akka.pattern
Interface AskSupport


public interface AskSupport

This object contains implementation details of the “ask” pattern.


Nested Class Summary
private static class AskSupport.AskableActorRef
          Implementation detail of the “ask” pattern enrichment of ActorRef
 
Method Summary
 AskSupport.AskableActorRef ask(ActorRef actorRef)
          Import this implicit conversion to gain ?
 scala.concurrent.Future<java.lang.Object> ask(ActorRef actorRef, java.lang.Object message, Timeout timeout)
          Sends a message asynchronously and returns a Future holding the eventual reply message; this means that the target actor needs to send the result to the sender reference provided.
 

Method Detail

ask

AskSupport.AskableActorRef ask(ActorRef actorRef)
Import this implicit conversion to gain ? and ask methods on ActorRef, which will defer to the ask(actorRef, message)(timeout) method defined here.


 import akka.pattern.ask

 val future = actor ? message             // => ask(actor, message)
 val future = actor ask message           // => ask(actor, message)
 val future = actor.ask(message)(timeout) // => ask(actor, message)(timeout)
 

All of the above use an implicit akka.actor.Timeout.


ask

scala.concurrent.Future<java.lang.Object> ask(ActorRef actorRef,
                                              java.lang.Object message,
                                              Timeout timeout)
Sends a message asynchronously and returns a Future holding the eventual reply message; this means that the target actor needs to send the result to the sender reference provided. The Future will be completed with an AskTimeoutException after the given timeout has expired; this is independent from any timeout applied while awaiting a result for this future (i.e. in Await.result(..., timeout)).

Warning: When using future callbacks, inside actors you need to carefully avoid closing over the containing actor’s object, i.e. do not call methods or access mutable state on the enclosing actor from within the callback. This would break the actor encapsulation and may introduce synchronization bugs and race conditions because the callback will be scheduled concurrently to the enclosing actor. Unfortunately there is not yet a way to detect these illegal accesses at compile time.

Recommended usage:


   val f = ask(worker, request)(timeout)
   flow {
     EnrichedRequest(request, f())
   } pipeTo nextActor
 

See Future for a description of flow