Scala Akka Play, Future doesn't return - scala

Question

I'm using Scala 2.10, Akka 2.1 and Play 2.1. When I send an http request to my backend, I ask one actor to compute something. The idea is to return the result of the calculation if it returns before a timeout, otherwise a different string. See code below.
val futureInt: Future[Int] = ask(testActor, Calculate(number.toInt)).mapTo[Int]
val timeoutFuture = play.api.libs.concurrent.Promise.timeout("Oops", 2.seconds)
Async {
Future.firstCompletedOf(Seq(futureInt, timeoutFuture)).map {
case i: Int => Ok("Got result " + i)
case t: String => Ok("timeout expired")
}
}
The actor is as follows:
class TestActor() extends Actor {
def receive = {
case Calculate(tonumber: Int) =>
for (a <- 1 to tonumber) {
val c: Double = scala.math.pow(a, 2)
println("a: " + a + ", c: " + c)
}
12345 // hardcoded value to return when the calculation finishes
case _ =>
println("bah")
}
}
My problem is that even if the actor finishes before the timeout, nothing is "returned" by the Future and so the timeout always expires. What am I doing wrong? Thanks a lot.

Answer 1

From http://doc.akka.io/docs/akka/snapshot/scala/actors.html
Using ask will send a message to the receiving Actor as with tell, and the receiving actor must reply with sender ! reply in order to complete the returned Future with a value.
and
Warning
To complete the future with an exception you need send a Failure message to the sender. This is not done automatically when an actor throws an exception while processing a message.
So instead of "returning" like you would in a usual scala function, do something along the lines of
def receive = {
case Calculate(tonumber: Int) =>
...
sender ! 12345
case _ =>
sender ! akka.actor.Status.Failure(new InvalidArgumentException)
}