Could not send a message to Remote Actor in akka using java.

[Hariharan LakshmiNarayanan]

I am new to Akka and I read some documentation and I am trying to send message to a remote actor (In a different jvm in the same machine).

I have attached the code for my program


Hero.java

import akka.actor.UntypedActor;

public class Hero extends UntypedActor {

    @Override
    public void onReceive(Object arg0) throws Exception {
        System.out.println("Received = " + arg0);
    }

}


TestHero.java

import akka.actor.ActorRef;
import akka.actor.ActorSystem;
import akka.actor.Props;

public class TestHero {
   
    public static void main(String[] args) {
        ActorSystem system = ActorSystem.create("testHero");
        ActorRef master = system.actorOf(Props.create(Hero.class), "master");
        System.out.println(master.path());
        master.tell("I am here", ActorRef.noSender());
    }

}

application.conf for running TestHero.java (through vm argument)

akka {
    actor {
        provider = "akka.remote.RemoteActorRefProvider"
    }
    remote {
        enabled-transports = ["akka.remote.netty.tcp"]
        netty.tcp {
            hostname = "localhost"
            port = 2009
        }
    }
}



Messenger.java

import akka.actor.ActorRef;
import akka.actor.ActorSelection;
import akka.actor.ActorSystem;
import akka.actor.Props;
import akka.actor.UntypedActor;

public class Messenger extends UntypedActor {
   
    public Messenger() {
       
       
    }

    @Override
    public void onReceive(Object arg0) throws Exception {
        System.out.println("msg = " + arg0);
        ActorSelection master = ActorSystem.create("msngr").actorSelection("akka.tcp://testHero@localhost:2009/user/master");
        System.out.println(master);
        master.tell(arg0, getSelf());
    }
   
   
    public static void main(String[] args) {
        ActorSystem system = ActorSystem.create("test");
        ActorRef actor = system.actorOf(Props.create(Messenger.class), "msgnr");
        actor.tell("Hi", null);
    }

}

When I run TestHero.java I get the following output in the console.

[INFO] [05/16/2015 22:35:11.856] [main] [Remoting] Starting remoting
[INFO] [05/16/2015 22:35:12.215] [main] [Remoting] Remoting started; listening on addresses :[akka.tcp://testHero@localhost:2009]
[INFO] [05/16/2015 22:35:12.217] [main] [Remoting] Remoting now listens on addresses: [akka.tcp://testHero@localhost:2009]
akka://testHero/user/master
Received = I am here

When I run Messenger.java I get the following output

msg = Hi
ActorSelection[Anchor(akka://msngr/deadLetters), Path(/user/master)]
[INFO] [05/16/2015 22:37:51.462] [msngr-akka.actor.default-dispatcher-7] [akka://msngr/deadLetters] Message [java.lang.String] from Actor[akka://test/user/msgnr#149375712] to Actor[akka://msngr/deadLetters] was not delivered. [1] dead letters encountered. This logging can be turned off or adjusted with configuration settings 'akka.log-dead-letters' and 'akka.log-dead-letters-during-shutdown'.

I could not understand why it is not delivered to Hero actor.

Can any one please clarify?

[Patrik Nordwall]

Try to replace ActorSystem.create("msngr") with getContext().system().

Creating a new ActorSystem for each message is not something you should do.

You might find this Activator Tutorial a good starting point: https://www.typesafe.com/activator/template/akka-sample-remote-java

Regards,

Patrik

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Patrik Nordwall
Typesafe -  Reactive apps on the JVM
Twitter: @patriknw