zookeeper分布式锁模拟12306买票

未加锁时容易出现重复买票情况

代码

java 复制代码

public class Ticket12306 implements Runnable{

    // 票数
    private int ticketNums = 10;

    @Override
    public void run() {
        while (true){
            if (ticketNums>0){
                System.out.println(Thread.currentThread() + "抢到了第" + ticketNums + "张票");
                ticketNums--;
            }
        }
    }
}

java 复制代码

public class Main {
    public static void main(String[] args) {
        Ticket12306 ticket = new Ticket12306();

        // 模拟多个线程抢票
        Thread thread1 = new Thread(ticket, "窗口1");
        Thread thread2 = new Thread(ticket, "窗口2");

        thread1.start();
        thread2.start();
    }
}

结果

加分布式锁后

java 复制代码

public class Ticket12306 implements Runnable{

    // 票数
    private int ticketNums = 10;

    public Ticket12306() {
        // 重试策略
        ExponentialBackoffRetry retryPolicy = new ExponentialBackoffRetry(3000, 10);
        CuratorFramework client = CuratorFrameworkFactory.builder()
                .connectString("192.168.106.140:2181")
                .sessionTimeoutMs(60 * 1000)
                .connectionTimeoutMs(15 * 1000)
                .retryPolicy(retryPolicy)
                .build();
        // 开启连接
        client.start();

        lock = new InterProcessMutex(client,"/lock");
    }

    private InterProcessMutex lock;

    @Override
    public void run() {
        while (true){
            try {
                // 获取锁
                lock.acquire(3, TimeUnit.SECONDS);
                if (ticketNums>0){
                    System.out.println(Thread.currentThread() + "抢到了第" + ticketNums + "张票");
                    ticketNums--;
                }
                // 解锁
            } catch (Exception e) {
                throw new RuntimeException(e);
            } finally {
                try {
                    lock.release();
                } catch (Exception e) {
                    throw new RuntimeException(e);
                }
            }

        }
    }
}

出现问题

期间还遇到了一个小插曲，这里顺便记录下。

在连接zookeeper时候出现下面这个错误，刚开始以为是服务端zookeeper出问题了，但是检查后发现没问题，在服务端可正常创建、修改节点信息。

解决方案：关闭服务器防火墙

powershell 复制代码

systemctl stop firewalld