code: @Override
      public void stop() {
          if(enabled) {
              metricPublishing.stop();
          }
          if(startUpMetric != null) {
              startUpMetric.stop();
          }
          super.stop();
      }
docs: Stops the appender, shutting down the background polling thread to ensure that the connection to the metrics
  database is closed. This method also stops the heartbeat method background thread.