@Override
    public List<String> identifyResources(HelixClusterManager helixClusterManager) {
      String dcName = helixClusterManager.clusterMapConfig.clusterMapDatacenterName;
      DataNodeId dataNodeId = helixClusterManager.instanceNameToAmbryDataNode.get(hostname);
      if (dataNodeId == null || !dataNodeId.getDatacenterName().equals(dcName)) {
        throw new IllegalArgumentException("Host " + hostname + " doesn't exist in this datacenter");
      }
      List<String> tags = helixClusterManager.instanceNameToInstanceConfig.get(hostname).getTags();
      return tags.stream()
          .map(tag -> helixClusterManager.dcToTagToResourceProperty.get(dataNodeId.getDatacenterName()).get(tag).name)
          .collect(Collectors.toList());
    }
Constructor to create a {@link HostnameIdentifier}.
@param hostname
ambry-clustermap/src/main/java/com/github/ambry/clustermap/HelixClusterManager.java