response.flushBuffer();
            if (logger.isDebugEnabled()) {
                logger.debug("Loaded {} docs", count);
            }
        } catch (final InvalidQueryException | ResultOffsetExceededException e) {
            if (logger.isDebugEnabled()) {
                logger.debug("Failed to process a scroll request.", e);
            }
            writeJsonResponse(HttpServletResponse.SC_BAD_REQUEST, e);

                System.getProperties().entrySet().stream().forEach(e -> logger.debug("Property: {}={}", e.getKey(), e.getValue()));
                System.getenv().entrySet().forEach(e -> logger.debug("Env: {}={}", e.getKey(), e.getValue()));
                logger.debug("Option: {}", options);
            } catch (final Exception e) {

                System.getProperties().entrySet().stream().forEach(e -> logger.debug("Property: {}={}", e.getKey(), e.getValue()));
                System.getenv().entrySet().forEach(e -> logger.debug("Env: {}={}", e.getKey(), e.getValue()));
                logger.debug("Option: {}", options);
            } catch (final Exception e) {

                            if (logger.isDebugEnabled()) {
                                logger.debug("generator path: {}", filePath);
                            }
                            return filePath;
                        }
                    }
                }
                if (logger.isDebugEnabled()) {
                    logger.debug("generator path: {}", s);
                }
                return s;

            logger.debug("process authentication: url: {}, params: {}", urlBuf, params);
        }

        // validate that state in response equals to state in request
        final StateData stateData = validateState(request.getSession(), params.containsKey(STATE) ? params.get(STATE).get(0) : null);
        if (logger.isDebugEnabled()) {
            logger.debug("load {}", stateData);
        }

                    if (logger.isDebugEnabled()) {
                        logger.debug("Token refreshed successfully via silent authentication");
                    }
                    return true;
                }
            } catch (final Exception e) {
                if (logger.isDebugEnabled()) {
                    logger.debug("Silent token refresh failed: {}", e.getMessage());
                }
            }

    public boolean generate(final String thumbnailId, final File outputFile) {
        if (logger.isDebugEnabled()) {
            logger.debug("Generate Thumbnail: {}", thumbnailId);
        }

        if (outputFile.exists()) {
            if (logger.isDebugEnabled()) {
                logger.debug("The thumbnail file exists: {}", outputFile.getAbsolutePath());
            }
            return true;
        }

                System.getProperties().entrySet().stream().forEach(e -> logger.debug("Property: {}={}", e.getKey(), e.getValue()));
                System.getenv().entrySet().forEach(e -> logger.debug("Env: {}={}", e.getKey(), e.getValue()));
                logger.debug("Option: {}", options);
            } catch (final Exception e) {

                    .get(stream -> stream.map(String::trim).filter(StringUtil::isNotBlank).collect(Collectors.toUnmodifiableSet()));
        }
        if (logger.isDebugEnabled()) {
            logger.debug("availableSearcherNameSet={}", availableSearcherNameSet);
        }
    }

    @Override
    @PreDestroy
    public void close() throws Exception {
        if (executorService != null) {
            try {

        // do nothing
    }

    /**
     * Initializes the helper.
     */
    @PostConstruct
    public void init() {
        if (logger.isDebugEnabled()) {
            logger.debug("Initialize {}", this.getClass().getSimpleName());
        }
        final FessConfig fessConfig = ComponentUtil.getFessConfig();
        langFields = fessConfig.getIndexerLanguageFieldsAsArray();