netty示例

maven依赖

    <dependency>
            <groupId>io.netty</groupId>
            <artifactId>netty-all</artifactId>
            <version>4.1.22.Final</version>
        </dependency>

echo服务器示例

public class EchoServer {
    
    private int port;
    
    public EchoServer(int port){
        this.port = port;
    }
    
    public void run() throws Exception{
        
        //bossGroup只负责接收客户端的连接，不做复杂操作，为了减少资源占用，取值越小越好
        EventLoopGroup bossGroup=new NioEventLoopGroup(1, new DefaultThreadFactory("netty-acceptor"));
        //workerGroup作为worker，处理boss接收的连接的流量和将接收的连接注册进入这个worker
        EventLoopGroup workerGroup=new NioEventLoopGroup(Math.max(1, Runtime.getRuntime().availableProcessors()-1), new DefaultThreadFactory("netty-worker"));
        //longBizGroup作为耗时业务处理器
        EventLoopGroup longBizGroup = new NioEventLoopGroup(100, new DefaultThreadFactory("netty-long-worker"));
        
        try {
            
            ServerBootstrap b=new ServerBootstrap();    //ServerBootstrap负责建立服务端
            b.group(bossGroup, workerGroup)
                .channel(NioServerSocketChannel.class)  //指定使用NioServerSocketChannel产生一个ServerChannel用来接收连接，会在使用bossGroup的EventLoop中执行
                .childHandler(new ChannelInitializer<SocketChannel>() {//ChannelInitializer用于配置一个新的Channel用来处理数据读写，以及业务操作等
                    public void initChannel(SocketChannel ch) throws Exception {
                        ChannelPipeline pipeline = ch.pipeline(); //处理器管道
                        pipeline.addLast(longBizGroup, new EchoServerHandler()); //配置自定义的处理器，并在指定的longBizGroup的EventLoop中执行
                    };
                })
                .option(ChannelOption.SO_BACKLOG, 128)
                .childOption(ChannelOption.SO_KEEPALIVE, true);
            
            ChannelFuture f=b.bind(port).sync();
            f.channel().closeFuture().sync();
            
        }finally{
            bossGroup.shutdownGracefully(); //资源优雅释放
            workerGroup.shutdownGracefully();
        }
    }
    
    
    public static class EchoServerHandler extends ChannelInboundHandlerAdapter {
        
        @Override
        public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
            
            TimeUnit.MILLISECONDS.sleep(50); //模拟耗时任务
            ctx.write(msg); //调用write方法来逐字返回接收到的信息
            ctx.flush();    //只调用write是不会释放的，它会缓存，直到调用flush
            //ctx.writeAndFlush(msg); //可以直接使用writeAndFlush(msg)
        }
        
        @Override
        public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
            cause.printStackTrace();
            ctx.close();
        }
    }
    
    public static void main(String[] args) {
        int port=8088;
        try {
            new EchoServer(port).run();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

echo服务器测试

telnet localhost 8088

hello
hello

IO模型

IO模型列表.png

BIO模型

BIO模型.png

伪异步IO

伪异步IO.png

NIO模型

NIO模型.png

基于NIO模型，可以演变出以下四种reactor模型：

一、Reactor单线程模型: Reactor线程负责Accept新连接，网络IO，并分派请求到处理器中执行。

image.png

对应的netty配置

EventLoopGroup reactorGroup = new NioEventLoopGroup(1);
serverBootstrap.group(reactorGroup,reactorGroup);

二、Reactor单线程+线程池模型: Reactor线程负责Accept新连接，网络IO；线程池负责处理器执行。

image.png

对应的netty配置

EventLoopGroup reactorGroup = new NioEventLoopGroup(1);
serverBootstrap.group(reactorGroup,reactorGroup);

EventLoopGroup bizGroup = new NioEventLoopGroup(100);
pipeline.addLast(bizGroup, new XxxChannelHandler());

三、主从Reactor模型：主Reactor线程负责Accept新连接，从Reactor负责网络IO和处理器执行。

image.png

对应的netty配置

EventLoopGroup acceptorGroup = new NioEventLoopGroup(1);
EventLoopGroup ioGroup = new NioEventLoopGroup(Runtime.getRuntime().availableProcessors());
serverBootstrap.group(acceptorGroup,ioGroup);

四、主从Reactor+ 线程池模型: 主Reactor线程负责Accept新连接，从Reactor负责网络IO，线程池负责处理器执行。

image.png

对应的netty配置

EventLoopGroup acceptorGroup = new NioEventLoopGroup(1);
EventLoopGroup ioGroup = new NioEventLoopGroup(Runtime.getRuntime().availableProcessors());
serverBootstrap.group(acceptorGroup,ioGroup);

EventLoopGroup bizGroup = new NioEventLoopGroup(100);
pipeline.addLast(bizGroup, new XxxChannelHandler());