code: private String getQualifiedMetricName(String metricName) {
      try {
        if (SecurityUtils.isAuthenticationEnabled(mConfiguration)
            && AuthenticatedClientUser.get(mConfiguration) != null) {
          return Metric.getMetricNameWithTags(metricName, CommonMetrics.TAG_USER,
              AuthenticatedClientUser.get(mConfiguration).getName(), WorkerMetrics.TAG_UFS,
              MetricsSystem.escape(new AlluxioURI(mPath)), WorkerMetrics.TAG_UFS_TYPE,
              mUnderFileSystem.getUnderFSType());
        }
      } catch (IOException e) {
        // fall through
      }
      return Metric.getMetricNameWithTags(metricName, WorkerMetrics.TAG_UFS,
          MetricsSystem.escape(new AlluxioURI(mPath)), WorkerMetrics.TAG_UFS_TYPE,
          mUnderFileSystem.getUnderFSType());
    }
docs: TODO(calvin): General tag logic should be in getMetricName