cache: emit copy-read hit totals as counters (#2602)

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

internal/collector/cache/cache.go

@@ -25,6 +25,7 @@ import (
 	"github.com/alecthomas/kingpin/v2"
 	"github.com/prometheus-community/windows_exporter/internal/mi"
 	"github.com/prometheus-community/windows_exporter/internal/pdh"
+	pdhtypes "github.com/prometheus-community/windows_exporter/internal/pdh/types"
 	"github.com/prometheus-community/windows_exporter/internal/types"
 	"github.com/prometheus/client_golang/prometheus"
 )
@@ -40,7 +41,7 @@ var ConfigDefaults = Config{}
 type Collector struct {
 	config Config
 
-	perfDataCollector *pdh.Collector[perfDataCounterValues]
+	perfDataCollector pdhtypes.Collector[perfDataCounterValues]
 	perfDataObject    []perfDataCounterValues
 
 	asyncCopyReadsTotal         *prometheus.Desc
@@ -95,7 +96,9 @@ func (c *Collector) GetName() string {
 }
 
 func (c *Collector) Close() error {
-	c.perfDataCollector.Close()
+	if c.perfDataCollector != nil {
+		c.perfDataCollector.Close()
+	}
 
 	return nil
 }
@@ -327,7 +330,7 @@ func (c *Collector) Collect(ch chan<- prometheus.Metric, _ time.Duration) error
 
 	ch <- prometheus.MustNewConstMetric(
 		c.copyReadHitsTotal,
-		prometheus.GaugeValue,
+		prometheus.CounterValue,
 		c.perfDataObject[0].CopyReadHitsTotal,
 	)
 

internal/collector/cache/copy_read_type_test.go

@@ -0,0 +1,98 @@
+// 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 cache
+
+import (
+	"log/slog"
+	"strings"
+	"testing"
+
+	"github.com/prometheus/client_golang/prometheus"
+	dto "github.com/prometheus/client_model/go"
+	"github.com/prometheus/common/expfmt"
+	"github.com/stretchr/testify/require"
+)
+
+func TestCopyReadHitCounterWireFormats(t *testing.T) {
+	t.Parallel()
+
+	c := New(nil)
+	require.NoError(t, c.Build(slog.New(slog.DiscardHandler), nil))
+	c.perfDataCollector.Close()
+	c.perfDataCollector = copyReadFixture{}
+	wrapper := &copyReadTestCollector{collector: c}
+	registry := prometheus.NewRegistry()
+	registry.MustRegister(wrapper)
+	families, err := registry.Gather()
+	require.NoError(t, err)
+	require.NoError(t, wrapper.err)
+
+	found := false
+
+	for _, family := range families {
+		if family.GetName() != "windows_cache_copy_read_hits_total" {
+			continue
+		}
+
+		found = true
+
+		require.Equal(t, dto.MetricType_COUNTER, family.GetType())
+		require.InDelta(t, 25, family.GetMetric()[0].GetCounter().GetValue(), 1e-9)
+
+		var text strings.Builder
+
+		_, err := expfmt.MetricFamilyToText(&text, family)
+		require.NoError(t, err)
+		require.Contains(t, text.String(), "# TYPE windows_cache_copy_read_hits_total counter")
+
+		var openMetrics strings.Builder
+
+		_, err = expfmt.MetricFamilyToOpenMetrics(&openMetrics, family)
+		require.NoError(t, err)
+		require.Contains(t, openMetrics.String(), "# TYPE windows_cache_copy_read_hits counter")
+		require.Contains(t, openMetrics.String(), "windows_cache_copy_read_hits_total 25")
+	}
+
+	require.True(t, found)
+}
+
+type copyReadFixture struct{}
+
+func (copyReadFixture) Collect(dst *[]perfDataCounterValues) error {
+	*dst = []perfDataCounterValues{{CopyReadHitsTotal: 25}}
+
+	return nil
+}
+
+func (copyReadFixture) Close() {}
+
+type copyReadTestCollector struct {
+	collector *Collector
+	err       error
+}
+
+func (c *copyReadTestCollector) Describe(_ chan<- *prometheus.Desc) {}
+
+func (c *copyReadTestCollector) Collect(ch chan<- prometheus.Metric) {
+	c.err = c.collector.Collect(ch, 0)
+}
+
+func TestCopyReadCollectorCloseBeforeInitialization(t *testing.T) {
+	t.Parallel()
+	require.NoError(t, New(nil).Close())
+}