Subject: Re: [PATCH v3 12/35] serve: introduce git-serve

From: Jonathan Nieder <[email-masked]>
Date: Mon, 5 Mar 2018 13:36:49 -0800

Hi,

Jeff King wrote:

> I agree that would be a lot more pleasant for adding protocol features.
> But I just worry that the stateful protocols get a lot less efficient.
> I'm having trouble coming up with an easy reproduction, but my
> recollection is that http has some nasty corner cases, because each
> round of "have" lines sent to the server has to summarize the previous
> conversation. So you can get a case where the client's requests keep
> getting bigger and bigger during the negotiation (and eventually getting
> large enough to cause problems).

That's not so much a corner case as just how negotiation works over
http.

We want to do better (e.g. see [1]) but that's a bigger change than
the initial protocol v2.

As Brandon explained it to me, we really do want to use stateless-rpc
semantics by default, since that's just better for maintainability.
Instead of having two protocols, one that is sane and one that
struggles to hoist that into stateless-rpc, there would be one
stateless baseline plus capabilities to make use of state.

For example, it would be nice to have a capability to remember
negotiation state between rounds, to get around exactly the problem
you're describing when using a stateful protocol.  Stateless backends
would just not advertise such a capability.  But doing that without [1]
still sort of feels like a cop-out.  If we can get a reasonable
baseline using ideas like [1] and then have a capability to keep
server-side state as icing on the cake instead of having a negotiation
process that only really makes sense when you have server-side state,
then that would be even better.

> If anything, I wish we could push the http protocol in a more stateful
> direction with something like websockets. But I suspect that's an
> unrealistic dream, just because not everybody's http setup (proxies,
> etc) will be able to handle that.

Agreed.  I think we have to continue to deal with stateless-rpc
semantics, at least for the near future.

Jonathan

[1] https://public-inbox.org/git/[email-masked]/