使用 Flask 代理到另一个 Web 服务

我想将对 Flask 应用程序发出的请求代理到计算机上本地运行的另一个 Web 服务。我宁愿使用 Flask 而不是更高级别的 nginx 实例，这样我们就可以重用应用程序中内置的现有身份验证系统。我们越能保持这种“单点登录”越好。

是否有现有的模块或其他代码可以执行此操作？尝试将 Flask 应用程序桥接到 httplib 或 urllib 之类的东西被证明是一件痛苦的事情。

我花了很多时间研究同一件事，最终找到了一个解决方案requests看起来运行良好的库。它甚至可以在一个响应中设置多个 cookie，这需要一些调查才能弄清楚。这是烧瓶视图函数：

from dotenv import load_dotenv  # pip package python-dotenv
import os
#
from flask import request, Response
import requests  # pip package requests


load_dotenv()
API_HOST = os.environ.get('API_HOST'); assert API_HOST, 'Envvar API_HOST is required'

@api.route('/', defaults={'path': ''}, methods=["GET", "POST"])  # ref. https://medium.com/@zwork101/making-a-flask-proxy-server-online-in-10-lines-of-code-44b8721bca6
@api.route('/<path>', methods=["GET", "POST"])  # NOTE: better to specify which methods to be accepted. Otherwise, only GET will be accepted. Ref: https://flask.palletsprojects.com/en/3.0.x/quickstart/#http-methods
def redirect_to_API_HOST(path):  #NOTE var :path will be unused as all path we need will be read from :request ie from flask import request
    res = requests.request(  # ref. https://stackoverflow.com/a/36601467/248616
        method          = request.method,
        url             = request.url.replace(request.host_url, f'{API_HOST}/'),
        headers         = {k:v for k,v in request.headers if k.lower() != 'host'}, # exclude 'host' header
        data            = request.get_data(),
        cookies         = request.cookies,
        allow_redirects = False,
    )

    #region exlcude some keys in :res response
    excluded_headers = ['content-encoding', 'content-length', 'transfer-encoding', 'connection']  #NOTE we here exclude all "hop-by-hop headers" defined by RFC 2616 section 13.5.1 ref. https://www.rfc-editor.org/rfc/rfc2616#section-13.5.1
    headers          = [
        (k,v) for k,v in res.raw.headers.items()
        if k.lower() not in excluded_headers
    ]
    #endregion exlcude some keys in :res response

    response = Response(res.content, res.status_code, headers)
    return response

2021 年 4 月更新：excluded_headers可能应该包括由定义的所有“逐跳标头”RFC 2616 第 13.5.1 节 https://www.rfc-editor.org/rfc/rfc2616#section-13.5.1.