package cn.com.toto.zkonlineoroffline;

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 DistributedClient {

    private static final String connectString = "192.168.106.80:2181,192.168.106.81:2181,192.168.106.82:2181";

    private static final int sessionTimeout = 2000;

     private static final String parentNode = "/servers";

     // 注意:加volatile的意義何在？

     private volatile List<String> serverList;

     private ZooKeeper zk = null;

     /**

      * 建立到zk的客戶端連線

      *

      * @throws Exception

      */

     public void getConnect() throws Exception {

         zk = new ZooKeeper(connectString, sessionTimeout, new Watcher() {

              @Override

              public void process(WatchedEvent event) {

                   // 收到事件通知後的回撥函式（應該是我們自己的事件處理邏輯）

                   try {

                       //重新更新伺服器列表，並且註冊了監聽

                       getServerList();

                   } catch (Exception e) {

                   }

              }

         });

     }

     /**

      * 獲取伺服器資訊列表

      *

      * @throws Exception

      */

     public void getServerList() throws Exception {

         // 獲取伺服器子節點資訊，並且對父節點進行監聽

         List<String> children = zk.getChildren(parentNode, true);

         // 先建立一個區域性的list來存伺服器資訊

         List<String> servers = new ArrayList<String>();

         for (String child : children) {

              // child只是子節點的節點名

              byte[] data = zk.getData(parentNode + "/" + child, false, null);

              servers.add(new String(data));

         }

         // 把servers賦值給成員變數serverList，已提供給各業務執行緒使用

         serverList = servers;

         //列印伺服器列表

         System.out.println(serverList);

     }

     /**

      * 業務功能

      *

      * @throws InterruptedException

      */

     public void handleBussiness() throws InterruptedException {

         System.out.println("client start working.....");

         Thread.sleep(Long.MAX_VALUE);

     }

     public static void main(String[] args) throws Exception {

         // 獲取zk連線

         DistributedClient client = new DistributedClient();

         client.getConnect();

         // 獲取servers的子節點資訊（並監聽），從中獲取伺服器資訊列表

         client.getServerList();

         // 業務執行緒啟動

         client.handleBussiness();

     }

}

package cn.com.toto.zkonlineoroffline;

import java.util.concurrent.CountDownLatch;

import org.apache.zookeeper.CreateMode;

import org.apache.zookeeper.WatchedEvent;

import org.apache.zookeeper.Watcher;

import org.apache.zookeeper.ZooKeeper;

import org.apache.zookeeper.Watcher.Event.KeeperState;

import org.apache.zookeeper.ZooDefs.Ids;

import org.apache.zookeeper.data.Stat;

public class DistributedServer {

     private static final String CONNECT_STRING = "192.168.106.80:2181,192.168.106.81:2181,192.168.106.82:2181";

     private static final int SESSION_TIME_OUT = 2000;

     private static final String PARENT_NODE = "/servers";

     private ZooKeeper zk = null;

     CountDownLatch countDownLatch = new CountDownLatch(1);

     /**

      * 建立到zk的客戶端連線

      *

      * @throws Exception

      */

     public void getConnect() throws Exception {

         zk = new ZooKeeper(CONNECT_STRING, SESSION_TIME_OUT, new Watcher() {

              @Override

              public void process(WatchedEvent event) {

                   if(event.getState()==KeeperState.SyncConnected){

                       countDownLatch.countDown();

                   }

              }

         });

         countDownLatch.await();

     }

     /**

      * 向zk叢集註冊伺服器資訊

      *

      * @param hostname

      * @throws Exception

      */

     public void registerServer(String hostname) throws Exception {

         Stat exists = zk.exists(PARENT_NODE, false);

         if(exists==null) zk.create(PARENT_NODE, null, Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT);

         String path = zk.create(PARENT_NODE + "/server", hostname.getBytes(), Ids.OPEN_ACL_UNSAFE, CreateMode.EPHEMERAL_SEQUENTIAL);

         System.out.println(hostname + "is online.." + path);

     }

     /**

      * 業務功能

      *

      * @throws InterruptedException

      */

     public void handleBussiness(String hostname) throws InterruptedException {

         System.out.println(hostname + "start working.....");

         Thread.sleep(Long.MAX_VALUE);

     }

     public static void main(String[] args) throws Exception {

         DistributedServer server = new DistributedServer();

         // 獲取zk連線

         server.getConnect();

         // 利用zk連線註冊伺服器資訊(主機名)

         server.registerServer(args[0]);

         // 啟動業務功能

         server.handleBussiness(args[0]);

     }

}