[droolsflow] Multiple Instances
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Can the constraint for an EventWait node in a flow be code-based (rather than rule-based)? The Eclipse plug-in (v 5.0.1) doesn't allow this to be specified, unlike say for a Split node, although the relevant XML can of course be edited. Trying to load such a process flow results in a NullPointerException, because the constraint is always interpreted as a rule. Ideally what I'd like to do is have an EventWait node where the constraint tests the value of a process variable. This then leads me to another question; is there a way of setting the value of a process variable via the Drools Flow API? Thanks in advance for any help, Alan Tessella plc
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In reply to this post
by Anderson vasconcelos
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In reply to this post
by gairey
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Kris, I've attached a simple test case (transaction manager, data source, etc. are configured via Spring). The error is thrown on line: ksession.insert(new SimpleFact()); If this line is commented out, the rule flow executes without error. Many thanks for looking at this. Regards, Alan
Alan, Could you send me the entire output / stack trace (as the rollback of the transaction is usually caused by another exception)? Or a simple test case that shows the error, so I can take a look? Thx, Kris Quoting [hidden email]: > Kris, > > After posting my last question, I quickly came to the same conclusion > as > you, so I'm now using a rule-based constraint in my EventWait node. > > This however has presented a different problem. If I create my > session > from JPAKnowledgeService, then when I try to insert my fact into the > > session, I get the following error: > > bitronix.tm.internal.BitronixRollbackException: transaction was > marked as > rollback only and has been rolled back > at > bitronix.tm.BitronixTransaction.commit(BitronixTransaction.java:153) > at > bitronix.tm.BitronixTransactionManager.commit(BitronixTransactionManager.java:96) > at > org.drools.persistence.session.SingleSessionCommandService.execute(SingleSessionCommandService.java:258) > at > org.drools.command.impl.CommandBasedStatefulKnowledgeSession.insert(CommandBasedStatefulKnowledgeSession.java:305) > (Everything works fine if I create my session from the knowledge base > - > i.e. with no state persistence.) > Prior to using a rule-based constraint (with no call to > CommandBasedStatefulKnowledgeSession.insert), the session created > from > JPAKnowledgeService worked OK. > I'm using the default JPA configuration from the Drools documentation > > (persisting to H2 database, etc.). > Any ideas what might be causing the problem? > Many thanks, > Alan > > > > > Kris Verlaenen <[hidden email]> > 23/10/2009 03:00 > > To > Rules Users List <[hidden email]>, > [hidden email] > cc > Rules Users List <[hidden email]> > Subject > Re: [rules-users] [droolsflow] Code-based constraints for EventWait > nodes > - is this possible? > > > > > > > No, the constraint of an EventWait node (or the State node in Drools > 5.1) can only be rule-based. The reason for this is that the rule > engine knows when to re-evaluates rules (based on the evailable > input). > If you would use a code-based constraint, the engine would have no > idea > when this code constraint might become true (if it was false at the > start). Only constant re-evaluation of the code constraint could > achieve this (which would be tremendously inefficient). Could you > explain why you would like to have this behaviour? Maybe there is > an > alternative way to model this. > > To change the value of a variable from inside the process (using an > action), simply use kcontext.setVariable(name, value). We do not > recommend manually changing the value of a process variable from > outside > the engine. Again, could you explain why you would like to have > this > functionality? > > Kris > > Quoting [hidden email]: > > > Can the constraint for an EventWait node in a flow be code-based > > (rather > > than rule-based)? The Eclipse plug-in (v 5.0.1) doesn't allow this > to > > be > > specified, unlike say for a Split node, although the relevant XML > can > > of > > course be edited. > > Trying to load such a process flow results in a > NullPointerException, > > > > because the constraint is always interpreted as a rule. > > > > Ideally what I'd like to do is have an EventWait node where the > > constraint > > tests the value of a process variable. This then leads me to > another > > > > question; is there a way of setting the value of a process > variable > > via > > the Drools Flow API? > > > > Thanks in advance for any help, > > > > Alan > > Tessella plc > > 26 The Quadrant, Abingdon Science Park, Abingdon, Oxfordshire, > OX14 > > 3YS > > E: [hidden email], T: +44 (0)1235 555511, F: +44 (0)1235 > > 553301 > > www.tessella.com Registered in England No. 1466429 > > > > This message is commercial in confidence and may be privileged. It > is > > > > intended for the addressee(s) only. Access to this message by > anyone > > else > > is unauthorized and strictly prohibited. If you have received this > > message > > in error, please inform the sender immediately. Please note that > > messages > > sent or received by the Tessella e-mail system may be monitored > and > > stored > > in an information retrieval system. > > > > > > > Disclaimer: http://www.kuleuven.be/cwis/email_disclaimer.htm > > Disclaimer: http://www.kuleuven.be/cwis/email_disclaimer.htm _______________________________________________ rules-users mailing list [hidden email] https://lists.jboss.org/mailman/listinfo/rules-users |
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drools-persistence-test.zip (7K) |
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Kris, Thanks - making the class SimpleFact serializable fixed that error. However, I now have a new problem: I have a rule flow containing a work item - the handler attempts to update the SimpleFact instance in memory before completing the task. The code in the executeWorkItem method is as follows: Collection<FactHandle> factHandles = ksession.getFactHandles(new ObjectFilter() { public boolean accept(Object object) { return (object instanceof SimpleFact); } }); for (Iterator<FactHandle> iterator = factHandles.iterator(); iterator.hasNext(); ) { FactHandle factHandle = iterator.next(); SimpleFact fact = (SimpleFact) ksession.getObject(factHandle); fact.setStatus("Error"); ksession.update(factHandle, fact); } workItemManager.completeWorkItem(workItem.getId(), null); The call to getObject() causes the following exception to be thrown: java.lang.NullPointerException at org.drools.command.runtime.rule.GetObjectCommand.execute(GetObjectCommand.java:35) at org.drools.persistence.session.SingleSessionCommandService.execute(SingleSessionCommandService.java:254) at org.drools.command.impl.CommandBasedStatefulKnowledgeSession.getObject(CommandBasedStatefulKnowledgeSession.java:369) at com.test.StatusChangeWorkItemHandler.executeWorkItem(StatusChangeWorkItemHandler.java:37) ... I've attached another test case to illustrate the problem. Once again, my sincere thanks for helping me with this. Regards, Alan
Alan, The cause of the rollback of the transaction is this: Caused by: java.io.NotSerializableException: com.test.SimpleFact The reason is that, if you use persistence for your session, the persister will try to save all runtime state of the engine. This does not only include process instances, but also rule-related state. By default, this also includes the data inserted in the memory. We support two strategies for storing this data: serialization of the data (default) or JPA-based storage of entities (by reference). In this case, the persister is trying to serialize the test object you inserted and fails. Making it serializable should fix this. Kris Quoting [hidden email]: > Kris, > > I've attached a simple test case (transaction manager, data source, > etc. > are configured via Spring). The error is thrown on line: > > ksession.insert(new SimpleFact()); > > If this line is commented out, the rule flow executes without error. > > > > Many thanks for looking at this. > > Regards, > > Alan > > > > > Kris Verlaenen <[hidden email]> > 28/10/2009 10:40 > > To > [hidden email] > cc > Rules Users List <[hidden email]> > Subject > Re: [rules-users] [droolsflow] Code-based constraints for EventWait > nodes > - is this possible? > > > > > > > Alan, > > Could you send me the entire output / stack trace (as the rollback > of > the transaction is usually caused by another exception)? > > Or a simple test case that shows the error, so I can take a