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如何利用Zookeeper实现分布式锁

小樊
60
2025-05-09 23:09:42
栏目: 大数据

ZooKeeper是一个分布式协调服务,它可以用来实现分布式锁。以下是使用ZooKeeper实现分布式锁的基本步骤:

1. 创建ZooKeeper客户端

首先,你需要创建一个ZooKeeper客户端连接到ZooKeeper集群。

import org.apache.zookeeper.ZooKeeper; public class ZooKeeperClient { private static final String ZK_ADDRESS = "localhost:2181"; private static final int SESSION_TIMEOUT = 3000; private ZooKeeper zk; public ZooKeeperClient() throws IOException { zk = new ZooKeeper(ZK_ADDRESS, SESSION_TIMEOUT, event -> { // 处理连接事件 }); } public ZooKeeper getZk() { return zk; } } 

2. 创建锁节点

在ZooKeeper中创建一个临时顺序节点来表示锁。

import org.apache.zookeeper.CreateMode; import org.apache.zookeeper.ZooDefs; import org.apache.zookeeper.data.Stat; public class DistributedLock { private static final String LOCK_ROOT = "/locks"; private static final String LOCK_NODE = LOCK_ROOT + "/lock_"; private ZooKeeper zk; private String lockPath; public DistributedLock(ZooKeeper zk) { this.zk = zk; try { // 创建锁的根节点 Stat stat = zk.exists(LOCK_ROOT, false); if (stat == null) { zk.create(LOCK_ROOT, new byte[0], ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT); } } catch (Exception e) { e.printStackTrace(); } } public void lock() throws Exception { lockPath = zk.create(LOCK_NODE, new byte[0], ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.EPHEMERAL_SEQUENTIAL); while (true) { List<String> children = zk.getChildren(LOCK_ROOT, false); Collections.sort(children); if (lockPath.endsWith(children.get(0))) { // 获取到锁 return; } else { // 监听前一个节点的删除事件 String previousNode = getPreviousNode(children, lockPath); Stat stat = zk.exists(LOCK_ROOT + "/" + previousNode, event -> { if (event.getType() == Watcher.Event.EventType.NodeDeleted) { synchronized (this) { notifyAll(); } } }); if (stat != null) { wait(); } } } } private String getPreviousNode(List<String> children, String currentNode) { int index = children.indexOf(currentNode.substring(LOCK_ROOT.length() + 1)); return children.get(index - 1); } public void unlock() throws Exception { if (lockPath != null) { zk.delete(lockPath, -1); lockPath = null; } } } 

3. 使用锁

在你的分布式应用中使用这个锁来保证操作的原子性。

public class DistributedApplication { public static void main(String[] args) { try { ZooKeeperClient zkClient = new ZooKeeperClient(); DistributedLock lock = new DistributedLock(zkClient.getZk()); lock.lock(); // 执行需要加锁的操作 System.out.println("Lock acquired, performing operation..."); // 模拟操作时间 Thread.sleep(5000); lock.unlock(); System.out.println("Lock released."); } catch (Exception e) { e.printStackTrace(); } } } 

注意事项

  1. 异常处理:在实际应用中,需要仔细处理各种异常情况,比如连接丢失、节点删除等。
  2. 性能考虑:ZooKeeper的写操作是相对较慢的,因此在高并发场景下需要谨慎使用。
  3. 会话管理:确保ZooKeeper客户端会话的有效性,避免因为会话过期导致锁失效。

通过以上步骤,你可以利用ZooKeeper实现一个基本的分布式锁。根据具体需求,你可能还需要进一步优化和扩展这个实现。

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