Re: How to create a substitute server with substitutes that failed?

[Dr. Arne Babenhauserheide]

Christopher Baines <mail@cbaines.net> writes:

> Dr. Arne Babenhauserheide <arne_bab@web.de> writes:
>
>> I’d like to create a small server that provides substitutes for
>> packages for which I often have to build a fallback (mostly ungoogled
>> Chromium).
>>
>> How can I do that? Is there already a simply way?
>
> It's not simple (yet), but I'm hoping to get there eventually with the
> Guix Build Coordinator.
>
> 1: https://git.cbaines.net/guix/build-coordinator/about/
…
> I realise the promise of being able to do this more easily in the future
> isn't that helpful, but I still wanted to mention the Guix Build
> Coordinator in case it's something you're interested in.

It sounds promising and I’m not in so much of a hurry that I can’t wait
a bit more.

Thank you!

What I need is likely much simpler, though: I need a hook which triggers
whenever a package had to be built locally. That way we could have
dynamic substitute-servers.

And seeing guix publish run locally got me wishing more that I’d already
be finished with my download-mesh implementation, because guix would be
a perfect usecase for that: We can actually add headers and people have
long-running servers. Parts of the content-addressed storage and
chunk-assembly are already done, but I’m still missing the validation of
chunks and making currently running downloads available.

Conceptually it’s simple: Users could tell guix to serve all derivations
they downloaded and tell the server to mark their guix-daemon as
content-addressed alternate source (X-Alt), then when someone downloaded
something like the 828MiB chromium derivation, the original server would
hand out a list of X-Alts, the hash for content-addressed retrieval and
a merkle-tree of chunk hashes for chunk-validation, so clients could
download from other clients without having to trust them.

The current state of my implementation of such a server and downloader
is at https://hg.sr.ht/~arnebab/wispserve/browse/wispserve/serve.w?rev=tip

And while writing this message I implemented serving while downloading.

Best wishes,
Arne
-- 
Unpolitisch sein
heißt politisch sein
ohne es zu merken

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