public function check_result($id)
  {
    if ( $d = $this->get($id) ){
      $t = new bbn\util\timer();
      $t->start();
      $res = $this->_exec($d['request'], $d['params']);
      $duration = (int)ceil($t->stop() * 1000);
      if ( $res !== $d['result'] ){
        $this->db->update('bbn_observers', [
          'result' => $res,
          'duration' => $duration
        ], [
          'id' => $id
        ]);
        return false;
      }
      return true;
    }
  }