!clt #13711 Move cluster tools from contrib

* new module akka-cluster-tools containing
  cluster singleton, distributed pub-sub, and cluster client

akka-cluster-tools/src/test/java/akka/cluster/pubsub/DistributedPubSubMediatorTest.java

@@ -0,0 +1,87 @@
+/**
+ * Copyright (C) 2009-2015 Typesafe Inc. <http://www.typesafe.com>
+ */
+
+package akka.cluster.pubsub;
+
+import akka.testkit.AkkaJUnitActorSystemResource;
+import org.junit.ClassRule;
+import org.junit.Test;
+
+import akka.actor.ActorRef;
+import akka.actor.ActorSystem;
+import akka.actor.Props;
+import akka.actor.UntypedActor;
+import akka.event.Logging;
+import akka.event.LoggingAdapter;
+
+public class DistributedPubSubMediatorTest {
+
+  @ClassRule
+  public static AkkaJUnitActorSystemResource actorSystemResource =
+    new AkkaJUnitActorSystemResource("DistributedPubSubMediatorTest");
+
+  private final ActorSystem system = actorSystemResource.getSystem();
+
+
+  @Test
+  public void demonstrateUsage() {
+    //#start-subscribers
+    system.actorOf(Props.create(Subscriber.class), "subscriber1");
+    //another node
+    system.actorOf(Props.create(Subscriber.class), "subscriber2");
+    system.actorOf(Props.create(Subscriber.class), "subscriber3");
+    //#start-subscribers
+
+    //#publish-message
+    //somewhere else
+    ActorRef publisher = system.actorOf(Props.create(Publisher.class), "publisher");
+    // after a while the subscriptions are replicated
+    publisher.tell("hello", null);
+    //#publish-message
+  }
+
+  static//#subscriber
+  public class Subscriber extends UntypedActor {
+    LoggingAdapter log = Logging.getLogger(getContext().system(), this);
+
+    public Subscriber() {
+      ActorRef mediator = 
+        DistributedPubSubExtension.get(getContext().system()).mediator();
+      // subscribe to the topic named "content"
+      mediator.tell(new DistributedPubSubMediator.Subscribe("content", getSelf()), 
+        getSelf());
+    }
+
+    public void onReceive(Object msg) {
+      if (msg instanceof String)
+        log.info("Got: {}", msg);
+      else if (msg instanceof DistributedPubSubMediator.SubscribeAck)
+        log.info("subscribing");
+      else
+        unhandled(msg);
+    }
+  }
+
+  //#subscriber
+
+  static//#publisher
+  public class Publisher extends UntypedActor {
+
+    // activate the extension
+    ActorRef mediator = 
+      DistributedPubSubExtension.get(getContext().system()).mediator();
+
+    public void onReceive(Object msg) {
+      if (msg instanceof String) {
+        String in = (String) msg;
+        String out = in.toUpperCase();
+        mediator.tell(new DistributedPubSubMediator.Publish("content", out), 
+          getSelf());
+      } else {
+        unhandled(msg);
+      }
+    }
+  }
+  //#publisher
+}