HTTP version is not honored when using a proxy

[AlecHaring]

Running this code:

import httpx

def http_version_test(url):
    # with proxy
    with httpx.Client(http2=True,
                      proxies={"all://": f"http://127.0.0.1:8080"}) as client:
        res = client.get(url)
        print(f"With proxy: {res.http_version}")

    # without proxy
    with httpx.Client(http2=True) as client:
        res = client.get(url)
        print(f"Without proxy: {res.http_version}")


if __name__ == '__main__':
    http_version_test('https://httpbin.org/get')

Will output this:

With proxy: HTTP/1.1
Without proxy: HTTP/2

It seems like the problem arises in the HTTPTransport's constructor. If proxy is not set, it sets HTTPTransport._pool to a new httpcore.ConnectionPool and passes along the HTTP version arguments. If proxy is set, it sets HTTPTransport._pool to httpcore.HTTPProxy but does not pass along the HTTP version arguments (presumably because the HTTPProxy class does not allow you to specify the HTTP version).

[lovelydinosaur]

Correct. At this point in time we should simply document that proxy HTTP requests always use HTTP/1.1.

[AlecHaring]

Is there a specific reason HTTP2 support was removed from the HTTPProxy class in encode/httpcore@f9b9391? Was it just too unstable?

[lovelydinosaur]

It's never been supported for proxies. (It's just a fiddly slightly confusing bit of extra work that I've never looked into.)

[AlecHaring]

httpx has never supported HTTP2 with proxies? If you run the above code using version 0.20.0 you get this:

With proxy: HTTP/2
Without proxy: HTTP/2

[lovelydinosaur]

Okay, that is /not/ what I'd expected, perhaps tunnelled connections did work. Worth looking into.

[p1-ra]

Hi,

The following PRs resolved that issue.

• Fix: proxy http2 prior to knowledge support #1647
• Fix: proxy http2 prior to knowledge support httpcore#342

They are waiting feedbacks since May 2021.

Thanks

[lovelydinosaur]

Resolved from 0.2.12 onwards.