look? > > Thx, > Kris > > Quoting [hidden email]: > > > Kris, > > > > After posting my last question, I quickly came to the same > conclusion > > as > > you, so I'm now using a rule-based constraint in my EventWait > node. > > > > This however has presented a different problem. If I create my > > session > > from JPAKnowledgeService, then when I try to insert my fact into > the > > > > session, I get the following error: > > > > bitronix.tm.internal.BitronixRollbackException: transaction was > > marked as > > rollback only and has been rolled back > > at > > > bitronix.tm.BitronixTransaction.commit(BitronixTransaction.java:153) > > at > > > bitronix.tm.BitronixTransactionManager.commit(BitronixTransactionManager.java:96) > > at > > > org.drools.persistence.session.SingleSessionCommandService.execute(SingleSessionCommandService.java:258) > > at > > > org.drools.command.impl.CommandBasedStatefulKnowledgeSession.insert(CommandBasedStatefulKnowledgeSession.java:305) > > (Everything works fine if I create my session from the knowledge > base > > - > > i.e. with no state persistence.) > > Prior to using a rule-based constraint (with no call to > > CommandBasedStatefulKnowledgeSession.insert), the session created > > from > > JPAKnowledgeService worked OK. > > I'm using the default JPA configuration from the Drools > documentation > > > > (persisting to H2 database, etc.). > > Any ideas what might be causing the problem? > > Many thanks, > > Alan > > > > > > > > > > Kris Verlaenen <[hidden email]> > > 23/10/2009 03:00 > > > > To > > Rules Users List <[hidden email]>, > > [hidden email] > > cc > > Rules Users List <[hidden email]> > > Subject > > Re: [rules-users] [droolsflow] Code-based constraints for > EventWait > > nodes > > - is this possible? > > > > > > > > > > > > > > No, the constraint of an EventWait node (or the State node in > Drools > > 5.1) can only be rule-based. The reason for this is that the rule > > engine knows when to re-evaluates rules (based on the evailable > > input). > > If you would use a code-based constraint, the engine would have > no > > idea > > when this code constraint might become true (if it was false at > the > > start). Only constant re-evaluation of the code constraint could > > achieve this (which would be tremendously inefficient). Could you > > explain why you would like to have this behaviour? Maybe there is > > an > > alternative way to model this. > > > > To change the value of a variable from inside the process (using > an > > action), simply use kcontext.setVariable(name, value). We do not > > recommend manually changing the value of a process variable from > > outside > > the engine. Again, could you explain why you would like to have > > this > > functionality? > > > > Kris > > > > Quoting [hidden email]: > > > > > Can the constraint for an EventWait node in a flow be code-based > > > (rather > > > than rule-based)? The Eclipse plug-in (v 5.0.1) doesn't allow > this > > to > > > be > > > specified, unlike say for a Split node, although the relevant > XML > > can > > > of > > > course be edited. > > > Trying to load such a process flow results in a > > NullPointerException, > > > > > > because the constraint is always interpreted as a rule. > > > > > > Ideally what I'd like to do is have an EventWait node where the > > > constraint > > > tests the value of a process variable. This then leads me to > > another > > > > > > question; is there a way of setting the value of a process > > variable > > > via > > > the Drools Flow API? > > > > > > Thanks in advance for any help, > > > > > > Alan > > > Tessella plc > > > 26 The Quadrant, Abingdon Science Park, Abingdon, Oxfordshire, > > OX14 > > > 3YS > > > E: [hidden email], T: +44 (0)1235 555511, F: +44 > (0)1235 > > > 553301 > > > www.tessella.com Registered in England No. 1466429 > > > > > > This message is commercial in confidence and may be privileged. > It > > is > > > > > > intended for the addressee(s) only. Access to this message by > > anyone > > > else > > > is unauthorized and strictly prohibited. If you have received > this > > > message > > > in error, please inform the sender immediately. Please note that > > > messages > > > sent or received by the Tessella e-mail system may be monitored > > and > > > stored > > > in an information retrieval system. > > > > > > > > > > > > > Disclaimer: http://www.kuleuven.be/cwis/email_disclaimer.htm > > > > > > > > > Disclaimer: http://www.kuleuven.be/cwis/email_disclaimer.htm > > Disclaimer: http://www.kuleuven.be/cwis/email_disclaimer.htm _______________________________________________ rules-users mailing list [hidden email] https://lists.jboss.org/mailman/listinfo/rules-users |
