Re: [rules-users] Drools Flow: waiting for process to complete without polling
Hello Kris,
Thank you for your reply.
I am currenty doing "test-driven" development outside an application
server to learn the API. I launch processes from within a unit test
method; hence my need to wait in this manner so that I can perform a
final assertion on process state (after the process is complete).
You are totally correct to point out that in real life, I will be
executing long-running processes from within JBoss in my application
across multiple executions of the application. So what is the typical
approach for doing that? Do you typically install Drools as a service in
a SAR, or do you launch it with a servlet startup listener when the WAR
starts? Also, how do you make sure a clean undeploy/shutdown occurs
where process execution is gracefully suspended and process states are
saved? Can you give me some pointers?
Thank you.
Kris Verlaenen wrote:
I'm not sure that having a thread wait like this until all
processes
have completed is a good idea in general, as in theory processes could
run for a long time (hours/days/weeks/...). Unless of course you are
only using synchronous processes, but in that case the engine will only
return once the process has been completed anyway (if you call it
synchronously).
But the approach you suggest is valid, you can register an event
listener to react whenever a process instance is completed, or similarly
you could use the history log to retrieve this kind of information
(making it decoupled from the actual execution).
Kris
Quoting Alexandros Karypidis <akarypid(a)yahoo.gr>:
> Hello,
>
> I'm not very experienced in the Drools Flow API so I'm looking into
> the
> best way to code a simple thing: wait for all processes in a session
> to
> complete without polling.
>
> The only way I could thing of from the javadoc reference I read, is
> to
> synchronize and do a wait()/notify() using a ProcessEventListener. It
>
> seems a lot of work for a use-case that is too basic. I set up a
> listener like this:
>
> pel = new ProcessEventListener() {
> // ...
> public void afterProcessCompleted(ProcessCompletedEvent
> pce) {
> synchronized (this) {
> notifyAll();
> }
> }
> }
> ksession.addEventListener(pel);
>
> ...then wait for processes (one in this simplified case) to complete
>
> like this:
>
> synchronized (pel) {
> new Thread(new Runnable() {
> public void run() {
> ksession.fireUntilHalt();
> }
> }).start();
> ksession.startProcess("some.process");
> pel.wait(); // the notifyAll() resumes this
> }
>
> Is there a better way to do this?
>
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