CODEWITHSUNDEEP
scalaakka
igx
igx

Reputation: 4231

howto verify that akka actor exists by name

I am trying to send a message to an actor using the actor selection . but it keeps getting to dead letters . This how the actor is created (using the activator template)

class PongActor extends Actor with ActorLogging {
  import PongActor._

  def receive = {
    case PingActor.PingMessage(text) => 
      log.info("In PongActor - received message: {}", text)
      sender() ! PongMessage("pong")
  } 
}

object PongActor {
  val props = Props[PongActor]
  case class PongMessage(text: String)
}

This is the sending actor :

class PingActor extends Actor with ActorLogging {
  import PingActor._

  var counter = 0
  val pongActor = context.actorOf(PongActor.props, "pongActor")
val tester = context.actorSelection("../pongActor") //getting the actor by name using the actorSelection 
  def receive = {
    case Initialize => 
        log.info("In PingActor - starting ping-pong")
      tester.tell(PingMessage("ping"),self)//going to dead letters
      tester ! PingMessage("ping")//also going to dead letters 
    case PongActor.PongMessage(text) =>
      log.info("In PingActor - received message: {}", text)
      counter += 1
      if (counter == 3) context.system.shutdown()
      else sender() ! PingMessage("ping")
  } 
}

object PingActor {
  val props = Props[PingActor]
  case object Initialize
  case class PingMessage(text: String)
}

  1. why the messages are getting to the dead letters

  2. how can I verify that the actor really exists ?

Upvotes: 1

Views: 1018

Answers (2)

Johny T Koshy
Johny T Koshy

Reputation: 3887

From akka- docs

actorSelection only ever looks up existing actors when messages are delivered, i.e. does not create actors, or verify existence of actors when the selection is created.

A better option is to use resolveOne

val timeout = 1.seconds
val tester1 = context.actorSelection("pongActor").resolveOne(timeout)

Upvotes: 3

Shadowlands
Shadowlands

Reputation: 15074

Your line val tester = context.actorSelection("../pongActor") is unnecessary, as the previous line sets pongActor to the actorRef you need. Just use pongActor.tell and pongActor ! instead of tester.tell and tester !.

As for why the actorSelection lookup is failing: when you create a child actor inside a parent actor (here Ping is the parent, Pong is the child), the path to the child is the same as the path to the parent, with the child's name appended. So, relative to Ping, the path to Pong is just "pongActor", not "../pongActor".

Upvotes: 2

Related Questions