docs: @Override
      public DirectoryServiceClient getDirectoryServiceClient(){
          if(client == null){
              synchronized(this){
                  if(isShutdown){
                      ServiceDirectoryError error = new ServiceDirectoryError(ErrorCode.SERVICE_DIRECTORY_IS_SHUTDOWN);
                      throw new ServiceException(error);
                  }
                  if(client == null){
                      try {
                          String host = ServiceDirectory.getServiceDirectoryConfig().getString(
                                  DirectoryServiceClient.SD_API_SD_SERVER_FQDN_PROPERTY,
                                  DirectoryServiceClient.SD_API_SD_SERVER_FQDN_DEFAULT);
                          int port = ServiceDirectory.getServiceDirectoryConfig().getInt(
                                  DirectoryServiceClient.SD_API_SD_SERVER_PORT_PROPERTY,
                                  DirectoryServiceClient.SD_API_SD_SERVER_PORT_DEFAULT);
  
                          List<String> ss = new ArrayList<String>();
                          ss.add(host + ":" + port);
                          client = new DirectoryServiceClient(ss, "admin", "admin");
                      } catch (Exception e) {
                          // TODO Auto-generated catch block
                          e.printStackTrace();
                      }
                  }
              }
          }
          return client;
      }