1.Channel

Channel中有EventLoop和ChannelPipeline,

public interface Channel {

    /**
     * Return the {@link EventLoop} this {@link Channel} was registered to.
     */
    EventLoop eventLoop();
}

1.1 Channel和EventLoop

在bind时会去做register动作,这个之前分析过
参考:Netty笔记-Channel的Register

此时也将EventLoop与Channel关联起来,Channel有了EventLoop便有了异步操作的能力,Channel的很多操作都是异步的,都是EventLoop的功劳
参考:Netty笔记-GlobalEventExecutor

        @Override
        public final void register(EventLoop eventLoop, final ChannelPromise promise) {
            if (eventLoop == null) {
                throw new NullPointerException("eventLoop");
            }
            if (isRegistered()) {
                promise.setFailure(new IllegalStateException("registered to an event loop already"));
                return;
            }
            if (!isCompatible(eventLoop)) {
                promise.setFailure(
                        new IllegalStateException("incompatible event loop type: " + eventLoop.getClass().getName()));
                return;
            }

            AbstractChannel.this.eventLoop = eventLoop;

            if (eventLoop.inEventLoop()) {
                register0(promise);
            } else {
                try {
                    eventLoop.execute(new Runnable() {
                        @Override
                        public void run() {
                            register0(promise);
                        }
                    });
                } catch (Throwable t) {
                    logger.warn(
                            "Force-closing a channel whose registration task was not accepted by an event loop: {}",
                            AbstractChannel.this, t);
                    closeForcibly();
                    closeFuture.setClosed();
                    safeSetFailure(promise, t);
                }
            }
        }

1 .2 使用EventLoop进行异步操作

我们会发现在代码中大量出现如下模式的代码

if (eventLoop.inEventLoop()) {
                
            } else {
                try {
                    eventLoop.execute(new Runnable() {
                        @Override
                        public void run() {
                        }
                    });
                }
}

所以上面的register0(promise)这段代码是异步执行的