process: fix fallback to V1 collector (#1667)

internal/collector/process/process.go

@@ -162,6 +162,7 @@ func (c *Collector) Build(logger *slog.Logger, wmiClient *wmi.Client) error {
 
 	if utils.PDHEnabled() {
 		counters := []string{
+			processID,
 			percentProcessorTime,
 			percentPrivilegedTime,
 			percentUserTime,
@@ -181,7 +182,6 @@ func (c *Collector) Build(logger *slog.Logger, wmiClient *wmi.Client) error {
 			pageFileBytes,
 			poolNonPagedBytes,
 			poolPagedBytes,
-			processID,
 			priorityBase,
 			privateBytes,
 			threadCount,
@@ -195,37 +195,8 @@ func (c *Collector) Build(logger *slog.Logger, wmiClient *wmi.Client) error {
 		var err error
 
 		c.perfDataCollector, err = perfdata.NewCollector("Process V2", c.config.PerfCounterInstances, counters)
-		if errors.Is(err, perfdata.NewPdhError(perfdata.PdhNoData)) {
-			counters = []string{
-				percentProcessorTime,
-				percentPrivilegedTime,
-				percentUserTime,
-				creatingProcessID,
-				elapsedTime,
-				handleCount,
-				idProcess,
-				ioDataBytesPerSec,
-				ioDataOperationsPerSec,
-				ioOtherBytesPerSec,
-				ioOtherOperationsPerSec,
-				ioReadBytesPerSec,
-				ioReadOperationsPerSec,
-				ioWriteBytesPerSec,
-				ioWriteOperationsPerSec,
-				pageFaultsPerSec,
-				pageFileBytesPeak,
-				pageFileBytes,
-				poolNonPagedBytes,
-				poolPagedBytes,
-				priorityBase,
-				privateBytes,
-				threadCount,
-				virtualBytesPeak,
-				virtualBytes,
-				workingSetPrivate,
-				workingSetPeak,
-				workingSet,
-			}
+		if errors.Is(err, perfdata.NewPdhError(perfdata.PdhCstatusNoObject)) {
+			counters[0] = idProcess
 
 			c.perfDataCollector, err = perfdata.NewCollector("Process", c.config.PerfCounterInstances, counters)
 		}

internal/collector/process/process_test.go

@@ -1,11 +1,18 @@
 package process_test
 
 import (
+	"io"
+	"log/slog"
+	"sync"
 	"testing"
+	"time"
 
 	"github.com/alecthomas/kingpin/v2"
 	"github.com/prometheus-community/windows_exporter/internal/collector/process"
 	"github.com/prometheus-community/windows_exporter/internal/testutils"
+	"github.com/prometheus/client_golang/prometheus"
+	"github.com/stretchr/testify/require"
+	"github.com/yusufpapurcu/wmi"
 )
 
 func BenchmarkProcessCollector(b *testing.B) {
@@ -15,3 +22,49 @@ func BenchmarkProcessCollector(b *testing.B) {
 	// No context name required as collector source is WMI
 	testutils.FuncBenchmarkCollector(b, process.Name, process.NewWithFlags)
 }
+
+func TestProcessCollector(t *testing.T) {
+	t.Setenv("WINDOWS_EXPORTER_PERF_COUNTERS_ENGINE", "pdh")
+
+	var (
+		metrics []prometheus.Metric
+		err     error
+	)
+
+	logger := slog.New(slog.NewTextHandler(io.Discard, nil))
+	c := process.New(nil)
+	ch := make(chan prometheus.Metric, 10000)
+
+	wmiClient := &wmi.Client{
+		AllowMissingFields: true,
+	}
+	wmiClient.SWbemServicesClient, err = wmi.InitializeSWbemServices(wmiClient)
+	require.NoError(t, err)
+
+	t.Cleanup(func() {
+		require.NoError(t, c.Close(logger))
+	})
+
+	wg := sync.WaitGroup{}
+	wg.Add(1)
+
+	go func() {
+		defer wg.Done()
+
+		for metric := range ch {
+			metrics = append(metrics, metric)
+		}
+	}()
+
+	require.NoError(t, c.Build(logger, wmiClient))
+
+	time.Sleep(1 * time.Second)
+
+	require.NoError(t, c.Collect(nil, logger, ch))
+
+	close(ch)
+
+	wg.Wait()
+
+	require.NotEmpty(t, metrics)
+}