public function resume($crawler_id)
  {
    if ($this->resumtion_enabled == false)
      throw new Exception("Resumption was not enalbled, call enableResumption() before calling the resume()-method!");
    
    // Adobt crawler-id
    $this->crawler_uniqid = $crawler_id;
    
    if (!file_exists($this->working_base_directory."phpcrawl_tmp_".$this->crawler_uniqid.DIRECTORY_SEPARATOR))
    {
      throw new Exception("Couldn't find any previous aborted crawling-process with crawler-id '".$this->crawler_uniqid."'");
    }
    
    $this->createWorkingDirectory();
    
    // Unlinks pids file in working-dir (because all PIDs will change in new process)
    if (file_exists($this->working_directory."pids")) unlink($this->working_directory."pids");
  }