code: public static boolean isDefaultNamenodeAddress(Configuration conf,
        InetSocketAddress address, String... keys) {
      for (String key : keys) {
        String candidateAddress = conf.get(key);
        if (candidateAddress != null
            && address.equals(NetUtils.createSocketAddr(candidateAddress)))
          return true;
      }
      return false;
    }
docs: Given the InetSocketAddress for any configured communication with a
  namenode, this method determines whether it is the configured
  communication channel for the "default" namenode.
  It does a reverse lookup on the list of default communication parameters
  to see if the given address matches any of them.
  Since the process of resolving URIs to Addresses is slightly expensive,
  this utility method should not be used in performance-critical routines.
  
  @param conf - configuration
  @param address - InetSocketAddress for configured communication with NN.
  Configured addresses are typically given as URIs, but we may have to
  compare against a URI typed in by a human, or the server name may be
  aliased, so we compare unambiguous InetSocketAddresses instead of just
  comparing URI substrings.
  @param keys - list of configured communication parameters that should
  be checked for matches.  For example, to compare against RPC addresses,
  provide the list DFS_NAMENODE_SERVICE_RPC_ADDRESS_KEY,
  DFS_NAMENODE_RPC_ADDRESS_KEY
  @return - boolean confirmation if matched generic parameter