1 files changed, 51 insertions, 0 deletions
diff --git a/krebs/3modules/systemd.nix b/krebs/3modules/systemd.nix
new file mode 100644
index 000000000..c30b2264a
--- /dev/null
+++ b/krebs/3modules/systemd.nix
@@ -0,0 +1,51 @@
+{ config, options, pkgs, ... }: let {
+  lib = import ../../lib;
+
+  body.options.krebs.systemd.services = lib.mkOption {
+    default = {};
+    type = lib.types.attrs;
+    description = ''
+      Definition of systemd service units with bonus features.
+
+      Services defined using this option will be restarted whenever any file
+      (described by an absolute path) used in LoadCredential changes.
+    '';
+  };
+
+  body.config.systemd =
+    lib.mkMerge
+      (lib.flatten
+        (lib.mapAttrsToList (serviceName: cfg: let
+          prefix = [ "krebs" "systemd" "services" serviceName ];
+          opts = options.systemd.services.type.getSubOptions prefix;
+
+          paths =
+            lib.filter
+              lib.types.absolute-pathname.check
+              (map
+                (lib.compose [ lib.maybeHead (lib.match "[^:]*:(.*)") ])
+                (cfg.serviceConfig.LoadCredential or []));
+        in
+          lib.singleton {
+            services.${serviceName} = cfg;
+          }
+          ++
+          lib.optionals (cfg.enable or opts.enable.default) (map (path: let
+            triggerName = "trigger-${lib.systemd.encodeName path}";
+          in {
+            paths.${triggerName} = {
+              wantedBy = ["multi-user.target"];
+              pathConfig.PathChanged = path;
+            };
+            services.${triggerName} = {
+              serviceConfig = {
+                Type = "oneshot";
+                ExecStart = lib.singleton (toString [
+                  "${pkgs.systemd}/bin/systemctl restart"
+                  (lib.shell.escape serviceName)
+                ]);
+              };
+            };
+          }) paths)
+        ) config.krebs.systemd.services));
+}