code: public void submitHadoopDownloadTask(String URL, String id) {
          Callable<ImageDownloadResult> call = new HadoopImageDownload(URL, id, followRedirects);
          pool.submit(call);
          numPendingTasks++;
      }
docs: Submits a new hadoop image download task.
  
  @param URL
  The url of the image
  @param id
  The id of the image (used to name the image file after download)