class DFSClientCache {

  UserGroupInformation getUserGroupInformation(
          String effectiveUser,
          UserGroupInformation realUser)
          throws IOException {
    Preconditions.checkNotNull(effectiveUser);
    Preconditions.checkNotNull(realUser);
    realUser.checkTGTAndReloginFromKeytab();

    UserGroupInformation ugi =
            UserGroupInformation.createProxyUser(effectiveUser, realUser);
    if (LOG.isDebugEnabled()){
      LOG.debug(String.format("Created ugi:" +
              " %s for username: %s", ugi, effectiveUser));
    }
    return ugi;
  }

    DFSClientCache(NfsConfiguration config);
    DFSClientCache(NfsConfiguration config, int clientCache);

}