前言:
此刻姐妹们对“netty运行原理”大概比较关心,各位老铁们都需要学习一些“netty运行原理”的相关知识。那么小编同时在网摘上收集了一些对于“netty运行原理””的相关知识,希望朋友们能喜欢,兄弟们快快来了解一下吧!Netty是一个高性能 事件驱动的异步的非堵塞的IO(NIO)框架,用于建立TCP等底层的连接,基于Netty可以建立高性能的Http服务器。支持HTTP、 WebSocket 、Protobuf、 Binary TCP |和UDP,Netty已经被很多高性能项目作为其Socket底层基础,如HornetQ Infinispan Vert.x
Play Framework Finangle和 Cassandra。其竞争对手是:Apache MINA和 Grizzly。
传统堵塞的IO读取如下:
InputStream is = new FileInputStream("input.bin");int byte = is.read();// 当前线程等待结果到达直至错误
而使用NIO如下:
while (true) { selector.select(); // 从多个通道请求事件 Iterator it = selector.selectedKeys().iterator(); while (it.hasNext()) { SelectorKey key = (SelectionKey) it.next(); handleKey(key); it.remove(); } }堵塞与非堵塞原理
传统硬件的堵塞如下,从内存中读取数据,然后写到磁盘,而CPU一直等到磁盘写完成,磁盘的写操作是慢的,这段时间CPU被堵塞不能发挥效率。
使用非堵塞的DMA如下图:CPU只是发出写操作这样的指令,做一些初始化工作,DMA具体执行,从内存中读取数据,然后写到磁盘,当完成写后发出一个中断事件给CPU。这段时间CPU是空闲的,可以做别的事情。这个原理称为Zero.copy零拷贝。
Netty底层基于上述Java NIO的零拷贝原理实现:
比较
Tomcat是一个Web服务器,它是采取一个请求一个线程,当有1000客户端时,会耗费很多内存。通常一个线程将花费 256kb到1mb的stack空间。
Node.js是一个线程服务于所有请求,在错误处理上有限制
Netty是一个线程服务于很多请求,如下图,当从Java NIO获得一个Selector事件,将激活通道Channel。
演示
Netty的使用代码如下:
Channel channel = ...ChannelFuture cf = channel.write(data);cf.addListener( new ChannelFutureListener() { @Override public void operationComplete(ChannelFuture future) throws Exception { if(!future.isSuccess() { future.cause().printStacktrace(); ... } ... }});...cf.sync();
通过引入观察者监听,当有数据时,将自动激活监听者中的代码运行。
我们使用Netty建立一个服务器代码:
public class EchoServer { private final int port; public EchoServer(int port) { this.port = port; } public void run() throws Exception { // Configure the server. EventLoopGroup bossGroup = new NioEventLoopGroup(); EventLoopGroup workerGroup = new NioEventLoopGroup(); try { ServerBootstrap b = new ServerBootstrap(); b.group(bossGroup, workerGroup).channel (NioServerSocketChannel.class) .option(ChannelOption.SO_BACKLOG, 100) .handler(new LoggingHandler(LogLevel.INFO)).childHandler(new ChannelInitializer<SocketChannel>() { @Override public void initChannel(SocketChannel ch) throws Exception { ch.pipeline().addLast( // new LoggingHandler(LogLevel.INFO), new EchoServerHandler()); } } ); // Start the server. ChannelFuture f = b.bind(port).sync(); // Wait until the server socket is closed. f.channel().closeFuture().sync(); } finally { // Shut down all event loops to terminate all threads. bossGroup.shutdownGracefully(); workerGroup.shutdownGracefully(); } }}
这段代码调用:在9999端口启动
new EchoServer(9999).run();
我们需要完成的代码是EchoServerHandler:
public class EchoServerHandler extends ChannelInboundHandlerAdapter { private static final Logger logger = Logger.getLogger(EchoServerHandler.class.getName()); @Override public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception { ctx.write(msg); } @Override public void channelReadComplete(ChannelHandlerContext ctx) throws Exception { ctx.flush(); } @Override public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) { // Close the connection when an exception is raised. logger.log(Level.WARNING, "Unexpected exception from downstream.", cause); ctx.close(); }}原理
一个Netty服务器的原理如下:
图中每次请求的读取是通过UpStream来实现,然后激活我们的服务逻辑如EchoServerHandler,而服务器向外写数据,也就是响应是通过DownStream实现的。每个通道Channel包含一对UpStream和DownStream,以及我们的handlers(EchoServerHandler),如下图,这些都是通过channel pipeline封装起来的,数据流在管道里流动,每个Socket对应一个ChannelPipeline。
CHANNELPIPELINE是关键,它类似Unix的管道,有以下作用:
为每个Channel 保留 ChannelHandlers ,如EchoServerHandler
所有的事件都要通过它
不断地修改:类似unix的SH管道: echo "Netty is shit...." | sed -e 's/is /is the /'
一个Channel对应一个 ChannelPipeline
包含协议编码解码 安全验证SSL/TLS和应用逻辑
客户端代码
前面我们演示了服务器端代码,下面是客户端代码:
public class EchoClient { private final String host; private final int port; private final int firstMessageSize; public EchoClient(String host, int port, int firstMessageSize) { this.host = host; this.port = port; this.firstMessageSize = firstMessageSize; } public void run() throws Exception { // Configure the client. EventLoopGroup group = new NioEventLoopGroup(); try { Bootstrap b = new Bootstrap(); b.group(group).channel(NioSocketChannel.class) .option(ChannelOption.TCP_NODELAY, true).handler(new ChannelInitializer<SocketChannel>() { @Override public void initChannel(SocketChannel ch) throws Exception { ch.pipeline().addLast( // new LoggingHandler(LogLevel.INFO), new EchoClientHandler(firstMessageSize)); } } ); // Start the client. ChannelFuture f = b.connect(host, port).sync(); // Wait until the connection is closed. f.channel().closeFuture().sync(); } finally { // Shut down the event loop to terminate all threads. group.shutdownGracefully(); } }}
客户端的应用逻辑EchoClientHandler:
public class EchoClientHandler extends ChannelInboundHandlerAdapter { private static final Logger logger = Logger.getLogger(EchoClientHandler.class.getName()); private final ByteBuf firstMessage; /** * Creates a client-side handler. */ public EchoClientHandler(int firstMessageSize) { if (firstMessageSize <= 0) { throw new IllegalArgumentException("firstMessageSize: " + firstMessageSize); } firstMessage = Unpooled.buffer(firstMessageSize); for (int i = 0; i < firstMessage.capacity(); i++) { firstMessage.writebyte((byte) i); } } @Override public void channelActive(ChannelHandlerContext ctx) { ctx.writeAndFlush(firstMessage); System.out.print("active"); } @Override public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception { ctx.write(msg); System.out.print("read"); } @Override public void channelReadComplete(ChannelHandlerContext ctx) throws Exception { ctx.flush(); System.out.print("readok"); } @Override public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) { // Close the connection when an exception is raised. logger.log(Level.WARNING, "Unexpected exception from downstream.", cause); ctx.close(); }}Java架构师丨苏先生:专注于Java开发技术的研究与知识分享!
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