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Hadoop2源码分析－RPC探索实战详解大数据

• 大数据

1.概述

　　在《Hadoop2源码分析－RPC机制初识》博客中，我们对RPC机制有了初步的认识和了解，下面我们对Hadoop V2的RPC机制做进一步探索，在研究Hadoop V2的RPC机制，我们需要掌握相关的Java基础知识，如：Java NIO、动态代理与反射等。本篇博客介绍的内容目录如下所示：

  • Java NIO简述
  • Java NIO实例演示
  • 动态代理与反射简述
  • 动态代理与反射实例演示
  • Hadoop V2 RPC框架使用实例

　　下面开始今天的博客介绍。

2.Java NIO简述

　　Java NIO又称Java New IO，它替代了Java IO API，提供了与标准IO不同的IO工作方式。Java NIO由一下核心组件组成：

  • Channels：连接通道，即能从通道读取数据，又能写数据到通道。可以异步读写，读写从Buffer开始。
  • Buffers：消息缓冲区，用于和NIO通道进行交互。所谓缓冲区，它是一块可以读写的内存，该内存被封装成NIO的Buffer对象，并提供相应的方法，以便于访问。
  • Selectors：通道管理器，它能检测到Java NIO中多个通道，单独的线程可以管理多个通道，间接的管理多个网络连接。

　　下图为Java NIO的工作原理图，如下图所示：

Hadoop2源码分析－RPC探索实战详解大数据

3.Java NIO实例演示

  • NIOServer

　　首先，我们来看NIOServer的代码块。代码内容如下所示：

package cn.hadoop.nio; 
import java.io.IOException; 
import java.net.InetSocketAddress; 
import java.nio.ByteBuffer; 
import java.nio.channels.SelectionKey; 
import java.nio.channels.Selector; 
import java.nio.channels.ServerSocketChannel; 
import java.nio.channels.SocketChannel; 
import java.util.Iterator; 
import org.slf4j.Logger; 
import org.slf4j.LoggerFactory; 
import cn.hadoop.conf.ConfigureAPI; 
/** 
* @Date May 8, 2015 
* 
* @Author dengjie 
* 
* @Note Defined nio server 
*/ 
public class NIOServer { 
private static final Logger LOGGER = LoggerFactory.getLogger(NIOServer.class); 
// The channel manager 
private Selector selector; 
/** 
* Get ServerSocket channel and initialize 
*  
* 1.Get a ServerSocket channel 
*  
* 2.Set channel for non blocking 
*  
* 3.The channel corresponding to the ServerSocket binding to port port 
*  
* 4.Get a channel manager 
*  
* 5.The channel manager and the channel binding, and the channel registered 
* SelectionKey.OP_ACCEPT event 
*  
* @param port 
* @throws IOException 
*/ 
public void init(int port) throws IOException { 
ServerSocketChannel serverChannel = ServerSocketChannel.open(); 
serverChannel.configureBlocking(false); 
serverChannel.socket().bind(new InetSocketAddress(port)); 
this.selector = Selector.open(); 
serverChannel.register(selector, SelectionKey.OP_ACCEPT); 
} 
/** 
* listen selector 
*  
* @throws IOException 
*/ 
public void listen() throws IOException { 
LOGGER.info("Server has start success"); 
while (true) { 
selector.select(); 
Iterator<SelectionKey> ite = this.selector.selectedKeys().iterator(); 
while (ite.hasNext()) { 
SelectionKey key = (SelectionKey) ite.next(); 
ite.remove(); 
if (key.isAcceptable()) { 
ServerSocketChannel server = (ServerSocketChannel) key.channel(); 
SocketChannel channel = server.accept(); 
channel.configureBlocking(false);// 非阻塞 
channel.write(ByteBuffer.wrap(new String("Send test info to client").getBytes())); 
channel.register(this.selector, SelectionKey.OP_READ);// 设置读的权限 
} else if (key.isReadable()) { 
read(key); 
} 
} 
} 
} 
/** 
* Deal client send event 
*/ 
public void read(SelectionKey key) throws IOException { 
SocketChannel channel = (SocketChannel) key.channel(); 
ByteBuffer buffer = ByteBuffer.allocate(1024); 
channel.read(buffer); 
byte[] data = buffer.array(); 
String info = new String(data).trim(); 
LOGGER.info("Server receive info : " + info); 
ByteBuffer outBuffer = ByteBuffer.wrap(info.getBytes()); 
channel.write(outBuffer);// 将消息回送给客户端 
    } 
public static void main(String[] args) { 
try { 
NIOServer server = new NIOServer(); 
server.init(ConfigureAPI.ServerAddress.NIO_PORT); 
server.listen(); 
} catch (Exception ex) { 
ex.printStackTrace(); 
LOGGER.error("NIOServer main run error,info is " + ex.getMessage()); 
} 
} 
}
  • NIOClient

