Question

I’m making a small caching actor with Akka 2 and to make the actor not block I perform all calculations inside futures. However a problem is that this actor also need to interact with with code that is not itself in an actor, so that I need to use the “ask” pattern to get a value.

My question is, how do I avoid wrapping the Future of my calculation inside another Future when using the ask pattern?

For example

val f = myCache ? GetOrCalc("myKey", myCalculation) // this will be a Future[Future[...]] but I would like a Future[...]

// meanwhile, inside the actor
def receive = {
    case GetOrCalc(key, calculation) =>
        if (keyNotExists) sender ! Future { calculation() } // calculation() is long-running
        else sender ! cacheMap(key)
}

Ideally I could use the Future.pipeTo function but I’m afraid this doesn’t get counted as a “response” for non-actor code

Answer 1

This is the solution:

val f = myCache ? GetOrCalc("myKey", myCalculation)

def receive = {
    case GetOrCalc(key, calculation) =>
        if (keyNotExists) Future { calculation() } pipeTo sender
        else sender ! cacheMap(key)
}

Send-And-Receive-Future”>http://doc.akka.io/docs/akka/2.0.3/scala/actors.html#Ask_Send-And-Receive-Future