Zookeeper分布式同步与一致性

Zookeeper是一个开源的分布式服务框架，它提供了分布式数据一致性解决方案，可以用于实现分布式应用的协调服务。

在Zookeeper中，数据是按照Znode树的结构组织起来的，每个Znode可以保存数据，同时可以有子Znode。Zookeeper的特点是，客户端可以在Znode上设置监听器，当Znode有变化时（如数据改变，子节点增减），Zookeeper会通知客户端。

以下是一个简单的Zookeeper使用示例，展示了如何在Java中创建Znode，设置数据，获取数据，以及监听Znode的变化。

import org.apache.zookeeper.ZooKeeper;
import org.apache.zookeeper.WatchedEvent;
import org.apache.zookeeper.Watcher;
import org.apache.zookeeper.Watcher.Event.EventType;
import org.apache.zookeeper.ZooDefs.Ids;
 
public class ZookeeperExample implements Watcher {
 
    private static final String CONNECT_STRING = "127.0.0.1:2181";
    private static final int SESSION_TIMEOUT = 2000;
    private ZooKeeper zk;
    private String host;
 
    public ZookeeperExample(String host) {
        this.host = host;
    }
 
    @Override
    public void process(WatchedEvent event) {
        if (event.getType() == EventType.None) {
            if (event.getState() == Event.KeeperState.SyncConnected) {
                System.out.println("Connected to " + host);
            }
        }
    }
 
    void startZK() throws Exception {
        zk = new ZooKeeper(host, SESSION_TIMEOUT, this);
    }
 
    void createNode(String path, String data) throws Exception {
        String result = zk.create(path, data.getBytes(), Ids.OPEN_ACL_UNSAFE,
                CreateMode.PERSISTENT);
        System.out.println("Created node: " + result);
    }
 
    void readNode(String path) throws Exception {
        byte[] data = zk.getData(path, true, null);
        System.out.println("Node " + path + " value: " + new String(data));
    }
 
    void watchNode(String path) throws Exception {
        zk.exists(path, true);
        System.out.println("Watching node: " + path);
    }
 
    void changeNode(String path, String data) throws Exception {
        zk.setData(path, data.getBytes(), -1);
        System.out.println("Changed node: " + path + " value: " + data);
    }
 
    public static void main(String[] args) throws Exception {
        ZookeeperExample example = new ZookeeperExample(CONNECT_STRING);
        example.startZK();
 
        String path = "/myapp";
        String data = "Hello, Zookeeper!";
 
        // 创建节点
        example.createNode(path, data);
 
        // 读取并监听节点数据的变化
        example.watchNode(path);
 
        // 修改节点数据
        example.changeNode(path, "Hello, Zookeeper! Updated!");
    }
}

在这个例子中，我们首先创建了一个与Zookeeper服务