Reactor 模式在Netty中的应用

Reactor 模式在Netty中的应用

典型的Rector模式

mainReactor

服务端创建成功后，会监听Accept操作，其中ServerSocketchannel中的PipeLine中现在包含3个handler

服务端监听到连接事件后，会创建代表客户端的socketChannel,并向workgroup注册channel,监听后续该channel读写事件。一言以蔽之，bossGroup只负责接收连接请求，并创建socketChannel,分发到workgroup中执行耗时的读写操作。

接收连接请求

if ((readyOps & (SelectionKey.OP_READ | SelectionKey.OP_ACCEPT)) != 0 || readyOps == 0) {
    unsafe.read();
}

try {
    do {
        int localRead = doReadMessages(readBuf);
        if (localRead == 0) {
            break;
        }
        if (localRead < 0) {
            closed = true;
            break;
        }

        allocHandle.incMessagesRead(localRead);
    } while (allocHandle.continueReading());

注意ServerSocketchannel的allocHandle默认最大为1。

@Override
protected int doReadMessages(List<Object> buf) throws Exception {
    SocketChannel ch = SocketUtils.accept(javaChannel());
    try {
        if (ch != null) {
            buf.add(new NioSocketChannel(this, ch));
            return 1;
        }
    } catch (Throwable t) {
        try {
            ch.close();
        } catch (Throwable t2) {
        }
    }

    return 0;
}

在接收到连接请求后，会触发PipeLine的firChannelRead事件。pipline中包含ServerBootstrap，read方法如下：

public void channelRead(ChannelHandlerContext ctx, Object msg) {
    final Channel child = (Channel) msg;

    child.pipeline().addLast(childHandler);

    setChannelOptions(child, childOptions, logger);

    for (Entry<AttributeKey<?>, Object> e: childAttrs) {
        child.attr((AttributeKey<Object>) e.getKey()).set(e.getValue());
    }

    try {
        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);
    }
}

至此，将NioSocketChannel注册到workgroup中执行。