code: public void run() {
          for (final GatewayServer server : this.serverData.getServers()) {
              if (!server.isExist()) {
                  continue;
              }
  
              Runnable handler = new Runnable() {
                  public void run() {
                      if (!server.isExist()) {
                          return;
                      }
  
                      final boolean result = server.ping();
                      server.setValid(result);
                      log.debug("[HealthCheck] Result {}", server);
                  }
              };
              this.threadPool.execute(handler);
          }
      }
docs: /*
  @see java.lang.Runnable#run()