code: public static void slowLog(Logger logger, long duration, long threshold) {
  		if (duration > threshold) {
  			logger.warn("[Performance Warning]  use {}ms, slow than {}ms", duration, threshold);
  		}
  	}
docs: 当处理时间超过预定的阈值时发出警告信息
  @param logger
  @param key
  @param threshold 阈值（单位：ms）