google-http-client请求处理超时

Question

        HttpTransport httpTransport = GoogleNetHttpTransport.newTrustedTransport();
        HttpRequestFactory requestFactory = httpTransport.createRequestFactory();

        long begin = System.currentTimeMillis();
        HttpRequest request = requestFactory.buildPostRequest(
                new GenericUrl(RecommendationEngineConstant.MAKE_RECOMMENDATION_PREDICT),
                new JsonHttpContent(new JacksonFactory(), json));
        request.setConnectTimeout(10000);
        request.setReadTimeout(10000);

        HttpResponse response = request.execute();
        long time = System.currentTimeMillis() - begin;
        if (time >= 3000) {
            logger.error(">> returned in " + time + "ms, and predict json = " + json.toPrettyString());
        }

上面的代码中的“时间”超过了3秒，但是使用CURL请求API的返回非常快，这种情况约占20％，请问是什么问题？