started.countDown();
                  try {
                    return method.invoke(delegate, args);
                  } catch (InvocationTargetException e) {
                    throw e.getCause();
                  } finally {
                    awaitUninterruptibly(canReturn);
                    returned.countDown();
                  }
                }
              });

            try (final InputStream is = new BufferedInputStream(responseData.getResponseBody())) {
                out.write(is);
            } catch (final IOException e) {
                if (!(e.getCause() instanceof ClientAbortException)) {
                    throw new FessSystemException("Failed to write a content. configId: " + configId + ", url: " + url, e);
                }
            } finally {