Zookeeper监听服务器节点动态上下线超详细案例

监听服务器节点动态上下线案例

1. 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
2. 需求分析
   
3. 具体实现
   先在集群上创建/servers节点

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

服务器端向Zookeeper注册代码

import java.io.IOException;
import org.apache.zookeeper.CreateMode;
import org.apache.zookeeper.WatchedEvent;
import org.apache.zookeeper.Watcher;
import org.apache.zookeeper.ZooKeeper;
import org.apache.zookeeper.ZooDefs.Ids;
public class DistributeServer {
	private static String connectString = "hadoop102:2181,hadoop103:2181,hadoop104:2181";
	private static 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() {
			@Override
			public void process(WatchedEvent event) {
			}
		});
	}
	
	// 注册服务器
	public void registServer(String hostname) throws Exception{
		String create = zk.create(parentNode + "/server", hostname.getBytes(), Ids.OPEN_ACL_UNSAFE, CreateMode.EPHEMERAL_SEQUENTIAL);
		System.out.println(hostname +" is online "+ create);
	}

	// 业务功能
	public void business(String hostname) throws Exception{
		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.registServer(args[0]);
		// 3 启动业务功能
		server.business(args[0]);
	}
}

客户端代码

import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import org.apache.zookeeper.WatchedEvent;
import org.apache.zookeeper.Watcher;
import org.apache.zookeeper.ZooKeeper;
public class DistributeClient {
	private static String connectString = "hadoop102:2181,hadoop103:2181,hadoop104:2181";
	private static 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() {
			@Override
			public void process(WatchedEvent event) {
				// 再次启动监听
				try {
					getServerList();
				} catch (Exception e) {
					e.printStackTrace();
				}
			}
		});
	}

	// 获取服务器列表信息
	public void getServerList() throws Exception {
		// 1获取服务器子节点信息，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<>();
        // 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();
	}
}

简书：https://www.jianshu.com/u/0278602aea1d
CSDN：https://blog.csdn.net/u012387141