This object contains implementation details of the “ask” pattern.
This is what is used to complete a Future that is returned from an ask/? call, when it times out.
Provides circuit breaker functionality to provide stability when working with "dangerous" operations, e.
Exception thrown when Circuit Breaker is open.
Companion object providing factory methods for Circuit Breaker which runs callbacks in caller's thread
Returns a scala.concurrent.Future that will be completed with the success or failure of the provided value after the specified duration.
Returns a scala.concurrent.Future that will be completed with the success or failure of the provided value after the specified duration.
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.
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)
).
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 scala.concurrent.Future for a description of flow
Import this implicit conversion to gain ?
and ask
methods on
akka.actor.ActorRef, which will defer to the
ask(actorRef, message)(timeout)
method defined here.
Import this implicit conversion to gain ?
and ask
methods on
akka.actor.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.
Returns a scala.concurrent.Future that will be completed with success (value true
) when
existing messages of the target actor has been processed and the actor has been
terminated.
Returns a scala.concurrent.Future that will be completed with success (value true
) when
existing messages of the target actor has been processed and the actor has been
terminated.
Useful when you need to wait for termination or compose ordered termination of several actors, which should only be done outside of the ActorSystem as blocking inside Actors is discouraged.
IMPORTANT NOTICE: the actor being terminated and its supervisor being informed of the availability of the deceased actor’s name are two distinct operations, which do not obey any reliable ordering. Especially the following will NOT work:
def receive = { case msg => Await.result(gracefulStop(someChild, timeout), timeout) context.actorOf(Props(...), "someChild") // assuming that that was someChildᅰs name, this will NOT work }
If the target actor isn't terminated within the timeout the scala.concurrent.Future is completed with failure akka.pattern.AskTimeoutException.
Import this implicit conversion to gain the pipeTo
method on scala.concurrent.Future:
Import this implicit conversion to gain the pipeTo
method on scala.concurrent.Future:
import akka.pattern.pipe
Future { doExpensiveCalc() } pipeTo nextActor
or
pipe(someFuture) to nextActor
Commonly Used Patterns With Akka
This package is used as a collection point for usage patterns which involve actors, futures, etc. but are loosely enough coupled to (multiple of) them to present them separately from the core implementation. Currently supported are:
In Scala the recommended usage is to import the pattern from the package object:
For Java the patterns are available as static methods of the akka.pattern.Patterns class:
import static akka.pattern.Patterns.ask; ask(actor, message);