}

    private static final Logger logger = LogManager.getLogger(SearchEngineClient.class);

    private static final String DOC_INDEX = "fess";

    private static final String LOG_INDEX_PREFIX = "fess_log";

    private static final String USER_INDEX_PREFIX = "fess_user";

    private static final String CONFIG_INDEX_PREFIX = "fess_config";

    /** OpenSearch runner for managing the embedded search engine */