throw new IllegalStateException("Unable to retrieve current key for rotation");
        }

        try {
            // Generate new key version
            int currentVersion = keyVersions.getOrDefault(sessionId, 0);
            int newVersion = currentVersion + 1;

            // Derive new key from current key
            String rotationLabel = String.format("KeyRotation-v%d", newVersion);

     *
     * @param handle notification handle
     * @return number of consecutive failures
     */
    private int getFailureCount(ChangeNotificationHandle handle) {
        return failureCounts.getOrDefault(handle.getDirectoryPath(), 0);
    }

    /**
     * Increment failure count for a handle
     *
     * @param handle notification handle
     */

     *
     * @param index the index configuration name
     */
    protected void sendConfigFiles(final String index) {
        final FessConfig fessConfig = ComponentUtil.getFessConfig();
        configListMap.getOrDefault(index, Collections.emptyList()).forEach(path -> {
            String source = null;
            final String filePath = indexConfigPath + "/" + index + "/" + path;
            final String dictionaryPath;