ci-runner experiment

modules/ci-runner/default.nix

@@ -1,41 +1,119 @@
-{ lib, config, pkgs, self, ... }:
+{ lib, config, pkgs, self, dockerTools, ... }:
+
 with lib;
 let
+  runnerImageName = "ci-runner-docker-drone-exec";
+  runnerImage = dockerTools.buildImage {
+    name = runnerImageName;
+    tag = "latest";
+
+    fromImageName = "debian";
+
+    runAsRoot = ''
+      #!/usr/bin/env bash
+
+      set -e
+
+      apt update
+      apt install --yes curl git sudo xz-utils
+
+      adduser --system --uid 9999 build
+      chown build /nix
+
+      sudo -u build curl -L https://nixos.org/nix/install > install
+      sudo -u build sh install
+
+      echo "export PATH=/nix/var/nix/profiles/per-user/build/profile/bin:''$PATH" >> /etc/profile
+
+      mkdir /etc/nix
+      echo 'experimental-features = nix-command flakes' >> /etc/nix/nix.conf
+
+      export nix_user_config_file="/home/build/.local/share/nix/trusted-settings.json"
+      mkdir -p $(dirname \\$nix_user_config_file)
+      echo '{"extra-experimental-features":{"nix-command flakes":true},"extra-substituters":{"https://nix-dram.cachix.org https://dram.cachix.org  https://nrdxp.cachix.org https://nix-community.cachix.org":true},"extra-trusted-public-keys":{"nix-dram.cachix.org-1:CKjZ0L1ZiqH3kzYAZRt8tg8vewAx5yj8Du/+iR8Efpg= dram.cachix.org-1:baoy1SXpwYdKbqdTbfKGTKauDDeDlHhUpC+QuuILEMY= nrdxp.cachix.org-1:Fc5PSqY2Jm1TrWfm88l6cvGWwz3s93c6IOifQWnhNW4= nix-community.cachix.org-1:mB9FSh9qf2dCimDSUo8Zy7bkq5CX+/rkCWyvRCYg3Fs=":true}}' > \\$nix_user_config_file
+      chown -R build /home/build/
+
+      curl -L https://github.com/drone-runners/drone-runner-exec/releases/latest/download/drone_runner_exec_linux_amd64.tar.gz | tar xz
+      sudo install -t /usr/local/bin drone-runner-exec
+    '';
+  };
+
+  startup = pkgs.writeScript "startup.sh" ''
+    chown build /nix
+
+    if [ ! -f /run/vars ]; then
+      exit 1
+    fi
+
+    cp -a /run/vars /run/runtime-vars
+    env | grep "DRONE" >> /run/runtime-vars
+
+    su - -s /bin/bash build sh -c "/usr/local/bin/drone-runner-exec daemon /run/runtime-vars"
+  '';
+
   psCfg = config.pub-solar;
   cfg = config.pub-solar.ci-runner;
 in
 {
   options.pub-solar.ci-runner = {
-    enable = mkEnableOption "Enables a systemd service that runs drone-ci-runner";
-  };
+    enable = lib.mkEnableOption "Enables a docker container running a drone exec runner as unprivileged user.";
 
-  config = mkIf cfg.enable {
-    systemd.user.services.ci-runner = {
-      enable = true;
-
-      description = "CI runner for the PubSolarOS repository that can run test VM instances with KVM.";
-
-      serviceConfig = {
-        Type = "simple";
-        Restart = "always";
-      };
-
-      path = [
-        pkgs.git
-        pkgs.nix
-        pkgs.libvirt
-      ];
-
-      wantedBy = [ "multi-user.target" ];
-      after = [ "network.target" "libvirtd.service" ];
-
-      script = ''${pkgs.drone-runner-exec}/bin/drone-runner-exec daemon /run/agenix/drone-runner-exec-config'';
+    enableKvm = lib.mkOption {
+      description = ''
+        Enable kvm support.
+      '';
+      default = true;
+      type = types.bool;
     };
 
-    age.secrets."drone-runner-exec-config" = {
-      file = "${self}/secrets/drone-runner-exec-config";
-      mode = "700";
-      owner = psCfg.user.name;
+    nixCacheLocation = lib.mkOption {
+      description = ''
+        Location of nix cache that is shared between builds
+      '';
+      type = types.path;
+    };
+
+    runnerEnvironment = lib.mkOption {
+      description = ''
+        Additional environment variables added to the vars file on container runtime
+      '';
+      default = {};
+    };
+
+    runnerVarsFile = lib.mkOption {
+      description = ''
+        Location of vars file passed to drone runner
+      '';
+      type = types.path;
+    };
+  };
+
+  config = lib.mkIf cfg.enable {
+    virtualisation = {
+      docker = {
+        enable = true; # sadly podman is not supported rightnow
+      };
+
+      oci-containers = {
+        backend = "docker";
+        containers."drone-exec-runner" = {
+          image = runnerImageName;
+          imageFile = runnerImage;
+          autoStart = true;
+          entrypoint = "bash";
+          cmd = [ "/startup.sh" ];
+
+          volumes = [
+            "${cfg.runnerVarsFile}:/run/vars"
+            "${cfg.nixCacheLocation}:/nix"
+            "${startup}:/startup.sh"
+          ];
+
+          environment = cfg.runnerEnvironment;
+
+          extraOptions = lib.mkIf cfg.enableKvm [ "--device=/dev/kvm" ];
+        };
+      };
     };
   };
 }