public void putPropertyId(String metric, String id) {
      Set<String> propertyIds = metrics.get(metric);

      if (propertyIds == null) {
        propertyIds = new HashSet<>();
        metrics.put(metric, propertyIds);
      }
      propertyIds.add(id);
    }
The information required to make a single RRD request.
ambari-server/src/main/java/org/apache/ambari/server/controller/metrics/ganglia/GangliaPropertyProvider.java