Akka/Scala example source code file (SimpleClusterListener.java)

This example Akka source code file (SimpleClusterListener.java) is included in my "Source Code Warehouse" project. The intent of this project is to help you more easily find Akka and Scala source code examples by using tags.

All credit for the original source code belongs to akka.io; I'm just trying to make examples easier to find. (For my Scala work, see my Scala examples and tutorials.)

Akka tags/keywords

actor, akka, cluster, event, member, memberevent, memberremoved, memberup, override, removed, unreachablemember, untypedactor, up

The SimpleClusterListener.java Akka example source code

package sample.cluster.simple;

import akka.actor.UntypedActor;
import akka.cluster.Cluster;
import akka.cluster.ClusterEvent;
import akka.cluster.ClusterEvent.MemberEvent;
import akka.cluster.ClusterEvent.MemberUp;
import akka.cluster.ClusterEvent.MemberRemoved;
import akka.cluster.ClusterEvent.UnreachableMember;
import akka.event.Logging;
import akka.event.LoggingAdapter;

public class SimpleClusterListener extends UntypedActor {
  LoggingAdapter log = Logging.getLogger(getContext().system(), this);
  Cluster cluster = Cluster.get(getContext().system());

  //subscribe to cluster changes
  @Override
  public void preStart() {
    //#subscribe
    cluster.subscribe(getSelf(), ClusterEvent.initialStateAsEvents(), 
        MemberEvent.class, UnreachableMember.class);
    //#subscribe
  }

  //re-subscribe when restart
  @Override
  public void postStop() {
    cluster.unsubscribe(getSelf());
  }

  @Override
  public void onReceive(Object message) {
    if (message instanceof MemberUp) {
      MemberUp mUp = (MemberUp) message;
      log.info("Member is Up: {}", mUp.member());

    } else if (message instanceof UnreachableMember) {
      UnreachableMember mUnreachable = (UnreachableMember) message;
      log.info("Member detected as unreachable: {}", mUnreachable.member());

    } else if (message instanceof MemberRemoved) {
      MemberRemoved mRemoved = (MemberRemoved) message;
      log.info("Member is Removed: {}", mRemoved.member());

    } else if (message instanceof MemberEvent) {
      // ignore

    } else {
      unhandled(message);
    }

  }
}