nixos: systemd: split off helper functions into systemd-lib

nixos/lib/systemd-lib.nix

@@ -5,6 +5,7 @@ with lib;
 let
   cfg = config.systemd;
   lndir = "${pkgs.buildPackages.xorg.lndir}/bin/lndir";
+  systemd = cfg.package;
 in rec {
 
   shellEscape = s: (replaceChars [ "\\" ] [ "\\\\" ] s);
@@ -235,4 +236,205 @@ in rec {
       ''}
     ''; # */
 
+  makeJobScript = name: text:
+    let
+      scriptName = replaceChars [ "\\" "@" ] [ "-" "_" ] (shellEscape name);
+      out = (pkgs.writeShellScriptBin scriptName ''
+        set -e
+        ${text}
+      '').overrideAttrs (_: {
+        # The derivation name is different from the script file name
+        # to keep the script file name short to avoid cluttering logs.
+        name = "unit-script-${scriptName}";
+      });
+    in "${out}/bin/${scriptName}";
+
+  unitConfig = { config, options, ... }: {
+    config = {
+      unitConfig =
+        optionalAttrs (config.requires != [])
+          { Requires = toString config.requires; }
+        // optionalAttrs (config.wants != [])
+          { Wants = toString config.wants; }
+        // optionalAttrs (config.after != [])
+          { After = toString config.after; }
+        // optionalAttrs (config.before != [])
+          { Before = toString config.before; }
+        // optionalAttrs (config.bindsTo != [])
+          { BindsTo = toString config.bindsTo; }
+        // optionalAttrs (config.partOf != [])
+          { PartOf = toString config.partOf; }
+        // optionalAttrs (config.conflicts != [])
+          { Conflicts = toString config.conflicts; }
+        // optionalAttrs (config.requisite != [])
+          { Requisite = toString config.requisite; }
+        // optionalAttrs (config.restartTriggers != [])
+          { X-Restart-Triggers = toString config.restartTriggers; }
+        // optionalAttrs (config.reloadTriggers != [])
+          { X-Reload-Triggers = toString config.reloadTriggers; }
+        // optionalAttrs (config.description != "") {
+          Description = config.description; }
+        // optionalAttrs (config.documentation != []) {
+          Documentation = toString config.documentation; }
+        // optionalAttrs (config.onFailure != []) {
+          OnFailure = toString config.onFailure; }
+        // optionalAttrs (options.startLimitIntervalSec.isDefined) {
+          StartLimitIntervalSec = toString config.startLimitIntervalSec;
+        } // optionalAttrs (options.startLimitBurst.isDefined) {
+          StartLimitBurst = toString config.startLimitBurst;
+        };
+    };
+  };
+
+  serviceConfig = { name, config, ... }: {
+    config = mkMerge
+      [ { # Default path for systemd services.  Should be quite minimal.
+          path = mkAfter
+            [ pkgs.coreutils
+              pkgs.findutils
+              pkgs.gnugrep
+              pkgs.gnused
+              systemd
+            ];
+          environment.PATH = "${makeBinPath config.path}:${makeSearchPathOutput "bin" "sbin" config.path}";
+        }
+        (mkIf (config.preStart != "")
+          { serviceConfig.ExecStartPre =
+              [ (makeJobScript "${name}-pre-start" config.preStart) ];
+          })
+        (mkIf (config.script != "")
+          { serviceConfig.ExecStart =
+              makeJobScript "${name}-start" config.script + " " + config.scriptArgs;
+          })
+        (mkIf (config.postStart != "")
+          { serviceConfig.ExecStartPost =
+              [ (makeJobScript "${name}-post-start" config.postStart) ];
+          })
+        (mkIf (config.reload != "")
+          { serviceConfig.ExecReload =
+              makeJobScript "${name}-reload" config.reload;
+          })
+        (mkIf (config.preStop != "")
+          { serviceConfig.ExecStop =
+              makeJobScript "${name}-pre-stop" config.preStop;
+          })
+        (mkIf (config.postStop != "")
+          { serviceConfig.ExecStopPost =
+              makeJobScript "${name}-post-stop" config.postStop;
+          })
+      ];
+  };
+
+  mountConfig = { config, ... }: {
+    config = {
+      mountConfig =
+        { What = config.what;
+          Where = config.where;
+        } // optionalAttrs (config.type != "") {
+          Type = config.type;
+        } // optionalAttrs (config.options != "") {
+          Options = config.options;
+        };
+    };
+  };
+
+  automountConfig = { config, ... }: {
+    config = {
+      automountConfig =
+        { Where = config.where;
+        };
+    };
+  };
+
+  commonUnitText = def: ''
+      [Unit]
+      ${attrsToSection def.unitConfig}
+    '';
+
+  targetToUnit = name: def:
+    { inherit (def) aliases wantedBy requiredBy enable;
+      text =
+        ''
+          [Unit]
+          ${attrsToSection def.unitConfig}
+        '';
+    };
+
+  serviceToUnit = name: def:
+    { inherit (def) aliases wantedBy requiredBy enable;
+      text = commonUnitText def +
+        ''
+          [Service]
+          ${let env = cfg.globalEnvironment // def.environment;
+            in concatMapStrings (n:
+              let s = optionalString (env.${n} != null)
+                "Environment=${builtins.toJSON "${n}=${env.${n}}"}\n";
+              # systemd max line length is now 1MiB
+              # https://github.com/systemd/systemd/commit/e6dde451a51dc5aaa7f4d98d39b8fe735f73d2af
+              in if stringLength s >= 1048576 then throw "The value of the environment variable ‘${n}’ in systemd service ‘${name}.service’ is too long." else s) (attrNames env)}
+          ${if def.reloadIfChanged then ''
+            X-ReloadIfChanged=true
+          '' else if !def.restartIfChanged then ''
+            X-RestartIfChanged=false
+          '' else ""}
+          ${optionalString (!def.stopIfChanged) "X-StopIfChanged=false"}
+          ${attrsToSection def.serviceConfig}
+        '';
+    };
+
+  socketToUnit = name: def:
+    { inherit (def) aliases wantedBy requiredBy enable;
+      text = commonUnitText def +
+        ''
+          [Socket]
+          ${attrsToSection def.socketConfig}
+          ${concatStringsSep "\n" (map (s: "ListenStream=${s}") def.listenStreams)}
+          ${concatStringsSep "\n" (map (s: "ListenDatagram=${s}") def.listenDatagrams)}
+        '';
+    };
+
+  timerToUnit = name: def:
+    { inherit (def) aliases wantedBy requiredBy enable;
+      text = commonUnitText def +
+        ''
+          [Timer]
+          ${attrsToSection def.timerConfig}
+        '';
+    };
+
+  pathToUnit = name: def:
+    { inherit (def) aliases wantedBy requiredBy enable;
+      text = commonUnitText def +
+        ''
+          [Path]
+          ${attrsToSection def.pathConfig}
+        '';
+    };
+
+  mountToUnit = name: def:
+    { inherit (def) aliases wantedBy requiredBy enable;
+      text = commonUnitText def +
+        ''
+          [Mount]
+          ${attrsToSection def.mountConfig}
+        '';
+    };
+
+  automountToUnit = name: def:
+    { inherit (def) aliases wantedBy requiredBy enable;
+      text = commonUnitText def +
+        ''
+          [Automount]
+          ${attrsToSection def.automountConfig}
+        '';
+    };
+
+  sliceToUnit = name: def:
+    { inherit (def) aliases wantedBy requiredBy enable;
+      text = commonUnitText def +
+        ''
+          [Slice]
+          ${attrsToSection def.sliceConfig}
+        '';
+    };
 }