基于Netty的RPC架构学习笔记（七）：netty学习之心跳

idleStateHandler

Netty提供的检测会话状态的工具。

netty3

Server.java

package com.heart;

import java.net.InetSocketAddress;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

import org.jboss.netty.bootstrap.ServerBootstrap;
import org.jboss.netty.channel.ChannelPipeline;
import org.jboss.netty.channel.ChannelPipelineFactory;
import org.jboss.netty.channel.Channels;
import org.jboss.netty.channel.socket.nio.NioServerSocketChannelFactory;
import org.jboss.netty.handler.codec.string.StringDecoder;
import org.jboss.netty.handler.codec.string.StringEncoder;
import org.jboss.netty.handler.timeout.IdleStateHandler;
import org.jboss.netty.util.HashedWheelTimer;
/**
 * 
 */
public class Server {

	public static void main(String[] args) {

		//服务类
		ServerBootstrap bootstrap = new ServerBootstrap();
		
		//boss线程监听端口，worker线程负责数据读写
		ExecutorService boss = Executors.newCachedThreadPool();
		ExecutorService worker = Executors.newCachedThreadPool();
		
	//设置niosocket工厂
		bootstrap.setFactory(new NioServerSocketChannelFactory(boss, worker));
		//new一个定时器
		final HashedWheelTimer hashedWheelTimer = new HashedWheelTimer();
		//设置管道的工厂
		bootstrap.setPipelineFactory(new ChannelPipelineFactory() {
			
			@Override
			public ChannelPipeline getPipeline() throws Exception {

				ChannelPipeline pipeline = Channels.pipeline();
				//需要在这里添加一个处理，handler才能处理
				//IdleStateHandler参数，定时器（在上面定义了，需要new出来），读超时时间，写超时时间，读写超时时间。
				pipeline.addLast("idle", new IdleStateHandler(hashedWheelTimer, 5, 5, 10));
				pipeline.addLast("decoder", new StringDecoder());
				pipeline.addLast("encoder", new StringEncoder());
				pipeline.addLast("helloHandler", new HelloHandler());
				return pipeline;
			}
		});
		
		bootstrap.bind(new InetSocketAddress(10101));
		
		System.out.println("start!!!");
		
	}

}

HelloHanler.java

package com.heart;

import org.jboss.netty.channel.ChannelEvent;
import org.jboss.netty.channel.ChannelFuture;
import org.jboss.netty.channel.ChannelFutureListener;
import org.jboss.netty.channel.ChannelHandlerContext;
import org.jboss.netty.channel.MessageEvent;
import org.jboss.netty.channel.SimpleChannelHandler;
import org.jboss.netty.handler.timeout.IdleState;
import org.jboss.netty.handler.timeout.IdleStateEvent;

public class HelloHandler extends SimpleChannelHandler {

	@Override
	public void messageReceived(ChannelHandlerContext ctx, MessageEvent e) throws Exception {
	
		System.out.println(e.getMessage());
	}

	@Override
	public void handleUpstream(final ChannelHandlerContext ctx, ChannelEvent e) throws Exception {
		if (e instanceof IdleStateEvent) {
		//e.getState返回状态，如果太久没有读，就会返回read，如果太久没有写就会返回write，没有度也没有写返回ALL_IDE
			if(((IdleStateEvent)e).getState() == IdleState.ALL_IDLE){
				System.out.println("提示玩家下线");
				//关闭会话，踢玩家下线
				//回写给用户，提示会话将会关闭。
				ChannelFuture write = ctx.getChannel().write("time out, you will close");
				write.addListener(new ChannelFutureListener() {
					
					@Override
					public void operationComplete(ChannelFuture future) throws Exception {
						 ctx.getChannel().close();
					}
				});
			}
		} else {
			super.handleUpstream(ctx, e);
		}
	}

}

等10秒不读也不写就会自动关闭

netty5

Server.java

package com.heart;

import io.netty.bootstrap.ServerBootstrap;
import io.netty.channel.Channel;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.ChannelOption;
import io.netty.channel.EventLoopGroup;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.nio.NioServerSocketChannel;
import io.netty.handler.codec.string.StringDecoder;
import io.netty.handler.codec.string.StringEncoder;
import io.netty.handler.timeout.IdleStateHandler;

