分布式锁的实现几种方式

• 基于zookeeper原生实现分布式锁

<dependency>
    <groupId>org.apache.zookeeper</groupId>
    <artifactId>zookeeper</artifactId>
    <version>3.8.0</version>
</dependency>

通过Watcher实现分布式锁

@Slf4j
public class ZkLock implements AutoCloseable, Watcher {
    private String znode;
    private ZooKeeper zooKeeper;
    public ZkLock() throws IOException {
        this.zooKeeper = new ZooKeeper("localhost:2181", 10000, this);
    }

    /**
     * 创建及获取锁
     */
    public boolean getLock(String businessCode) {
        try {
            // 创建业务根结点
            Stat stat = zooKeeper.exists("/" + businessCode, false);
            if (stat == null) {
                zooKeeper.create("/" + businessCode, businessCode.getBytes(StandardCharsets.UTF_8), ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT);
            }
            // 创建瞬时有序节点 /order/order_000001
            znode = zooKeeper.create("/" + businessCode + "/" + businessCode + "_", businessCode.getBytes(StandardCharsets.UTF_8), ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT_SEQUENTIAL);
            // 获取业务节点下所有子节点
            List<String> childrenNodes = zooKeeper.getChildren("/" + businessCode, false);
            Collections.sort(childrenNodes);
            // 获取序号最小的（第一个）子节点
            String firstNode = childrenNodes.get(0);
            // 如果创建的节点是第一个子节点则获得锁
            if (znode.endsWith(firstNode)) {
                return true;
            }
            // 不是第一个子节点，则监听前一个节点
            String lastNode = firstNode;
            for (String node : childrenNodes) {
                if (znode.endsWith(node)) {
                    zooKeeper.exists("/" + businessCode + "/" + lastNode, true);
                    break;
                }
                lastNode = node;
            }
            // 获取不到锁，线程等待直到当前锁的删除
            synchronized (this) {
                wait();
            }
            return true;
        } catch (Exception e) {
            e.printStackTrace();
        }
        return false;
    }

    @Override
    public void close() throws Exception {
        zooKeeper.delete(znode, -1);
        zooKeeper.close();
        log.info("我已经释放了锁");
    }

    @Override
    public void process(final WatchedEvent watchedEvent) {
        // 节点消失唤醒线程
        if (watchedEvent.getType() == Event.EventType.NodeDeleted) {
            synchronized (this) {
                notify();
            }
        }

    }
}

分别开启两个服务去测试

/**
 * 基于zookeeper原生实现分布式锁
 */
@GetMapping("zkLock")
public String zookeeperLock() {
   log.info("方法开始执行");
   try (ZkLock zkLock = new ZkLock()) {
       if (zkLock.getLock("order")) {
           log.info("获得了锁");
           Thread.sleep(10000);
       }
   } catch (Exception e) {
        e.printStackTrace();
   }
   log.info("方法执行完成");
   return "方法执行完成";
 }

• 基本zookeeper curator客户端实现分布式锁

<dependency>
      <groupId>org.apache.curator</groupId>
      <artifactId>curator-recipes</artifactId>
      <version>5.4.0</version>
</dependency>

配置相应的baen

/**
 * Curator初始化连接客户端
 */
@Bean(initMethod = "start", destroyMethod = "close")
public CuratorFramework getCuratorFramework() {
    RetryPolicy retryPolicy = new ExponentialBackoffRetry(1000, 3);
    CuratorFramework client = CuratorFrameworkFactory.newClient("localhost:2181", retryPolicy);
    return client;
}

配置完连接后直接可以使用分布式锁了

@Autowired
private CuratorFramework curatorFramework;
/**
 * 基于zookeeper curator客户端实现分布式锁（客户端已实现分布式锁）
 */
@GetMapping("curatorLock")
public String curatorLock() {
  log.info("方法开始执行");
  InterProcessMutex lock = new InterProcessMutex(curatorFramework, "/order");
  try {
    if (lock.acquire(30, TimeUnit.SECONDS)) {
        log.info("获得了锁");
        Thread.sleep(10000);
    }
  } catch (Exception e) {
      e.printStackTrace();
  }finally {
    try {
      log.info("释放了锁");
      lock.release();
    } catch (Exception e) {
        e.printStackTrace();
    }
  }
  log.info("方法执行完成");
  return "方法执行完成";
}

• 基础redission实现分布式锁

<dependency>
  <groupId>org.redisson</groupId>
  <artifactId>redisson-spring-boot-starter</artifactId>
  <version>3.18.0</version>
</dependency>

yml配置

spring:
  redis:
    host: localhost
    port: 6379

配置好了之后就可以直接使用分布式锁了

@RestController
public class RedissonController {
    @Autowired
    private RedissonClient redissonClient;

    @GetMapping("redissonLock")
    public String redissonLock() {
        log.info("进入了方法");
        RLock lock = redissonClient.getLock("order");
        try {
            lock.lock(30, TimeUnit.SECONDS);
            log.info("获得了锁");
            Thread.sleep(10000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        } finally {
            log.info("释放🔒");
            lock.unlock();
        }
        log.info("方法请求完成");
        return "方法请求完成";
    }
}