Thank you! Fred
On Friday, July 3, 2015 at 5:10:00 AM UTC-7, Patrik Nordwall wrote: > > We have investigated and fixed the issue. The conclusion was that the > change of self during restarts was not needed and incorrect. We have > changed the implementation to match the documentation "// Completely > safe, "self" is OK to close over" > It will be fixed in upcoming 2.3.12. > > Using pipeTo is still the recommended bridge between futures and actors. > > You must still not close over and use anything in the context from other > threads than the actor's message receive. > > /Patrik > > On Wed, Jun 24, 2015 at 8:25 PM, Endre Varga <[email protected] > <javascript:>> wrote: > >> >> >> On Wed, Jun 24, 2015 at 8:20 PM, Frederic <[email protected] >> <javascript:>> wrote: >> >>> Yes Michael, you are right. I based my example code on the documentation >>> you referenced, assuming it was correct. >>> >>> What would be the correct way to do, the same as when sender is involved >>> or is there something special here? >>> // is this the safe way to proceed? >>> val s = self >>> Future { expensiveCalculation() } onComplete { f => s ! f.value.get } >>> // or is this better? >>> Future { expensiveCalculation() } pipeTo self() >>> >>> Could someone help me understand the following statement from the newly >>> opened issue >>> https://github.com/akka/akka/issues/17805#issuecomment-114389213: >>> "(after all, even if you share the result of self() the message will end up >>> in DeadLetters anyway)". This doesn't match my experience, as actors are >>> restarted, message sent to a copy of self() end up in the actor's mailbox >>> and not in deadLetters. >>> >> >> What I wanted to say that if you stop the actor then: >> - sending to the the ActorRef of that actor (independently if it was >> returned by self() or aquired from actorOf) will end up delivering the >> message to dead letters >> - closing over self() and then calling it after the actor has been >> stopped will return the ActorRef of DeadLetters, so again, sending messages >> to it will end up in dead letters >> >> -Endre >> >> >>> >>> Thanks, Fred >>> >>> On Monday, June 22, 2015 at 2:35:41 PM UTC-7, Michael Frank wrote: >>>> >>>> the current documentation appears to be incorrect, which i believe >>>> was the source of confusion. on line 20 of the code block of the section >>>> "Actors and shared mutable state" on page >>>> http://doc.akka.io/docs/akka/2.3.11/general/jmm.html#jmm-shared-state >>>> it specifically states: >>>> >>>> 18 // Completely safe, "self" is OK to close over >>>> 19 // and it's an ActorRef, which is thread-safe >>>> 20 Future { expensiveCalculation() } onComplete { f => self ! >>>> f.value.get } >>>> >>>> i opened an issue for it: https://github.com/akka/akka/issues/17805 >>>> >>>> -Michael >>>> >>>> On 06/20/15 01:45, Roland Kuhn wrote: >>>> >>>> Hi Frederic, >>>> >>>> you violate the first rule of Actors: never call *any* of their >>>> methods from outside of their context of execution. This is true for all >>>> of >>>> them, including context() and self(). While the result of calling self() >>>> can then safely be shared afterwards (an ActorRef is thread-safe), the >>>> result of context() cannot (because ActorContext is not thread-safe). >>>> >>>> What happens in your sample is that the Actor is destroyed due to the >>>> Exception (that triggers a restart), so anything referencing the old Actor >>>> instance will see a dead entity with nulls in it (in order to minimize >>>> memory leaks in case someone does something wrong). >>>> >>>> Regards, >>>> >>>> Roland >>>> >>>> 19 jun 2015 kl. 02:02 skrev Frederic <[email protected]>: >>>> >>>> There's more... as context is also null in the Future's callback, >>>> anything using context won't work, see below for an updated example using >>>> the Akka's scheduler and dispatcher: >>>> >>>> import akka.actor._ >>>> import scala.concurrent._ >>>> import scala.concurrent.duration._ >>>> >>>> case