/**
     * Drains all events from the buffer and returns them as a list.
     *
     * @return a list of all buffered events
     */
    public List<LogNotificationEvent> drainAll() {
        final List<LogNotificationEvent> events = new ArrayList<>();
        LogNotificationEvent event;
        while ((event = queue.poll()) != null) {
            events.add(event);
            size.decrementAndGet();
        }

        LogNotificationHelper helper = new LogNotificationHelper();
        helper.offer(new LogNotificationEvent(1000L, "ERROR", "com.example.Foo", "message1", "throwable1"));
        helper.offer(new LogNotificationEvent(2000L, "WARN", "com.example.Bar", "message2", null));

        List<LogNotificationEvent> events = helper.drainAll();
        assertEquals(2, events.size());

            for (int i = 0; i < events.size(); i += BATCH_SIZE) {
                final List<LogNotificationEvent> batch = events.subList(i, Math.min(i + BATCH_SIZE, events.size()));
                final BulkRequestBuilder bulkRequest = client.prepareBulk();
                for (final LogNotificationEvent event : batch) {
                    final Map<String, Object> source = new HashMap<>();

        assertEquals(0, events.size());
    }

    @Test
    public void test_append_nonExcludedLogger() {
        final LogEvent event = createLogEvent(Level.ERROR, "org.codelibs.fess.helper.SystemHelper", "not excluded");
        appender.append(event);

        final List<LogNotificationEvent> events = ComponentUtil.getLogNotificationHelper().drainAll();

        long base = 1700000000000L;
        List<LogNotificationEvent> events = new ArrayList<>();
        events.add(new LogNotificationEvent(base, "ERROR", "org.test.A", "first", null));
        events.add(new LogNotificationEvent(base + 1000, "WARN", "org.test.B", "second", null));
        events.add(new LogNotificationEvent(base + 2000, "ERROR", "org.test.C", "third", null));

        // Add events to buffer
        ComponentUtil.getLogNotificationHelper()
                .offer(new LogNotificationEvent(System.currentTimeMillis(), "ERROR", "org.test", "msg1", null));
        ComponentUtil.getLogNotificationHelper()
                .offer(new LogNotificationEvent(System.currentTimeMillis(), "WARN", "org.test", "msg2", null));

        final Map<String, List<LogNotificationEvent>> eventsByLevel =
                events.stream().collect(Collectors.groupingBy(LogNotificationEvent::getLevel));

        for (final Map.Entry<String, List<LogNotificationEvent>> entry : eventsByLevel.entrySet()) {
            final String level = entry.getKey();
            final List<LogNotificationEvent> levelEvents = entry.getValue();

            if (throwableStr.length() > MAX_THROWABLE_LENGTH) {
                throwableStr = throwableStr.substring(0, MAX_THROWABLE_LENGTH);
            }
        }

        final LogNotificationEvent notificationEvent = new LogNotificationEvent( //
                event.getTimeMillis(), //
                event.getLevel().name(), //
                loggerName, //
                event.getMessage().getFormattedMessage(), //