splitting hive.nix into groups of hosts?

[ser]

Splitting hive.nix file into groups of hosts is not documented and I have no idea how to make it.

What i want is to have a short hive.nix file like this:

{
meta = {};
defaults = { config, pkgs, lib, modulesPath, builtins, ... }: {};
}

and for example a group of hosts file srv.nix like this:

{
srv1 = { config, pkgs, lib, modulesPath, builtins, ... }: {};
srv2 = { config, pkgs, lib, modulesPath, builtins, ... }: {};
}

Question is - how to properly include srv.nix in hive.nix?

[justinas]

Something as simple as:

{
  meta = {};
  defaults = { config, pkgs, lib, modulesPath, builtins, ... }: {};
} // (import ./srv.nix)

should work. This isn't a colmena thing, but a nix thing: as "hives" are just attrsets, you can use the attrset update syntax.

[ser]

Sorry, but it does not work.

error: attempt to call something which is not a function but a set

[justinas]

Your minimized example totally does work (up to a point, because node configurations are empty):

$ cat hive.nix
{
  meta = {};
  defaults = { config, pkgs, lib, modulesPath, builtins, ... }: {};
} // (import ./srv.nix)
$ cat srv.nix
{
  srv1 = { config, pkgs, lib, modulesPath, builtins, ... }: {};
  srv2 = { config, pkgs, lib, modulesPath, builtins, ... }: {};
}
$ colmena build -v
[INFO ] Using configuration: /home/justinas/ser/hive.nix
[INFO ] Enumerating nodes...
[INFO ] Selected all 2 nodes.
(...) | Evaluating srv1 and srv2
(...) | trace: warning: system.stateVersion is not set, defaulting to 24.05. Read why this matters on https://nixos.org/manual/nixos/stable/options.html#opt-system.stateVersion.
(...) | error:
(...) |        … while evaluating attribute 'srv1'
(...) |
(...) |          at «none»:0: (source not available)
(...) |
(...) |        … while calling the 'head' builtin
(...) |
(...) |          at /nix/store/w6w8z9w6ywpfvy8pjwsky51hc8xj0ilx-6c9x72i5sf121x2r7vfm6fj57aw2sx33-nixos-24.05-2024-07-25/lib/attrsets.nix:1575:11:
(...) |
(...) |          1574|         || pred here (elemAt values 1) (head values) then
(...) |          1575|           head values
(...) |              |           ^
(...) |          1576|         else
(...) |
(...) |        (stack trace truncated; use '--show-trace' to show the full trace)
(...) |
(...) |        error:
(...) |        Failed assertions:
(...) |        - The ‘fileSystems’ option does not specify your root file system.
(...) |        - You must set the option ‘boot.loader.grub.devices’ or 'boot.loader.grub.mirroredBoots' to make the system bootable.
(...) | Evaluation failed: Child process exited with error code: 1
      | Failed: Child process exited with error code: 1
<...>

If you are having additional errors, it is likely because of something that is in your configuration. There's no way to tell from your example.

[ser]

OK, thanks for an example, now I can understand that // is not a comment but part of nixos language - I would never expect that :-)

So yes, I was able to finally split long hive.nix in this way:

{
meta = {};
defaults = { config, pkgs, lib, modulesPath, builtins, ... }: {};
}
// ( import ./srv.nix )
// ( import ./othersrv.nix )
// ( import ./dnsserv.nix )

In my opinion Colmena documentation should include such a use case with good practices, as not every Colmena user must be a nixos expert, there are also just users like me...

Thanks.