　　然后，我们在来看NIOClient的代码块，代码具体内容如下所示：

package cn.hadoop.nio; 
import java.io.IOException; 
import java.net.InetSocketAddress; 
import java.nio.ByteBuffer; 
import java.nio.channels.SelectionKey; 
import java.nio.channels.Selector; 
import java.nio.channels.SocketChannel; 
import java.util.Iterator; 
import org.slf4j.Logger; 
import org.slf4j.LoggerFactory; 
import cn.hadoop.conf.ConfigureAPI; 
/** 
* @Date May 8, 2015 
* 
* @Author dengjie 
* 
* @Note Defined NIO client 
*/ 
public class NIOClient { 
private static final Logger LOGGER = LoggerFactory.getLogger(NIOClient.class); 
private Selector selector; 
/** 
* Get ServerSocket channel and initialize 
*/ 
public void init(String ip, int port) throws Exception { 
SocketChannel channel = SocketChannel.open(); 
channel.configureBlocking(false); 
this.selector = Selector.open(); 
channel.connect(new InetSocketAddress(ip, port)); 
channel.register(selector, SelectionKey.OP_CONNECT); 
} 
/** 
* listen selector 
*/ 
public void listen() throws Exception { 
while (true) { 
selector.select(); 
Iterator<SelectionKey> ite = this.selector.selectedKeys().iterator(); 
while (ite.hasNext()) { 
SelectionKey key = (SelectionKey) ite.next(); 
ite.remove(); 
if (key.isConnectable()) { 
SocketChannel channel = (SocketChannel) key.channel(); 
if (channel.isConnectionPending()) { 
channel.finishConnect(); 
} 
channel.configureBlocking(false);// 非阻塞 
 
channel.write(ByteBuffer.wrap(new String("Send test info to server").getBytes())); 
channel.register(this.selector, SelectionKey.OP_READ); 
} else if (key.isReadable()) { 
read(key); 
} 
} 
} 
} 
/** 
* Deal client send event 
*/ 
public void read(SelectionKey key) throws IOException { 
SocketChannel channel = (SocketChannel) key.channel(); 
ByteBuffer buffer = ByteBuffer.allocate(1024); 
channel.read(buffer); 
byte[] data = buffer.array(); 
String info = new String(data).trim(); 
LOGGER.info("Client receive info : " + info); 
ByteBuffer outBuffer = ByteBuffer.wrap(info.getBytes()); 
channel.write(outBuffer); 
} 
public static void main(String[] args) { 
try { 
NIOClient client = new NIOClient(); 
client.init(ConfigureAPI.ServerAddress.NIO_IP, ConfigureAPI.ServerAddress.NIO_PORT); 
client.listen(); 
} catch (Exception ex) { 
ex.printStackTrace(); 
LOGGER.error("NIOClient main run has error,info is " + ex.getMessage()); 
} 
} 
}
  • ConfigureAPI

　　下面给出ConfigureAPI类的代码，内容如下所示：

package cn.hadoop.conf; 
/** 
* @Date May 7, 2015 
* 
* @Author dengjie 
* 
* @Note Defined rpc info 
*/ 
public class ConfigureAPI { 
public interface VersionID { 
public static final long RPC_VERSION = 7788L; 
} 
public interface ServerAddress { 
public static final int NIO_PORT = 8888; 
public static final String NIO_IP = "127.0.0.1"; 
} 
}

4.动态代理和反射简述

　　在Java中，动态代理主要用来做方法的增强，可以在不修改源码的情况下，增强一些方法。另外，还有一个作用就是做远程调用，比如现在有Java接口，该接口的实现部署在非本地服务器上，在编写客户端代码时，由于没法直接生成该对象，这个时候就需要考虑使用动态代理了。

　　而反射，利用了Class类作为反射实例化对象的基本应用，对于一个实例化对象而言，它需要调用类中的构造方法，属性和一般方法，这些操作都可以通过反射机制来完成。下面我们用一个实例来理解这些理论。

