Maciej, thanks.

I did more tests in recent days. Virtually I used the Websphere application server. I did not observe the obvious memory leak. I tested the Evaluation sample using two different accessing ways: one used remote API, and another used common java api(directly calling jbpm api, just like embedded mode). Under the same workload, the common java api was much faster than remote API. Even when I just used one thread to circularly execute the complete evalation process (start process, complete tasks) 200 times, I observed each later operation costed at least over 10s, and the test lasted over 3 hours. So I suspect the jaxb conversion and REST communication over HTTP caused the issue.

BTW I wonder if there is EJB api for the remote interaction. is it on your roadmap?

Thank you for your response.

I followed your post and give the ejb services a try on WebSphere 8.5. But I faced the following error when starting the kie-wb which was packed in an ear named WFE(workflow engine, only has one module). Kindly note I have put the ejb-related service jars in kie-wb war. It seemed like the Websphere does not allow to inject UserTransaction for ejb CMP.

Caused by: com.ibm.ejs.container.ContainerException: Failed to start the TransactionalCommandServiceEJBImpl component in the kie-wb.war module of the server1_WFE application. : An operation in the enterprise bean constructor failed. It is recommended that component initialization logic be placed in a PostConstruct method instead of the bean class no-arg constructor.; nested exception is:

  java.lang.IllegalStateException: Unable to find transaction: Exception occurred while the JNDI NamingManager was processing a javax.naming.Reference object.

  at com.ibm.ws.ejbcontainer.runtime.SharedEJBRuntimeImpl.startBean(SharedEJBRuntimeImpl.java:609)

  at com.ibm.ws.runtime.component.WASEJBRuntimeImpl.startBean(WASEJBRuntimeImpl.java:583)

  at com.ibm.ws.ejbcontainer.runtime.AbstractEJBRuntime.fireMetaDataCreatedAndStartBean(AbstractEJBRuntime.java:1716)

  at com.ibm.ws.ejbcontainer.runtime.AbstractEJBRuntime.initializeDeferredEJBImpl(AbstractEJBRuntime.java:1607)

  at com.ibm.ws.ejbcontainer.runtime.SharedEJBRuntimeImpl.initializeDeferredEJBImpl(SharedEJBRuntimeImpl.java:545)

  at com.ibm.ws.ejbcontainer.runtime.AbstractEJBRuntime$1$1.run(AbstractEJBRuntime.java:1501)

  at com.ibm.ws.ejbcontainer.runtime.AbstractEJBRuntime$1$1.run(AbstractEJBRuntime.java:1495)

  at com.ibm.ws.security.auth.ContextManagerImpl.runAs(ContextManagerImpl.java:5474)

  at com.ibm.ws.security.auth.ContextManagerImpl.runAsSystem(ContextManagerImpl.java:5600)

  at com.ibm.ws.security.core.SecurityContext.runAsSystem(SecurityContext.java:255)

  at com.ibm.ws.ejbcontainer.runtime.AbstractEJBRuntime$1.run(AbstractEJBRuntime.java:1494)

  ... 37 more

Caused by: java.lang.IllegalStateException: Unable to find transaction: Exception occurred while the JNDI NamingManager was processing a javax.naming.Reference object.

  at org.drools.persistence.jta.JtaTransactionManager.findUserTransaction(JtaTransactionManager.java:139)

  at org.drools.persistence.jta.JtaTransactionManager.<init>(JtaTransactionManager.java:79)

  at org.jbpm.shared.services.impl.TransactionalCommandService.<init>(TransactionalCommandService.java:23)

  at org.jbpm.services.ejb.impl.tx.TransactionalCommandServiceEJBImpl.<init>(TransactionalCommandServiceEJBImpl.java:37)

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

  at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:56)

  at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:39)

  at java.lang.reflect.Constructor.newInstance(Constructor.java:527)

  at com.ibm.ws.ejbcontainer.runtime.SharedEJBRuntimeImpl.startBean(SharedEJBRuntimeImpl.java:577)

  ... 47 more

Caused by: com.ibm.websphere.naming.CannotInstantiateObjectException: Exception occurred while the JNDI NamingManager was processing a javax.naming.Reference object. [Root exception is com.ibm.wsspi.injectionengine.InjectionException: UserTransaction may only be looked up by or injected into an EJB if that EJB is configured to use bean managed transactions.  EJB server1_WFE#kie-wb.war#TransactionalCommandServiceEJBImpl is configured for container managed transactions.]

  at com.ibm.ws.naming.util.Helpers.processSerializedObjectForLookupExt(Helpers.java:1103)

  at com.ibm.ws.naming.urlbase.UrlContextHelper.processBoundObjectForLookup(UrlContextHelper.java:181)

  at com.ibm.ws.naming.java.javaURLContextRoot.processBoundObjectForLookup(javaURLContextRoot.java:850)

  at com.ibm.ws.naming.urlbase.UrlContextImpl.lookupExt(UrlContextImpl.java:1454)

  at com.ibm.ws.naming.java.javaURLContextImpl.lookupExt(javaURLContextImpl.java:477)

  at com.ibm.ws.naming.java.javaURLContextRoot.lookupExt(javaURLContextRoot.java:485)

  at com.ibm.ws.naming.java.javaURLContextRoot.lookup(javaURLContextRoot.java:370)

  at org.apache.aries.jndi.DelegateContext.lookup(DelegateContext.java:161)

  at javax.naming.InitialContext.lookup(InitialContext.java:436)

  at org.drools.persistence.jta.JtaTransactionManager.findUserTransaction(JtaTransactionManager.java:131)

  ... 55 more

Caused by: com.ibm.wsspi.injectionengine.InjectionException: UserTransaction may only be looked up by or injected into an EJB if that EJB is configured to use bean managed transactions.  EJB server1_WFE#kie-wb.war#TransactionalCommandServiceEJBImpl is configured for container managed transactions.

  at com.ibm.ws.ejbcontainer.injection.factory.HybridUserTransactionObjectFactory.getObjectInstance(HybridUserTransactionObjectFactory.java:96)

  at org.apache.aries.jndi.ObjectFactoryHelper.getObjectInstanceUsingObjectFactoryBuilders(ObjectFactoryHelper.java:349)

  at org.apache.aries.jndi.ObjectFactoryHelper.getObjectInstance(ObjectFactoryHelper.java:89)

  at org.apache.aries.jndi.OSGiObjectFactoryBuilder.getObjectInstance(OSGiObjectFactoryBuilder.java:57)

  at javax.naming.spi.NamingManager.getObjectInstance(NamingManager.java:349)

  at com.ibm.ws.naming.util.Helpers.processSerializedObjectForLookupExt(Helpers.java:993)

  ... 64 more

so I changed the TransactionalCommandServiceEJBImpl no-arg constructor 

public TransactionalCommandServiceEJBImpl() {

  super();//don't pass arg to prohibit super class to call findUserTransaction

  // entity manager will be set by setter method

  }

and add a no-arg constructor to its parent class, TransactionalCommandService.java. Now the application can start. but NPE is throwed because there is not txm. Any suggestions?