Hi Eax, There is one pattern in contrib that does something similar to what you need: http://doc.akka.io/docs/akka/2.3.11/contrib/aggregator.html
I recommend taking a look at that, and see if it what you want, or just take the code and customize it as you want. In the future we plan to add some nice DSL to make these patters more easy to express. Will see where (or if) that one ends up, but until then you should try the aggregator. -Endre On Wed, Jun 3, 2015 at 1:32 PM, pjan vandaele <[email protected]> wrote: > Hi Eax, > > Whether this is a race condition, is something that is unclear from the > code itself. It would help if you would provide us with the expected order > of operations. > > I see 2 possible ways you could have in mind. > > First: > > (request 1) readSomethingFromDB() > (request 1) readAndWriteActorState() > (request 1) writeSomethingToDB() > ... > (request 2) readSomethingFromDB() > (request 2) readAndWriteActorState() > (request 2) writeSomethingToDB() > ... > > In which case you can let the actor become waitingForResult and then pipe > the result of the future to self, upon which it returns it to the original > sender, and becomes waitingForTask (or similar) again. In this case, you > need to handle the incoming SomeMessage messages, either by putting them in > a queue local to the actor, or use a pull pattern (so the actor asks for a > nextMessage once it completes a task) > > Second: > > (request 1) readSomethingFromDB() > (request 2) readSomethingFromDB() > ... > (request 1) readAndWriteActorState() > (request 2) readAndWriteActorState() > ... > (request 1) writeSomethingToDB() > (request 2) writeSomethingToDB() > ... > > In this case, you could create a couple of actors, working in serie, each > of them doing a single task. You can forward the initial sender with each > result if that sender is waiting for the response... > > > In any case, when using Futures within actors, you should be careful with > just using sender, as it is a function call within the execution context of > an actor. Once the future returns, the actor might already have moved on to > processing a new message from another sender, to which the result of the > future would then wrongfully get returned. You should do something like > > val originalSender = sender > val fResult = for ... > > fResult pipeTo originalSender > > pjan > > On Tuesday, June 2, 2015 at 3:49:43 AM UTC+9, Eax Melanhovich wrote: >> >> Hello. >> >> As I understand code like this is quite common: >> >> def receive = { >> case r: SomeMessage => >> val fResult: Future[SomeResult] = { >> for { >> _ <- readSomethingFromDB() >> _ = readAndWriteActorState() >> _ <- writeSomethingToDB() >> _ <- doSomethingElse() >> } yield result >> } >> fResult pipeTo sender >> } >> >> In such cases it is a good idea to use Stash trait and become / >> unbecome to avoid cases like this: >> >> (request 1) readSomethingFromDB() >> (request 2) readSomethingFromDB() >> (request 2) readAndWriteActorState() >> (request 1) readAndWriteActorState() >> (request 1) writeSomethingToDB() >> (request 2) writeSomethingToDB() >> ... etc ... >> >> Which clearly is a race condition and almost always is not something >> what programmer really wants. Still as I understand there is no >> stashedPipeTo method or something like this in Akka, so every team has >> to write its own version. >> >> Am I right so far? And is there any reason not to add such a method to >> Akka? >> >> -- >> Best regards, >> Eax Melanhovich >> http://eax.me/ >> > -- > >>>>>>>>>> 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. > -- Akka Team Typesafe - Reactive apps on the JVM Blog: letitcrash.com Twitter: @akkateam -- >>>>>>>>>> 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.
