nix-build loops while building

[domenkozar]

Nix 2.3.4

Nix seems to loop between the same derivations, see a sample of the log at https://gist.github.com/anamarijas/c5a1ea49ca1e1cbdd3f70f5a8d4aa969

To reproduce:

• git clone https://github.com/cachix/ghcide-nix
• cd ghcide-nix
• cachix use ghcide-nix
• git checkout ghc-8.8
• nix-build

[domenkozar]

I've tested on 2.3.3 and master, same loop.

[andir]

I saw a similar issue a while ago when a binary cache reported a 404 on a file that should be there. Nix did also complain that it didn't know how to build some paths. Can you post the full output that you get from Nix?

[domenkozar]

Full output is 300MB, do you have something to grep for?

I can confirm removing binary caches makes it build.

Was 404 on nar file or narinfo?

[andir]

On 10:42 26.04.20, Domen Kožar wrote: Was 404 on nar file or narinfo?

I honestly do not recall anymore. Could have been either. My guess is on a NAR file but I can't provide evidence. By now I can't reproduce it anymore. I just noticed that the temproots file would eventually fill up the entire disk and only then the build would abort. It was on some cachix bucket shortly after cloudflare was enabled there, if that helps.

[domenkozar]

Thanks @andir I'll take a look at this.

[domenkozar]

My initial hypothesis is that this is an instance of #3373 but during IFD.

[andir]

On 02:39 27.04.20, Domen Kožar wrote: My initial hypothesis is that this is an instance of #3373 but during IFD.

In my case there was no IFD.

[domenkozar]

Refs #1217 #3002

[domenkozar]

I can confirm (even on linux) this is due to missing references from a binary cache, so referenced issues are valid.

I managed to reproduce this again and in the logs it can be observed that Nix is looping between:

some references of path '/nix/store/kk48ba50zs7dj2n30nx4wxxan6273rnq-basement-0.0.11-lib-basement' could not be realised
some references of path '/nix/store/10rgwgpv65fvwajap619pn7i1xj00zky-blaze-builder-0.4.1.0-lib-blaze-builder' could not be         realised

If I try to realize one of those paths manually I get the known error:

$ nix-store -r /nix/store/kk48ba50zs7dj2n30nx4wxxan6273rnq-basement-0.0.11-lib-basement
these paths will be fetched (1.73 MiB download, 17.59 MiB unpacked):
  /nix/store/kk48ba50zs7dj2n30nx4wxxan6273rnq-basement-0.0.11-lib-basement
don't know how to build these paths:
  /nix/store/y62x4jrm775l94gccqkbqfpw2ds2z9bj-basement-0.0.11-lib-basement-doc
error: build of '/nix/store/kk48ba50zs7dj2n30nx4wxxan6273rnq-basement-0.0.11-lib-basement' failed

It seems like currently Nix assumes the binary caches has the full closure, while cachix doesn't enforce this property.

The fact that it loops is probably the result of IFD (maybe enough to trigger this is to import nixpkgs from a pin, etc).

[domenkozar]

@edolstra any idea how easy would it be to fix #3373 and hopefully this?