How to Cache Derivations When Developing NixOS Integration Tests?

Help
1

I have a nixos integration test defined in my flake that imports two modules.

imports = [
    bootstrapMod
    webserverMod
];

these modules are built in a let statement using a function that takes a derivation as an input, and then the output of the function is the module.

        bootstrapMod = ((import ./service.app.nix) bootstrap);
        webserverMod = ((import ./service.webserver.nix) app);

the service files look like this

app:
{ config, lib, pkgs, ... }:

let
  cfg = config.services.webserver;
in
{
  options.services.webserver = {
    enable = lib.mkEnableOption "webserver Service";
    path = [ pkgs.nix pkgs.git ];

    after = lib.mkOption {
      type = lib.types.listOf lib.types.str;
      default = [  "network.target" ];
      example = [ "network.target" "serve.service" "seeddb.service"];
      description = "";
    };
  };

  config = lib.mkIf cfg.enable {
    system.stateVersion = "23.05";

    systemd.services.webserver = {
      environment = {

      };
      description = "webserver";
      after = cfg.after;
      wantedBy = [ "multi-user.target" ];
      serviceConfig = {
        ExecStart = "${app}/bin/app";
        Type = "simple";
      };
    };
  };
}

and app is a derivation that builds the app. Every time i run a nixos integration test, the app derivation needs to be rebuilt. how can i cache this if the app derivation hasn’t changed?

I was thinking that I could make a separate flake for bootstrap and app, make those outputs of that flake, and import them into this flake but was wondering if that was over complicating things

2

You probably need to filter the source to not include any irrelevant changes and then you get a cache hit.

1 Like