Channel Register

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io.netty.channel.AbstractChannel.AbstractUnsafe#register

开始注册

   if (eventLoop.inEventLoop()) {
                register0(promise);
            } else {
                try {
                    eventLoop.execute(new Runnable() {
                        @Override
                        public void run() {
                            register0(promise);
                        }
                    });
                } catch (Throwable t) {
                }
            }

进入 io.netty.util.concurrent.SingleThreadEventExecutor#execute，SingleThreadEventExecutor重写线程池的execute方法

1. 添加register0到任务队列
2. 会调用线程start

inEventLoop()方法用来判断当前是否在EventLoop线程执行，注册的时候是在main线程执行的，所以为false。

eventLoop.execute

    @Override
    public void execute(Runnable task) {
        if (task == null) {
            throw new NullPointerException("task");
        }

        boolean inEventLoop = inEventLoop();
        if (inEventLoop) {
            addTask(task);
        } else {
            startThread();
            addTask(task);
            if (isShutdown() && removeTask(task)) {
                reject();
            }
        }

        if (!addTaskWakesUp && wakesUpForTask(task)) {
            wakeup(inEventLoop);
        }
    }

register0

断点 io.netty.channel.AbstractChannel.AbstractUnsafe#register0
SingleThreadEventExecutor的Thread运行的是NioEventLoop的run。

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  doRegister();
pipeline.invokeHandlerAddedIfNeeded();
 pipeline.fireChannelRegistered();

doRegister 会绑定channel到selector

invokeHandlerAddedIfNeeded

断点 ServerBootstrap 181
断点 SimpleServerHandler#handlerAdded
断点 ServerBootstrap 193

 p.addLast(new ChannelInitializer<Channel>() {
            @Override
            public void initChannel(Channel ch) throws Exception {
                final ChannelPipeline pipeline = ch.pipeline();
                ChannelHandler handler = handler();
                if (handler != null) {
                    pipeline.addLast(handler);//断点
                }

                ch.eventLoop().execute(new Runnable() {
                    @Override
                    public void run() {
                        pipeline.addLast(new ServerBootstrapAcceptor(
                                currentChildGroup, currentChildHandler, currentChildOptions, currentChildAttrs));
                    }
                });
            }
        });

调用pipeline.addLast(handler);之前，pipeline中只有head ServerBootstrap$1#0 tail
调用之后，pipeline中有 head ServerBootstrap$1#0 SimpleServerHandler tail
函数返回后，进入
io.netty.channel.ChannelInitializer#initChannel(io.netty.channel.ChannelHandlerContext)

if (initMap.putIfAbsent(ctx, Boolean.TRUE) == null) { // Guard against re-entrance.
            try {
                initChannel((C) ctx.channel());
            } catch (Throwable cause) {
                // Explicitly call exceptionCaught(...) as we removed the handler before calling initChannel(...).
                // We do so to prevent multiple calls to initChannel(...).
                exceptionCaught(ctx, cause);
            } finally {
                remove(ctx);
            }
            return true;
        }

然后会把ServerBootstrap$1#0删除。

另外，对于pipeline添加ServerBootstrapAcceptor，会以任务方式提交到队列。

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fireChannelRegistered

SimpleServerHandler#channelRegistered