【RPC 专栏】简单了解RPC实现原理

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时下很多企业应用更新换代到分布式,一篇文章了解什么是RPC。
原作者梁飞,在此记录下他非常简洁的rpc实现思路。

核心框架类

/*
* Copyright 2011 Alibaba.com All right reserved. This software is the
* confidential and proprietary information of Alibaba.com ("Confidential
* Information"). You shall not disclose such Confidential Information and shall
* use it only in accordance with the terms of the license agreement you entered
* into with Alibaba.com.
*/

package com.alibaba.study.rpc.framework;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
import java.net.ServerSocket;
import java.net.Socket;
/**
* RpcFramework
*
* @author william.liangf
*/

public class RpcFramework {
   /**
    * 暴露服务
    *
    * @param service 服务实现
    * @param port 服务端口
    * @throws Exception
    */

   public static void export(final Object service, int port) throws Exception {
       if (service == null)
           throw new IllegalArgumentException("service instance == null");
       if (port <= 0 || port > 65535)
           throw new IllegalArgumentException("Invalid port " + port);
       System.out.println("Export service " + service.getClass().getName() + " on port " + port);
       ServerSocket server = new ServerSocket(port);
       for(;;) {
           try {
               final Socket socket = server.accept();
               new Thread(new Runnable() {
                   @Override
                   public void run() {
                       try {
                           try {
                               ObjectInputStream input = new ObjectInputStream(socket.getInputStream());
                               try {
                                   String methodName = input.readUTF();
                                   Class<?>[] parameterTypes = (Class<?>[])input.readObject();
                                   Object[] arguments = (Object[])input.readObject();
                                   ObjectOutputStream output = new ObjectOutputStream(socket.getOutputStream());
                                   try {
                                       Method method = service.getClass().getMethod(methodName, parameterTypes);
                                       Object result = method.invoke(service, arguments);
                                       output.writeObject(result);
                                   } catch (Throwable t) {
                                       output.writeObject(t);
                                   } finally {
                                       output.close();
                                   }
                               } finally {
                                   input.close();
                               }
                           } finally {
                               socket.close();
                           }
                       } catch (Exception e) {
                           e.printStackTrace();
                       }
                   }
               }).start();
           } catch (Exception e) {
               e.printStackTrace();
           }
       }
   }
   /**
    * 引用服务
    *
    * @param <T> 接口泛型
    * @param interfaceClass 接口类型
    * @param host 服务器主机名
    * @param port 服务器端口
    * @return 远程服务
    * @throws Exception
    */

   @SuppressWarnings("unchecked")
   public static <T> T refer(final Class<T> interfaceClass, final String host, final int port) throws Exception {
       if (interfaceClass == null)
           throw new IllegalArgumentException("Interface class == null");
       if (! interfaceClass.isInterface())
           throw new IllegalArgumentException("The " + interfaceClass.getName() + " must be interface class!");
       if (host == null || host.length() == 0)
           throw new IllegalArgumentException("Host == null!");
       if (port <= 0 || port > 65535)
           throw new IllegalArgumentException("Invalid port " + port);
       System.out.println("Get remote service " + interfaceClass.getName() + " from server " + host + ":" + port);
       return (T) Proxy.newProxyInstance(interfaceClass.getClassLoader(), new Class<?>[] {interfaceClass}, new InvocationHandler() {
           public Object invoke(Object proxy, Method method, Object[] arguments) throws Throwable {
               Socket socket = new Socket(host, port);
               try {
                   ObjectOutputStream output = new ObjectOutputStream(socket.getOutputStream());
                   try {
                       output.writeUTF(method.getName());
                       output.writeObject(method.getParameterTypes());
                       output.writeObject(arguments);
                       ObjectInputStream input = new ObjectInputStream(socket.getInputStream());
                       try {
                           Object result = input.readObject();
                           if (result instanceof Throwable) {
                               throw (Throwable) result;
                           }
                           return result;
                       } finally {
                           input.close();
                       }
                   } finally {
                       output.close();
                   }
               } finally {
                   socket.close();
               }
           }
       });
   }
}

