I have been evaluating a number of frameworks including jBPM and Drools flow for my application requirements. Lots of the opinions seem to be inclined towards Drools flow as its more flexible, knowledge oriented, easier to integrate with business rules, etc..

The application is some sort of an Email Campaign manager , where different customers can sign in, prepare (design) and launch email campaigns.

The application should be able to do the following :

1- Receive a list of email addresses, send emails to each of these addresses starting from a certain date and during a certain time interval of the day , do some custom actions, and then wait for reply emails. 2- If a reply email is received and depending on the response text of the email , and depending on the time the email was received certain actions need to happen, web service calls need to take place, and error handling for these calls. 3- The application will manage and run many and different campaigns (different customers and different flows for each customer) at any point of time.

The first question is : Is Drools flow the way to go about this? My main concerns are scalability, suspending, resuming flows, and long wait, and flows management.

As you see from the requirements : There is a scheduling part : Certain flows need to be run at a certain point in time, they need to get suspended and then resumed. For example start sending emails starting on Dec 1st 2010 and send emails only in the time interval between 08:00 and 17:00 GMT. By then it might be that all subscribers have been sent emails, but it might not be the case, the process needs to (resume) on Dec 2nd and send a second batch, however certain (users) already received emails and they should be able to (continue at different stages of the flow)

There are long wait states : Days or even weeks , i need to persist, suspend / resume and terminate flows (manage flows)

External Events :

This is where i got stuck first, i tried to put together a simple flow (see attached screenshot)

See image http://img46.imageshack.us/img46/9620/workflowwithevents.png

, there is a start node , connected to an action node, connected to a join. An event node is connected to a second action node, which is connected to the join. The join is an AND join , after the join there is an action and the end node.

Here is the sample code i am using to launch the flow :

    KnowledgeBuilder builder = KnowledgeBuilderFactory
            .newKnowledgeBuilder();
    builder.add(ResourceFactory.newClassPathResource("campaign.rf",
            CampaignsDroolsPoc.class), ResourceType.DRF);

    if (builder.hasErrors()) {
        KnowledgeBuilderErrors errors = builder.getErrors();
        Iterator<KnowledgeBuilderError> iterator = errors.iterator();
        while (iterator.hasNext()) {
            System.out.println(iterator.next().toString());
        }

    }

    KnowledgeBase base = KnowledgeBaseFactory.newKnowledgeBase();
    base.addKnowledgePackages(builder.getKnowledgePackages());

    final StatefulKnowledgeSession ksession = base
            .newStatefulKnowledgeSession();

    // KnowledgeRuntimeLoggerFactory.newConsoleLogger(ksession);

    ksession.getWorkItemManager().registerWorkItemHandler("Log",
            new SendSMSWorkItemHandler());

    ProcessInstance startProcess = ksession.startProcess("flow");

    System.out.println("Signaling event");

    startProcess.signalEvent("ev1", "ev1");

    System.out.println("Signaled");

    ksession.fireUntilHalt();

I am noticing that the event get triggered, the action node connected to the event gets triggered, however things seem to get stuck at the join. The flow does not continue past the AND join and the flow seems to get stuck. The action following the node does not get triggered.

I also went through the drools flow documentation , and all the example codes, however i didn't find anything there.

In addition any hints about the way to go about architecting the solution, and implementing it would be great.