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/20180227054638.GB65699@aiede.svl.corp.google.com/