bug#38469: guix gc should keep around recent intermediate build ingredients by default

bug#38469: guix gc should keep around recent intermediate build ingredients by default

[Robert Vollmert]

[ This is a user/developer friendliness feature request. I’m not arguing
  that `guix gc` should do anything differently on a technical level, I’m
  just trying to argue that the default experience should be different. ]

Current situation:
  I use a forked guix repository as my default channel, which
  includes a number of slow-to-build Haskell packages. Now and
  then, I run out of disk space. So I call `guix gc`, which invariably
  removes the store paths involved in building my current system generation,
  so the next call to `guix system reconfigure` takes hours.

Desired situation:
  After calling `guix gc`, the paths that were involved in my last system
  build are still around, so reconfiguring doesn’t result in everything
  being rebuilt.

(If there’s some way I can achieve that now, perhaps by explicitly managing
some roots, or passing specific arguments to `guix gc`, I’d be happy to
know! I’d still argue that we should try to make this the default behaviour,
though.)

bug#38469: guix gc should keep around recent intermediate build ingredients by default

[Guillaume Le Vaillant]

Robert Vollmert skribis:

> [ This is a user/developer friendliness feature request. I’m not arguing
>   that `guix gc` should do anything differently on a technical level, I’m
>   just trying to argue that the default experience should be different. ]
>
> Current situation:
>   I use a forked guix repository as my default channel, which
>   includes a number of slow-to-build Haskell packages. Now and
>   then, I run out of disk space. So I call `guix gc`, which invariably
>   removes the store paths involved in building my current system generation,
>   so the next call to `guix system reconfigure` takes hours.
>
> Desired situation:
>   After calling `guix gc`, the paths that were involved in my last system
>   build are still around, so reconfiguring doesn’t result in everything
>   being rebuilt.
>
> (If there’s some way I can achieve that now, perhaps by explicitly managing
> some roots, or passing specific arguments to `guix gc`, I’d be happy to
> know! I’d still argue that we should try to make this the default behaviour,
> though.)

Have you tried passing the options '--gc-keep-derivations=yes' and
'--gc-keep-outputs=yes' to guix-daemon?

In the operating-system definition, it would be something like:
--8<---------------cut here---------------start------------->8---
(services
   (cons* (service ...)
          [...]
          (modify-services %desktop-services
            (guix-service-type config =>
              (guix-configuration
               (inherit config)
               (extra-options '("--gc-keep-derivations=yes"
                                "--gc-keep-outputs=yes")))))))
--8<---------------cut here---------------end--------------->8---

bug#38469: guix gc should keep around recent intermediate build

[Robert Vollmert]

> Have you tried passing the options '--gc-keep-derivations=yes’ and
> '--gc-keep-outputs=yes' to guix-daemon?

I had not. I added that right now, and first tests seem to indicate
that this helps. Thanks!

Would it be a bad idea to make this the default?

Alternatively, how about some kind of developer config fragment that
would modify a system configuration with settings that are a good
idea for Guix development, if not general use? That might also include
things like setting the $%!^@!*^% guile backtrace columns variable
for guix-daemon.

bug#38469: guix gc should keep around recent intermediate build

[Ludovic Courtès]

Hi,

Robert Vollmert <rob@vllmrt.net> skribis:

>> Have you tried passing the options '--gc-keep-derivations=yes’ and
>> '--gc-keep-outputs=yes' to guix-daemon?
>
> I had not. I added that right now, and first tests seem to indicate
> that this helps. Thanks!

Yes, I think these options are exactly what you want.

> Would it be a bad idea to make this the default?

I think the current defaults are more appropriate; after all, they
really allow “garbage” to be collected.

> Alternatively, how about some kind of developer config fragment that
> would modify a system configuration with settings that are a good
> idea for Guix development, if not general use? That might also include
> things like setting the $%!^@!*^% guile backtrace columns variable
> for guix-daemon.

I think what you’d want is to set COLUMNS within derivation, not “for
the daemon”.

So I don’t know, I’m sympathetic to the idea of developer settings in
Guix System, but I’m not sure what it could bring beyond these two
options.

In the meantime, I propose to close this bug and to discuss this
potential new feature separately.

Thanks,
Ludo’.