Subscribing multiple actors to Dead Letters in Akka - scala

Question

I am trying to create a simple application that has two actors:
Master actor that handles some App actions
DeadLettersListener that is supposed to handle all dead or unhandled messages
Here is the code that works perfectly:
object Hw extends App {
// creating Master actor
val masterActorSystem = ActorSystem("Master")
val master = masterActorSystem.actorOf(Props[Master], "Master")
// creating Dead Letters listener actor
val deadLettersActorSystem = ActorSystem.create("DeadLettersListener")
val listener = deadLettersActorSystem.actorOf(Props[DeadLettersListener])
// subscribe listener to Master's DeadLetters
masterActorSystem.eventStream.subscribe(listener, classOf[DeadLetter])
masterActorSystem.eventStream.subscribe(listener, classOf[UnhandledMessage])
}
According to the akka manual though, ActorSystem is a heavy object and we should create only one per application. But when I replace these lines:
val deadLettersActorSystem = ActorSystem.create("DeadLettersListener")
val listener = deadLettersActorSystem.actorOf(Props[DeadLettersListener])
with this code:
val listener = masterActorSystem.actorOf(Props[DeadLettersListener], "DeadLettersListener")
The subscription does not work any more and DeadLettersListener is not getting any Dead or Unhandled messages.
Can you please explain what am I doing wrong and give an advice how to subscribe to Dead Letters in this case?

Answer 1

I can't really imagine what are you doing wrong, I created a small example, and it seems to work:
object Hw extends App {
class Master extends Actor {
override def receive: Receive = {
case a => println(s"$a received in $self")
}
}
class DeadLettersListener extends Actor {
override def receive: Actor.Receive = {
case a => println(s"$a received in $self")
}
}
// creating Master actor
val masterActorSystem = ActorSystem("Master")
val master = masterActorSystem.actorOf(Props[Master], "Master")
val listener = masterActorSystem.actorOf(Props[DeadLettersListener])
// subscribe listener to Master's DeadLetters
masterActorSystem.eventStream.subscribe(listener, classOf[DeadLetter])
masterActorSystem.eventStream.subscribe(listener, classOf[UnhandledMessage])
masterActorSystem.actorSelection("/unexistingActor") ! "yo"
}
Could you try it?