nixos/hydra: add system-hydra.slice, fix typo (#338532)

nixos/modules/services/continuous-integration/hydra/default.nix

@@ -246,7 +246,7 @@ in
       }
       {
         assertion = cfg.minSpareServers < cfg.maxSpareServers;
-        message = "services.hydra.minSpareServers cannot be bigger than servives.hydra.maxSpareServers";
+        message = "services.hydra.minSpareServers cannot be bigger than services.hydra.maxSpareServers";
       }
     ];
 
@@ -311,6 +311,11 @@ in
       )
     ];
 
+    systemd.slices.system-hydra = {
+      description = "Hydra Slice";
+      documentation = [ "file://${cfg.package}/share/doc/hydra/index.html" "https://nixos.org/hydra/manual/" ];
+    };
+
     systemd.services.hydra-init =
       { wantedBy = [ "multi-user.target" ];
         requires = lib.optional haveLocalDB "postgresql.service";
@@ -371,6 +376,7 @@ in
         serviceConfig.User = "hydra";
         serviceConfig.Type = "oneshot";
         serviceConfig.RemainAfterExit = true;
+        serviceConfig.Slice = "system-hydra.slice";
       };
 
     systemd.services.hydra-server =
@@ -389,6 +395,7 @@ in
             User = "hydra-www";
             PermissionsStartOnly = true;
             Restart = "always";
+            Slice = "system-hydra.slice";
           };
       };
 
@@ -408,6 +415,7 @@ in
             ExecStopPost = "${hydra-package}/bin/hydra-queue-runner --unlock";
             User = "hydra-queue-runner";
             Restart = "always";
+            Slice = "system-hydra.slice";
 
             # Ensure we can get core dumps.
             LimitCORE = "infinity";
@@ -430,6 +438,7 @@ in
             User = "hydra";
             Restart = "always";
             WorkingDirectory = baseDir;
+            Slice = "system-hydra.slice";
           };
       };
 
@@ -442,6 +451,7 @@ in
         serviceConfig =
           { ExecStart = "@${hydra-package}/bin/hydra-update-gc-roots hydra-update-gc-roots";
             User = "hydra";
+            Slice = "system-hydra.slice";
           };
         startAt = "2,14:15";
       };
@@ -455,6 +465,7 @@ in
         serviceConfig =
           { ExecStart = "@${hydra-package}/bin/hydra-send-stats hydra-send-stats";
             User = "hydra";
+            Slice = "system-hydra.slice";
           };
       };
 
@@ -474,6 +485,7 @@ in
             User = "hydra-queue-runner";
             Restart = "always";
             RestartSec = 5;
+            Slice = "system-hydra.slice";
           };
       };
 
@@ -492,6 +504,7 @@ in
             fi
           '';
         startAt = "*:0/5";
+        serviceConfig.Slice = "system-hydra.slice";
       };
 
     # Periodically compress build logs. The queue runner compresses
@@ -509,6 +522,7 @@ in
             find ${baseDir}/build-logs -type f -name "*.drv" -mtime +3 -size +0c | xargs -r $compression --force --quiet
           '';
         startAt = "Sun 01:45";
+        serviceConfig.Slice = "system-hydra.slice";
       };
 
     services.postgresql.enable = lib.mkIf haveLocalDB true;