This looks good. I will sit down tomorrow to give it a shot, thanks to everyone! Markus
2014-10-13 19:52 GMT+02:00 Michael Frank <[email protected]>: > I think Richard's suggestion is a good one. a simple implementation > might be: > > class SomeActor extends Actor with Stash { > > def doThing: Future[Result] = ??? > > def waiting = { > case Start => > doThing pipeTo self // execute doThing, and send the result back > to the actor > become(running) > } > > def running = { > case result: Result => > // do something with the result > unstashAll() > become(waiting) > case _ => > try { stash() } > catch { > case ex: StashOverflowException => sender() ! Error // too much > work queued up! let the sender know. > } > } > > def receive = waiting > > } > > note the check for stash overflow. as you brought up earlier, messages > could be received by your actor at a faster rate than your actor can > process them. we can queue these messages up for orderly processing, but > eventually we will run out of memory if we just blindly accept messages > forever. to guard against this scenario, we signal to the sender if we > have too many queued messages. signaling to the sender in this way is > called backpressure. the sender will then need to make a decision whether > to retry or give up. > > Richard also discussed using FSM. for a single purpose actor (that is, an > actor that only exists to execute doThing method and then process the > result) i think the above is a good solution. If your actor is more > complicated, then you might want to learn about FSM. The decision between > become() and FSM is a bit of a personal taste, but my thought process is: > > 1) does the actor only need to process messages as a linear sequence of > steps? use become() and stash(), or simply keep state manually using > actor-local variables. > 2) does the actor have branching behavior (in other words, multiple > states)? maybe use FSM, but if there are only two states, then become() is > probably easier. > 3) does the behavior have 3 or more states? almost always use FSM. > > -Michael > > > On 10/13/14 07:47, Richard Rodseth wrote: > > Let's see what the experts say, but you could put the actor in a > "suspended" state using become(). Take a look at the link I provided and > see if that makes any sense. > > On Mon, Oct 13, 2014 at 7:39 AM, Joheinz <[email protected]> wrote: > >> What I had been trying to express (non-native speaker), is that when the >> actor processes/creates a future in the receive method, it will very >> quickly proceed the next message, without a guarantee that the future is >> completed. What I somehow would like to achieve: avoid Await.result due to >> its blocking characteristics, but also prevent the actor from creating to >> much noise. I do not know it is possible, but I imagine that I could >> somehow tell the mailbox of the actor to proceed only when the future the >> actor had created is completed. >> >> Hopefully that makes more sense, >> >> Markus >> >> >> 2014-10-13 16:28 GMT+02:00 Richard Rodseth <[email protected]>: >> >>> I don't follow your snippet. Receive is a partial function from Any to >>> Unit, so it doesn't return anything. >>> >>> def receive = { >>> case Start => { >>> val futureResult = someFuture >>> someFuture pipeTo sender >>> } >>> } >>> >>> You don't need to add an ask- you can just pipe someFuture to self or >>> the sender. The result will be queued in the sender's mailbox when the >>> future completes. >>> If you're careful about "closing over self" you can also implement >>> future.onComplete within the receive block. >>> >>> If the sender is sensitive to the order of messages received, it can >>> use become() to change states or use the FSM trait. >>> http://letitcrash.com/post/54507231889/2-2-spotlight-simpler-use-of-stash >>> >>> Hope this helps. >>> >>> >>> On Mon, Oct 13, 2014 at 6:47 AM, Joheinz <[email protected]> wrote: >>> >>>> Hi *, >>>> >>>> Let's say I have an actor which receives a message Start and is >>>> processing this message asynchrounously. >>>> >>>> someActor ! start >>>> >>>> class SomeActor { >>>> def receive = { >>>> case Start => >>>> for { >>>> _ <- someFuture >>>> } yield () >>>> } >>>> >>>> Because processing of Start happens asynchronous it could be that >>>> SomeActor receives more messages before the processing of start is >>>> completed. >>>> >>>> What would be my options to improve this behaviour? >>>> - I could use Await.result - which does not seem to be a reasonable >>>> option >>>> - I could use the ask pattern and pipe the response back to the sender. >>>> In that case what would happen if other actors send me messages? >>>> >>>> Are there any other ways to deal with this situation? I am concerned >>>> that messages arrive when the actor is not in a stable state yet, and I >>>> would like to prevent this. >>>> >>>> Thanks, >>>> Markus >>>> >>>> >>>> >>>> >>>> >>>> -- >>>> >>>>>>>>>> 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]. >>> 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]. >> 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]. > 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]. > 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. 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