@GET
  @Path("/concat")
  @Consumes(MediaType.APPLICATION_JSON)
  @Produces(MediaType.APPLICATION_OCTET_STREAM)
  public Response concatByRequestId(@QueryParam("requestId") String requestId) {
    LOG.info("Starting concat for requestId : {}", requestId);
    try {
      DownloadRequest request = getDownloadRequest(requestId);
      return concat(request);
    } catch (WebApplicationException ex) {
      LOG.error("Error occurred : ", ex);
      throw ex;
    } catch (Exception ex) {
      LOG.error("Error occurred : ", ex);
      throw new ServiceFormattedException(ex.getMessage(), ex);
    }
  }
Concatenate files by unique link
@param requestId id of request
@return response with concatenated files
contrib/views/files/src/main/java/org/apache/ambari/view/filebrowser/DownloadService.java