Re: Verification Builds for Guix

[zimoun]

Dear,

I do not know if it is relevant and if it completes what janneke already said.


On Wed, 13 May 2020 at 08:54, Jan Nieuwenhuizen  wrote:

> > Checking out the packages part of the website I found that there is at
> > least an CI creating binaries. Are those also offered to users?

The build farm (by default) is reachable at [1] and it offers binary
substitutes.  Another entry point is Guix Data Service [1] which
collects data about packages, builds, branches, etc.; for example the
history of versions [3] or the status of builds [4].  Moreover, there
is a recent proposal: build-coordinator [5].

[1] https://ci.guix.gnu.org/
[2] http://data.guix.gnu.org/
[3] https://data.guix.gnu.org/repository/1/branch/master/package/git
[4] 
https://data.guix.gnu.org/repository/1/branch/master/package/git/output-history?output=out=armhf-linux=none
[5] https://lists.gnu.org/archive/html/guix-devel/2020-04/msg00323.html


> This hash includes the transitive dependencies and can be calculated
> without compiling anything.  The "binary package", once built, will be
> installed using this hash, e.g.:
> "/gnu/store/18hp7flyb3yid3yp49i6qcdq0sbi5l1n-guile-3.0.2".

This hash identifies the package and the transitive dependencies, so
the hash is an unique identifier (modulo hash collisions which are
another story).
The same hash should produce the same binary or there is source of
non-determinism.  That's why "guix build --check" rebuilds and compare
the two builds.

I do not know what is the policy on the build farm ci.guix.gnu.org
about checking the rebuild.


> Guix does have the "guix challenge" command
>
> --8<---cut here---start->8---
> guix challenge --help
> Usage: guix challenge [PACKAGE...]
> Challenge the substitutes for PACKAGE... provided by one or more servers.
>
>   --substitute-urls=URLS
>  compare build results with those at URLS
> --8<---cut here---end--->8---
>
> now the trick is, to get "someone" to run that on an interesting portion
> of the archive...and to report the results in some common format.

I am not aware of such initiative.  Which should be really cool.

On the other hand, using this information of challenging the local
builds against remote builds would allow to share /gnu/store/; other
said full distributed substitutes mechanism.



Best regards,
simon

Re: Verification Builds for Guix

[Jan Nieuwenhuizen]

Paul Spooren writes:

[cc: guix-devel]

Hello Paul,

> I've used the last week a bit to work on some kind of verification build
> collector. Essentially a scraper of rebuild results. Meaning, an official 
> binary
> provided by a project is tried to rebuild.

Okay...

> This works already for Archlinux and OpenWrt[0], now I wanted to know if the
> same would make sense for Guix.

Possibly...I'm not sure, cc'ing guix-devel :-)

> Checking out the packages part of the website I found that there is at
> least an CI creating binaries. Are those also offered to users?

Yes, Guix (like Nix) uses a mechanism that enables (encourages?) users
to always build everything from source.  The result of a package build,
a "binary package" is uniquely identified by a hash of its inputs,
including its build recipe, e.g.,
"18hp7flyb3yid3yp49i6qcdq0sbi5l1n-guile-3.0.2".

This hash includes the transitive dependencies and can be calculated
without compiling anything.  The "binary package", once built, will be
installed using this hash, e.g.:
"/gnu/store/18hp7flyb3yid3yp49i6qcdq0sbi5l1n-guile-3.0.2".

A user can opt-in to using "binary substitutes".  In that case when a
installing a package, before the package build actually starts, Guix
checks if a binary is already available from a substitute server using
this hash.  If a binary is available it simply (well...keys/trust etc.)
downloads the build result.  In my case it checks for these in order


http://banaan.local:8080/nar/gzip/18hp7flyb3yid3yp49i6qcdq0sbi5l1n-guile-3.0.2

http://janneke.lilypond.org:8080/nar/gzip/18hp7flyb3yid3yp49i6qcdq0sbi5l1n-guile-3.0.2

http://kluit.dezyne.org:8181/nar/gzip/18hp7flyb3yid3yp49i6qcdq0sbi5l1n-guile-3.0.2

https://ci.guix.gnu.org/nar/lzip/18hp7flyb3yid3yp49i6qcdq0sbi5l1n-guile-3.0.2

> If so a rebuilder of exactly these images would be interesting to
> integrate in the rebuild-collector.

Okay...so be clear on this; Guix (nor Nix) have the concept of
REbuilders; all builders are equal: the central CI builder is not "more
equal" than any other ;-)

Guix does have the "guix challenge" command

--8<---cut here---start->8---
guix challenge --help
Usage: guix challenge [PACKAGE...]
Challenge the substitutes for PACKAGE... provided by one or more servers.

  --substitute-urls=URLS
 compare build results with those at URLS
--8<---cut here---end--->8---

now the trick is, to get "someone" to run that on an interesting portion
of the archive...and to report the results in some common format.

Looking at

> [0]: https://rebuild.aparcar.org/

I think it could work, although for Guix I think it would be more
natural to consider the local build to be the the "original" to compare
binary substitute servers against?  Maybe the format could be more
symmetrical?

Greetings,
janneke

-- 
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