return tempBuf.toString();
            }).collect(Collectors.joining(","));
            buf.append(hotThreads).append(',');
        } catch (final Exception e) {
            appendException(buf, e).append(',');
        }

        appendTimestamp(buf);
        buf.append('}');

        if (logger.isInfoEnabled()) {
            logger.info(buf.toString());
        }
    }

        append(buf, "timestamp", () -> FessFunctions.formatDate(systemHelper.getCurrentTime()));
        return buf;
    }

    protected StringBuilder appendException(final StringBuilder buf, final Exception exception) {
        try (ByteArrayOutputStream baos = new ByteArrayOutputStream();
                PrintWriter writer = new PrintWriter(baos, false, Constants.CHARSET_UTF_8)) {

            try (OutputStream out = builder.getOutputStream()) {
                stats = ((ByteArrayOutputStream) out).toString(Constants.UTF_8);
            }
        } catch (final Exception e) {
            appendException(buf, e).append(',');
        }
        buf.append("\"search_engine\":").append(stats).append(',');
    }