（原）3.2 Zookeeper应用

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数据的发布与订阅

1、应用

　　服务端监听数据改变，客户端创建/更新节点数据，客户端提供数据，服务端处理

2、原理 

• 客户端监控节点数据改变事件（例如配置信息，下图的config节点），启动时在服务器节点下创建临时节点（图中servers下节点）
• 服务端监听工作服务器的子节点更新，触发自身存储的工作服务器列表，同时监听订阅节点的数据改变事件（下图中command节点）

3、架构图

• config：配置信息节点
• servers：服务器列表父节点
• command：数据订阅节点

4、客户端流程图

5、服务端流程图

 6、核心类关系图

• SubscribeClient：模拟服务端、客户端启动
• WorkServer：客户端
• ManageServer：服务端
• ServerConfig：配置信息
• ServerData：server数据

7、核心代码

• WorkServer 监听

  public WorkServer(String serverPath, String configPath, final ServerData serverData, ServerConfig serverConfig, ZkClient zkClient) {
          this.serverPath = serverPath;
          this.configPath = configPath;
          this.serverData = serverData;
          this.serverConfig = serverConfig;
          this.zkClient = zkClient;
  
          dataListener = new IZkDataListener() {
              @Override
              public void handleDataChange(String s, Object o)  {
  
                  try{
                      String data = new String((byte[])o);
                      System.out.println(data);
                      ServerConfig config = (ServerConfig)JSON.parseObject(data,ServerConfig.class);
                      updateConfig(config);
                      System.out.println("server name:"+serverData.getName()+" update config:"+config.toString());
                  }catch (Exception e) {
                      e.printStackTrace();
                  }
  
              }
  
              @Override
              public void handleDataDeleted(String s) throws Exception {
  
              }
          };
      }

• WorkServer 注册

  private void registerMe() {
          String myPath = serverPath.concat("/").concat(serverData.getAddress());
          try{
              if(!zkClient.exists(myPath))
                  zkClient.createEphemeral(myPath,JSON.toJSONString(serverData).getBytes());
          }catch (ZkNoNodeException e ) {
              zkClient.createPersistent(serverPath, true);
              registerMe();
          }
      }

  ps：此操作是在servers节点下创建节点，需要servers节点已存在

• ManageServer 监听

   public ManageServer(String serverPath, String configPath, String cmdPath, ServerConfig serverConfig, ZkClient zkClient) {
          this.serverPath = serverPath;
          this.configPath = configPath;
          this.cmdPath = cmdPath;
          this.serverConfig = serverConfig;
          this.zkClient = zkClient;
  
          childListener = new IZkChildListener() {
              @Override
              public void handleChildChange(String s, List<String> strings) throws Exception {
                  workServerList = strings;
                  System.out.println("----"+workServerList.toString());
              }
          };
  
          dataListener = new IZkDataListener() {
              @Override
              public void handleDataChange(String s, Object o) throws Exception {
                  String cmd = new String((byte[])o);
                  System.out.println("cmd="+cmd);
                  exeCmd(cmd);
              }
  
              @Override
              public void handleDataDeleted(String s) throws Exception {
  
              }
          };
  
      }

  • childListener ：监听Servers下的节点变化

  • dataListener ：监听command节点的数据变化

• ManageServer 执行操作

  /**
       *模拟命令：1、list 2、create 3、modify
       */
      private void exeCmd(String cmd) {
          if("list".equals(cmd)) {
              System.out.println(workServerList.toString());
          }else if("create".equals(cmd)) {
              exeCreate();
          }else if("modify".equals(cmd)) {
              exeModify();
          }else {
              System.out.println("this cmd can not exe");
          }
  
      }

• SubscribeClient

  public class SubscribeClient {
      private static final int CLIENT_QTY =3;
      private static final String ZOOKEEPER_URL = "192.168.117.128:2181";
      private static final String SERVERPATH = "/servers";
      private static final String CONFIGPATH = "/config";
      private static final String CMDPATH = "/command";
  
      @Test
      public void testSubScribe() throws IOException {
          ServerConfig config = new ServerConfig("DBURL...","DBUSER...","DBPAW...");
          ZkClient zk = new ZkClient(ZOOKEEPER_URL,5000,5000,new BytesPushThroughSerializer());
          ManageServer manageServer = new ManageServer(SERVERPATH,CONFIGPATH,CMDPATH,config,zk);
          manageServer.start();
  
          for (int i = 0; i < CLIENT_QTY; i++) {
              ZkClient zkq = new ZkClient(ZOOKEEPER_URL,5000,5000,new BytesPushThroughSerializer());
              ServerData data = new ServerData("address"+i,i+"","name_"+i);
              WorkServer server = new WorkServer(SERVERPATH,CONFIGPATH,data,config,zkq);
              server.start();
          }
  
          new BufferedReader(new InputStreamReader(System.in)).readLine();
      }
  }