Sends a message asynchronously and returns a scala.concurrent.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 akka.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’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, replyTo => Request(replyTo))(timeout)
f.map { response =>
  EnrichedMessage(response)
} pipeTo nextActor

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

import akka.pattern.ask

// same as `ask(selection, askSender => Request(askSender))`
val future = selection ? { askSender => Request(askSender) }

// same as `ask(selection, Request(_))`
val future = selection ? (Request(_))

// same as `ask(selection, Request(_))(timeout)`
val future = selection ? (Request(_))(timeout)

All of the above use a required implicit akka.util.Timeout and optional implicit sender akka.actor.ActorRef.

Sends a message asynchronously and returns a scala.concurrent.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 akka.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’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, replyTo => Request(replyTo))(timeout)
f.map { response =>
  EnrichedMessage(response)
} pipeTo nextActor

Import this implicit conversion to gain ? and ask methods on akka.actor.ActorRef, which will defer to the ask(actorRef, askSender => message)(timeout) method defined here.

import akka.pattern.ask

// same as `ask(actor, askSender => Request(askSender))`
val future = actor ? { askSender => Request(askSender) }

// same as `ask(actor, Request(_))`
val future = actor ? (Request(_))

// same as `ask(actor, Request(_))(timeout)`
val future = actor ? (Request(_))(timeout)

All of the above use a required implicit akka.util.Timeout and optional implicit sender akka.actor.ActorRef.