code: private void handleGetAllMMetricsName(final HttpServletRequest req,
        final Map<String, Object> ret) {
      if (MetricReportManager.isAvailable()) {
        final MetricReportManager metricManager = MetricReportManager.getInstance();
        final List<IMetric<?>> result = metricManager.getAllMetrics();
        if (result.size() == 0) {
          ret.put(RESPONSE_ERROR, "No Metric being tracked");
        } else {
          final List<String> metricNames = new LinkedList<>();
          for (final IMetric<?> metric : result) {
            metricNames.add(metric.getName());
          }
          ret.put("data", metricNames);
        }
      } else {
        ret.put(RESPONSE_ERROR, "MetricReportManager is not available");
      }
    }
docs: Get all the metrics tracked by metric manager