目录

需求

 实现

1. 集群

2. 服务器

3.客户端

4. 测试

在 Linux 命令行上操作增加减少服务器

在 Idea 上操作增加减少服务器

 来源：

需求

 实现

1. 集群

[zk: localhost:2181(CONNECTED) 10] create /servers "servers"
Created /servers

2. 服务器

import org.apache.zookeeper.*;
import java.io.IOException;public class DistributeServer {private String connectString = "hadoop102:2181,hadoop103:2181,hadoop104:2181";private int sessionTimeout = 2000;private ZooKeeper zk;public static void main(String[] args) throws IOException, KeeperException, InterruptedException {DistributeServer server = new DistributeServer();// 1 获取zk连接server.getConnect();// 2 注册服务器到zk集群server.regist(args[0]);// 3 启动业务逻辑（睡觉）server.business();}private void business() throws InterruptedException {Thread.sleep(Long.MAX_VALUE);}private void regist(String hostname) throws KeeperException, InterruptedException {String create = zk.create("/servers/"+hostname, hostname.getBytes(), ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.EPHEMERAL_SEQUENTIAL);System.out.println(hostname +" is online") ;}private void getConnect() throws IOException {zk = new ZooKeeper(connectString, sessionTimeout, new Watcher() {@Overridepublic void process(WatchedEvent watchedEvent) {}});}
}

3.客户端

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;public class DistributeClient {private String connectString = "hadoop102:2181,hadoop103:2181,hadoop104:2181";private int sessionTimeout = 2000;private ZooKeeper zk;public static void main(String[] args) throws IOException, KeeperException, InterruptedException {DistributeClient client = new DistributeClient();// 1 获取zk连接client.getConnect();// 2 监听/servers下面子节点的增加和删除client.getServerList();// 3 业务逻辑（睡觉）client.business();}private void business() throws InterruptedException {Thread.sleep(Long.MAX_VALUE);}private void getServerList() throws KeeperException, InterruptedException {List children = zk.getChildren("/servers", true);ArrayList servers = new ArrayList<>();for (String child : children) {byte[] data = zk.getData("/servers/" + child, false, null);servers.add(new String(data));}// 打印System.out.println(servers);}private void getConnect() throws IOException {zk = new ZooKeeper(connectString, sessionTimeout, new Watcher() {@Overridepublic void process(WatchedEvent watchedEvent) {try {getServerList();} catch (KeeperException e) {e.printStackTrace();} catch (InterruptedException e) {e.printStackTrace();}}});}
}

4. 测试

在 Linux 命令行上操作增加减少服务器

[zk: localhost:2181(CONNECTED) 1] create -e -s 
/servers/hadoop102 "hadoop102"
[zk: localhost:2181(CONNECTED) 2] create -e -s 
/servers/hadoop103 "hadoop103"

[zk: localhost:2181(CONNECTED) 8] delete /servers/hadoop1020000000000

在 Idea 上操作增加减少服务器

 来源：

尚硅谷