nixos/redis: unbreak module

The redis module currently fails to start up, most likely due to running
a chown as non-root in preStart.

While at it, I hardcoded it to use systemd's StateDirectory and
DynamicUser to manage directory permissions, removed the unused
appendOnlyFilename option, and the pidFile option.

We properly tell redis now it's daemonized, and it'll use notify support
to signal readiness.

nixos/modules/services/databases/redis.nix

@@ -8,17 +8,19 @@ let
   condOption = name: value: if value != null then "${name} ${toString value}" else "";
 
   redisConfig = pkgs.writeText "redis.conf" ''
-    pidfile ${cfg.pidFile}
     port ${toString cfg.port}
     ${condOption "bind" cfg.bind}
     ${condOption "unixsocket" cfg.unixSocket}
+    daemonize yes
+    supervised systemd
     loglevel ${cfg.logLevel}
     logfile ${cfg.logfile}
     syslog-enabled ${redisBool cfg.syslog}
+    pidfile /run/redis/redis.pid
     databases ${toString cfg.databases}
     ${concatMapStrings (d: "save ${toString (builtins.elemAt d 0)} ${toString (builtins.elemAt d 1)}\n") cfg.save}
-    dbfilename ${cfg.dbFilename}
-    dir ${toString cfg.dbpath}
+    dbfilename dump.rdb
+    dir /var/lib/redis
     ${if cfg.slaveOf != null then "slaveof ${cfg.slaveOf.ip} ${toString cfg.slaveOf.port}" else ""}
     ${condOption "masterauth" cfg.masterAuth}
     ${condOption "requirepass" cfg.requirePass}
@@ -55,18 +57,6 @@ in
         description = "Which Redis derivation to use.";
       };
 
-      user = mkOption {
-        type = types.str;
-        default = "redis";
-        description = "User account under which Redis runs.";
-      };
-
-      pidFile = mkOption {
-        type = types.path;
-        default = "/var/lib/redis/redis.pid";
-        description = "";
-      };
-
       port = mkOption {
         type = types.int;
         default = 6379;
@@ -100,7 +90,7 @@ in
         type = with types; nullOr path;
         default = null;
         description = "The path to the socket to bind to.";
-        example = "/run/redis.sock";
+        example = "/run/redis/redis.sock";
       };
 
       logLevel = mkOption {
@@ -136,18 +126,6 @@ in
         example = [ [900 1] [300 10] [60 10000] ];
       };
 
-      dbFilename = mkOption {
-        type = types.str;
-        default = "dump.rdb";
-        description = "The filename where to dump the DB.";
-      };
-
-      dbpath = mkOption {
-        type = types.path;
-        default = "/var/lib/redis";
-        description = "The DB will be written inside this directory, with the filename specified using the 'dbFilename' configuration.";
-      };
-
       slaveOf = mkOption {
         default = null; # { ip, port }
         description = "An attribute set with two attributes: ip and port to which this redis instance acts as a slave.";
@@ -175,12 +153,6 @@ in
         description = "By default data is only periodically persisted to disk, enable this option to use an append-only file for improved persistence.";
       };
 
-      appendOnlyFilename = mkOption {
-        type = types.str;
-        default = "appendonly.aof";
-        description = "Filename for the append-only file (stored inside of dbpath)";
-      };
-
       appendFsync = mkOption {
         type = types.str;
         default = "everysec"; # no, always, everysec
@@ -222,19 +194,15 @@ in
       allowedTCPPorts = [ cfg.port ];
     };
 
-    users.users.redis =
-      { name = cfg.user;
-        description = "Redis database user";
-      };
+    users.users.redis.description = "Redis database user";
 
     environment.systemPackages = [ cfg.package ];
 
     systemd.services.disable-transparent-huge-pages = {
-      enable = config.services.redis.enable;
       description = "Disable Transparent Huge Pages (required by Redis)";
       before = [ "redis.service" ];
       wantedBy = [ "redis.service" ];
-      script = "echo never >/sys/kernel/mm/transparent_hugepage/enabled";
+      script = "echo never > /sys/kernel/mm/transparent_hugepage/enabled";
       serviceConfig.Type = "oneshot";
     };
 
@@ -244,14 +212,12 @@ in
         wantedBy = [ "multi-user.target" ];
         after = [ "network.target" ];
 
-        preStart = ''
-          install -d -m0700 -o ${cfg.user} ${cfg.dbpath}
-          chown -R ${cfg.user} ${cfg.dbpath}
-        '';
-
         serviceConfig = {
           ExecStart = "${cfg.package}/bin/redis-server ${redisConfig}";
-          User = cfg.user;
+          RuntimeDirectory = "redis";
+          StateDirectory = "redis";
+          Type = "notify";
+          User = "redis";
         };
       };