使用多线程优化NIO

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前言

NIO是一个Selector同时轮询多个Channel，监听读写事件。我们可以使用多线程来处理。多个Selector线程，多个处理读写的线程。


让boss线程专门处理accept事件。

worker线程来处理读事件。但是这里有一个问题，boss线程会阻塞worker0线程的执行，所以这里需要专门处理。

一、使用队列共享资源

• 目的是：让boss线程在worker线程中执行

@Slf4j
public class MultiThreadServer {

    static class Worker implements Runnable {

        private Thread thread;
        private Selector selector;
        private String name;
        private ConcurrentLinkedQueue<Runnable> queue = new ConcurrentLinkedQueue<>();

        private volatile boolean start = false;

        public Worker(String name) {
            this.name = name;
        }

        public void register(SocketChannel sc) throws IOException {
            if (!start) {
                selector = Selector.open();
                thread = new Thread(this, name);
                thread.start();
                start = true;
            }
            queue.add(() -> {
                try {
                    sc.register(selector, SelectionKey.OP_READ, null);
                } catch (ClosedChannelException e) {
                    e.printStackTrace();
                }
            });
            //唤醒select
            selector.wakeup();

        }

        @Override
        public void run() {
            while (true) {
                try {
                    selector.select();
                    Runnable task = queue.poll();
                    if (task != null) {
                        task.run();//这个位置执行了 sc.register(selector,SelectionKey.OP_READ,null);
                    }
                    Iterator<SelectionKey> iterator = selector.selectedKeys().iterator();
                    while (iterator.hasNext()) {
                        SelectionKey key = iterator.next();
                        iterator.remove();
                        if (key.isReadable()) {
                            ByteBuffer buffer = ByteBuffer.allocate(16);
                            SocketChannel channel = (SocketChannel) key.channel();
                            log.debug("read...{}", channel.getRemoteAddress());
                            channel.read(buffer);
                            buffer.flip();
                            debugAll(buffer);
                        }
                    }
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
    }

    public static void main(String[] args) throws IOException {
        Thread.currentThread().setName("boss");
        ServerSocketChannel ssc = ServerSocketChannel.open();
        ssc.configureBlocking(false);
        Selector boss = Selector.open();
        SelectionKey bossKey = ssc.register(boss, 0, null);
        bossKey.interestOps(SelectionKey.OP_ACCEPT);
        ssc.bind(new InetSocketAddress(8080));
        Worker worker = new Worker("worker-0");

        while (true) {
            boss.select();
            Iterator<SelectionKey> iterator = boss.selectedKeys().iterator();
            while (iterator.hasNext()) {
                SelectionKey key = iterator.next();
                iterator.remove();
                if (key.isAcceptable()) {
                    SocketChannel sc = ssc.accept();
                    sc.configureBlocking(false);
                    log.debug("connected...{}", sc.getRemoteAddress());
                    log.debug("before register...{}", sc.getRemoteAddress());
                    //关联selector
                    worker.register(sc);
                    log.debug("after register...{}", sc.getRemoteAddress());
                }
            }
        }
    }
}

二、模拟多worker

    public static void main(String[] args) throws IOException {
        Thread.currentThread().setName("boss");
        ServerSocketChannel ssc = ServerSocketChannel.open();
        ssc.configureBlocking(false);
        Selector boss = Selector.open();
        SelectionKey bossKey = ssc.register(boss, 0, null);
        bossKey.interestOps(SelectionKey.OP_ACCEPT);
        ssc.bind(new InetSocketAddress(8080));
        Worker[] workers=new Worker[Runtime.getRuntime().availableProcessors()];
        for (int i=0;i<workers.length;i++){
            workers[i]=new Worker("worker-"+i);
        }
        AtomicInteger index=new AtomicInteger();
        while (true){
            boss.select();
            Iterator<SelectionKey> iterator = boss.selectedKeys().iterator();
            while (iterator.hasNext()) {
                SelectionKey key = iterator.next();
                iterator.remove();
                if(key.isAcceptable()){
                    SocketChannel sc = ssc.accept();
                    sc.configureBlocking(false);
                    log.debug("connected...{}",sc.getRemoteAddress());
                    log.debug("before register...{}",sc.getRemoteAddress());
                    //关联selector  round robin 轮询workers
                    workers[index.getAndIncrement()%workers.length].register(sc);
                    log.debug("after register...{}",sc.getRemoteAddress());
                }
            }
        }
    }