Zookeeper案例

1. 统一配置中心

在分布式集群系统中，经常要对某个配置信息进行修改，若一台一台对服务器进行修改，非常浪费时间，假如服务的体量非常大，几十台上百台甚至上千台服务器进行修改的话，几乎很不现实。zookeeper通过对节点数据进行监听，一旦配置信息发生变化，立马通知所有的客户端对数据进行重新读取。
下面通过Java代码的方式对统一配置中心进行简单的实现。

1.1 客户端

package cn.tianqb.zookeeper;

import org.apache.zookeeper.KeeperException;
import org.apache.zookeeper.ZooKeeper;

import java.util.concurrent.CountDownLatch;

/**
 * @Description: 客户端
 * @Author tianqb
 * @Mail tianqingbo@tianqb.cn
 * @Date 2020/5/21 20:26
 * @Version v1.0
 */
public class ZKClient {
   

    public ZooKeeper zooKeeper;
    public CountDownLatch countDownLatch = new CountDownLatch(1);
    // zookeeper服务器地址
    private String IP;
    // 会话超时时间
    private Integer SESSION_TIME_OUT;
    // url信息
    private String URL_PATH;
    // 用户名信息
    private String USER_PATH;
    // 密码信息
    private String PASSWD_PATH;

    public ZKClient(String IP, Integer SESSION_TIME_OUT, String URL_PATH, String USER_PATH, String PASSWD_PATH) {
   
        this.IP = IP;
        this.SESSION_TIME_OUT = SESSION_TIME_OUT;
        this.URL_PATH = URL_PATH;
        this.USER_PATH = USER_PATH;
        this.PASSWD_PATH = PASSWD_PATH;
        init();
    }

    /**
     * 连接至服务器
     */
    private void init() {
   

        ZKWatcher watcher = new ZKWatcher(countDownLatch, this);
        try {
   
            zooKeeper = new ZooKeeper(IP, SESSION_TIME_OUT, watcher);
            countDownLatch.await();
            pull();
        } catch (Exception e) {
   
            e.printStackTrace();
        }
    }

    public void close() {
   
        try {
   
            zooKeeper.close();
        } catch (InterruptedException e) {
   
            e.printStackTrace();
        }
    }

    /**
     * 接到通知重新拉取数据
     */
    public void pull() {
   
        
        ZKWatcher watcher = new ZKWatcher(countDownLatch, this);
        try {
   
            System.out.println("客户端" + zooKeeper.getSessionId() + "---url:" + new String(zooKeeper.getData(URL_PATH, watcher,
                    null)));
            System.out.println("客户端" + zooKeeper.getSessionId() + "---user:" + new String(zooKeeper.getData(USER_PATH, watcher,
                    null)));
            System.out.println("客户端" + zooKeeper.getSessionId() + "---passwd:" + new String(zooKeeper.getData(PASSWD_PATH, watcher,
                    null)));
        } catch (KeeperException e) {
   
            e.printStackTrace();
        } catch (InterruptedException e) {
   
            e.printStackTrace();
        }
    }
}

1.2 常量

package cn.tianqb.zookeeper;

/**
 * @Description: 常量
 * @Author tianqb
 * @Mail tianqingbo@tianqb.cn
 * @Date 2020/5/21 20:34
 * @Version v1.0
 */
public class ZKConstant {
   
    // zookeeper服务器地址
    public static final String IP = "192.168.100.1