Thank you for your response. AKKAs place in this application is to manage the concurrency involved in distributing tasks to workers, and processing them, etc... The implementation of the interface requires multi-threaded operation, and refactoring the interface introduces a huge burden on basically ever client of the library. It's also unlikely that they would be willing to adopt the actor model whole heartedly. Consequently I do have a general problem of needing to read inboxes from threads, although in this particular instance I could probably move it back into the Actor that is populating the inbox. I will look at the article you presented, but I guess the one question that is still open. Shouldn't inbox.receive() be declared to throw TimeoutException given that it is in fact throwing it.
Steve Ramage On Friday, 23 May 2014 06:29:17 UTC-7, Martynas Mickevičius wrote: > > Hello Steve, > > it seems that you are using > ActorD*sl*<http://doc.akka.io/docs/akka/2.3.3/scala/actordsl.html>. > It is meant to be used mostly for trying things out in the REPL. I would > suggest re-factoring your application to separate actors and letting Akka > do the concurrency management. In that case you should get rid of Runnable > I see in your example and move it to actor. > > Have you seen this > article<http://letitcrash.com/post/30165507578/shutdown-patterns-in-akka-2>, > which discuses some of the shutdown patterns? > > > On Wed, May 21, 2014 at 9:09 PM, Steve Ramage <[email protected] <javascript:> > > wrote: > >> Hello, >> >> I'm new to Akka, and to provide some context to my question I will >> provide some background to the problem I'm actually trying to solve. I have >> only read a few chapters of the Akka manual, but have started implementing >> anyway since I need to get my hands dirty, and so no doubt do not a firm >> understanding of Akka principles and concepts. Essentially I have written a >> library for use in my narrow field of scientific research, and central to >> it is the following interface (everything is in Java 7, and this is >> slightly simplified): >> >> interface TargetAlgorithmEvaluator >> { >> /** >> * Do the task descriptions, and when complete notify the onSuccess() >> or onFailure() method of the callback >> */ >> public void evaluateTaskAsync(List<TaskDescription> t, Callback c); >> /** >> * Shutdown any resources associated with this TargetAlgorithmEvaluator >> */ >> public void notifyShutdown(); >> } >> >> A task in this case is roughly running a program and getting some >> results, and there are a bunch of ways you can do it. The tasks come from a >> very specific domain, and aren't general at all. The first and default way >> is locally, via the command line. So of course there is an implementation >> of this that just executes the tasks on the command line, and then gets the >> results. Sometimes we want to do 'lots' of these executions and so it makes >> sense to distribute them, and so another one exists that actually uses >> MySQL and has workers poll from the SQL database, and this works very well. >> Unfortunately for releasing our tools built with this library, the >> requirement that users have a tuned MySQL server around is limiting, so we >> would like some other distributed mechanism and hence Akka. Unlike what I >> imagine are standard Akka use cases, these distributions are incredibly >> transient, they just are scheduled on some shared cluster, work together >> for a while and are terminated. There is no stable or perpetual deployment. >> It's just a master / slave architecture. The way this currently works in >> Akka is that the master job spins up, creates an actor system that is >> listening for other actors. When other actors on other systems come online, >> it will dispatch the tasks to them. The workers will then use the Command >> line implementation locally before giving the result back via Akka to the >> master. >> >> One problem I'm currently having is implementing the notifyShutdown() >> method. This method needs to shutdown all the thread pools and the actor >> system etc. One thread in this listens to a specific inbox for completion >> results, and then dispatches calls to the callback in another thread. >> >> The code looks like the following: >> >> Runnable run = new Runnable(){ @Override >> public void run() { >> while(!Thread.interrupted() && !stopProcessingInbox.get()) >> { Object o = null; >> try { String threadName = "My Thread " + Math.random(); >> System.out.println(threadName); >> Thread.currentThread().setName(threadName); >> try { >> o = inbox.receive(new FiniteDuration(1, TimeUnit.SECONDS)); >> } finally >> { System.err.println("Done recieve"); >> } } catch(Throwable e) >> { System.out.println("Error: " + e); >> throw e; } >> >> >> if (o == null) continue; >> >> //Rest of while loop here >> >> } >> } >> } >> } >> >> >> Essentially the problem is that I would like to make the inbox.receive >> sensitive to interruption, that might occur when notifyShutdown() is >> called. The above code however has some very weird output that I just don't >> understand: >> >> My Thread 0.7085946542233289 >> Done recieve >> Error: java.util.concurrent.TimeoutException: deadline passed >> Exception in thread "My Thread 0.7085946542233289" java.lang.Error: >> java.util.concurrent.TimeoutException: deadline passed at >> java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1151) >> at >> java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615) >> at java.lang.Thread.run(Thread.java:744)Caused by: >> java.util.concurrent.TimeoutException: deadline passed at >> akka.actor.dsl.Inbox$InboxActor$$anonfun$receive$1.applyOrElse(Inbox.scala:117) >> at scala.PartialFunction$AndThen.applyOrElse(PartialFunction.scala:184) >> at akka.actor.Actor$class.aroundReceive(Actor.scala:465) >> at akka.actor.dsl.Inbox$InboxActor.aroundReceive(Inbox.scala:62) >> at akka.actor.ActorCell.receiveMessage(ActorCell.scala:516) >> at akka.actor.ActorCell.invoke(ActorCell.scala:487) >> at akka.dispatch.Mailbox.processMailbox(Mailbox.scala:238) >> at akka.dispatch.Mailbox.run(Mailbox.scala:220) >> at >> akka.dispatch.ForkJoinExecutorConfigurator$AkkaForkJoinTask.exec(AbstractDispatcher.scala:393) >> at scala.concurrent.forkjoin.ForkJoinTask.doExec(ForkJoinTask.java:260) >> at >> scala.concurrent.forkjoin.ForkJoinPool$WorkQueue.runTask(ForkJoinPool.java:1339) >> at >> scala.concurrent.forkjoin.ForkJoinPool.runWorker(ForkJoinPool.java:1979) >> at >> scala.concurrent.forkjoin.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:107) >> >> >> >> So my questions or concerns are as follows: >> >> >> 1) Why does the stack trace which as far as I can tell is generated when the >> timeout expires NOT show my code at all. >> >> 2) I can't seem to catch this exception at all, it looks like the code is >> throwing a checked exception j.u.c.TimeoutException, even though the method >> declaration for inbox.receive doesn't declare it. >> >> 3) What is the best way to implement a shutdown procedure, essentially I >> will have a thread blocking on an inbox and I would like to have that thread >> terminate _GRACEFULLY_. >> >> >> >> Other things I should mention is that I'm running Akka 2.3.2, and I am >> unfamiliar with Maven so I literally just added every jar in the download to >> my class path. >> >> >> Thanks, >> Steve Ramage >> >> >> >> >> -- >> >>>>>>>>>> Read the docs: http://akka.io/docs/ >> >>>>>>>>>> Check the FAQ: >> http://doc.akka.io/docs/akka/current/additional/faq.html >> >>>>>>>>>> Search the archives: https://groups.google.com/group/akka-user >> --- >> You received this message because you are subscribed to the Google Groups >> "Akka User List" group. >> To unsubscribe from this group and stop receiving emails from it, send an >> email to [email protected] <javascript:>. >> To post to this group, send email to [email protected]<javascript:> >> . >> Visit this group at http://groups.google.com/group/akka-user. >> For more options, visit https://groups.google.com/d/optout. >> > > > > -- > Martynas Mickevičius > Typesafe <http://typesafe.com/> – > Reactive<http://www.reactivemanifesto.org/>Apps on the JVM > -- >>>>>>>>>> Read the docs: http://akka.io/docs/ >>>>>>>>>> Check the FAQ: >>>>>>>>>> http://doc.akka.io/docs/akka/current/additional/faq.html >>>>>>>>>> Search the archives: https://groups.google.com/group/akka-user --- You received this message because you are subscribed to the Google Groups "Akka User List" group. 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