presto-elasticsearch/src/main/java/io/prestosql/elasticsearch/client/ElasticsearchClient.java/ElasticsearchClient/doRequest
class ElasticsearchClient:    private <T> T doRequest(String path, ResponseHandler<T> handler)
    {
        checkArgument(path.startsWith("/"), "path must be an absolute path");

        Response response;
        try {
            response = client.getLowLevelClient()
                    .performRequest("GET", path);
        }
        catch (IOException e) {
            throw new PrestoException(ELASTICSEARCH_CONNECTION_ERROR, e);
        }

        String body;
        try {
            body = EntityUtils.toString(response.getEntity());
        }
        catch (IOException e) {
            throw new PrestoException(ELASTICSEARCH_INVALID_RESPONSE, e);
        }

        return handler.process(body);
    }