Re: [Caml-list] Functorising over Cohttp's backends

[Dario Teixeira <dario.teixeira@nleyten.com>]

Hi,

And thanks for the comprehensive response, Rudi!


> The Cohttp API at its present state doesn't really offer a good
> abstraction for creating backend independent HTTP clients and
> servers.
> 
> Luckily, the request and response types are backend independent. And
> so is the http body type if you aren't streaming. This means that
> you can fairly easily create a light application specific abstraction
> for yourself.

Yes, I'm leaning towards just functorising over "IO" and nothing
else.  I thought about functorising also over "Body", but I reckon
the API will be much simpler if I dictate that the body must be of
type Cohttp.S.Body.t, and place on the user the burden of converting
to/from this type if the backend body implementation extends over
Cohttp.S.Body (as is the case with Cohttp_lwt_body).

I reckon a truly universal solution would also need to functorise
over "Request" and "Response", but a) that way lies madness, and b)
as you pointed out, luckily these are presently backend-independent.


> To summarize, it's unfortunate that Cohttp doesn't provide a real
> server (or client) abstraction. But it's kind of hard to do without
> making a wrapper that tries to abstract away the differences between
> different backends. Hiding away the details of Async and Lwt was
> always an anti-goal for Cohttp anyway.

Cohttp is perhaps the poster child for how the Lwt/Async schism
makes many APIs way more complex than they should be!  (Not that
there's an easy solution to this situation...)

Best regards,
Dario Teixeira