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

This example Akka source code file (ClusterShardingTest.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, actorref, akka, concurrent, counter, counterchanged, duration, entryenvelope, get, object, override, persistence, procedure, string, time, untypedpersistentactor

The ClusterShardingTest.java Akka example source code

/**
 * Copyright (C) 2009-2014 Typesafe Inc. <http://www.typesafe.com>
 */

package akka.contrib.pattern;

import java.util.concurrent.TimeUnit;

import scala.concurrent.duration.Duration;
import akka.actor.ActorRef;
import akka.actor.ActorSystem;
import akka.actor.PoisonPill;
import akka.actor.Props;
import akka.actor.ReceiveTimeout;
import akka.japi.Procedure;
import akka.persistence.UntypedPersistentActor;

// Doc code, compile only
public class ClusterShardingTest {

  ActorSystem system = null;

  ActorRef getSelf() {
    return null;
  }

  public void demonstrateUsage() {
    //#counter-extractor
    ShardRegion.MessageExtractor messageExtractor = new ShardRegion.MessageExtractor() {

      @Override
      public String entryId(Object message) {
        if (message instanceof Counter.EntryEnvelope)
          return String.valueOf(((Counter.EntryEnvelope) message).id);
        else if (message instanceof Counter.Get)
          return String.valueOf(((Counter.Get) message).counterId);
        else
          return null;
      }

      @Override
      public Object entryMessage(Object message) {
        if (message instanceof Counter.EntryEnvelope)
          return ((Counter.EntryEnvelope) message).payload;
        else
          return message;
      }

      @Override
      public String shardId(Object message) {
        if (message instanceof Counter.EntryEnvelope) {
          long id = ((Counter.EntryEnvelope) message).id;
          return String.valueOf(id % 10);
        } else if (message instanceof Counter.Get) {
          long id = ((Counter.Get) message).counterId;
          return String.valueOf(id % 10);
        } else {
          return null;
        }
      }

    };
    //#counter-extractor

    //#counter-start
    ActorRef startedCounterRegion = ClusterSharding.get(system).start("Counter", Props.create(Counter.class),
              messageExtractor);
    //#counter-start

    //#counter-usage
    ActorRef counterRegion = ClusterSharding.get(system).shardRegion("Counter");
    counterRegion.tell(new Counter.Get(100), getSelf());

    counterRegion.tell(new Counter.EntryEnvelope(100,
        Counter.CounterOp.INCREMENT), getSelf());
    counterRegion.tell(new Counter.Get(100), getSelf());
    //#counter-usage
  }

  static//#counter-actor
  public class Counter extends UntypedPersistentActor {

    public static enum CounterOp {
      INCREMENT, DECREMENT
    }

    public static class Get {
      final public long counterId;

      public Get(long counterId) {
        this.counterId = counterId;
      }
    }

    public static class EntryEnvelope {
      final public long id;
      final public Object payload;

      public EntryEnvelope(long id, Object payload) {
        this.id = id;
        this.payload = payload;
      }
    }

    public static class CounterChanged {
      final public int delta;

      public CounterChanged(int delta) {
        this.delta = delta;
      }
    }

    int count = 0;
    
    // getSelf().path().parent().name() is the type name (utf-8 URL-encoded) 
    // getSelf().path().name() is the entry identifier (utf-8 URL-encoded)
    @Override
    public String persistenceId() {
      return getSelf().path().parent().name() + "-" + getSelf().path().name();
    }

    @Override
    public void preStart() throws Exception {
      super.preStart();
      context().setReceiveTimeout(Duration.create(120, TimeUnit.SECONDS));
    }

    void updateState(CounterChanged event) {
      count += event.delta;
    }

    @Override
    public void onReceiveRecover(Object msg) {
      if (msg instanceof CounterChanged)
        updateState((CounterChanged) msg);
      else
        unhandled(msg);
    }

    @Override
    public void onReceiveCommand(Object msg) {
      if (msg instanceof Get)
        getSender().tell(count, getSelf());

      else if (msg == CounterOp.INCREMENT)
        persist(new CounterChanged(+1), new Procedure<CounterChanged>() {
          public void apply(CounterChanged evt) {
            updateState(evt);
          }
        });

      else if (msg == CounterOp.DECREMENT)
        persist(new CounterChanged(-1), new Procedure<CounterChanged>() {
          public void apply(CounterChanged evt) {
            updateState(evt);
          }
        });

      else if (msg.equals(ReceiveTimeout.getInstance()))
        getContext().parent().tell(
            new ShardRegion.Passivate(PoisonPill.getInstance()), getSelf());

      else
        unhandled(msg);
    }
  }

  //#counter-actor

}

Other Akka source code examples

Here is a short list of links related to this Akka ClusterShardingTest.java source code file:

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