Define local extractors

[kjeremy]

Can I define extractors locally in my project? For instance I use some services from https://github.com/lopsided98/nix-ros-overlay/ and have some other services defined locally in my flake that I would like to detect.

[oddlama]

Of course, the extractors are just a regular NixOS module that are included on your host. All it does is to define some entries in topology.self.services. Anything you put in there will be shown automatically.

So anywhere in your relevant nixos configurations you can just do something like:

topology.self.services.mycustomservice = mkIf config.services.mycustomservice.enable {
  name = "My Custom Service";
  icon = ./mycustomservice.svg; # any SVG (recommended) / PNG
  # Extra stuff to show
  details.listen = "${config.services.mycustomservice.address}:${toString config.services.mycustomservice.port}";
};

[oddlama]

Relevant options: https://oddlama.github.io/nix-topology/topology-options.html#nodesnameservices

[kjeremy]

Thank you. I'm struggling a little with this:

  topology-diagrams =
    let t = import inputs.nix-topology {
      pkgs = local.legacyPackages;
      modules = [
        ({config, ...} : { topology.self.services.what = { name = "HI"; info = "INFO"; }; })
        { nixosConfigurations = mapAttrs (n: v: nixosWithModules v) hosts; }
      ];
    };
    in t.config.output;

$ nix build .#myplatform/topology-diagrams

ends in:

 … while evaluating the attribute 'config.output'
         at /nix/store/dk2rpyb6ndvfbf19bkb2plcz5y3k8i5v-source/lib/modules.nix:322:9:
          321|         options = checked options;
          322|         config = checked (removeAttrs config [ "_module" ]);
             |         ^
          323|         _module = checked (config._module);

       (stack trace truncated; use '--show-trace' to show the full, detailed trace)

       error: The option `topology.topology.self' does not exist. Definition values:
       - In `<unknown-file>':
           {
             services = {
               what = {
                 info = "INFO";
                 name = "HI";
           ...

[oddlama]

This -> topology.self.services.what = { name = "HI"; info = "INFO"; }; is supposed to go into your nixos configuration, not the topology config. Set it on the host that exposes the service