code: private String getQualifiedMetricName(String metricName) {
      try {
        if (SecurityUtils.isAuthenticationEnabled(mContext.getConf())
            && LoginUser.get(mContext.getConf()) != null) {
          return Metric.getMetricNameWithTags(metricName, CommonMetrics.TAG_USER,
              LoginUser.get(mContext.getConf()).getName());
        } else {
          return metricName;
        }
      } catch (IOException e) {
        return metricName;
      }
    }
docs: TODO(calvin): General tag logic should be in getMetricName