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In reply to this post
by gairey
Kris, Thanks yes - the null check fixes the NPE I was seeing. Unfortunately, I now have a more difficult problem. In my work item handler, I use the following code to get the ID of a work item in the rule flow (i.e. the .rf file itself) given a org.drools.runtime.process.WorkItem instance: private long getCurrentNodeId(WorkItem workItem) { ProcessInstance processInstance = ksession.getProcessInstance(workItem.getProcessInstanceId()); if (processInstance instanceof WorkflowProcessInstanceImpl) { Collection<NodeInstance> nodeInstances = ((WorkflowProcessInstanceImpl) processInstance).getNodeInstances(); for (NodeInstance nodeInstance : nodeInstances) { System.out.println(String.format("Node instance: %s", nodeInstance)); if (nodeInstance instanceof WorkItemNodeInstance) { WorkItemNodeInstance workItemNodeInstance = (WorkItemNodeInstance) nodeInstance; if (workItemNodeInstance.getWorkItem() == workItem) { return workItemNodeInstance.getNodeId(); } } } } throw new RuntimeException(String.format("Error determining node ID for work item: %s", workItem.toString())); } The work item in the attached test case, the first time it executes sets a property on a fact in memory that causes a subsequent Split node to send the flow to an Event Wait. The code in the overall main() method (in PersistenceTest.java) then updates the fact in memory so that the Event Wait's constraint is satisfied, and the work item node is executed again. The second time around, it sets the property on the fact in memory so that the subsequent Split node sends the flow to its end. (I hope this makes sense; looking at the rule flow in the test case should show you what I'm trying to do.)
If I execute the test case with my session created using the code: StatefulKnowledgeSession ksession = kbase.newStatefulKnowledgeSession(); everything works as I would expect, and the output from the System.out.println() statement in my getCurrentNodeId() method above is: Node instance: org.drools.workflow.instance.node.WorkItemNodeInstance@125d568
StatefulKnowledgeSession ksession = JPAKnowledgeService.newStatefulKnowledgeSession(kbase, null, env); then the RuntimeException in getCurrentNodeId() is thrown, and the output is: Node instance: org.drools.workflow.instance.node.WorkItemNodeInstance@2209db
Somehow it seems as though the node instance isn't quite synchronised with the overall state when using JPA persistence. Any help you could give me here would be very much appreciated. Regards, Alan
Alan, Thanks, this indeed seems to be the issue. I have changed this on trunk. Does adding this null check solve your issue? Thx, Kris Quoting [hidden email]: > Kris, > > Some more information: the NullPointerException from GetObjectCommand > is > thrown by the line: > > > ((StatefulKnowledgeSessionImpl)ksession).session.getExecutionResult().getResults().put( > > this.outIdentifier, > object ); > > Method getExecutionResult() is returning null. Debugging my test > case, I > also notice that this.outIdentifier is also null. > > I then had a look at the GetObjectsCommand class; in its execute > method, > there is a line similar to that above. However, it is contained > within an > if block that checks this.outIdentifier is not null: > > if ( this.outIdentifier != null ) { > List objects = new ArrayList( col ); > > > ((StatefulKnowledgeSessionImpl)ksession).session.getExecutionResult().getResults().put( > > this.outIdentifier, objects ); > } > > If something similar was done in GetObjectCommand, presumably this > would > fix my problem? > > Hope this is of some use - regards, > > Alan > > > > > [hidden email] > Sent by: [hidden email] > 29/10/2009 17:35 > Please respond to > Rules Users List <[hidden email]> > > > To > Kris Verlaenen <[hidden email]> > cc > Rules Users List <[hidden email]> > Subject > Re: [rules-users] [droolsflow] Code-based constraints for EventWait > nodes > - is this possible? > > > > > > > > Kris, > > Thanks - making the class SimpleFact serializable