Zookeeper实现分布式锁的原理

​ Zookeeper基于临时有序节点+watch机制实现分布式锁原理； 所有线程启动后，所有线程都会在zookeeper中创建临时有序节点（抢占锁），只有最小临时有序节点的那个线程能够抢占到锁， 其他未抢占到锁的线程处于等待状态和监听比自己小的节点； 当抢占到锁的线程释放锁后，比自己大的节点会监听到该节点发生变化，并且去尝试抢占锁；

源码

Maven 依赖

  <dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-web</artifactId>
  </dependency>

  <dependency>
    <groupId>org.apache.curator</groupId>
    <artifactId>curator-recipes</artifactId>
    <version>5.1.0</version>
  </dependency>

  <dependency>
    <groupId>org.projectlombok</groupId>
    <artifactId>lombok</artifactId>
    <version>1.18.12</version>
  </dependency>

application.yml

server:
  port: 8085
spring:
  curator:
    retryCount: 5  #重试次数
    elapsedTimeMs: 5000   #重试间隔时间 
    connectString: 127.0.0.1:2181   #zookeeper地址
    sessionTimeoutMs: 60000  #session超时时间
    connectionTimeoutMs: 15000  #连接超时时间

CuratorConfig 配置类

@Value("${spring.curator.retryCount}")
    private int retryCount;
    @Value("${spring.curator.elapsedTimeMs}")
    private int elapsedTimeMs;
    @Value("${spring.curator.connectString}")
    private String connectString;
    @Value("${spring.curator.sessionTimeoutMs}")
    private int sessionTimeoutMs;
    @Value("${spring.curator.connectionTimeoutMs}")
    private int connectionTimeoutMs;

    @Bean
    public CuratorFramework curatorFramework() {
        RetryPolicy retryPolicy = new ExponentialBackoffRetry(elapsedTimeMs, retryCount);
        CuratorFramework client = CuratorFrameworkFactory.newClient(
                connectString,
                sessionTimeoutMs,
                connectionTimeoutMs,
                retryPolicy);
        client.start();
        return client;
    }

Controller 控制器类

@RestController
@Slf4j
public class CuratorLockController {

    @Autowired
    private CuratorFramework client;

    /**
     * 锁测试共享变量
     */
    private Integer lockCount = 10;

    @GetMapping("/lock")
    public void lock() throws Exception {
        // Zk分布式锁
        InterProcessMutex lock = new InterProcessMutex(client, "/lock/lockCount");

        if (lock.acquire(5, TimeUnit.SECONDS)) {
            try {
                if (lockCount <= 0) {
                    throw new Exception("lockCount不能小于0");
                }
                // 业务逻辑
                lockCount--;
                log.info("lockCount值："+lockCount);
            } finally {
                lock.release();
            }
        }
    }

Application 启动类

@SpringBootApplication
public class ZkLockApplication {
    
    public static void main(String[] args) {
        SpringApplication.run(ZkLockApplication.class,args);
    }
}

测试

​ 打开 JMeter，设置10个线程，点击运行：

序号依次递减，如下图：

参考：

http://curator.apache.org/index.htmls

https://mvnrepository.com/artifact/org.apache.curatorZookeeper

http://curator.apache.org/apidocs/org/apache/curator/framework/CuratorFrameworkFactory.html

源码