How to broadcast message to all actors in an AKKA cluster in java?

Question

I have an AKKA cluster system with name say ClusterSystem. Each node of this cluster have an actor ActorA. I want a way to broadcast a message sent to an actor to all the ActoraA-s running in the cluster.

It would be of great help if any one can post an example in Java.

Answer 1

Check out the Distributed Publish Subscribe extension. It lets you subscribe one or more actors to a topic, and publish messages to this topic from any actor in the cluster.

Subscribing:

class Subscriber extends Actor with ActorLogging {
  import DistributedPubSubMediator.{ Subscribe, SubscribeAck }
  val mediator = DistributedPubSub(context.system).mediator
  // subscribe to the topic named "content"
  mediator ! Subscribe("content", self)

  def receive = {
    case s: String ⇒
      log.info("Got {}", s)
    case SubscribeAck(Subscribe("content", None, `self`)) ⇒
      log.info("subscribing");
  }
}

Publishing:

class Publisher extends Actor {
  import DistributedPubSubMediator.Publish
  // activate the extension
  val mediator = DistributedPubSub(context.system).mediator

  def receive = {
    case in: String ⇒
      val out = in.toUpperCase
      mediator ! Publish("content", out)
  }
}

Code examples and additional explanation here.

Answer 2

There is an special type of message for this task. You can send a Broadcast message to a router and it will be received by all the routees.

router.tell(new Broadcast("Watch out for Davy Jones' locker"), getTestActor());

You can also create a BroadcastPool and BroadcastGroup in case that you need to broadcast every single message.

You can find more information about both options in this link.