried to create a transaction:

org.drools.container.spring.beans.persistence.DroolsSpringTransactionManager: Unable to begin transaction

org.springframework.transaction.CannotCreateTransactionException: Could not open JPA EntityManager for transaction; nested exception is java.lang.IllegalStateException: A JTA EntityManager cannot use getTransaction()

at org.springframework.orm.jpa.JpaTransactionManager.doBegin(JpaTransactionManager.java:427)

at org.springframework.transaction.support.AbstractPlatformTransactionManager.getTransaction(AbstractPlatformTransactionManager.java:371)

at org.drools.container.spring.beans.persistence.DroolsSpringTransactionManager.begin(DroolsSpringTransactionManager.java:48)

at org.drools.persistence.SingleSessionCommandService.<init>(SingleSessionCommandService.java:190)

at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)

at sun.reflect.NativeConstructorAccessorImpl.newInstance(Unknown Source)

at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source)

at java.lang.reflect.Constructor.newInstance(Unknown Source)

at org.drools.persistence.jpa.KnowledgeStoreServiceImpl.buildCommandService(KnowledgeStoreServiceImpl.java:100)

at org.drools.persistence.jpa.KnowledgeStoreServiceImpl.loadStatefulKnowledgeSession(KnowledgeStoreServiceImpl.java:83)

at MyClass1.initializeKnowledgeSession

at MyClass1.initializeKnowledgeEngine

at MyClass2.main

Caused by: java.lang.IllegalStateException: A JTA EntityManager cannot use getTransaction()

at org.hibernate.ejb.AbstractEntityManagerImpl.getTransaction(AbstractEntityManagerImpl.java:996)

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

at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)

at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)

at java.lang.reflect.Method.invoke(Unknown Source)

at org.springframework.orm.jpa.ExtendedEntityManagerCreator$ExtendedEntityManagerInvocationHandler.invoke(ExtendedEntityManagerCreator.java:365)

at com.sun.proxy.$Proxy16.getTransaction(Unknown Source)

at org.springframework.orm.jpa.DefaultJpaDialect.beginTransaction(DefaultJpaDialect.java:70)

at org.springframework.orm.jpa.JpaTransactionManager.doBegin(JpaTransactionManager.java:377)

... 12 more

Thanks,

Tom