dhcp: query the distinct non-match denial counter (#2593)

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

internal/collector/dhcp/denial_counters_test.go

@@ -0,0 +1,118 @@
+// 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 dhcp
+
+import (
+	"errors"
+	"log/slog"
+	"reflect"
+	"testing"
+
+	"github.com/prometheus-community/windows_exporter/internal/pdh"
+	"github.com/prometheus/client_golang/prometheus"
+	dto "github.com/prometheus/client_model/go"
+	"github.com/stretchr/testify/require"
+)
+
+func TestDenialCounterValues(t *testing.T) {
+	t.Parallel()
+
+	c := New(&Config{CollectorsEnabled: []string{subCollectorServerMetrics}})
+	// Build creates descriptors before attempting to connect to the optional DHCP provider.
+	_ = c.Build(slog.New(slog.DiscardHandler), nil)
+	if c.perfDataCollector != nil {
+		c.perfDataCollector.Close()
+	}
+
+	c.perfDataCollector = denialFixture{
+		"Denied due to match.":    7,
+		"Denied due to nonmatch.": 11,
+	}
+	metrics := make(chan prometheus.Metric, 100)
+	require.NoError(t, c.collectServerMetrics(metrics))
+	close(metrics)
+
+	found := make(map[*prometheus.Desc]float64)
+
+	for metric := range metrics {
+		var value dto.Metric
+		require.NoError(t, metric.Write(&value))
+		found[metric.Desc()] = value.GetCounter().GetValue()
+	}
+
+	require.InDelta(t, 7, found[c.deniedDueToMatch], 1e-9)
+	require.InDelta(t, 11, found[c.deniedDueToNonMatch], 1e-9)
+}
+
+type denialFixture map[string]float64
+
+func (f denialFixture) Collect(dst *[]perfDataCounterValues) error {
+	var row perfDataCounterValues
+
+	value := reflect.ValueOf(&row).Elem()
+	for _, field := range reflect.VisibleFields(value.Type()) {
+		value.FieldByIndex(field.Index).SetFloat(f[field.Tag.Get("perfdata")])
+	}
+
+	*dst = []perfDataCounterValues{row}
+
+	return nil
+}
+
+func (f denialFixture) Close() {}
+
+func TestNativeDenialCounterNames(t *testing.T) {
+	t.Parallel()
+
+	logger := slog.New(slog.DiscardHandler)
+	// Probe a known counter first so absence of the DHCP role can be skipped.
+	probe, err := pdh.NewDynamicCollector(logger, pdh.CounterTypeRaw, "DHCP Server", nil, []string{"Acks/sec"})
+	if probe != nil {
+		t.Cleanup(probe.Close)
+	}
+
+	if errors.Is(err, pdh.NewPdhError(pdh.CstatusNoObject)) || errors.Is(err, pdh.NewPdhError(pdh.CstatusNoCounter)) {
+		t.Skip("DHCP Server performance counters are unavailable")
+	}
+
+	require.NoError(t, err)
+
+	names := make([]string, 0, 2)
+
+	for _, fieldName := range []string{"DeniedDueToMatch", "DeniedDueToNonMatch"} {
+		field, ok := reflect.TypeFor[perfDataCounterValues]().FieldByName(fieldName)
+		require.True(t, ok)
+
+		names = append(names, field.Tag.Get("perfdata"))
+	}
+
+	native, err := pdh.NewDynamicCollector(logger, pdh.CounterTypeRaw, "DHCP Server", nil, names)
+	if native != nil {
+		t.Cleanup(native.Close)
+	}
+
+	require.NoError(t, err, "the production denial counter names must exist on the native provider")
+}
+
+func TestCloseAfterInvalidSubcollectorBuild(t *testing.T) {
+	t.Parallel()
+
+	c := New(&Config{CollectorsEnabled: []string{subCollectorServerMetrics, "invalid"}})
+	require.Error(t, c.Build(slog.New(slog.DiscardHandler), nil))
+	require.NoError(t, c.Close())
+}

internal/collector/dhcp/dhcp.go

@@ -30,6 +30,7 @@ import (
 	"github.com/prometheus-community/windows_exporter/internal/headers/dhcpsapi"
 	"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"
 )
@@ -59,7 +60,7 @@ type Collector struct {
 
 	logger *slog.Logger
 
-	perfDataCollector *pdh.Collector[perfDataCounterValues]
+	perfDataCollector pdhtypes.Collector[perfDataCounterValues]
 	perfDataObject    []perfDataCounterValues
 
 	acksTotal                                        *prometheus.Desc
@@ -143,7 +144,7 @@ func (c *Collector) GetName() string {
 }
 
 func (c *Collector) Close() error {
-	if slices.Contains(c.config.CollectorsEnabled, subCollectorServerMetrics) {
+	if slices.Contains(c.config.CollectorsEnabled, subCollectorServerMetrics) && c.perfDataCollector != nil {
 		c.perfDataCollector.Close()
 	}
 

internal/collector/dhcp/types.go

@@ -23,7 +23,7 @@ type perfDataCounterValues struct {
 	ConflictCheckQueueLength                         float64 `perfdata:"Conflict Check Queue Length"`
 	DeclinesTotal                                    float64 `perfdata:"Declines/sec"`
 	DeniedDueToMatch                                 float64 `perfdata:"Denied due to match."`
-	DeniedDueToNonMatch                              float64 `perfdata:"Denied due to match."`
+	DeniedDueToNonMatch                              float64 `perfdata:"Denied due to nonmatch."`
 	DiscoversTotal                                   float64 `perfdata:"Discovers/sec"`
 	DuplicatesDroppedTotal                           float64 `perfdata:"Duplicates Dropped/sec"`
 	FailoverBndAckReceivedTotal                      float64 `perfdata:"Failover: BndAck received/sec."`