fixed that error. > > However, I now have a new problem: I have a rule flow containing a > work > item - the handler attempts to update the SimpleFact instance in > memory > before completing the task. The code in the executeWorkItem method is > as > follows: > > Collection<FactHandle> factHandles = > ksession.getFactHandles(new > ObjectFilter() { > public boolean accept(Object object) { > return (object instanceof SimpleFact); > } > }); > for (Iterator<FactHandle> iterator = factHandles.iterator(); > > iterator.hasNext(); ) { > FactHandle factHandle = iterator.next(); > SimpleFact fact = (SimpleFact) > ksession.getObject(factHandle); > > fact.setStatus("Error"); > ksession.update(factHandle, fact); > } > > workItemManager.completeWorkItem(workItem.getId(), null); > > The call to getObject() causes the following exception to be thrown: > > > java.lang.NullPointerException > at > org.drools.command.runtime.rule.GetObjectCommand.execute(GetObjectCommand.java:35) > > > at > org.drools.persistence.session.SingleSessionCommandService.execute(SingleSessionCommandService.java:254) > > > at > org.drools.command.impl.CommandBasedStatefulKnowledgeSession.getObject(CommandBasedStatefulKnowledgeSession.java:369) > > > at > com.test.StatusChangeWorkItemHandler.executeWorkItem(StatusChangeWorkItemHandler.java:37) > > > ... > > I've attached another test case to illustrate the problem. > > > > Once again, my sincere thanks for helping me with this. > > Regards, > > Alan > > > > Kris Verlaenen <[hidden email]> > 29/10/2009 12:00 > > > To > [hidden email] > cc > Rules Users List <[hidden email]> > Subject > Re: [rules-users] [droolsflow] Code-based constraints for EventWait > nodes > - is this possible? > > > > > > > > > Alan, > > The cause of the rollback of the transaction is this: > Caused by: java.io.NotSerializableException: com.test.SimpleFact > > The reason is that, if you use persistence for your session, the > persister will try to save all runtime state of the engine. This > does > not only include process instances, but also rule-related state. By > default, this also includes the data inserted in the memory. We > support > two strategies for storing this data: serialization of the data > (default) or JPA-based storage of entities (by reference). In this > case, the persister is trying to serialize the test object you > inserted > and fails. Making it serializable should fix this. > > Kris > > Quoting [hidden email]: > > > Kris, > > > > I've attached a simple test case (transaction manager, data > source, > > etc. > > are configured via Spring). The error is thrown on line: > > > > ksession.insert(new SimpleFact()); > > > > If this line is commented out, the rule flow executes without > error. > > > > > > > > Many thanks for looking at this. > > > > Regards, > > > > Alan > > > > > > > > > > Kris Verlaenen <[hidden email]> > > 28/10/2009 10:40 > > > > To > > [hidden email] > > cc > > Rules Users List <[hidden email]> > > Subject > > Re: [rules-users] [droolsflow] Code-based constraints for > EventWait > > nodes > > - is this possible? > > > > > > > > > > > > > > Alan, > > > > Could you send me the entire output / stack trace (as the rollback > > of > > the transaction is usually caused by another exception)? > > > > Or a simple test case that shows the error, so I can take a look? > > > > Thx, > > Kris > > > > Quoting [hidden email]: > > > > > Kris, > > > > > > After posting my last question, I quickly came to the same > > conclusion > > > as > > > you, so I'm now using a rule-based constraint in my EventWait > > node. > > > > > > This however has presented a different problem. If I create my > > > session > > > from JPAKnowledgeService, then when I try to insert my fact into > > the > > > > > > session, I get the following error: > > > > > > bitronix.tm.internal.BitronixRollbackException: transaction was > > > marked as > > > rollback only and has been rolled back > > > at > > > > > > bitronix.tm.BitronixTransaction.commit(BitronixTransaction.java:153) > > > at > > > > > > bitronix.tm.BitronixTransactionManager.commit(BitronixTransactionManager.java:96) > > > at > > > > > > org.drools.persistence.session.SingleSessionCommandService.execute(SingleSessionCommandService.java:258) > > > at > > > > > > org.drools.command.impl.CommandBasedStatefulKnowledgeSession.insert(CommandBasedStatefulKnowledgeSession.java:305) > > > (Everything