You can add code to be run with the `request`,  before any *path operation* receives it.

And also after the `response` is generated, before returning it.

For example, you could add a custom header `X-Process-Time` containing the time in seconds that it took to process the request and generate a response:

{* ../../docs_src/middleware/tutorial001.py hl[10,12:13] *}

/// tip

errors.app.db.already.deleted = It may have been deleted by another process. Please try again.
errors.app.db.already.updated = It may have been updated by another process. Please try again.
errors.app.db.already.exists = The data already exists. Please try again.
errors.app.double.submit.request = It may have been processed before this request. Please try again.

errors.app.db.already.deleted = It may have been deleted by another process. Please try again.
errors.app.db.already.updated = It may have been updated by another process. Please try again.
errors.app.db.already.exists = The data already exists. Please try again.
errors.app.double.submit.request = It may have been processed before this request. Please try again.

      }
      readControlFrame()
    }
  }

  /**
   * Reads a message body into across one or more frames. Control frames that occur between
   * fragments will be processed. If the message payload is masked this will unmask as it's being
   * processed.
   */
  @Throws(IOException::class)
  private fun readMessage() {
    while (true) {
      if (closed) throw IOException("closed")

      if (frameLength > 0L) {

                            true);

            final int totalCount = process(options);
            if (totalCount != 0) {
                logger.info("Processed {} thumbnail task(s).", totalCount);
            } else {
                logger.info("No new thumbnails found.");
            }
            exitCode = 0;

        } catch (JobProcessingException e) {
            assertTrue(e.getMessage().contains("10 crawler processes are running"));
            assertTrue(e.getMessage().contains("Max processes are 5"));
        }
    }

    // Test execute method with no max process limit
    public void test_execute_noMaxProcessLimit() {
        // Setup test
        crawlJob = new CrawlJob() {

                failureUrlService.delete(entity);
                saveInfo(messages -> messages.addSuccessCrudDeleteCrudTable(GLOBAL));
            } catch (final Exception e) {
                logger.warn("Failed to process a request.", e);
                throwValidationErrorApi(messages -> messages.addErrorsCrudFailedToDeleteCrudTable(GLOBAL, buildThrowableMessage(e)));
            }
        }).orElse(() -> {

                crawlingInfoService.delete(entity);
                saveInfo(messages -> messages.addSuccessCrudDeleteCrudTable(GLOBAL));
            } catch (final Exception e) {
                logger.warn("Failed to process a request.", e);
                throwValidationErrorApi(messages -> messages.addErrorsCrudFailedToDeleteCrudTable(GLOBAL, buildThrowableMessage(e)));
            }
        }).orElse(() -> {

* Processing data:
    * For example, let's say you receive a file that must go through a slow process, you can return a response of "Accepted" (HTTP 202) and process the file in the background.

## Using `BackgroundTasks` { #using-backgroundtasks }

            }
            final CorsHandlerFactory factory = ComponentUtil.getCorsHandlerFactory();
            final CorsHandler handler = factory.get(origin);
            if (handler != null) {
                handler.process(origin, request, response);

                if (OPTIONS.equals(httpRequest.getMethod())) {
                    final HttpServletResponse httpResponse = (HttpServletResponse) response;