netty

netty的主从多线程模型，主线程（线程池中就一个线程）主要负责接收客户端的链接，然后转发给从线程（8个容量的线程池）进行实际的业务处理

MainReactor = NioServerBoss
SubReactor = NioWorker

 

 

 

 

 

 

 

 

 

从图上看NioWorker 和 NioServer都继承AbstractNioSelector，主要的业务逻辑都会在这里进行处理

在初始化的时候，会把主从的线程池进行初始化，最后都会执行得到AbstractNioSelector的run方法：

 

 

主从 区别在于processTaskQueue和process的实现一个是boss，一个是worker

worker的processTaskQueue，调用nioworker里面的Register类的run方法，主要几件事：设置channel非阻塞，注册selector,触发链接客户端（pipleline的上行链接事件）

 

public void run() {
            SocketAddress localAddress = channel.getLocalAddress();
            SocketAddress remoteAddress = channel.getRemoteAddress();

            if (localAddress == null || remoteAddress == null) {
                if (future != null) {
                    future.setFailure(new ClosedChannelException());
                }
                close(channel, succeededFuture(channel));
                return;
            }

            try {
                if (server) {
                    channel.channel.configureBlocking(false);
                }

                channel.channel.register(
                        selector, channel.getInternalInterestOps(), channel);

                if (future != null) {
                    channel.setConnected();
                    future.setSuccess();
                }

                if (server || !((NioClientSocketChannel) channel).boundManually) {
                    fireChannelBound(channel, localAddress);
                }
                fireChannelConnected(channel, remoteAddress);
            } catch (IOException e) {
                if (future != null) {
                    future.setFailure(e);
                }
                close(channel, succeededFuture(channel));
                if (!(e instanceof ClosedChannelException)) {
                    throw new ChannelException(
                            "Failed to register a socket to the selector.", e);
                }
            }
        }

 process方法是nioworker里的process，开始轮询selector里面已经就绪链接，通过nioworker读取bytebuffer-》转成channelbuffer，并触发消息处理机制（fireMessageReceived）它会调用我们的在pipeline中添加的各种handler处理

protected void process(Selector selector) throws IOException {
    Set<SelectionKey> selectedKeys = selector.selectedKeys();
    // check if the set is empty and if so just return to not create garbage by
    // creating a new Iterator every time even if there is nothing to process.
    // See https://github.com/netty/netty/issues/597
    if (selectedKeys.isEmpty()) {
        return;
    }
    for (Iterator<SelectionKey> i = selectedKeys.iterator(); i.hasNext();) {
        SelectionKey k = i.next();
        i.remove();
        try {
            int readyOps = k.readyOps();
            if ((readyOps & SelectionKey.OP_READ) != 0 || readyOps == 0) {
                if (!read(k)) {
                    // Connection already closed - no need to handle write.
                    continue;
                }
            }
            if ((readyOps & SelectionKey.OP_WRITE) != 0) {
                writeFromSelectorLoop(k);
            }
        } catch (CancelledKeyException e) {
            close(k);
        }

        if (cleanUpCancelledKeys()) {
            break; // break the loop to avoid ConcurrentModificationException
        }
    }
}

protected boolean read(SelectionKey k) {
        final SocketChannel ch = (SocketChannel) k.channel();
        final NioSocketChannel channel = (NioSocketChannel) k.attachment();

        final ReceiveBufferSizePredictor predictor =
            channel.getConfig().getReceiveBufferSizePredictor();
        final int predictedRecvBufSize = predictor.nextReceiveBufferSize();
        final ChannelBufferFactory bufferFactory = channel.getConfig().getBufferFactory();

        int ret = 0;
        int readBytes = 0;
        boolean failure = true;

        ByteBuffer bb = recvBufferPool.get(predictedRecvBufSize).order(bufferFactory.getDefaultOrder());
        try {
            while ((ret = ch.read(bb)) > 0) {
                readBytes += ret;
                if (!bb.hasRemaining()) {
                    break;
                }
            }
            failure = false;
        } catch (ClosedChannelException e) {
            // Can happen, and does not need a user attention.
        } catch (Throwable t) {
            fireExceptionCaught(channel, t);
        }

        if (readBytes > 0) {
            bb.flip();

            final ChannelBuffer buffer = bufferFactory.getBuffer(readBytes);
            buffer.setBytes(0, bb);
            buffer.writerIndex(readBytes);

            // Update the predictor.
            predictor.previousReceiveBufferSize(readBytes);

            // Fire the event.
            fireMessageReceived(channel, buffer);
        }

        if (ret < 0 || failure) {
            k.cancel(); // Some JDK implementations run into an infinite loop without this.
            close(channel, succeededFuture(channel));
            return false;
        }

        return true;
    }

 

