Hi Allen,
3 jun 2014 kl. 07:48 skrev Allen Nie <[email protected]>:
> Hey,
>
> I want to create a Timer Actor that tracks the progress of the entire
> program (and also estimate remaining execution time). Since the timer actor
> will have to hold mutable variable aka "current progress", I think it should
> be constructed under the highest supervisor instead of being spawned by lower
> actors. So I created this:
>
> object Entry extends App {
> val system: ActorSystem = ActorSystem("Twitter")
> val sup = system.actorOf(Props[Supervisor])
This actor should have a name, let’s call it “app” (i.e. use
system.actorOf(Props[Supervisor], "app")).
> sup ! Sentence(.....)
> }
>
> class Supervisor extends Actor {
>
> def receive = {
> case sen: Sentence =>
> val timer = context.actorOf(Props[Timer])
This one should also have a name, e.g. “timer”.
> val pcfg = context.actorOf(Props[PCFGParser])
This one will need to be acquainted with the timer, so I’d recommend
val pcfg = context.actorOf(PCFGParser.props(timer), "parser")
which needs
object PCFGParser {
def props(timer: ActorRef): Props = Props(new PCFGParser(timer))
}
> pcfg ! sen.copy()
> }
> }
>
> Then I have this lower actor that does all the actions:
>
> class PCFGParser extends Actor{
Introduce the “timer” ActorRef here …
>
> def receive = {
> case sen: Sentence =>
> //....business logic
> val ps = context.actorOf(Props[PatternSearch]) //create another actor
> ps ! sen.copy(tree = Some(tree))
> context.actorSelection("../timer") ! PCFGAddOne
… then you can send to it here.
> }
> }
>
> So at this point, I think it should send messages back to that Timer Actor.
> BUT HOW!? I tried actorSelection, but all I got were "dead letter" errors.
> The message was not delivered. And it also seems like this PCFGParser actor
> failed to send messages to both its child actor and Timer Actor:
>
> [INFO] [06/03/2014 01:35:25.290] [Twitter-akka.actor.default-dispatcher-4]
> [akka://Twitter/user/$a/$h/$a] Message
> [TwitterProject.PCFGParserMsg$Sentence] from
> Actor[akka://Twitter/user/$a/$h#11
> 90256968] to Actor[akka://Twitter/user/$a/$h/$a#-1918790382] was not
> delivered. [6] dead letters encountered.
>
> [INFO] [06/03/2014 01:35:25.291] [Twitter-akka.actor.default-dispatcher-17]
> [akka://Twitter/user/$a/$d/../timer] Message
> [TwitterProject.TimerMsg$PCFGAddOne$] from Actor[akka://Twitter/user/$a/
> $d#-1685001108] to Actor[akka://Twitter/user/$a/$d/../timer] was not
> delivered. [7] dead letters encountered.
>
> First, I admit there could be some error that's inside the business logic of
> this actor that caused this error (or really?? Could a dead actor triggers
> message not delivered error?) Second, what's the right way for this
> PCFGParser actor to send message to a distant actor?
Hope this helps! And remember to always give names to your actors, they are
precious little helpers of yours :-)
Regards,
Roland
>
> Thank you!
>
> --
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Dr. Roland Kuhn
Akka Tech Lead
Typesafe – Reactive apps on the JVM.
twitter: @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
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