Akka 实践之(三) 远程部署

Akka 可以支持客户端和服务端远程部署，这点对与高并发分布式调用非常有利。 在上篇的代码基础上，新增2个类，LookupActor和LookupApplication.java

1、首先看一下类图

2、 源码

在本例中，将远程创建CalculatorActor 对象，然后通过指定path的方式创建这个对象的远程Actor（其实我认为是这个对象的代理）

<span style="font-family:Microsoft YaHei;font-size:14px;">    final String path = "akka.tcp://[email protected]:8552/user/calculator";
    final ActorRef actor = system.actorOf( Props.create(LookupActor.class, path), "lookupActor");</span>

LookupActor和 LookupApplication的源码如下，重点关注是如何创建远程对象，以及如何获取对远程对象的使用。

<span style="font-family:Microsoft YaHei;font-size:14px;">package com.cwqsolo.study.akka.demo;

import static java.util.concurrent.TimeUnit.SECONDS;
import scala.concurrent.duration.Duration;
import akka.actor.ActorRef;
import akka.actor.ActorIdentity;
import akka.actor.Identify;
import akka.actor.Terminated;
import akka.actor.UntypedActor;
import akka.actor.ReceiveTimeout;
import akka.japi.Procedure;

public class LookupActor extends UntypedActor {

  private final String path;
  private ActorRef calculator = null;

  public LookupActor(String path) {
    this.path = path;
    sendIdentifyRequest();
  }

  private void sendIdentifyRequest() {
    getContext().actorSelection(path).tell(new Identify(path), getSelf());
    getContext()
        .system()
        .scheduler()
        .scheduleOnce(Duration.create(3, SECONDS), getSelf(),
            ReceiveTimeout.getInstance(), getContext().dispatcher(), getSelf());
  }

  @Override
  public void onReceive(Object message) throws Exception {
    if (message instanceof ActorIdentity) {
      calculator = ((ActorIdentity) message).getRef();
      if (calculator == null) {
        System.out.println("Remote actor not available: " + path);
      } else {
        getContext().watch(calculator);
        getContext().become(active, true);
      }

    } else if (message instanceof ReceiveTimeout) {
      sendIdentifyRequest();

    } else {
      System.out.println("Not ready yet");

    }
  }

  Procedure<Object> active = new Procedure<Object>() {
    @Override
    public void apply(Object message) {
      if (message instanceof Op.MathOp) {
        // send message to server actor
        calculator.tell(message, getSelf());

      } else if (message instanceof Op.AddResult) {
        Op.AddResult result = (Op.AddResult) message;
        System.out.printf("Add result: %d + %d = %d\n", result.getN1(),
            result.getN2(), result.getResult());

      } else if (message instanceof Op.SubtractResult) {
        Op.SubtractResult result = (Op.SubtractResult) message;
        System.out.printf("Sub result: %d - %d = %d\n", result.getN1(),
            result.getN2(), result.getResult());

      } else if (message instanceof Terminated) {
        System.out.println("Calculator terminated");
        sendIdentifyRequest();
        getContext().unbecome();
        
        

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

      } else {
        unhandled(message);
      }

    }
  };
}
</span>

可以看到LookupActor 与上节中的CreationActor类没有什么区别，重点是LookupApplication类源码。

<span style="font-family:Microsoft YaHei;font-size:14px;">package com.cwqsolo.study.akka.demo;
import static java.util.concurrent.TimeUnit.SECONDS;

import java.util.Random;

//import scala.concurrent.duration.Duration;
//import akka.actor.ActorRef;
//import akka.actor.ActorSystem;
//import akka.actor.Props;
import com.typesafe.config.ConfigFactory;

import java.util.Arrays;  
import java.util.concurrent.Callable;    
import scala.concurrent.*;
import scala.concurrent.duration.Duration;
import akka.actor.ActorRef;  
import akka.actor.ActorSystem;  
import akka.actor.Props;  

public class LookupApplication {
  public static void main(String[] args) {
    if (args.length == 0 || args[0].equals("Calculator"))
      startRemoteCalculatorSystem();
    if (args.length == 0 || args[0].equals("Lookup"))
      startRemoteLookupSystem();
    
   }

  public static void startRemoteCalculatorSystem() {
<span style="color:#ff0000;">    final ActorSystem system = ActorSystem.create("CalculatorSystem",
        ConfigFactory.load(("calculator")));</span>
    <span style="color:#ff0000;">final ActorRef calActor = system.actorOf(Props.create(CalculatorActor.class), "calculator");</span>
    //calActor.
    System.out.println("Started CalculatorSystem");
  }

  public static void startRemoteLookupSystem() {

    <span style="color:#ff0000;">final ActorSystem system = ActorSystem.create("LookupSystem",
        ConfigFactory.load("remotelookup"));</span>
<span style="color:#ff0000;">    final String path = "akka.tcp://[email protected]:8552/user/calculator";
    final ActorRef actor = system.actorOf(
        Props.create(LookupActor.class, path), "lookupActor");</span>

