@Override
      public void onDataNodeDelete(String instanceName) {
        clusterChangeHandler.onDataNodeDelete(instanceName);
      }
Register for data node configs from Helix Property store.
@param dcName data center for which we are interested in data node configs.
ambry-clustermap/src/main/java/com/github/ambry/clustermap/HelixAggregatedViewClusterInitializer.java