Re: What's the state of (guix build download-nar)?

[Simon Tournier]

Hi,

On jeu., 09 févr. 2023 at 09:16, Maxim Cournoyer <maxim.cournoyer@gmail.com> 
wrote:

>> Currently it’s used by some of the (guix VCS-download) modules.  I think
>> we should just update to (1) use lzip instead of gzip, and (2) have it
>> check ci.guix.gnu.org + bordeaux.guix.gnu.org.
>
> How about using zstd?  I'm proposing it instead of lzip, because long
> term, I think we want to reduce the size of our storage requirements and
> offer a single compression type for our NARs, which zstd would be ideal
> (it's faster and compresses close enough to lzip).

I guess it’s the same direction as this thread [1],

        When substitute download + decompression is CPU-bound
        Ludovic Courtès <ludo@gnu.org>
        Mon, 14 Dec 2020 23:20:17 +0100
        id:87im94qbby.fsf@gnu.org

especially this Guillaume’s message [2] comparing various methods.  The
possible agenda [3] concluding the thread was, quoting:

        We could do that.  I suppose a possible agenda would be:

          1. Start providing zstd susbstitutes anytime.  However, most clients
             will keep choosing lzip because it usually compresses better.

          2. After the next release, stop providing lzip substitutes and provide
             only gzip + zstd-19.

        This option has the advantage that it wouldn’t break any installation.
        It’s not as nice as the ability to choose a download strategy, as we
        discussed earlier, but implementing that download strategy sounds
        tricky.

Well, to be honest, I am a bit lost about the compression methods;
especially when also considering this old blog post [4].

As the subject of this thread is asking: “What's the state of (guix
build download-nar)?” ;-)

1: https://yhetil.org/guix/87im94qbby.fsf@gnu.org/#r
2: https://yhetil.org/guix/87ft3d2fge.fsf@yamatai
3: https://yhetil.org/guix/87bld9j651.fsf@gnu.org
4: https://guix.gnu.org/en/blog/2019/substitutes-are-now-available-as-lzip/


Cheers,
simon