/** The key of the configuration. e.g. 10 */
    String INDEX_DOCUMENT_CRAWLER_DATA_number_of_shards = "index.document.crawler.data.number_of_shards";

    /** The key of the configuration. e.g. 10 */
    String INDEX_DOCUMENT_CRAWLER_FILTER_number_of_shards = "index.document.crawler.filter.number_of_shards";

    /** The key of the configuration. e.g. 1 */