Akka Futures Exceptions - scala

Question

What happens when an actor of a future throws an exception?
According to the Akka documentation at http://doc.akka.io/docs/akka/snapshot/scala/futures.html:
It doesn't matter if an Actor or the dispatcher is completing the
Future, if an Exception is caught the Future will contain it instead
of a valid result. If a Future does contain an Exception, calling
Await.result will cause it to be thrown again so it can be handled
properly.
I am not sure this is what I am seeing when running this piece of code:
class Worker extends Actor {
def receive = {
case i: Int => throw new RuntimeException
}
}
implicit val system = ActorSystem("MySystem")
val worker = system.actorOf(Props(new Worker), name="worker")
implicit val timeout = Timeout(5 minutes)
val future = worker ? 0
val res = Await.result(future, 10 seconds)
According to the documentation, Await.result should throw the exception again, but what I am getting is a TimeoutException! Can someone clarify on this?

Answer 1

For actors you need to catch the exception and return it as a failure status. Right now you're not returning anything to the sender so you're getting a timeout exception:
class Worker extends Actor {
def receive = {
case i: Int => {
try {
throw new RuntimeException
sender ! "Some good result"
} catch {
case e: Exception =>
sender ! akka.actor.Status.Failure(e) // Alert the sender of the failure
throw e // Alert any supervisor actor of the failure
}
}
}
}
Futures can handle this a little more gracefully since they always send a result, while actors do not (this would give you the same result as above):
val future = Future {
throw new RuntimeException
}