@Override
  public JSONObject getSnapshot() {
    JSONObject snapshot = new JSONObject();
    snapshot.put(DATA_NODE_HOSTNAME, getHostname());
    snapshot.put(DATA_NODE_DATACENTER, getDatacenterName());
    snapshot.put(DATA_NODE_XID, getXid());
    snapshot.put(LIVENESS, getLiveness());
    return snapshot;
  }
@return a port with number {@link #UNKNOWN_PORT}, since CloudServiceDataNode cannot be connected to via a socket.
ambry-clustermap/src/main/java/com/github/ambry/clustermap/CloudServiceDataNode.java