@Override
  public HelixClusterManager getClusterMap() throws IOException {
    if (helixClusterManager == null) {
      helixClusterManager = new HelixClusterManager(clusterMapConfig, instanceName, helixFactory, metricRegistry);
    }
    return helixClusterManager;
  }
Ctor exposed for testing purpose
@param clusterMapConfig the {@link ClusterMapConfig} to specify cluster configuration parameters.
@param helixFactory the {@link HelixFactory} that helps get reference of HelixManager and HelixAdmin.
ambry-clustermap/src/main/java/com/github/ambry/clustermap/HelixClusterAgentsFactory.java