[Haskell-cafe] HTTP/2 implementation?

Ben Bangert ben at groovie.org
Sat Jul 26 04:00:31 UTC 2014

On Jul 25, 2014, at 6:45 PM, Kazu Yamamoto (山本和彦) <kazu at iij.ad.jp> wrote:

> I would be nice if we can work together.

Absolutely! I definitely would prefer not to do this by myself. :)

> Mighty is a web server based on Warp. Currently, Mighty implements
> reverse proxy only. I'm planning to implement (forward) proxy and
> supports HTTP/2 in forward/reverse proxy.

Cool! From my evaluation, HTTP/2 proxy is going to be very very different from HTTP/1. In HTTP/1 every request/response cycle is a separate TCP connection, while proxying in HTTP/2 to a single authority server can multiplex (or use multiple multiplexed connections). A server that knows its being proxied to will require very different settings (with much higher max concurrent streams) than a server expected to handle public requests. I've been trying to determine the various requirements and config options needed.

I've also been considering the ability to 'replay' specific streams for fail-over. For example, if a stream enter half-closed (remote), and nothing except perhaps push promise frames have been sent before the server being proxied to dies, then the proxy can replay the headers needed to restore that state to a new app-server.

> I don't understand this problem yet due to the lack of experience. But
> if direct access is really necessary, you can propose to extend WAI.

In my case, after a client does a GET to a specific URI, I don't want to send any content. I want to keep the connection open indefinitely and occasionally send PUSH PROMISE frames down to send messages, per the new HTTP/2 PUSH spec:

This requires the ability in a request handler to send push promise frames and write the content for the newly allocated streams, all without fully returning (and thus ending) the request/response stream that started it. The node-http2 API implemented a special command to enable this.

> I think that web-devel at haskell.org is a proper place to discuss this.

Ah, thanks, I didn't know that list existed. :)

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