Hadoop基础（三十六）：监听服务器节点动态上下线案例

package com.atguigu.zkclient;

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 final String CONNECTION_STRING = "192.168.1.122:2181,192.168.1.133:2181,192.168.1.144:2128";
    private static final int SESSION_TIMEOUT = 300000;
    private ZooKeeper zk;
    private String parentNode = "/servers";

    // 创建到 zk 的客户端连接
    public void getConnect() throws IOException {
        zk = new ZooKeeper(CONNECTION_STRING, SESSION_TIMEOUT, new Watcher() {
            public void process(WatchedEvent event){
                try {
                    getServerList();
                } catch (Exception e) {
                    //TODO: handle exception
                    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();
    }
}