process: report owner label as DOMAIN\user (#2515)

Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>
Signed-off-by: Jan-Otto Kröpke <mail@jkroepke.de>

internal/collector/process/process.go

@@ -483,7 +483,7 @@ func (c *Collector) getProcessOwner(logger *slog.Logger, hProcess windows.Handle
 		if err != nil {
 			owner = sid
 		} else {
-			owner = fmt.Sprintf(`%s\%s`, account, domain)
+			owner = fmt.Sprintf(`%s\%s`, domain, account)
 		}
 
 		c.lookupCache.Store(sid, owner)

internal/collector/process/process_internal_test.go

@@ -0,0 +1,41 @@
+// SPDX-License-Identifier: Apache-2.0
+//
+// Copyright The Prometheus Authors
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+//go:build windows
+
+package process
+
+import (
+	"log/slog"
+	"os/user"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+	"golang.org/x/sys/windows"
+)
+
+// The owner label must use the Windows DOMAIN\user form, as os/user reports it.
+func TestGetProcessOwner(t *testing.T) {
+	t.Parallel()
+
+	currentUser, err := user.Current()
+	require.NoError(t, err)
+
+	c := &Collector{}
+
+	owner, err := c.getProcessOwner(slog.New(slog.DiscardHandler), windows.CurrentProcess())
+	require.NoError(t, err)
+	require.Equal(t, currentUser.Username, owner)
+}