works fine if I create my session from the knowledge > > base > > > - > > > i.e. with no state persistence.) > > > Prior to using a rule-based constraint (with no call to > > > CommandBasedStatefulKnowledgeSession.insert), the session > created > > > from > > > JPAKnowledgeService worked OK. > > > I'm using the default JPA configuration from the Drools > > documentation > > > > > > (persisting to H2 database, etc.). > > > Any ideas what might be causing the problem? > > > Many thanks, > > > Alan > > > > > > > > > > > > > > > Kris Verlaenen <[hidden email]> > > > 23/10/2009 03:00 > > > > > > To > > > Rules Users List <[hidden email]>, > > > [hidden email] > > > cc > > > Rules Users List <[hidden email]> > > > Subject > > > Re: [rules-users] [droolsflow] Code-based constraints for > > EventWait > > > nodes > > > - is this possible? > > > > > > > > > > > > > > > > > > > > > No, the constraint of an EventWait node (or the State node in > > Drools > > > 5.1) can only be rule-based. The reason for this is that the > rule > > > engine knows when to re-evaluates rules (based on the evailable > > > input). > > > If you would use a code-based constraint, the engine would have > > no > > > idea > > > when this code constraint might become true (if it was false at > > the > > > start). Only constant re-evaluation of the code constraint > could > > > achieve this (which would be tremendously inefficient). Could > you > > > explain why you would like to have this behaviour? Maybe there > is > > > an > > > alternative way to model this. > > > > > > To change the value of a variable from inside the process (using > > an > > > action), simply use kcontext.setVariable(name, value). We do > not > > > recommend manually changing the value of a process variable from > > > outside > > > the engine. Again, could you explain why you would like to have > > > this > > > functionality? > > > > > > Kris > > > > > > Quoting [hidden email]: > > > > > > > Can the constraint for an EventWait node in a flow be > code-based > > > > (rather > > > > than rule-based)? The Eclipse plug-in (v 5.0.1) doesn't allow > > this > > > to > > > > be > > > > specified, unlike say for a Split node, although the relevant > > XML > > > can > > > > of > > > > course be edited. > > > > Trying to load such a process flow results in a > > > NullPointerException, > > > > > > > > because the constraint is always interpreted as a rule. > > > > > > > > Ideally what I'd like to do is have an EventWait node where > the > > > > constraint > > > > tests the value of a process variable. This then leads me to > > > another > > > > > > > > question; is there a way of setting the value of a process > > > variable > > > > via > > > > the Drools Flow API? > > > > > > > > Thanks in advance for any help, > > > > > > > > Alan > > > > Tessella plc > > > > 26 The Quadrant, Abingdon Science Park, Abingdon, Oxfordshire, > > > OX14 > > > > 3YS > > > > E: [hidden email], T: +44 (0)1235 555511, F: +44 > > (0)1235 > > > > 553301 > > > > www.tessella.com Registered in England No. 1466429 > > > > > > > > This message is commercial in confidence and may be > privileged. > > It > > > is > > > > > > > > intended for the addressee(s) only. Access to this message by > > > anyone > > > > else > > > > is unauthorized and strictly prohibited. If you have received > > this > > > > message > > > > in error, please inform the sender immediately. Please note > that > > > > messages > > > > sent or received by the Tessella e-mail system may be > monitored > > > and > > > > stored > > > > in an information retrieval system. > > > > > > > > > > > > > > > > > > > Disclaimer: http://www.kuleuven.be/cwis/email_disclaimer.htm > > > > > > > > > > > > > > > > Disclaimer: http://www.kuleuven.be/cwis/email_disclaimer.htm > > > > > > > > > Disclaimer: http://www.kuleuven.be/cwis/email_disclaimer.htm > [attachment "drools-persistence-test.zip" deleted by Alan > Gairey/Tessella] > _______________________________________________ > rules-users mailing list > [hidden email] > https://lists.jboss.org/mailman/listinfo/rules-users > > Disclaimer: http://www.kuleuven.be/cwis/email_disclaimer.htm _______________________________________________ rules-users mailing list [hidden email] https://lists.jboss.org/mailman/listinfo/rules-users |
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