private String generateUniqueIdentifer(DownloadRequest request) {
    String uuid = UUID.randomUUID().toString().replaceAll("-", "");
    String json = gson.toJson(request);
    writeToHdfs(uuid, json);
    return uuid;
  }
Generate link for concat
@param request download request
@return response wth request id
@see #concatByRequestId(String)
contrib/views/files/src/main/java/org/apache/ambari/view/filebrowser/DownloadService.java