伺服器動態上下線監聽案例

需求

某分散式系統中，主節點可以有多臺，可以動態上下線，任意一臺客戶端都能實時感知 到主節點伺服器的上下線。

需求分析

具體實現

• 先在叢集上建立/servers節點

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

• 在IDEA中建立包明：com.atguigu.case1

• 伺服器端向Zookeeper註冊程式碼

  packagecom.atguigu.case1;
  
  importorg.apache.zookeeper.*;
  
  importjava.io.IOException;
  
  /**
  *@author
   
  :fxl
  *@Description:
  *@Data:Createin2022-02-05
  *@ModifiedBy:
  */
  publicclassDistributeServer{
  privateStringconnectString="hadoop102:2181,hadoop103:2181,hadoop104:2181";
  privateintsessionTimeout=2000;
  privateZooKeeperzk;
  
  publicstaticvoidmain(String[]args)throwsIOException,InterruptedException,KeeperException{
  DistributeServerserver=new
   
  DistributeServer();
  //1.獲取zk連結
  server.getConnect();
  //2.註冊伺服器zk叢集
  server.regist(args[0]);
  //3.啟動業務邏輯（休眠）
  server.business();
  }
  
  privatevoidbusiness()throwsInterruptedException{
  Thread.sleep(Long.MAX_VALUE);
  }
  
  privatevoidregist(Stringhostname)throwsInterruptedException,KeeperException{
  Stringcreate=zk.create("/servers/"+hostname,hostname.getBytes(),ZooDefs.Ids.OPEN_ACL_UNSAFE,CreateMode.EPHEMERAL_SEQUENTIAL);
  System.out.println(hostname+"isonline"
   
  );
  }
  
  
  privatevoidgetConnect()throwsIOException{
  zk=newZooKeeper(connectString,sessionTimeout,newWatcher(){
  @Override
  publicvoidprocess(WatchedEventwatchedEvent){
  
  }
  });
  }
  }
  

• 客戶端程式碼

  packagecom.atguigu.case1;
  
  importorg.apache.zookeeper.KeeperException;
  importorg.apache.zookeeper.WatchedEvent;
  importorg.apache.zookeeper.Watcher;
  importorg.apache.zookeeper.ZooKeeper;
  
  importjava.io.IOException;
  importjava.util.ArrayList;
  importjava.util.List;
  
  /**
  *@author:fxl
  *@Description:
  *@Data:Createin2022-02-05
  *@ModifiedBy:
  */
  publicclassDistributeClient{
  privateStringconnectString="hadoop102:2181,hadoop103:2181,hadoop104:2181";
  privateintsessionTimeout=2000;
  privateZooKeeperzk;
  
  publicstaticvoidmain(String[]args)throwsIOException,InterruptedException,KeeperException{
  DistributeClientclient=newDistributeClient();
  //1.獲取zk連線
  client.getConnnect();
  //2.監聽/servers下面子節點的增加和刪除
  client.getServerList();
  //3.業務邏輯（休眠）
  client.business();
  }
  
  privatevoidbusiness()throwsInterruptedException{
  Thread.sleep(Long.MAX_VALUE);
  }
  
  privatevoidgetServerList()throwsInterruptedException,KeeperException{
  List<String>children=zk.getChildren("/servers",true);
  ArrayList<String>servers=newArrayList<>();
  for(Stringchild:children){
  byte[]data=zk.getData("/servers/"+child,false,null);
  servers.add(newString(data));
  }
  //列印
  System.out.println(servers);
  }
  
  privatevoidgetConnnect()throwsIOException{
  zk=newZooKeeper(connectString,sessionTimeout,newWatcher(){
  @Override
  publicvoidprocess(WatchedEventwatchedEvent){
  try{
  getServerList();
  }catch(Exceptione){
  e.printStackTrace();
  }
  }
  });
  }
  }
  

測試

• 在Linux命令列上操作增加減少伺服器

  • 啟動DistributeClient客戶端

    • 在hadoop102上zk客戶端/servers目錄上建立臨時帶序號節點

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

    • 觀察IDEA控制檯變化

      hadoop102, hadoop103]

    • 執行刪除操作

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

    • 觀察 Idea 控制檯變化

      [hadoop103]

• 在 Idea 上操作增加減少伺服器

  • 啟動DistributeClient客戶端（如果已經啟動過，不需要重啟）

  • 啟動 DistributeServer服務

    • ①點選 Edit Configurations

    • 在彈出的視窗中（Program arguments）輸入想啟動的主機，例如，hadoop102

    • 回到 DistributeServer 的 main 方 法 ， 右 鍵 ， 在 彈 出 的 窗 口 中 點 擊 Run “DistributeServer.main()”

    • 觀察 DistributeServer 控制檯，提示 hadoop102 is working

    • 觀察 DistributeClient控制檯，提示hadoop102 已經上線