Commit 5d7f6440 authored by Gaute Ravndal's avatar Gaute Ravndal
Browse files

nixos/man-db: add option to generate cache at runtime 

Enables faster and fully asynchronous generation of the cache at runtime
by maintaining a separate copy of `cfg.manualPages` with appropriate
timestamps so that mandb can pick up relevant changes without having to
re-generate the full cache on nearly every system rebuild.
parent 3fff19ce

nixos/modules/misc/documentation.nix

+10 −0
Original line number Diff line number Diff line
@@ -277,6 +277,16 @@ in 
        '';

      };



      man.cache.generateAtRuntime = mkOption {

        type = types.bool;

        default = false;

        description = ''

          Whether to generate the manual page index caches at runtime using

          a systemd service. Note that this is currently only supported by the

          man-db module.

        '';

      };



      info.enable = mkOption {

        type = types.bool;

        default = true;

nixos/modules/misc/man-db.nix

+74 −35
Original line number Diff line number Diff line
@@ -7,13 +7,14 @@ 


let

  cfg = config.documentation.man.man-db;

  cfgm = config.documentation.man;

in



{

  options = {

    documentation.man.man-db = {

      enable = lib.mkEnableOption "man-db as the default man page viewer" // {

        default = config.documentation.man.enable;

        default = cfgm.enable;

        defaultText = lib.literalExpression "config.documentation.man.enable";

        example = false;

      };
@@ -65,7 +66,9 @@ in 
    )

  ];



  config = lib.mkIf cfg.enable {

  config = lib.mkIf cfg.enable (

    lib.mkMerge [

      {

        environment.systemPackages = [ cfg.package ];

        environment.etc."man_db.conf".text =

          let
@@ -79,6 +82,7 @@ in 
                pkgs.buildPackages.man-db;



            manualCache =

              if (!cfgm.cache.generateAtRuntime) then

                pkgs.runCommand "man-cache"

                  {

                    nativeBuildInputs = [ buildPackage ];
@@ -87,19 +91,54 @@ in 
                  ''

                    echo "MANDB_MAP ${cfg.manualPages}/share/man $out" > man.conf

                    mandb -C man.conf -pscq

            '';

                  ''

              else

                "/var/cache/man/nixos-mandb";

          in

          ''

            # Manual pages paths for NixOS

            MANPATH_MAP /run/current-system/sw/bin /run/current-system/sw/share/man

            MANPATH_MAP /run/wrappers/bin          /run/current-system/sw/share/man



        ${lib.optionalString config.documentation.man.cache.enable ''

          # Generated manual pages cache for NixOS (immutable)

            ${lib.optionalString cfgm.cache.enable ''

              # Manual pages caches for NixOS

              MANDB_MAP /run/current-system/sw/share/man ${manualCache}

            ''}

        # Manual pages caches for NixOS

        MANDB_MAP /run/current-system/sw/share/man /var/cache/man/nixos

          '';

      }



      (lib.mkIf (cfgm.enable && cfgm.cache.generateAtRuntime) {

        users.users.mandb = {

          isSystemUser = true;

          group = "mandb";

        };

        users.groups.mandb = { };



        systemd.services.mandb = {

          path = [

            cfg.package

            pkgs.rsync

          ];

          script = ''

            rsync \

              --checksum --recursive --copy-links --delete --no-times --no-perms --chmod=+w \

              ${cfg.manualPages}/share/man/ "$CACHE_DIRECTORY/nixos-manpages"



            echo "MANDB_MAP $CACHE_DIRECTORY/nixos-manpages $CACHE_DIRECTORY/nixos-mandb" \

              > "$RUNTIME_DIRECTORY/man.conf"



            mandb -C "$RUNTIME_DIRECTORY/man.conf" -q

          '';

          serviceConfig = {

            CacheDirectory = "man";

            RuntimeDirectory = "mandb";

            User = "mandb";

            BindReadOnlyPaths = [ "/dev/null:/etc/man_db.conf" ]; # mandb will still read /etc/man_db.conf if it exists, even when setting -C path/to/config.conf

            ProtectSystem = "strict";

          };

          wantedBy = [ "default.target" ];

        };

      })

    ]

  );

}