Akka DistributedPubSubExtension multi-node cluster sample

AkkaDistributedPubSub.scala

package test.akka

import akka.actor.Actor.Receive
import akka.actor.{Props, ActorLogging, Actor, ActorSystem}
import akka.cluster.Cluster
import akka.contrib.pattern.DistributedPubSubExtension
import akka.contrib.pattern.DistributedPubSubMediator.{SubscribeAck, Subscribe, Publish}
import com.typesafe.config.ConfigFactory

/**
 * Created by 
 * @author Basel Darvish
 */
object AkkaDistributedPubSub extends App{
  val systemC1 = ActorSystem("system1", ConfigFactory.load("c1"))
  val systemC2 = ActorSystem("system1", ConfigFactory.load("c2"))
  Thread.sleep(10000)//waiting for cluster to initiate

  systemC1.actorOf(Props(classOf[Subscriber]))
  Thread.sleep(3000)//waiiting for subscriber to initiate
  val publisher = systemC2.actorOf(Props(classOf[Publisher]))
  publisher ! "Hey!"
}
class Subscriber extends Actor with ActorLogging {

  val mediator = DistributedPubSubExtension(context.system).mediator
  mediator ! Subscribe("t", self)
  log info("subscribed to: {}", "t")
  def receive = {
    case SubscribeAck(Subscribe("t", _, `self`)) ⇒
      context become ready
  }

  def ready: Receive = {
    case s:String =>
      log info("++++++++++++++++ Received message: {}", s)
    case a:Any =>
      log info("Received unknown message: {}", a)
  }
}
class Publisher extends Actor with ActorLogging {
  val mediator = DistributedPubSubExtension(context.system).mediator
  override def receive: Receive = {
    case s:String =>
      log info("________________Publishing message: {}", s)
      mediator ! Publish("t", s)
  }
}

c1.conf

akka{
  extensions = ["akka.contrib.pattern.DistributedPubSubExtension"]
  actor {
    provider = "akka.cluster.ClusterActorRefProvider"
  }
  remote {
    netty.tcp {
      hostname = "127.0.0.1"
      port = 2552
    }
  }
  cluster {
    seed-nodes = [
      "akka.tcp://system1@127.0.0.1:2552"
      "akka.tcp://system1@127.0.0.1:2551"]
    auto-down = on
    auto-down-unreachable-after = 5s
  }
}

c2.conf

akka{
  extensions = ["akka.contrib.pattern.DistributedPubSubExtension"]
  actor {
    provider = "akka.cluster.ClusterActorRefProvider"
  }
  remote {
    netty.tcp {
      hostname = "127.0.0.1"
      port = 2551
    }
  }
  cluster {
    seed-nodes = [
      "akka.tcp://system1@127.0.0.1:2552",
      "akka.tcp://system1@127.0.0.1:2551"]
    auto-down = on
    auto-down-unreachable-after = 5s
  }
}