/**
 * netty5服务端
 * @au
 *
 */
public class Server {

	public static void main(String[] args) {
		//服务类
		ServerBootstrap bootstrap = new ServerBootstrap();
		
		//boss和worker
		EventLoopGroup boss = new NioEventLoopGroup();
		EventLoopGroup worker = new NioEventLoopGroup();
		
		try {
			//设置线程池
			bootstrap.group(boss, worker);
			
			//设置socket工厂、
			bootstrap.channel(NioServerSocketChannel.class);
			
			//设置管道工厂
			bootstrap.childHandler(new ChannelInitializer<Channel>() {

				@Override
				protected void initChannel(Channel ch) throws Exception {
					ch.pipeline().addLast(new IdleStateHandler(5, 5, 10));
					ch.pipeline().addLast(new StringDecoder());
					ch.pipeline().addLast(new StringEncoder());
					ch.pipeline().addLast(new ServerHandler());
				}
			});
			
			//netty3中对应设置如下
			//bootstrap.setOption("backlog", 1024);
			//bootstrap.setOption("tcpNoDelay", true);
			//bootstrap.setOption("keepAlive", true);
			//设置参数，TCP参数
			bootstrap.option(ChannelOption.SO_BACKLOG, 2048);//serverSocketchannel的设置，链接缓冲池的大小
			bootstrap.childOption(ChannelOption.SO_KEEPALIVE, true);//socketchannel的设置,维持链接的活跃，清除死链接
			bootstrap.childOption(ChannelOption.TCP_NODELAY, true);//socketchannel的设置,关闭延迟发送
			
			//绑定端口
			ChannelFuture future = bootstrap.bind(10101);
			
			System.out.println("start");
			
			//等待服务端关闭
			future.channel().closeFuture().sync();
			
		} catch (Exception e) {
			e.printStackTrace();
		} finally{
			//释放资源
			boss.shutdownGracefully();
			worker.shutdownGracefully();
		}
	}
}

ServerHandler.java

package com.heart;

import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelFutureListener;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.SimpleChannelInboundHandler;
import io.netty.handler.timeout.IdleState;
import io.netty.handler.timeout.IdleStateEvent;
/**
 * 服务端消息处理
 * @
 *
 */
public class ServerHandler extends SimpleChannelInboundHandler<String> {

	@Override
	protected void messageReceived(ChannelHandlerContext ctx, String msg) throws Exception {

		System.out.println(msg);
		
		ctx.channel().writeAndFlush("hi");
		ctx.writeAndFlush("hi");
	}
	
	

	@Override
	public void userEventTriggered(final ChannelHandlerContext ctx, Object evt) throws Exception {
		if(evt instanceof IdleStateEvent){
			IdleStateEvent event = (IdleStateEvent)evt;
			if(event.state() == IdleState.ALL_IDLE){
				
				//清除超时会话
				ChannelFuture writeAndFlush = ctx.writeAndFlush("you will close");
				writeAndFlush.addListener(new ChannelFutureListener() {
					
					@Override
					public void operationComplete(ChannelFuture future) throws Exception {
						ctx.channel().close();
					}
				});
			}
		}else{
			super.userEventTriggered(ctx, evt);
		}
	}


	/**
	 * 新客户端接入
	 */
	@Override
	public void channelActive(ChannelHandlerContext ctx) throws Exception {
		System.out.println("channelActive");
	}

	/**
	 * 客户端断开
	 */
	@Override
	public void channelInactive(ChannelHandlerContext ctx) throws Exception {
		System.out.println("channelInactive");
	}

	/**
	 * 异常
	 */
	@Override
	public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
		cause.printStackTrace();
	}
	
	
}

总结

1. 心跳其实就是一个普通的请求，特点数据简单，业务也简单

2. 心跳对于服务端来说，定时清除闲置会话inactive(netty5) channelclose(netty3)

假如客户端突然停电了，这个时候会话保存着，然后有电了之后，再次请求会重新建立会话，原来的会话就成了僵尸会话，需要定时去清理这些僵尸会话。后台还可以返回系统时间，达到一个防作弊的效果，前端修改系统时间可以达到一个游戏加速的作用。

3. 心跳对客户端来说，用来检测会话是否断开，是否重连！ 用来检测网络延时！

手机app中经常有断开连接、重新连接的操作。玩王者的时候右上角有一个网络延迟，就是心跳做的。