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

}