Hi George,
I think you will find the answer here:
http://doc.akka.io/docs/akka/2.3.9/java/routing.html#Supervision
Regards,
Patrik
On Mon, Feb 23, 2015 at 1:56 PM, George Lu <luwenbin...@gmail.com> wrote:
> Dear all,
>
> For learning Akka, I wrote below in Java to test fault-tolerance.
> I have a master actor to assign job to worker actors, in the master actor,
> simply divide the job into several pieces and use round robin router to
> assign to workers (i.e. let workers add slices of a summation).
>
> In the worker onReceive, I let the first worker who does its job to throw
> an Exception, please consider below code:
>
> WorkerActor/onReceive:
>
> if(RetryCount >=1 ) {
> RetryCount--;
> throw new Exception("exception thrown from worker");
> }
>
> WorkerActor/preRestart:
> public void preRestart(Throwable cause, Option<Object> msg) {
> System.out.println("Thread "+Thread.currentThread().getId()+" get restart
> message ");
> if(cause instanceof Exception && msg.nonEmpty()) {
> WorkerMessage workerMsg = (WorkerMessage)msg.get();
> getSelf().forward(workerMsg, getContext());
> //getSelf().tell(workerMsg, getSender());
> }
> else {
> return;
> }
> }
>
> For the master actor:
> router = getContext().actorOf(
> Props.create(WorkerActor.class).withRouter(
> new RoundRobinRouter(10)));
>
> private static SupervisorStrategy strategy = new OneForOneStrategy(10,
> Duration.create(1, TimeUnit.MINUTES),
> new Function<Throwable, Directive>() {
>
> public Directive apply(Throwable exception) throws Exception {
> if (exception instanceof Exception) {
> return SupervisorStrategy.restart();
> } else {
> return SupervisorStrategy.escalate();
> }
> }
>
> });
>
> @Override
> public SupervisorStrategy supervisorStrategy() {
> return strategy;
> }
>
> I have 10 workers running and tasks assigned in round-robin algorithm,
> after running the example, the restart run as expected, but I have several
> questions:
> 1) All 10 workers' preRestart get called, why is that, is that correct as
> I used OneForOneStrategy and I thrown exception only from one worker?
> I use the msg.nonEmpty() to get rid of those null msg passed in as
> from my running result, all 10 workers run the preRestart which I am quite
> confused.
>
> 2) After one worker forwards the message, another worker receives the
> message and re-process it, they are not the same thread, is that correct?
> Thread 11 processing worker 1
> Thread 11 throw exception
> Thread 18 processing worker 1
> From the output, thread 11 throw exception and thread 18 process later for
> fail-over. From understanding, if one child actor failed, then parent actor
> should invoke that child actor's preRestart method only, not for all child
> actors. Is that correct?
>
> Thanks in advance!
>
> Regards,
> George
>
> --
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--
Patrik Nordwall
Typesafe <http://typesafe.com/> - Reactive apps on the JVM
Twitter: @patriknw
[image: Scala Days] <http://event.scaladays.org/scaladays-sanfran-2015>
--
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>>>>>>>>>> Check the FAQ:
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