Package org.apache.pekko.pattern

Interface AskSupport

  • public interface AskSupport
    This object contains implementation details of the “ask” pattern.

    • Method Summary

      All Methods Instance Methods Abstract Methods 
      Modifier and Type Method Description
      AskableActorRef ask​(ActorRef actorRef)
      Import this implicit conversion to gain ? and ask methods on pekko.actor.ActorRef, which will defer to the ask(actorRef, message)(timeout) method defined here.
      scala.concurrent.Future<java.lang.Object> ask​(ActorRef actorRef, java.lang.Object message, ActorRef sender, Timeout timeout)  
      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.
      AskableActorSelection ask​(ActorSelection actorSelection)
      Import this implicit conversion to gain ? and ask methods on pekko.actor.ActorSelection, which will defer to the ask(actorSelection, message)(timeout) method defined here.
      scala.concurrent.Future<java.lang.Object> ask​(ActorSelection actorSelection, java.lang.Object message, ActorRef sender, Timeout timeout)  
      scala.concurrent.Future<java.lang.Object> ask​(ActorSelection actorSelection, 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.
      scala.concurrent.Future<java.lang.Object> askWithStatus​(ActorRef actorRef, java.lang.Object message, ActorRef sender, Timeout timeout)
      Use for messages whose response is known to be a pekko.pattern.StatusReply.
      scala.concurrent.Future<java.lang.Object> askWithStatus​(ActorRef actorRef, java.lang.Object message, Timeout timeout)
      Use for messages whose response is known to be a pekko.pattern.StatusReply.

    • Method Detail

      • ask

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

        
 import org.apache.pekko.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 pekko.util.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 pekko.pattern.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)). A typical reason for AskTimeoutException is that the recipient actor didn't send a reply.

        Warning: When using future callbacks, inside actors you need to carefully avoid closing over the containing actor&rsquo;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)
   f.map { response =>
     EnrichedMessage(response)
   } pipeTo nextActor

      • ask

        scala.concurrent.Future<java.lang.Object> ask​(ActorRef actorRef,
                                              java.lang.Object message,
                                              ActorRef sender,
                                              Timeout timeout)

      • ask

        AskableActorSelection ask​(ActorSelection actorSelection)
        Import this implicit conversion to gain ? and ask methods on pekko.actor.ActorSelection, which will defer to the ask(actorSelection, message)(timeout) method defined here. 

        
 import org.apache.pekko.pattern.ask

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

        All of the above use an implicit pekko.util.Timeout.

      • ask

        scala.concurrent.Future<java.lang.Object> ask​(ActorSelection actorSelection,
                                              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 pekko.pattern.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)). A typical reason for AskTimeoutException is that the recipient actor didn't send a reply.

        Warning: When using future callbacks, inside actors you need to carefully avoid closing over the containing actor&rsquo;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)
   f.map { response =>
     EnrichedMessage(response)
   } pipeTo nextActor

      • ask

        scala.concurrent.Future<java.lang.Object> ask​(ActorSelection actorSelection,
                                              java.lang.Object message,
                                              ActorRef sender,
                                              Timeout timeout)

      • askWithStatus

        scala.concurrent.Future<java.lang.Object> askWithStatus​(ActorRef actorRef,
                                                        java.lang.Object message,
                                                        Timeout timeout)
        Use for messages whose response is known to be a pekko.pattern.StatusReply. When a pekko.pattern.StatusReply.Success response arrives the future is completed with the wrapped value, if a pekko.pattern.StatusReply.Error arrives the future is instead failed.

      • askWithStatus

        scala.concurrent.Future<java.lang.Object> askWithStatus​(ActorRef actorRef,
                                                        java.lang.Object message,
                                                        ActorRef sender,
                                                        Timeout timeout)
        Use for messages whose response is known to be a pekko.pattern.StatusReply. When a pekko.pattern.StatusReply.Success response arrives the future is completed with the wrapped value, if a pekko.pattern.StatusReply.Error arrives the future is instead failed.