定义服务接口

/*
* Copyright 2011 Alibaba.com All right reserved. This software is the
* confidential and proprietary information of Alibaba.com ("Confidential
* Information"). You shall not disclose such Confidential Information and shall
* use it only in accordance with the terms of the license agreement you entered
* into with Alibaba.com.
*/

package com.alibaba.study.rpc.test;
/**
* HelloService
*
* @author william.liangf
*/

public interface HelloService {
   String hello(String name);
}

实现服务

/*
* Copyright 2011 Alibaba.com All right reserved. This software is the
* confidential and proprietary information of Alibaba.com ("Confidential
* Information"). You shall not disclose such Confidential Information and shall
* use it only in accordance with the terms of the license agreement you entered
* into with Alibaba.com.
*/

package com.alibaba.study.rpc.test;
/**
* HelloServiceImpl
*
* @author william.liangf
*/

public class HelloServiceImpl implements HelloService {
   public String hello(String name) {
       return "Hello " + name;
   }
}

暴露服务

/*
* Copyright 2011 Alibaba.com All right reserved. This software is the
* confidential and proprietary information of Alibaba.com ("Confidential
* Information"). You shall not disclose such Confidential Information and shall
* use it only in accordance with the terms of the license agreement you entered
* into with Alibaba.com.
*/

package com.alibaba.study.rpc.test;
import com.alibaba.study.rpc.framework.RpcFramework;
/**
* RpcProvider
*
* @author william.liangf
*/

public class RpcProvider {
   public static void main(String[] args) throws Exception {
       HelloService service = new HelloServiceImpl();
       RpcFramework.export(service, 1234);
   }
}

引用服务

/*
* Copyright 2011 Alibaba.com All right reserved. This software is the
* confidential and proprietary information of Alibaba.com ("Confidential
* Information"). You shall not disclose such Confidential Information and shall
* use it only in accordance with the terms of the license agreement you entered
* into with Alibaba.com.
*/

package com.alibaba.study.rpc.test;
import com.alibaba.study.rpc.framework.RpcFramework;
/**
* RpcConsumer
*
* @author william.liangf
*/

public class RpcConsumer {
   public static void main(String[] args) throws Exception {
       HelloService service = RpcFramework.refer(HelloService.class, "127.0.0.1", 1234);
       for (int i = 0; i < Integer.MAX_VALUE; i ++) {
           String hello = service.hello("World" + i);
           System.out.println(hello);
           Thread.sleep(1000);
       }
   }
}

总结

这个简单的例子的实现思路是使用阻塞的socket IO流来进行server和client的通信,也就是rpc应用中服务提供方和服务消费方。并且是端对端的,用端口号来直接进行通信。方法的远程调用使用的是jdk的动态代理,参数的序列化也是使用的最简单的objectStream。

真实的rpc框架会对上面的实现方式进行替换,采用更快更稳定,更高可用易扩展,更适宜分布式场景的中间件,技术来替换。例如使用netty的nio特性达到非阻塞的通信,使用zookeeper统一管理服务注册与发现,解决了端对端不灵活的劣势。代理方式有cglib字节码技术。序列化方式有hession2,fastjson等等。不过梁飞大大的博客使用原生的jdk api就展现给各位读者一个生动形象的rpc demo,实在是强。rpc框架解决的不仅仅是技术层面的实现,还考虑到了rpc调用中的诸多问题,重试机制,超时配置…这些就需要去了解成熟的rpc框架是如果考虑这些问题的了。

推荐一个轻量级的rpc框架:motan。weibo团队在github开源的一个rpc框架,有相应的文档,用起来感觉比dubbo要轻量级,易上手。



【RPC 专栏】简单了解RPC实现原理

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