From mboxrd@z Thu Jan  1 00:00:00 1970
From: ludo@gnu.org (Ludovic =?UTF-8?Q?Court=C3=A8s?=)
Subject: bug#22774: Bootstrapping issue with HTTPS downloads
Date: Mon, 14 Nov 2016 00:02:38 +0100
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ludo@gnu.org (Ludovic Court=C3=A8s) skribis:

> The =E2=80=98wip-oob-download=E2=80=99 implements =E2=80=9Cout-of-band do=
wnloads=E2=80=9D, whereby
> downloads are performed by the daemon on behalf of clients.
>
> This works by adding a =E2=80=9Cbuilt-in builder=E2=80=9D in the daemon (=
idea stolen
> from the Nix daemon): if you specify =E2=80=9Cbuiltin:download=E2=80=9D a=
s the builder
> of your derivation, then guix-daemon invokes =E2=80=98guix download=E2=80=
=99 to download
> the thing.  The derivation has to be fixed-output, of course.
>
> The branch is not ready yet, notably because we=E2=80=99d need a way to p=
ass
> mirror lists to =E2=80=98guix download=E2=80=99, as an attribute of the d=
erivation.

Fixed!

> Another question is compatibility: what if a recent client creates a
> =E2=80=9Cbuiltin:download=E2=80=9D derivation on an old daemon?  The prob=
lem is that
> currently old daemons do not check the builder of the .drv file until
> you call =E2=80=98build-derivations=E2=80=99.  So I think we=E2=80=99ll n=
eed to bump the
> protocol version so client code can check whether the daemon is new
> enough.

To address that, I bumped the protocol number in worker-protocol.hh and
added a =E2=80=98built-in-builders=E2=80=99 RPC that returns the list of su=
pported
built-in builders (a list of strings.)

That way, clients can check what the daemon supports.  For instance,
=E2=80=98url-fetch=E2=80=99 can return either a =E2=80=9Cnormal=E2=80=9D fi=
xed-output derivation or one
that uses =E2=80=9Cbuiltin:download=E2=80=9D, depending on what the daemon =
supports.

Feedback welcome.

Ludo=E2=80=99.