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8.NIO-多线程优化

时间:2022-10-12 13:45:49浏览次数:60  
标签:workSelector NIO register iter sc new 多线程 优化 public

1.4.4、多线程优化

设计思路:分两组选择器

  • 单线程配一个选择器,专门处理accpet事件(建立连接) BOSS
  • 创建多线程,每个线程一个选择器,专门处理read事件 WORK

服务端

@Slf4j
public class ThreadServer {
    public static void main(String[] args) throws IOException, InterruptedException {
        Thread.currentThread().setName("boss thread");
        ServerSocketChannel ssc = ServerSocketChannel.open();
        ssc.configureBlocking(false);

        Selector bossSelector = Selector.open();
        ssc.register(bossSelector, SelectionKey.OP_ACCEPT);
        ssc.bind(new InetSocketAddress(50001));

        Worker worker = new Worker("work thread");
        worker.register();

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

                    sc.register(worker.workSelector, SelectionKey.OP_READ, null);
                    log.debug("after register...{}", sc.getRemoteAddress());
                }
            }
        }
    }

    @Data
    static class Worker implements Runnable {
        private String name;
        private Selector workSelector;
        private volatile boolean flag = false;

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

        //初始化线程和selector

        public void register() throws IOException {
            if (!flag) {
                workSelector = Selector.open();
                new Thread(this, name).start();
                flag = true;
            }

        }

        @Override
        public void run() {
            while (true) {
                try {
                    workSelector.select();
                    Iterator<SelectionKey> iter = workSelector.selectedKeys().iterator();
                    while (iter.hasNext()) {
                        SelectionKey key = iter.next();
                        iter.remove();
                        if (key.isReadable()) {
                            ByteBuffer buffer = ByteBuffer.allocate(16);
                            SocketChannel sc = (SocketChannel) key.channel();
                            log.debug("read...{}", sc.getRemoteAddress());
                            sc.read(buffer);
                            buffer.flip();
                            ByteBufferUtil.debugAll(buffer);
                        }
                    }
                } catch (IOException e) {
                    throw new RuntimeException(e);
                }
            }
        }
    }
}

客户端

public class Client {
    public static void main(String[] args) throws IOException {
        SocketChannel sc = SocketChannel.open();
        sc.connect(new InetSocketAddress("localhost", 50001));
        SocketAddress address = sc.getLocalAddress();
        System.out.println(address.toString());
        sc.write(Charset.defaultCharset().encode("123456"));
        System.in.read();
    }
}

问题:只打印了before信息,没有打印after和read信息,因为worker线程start后,run方法中workSelector.select();会阻塞,在主线程boss中,sc.register(workerSelecotr..)就不会执行.

run方法是在work线程中执行,sc.register是在boss线程中执行,只要run运行在register之前就会阻塞、

解决:把worker.register();放到sc.register之前,这是sc.register就可能发生在work.register之前,selector.select()后执行,就没有问题了。

新问题:再来一个客户端,之前的select()方法已经执行阻塞了,新的就register不了

解决:把worker.register();和sc.register(worker.workSelector, SelectionKey.OP_READ, null);放早同一个线程里,就可以控制顺序

public void register(SocketChannel sc) throws IOException {
    if (!flag) {
        workSelector = Selector.open();
        new Thread(this, name).start();
        flag = true;
    }

    sc.register(workSelector, SelectionKey.OP_READ, null);
}

但是register还在在boss线程中被调用,只有run方法才是在work线程中执行。

  • 方案1:采用一个队列,将sc.register(workSelector, SelectionKey.OP_READ, null)放入队列中,然后在run方法中从队列中拿到任务,执行,还要调用warkUp唤醒select的阻塞
@Slf4j
public class ThreadServer {
    public static void main(String[] args) throws IOException, InterruptedException {
        Thread.currentThread().setName("boss thread");
        ServerSocketChannel ssc = ServerSocketChannel.open();
        ssc.configureBlocking(false);

        Selector bossSelector = Selector.open();
        ssc.register(bossSelector, SelectionKey.OP_ACCEPT);
        ssc.bind(new InetSocketAddress(50001));

        Worker worker = new Worker("work thread");

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

                    log.debug("after register...{}", sc.getRemoteAddress());
                }
            }
        }
    }

    @Data
    static class Worker implements Runnable {
        private String name;
        private Selector workSelector;
        private volatile boolean flag = false;

        private ConcurrentLinkedQueue<Runnable> queue = new ConcurrentLinkedQueue<>();

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

        //初始化线程和selector

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

        @Override
        public void run() {
            while (true) {
                try {
                    workSelector.select();

                    //取出任务并执行
                    Runnable task = queue.poll();
                    if (task != null) {
                        task.run();
                    }

                    Iterator<SelectionKey> iter = workSelector.selectedKeys().iterator();
                    while (iter.hasNext()) {
                        SelectionKey key = iter.next();
                        iter.remove();
                        if (key.isReadable()) {
                            ByteBuffer buffer = ByteBuffer.allocate(16);
                            SocketChannel sc = (SocketChannel) key.channel();
                            log.debug("read...{}", sc.getRemoteAddress());
                            sc.read(buffer);
                            buffer.flip();
                            ByteBufferUtil.debugAll(buffer);
                        }
                    }
                } catch (IOException e) {
                    throw new RuntimeException(e);
                }
            }
        }
    }
}
  • 方案2:不用队列,23步都是在boss线程中执行,顺序固定

分析:wakeup可以在select前或后唤醒,相当于发一张票

  1. 123顺序,先阻塞,然后warkup唤醒,没问题
  2. 213,ok
  3. 231,和第2情况相同

标签:workSelector,NIO,register,iter,sc,new,多线程,优化,public
From: https://www.cnblogs.com/jpymll/p/16784231.html

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