@Override
  public Set<Resource> populateResourcesWithProperties(Set<Resource> resources,
            Request request, Set<String> propertyIds) throws SystemException {

    Map<String, Map<TemporalInfo, RRDRequest>> requestMap = getRRDRequests(resources, request, propertyIds);

    // For each cluster...
    for (Map.Entry<String, Map<TemporalInfo, RRDRequest>> clusterEntry : requestMap.entrySet()) {
      // For each request ...
      for (RRDRequest rrdRequest : clusterEntry.getValue().values() ) {
        //todo: property provider can reduce set of resources
        rrdRequest.populateResources();
      }
    }
    return resources;
  }
Map of Ganglia cluster names keyed by component type.
ambari-server/src/main/java/org/apache/ambari/server/controller/metrics/ganglia/GangliaPropertyProvider.java