return num;
        }
        return Runtime.getRuntime().availableProcessors();
    }

    Integer getCrawlerHttpThreadPoolSizeAsInteger();

    default int getCrawlerHttpProcessors() {
        final int num = getCrawlerHttpThreadPoolSizeAsInteger();
        if (num > 0) {
            return num;
        }
        return Runtime.getRuntime().availableProcessors();
    }

     * @return The value of found property. (NotNull: if not found, exception but basically no way)
     * @throws NumberFormatException When the property is not integer.
     */
    Integer getCrawlerHttpThreadPoolSizeAsInteger();

    /**
     * Get the value for the key 'crawler.data.serializer'. <br>
     * The value is, e.g. kryo <br>
     * comment: Serializer type for crawler data (e.g., kryo).