RPC框架 之一 最简RPC

最近两月计划学习研究下RPC框架。本学习会以Dubbo和Motan为参考,先从RPC原理和一个简单的例子入手。

一、 RPC原理

1. 服务消费方本地调用服务提供方的例子

package com.medici.lorenzo.rpc.stub;

/**
 * @author Weimin Sun
 *
 */


public interface HelloService {

    String hello(String name);

}
package com.medici.lorenzo.rpc.stub;

/**
 * @author Weimin Sun
 *
 */
public class HelloServiceImpl implements HelloService {

    /* (non-Javadoc)
     * @see com.medici.lorenzo.easy.HelloService#hello(java.lang.String)
     */
    public String hello(String name) {
        return "Hello " + name;
    }

}
package com.medici.lorenzo.rpc.stub;

import com.medici.lorenzo.rpc.easy.HelloService;
import com.medici.lorenzo.rpc.easy.HelloServiceImpl;

/**
 * @author Weimin Sun
 *
 */
public class LocalInvoke {

    /**
     * @param args
     */
    public static void main(String[] args) {
        HelloService helloService = new HelloServiceImpl();
                helloService.hello("Hello World!");
    }

}

2. 调用远程服务

如果服务部署在不同机器,服务间的调用就要网络通信过程,服务消费方每调用一个服务都要写网络通信相关代码,不仅复杂而且极易出错。那么有没有一种方式能像调用本地服务一样调用远程服务,而让调用者对网络通信这些细节透明,比如服务消费方在执行helloService.hello(“Hello World!”)时,实质上调用的是远端的服务。
答案就是RPC,看一下其调用流程:

image.png
  • 服务消费方(client)调用以本地调用方式调用服务;
  • client stub接收到调用后负责将方法、参数等组装成能够进行网络传输的消息体;
  • client stub找到服务地址,并将消息发送到服务端;
  • server stub收到消息后进行解码;
  • server stub根据解码结果调用本地的服务;
  • 本地服务执行并将结果返回给server stub;
  • server stub将返回结果打包成消息并发送至消费方;
  • client stub接收到消息,并进行解码;
  • 服务消费方得到结果。
    下面把上面的本地调用改造一下,可以用来远程调用:
package com.medici.lorenzo.rpc.stub;

import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
import java.net.Socket;

/**
 * @author Weimin Sun
 *
 */
public class RpcProxyClient implements java.lang.reflect.InvocationHandler{
    
    public RpcProxyClient(){
        
    }
    /**
     * 得到被代理对象;
     */
    @SuppressWarnings("unchecked")
    public static <T> T getProxy(final Class<T> interfaceClass){
        return (T) Proxy.newProxyInstance(interfaceClass.getClassLoader(),
                new Class<?>[] {interfaceClass}, new RpcProxyClient());
    }
 
    /**
     * 调用此方法执行
     */
    @Override
    public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
        int port = 3456;
        Socket socket = new Socket("127.0.0.1", port);
        try {
            ObjectOutputStream output = new ObjectOutputStream(socket.getOutputStream());
            try {
                output.writeUTF(method.getName());
                output.writeObject(method.getParameterTypes());
                output.writeObject(args);
                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();
        }
    }
      
}
/**
 * 
 */
package com.medici.lorenzo.rpc.stub;

import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.lang.reflect.Method;
import java.net.ServerSocket;
import java.net.Socket;

import com.medici.lorenzo.rpc.easy.HelloService;
import com.medici.lorenzo.rpc.easy.HelloServiceImpl;

/**
 * @author Weimin Sun
 *
 */
public class RemoteServiceStub {

    /**
     * @param args
     */
    public static void main(String[] args) {
        int port = 3456;
        ServerSocket server;
        try {
            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 {
                                         HelloService service = new HelloServiceImpl();
                                        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();
                
                Thread.sleep(2000);
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
        
        } catch (IOException e1) {
            // TODO Auto-generated catch block
            e1.printStackTrace();
        }

    }

}

/**
 * 
 */
package com.medici.lorenzo.rpc.stub;

import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.lang.reflect.Method;
import java.net.ServerSocket;
import java.net.Socket;

import com.medici.lorenzo.rpc.easy.HelloService;

/**
 * @author Weimin Sun
 *
 */
public class RemoteInvoke {

    /**
     * @param args
     * @throws InterruptedException 
     */
    public static void main(String[] args) throws InterruptedException {
        
        HelloService helloService = (HelloService)RpcProxyClient.getProxy(HelloService.class);
        for (int i = 0; i < Integer.MAX_VALUE; i ++) {
            String hello = helloService.hello("Hello World" + i);
            System.out.println(hello);
            Thread.sleep(1000);
        }
        

    }

}

这些代码已实现了简单的远程调用服务的功能,下面再把编码和解码,通讯代码放在一起,就是下面的实现。

二、 简单RPC

1 核心框架

package com.medici.lorenzo.rpc.easy;

/**
 * @author Weimin Sun
 *
 */
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;


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();
                }
            }
        });
    }

}

2 定义服务接口

package com.medici.lorenzo.rpc.easy;

/**
 * @author Weimin Sun
 *
 */


public interface HelloService {

    String hello(String name);

}

3 实现服务

package com.medici.lorenzo.rpc.easy;

/**
 * @author Weimin Sun
 *
 */
public class HelloServiceImpl implements HelloService {

    /* (non-Javadoc)
     * @see com.medici.lorenzo.easy.HelloService#hello(java.lang.String)
     */
    public String hello(String name) {
        return "Hello " + name;
    }

}

4 暴露服务

package com.medici.lorenzo.rpc.easy;

/**
 * @author Weimin Sun
 *
 */
public class RpcProvider {

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

}

5 引用服务

package com.medici.lorenzo.rpc.easy;

/**
 * @author Weimin Sun
 *
 */
public class RpcConsumer {

    /**
     * @param args
     */
    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);
        }
    }
}

本例的思路:

  1. 使用阻塞的socket IO流来进行server(rpc应用中服务提供方)和client(服务消费方)的通信。
  2. 并且是端对端的,用端口号来直接进行通信。
  3. 方法的远程调用使用的是jdk的动态代理
  4. 参数的序列化也是使用的最简单的objectStream。

如果是rpc框架会对上面的实现方式进行替换升级,采用可用易扩展,更适宜分布式场景的中间件技术来替换。

  1. 用netty的nio特性达到非阻塞的通信,
  2. 使用zookeeper或其它产品统一管理服务注册与发现,解决了端对端不灵活的劣势。
  3. 代理方式有cglib字节码技术。
  4. 序列化方式有hession2,fastjson等。
  5. rpc框架要解决的不仅仅是技术层面的问题,还要考虑重试机制,超时配置,性能统计等…

代码:最简RPC例子

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