Alright, now we have bit more information :)
If I understand your case properly, once a process is started the web service will return at least process instance id to the caller for further reference, correct? If so, you could do one of the following:
- return session id as well with process instance id so it can be referenced for subsequent calls
- maintain a map of process instance id to session id on jBPM service side (either in db or distributed cache)
That would mean that each call should dispose the session. Next calls will load the session based on provided session id regardless of what server the request is being processed on.
What do you think about it?