Zookeeper3.8.3 java client示例

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前言

在当今微服务架构和分布式系统快速发展的背景下，系统组件之间的协调与管理变得尤为重要。随着服务规模的扩大，节点之间的信息同步、主从选举、配置管理以及任务调度等问题逐渐浮现，传统的单体系统难以胜任这些复杂的协调任务。为了解决这一难题，Apache 推出了一个高性能、高可用的分布式协调框架 —— Zookeeper。

Zookeeper 提供了一个强一致性的分布式协调服务，它通过简单的数据模型和 Watch 机制，帮助开发者在复杂的分布式环境中轻松实现服务注册与发现、主从选举、分布式锁等关键功能。它广泛应用于 Hadoop、Kafka、HBase 等大型系统中，成为构建可靠、高可用分布式系统的基石。

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一、Zookeeper是什么？

Zookeeper 是一个由 Apache 提供的 分布式协调服务，主要用于管理分布式系统中的配置信息、命名服务、同步服务和集群管理等。

二、使用步骤

1.引入依赖

  <dependency>
       <groupId>org.apache.zookeeper</groupId>
       <artifactId>zookeeper</artifactId>
       <version>3.8.3</version>
   </dependency>

2.创建连接

    static ZooKeeper init() throws Exception {
        CountDownLatch countDownLatch = new CountDownLatch(1);
        ZooKeeper zooKeeper = new ZooKeeper("192.168.4.64:2181", 60000, watchedEvent -> {
            if (Watcher.Event.KeeperState.SyncConnected == watchedEvent.getState()) {
                countDownLatch.countDown();
            }
        });
        System.out.println(zooKeeper.getState());
        countDownLatch.await();
        System.out.println(zooKeeper.getState());
        return zooKeeper ;
    }

3.创建节点

    @Test
    public void create() throws Exception {
        //同步创建
        String path = zooKeeper.create(ZK_NODE, "dataSync".getBytes(), ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT);
        log.info("created path: {}",path);
    }

4.删除节点

    @Test
    public void delete() throws Exception {
        Stat stat = zooKeeper.exists(ZK_NODE, false);
        if (stat != null) {
            zooKeeper.delete(ZK_NODE, stat.getVersion());
            log.info("节点删除成功");
        } else {
            log.info("节点不存在");
        }
    }

5.修改节点

    @Test
    public void update() throws Exception {
        Stat stat = new Stat();
        byte[] data = zooKeeper.getData(ZK_NODE, false, stat);
        log.info("修改前: {}",new String(data));
        zooKeeper.setData(ZK_NODE, "changed!".getBytes(), stat.getVersion());
        byte[] dataAfter = zooKeeper.getData(ZK_NODE, false, stat);
        log.info("修改后: {}",new String(dataAfter));
    }

6.查询节点

    @Test
    public void query() throws Exception {
        List<String> children = zooKeeper.getChildren("/config", true);
        log.info("{}",children);
        Stat stat = new Stat();
        byte[] data = zooKeeper.getData(ZK_NODE, true, stat);
        log.info("data : {}",new String(data));
    }

三、完整示例

@Slf4j
public class ZkClientTest {

    private static final String ZK_NODE = "/test";
    private static ZooKeeper zooKeeper;

    @BeforeAll
    static void init() throws Exception {
        CountDownLatch countDownLatch = new CountDownLatch(1);
        zooKeeper = new ZooKeeper("192.168.4.64:2181", 60000, watchedEvent -> {
            if (Watcher.Event.KeeperState.SyncConnected == watchedEvent.getState()) {
                countDownLatch.countDown();
            }
        });
        System.out.println(zooKeeper.getState());
        countDownLatch.await();
        System.out.println(zooKeeper.getState());
    }

    @AfterAll
    static void end() throws InterruptedException {
        zooKeeper.close();
    }

    @Test
    public void create() throws Exception {
        //同步创建
        String path = zooKeeper.create(ZK_NODE, "dataSync".getBytes(), ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT);
        log.info("created path: {}",path);
    }

    @Test
    public void delete() throws Exception {
        Stat stat = zooKeeper.exists(ZK_NODE, false);
        if (stat != null) {
            zooKeeper.delete(ZK_NODE, stat.getVersion());
            log.info("节点删除成功");
        } else {
            log.info("节点不存在");
        }
    }

    @Test
    public void update() throws Exception {
        Stat stat = new Stat();
        byte[] data = zooKeeper.getData(ZK_NODE, false, stat);
        log.info("修改前: {}",new String(data));
        zooKeeper.setData(ZK_NODE, "changed!".getBytes(), stat.getVersion());
        byte[] dataAfter = zooKeeper.getData(ZK_NODE, false, stat);
        log.info("修改后: {}",new String(dataAfter));
    }

    @Test
    public void query() throws Exception {
        List<String> children = zooKeeper.getChildren("/config", true);
        log.info("{}",children);
        Stat stat = new Stat();
        byte[] data = zooKeeper.getData(ZK_NODE, true, stat);
        log.info("data : {}",new String(data));
    }

    @Test
    public void createAsync() throws Exception {
        //异步创建
        zooKeeper.create(ZK_NODE, "dataAsync".getBytes(), ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT,
                (rc, path, ctx, name) -> log.info("rc  {},path {},ctx {},name {}",rc,path,ctx,name),"context");
        TimeUnit.SECONDS.sleep(5);
    }

}

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总结

Zookeeper 是一个为分布式系统提供协调、同步、命名、配置管理的“调度大脑”。