Get a message out of an Akka Actor - scala

Question

I've built an Akka actor that queries an API at regular intervals, like this:
val cancellable =
system.scheduler.schedule(0 milliseconds,
5 seconds,
actor,
QueryController(1))
The Actor, in essence is:
object UpdateStatistics {
/**
* Query the controller for the given switch Id
*
* #param dpId Switch's Id
*/
case class QueryController(dpId: Int)
case object Stop
def props: Props = Props[UpdateStatistics]
}
class UpdateStatistics extends Actor with akka.actor.ActorLogging {
import UpdateStatistics._
def receive = {
case QueryController(id) =>
import context.dispatcher
log.info(s"Receiving request to query controller")
Future { FlowCollector.getSwitchFlows(1) } onComplete {
f => self ! f.get
}
case Stop =>
log.info(s"Shuting down")
context stop self
case json: JValue =>
log.info("Getting json response, computing features...")
val features = FeatureExtractor.getFeatures(json)
log.debug(s"Features: $features")
sender ! features
case x =>
log.warning("Received unknown message: {}", x)
}
}
What I am trying to do is get the json:Jvalue message out of UpdateStatistics actor. Reading the Akka docs I thought this may be useful:
implicit val i = inbox()
i.select() {
case x => println(s"Valor Devuelto $x")
}
println(i receive(2.second))
But I do not know how to modify UpdateStatistics actor in order to send the result to the inbox above.
Another option I've read in the docs are event streams.
But I do not think this is the correct way.
Is there a way of achieving what I want to do? Or do I need to use a second Actor to which I send the JSON response?

Answer 1

You probably are looking for the ask pattern in AKKA. This will allow you to return a value to the sender.
import akka.pattern.ask
import akka.util.duration._
implicit val timeout = Timeout(5 seconds)
val future = actor ? QueryController(1)
val result = Await.result(future, timeout.duration).asInstanceOf[JValue]
println(result)
To make this work, you need to send the response to the original sender, rather than self. Also, you should beware the dangers of closing over sender in a future when handling messages.