Akka Actors - Creating Pool of Actors - scala

Question

I created the following Akka Actor code in Scala. Code works fine when a single workerActor is created. But code silently fails when I try to create a pool of worker actors using round robin logic. Any idea how to fix this? How do I get more debug info to be printed?
import scala.collection.immutable.Map
import scala.collection.mutable.ArrayBuffer
import akka.actor.actorRef2Scala
import akka.actor.ActorSystem
import akka.actor.Props
import scala.concurrent.Await
import scala.concurrent.duration._
import akka.pattern.ask
import akka.util.Timeout
import akka.actor._
import org.junit._
import org.junit.Assert._
import messaging.actors._
import akka.routing.RoundRobinRouter
import akka.routing._
class MainEngineActorTest {
#Test
def testMainActor () = {
val _system = ActorSystem("MainEngineActor")
val master = _system.actorOf(Props[MainEngineActor], name = "EngineActor")
println ("Created Main Engine Actor")
implicit val timeout = Timeout(5 seconds)
val userID = new UserID ("test1")
println ("Sending messages")
for (i <- ( 1 to 10)) {
master ! "Hello"
master ! "World"
}
}
}
class MainEngineActor extends Actor with ActorLogging{
// works if we create only a single workerActor
//val workerActors = context.actorOf(Props[WorkerActor], name = "WorkerActors")
// Doesn't work when we create a pool of worker actors - how do we fix this?
// why doesn't this work and why aren't any error messages printed?
val workerActors = context.actorOf(RoundRobinPool(5).props(Props[WorkerActor]), name = "WorkerActors")
def receive: Receive = {
case request => {
workerActors forward request
}
}
}
class WorkerActor extends Actor {
def receive: Receive = {
case request => {
println ("RequestReceived =" + request)
}
}
}

Answer 1

Try creating your pool like this instead:
val workerActors = context.actorOf(Props[WorkerActor].withRouter(RoundRobinPool(5)), name = "WorkerActors")
In addition, when running this as a Junit test, the program is terminating before the child actors have a chance to receive the message. I verified this by adding a Thread.sleep(5000) after the loop that is sending the Hello and World messages to master. I then tweaked your code a little bit to use Akka's TestActorRef from akka-testkit which will force everything to use the CallingThreadDispatcher to get synchronous execution throughout the test and everything works as expected. The two lines I changed are:
implicit val _system = ActorSystem("MainEngineActor")
val master = TestActorRef(new MainEngineActor())