再看一下boss的这边，可以肯定的是，会链接客户端因为这是入口，在一个就是来链接之后如何交给nioworker处理，并且看一下是如何分配的，

processTaskQueue的方法是由nioserverboss的registerTask类中的run方法，下面会有什么时候把这个task放到队列：

public void run() {
            boolean bound = false;
            boolean registered = false;
            try {
//绑定地址端口
                channel.socket.socket().bind(localAddress, channel.getConfig().getBacklog());
                bound = true;

                future.setSuccess();
                fireChannelBound(channel, channel.getLocalAddress());
//注册accept事件

                channel.socket.register(selector, SelectionKey.OP_ACCEPT, channel);

                registered = true;
            } catch (Throwable t) {
                future.setFailure(t);
                fireExceptionCaught(channel, t);
            } finally {
                if (!registered && bound) {
                    close(channel, future);
                }
            }
        }

nioserverboss的process方法

 protected void process(Selector selector) {
        Set<SelectionKey> selectedKeys = selector.selectedKeys();
        if (selectedKeys.isEmpty()) {
            return;
        }
//轮询触发的链接
        for (Iterator<SelectionKey> i = selectedKeys.iterator(); i.hasNext();) {
            SelectionKey k = i.next();
            i.remove();
            NioServerSocketChannel channel = (NioServerSocketChannel) k.attachment();

            try {
                // accept connections in a for loop until no new connection is ready
                for (;;) {
                    SocketChannel acceptedSocket = channel.socket.accept();
                    if (acceptedSocket == null) {
                        break;
                    }
                    registerAcceptedChannel(channel, acceptedSocket, thread);
                }
            } catch (CancelledKeyException e) {
                // Raised by accept() when the server socket was closed.
                k.cancel();
                channel.close();
            } catch (SocketTimeoutException e) {
                // Thrown every second to get ClosedChannelException
                // raised.
            } catch (ClosedChannelException e) {
                // Closed as requested.
            } catch (Throwable t) {
                if (logger.isWarnEnabled()) {
                    logger.warn(
                            "Failed to accept a connection.", t);
                }

                try {
                    Thread.sleep(1000);
                } catch (InterruptedException e1) {
                    // Ignore
                }
            }
        }
    }

private static void registerAcceptedChannel(NioServerSocketChannel parent, SocketChannel acceptedSocket,
                                     Thread currentThread) {
    try {
        ChannelSink sink = parent.getPipeline().getSink();
        ChannelPipeline pipeline =
                parent.getConfig().getPipelineFactory().getPipeline();
//轮询每个nioworker，workers[Math.abs(workerIndex.getAndIncrement() % workers.length)]
        NioWorker worker = parent.workerPool.nextWorker();
//这里把客户端的socket绑定到了nioworker上，
        worker.register(new NioAcceptedSocketChannel(
                parent.getFactory(), pipeline, parent, sink
                , acceptedSocket,
                worker, currentThread), null);
    } catch (Exception e) {
        if (logger.isWarnEnabled()) {
            logger.warn(
                    "Failed to initialize an accepted socket.", e);
        }

        try {
            acceptedSocket.close();
        } catch (IOException e2) {
            if (logger.isWarnEnabled()) {
                logger.warn(
                        "Failed to close a partially accepted socket.",
                        e2);
            }
        }
    }
}

abstractNioselector的register

public void register(Channel channel, ChannelFuture future) {
　　//这里的register又会走一遍nioserverboss的registerTask类中的run方法
    Runnable task = createRegisterTask(channel, future);
    registerTask(task);
}

protected final void registerTask(Runnable task) {
//添加任务到队列
    taskQueue.add(task);

    Selector selector = this.selector;

    if (selector != null) {
//cas操作，设置唤醒selector
        if (wakenUp.compareAndSet(false, true)) {
            selector.wakeup();
        }
    } else {
        if (taskQueue.remove(task)) {
            // the selector was null this means the Worker has already been shutdown.
            throw new RejectedExecutionException("Worker has already been shutdown");
        }
    }
}

再看一下NioAcceptedSocketChannel

final class NioAcceptedSocketChannel extends NioSocketChannel {

final Thread bossThread;

    NioAcceptedSocketChannel(
ChannelFactory factory, ChannelPipeline pipeline,
            Channel parent, ChannelSink sink,
            SocketChannel socket, NioWorker worker, Thread bossThread) {

super(parent, factory, pipeline, sink, socket, worker);

        this.bossThread = bossThread;

        setConnected();
//产生链接事件，把链接交给nioworker
        fireChannelOpen(this);
    }
}

 

 

这里的register又会走一遍nioserverboss的registerTask类中的run方法