Netty分布式NioSocketChannel注册到selector方法解析

public void read() {
    //必须是NioEventLoop方法调用的, 不能通过外部线程调用
    assert eventLoop().inEventLoop();
    //服务端channel的config
    final ChannelConfig config = config();
    //服务端channel的pipeline
    final ChannelPipeline pipeline = pipeline();
    //处理服务端接入的速率
    final RecvByteBufAllocator.Handle allocHandle = unsafe().recvBufAllocHandle();
    //设置配置
    allocHandle.reset(config);
    boolean closed = false;
    Throwable exception = null;
    try {
        try {
            do {
                //创建jdk底层的channel
                //readBuf用于临时承载读到链接
                int localRead = doReadMessages(readBuf);
                if (localRead == 0) {
                    break;
                }
                if (localRead < 0) {
                    closed = true;
                    break;
                }
                //分配器将读到的链接进行计数
                allocHandle.incMessagesRead(localRead);
                //连接数是否超过最大值
            } while (allocHandle.continueReading());
        } catch (Throwable t) {
            exception = t;
        }
        int size = readBuf.size();
        //遍历每一条客户端连接
        for (int i = 0; i < size; i ++) {
            readPending = false;
            //传递事件, 将创建NioSokectChannel进行传递
            //最终会调用ServerBootstrap的内部类ServerBootstrapAcceptor的channelRead()方法
            pipeline.fireChannelRead(readBuf.get(i));
        }
        readBuf.clear();
        allocHandle.readComplete();
        pipeline.fireChannelReadComplete();
        //代码省略
    } finally {
        //代码省略
    }
}

public void channelRead(ChannelHandlerContext ctx, Object msg) {
    final Channel child = (Channel) msg;
    //代码省略
    try {
        //work线程注册channel
        childGroup.register(child).addListener(new ChannelFutureListener() {
            @Override
            public void operationComplete(ChannelFuture future) throws Exception {
                if (!future.isSuccess()) {
                    forceClose(child, future.cause());
                }
            }
        });
    } catch (Throwable t) {
        forceClose(child, t);
    }
}

public ChannelFuture register(final ChannelPromise promise) {
    ObjectUtil.checkNotNull(promise, "promise");
    promise.channel().unsafe().register(this, promise);
    return promise;
}

public final void register(EventLoop eventLoop, final ChannelPromise promise) {
    //省略验证代码
    //所有的复制操作, 都交给eventLoop处理
    AbstractChannel.this.eventLoop = eventLoop;

    if (eventLoop.inEventLoop()) {
        //做实际主注册
        register0(promise);
    } else {
        try {
            eventLoop.execute(new Runnable() {
                @Override
                public void run() {
                    register0(promise);
                }
            });
        } catch (Throwable t) {
            //代码省略
        }
    }
}

private void register0(ChannelPromise promise) {
    try {
        //省略代码
        //做实际的注册
        doRegister();
        neverRegistered = false;
        registered = true;
        //触发事件
        pipeline.invokeHandlerAddedIfNeeded();
        safeSetSuccess(promise);
        //触发注册成功事件
        pipeline.fireChannelRegistered();
        if (isActive()) {
            if (firstRegistration) {
                //传播active事件(4)
                pipeline.fireChannelActive();
            } else if (config().isAutoRead()) {
                beginRead();
            }
        }
    } catch (Throwable t) {
        //省略代码
    }
}

protected void doRegister() throws Exception {
    boolean selected = false;
    for (;;) {
        try {
            //jdk底层的注册方法
            //第一个参数为selector, 第二个参数表示不关心任何事件
            selectionKey = javaChannel().register(eventLoop().selector, 0, this);
            return;
        } catch (CancelledKeyException e) {
            //省略代码
        }
    }
}