如何使用请求库在 python 中测试重试尝试

Question

我有以下内容：

from requests.adapters import HTTPAdapter
from requests.packages.urllib3.util.retry import Retry

retry_strategy = Retry(
    total=3,
    status_forcelist=[429, 500, 502, 503, 504],
    method_whitelist=["HEAD", "GET", "OPTIONS"]
)
adapter = HTTPAdapter(max_retries=retry_strategy)
http = requests.Session()
http.mount("https://", adapter)
http.mount("http://", adapter)

response = http.get("some_endpoint")

如何有效地进行单元测试，让我重试 N 次（在本例中为 3 次）？

Answer 1

我也想知道，但我找不到任何建议，甚至在 Stack Overflow 上也找不到。但我真的想确保它按我的预期工作......

我花了一段时间才弄清楚在哪里以及如何修补urllib3以正确测试它，但这是迄今为止我想出的最佳解决方案，为您节省了几个小时的研究时间：

import urllib3
from http.client import HTTPMessage
from unittest.mock import ANY, Mock, patch, call

import requests


def request_with_retry(*args, **kwargs):
    session = requests.Session()
    adapter = requests.adapters.HTTPAdapter(max_retries=urllib3.Retry(
        raise_on_status=False,
        total=kwargs.pop("max_retries", 3),
        status_forcelist=[429, 500, 502, 503, 504],  # The HTTP response codes to retry on
        allowed_methods=["HEAD", "GET", "PUT", "DELETE", "OPTIONS"],  # The HTTP methods to retry on
    ))
    session.mount("https://", adapter)
    session.mount("http://", adapter)
    return session.request(*args, **kwargs)


@patch("urllib3.connectionpool.HTTPConnectionPool._get_conn")
def test_retry_request(getconn_mock):
    getconn_mock.return_value.getresponse.side_effect = [
        Mock(status=500, msg=HTTPMessage()),
        Mock(status=429, msg=HTTPMessage()),
        Mock(status=200, msg=HTTPMessage()),
    ]

    r = request_with_retry("GET", "http://any.url/testme", max_retries=2)
    r.raise_for_status()

    assert getconn_mock.return_value.request.mock_calls == [
        call("GET", "/testme", body=None, headers=ANY),
        call("GET", "/testme", body=None, headers=ANY),
        call("GET", "/testme", body=None, headers=ANY),
    ]

（注意：如果您多次调用此方法，那么您可能只想初始化会话对象一次，而不是每次发出请求时都初始化！）