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

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

internal/pdh/collector.go

@@ -217,7 +217,7 @@ func newCollector[T any](logger *slog.Logger, resultType CounterType, object str
 		resultType:            resultType,
 		counters:              make([]Counter, 0, len(fields)),
 		handle:                handle,
-		totalCounterRequested: slices.Contains(instances, InstanceTotal),
+		totalCounterRequested: slices.ContainsFunc(instances, func(instance string) bool { return IsTotalInstance(object, instance) }),
 		mu:                    sync.RWMutex{},
 		logger:                logger,
 		rows:                  rows,
@@ -597,7 +597,7 @@ func (r *rowSet[T]) row(counter *Counter, szName *uint16, status uint32) (int, b
 		return 0, false
 	}
 
-	if strings.HasSuffix(instanceName, InstanceTotal) && !r.c.totalCounterRequested {
+	if IsTotalInstance(r.c.object, instanceName) && !r.c.totalCounterRequested {
 		return 0, false
 	}
 

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
+}

internal/pdh/instance_total_test.go

@@ -0,0 +1,107 @@
+// 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_test
+
+import (
+	"log/slog"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"testing"
+	"time"
+
+	"github.com/prometheus-community/windows_exporter/internal/pdh"
+	"github.com/prometheus-community/windows_exporter/internal/pdh/registry"
+	"github.com/stretchr/testify/require"
+)
+
+func TestIsTotalInstance(t *testing.T) {
+	t.Parallel()
+
+	for _, tc := range []struct {
+		object string
+		name   string
+		want   bool
+	}{
+		{"Process", "_Total", true},
+		{"Process", "worker_Total", false},
+		{"SQLServer:Databases", "Orders_Total", false},
+		{"SQLServer:Databases", "0,_Total", false},
+		{"Processor Information", "_Total", true},
+		{"Processor Information", "0,_Total", true},
+		{"Processor Information", "0,1", false},
+		{"Processor Information", "worker_Total", false},
+	} {
+		require.Equal(t, tc.want, pdh.IsTotalInstance(tc.object, tc.name), "%s/%s", tc.object, tc.name)
+	}
+}
+
+func TestTotalSuffixProcess(t *testing.T) {
+	if os.Getenv("WINDOWS_EXPORTER_TEST_TOTAL_CHILD") == "1" {
+		time.Sleep(time.Minute)
+
+		return
+	}
+
+	t.Parallel()
+
+	executable, err := os.Executable()
+	require.NoError(t, err)
+	contents, err := os.ReadFile(executable)
+	require.NoError(t, err)
+	childPath := filepath.Join(t.TempDir(), "worker_Total.exe")
+	//nolint:gosec // The destination is a fixed filename in a test-owned temporary directory.
+	require.NoError(t, os.WriteFile(childPath, contents, 0o600))
+	child := exec.CommandContext(t.Context(), childPath, "-test.run=^TestTotalSuffixProcess$")
+
+	child.Env = append(os.Environ(), "WINDOWS_EXPORTER_TEST_TOTAL_CHILD=1")
+	require.NoError(t, child.Start())
+	t.Cleanup(func() { _ = child.Process.Kill(); _ = child.Wait() })
+
+	type processValues struct {
+		Name string
+		ID   float64 `perfdata:"ID Process"`
+	}
+
+	legacy, err := registry.NewCollector[processValues]("Process", pdh.InstancesAll)
+	require.NoError(t, err)
+	t.Cleanup(legacy.Close)
+
+	modern, err := pdh.NewCollector[processValues](slog.New(slog.DiscardHandler), pdh.CounterTypeRaw, "Process", []string{"worker_Total"})
+	require.NoError(t, err)
+	t.Cleanup(modern.Close)
+
+	for name, collect := range map[string]func(*[]processValues) error{"registry": legacy.Collect, "explicit PDH": modern.Collect} {
+		t.Run(name, func(t *testing.T) {
+			require.Eventually(t, func() bool {
+				var rows []processValues
+				if collect(&rows) != nil {
+					return false
+				}
+
+				for _, row := range rows {
+					if row.ID == float64(child.Process.Pid) && row.Name == "worker_Total" {
+						return true
+					}
+				}
+
+				return false
+			}, time.Second*5, time.Millisecond*100)
+		})
+	}
+}

internal/pdh/registry/collector.go

@@ -164,7 +164,7 @@ func (c *Collector[T]) Collect(dst *[]T) error {
 
 		for _, perfInstance := range perfObject.Instances {
 			instanceName := perfInstance.Name
-			if strings.HasSuffix(instanceName, "_Total") {
+			if pdh.IsTotalInstance(c.object, instanceName) {
 				continue
 			}