pdh: preserve legitimate instances ending in _Total (#2588)

Signed-off-by: Jan-Otto Kröpke <mail@jkroepke.de>

internal/pdh/instance_total.go

@@ -0,0 +1,45 @@
+// 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 pdh
+
+import (
+	"strconv"
+	"strings"
+)
+
+// IsTotalInstance identifies aggregate instances without discarding ordinary
+// application names ending in _Total. Processor Information also publishes
+// processor-group aggregates named <group>,_Total.
+func IsTotalInstance(object, instance string) bool {
+	if instance == InstanceTotal {
+		return true
+	}
+
+	if !strings.EqualFold(object, "Processor Information") {
+		return false
+	}
+
+	group, ok := strings.CutSuffix(instance, ","+InstanceTotal)
+	if !ok {
+		return false
+	}
+
+	_, err := strconv.ParseUint(group, 10, 32)
+
+	return err == nil
+}