5.动态代理和反射实例演示

5.1动态代理

  • JProxy
package cn.java.base; 
import java.lang.reflect.InvocationHandler; 
import java.lang.reflect.Method; 
import java.lang.reflect.Proxy; 
/** 
* @Date May 7, 2015 
*  
* @Author dengjie 
*/ 
public class JProxy { 
public static void main(String[] args) { 
JInvocationHandler ji = new JInvocationHandler(); 
Subject sub = (Subject) ji.bind(new RealSubject()); 
System.out.println(sub.say("dengjie", 25)); 
} 
} 
interface Subject { 
public String say(String name, int age); 
} 
class RealSubject implements Subject { 
@Override 
public String say(String name, int age) { 
return name + "," + age; 
} 
} 
class JInvocationHandler implements InvocationHandler { 
private Object object = null; 
public Object bind(Object object) { 
this.object = object; 
return Proxy.newProxyInstance(object.getClass().getClassLoader(), object.getClass().getInterfaces(), this); 
} 
@Override 
public Object invoke(Object proxy, Method method, Object[] args) throws Throwable { 
Object tmp = method.invoke(this.object, args); 
return tmp; 
} 
}

5.2反射

  • JReflect
package cn.java.base; 
/** 
* @Date May 7, 2015 
*  
* @Author dengjie 
*/ 
public class JReflect { 
public static void main(String[] args) { 
Fruit f = Factory.getInstance(Orange.class.getName()); 
if (f != null) { 
f.eat(); 
} 
} 
} 
interface Fruit { 
public abstract void eat(); 
} 
class Apple implements Fruit { 
@Override 
public void eat() { 
System.out.println("apple"); 
} 
} 
class Orange implements Fruit { 
@Override 
public void eat() { 
System.out.println("orange"); 
} 
} 
class Factory { 
public static Fruit getInstance(String className) { 
Fruit f = null; 
try { 
f = (Fruit) Class.forName(className).newInstance(); 
} catch (Exception e) { 
e.printStackTrace(); 
} 
return f; 
} 
}

6.Hadoop V2 RPC框架使用实例

　　本实例主要演示通过Hadoop V2的RPC框架实现一个计算两个整数的Add和Sub，服务接口为 CaculateService ，继承于 VersionedProtocol ，具体代码如下所示：

  • CaculateService
package cn.hadoop.service; 
import org.apache.hadoop.io.IntWritable; 
import org.apache.hadoop.ipc.ProtocolInfo; 
import org.apache.hadoop.ipc.VersionedProtocol; 
import cn.hadoop.conf.ConfigureAPI; 
/** 
* @Date May 7, 2015 
* 
* @Author dengjie 
* 
* @Note Data calculate service interface 
*/ 
@ProtocolInfo(protocolName = "", protocolVersion = ConfigureAPI.VersionID.RPC_VERSION) 
public interface CaculateService extends VersionedProtocol { 
// defined add function 
public IntWritable add(IntWritable arg1, IntWritable arg2); 
// defined sub function 
public IntWritable sub(IntWritable arg1, IntWritable arg2); 
}

　　注意，本工程使用的是Hadoop-2.6.0版本，这里CaculateService接口需要加入注解，来声明版本号。

　　CaculateServiceImpl类实现CaculateService接口。代码如下所示：

  • CaculateServiceImpl
package cn.hadoop.service.impl; 
import java.io.IOException; 
import org.apache.hadoop.io.IntWritable; 
import org.apache.hadoop.ipc.ProtocolSignature; 
import cn.hadoop.conf.ConfigureAPI; 
import cn.hadoop.service.CaculateService; 
/** 
* @Date May 7, 2015 
* 
* @Author dengjie 
* 
* @Note Implements CaculateService class 
*/ 
public class CaculateServiceImpl implements CaculateService { 
public ProtocolSignature getProtocolSignature(String arg0, long arg1, int arg2) throws IOException { 
return this.getProtocolSignature(arg0, arg1, arg2); 
} 
/** 
* Check the corresponding version 
*/ 
public long getProtocolVersion(String arg0, long arg1) throws IOException { 
return ConfigureAPI.VersionID.RPC_VERSION; 
} 
/** 
* Add nums 
*/ 
public IntWritable add(IntWritable arg1, IntWritable arg2) { 
return new IntWritable(arg1.get() + arg2.get()); 
} 
/** 
* Sub nums 
*/ 
public IntWritable sub(IntWritable arg1, IntWritable arg2) { 
return new IntWritable(arg1.get() - arg2.get()); 
} 
}