class Done(s: String) >>>> case object Greet >>>> case class Complete(p: Promise[Unit]) >>>> >>>> class Greeter extends Actor { >>>> import context.dispatcher >>>> def receive = { >>>> case Done(s) => println(s"Done($s) (system still running)!") >>>> case Complete(p) => p.success(()) >>>> case Greet => >>>> val p = Promise[Unit]() >>>> val saveMyself = self >>>> val sched = context.system.scheduler >>>> val disp = context.dispatcher >>>> p.future onComplete { >>>> case _ => >>>> println(s"self is $self") >>>> println(s"self is expexted to be $saveMyself") >>>> // cannot use self to send a message, need to close on self >>>> self ! Done("Send using self") >>>> saveMyself ! Done("Send using saveMyself") >>>> // are we supposed to avoid using context here? >>>> println(s"context is $context") // outputs: context is null >>>> // is this meant to work? >>>> // context.system.scheduler.scheduleOnce(1.millisecond, >>>> saveMyself, Done) >>>> // will fail because we can't get the scheduler as context is >>>> null >>>> try { context.system.scheduler.scheduleOnce(1.millisecond, >>>> saveMyself, Done("scheduler 1")) } catch { case e => println(e) } >>>> // The following will still fail because implicit dispatcher >>>> is context.dispatcher and context is null >>>> try { sched.scheduleOnce(1.millisecond, saveMyself, >>>> Done("scheduler 2")) } catch { case e => println(e) } >>>> // that will work... >>>> sched.scheduleOnce(1.millisecond, saveMyself, Done("scheduler >>>> 3"))(disp, saveMyself) >>>> } >>>> self ! Complete(p) >>>> throw new Exception("Messing with onComplete callback, self will >>>> be dead letters") >>>> } >>>> } >>>> >>>> object HelloAkkaScala extends App { >>>> val system = ActorSystem("helloakka") >>>> val greeter = system.actorOf(Props[Greeter], "greeter") >>>> greeter ! Greet >>>> } >>>> >>>> Program output : >>>> >>>> Running HelloAkkaScala >>>> self is Actor[akka://helloakka/deadLetters] >>>> [ERROR] [06/18/2015 16:47:50.464] >>>> [helloakka-akka.actor.default-dispatcher-3] [ >>>> akka://helloakka/user/greeter] Messing with onComplete callback, self >>>> will be dead letters >>>> java.lang.Exception: Messing with onComplete callback, self will be >>>> dead letters >>>> at Greeter$anonfun$receive$1.applyOrElse(HelloAkkaScala.scala:40) >>>> at akka.actor.Actor$class.aroundReceive(Actor.scala:467) >>>> at Greeter.aroundReceive(HelloAkkaScala.scala:9) >>>> 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$AkkaForkJoinTask.exec(AbstractDispatcher.scala:397) >>>> at scala.concurrent.forkjoin.ForkJoinTask.doExec(ForkJoinTask.java:260) >>>> at >>>> scala.concurrent.forkjoin.ForkJoinPool$WorkQueue.runTask(ForkJoinPool.java:1339) >>>> at >>>> scala.concurrent.forkjoin.ForkJoinPool.runWorker(ForkJoinPool.java:1979) >>>> at >>>> scala.concurrent.forkjoin.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:107) >>>> >>>> self is expexted to be Actor[akka://helloakka/user/greeter#-1327535750] >>>> context is null >>>> java.lang.NullPointerException >>>> java.lang.NullPointerException >>>> Done(Send using saveMyself) (system still running)! >>>> [INFO] [06/18/2015 16:47:50.480] >>>> [helloakka-akka.actor.default-dispatcher-4] [akka://helloakka/deadLetters] >>>> Message [Done] from Actor[akka://helloakka/deadLetters] to >>>> Actor[akka://helloakka/deadLetters] was not delivered. [1] dead >>>> letters encountered. This logging can be turned off or adjusted with >>>> configuration settings 'akka.log-dead-letters' and >>>> 'akka.log-dead-letters-during-shutdown'. >>>> Done(scheduler 3) (system still running)! >>>> >>>> >>>> On Thursday, June 18, 2015 at 2:37:35 PM UTC-7, Frederic wrote: >>>>> >>>>> Hello, >>>>> >>>>> I found a quite specific case involving Actors, Future callbacks and >>>>> exceptions where self becomes deadLetters. >>>>> >>>>> I have the feeling I'm using self the way it is meant to be used, as >>>>> described here: >>>>> http://doc.akka.io/docs/akka/2.3.11/general/jmm.html#jmm-shared-state >>>>> >>>>> Am I doing something wrong or is it a bug? >>>>> >>>>> Please see code and output below to reproduce/illustrate the issue. >>>>> >>>>> Thanks, Fred >>>>> >>>>> import akka.actor._ >>>>> import scala.concurrent._ >>>>> >>>>> case object Done >>>>> case object Greet >>>>> case class Complete(p: Promise[Unit]) >>>>> >>>>> class Greeter extends Actor { >>>>> import context.dispatcher >>>>> def receive = { >>>>> case Done => println("Done (system still running)!") >>>>> case Complete(p) => p.success(()) >>>>> case Greet => >>>>> val p = Promise[Unit]() >>>>> val saveMyself = self >>>>> p.future onComplete { >>>>> case _ => >>>>> println(s"self is $self") >>>>> println(s"self is expexted to be $saveMyself") >>>>> // cannot use self to send a message, bug? >>>>> self ! Done >>>>> saveMyself ! Done >>>>> } >>>>> self ! Complete(p) >>>>> throw new Exception("Messing with onComplete callback, self will >>>>> be dead letters") >>>>> } >>>>> } >>>>> >>>>> object HelloAkkaScala extends App { >>>>> val system = ActorSystem("helloakka") >>>>> val greeter = system.actorOf(Props[Greeter], "greeter") >>>>> greeter ! Greet >>>>> } >>>>> >>>>> Program output : >>>>> >>>>> Running HelloAkkaScala >>>>> self is Actor[akka://helloakka/deadLetters] >>>>> [ERROR] [06/18/2015 14:25:41.510] >>>>> [helloakka-akka.actor.default-dispatcher-4] >>>>> [akka://helloakka/user/greeter] >>>>> Messing with onComplete callback, self will be dead letters >>>>> java.lang.Exception: Messing with onComplete callback, self will be >>>>> dead letters >>>>> at Greeter$anonfun$receive$1.applyOrElse(HelloAkkaScala.scala:27) >>>>> at akka.actor.Actor$class.aroundReceive(Actor.scala:467) >>>>> at Greeter.aroundReceive(HelloAkkaScala.scala:8) >>>>> 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$AkkaForkJoinTask.exec(AbstractDispatcher.scala:397) >>>>> at scala.concurrent.forkjoin.ForkJoinTask.doExec(ForkJoinTask.java:260) >>>>> at >>>>> scala.concurrent.forkjoin.ForkJoinPool$WorkQueue.runTask(ForkJoinPool.java:1339) >>>>> at >>>>> scala.concurrent.forkjoin.ForkJoinPool.runWorker(ForkJoinPool.java:1979) >>>>> at >>>>> scala.concurrent.forkjoin.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:107) >>>>> >>>>> self is expexted to be Actor[akka://helloakka/user/greeter#990239115] >>>>> Done (system still running)! >>>>> [INFO] [06/18/2015 14:25:41.516] >>>>> [helloakka-akka.actor.default-dispatcher-3] >>>>> [akka://helloakka/deadLetters] >>>>> Message [Done$] from Actor[akka://helloakka/deadLetters] to Actor[ >>>>> akka://helloakka/deadLetters] was not delivered. [1] dead letters >>>>> encountered. This logging can be turned off or adjusted with >>>>> configuration >>>>> settings 'akka.log-dead-letters' and >>>>> 'akka.log-dead-letters-during-shutdown'. >>>>> >>>> >>>> -- >>>> >>>>>>>>>> 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]. >>>> To post to this group, send email to [email protected]. >>>> Visit this group at http://groups.google.com/group/akka-user. >>>> For more options, visit https://groups.google.com/d/optout. >>>> >>>> >>>> >>>> >>>> *Dr. Roland Kuhn* >>>> *Akka Tech Lead* >>>> Typesafe <http://typesafe.com/> – Reactive apps on the JVM. >>>> twitter: @rolandkuhn >>>> <http://twitter.com/#%21/rolandkuhn> >>>> >>>> -- >>>> >>>>>>>>>> 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]. >>>> To post to this group, send email to [email protected]. >>>> Visit this group at http://groups.google.com/group/akka-user. >>>> For more options, visit https://groups.google.com/d/optout. >>>> >>>> >>>> -- >>> >>>>>>>>>> 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. >>> >> >> -- >> >>>>>>>>>> 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. >> > > > > -- > > Patrik Nordwall > Typesafe <http://typesafe.com/> - Reactive apps on the JVM > Twitter: @patriknw > > -- >>>>>>>>>> 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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