if (!Strings.isNullOrEmpty(error)) {
            throw new IllegalArgumentException(error);
        }

        final Deferred<T> deferred = new Deferred<>();
        try {
            processRequest(client, deferred);
        } catch (final Exception e) {
            throw new SuggesterException(e);
        }
        return deferred.promise();
    }

    /**
     * Processes the request.

     */
    public void setQueryFreqThreshold(final int queryFreqThreshold) {
        this.queryFreqThreshold = queryFreqThreshold;
    }

    @Override
    protected void processRequest(final Client client, final Deferred<PopularWordsResponse> deferred) {
        final SearchRequestBuilder builder = client.prepareSearch(index);
        builder.setSize(size);
        builder.setQuery(buildQuery());