Question

我正在制作一个需要进行快速HTTP API调用的python应用程序。我使用python请求包在HTTPS上进行API调用。我注意到第一次请求总是比其他请求花费更多时间。这不是因为建立HTTP连接，因为requests.get（）在每次调用时都建立了一个新连接（带有日志的已检查请求）。

我使用Wireshark调查了我的网络，虽然我发现第一个请求比其他请求花费的时间更长，但差别并不大。

我还注意到即使我第一次调用host1而所有其余的调用都发送到host2，对host1的请求比所有后续请求花费的时间要多得多。这向我保证，该问题与与主机建立某种联系无关。

我使用ping命令检查了并没有在第一个和后续的ping请求之间找到这样的区别。

是否与操作系统有关，请求在第一个请求或其他内容上进行初始设置？

我的python代码：

import requests
import time
import logging


logging.basicConfig(level=logging.DEBUG)

url = "https://bittrex.com/api/v1.1/public/getorderbook?market=BTC-LTC&type=both"

for i in range(10):
    start = time.time()

    requests.get(url)

    end = time.time()

    print('Time: {}. index: {}'.format(end - start, i))

输出：

DEBUG:urllib3.connectionpool:Starting new HTTPS connection (1): bittrex.com
DEBUG:urllib3.connectionpool:https://bittrex.com:443 "GET /api/v1.1/public/getorderbook?market=BTC-LTC&type=both HTTP/1.1" 200 46568
Time: 0.8292889595031738. index: 0
DEBUG:urllib3.connectionpool:Starting new HTTPS connection (1): bittrex.com
DEBUG:urllib3.connectionpool:https://bittrex.com:443 "GET /api/v1.1/public/getorderbook?market=BTC-LTC&type=both HTTP/1.1" 200 46568
Time: 0.14321112632751465. index: 1
DEBUG:urllib3.connectionpool:Starting new HTTPS connection (1): bittrex.com
DEBUG:urllib3.connectionpool:https://bittrex.com:443 "GET /api/v1.1/public/getorderbook?market=BTC-LTC&type=both HTTP/1.1" 200 46568
Time: 0.10214948654174805. index: 2
DEBUG:urllib3.connectionpool:Starting new HTTPS connection (1): bittrex.com
DEBUG:urllib3.connectionpool:https://bittrex.com:443 "GET /api/v1.1/public/getorderbook?market=BTC-LTC&type=both HTTP/1.1" 200 46568
Time: 0.10616683959960938. index: 3
DEBUG:urllib3.connectionpool:Starting new HTTPS connection (1): bittrex.com
DEBUG:urllib3.connectionpool:https://bittrex.com:443 "GET /api/v1.1/public/getorderbook?market=BTC-LTC&type=both HTTP/1.1" 200 46568
Time: 0.1061558723449707. index: 4
DEBUG:urllib3.connectionpool:Starting new HTTPS connection (1): bittrex.com
DEBUG:urllib3.connectionpool:https://bittrex.com:443 "GET /api/v1.1/public/getorderbook?market=BTC-LTC&type=both HTTP/1.1" 200 46568
Time: 0.09714269638061523. index: 5
DEBUG:urllib3.connectionpool:Starting new HTTPS connection (1): bittrex.com
DEBUG:urllib3.connectionpool:https://bittrex.com:443 "GET /api/v1.1/public/getorderbook?market=BTC-LTC&type=both HTTP/1.1" 200 46568
Time: 0.0861358642578125. index: 6
DEBUG:urllib3.connectionpool:Starting new HTTPS connection (1): bittrex.com
DEBUG:urllib3.connectionpool:https://bittrex.com:443 "GET /api/v1.1/public/getorderbook?market=BTC-LTC&type=both HTTP/1.1" 200 46568
Time: 0.08713865280151367. index: 7
DEBUG:urllib3.connectionpool:Starting new HTTPS connection (1): bittrex.com
DEBUG:urllib3.connectionpool:https://bittrex.com:443 "GET /api/v1.1/public/getorderbook?market=BTC-LTC&type=both HTTP/1.1" 200 46568
Time: 0.09714365005493164. index: 8
DEBUG:urllib3.connectionpool:Starting new HTTPS connection (1): bittrex.com
DEBUG:urllib3.connectionpool:https://bittrex.com:443 "GET /api/v1.1/public/getorderbook?market=BTC-LTC&type=both HTTP/1.1" 200 46568
Time: 0.09714889526367188. index: 9

Answer 1

请参阅：
Python requests module is very slow on specific machine
Why is Python 3 http.client so much faster than python-requests?
requests: how to disable / bypass proxy

对于某些人来说，这个问题似乎与代理人有关对您的代码进行的这一更改为我带来了巨大的速度。

import requests
import time
import logging
logging.basicConfig(level=logging.DEBUG)
url = "https://bittrex.com/api/v1.1/public/getorderbook?market=BTC-LTC&type=both"
session = requests.Session()
session.trust_env = False

for i in range(10):
    start = time.time()

    session.get(url)

    end = time.time()

    print('Time: {}. index: {}'.format(end - start, i))

来自requests: how to disable / bypass proxy
作者：@Lukas Graf
“我目前唯一能够完全禁用代理的方法如下：

创建会话
将session.trust_env设置为False
使用该会话创建您的请求“

您的里程可能会有所不同

Answer 2

我也有同样的问题。第一个请求需要5秒，而其他请求很快。我尝试更新请求和python，问题仍然存在。然后，我检查服务器的负载和网络连接，没有错。我尝试了这段代码：

logging.basicConfig()   
logging.getLogger().setLevel(logging.DEBUG)  
requests_log = logging.getLogger("requests.packages.urllib3")  
requests_log.setLevel(logging.DEBUG)  
requests_log.propagate = True

它显示第一个DEBUG:urllib3.connectionpool:Starting new HTTPS connection (1)持续5秒钟。

我也尝试使用会话而不是获取，没有任何改善。

最后，我将域添加到/etc/hosts，问题已解决。

所以我认为关键是DNS。

第一个HTTPS请求比其余请求花费更多时间

2 个答案: