Thanks Michael. That was very helpful. ~ Karthik On Wednesday, January 20, 2016 at 10:27:45 AM UTC-8, Michael Frank wrote: > > passing around an ActorRef is safe, because an ActorRef is an immutable > structure: http://doc.akka.io/api/akka/2.4.1/akka/actor/ActorRef.html > > there is an alternative however, which i think is less 'leaky'. in the > handling of Request in actor A, you can use ask() and pipeTo(): > > def receive = { > > case req: Request if some_special_condition => > actor2.ask(new HandleSpecialCondition()).pipeTo(sender()) > > case req: Request => > sender() ! new NormalResponse() > } > > a couple things to note: 1) i broke up your receive function into two > cases using a guard just for clarity, 2) i made up NormalResponse, and 3) > ask() and ? are interchangeable, i prefer ask(). hopefully the intent is > clear. > > what i like about this pattern is that actor B doesn't need to know > anything about the the requesting actor. you also get timeout support by > passing a timeout to the ask() or putting an implicit timeout in scope, > which is useful if actor B is doing something like querying a database or > something else which can fail. the disadvantage to this approach is that > ask() creates an intermediate actor 'behind the scenes', so there is > (small) overhead in terms of allocation and scheduling. this overhead is > something you probably shouldn't worry about, but it's good to understand > what's happening underneath. > > -Michael > > On 01/20/16 00:17, Karthik Deivasigamani wrote: > > Hi, > I have a use case where I have to pass message between actors and send > a response back to the caller. > Once I get a request I invoke Actor A, which will do some DB call and > return results. But in certain cases actor A has to invoke actor B and get > some results from Actor B. It then has to return that result back to the > guy who sent the request. I accomplished this by passing a reference to the > original sender in the message that I send to actor B as shown below : > > > App { > > val actor1 = system.actorOf(A) > val actor2 = system.actorOf(B) > //I want actor 1 to process this request > actor1 ? new Request("process this") > } > > case class HandleSpecialConition(sender : ActorRef) > case class SpecialConditionResponse(sender : ActorRef, response: String) > > A extends Actor { > > def receive = { > case req : Request => { > //Checks for special condition and if so sends a message to actor2 and > the message is embedded with a reference to the sender to whom we have to > respond back > if (some_special_condition) { > actor2 ! new HandleSpecialCondition(sender) > } else { > "sending_back_response" > } > } > > //when we get the response from Actor B it will contain the reference to > the original sender and we reply back to him > case response : SpecialConditionResponse => { > response.sender ! response.response > } > > } > > } > > B extends Actor { > def receive = { > case m : HandleSpecialCondition { > //reply back to actor 1 > sender ! new SpecialConditionResponse(m.sender, "Response for > special condition") > } > } > } > > > > > I wanted to ask if there is better way to accomplish this without passing > the original sender's reference around. Is there something wrong with this > kind of approach. > > Thanks, > Karthik > -- > >>>>>>>>>> Read the docs: <http://akka.io/docs/>http://akka.io/docs/ > >>>>>>>>>> Check the FAQ: > <http://doc.akka.io/docs/akka/current/additional/faq.html> > http://doc.akka.io/docs/akka/current/additional/faq.html > >>>>>>>>>> Search the archives: > <https://groups.google.com/group/akka-user> > 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 https://groups.google.com/group/akka-user. > For more options, visit https://groups.google.com/d/optout. > > >
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