1 分布式锁

1.1 概念

1.2 原理

2 案例：模拟12306售票

2.1 Curator实现分布式锁API

在Curator中有五种锁方案：

• InterProcessSemaphoreMutex：分布式排它锁（非可重入锁）
• InterProcessMutex：分布式可重入排它锁
• InterProcessReadWriteLock：分布式读写锁
• InterProcessMultiLock：将多个锁作为单个实体管理的容器
• InterProcessSemaphoreV2：共享信号量

2.2 Zookeeper分布式锁实现

架构：

package com.yppah.curator;

/**
 * @Author: haifei
 * @Date: 2022/10/22 17:04
 */
public class LockTest {
    public static void main(String[] args) {
        Ticket12306 ticket12306 = new Ticket12306();
        //模拟客户端多个
        Thread t1 = new Thread(ticket12306,"携程");
        Thread t2 = new Thread(ticket12306,"飞猪");
        t1.start();
        t2.start();
    }
}

package com.yppah.curator;

import org.apache.curator.RetryPolicy;
import org.apache.curator.framework.CuratorFramework;
import org.apache.curator.framework.CuratorFrameworkFactory;
import org.apache.curator.framework.recipes.locks.InterProcessMutex;
import org.apache.curator.retry.ExponentialBackoffRetry;

import java.util.concurrent.TimeUnit;

/**
 * @Author: haifei
 * @Date: 2022/10/22 17:05
 */
// 模拟服务端1个
public class Ticket12306 implements Runnable{

    private int tickets = 10;//数据库的票数
    private InterProcessMutex lock; //分布式可重入排他锁

    public Ticket12306(){
        RetryPolicy retryPolicy = new ExponentialBackoffRetry(3000, 10);
        CuratorFramework client = CuratorFrameworkFactory.builder()
                .connectString("101.43.128.227:2181")
                .sessionTimeoutMs(60 * 1000)
                .connectionTimeoutMs(15 * 1000)
                .retryPolicy(retryPolicy)
                .build();
        client.start();
        lock = new InterProcessMutex(client,"/lock");
    }

    @Override
    public void run() {
        while(true){
            //获取锁
            try {
                lock.acquire(3, TimeUnit.SECONDS);
                if(tickets > 0){
                    System.out.println(Thread.currentThread()+":"+tickets);
                    Thread.sleep(100);
                    tickets--;
                }
            } catch (Exception e) {
                e.printStackTrace();
            }finally {
                //释放锁
                try {
                    lock.release();
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        }
    }

}