Document protocol versions and negotiation mechanism

[qwerty32123]

I need to make a http2 get requests, i tried with hyper but having issues with headers my question is if i can make these same requests with httpx
python-hyper/hyper#416
I dont see in documentation anything about requests compatibility or about using http2 when doing the requests

also it has proxy support?

[sethmlarson]

Currently httpx supports HTTP/2 via ALPN (meaning HTTPS-only) and does so automatically (We negotiate which protocol version to use before issuing requests).

We could add a section in the documentation about which protocols we support and via what mechanism they are negotiated.

Proxy support is planned, see #163

[jlaine]

Looking a bit further into the future how do we plan to support HTTP/3? Unlike HTTP/2, support can only be determined after a first request completes, if the Alt-Svc header is present.

https://http3-explained.haxx.se/en/h3-altsvc.html

curl has flags which allow you to force the http version, do we want something similar?

[sethmlarson]

Yep, it's a completely different deal. I've got a couple thoughts on how we can support H3:

• Make it a Dispatcher, probably the easiest but the least integrated. It could be bundled with httpx or a separate library.
• Integrate directly with httpx, maybe controllable on the client (allow_http3?) and then we have a client session data storage mechanism. Could be used for alt-svc, cookies, hsts that aren't on the preload list, with a middleware could be used as a cache, all sorts of important things that HTTP clients should remember.

I'd prefer option 2 for multiple reasons, because I feel like the client session storage should be a feature regardless of whether we integrate HTTP/3 natively

[tomchristie]

Integrate directly with httpx

Yup, we'd want to go down this route.

On a first pass we probably wouldn't bother storing info about "is an HTTP/3 service available for this host", but instead just rely on "Is there an existing H3 connection, or an existing upgradable H1/2 connection"? Our standard connection keep-alive policy would be enough to make sure that users would end up on HTTP/3 services where available.

curl has flags which allow you to force the http version, do we want something similar?

Yes - we'll want something like an http_version(s) argument & property on the Client and top-level API, which can be used to specify which of 1.1 / 2 / 3 should be supported.

[sethmlarson]

Do we really want it for the top level API? I'm talking about the httpx.request() APIs. Tbh I don't see a point to doing anything except HTTP/1 on those short-lived connections.

[tomchristie]

Yes true - wasn't really thinking there.

[florimondmanca]

Closing this as most likely stale now - see HTTP/2 Support.