}
        throw cause;
    }

    @Override
    @PreDestroy
    public void close() {
        if (runner != null) {
            try {
                client.admin().indices().prepareFlush().setForce(true).execute()
                        .actionGet(ComponentUtil.getFessConfig().getIndexIndicesTimeout());
            } catch (final Exception e) {
                logger.warn("Failed to flush indices.", e);