4.Netty源码-服务器启动

我们带着问题去看源码，下面是我的问题：

• serverSocketChannel是什么时候与selector绑定的，流程是什么
• 启动的线程数有多少，什么时候new的，什么时候start的
• 有那些地方需要用锁

前提概要：netty代码非常深，尽量写详细,贴出代码中可以看todo的注解。2.1章节为重点，提到了线程的创建与start
可以先看最后的总结再看。

服务端代码

主要是分析

• NioEventLoopGroup bossGroup = new NioEventLoopGroup();
• ChannelFuture cf = bootstrap.bind(6666).sync();

 public static void main(String[] args)  {
    //1.创建Boss NioEventLoopGroup , Worker NioEventLoopGroup
    NioEventLoopGroup bossGroup = new NioEventLoopGroup();
    NioEventLoopGroup workerGroup = new NioEventLoopGroup();
    try {
      //2.创建服务器端的启动对象，配置参数
      ServerBootstrap bootstrap = new ServerBootstrap();
      bootstrap.group(bossGroup, workerGroup)
          .channel(NioServerSocketChannel.class)
          //线程队列得到连接个数
          .option(ChannelOption.SO_BACKLOG, 128)
          //设置保持活动链接状态
          .childOption(ChannelOption.SO_KEEPALIVE, true)
          //给workGroup的EventLoop对应的管道设置handler
          .childHandler(new ChannelInitializer() {
            @Override
            protected void initChannel(SocketChannel socketChannel) throws Exception {
              socketChannel.pipeline().addLast(new NettyServerHandler());
            }
          });
      //3.绑定端口并且同步
      ChannelFuture cf = bootstrap.bind(6666).sync();

      //4.对关闭通道进行监听
      cf.channel().closeFuture().sync();
    } catch (InterruptedException e) {
      e.printStackTrace();
    }finally {
      bossGroup.shutdownGracefully();
      workerGroup.shutdownGracefully();
    }
  }

猜想

NioEventLoopGroup bossGroup = new NioEventLoopGroup();

• 创建NioEventLoop
• 创建Selector
  ChannelFuture cf = bootstrap.bind(6666).sync();
• 创建ServerSocketChannel
• 选出一个Selector于ServerSocketChannel绑定

实际

1.NioEventLoopGroup bossGroup = new NioEventLoopGroup();

protected MultithreadEventExecutorGroup(int nThreads, Executor executor,
                                            EventExecutorChooserFactory chooserFactory, Object... args) {
      // TODO: 不指定的时候，线程数默认cpu核数 *2
        if (nThreads <= 0) {
            throw new IllegalArgumentException(String.format("nThreads: %d (expected: > 0)", nThreads));
        }
     //TODO:executor.execute(Runnable command) 使用ThreadFactory创建一个新线程并且start();
        if (executor == null) {
            executor = new ThreadPerTaskExecutor(newDefaultThreadFactory());
        }

        children = new EventExecutor[nThreads];

        for (int i = 0; i < nThreads; i ++) {
            boolean success = false;
            try {
                // TODO: 创建NioEventLoop
                children[i] = newChild(executor, args);
                success = true;
            } catch (Exception e) {
                throw new IllegalStateException("failed to create a child event loop", e);
            } finally {
                if (!success) {
                    for (int j = 0; j < i; j ++) {
                        children[j].shutdownGracefully();
                    }

                    for (int j = 0; j < i; j ++) {
                        EventExecutor e = children[j];
                        try {
                            while (!e.isTerminated()) {
                                e.awaitTermination(Integer.MAX_VALUE, TimeUnit.SECONDS);
                            }
                        } catch (InterruptedException interrupted) {
                            // Let the caller handle the interruption.
                            Thread.currentThread().interrupt();
                            break;
                        }
                    }
                }
            }
        }
       // TODO: 根据nThreads线程数来选出选择选择器
        chooser = chooserFactory.newChooser(children);

        final FutureListener