1.什么是Akka remoting？

Akka-Remoting一种ActorSystem之间Actor对Actor点对点的沟通协议.通过Akka-Remoting来实现一个ActorSystem中的一个Actor与另一个ActorSystem中的另一个Actor之间的沟通

Akka Remoting限制：

• 不支持NAT（Network Address Translation）
• 不支持负载均衡器（Load Balancers）

Akka提供了种方式来使用Remoting功能：

• 通过调用actorSelection方法搜索一个actor，该方法输入的参数的模式为：akka.<protocol>://<actor system>@<hostname>:<port>/<actor path>
• 通过actorOf方法创建一个actor

下面看一下Remoting系统中故障恢复模型（Failure Recovery Model），如下图所示：

上图中，连接到一个远程系统的过程中，包括上面4种状态：在进行任何通信之前，系统处于Idle状态；当第一次一个消息尝试向远程系统发送，或者当远程系统连接过来，这时系统状态变为Active；当两个系统通信失败，连接丢失，这时系统变为Gated状态；当系统通信过程中，由于参与通信的系统的状态不一致导致系统无法恢复，这时远程系统变为Quarantined状态，只有重新启动系统才能恢复，重启后系统变为Active状态。

Akka Remoting功能：

Akka将remoting完全配置化了，使用时几乎只需要修改配置文件，除非自定义，否则不需要动一行代码。 remoting包提供了两个功能：

• 查找一个已存在的远程Actor
• 在指定的远程路径上创建一个远程Actor

2.代码管理

实验目标

实现客户端和服务端通信

pom.xml

<!-- Akka Streams -->
<dependency>
    <groupId>com.typesafe.akka</groupId>
    <artifactId>akka-stream_2.13</artifactId>
    <version>2.6.0</version>
</dependency>

server

server.conf

akka {
  actor {
    provider = "akka.remote.RemoteActorRefProvider"
  }
  remote {
    artery {
      enabled = on
      transport = tcp
      canonical.hostname = "127.0.0.1"
      canonical.port = 2552
    }
  }
}

package com.et.akka.remoting;

import akka.actor.AbstractActor;
import akka.actor.ActorRef;
import akka.actor.ActorSystem;
import akka.actor.Props;
import com.typesafe.config.ConfigFactory;

public class ServerApp {

    static class ServerActor extends AbstractActor {
        @Override
        public Receive createReceive() {
            return receiveBuilder()
                    .match(String.class, msg -> {
                        System.out.println("Server received message: " + msg);
                        getSender().tell("Hello from Server", getSelf());
                    })
                    .build();
        }
    }

    public static void main(String[] args) {
        ActorSystem system = ActorSystem.create("RemoteSystem", ConfigFactory.load("server"));
        ActorRef serverActor = system.actorOf(Props.create(ServerActor.class), "serverActor");
        System.out.println("Server is running...");
    }
}

client

client.conf

akka {
  actor {
    provider = "akka.remote.RemoteActorRefProvider"
  }
  remote {
    artery {
      enabled = on
      transport = tcp
      canonical.hostname = "127.0.0.1"
      canonical.port = 0
    }
  }
}

package com.et.akka.remoting;

import akka.actor.AbstractActor;
import akka.actor.ActorRef;
import akka.actor.ActorSelection;
import akka.actor.ActorSystem;
import akka.actor.Props;
import com.typesafe.config.ConfigFactory;

public class ClientApp {

    static class ClientActor extends AbstractActor {

        private final String serverActorPath;

        public ClientActor(String serverActorPath) {
            this.serverActorPath = serverActorPath;
        }

        @Override
        public void preStart() {
            ActorSelection serverActor = getContext().actorSelection(serverActorPath);
            serverActor.tell("Hello from Client", getSelf());
        }

        @Override
        public Receive createReceive() {
            return receiveBuilder()
                    .match(String.class, msg -> {
                        System.out.println("Client received message: " + msg);
                    })
                    .build();
        }
    }

    public static void main(String[] args) {
        ActorSystem system = ActorSystem.create("RemoteSystem", ConfigFactory.load("client"));
        String serverPath = "akka://RemoteSystem@127.0.0.1:2552/user/serverActor";
        ActorRef clientActor = system.actorOf(Props.create(ClientActor.class, serverPath), "clientActor");
        System.out.println("Client is running...");
    }
}

以上只是一些关键代码，所有代码请参见下面代码仓库

代码仓库

• GitHub - Harries/springboot-demo: a simple springboot demo with some components for example: redis,solr,rockmq and so on.(akka)

3.测试

1. 启动server
2. 启动client
3. 产看日志

server

Server is running...
Server received message: Hello from Client

client

Client is running...
Client received message: Hello from Server

4.引用

• https://doc.akka.io/docs/akka/current/remoting.html
• https://doc.akka.io/docs/akka/current/remoting-artery.html#selecting-a-transport
• Spring Boot集成Akka remoting快速入门Demo | Harries Blog™