　　CaculateServer服务类，对外提供服务，具体代码如下所示：

  • CaculateServer
package cn.hadoop.rpc; 
import org.apache.hadoop.conf.Configuration; 
import org.apache.hadoop.ipc.RPC; 
import org.apache.hadoop.ipc.RPC.Server; 
import org.slf4j.LoggerFactory; 
import org.slf4j.Logger; 
import cn.hadoop.service.CaculateService; 
import cn.hadoop.service.impl.CaculateServiceImpl; 
/** 
* @Date May 7, 2015 
* 
* @Author dengjie 
* 
* @Note Server Main 
*/ 
public class CaculateServer { 
private static final Logger LOGGER = LoggerFactory.getLogger(CaculateServer.class); 
public static final int IPC_PORT = 9090; 
public static void main(String[] args) { 
try { 
Server server = new RPC.Builder(new Configuration()).setProtocol(CaculateService.class) 
.setBindAddress("127.0.0.1").setPort(IPC_PORT).setInstance(new CaculateServiceImpl()).build(); 
server.start(); 
LOGGER.info("CaculateServer has started"); 
System.in.read(); 
} catch (Exception ex) { 
ex.printStackTrace(); 
LOGGER.error("CaculateServer server error,message is " + ex.getMessage()); 
} 
} 
}

　　注意，在Hadoop V2版本中，获取RPC下的Server对象不能在使用RPC.getServer()方法了，该方法已被移除，取而代之的是使用Builder方法来构建新的Server对象。

　　RPCClient客户端类，用于访问Server端，具体代码实现如下所示：

  • RPCClient
package cn.hadoop.rpc; 
import java.net.InetSocketAddress; 
import org.apache.hadoop.conf.Configuration; 
import org.apache.hadoop.io.IntWritable; 
import org.apache.hadoop.ipc.RPC; 
import org.slf4j.Logger; 
import org.slf4j.LoggerFactory; 
import cn.hadoop.service.CaculateService; 
/** 
* @Date May 7, 2015 
* 
* @Author dengjie 
* 
* @Note RPC Client Main 
*/ 
public class RPCClient { 
private static final Logger LOGGER = LoggerFactory.getLogger(RPCClient.class); 
public static void main(String[] args) { 
InetSocketAddress addr = new InetSocketAddress("127.0.0.1", CaculateServer.IPC_PORT); 
try { 
RPC.getProtocolVersion(CaculateService.class); 
CaculateService service = (CaculateService) RPC.getProxy(CaculateService.class, 
RPC.getProtocolVersion(CaculateService.class), addr, new Configuration()); 
int add = service.add(new IntWritable(2), new IntWritable(3)).get(); 
int sub = service.sub(new IntWritable(5), new IntWritable(2)).get(); 
LOGGER.info("2+3=" + add); 
LOGGER.info("5-2=" + sub); 
} catch (Exception ex) { 
ex.printStackTrace(); 
LOGGER.error("Client has error,info is " + ex.getMessage()); 
} 
} 
}

　　Hadoop V2 RPC服务端截图预览，如下所示：

Hadoop2源码分析－RPC探索实战详解大数据

　　Hadoop V2 RPC客户端截图预览，如下所示：

Hadoop2源码分析－RPC探索实战详解大数据

7.总结

　　Hadoop V2 RPC框架对Socket通信进行了封装，定义了自己的基类接口VersionProtocol。该框架需要通过网络以序列化的方式传输对象，关于Hadoop V2的序列化可以参考《Hadoop2源码分析－序列化篇》，传统序列化对象较大。框架内部实现了基于Hadoop自己的服务端对象和客户端对象。服务端对象通过new RPC.Builder().builder()的方式来获取，客户端对象通过RPC.getProxy()的方式来获取。并且都需要接受Configuration对象，该对象实现了Hadoop相关文件的配置。

8.结束语

　　这篇博客就和大家分享到这里，如果大家在研究学习的过程当中有什么问题，可以加群进行讨论或发送邮件给我，我会尽我所能为您解答，与君共勉！

原创文章，作者：745907710，如若转载，请注明出处：https://blog.ytso.com/228082.html

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