    System.out.println("Started LookupSystem");
    final Random r = new Random();
    system.scheduler().schedule(Duration.create(1, SECONDS),
        Duration.create(1, SECONDS), new Runnable() {
          @Override
          public void run() {
            if (r.nextInt(100) % 2 == 0) {
              actor.tell(new Op.Add(r.nextInt(100), r.nextInt(100)), null);
            } else {
              actor.tell(new Op.Subtract(r.nextInt(100), r.nextInt(100)), null);
            }

          }
        }, system.dispatcher());

  }
}</span>

标红代码这里要注意，这里是关键，而且可以看到，这里用到了配置文件（一开始，这里没有搞懂，运行起来都是无法找到远程对象）

配置文件有3个

common.conf

<span style="font-family:Microsoft YaHei;font-size:14px;">[root@archive akka]# cat  common.conf
akka {  
  actor {  
    provider = "akka.remote.RemoteActorRefProvider"  
  }  
  
  remote {  
     enabled-transports = ["akka.remote.netty.tcp"]  
    netty.tcp {  
      hostname = "127.0.0.1"  
    }  
  }  
}</span>

<span style="font-family:Microsoft YaHei;font-size:14px;">[root@archive akka]# cat  calculator.conf
include "common"  
  
akka {  
  # LISTEN on tcp port 2552  
  remote.netty.tcp.port = 8552  
}  </span>

<span style="font-family:Microsoft YaHei;font-size:14px;">[root@archive akka]# cat  remotelookup.conf 
include "common"

akka {
  remote.netty.tcp.port = 2553
}</span>

从上面的配置文件可以看到， calculator对象在8552端口进行监听，  lookup对象通过remotelookup创建了 2553端口的监听，lookup对象通过path 获取

到calculator对象的引用（代理），然后就可以进行对象间的调用。

3、执行结果

[root@archive akka]# sh  ./start.sh
java version "1.7.0_80"
Java(TM) SE Runtime Environment (build 1.7.0_80-b15)
Java HotSpot(TM) 64-Bit Server VM (build 24.80-b11, mixed mode)
[INFO] [10/27/2016 16:48:26.956] [main] [Remoting] Starting remoting
[INFO] [10/27/2016 16:48:27.234] [main] [Remoting] Remoting started; listening on addresses :[akka.tcp://[email protected]:8552]
[INFO] [10/27/2016 16:48:27.236] [main] [Remoting] Remoting now listens on addresses: [akka.tcp://[email protected]:8552]
Started CalculatorSystem
[INFO] [10/27/2016 16:48:27.311] [main] [Remoting] Starting remoting
[INFO] [10/27/2016 16:48:27.339] [main] [Remoting] Remoting started; listening on addresses :[akka.tcp://[email protected]:2553]
[INFO] [10/27/2016 16:48:27.339] [main] [Remoting] Remoting now listens on addresses: [akka.tcp://[email protected]:2553]
Started LookupSystem
Calculating 9 - 61
Sub result: 9 - 61 = -52
Calculating 51 - 86
Sub result: 51 - 86 = -35
Calculating 64 - 30
Sub result: 64 - 30 = 34
Calculating 38 + 71
Add result: 38 + 71 = 109
Calculating 51 - 73
Sub result: 51 - 73 = -22
Calculating 29 + 12
Add result: 29 + 12 = 41

4、注意内容

4.1 因为引入了配置文件，需要使用google的配置文件类protobuf-java-2.5.0.jar

4.2 打包运行

      我是eclipse环境中调试后，放centos执行的，一开始把代码和依赖库打包在一起，执行会报错。最后是将依赖库单独在centos上建一个lib，只打包代码部分，这样执行才没有问题。

    

<span style="font-family:Microsoft YaHei;font-size:14px;">[root@archive akka]# Exception in thread "main" com.typesafe.config.ConfigException$Missing: No configuration setting found for key 'akka.version'
        at com.typesafe.config.impl.SimpleConfig.findKey(SimpleConfig.java:124)
        at com.typesafe.config.impl.SimpleConfig.find(SimpleConfig.java:145)
</span>

    或者是这样

   

<span style="font-family:Microsoft YaHei;font-size:14px;">Java HotSpot(TM) 64-Bit Server VM (build 24.80-b11, mixed mode)
[root@archive akka]# Exception in thread "main" java.lang.NoClassDefFoundError: scala/concurrent/ExecutionContext
        at java.lang.Class.getDeclaredMethods0(Native Method)
        at java.lang.Class.privateGetDeclaredMethods(Class.java:2625)
        at java.lang.Class.getMethod0(Class.java:2866)
        at java.lang.Class.getMethod(Class.java:1676)
</span>

     最后通过只打包自己的代码， lib库单独放置的方式解决