[jboss-dev-forums] [Design of JBoss jBPM] - Re: jBPM Multithreading: Is there a specification?

[estaub]

Tom,

I think this is another case, like the one a month or so ago with ProcessInstances not existing when needed that I tried to help with, where additional database commits are necessary.

In this case, the commit must be somewhere in the flow of execution between:

In TaskInstance:
public void setActorId(String actorId, boolean overwriteSwimlane){
  |     // do the actual assignment
  |     this.previousActorId = this.actorId;
  |     this.actorId = actorId;
  |     if ( (swimlaneInstance!=null)
  |          && (overwriteSwimlane) ) {
  |       log.debug("assigning task '"+name+"' to '"+actorId+"'");
  |       swimlaneInstance.setActorId(actorId);
  |     }
  | COMMIT AFTER HERE...  
  | 

and in GraphElement:
  void executeActions(List actions, ExecutionContext executionContext, boolean isPropagated) {
  |     if (actions!=null) {
  |       Iterator iter = actions.iterator();
  |       while (iter.hasNext()) {
  |         Action action = (Action) iter.next();
  |         if ( action.acceptsPropagatedEvents()
  |              || (!isPropagated)
  |            ) {
  |           if (action.isAsync()) {
  |             Message continuationMsg = new ExecuteActionCommand(action, executionContext.getToken());
  |             MessageService messageService 
  |                = (MessageService) Services.getCurrentService(Services.SERVICENAME_MESSAGE);
  | COMMIT BEFORE HERE:
  |             messageService.send(continuationMsg);
  | 

Because the next instruction executed after the send may be in the other thread - you haven't committed yet, I don't think.

An efficient implementation would be to keep an internal queue of messages to send after you've committed, before you enter a wait state.  This would avoid any additional commits, and I think it would preserve the correct semantics.

I easily may be overlooking something - I don't know this code anywhere near as well as you, of course!

-Ed Staub

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