nixos/pgbackup: Fix and refactor the postgres backup module

nixos/modules/rename.nix

@@ -197,6 +197,12 @@ with lib;
     (mkRenamedOptionModule [ "fonts" "fontconfig" "ultimate" "forceAutohint" ] [ "fonts" "fontconfig" "forceAutohint" ])
     (mkRenamedOptionModule [ "fonts" "fontconfig" "ultimate" "renderMonoTTFAsBitmap" ] [ "fonts" "fontconfig" "renderMonoTTFAsBitmap" ])
 
+    # postgresqlBackup
+    (mkRemovedOptionModule [ "services" "postgresqlBackup" "period" ] ''
+       A systemd timer is now used instead of cron.
+       The starting time can be configured via <literal>services.postgresqlBackup.startAt</literal>.
+    '')
+
     # Profile splitting
     (mkRenamedOptionModule [ "virtualization" "growPartition" ] [ "boot" "growPartition" ])
 

nixos/modules/services/backup/postgresql-backup.nix

@@ -3,18 +3,41 @@
 with lib;
 
 let
-  inherit (pkgs) gzip;
 
-  location = config.services.postgresqlBackup.location;
+  cfg = config.services.postgresqlBackup;
 
-  postgresqlBackupCron = db:
-    ''
-      ${config.services.postgresqlBackup.period} root ${config.services.postgresql.package}/bin/pg_dump ${db} | ${gzip}/bin/gzip -c > ${location}/${db}.gz
-    '';
+  postgresqlBackupService = db :
+    {
+      enable = true;
 
-in
+      description = "Backup of database ${db}";
 
-{
+      requires = [ "postgresql.service" ];
+
+      preStart = ''
+        mkdir -m 0700 -p ${cfg.location}
+        chown postgres ${cfg.location}
+      '';
+
+      script = ''
+        if [ -e ${cfg.location}/${db}.sql.gz ]; then
+          ${pkgs.coreutils}/bin/mv ${cfg.location}/${db}.sql.gz ${cfg.location}/${db}.prev.sql.gz
+        fi
+
+        ${config.services.postgresql.package}/bin/pg_dump ${cfg.pgdumpOptions} ${db} | \
+          ${pkgs.gzip}/bin/gzip -c > ${cfg.location}/${db}.sql.gz
+      '';
+
+      serviceConfig = {
+        Type = "oneshot";
+        PermissionsStartOnly = "true";
+        User = "postgres";
+      };
+
+      startAt = cfg.startAt;
+    };
+
+in {
 
   options = {
 
@@ -27,10 +50,10 @@ in
         '';
       };
 
-      period = mkOption {
-        default = "15 01 * * *";
+      startAt = mkOption {
+        default = "*-*-* 01:15:00";
         description = ''
-          This option defines (in the format used by cron) when the
+          This option defines (see <literal>systemd.time</literal> for format) when the
           databases should be dumped.
           The default is to update at 01:15 (at night) every day.
         '';
@@ -49,18 +72,23 @@ in
           Location to put the gzipped PostgreSQL database dumps.
         '';
       };
+
+      pgdumpOptions = mkOption {
+        type = types.string;
+        default = "-Cbo";
+        description = ''
+          Command line options for pg_dump.
+        '';
+      };
     };
 
   };
 
   config = mkIf config.services.postgresqlBackup.enable {
-    services.cron.systemCronJobs = map postgresqlBackupCron config.services.postgresqlBackup.databases;
 
-    system.activationScripts.postgresqlBackup = stringAfter [ "stdio" "users" ]
-      ''
-        mkdir -m 0700 -p ${config.services.postgresqlBackup.location}
-        chown root ${config.services.postgresqlBackup.location}
-      '';
+    systemd.services = listToAttrs (map (db : {
+          name = "postgresqlBackup-${db}";
+          value = postgresqlBackupService db; } ) cfg.databases);
   };
 
 }

nixos/tests/postgresql.nix

@@ -26,6 +26,9 @@ let
       {
         services.postgresql.package=postgresql-package;
         services.postgresql.enable = true;
+
+        services.postgresqlBackup.enable = true;
+        services.postgresqlBackup.databases = [ "postgres" ];
       };
 
     testScript = ''
@@ -46,6 +49,10 @@ let
       $machine->succeed(check_count("SELECT * FROM sth;", 5));
       $machine->fail(check_count("SELECT * FROM sth;", 4));
       $machine->succeed(check_count("SELECT xpath(\'/test/text()\', doc) FROM xmltest;", 1));
+
+      # Check backup service
+      $machine->succeed("systemctl start postgresqlBackup-postgres.service");
+      $machine->succeed("zcat /var/backup/postgresql/postgres.sql.gz | grep '<test>ok</test>'");
       $machine->shutdown;
     '';