Zookeeper服务器动态上下线监听案例

需求

某分布式系统中，主节点可以有多台，可以动态上下线，任意一台客户端都能实时感知到主节点服务器的上下线。

需求分析

具体实现

（1）先在集群上创建/servers 节点

（2）在 Idea 中创建包名：com.gk.case1

（3）服务器端向 Zookeeper 注册代码

package com.gk.case1; import org.apache.zookeeper.*; import java.io.IOException; /** * create with IntelliJ IDEA * * @Project :zookeeper * @Package :com.gk.case1 * @ClassName : * @CreateTime :2022/4/128:53 * @Version :1.0 * @Author :锦林 * @Email :836658031@qq.com **/ public class DistributeServer { private String connectString = "hadoop102:2181,hadoop103:2181,hadoop104:2181"; private int sessionTimeout = 2000; private ZooKeeper zk = null; private String pareNode = "/servers"; // 创建到zk的客户端连接 public void getConnect() throws IOException { zk = new ZooKeeper(connectString, sessionTimeout, new Watcher() { public void process(WatchedEvent watchedEvent) { } }); } // 注册服务器 public void registerServer(String hostname) throws KeeperException, InterruptedException { String create = zk.create(pareNode + "/server", hostname.getBytes(), ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.EPHEMERAL_SEQUENTIAL); System.out.println(hostname + " is online " + create); } // 业务功能 public void business(String hostname) throws InterruptedException { System.out.println(hostname + " is working ..."); Thread.sleep(Long.MAX_VALUE); } public static void main(String[] args) throws Exception { // 1 获取zk连接 DistributeServer server = new DistributeServer(); server.getConnect(); // 2 利用zk连接注册服务器信息 server.registerServer(args[0]); // 3 启动业务功能 server.business(args[0]); } }

（4）客户端代码

package com.gk.case1; import org.apache.zookeeper.KeeperException; import org.apache.zookeeper.WatchedEvent; import org.apache.zookeeper.Watcher; import org.apache.zookeeper.ZooKeeper; import java.io.IOException; import java.util.ArrayList; import java.util.List; /** * create with IntelliJ IDEA * * @Project :zookeeper * @Package :com.gk.case1 * @ClassName : * @CreateTime :2022/4/129:04 * @Version :1.0 * @Author :锦林 * @Email :836658031@qq.com **/ public class DistributeClient { private String connectString = "hadoop102:2181,hadoop103:2181,hadoop104:2181"; private int sessionTimeout = 2000; private ZooKeeper zk = null; private String parentNode = "/servers"; // 创建到zk的客户端连接 public void getConnect() throws IOException { zk = new ZooKeeper(connectString, sessionTimeout, new Watcher() { public void process(WatchedEvent watchedEvent) { try { getServerList(); } catch (KeeperException e) { e.printStackTrace(); } catch (InterruptedException e) { e.printStackTrace(); } } }); } // 获取服务器列表信息 public void getServerList() throws KeeperException, InterruptedException { // 1 获取服务器节点信息，并且对父节点进行监听 List<String> children = zk.getChildren(parentNode, true); // 2 存储服务器信息列表 ArrayList<String> servers = new ArrayList<String>(); // 3 遍历所有节点，获取节点中的主机名称信息 for (String child : children) { byte[] data = zk.getData(parentNode + "/" + child, false, null); servers.add(new String(data)); } // 4 打印服务器列表信息 System.out.println(servers); } // 业务功能 public void business() throws Exception { System.out.println("client is working ..."); Thread.sleep(Long.MAX_VALUE); } public static void main(String[] args) throws Exception { // 1 获取zk连接 DistributeClient client = new DistributeClient(); client.getConnect(); // 2 获取servers的子节点信息，从中获取服务器信息列表 client.getServerList(); // 3 业务进程启动 client.business(); } }