@Override
  public String getHostname() {
    return hostName;
  }
Instantiate an AmbryDataNode object.
@param dataCenterName the name of the dataCenter associated with this data node.
@param clusterMapConfig the {@link ClusterMapConfig} to use.
@param hostName the hostName identifying this data node.
@param plaintextPortNum the plaintext port identifying this data node. This can be
       {@link DataNodeId#UNKNOWN_PORT} if this object represents an in-process entity without a real TCP
       port.
@param sslPortNum the ssl port associated with this data node (may be null).
@param http2PortNum the http2 ssl port associated with this data node (may be null).
@throws Exception if there is an exception in instantiating the {@link ResourceStatePolicy}
ambry-clustermap/src/main/java/com/github/ambry/clustermap/AmbryDataNode.java