Prototype of multi-agents module for nix-darwin

flake.nix

@@ -194,6 +194,31 @@
               };
             };
 
+          darwinModules.multi-agent-service =
+            { lib, pkgs, ...}:
+            {
+              _file = "${toString ./flake.nix}#darwinModules.multi-agent-service";
+              imports = [
+                agentFromFlakeModule_multi
+                ./internal/nix/nix-darwin/multi.nix
+              ];
+
+              # This module replaces what's provided by nix-darwin
+              disabledModules = [ "services/hercules-ci-agent" ];
+
+              options = let inherit (lib) types mkOption; in
+                {
+                  services.hercules-ci-agents =
+                    mkOption {
+                      type = types.attrsOf (
+                        types.submoduleWith {
+                          modules = [{ config.settings.labels.module = "darwin-multi-service"; }];
+                        }
+                      );
+                    };
+                };
+            };
+
           # A nix-darwin module with more defaults set for machines that serve as agents
           darwinModules.agent-profile =
             { lib, pkgs, ... }:

internal/nix/nix-darwin/multi.nix

@@ -0,0 +1,167 @@
+# Module similar to (flake).agent-service or the NixOS-bundled module, but
+# supports running multiple instance of the agent, each with their own files,
+# user, etc.
+
+systemArgs@{ pkgs, config, lib, ... }:
+let
+  inherit (lib) mkIf mkDefault types mkOption;
+  inherit (lib.strings) match;
+  topConfig = config;
+  literalDocBook = lib.literalDocBook or lib.literalExample;
+  literalExpression = lib.literalExpression or lib.literalExample;
+
+  submodule = { config, options, name, ... }:
+    let
+      inherit (import ../settings.nix { inherit pkgs lib; }) format makeSettingsOptions;
+      configFile = format.generate "hercules-ci-agent${suffix}.json" config.settings;
+      command = "${config.package}/bin/hercules-ci-agent --config ${configFile}";
+      testCommand = "${command} --test-configuration";
+      suffix = if name == "" then "" else "-${name}";
+      user = topConfig.users.users.${config.user};
+    in
+    {
+      options = {
+        systemConfig = lib.mkOption {
+          internal = true;
+          type = types.unspecified; # A function from module arguments to config.
+        };
+        package = mkOption {
+          description = ''
+            Package containing the bin/hercules-ci-agent executable.
+          '';
+          type = types.package;
+          default = pkgs.hercules-ci-agent;
+          defaultText = literalExpression "pkgs.hercules-ci-agent";
+        };
+        user = mkOption {
+          type = types.str;
+          default = "_hercules-ci-agent";
+        };
+        group = mkOption {
+          type = types.str;
+          default = "_hercules-ci-agent";
+        };
+        logFile = mkOption {
+          type = types.str;
+          default = "/var/log/hci-agent${suffix}.log";
+        };
+        baseDirectory = mkOption {
+          type = types.str;
+          default = "/var/lib/hercules-ci-agent${if name == "" then "" else "/${name}"}"; # Almost a `suffix` logic, but yield subdir
+        };
+      } // makeSettingsOptions { cfg = config; opt = options; };
+      config = let cfg = config; in
+        {
+          settings = {
+            _module.args = {
+              packageOption = options.package;
+              inherit pkgs;
+            };
+            baseDirectory = cfg.baseDirectory;
+            nixUserIsTrusted = true;
+            labels =
+              let
+                mkIfNotNull = x: mkIf (x != null) x;
+              in
+              {
+                darwin.label = topConfig.system.darwinLabel;
+                darwin.revision = topConfig.system.darwinRevision;
+                darwin.version = topConfig.system.darwinVersion;
+                darwin.nix.daemon = topConfig.nix.useDaemon;
+                darwin.nix.sandbox = topConfig.nix.settings.sandbox;
+              };
+          };
+          systemConfig = { config, ... }: {
+            launchd.daemons."hci-agent${suffix}" = {
+              script = "exec ${command}";
+
+              path = [ config.nix.package ];
+              environment = {
+                NIX_SSL_CERT_FILE = "${pkgs.cacert}/etc/ssl/certs/ca-bundle.crt";
+              };
+
+              serviceConfig.KeepAlive = true;
+              serviceConfig.RunAtLoad = true;
+              serviceConfig.StandardErrorPath = cfg.logFile;
+              serviceConfig.StandardOutPath = cfg.logFile;
+              serviceConfig.GroupName = cfg.user;
+              serviceConfig.UserName = cfg.group;
+              serviceConfig.WorkingDirectory = cfg.baseDirectory;
+              serviceConfig.WatchPaths = [
+                cfg.settings.staticSecretsDirectory
+              ];
+            };
+
+            nix.settings.trusted-users = [ cfg.user ];
+
+            system.activationScripts.preActivation.text = ''
+              touch '${cfg.logFile}'
+              chown ${toString user.uid}:${toString user.gid} '${cfg.logFile}'
+              if ! test -d ${cfg.baseDirectory}; then
+                mkdir -p ${cfg.baseDirectory}
+                chown ${toString user.uid}:${toString user.gid} ${cfg.baseDirectory}
+              fi
+            '';
+          };
+        };
+    };
+
+  mergeSub =
+    f: lib.mkMerge (map (sub: f (sub.systemConfig systemArgs)) (lib.attrValues config.services.hercules-ci-agents));
+in
+{
+  options = {
+    services.hercules-ci-agents = lib.mkOption {
+      type = types.attrsOf (types.submoduleWith {
+        modules = [ submodule ];
+      });
+      default = { };
+      description = ''
+        Multiple instances of hercules-ci-agent can be specified.
+
+        If you specify an instance named `""`, it will behave just as the `services.hercules-ci-agent` options did.
+        - User: `hercules-ci-agent`
+        - Default base directory: `/var/lib/hercules-ci-agent`
+
+        Otherwise:
+        - User: `hercules-ci-agent` (on darwin we use same username)
+        - Default base directory: `/var/lib/hercules-ci-agent-''${name}`
+      '';
+    };
+  };
+
+  config = lib.mkMerge [
+    {
+      nix = mergeSub (c: c.nix);
+      launchd = mergeSub (c: c.launchd);
+      system = mergeSub (c: c.system);
+    }
+    {
+      nix.extraOptions = lib.mkIf (config.services.hercules-ci-agents != { }) ''
+        # A store path that was missing at first may well have finished building,
+        # even shortly after the previous lookup. This *also* applies to the daemon.
+        narinfo-cache-negative-ttl = 0
+      '';
+
+      users.knownGroups = [ "hercules-ci-agent" "_hercules-ci-agent" ];
+      users.knownUsers = [ "hercules-ci-agent" "_hercules-ci-agent" ];
+
+      users.users._hercules-ci-agent = {
+        uid = mkDefault 399;
+        gid = mkDefault config.users.groups._hercules-ci-agent.gid;
+        home = mkDefault "/var/lib/hercules-ci-agent";
+        name = "_hercules-ci-agent";
+        createHome = true;
+        shell = "/bin/bash";
+        description = "System user for the Hercules CI Agent";
+      };
+      users.groups._hercules-ci-agent = {
+        gid = mkDefault 32001;
+        name = "_hercules-ci-agent";
+        description = "System group for the Hercules CI Agent";
+      };
+    }
+  ];
+
+  meta.maintainers = [ ];
+}