fix: ignore modifications to unregistered metrics

go.mod

@@ -9,18 +9,21 @@ require (
 	github.com/sirupsen/logrus v1.9.3
 	github.com/spf13/cobra v1.8.0
 	github.com/spf13/viper v1.18.2
+	github.com/stretchr/testify v1.10.0
 )
 
 require (
 	github.com/beorn7/perks v1.0.1 // indirect
 	github.com/cespare/xxhash/v2 v2.3.0 // indirect
+	github.com/davecgh/go-spew v1.1.2-0.20180830191138-d8f796af33cc // indirect
 	github.com/fsnotify/fsnotify v1.7.0 // indirect
 	github.com/hashicorp/hcl v1.0.0 // indirect
 	github.com/inconshreveable/mousetrap v1.1.0 // indirect
 	github.com/magiconair/properties v1.8.7 // indirect
 	github.com/mitchellh/mapstructure v1.5.0 // indirect
 	github.com/nelkinda/http-go v0.0.1 // indirect
 	github.com/pelletier/go-toml/v2 v2.2.2 // indirect
+	github.com/pmezard/go-difflib v1.0.1-0.20181226105442-5d4384ee4fb2 // indirect
 	github.com/prometheus/client_model v0.6.1 // indirect
 	github.com/prometheus/common v0.53.0 // indirect
 	github.com/prometheus/procfs v0.14.0 // indirect
@@ -30,7 +33,6 @@ require (
 	github.com/spf13/afero v1.11.0 // indirect
 	github.com/spf13/cast v1.6.0 // indirect
 	github.com/spf13/pflag v1.0.5 // indirect
-	github.com/stretchr/testify v1.10.0 // indirect
 	github.com/subosito/gotenv v1.6.0 // indirect
 	github.com/tidwall/gjson v1.14.4 // indirect
 	github.com/tidwall/match v1.1.1 // indirect

main.go

@@ -215,7 +215,7 @@ func runExporter() {
 
 	log.Infof("Metrics set: %v", slices.Sorted(maps.Keys(enabledMetrics)))
 	for _, metric := range enabledMetrics {
-		prometheus.MustRegister(metric)
+		metric.MustRegisterWith(prometheus.DefaultRegisterer)
 	}
 
 	scrapeInterval := time.Duration(viper.GetInt("scrape_interval")) * time.Second

metrics.go

@@ -11,6 +11,10 @@ import (
 const joinChar = "|"
 const maxAge = 1 * time.Hour
 
+type trackedMetric interface {
+	MustRegisterWith(prometheus.Registerer)
+}
+
 type reportableMetrics []*metricTracker
 
 var registeredMetrics = reportableMetrics{}
@@ -29,83 +33,91 @@ func register(m *metricTracker) {
 
 type metricTracker struct {
 	sync.Mutex
+	registered  bool
+	collector   prometheus.Collector
+	del         func(...string) bool
 	expirations map[string]time.Time
 }
 
-func newMetricTracker() *metricTracker {
-	mt := &metricTracker{expirations: map[string]time.Time{}}
+func newMetricTracker(collector prometheus.Collector, del func(...string) bool) *metricTracker {
+	mt := &metricTracker{
+		registered:  false,
+		collector:   collector,
+		del:         del,
+		expirations: map[string]time.Time{},
+	}
 	register(mt)
 	return mt
 }
 
-func (m *metricTracker) touch(labels []string) {
-	m.Lock()
-	defer m.Unlock()
-	m.expirations[strings.Join(labels, joinChar)] = time.Now().Add(maxAge)
+func (mt *metricTracker) update(labels []string, fn func()) {
+	if !mt.registered {
+		return
+	}
+
+	mt.Lock()
+	mt.expirations[strings.Join(labels, joinChar)] = time.Now().Add(maxAge)
+	defer mt.Unlock()
+
+	fn()
+}
+
+func (mt *metricTracker) MustRegisterWith(registry prometheus.Registerer) {
+	mt.registered = true
+	registry.MustRegister(mt)
+}
+
+func (mt *metricTracker) Describe(ch chan<- *prometheus.Desc) {
+	mt.collector.Describe(ch)
 }
 
-func (m *metricTracker) collect(del func(...string) bool) {
-	m.Lock()
-	defer m.Unlock()
+func (mt *metricTracker) Collect(ch chan<- prometheus.Metric) {
+	mt.Lock()
+	defer mt.Unlock()
 	now := time.Now()
-	for k, v := range m.expirations {
+	for k, v := range mt.expirations {
 		if v.Before(now) {
-			delete(m.expirations, k)
-			if del(strings.Split(k, joinChar)...) {
+			delete(mt.expirations, k)
+			if mt.del(strings.Split(k, joinChar)...) {
 				expiredMetrics.Inc()
 			}
 		}
 	}
+	mt.collector.Collect(ch)
 }
 
 type trackedGauge struct {
-	tracker *metricTracker
-	gauge   *prometheus.GaugeVec
+	*metricTracker
+	gauge *prometheus.GaugeVec
 }
 
 func NewTrackedGauge(gauge *prometheus.GaugeVec) *trackedGauge {
 	return &trackedGauge{
-		tracker: newMetricTracker(),
-		gauge:   gauge,
+		metricTracker: newMetricTracker(gauge, gauge.DeleteLabelValues),
+		gauge:         gauge,
 	}
 }
 
-func (tg *trackedGauge) Describe(ch chan<- *prometheus.Desc) {
-	tg.gauge.Describe(ch)
-}
-
-func (tg *trackedGauge) Collect(ch chan<- prometheus.Metric) {
-	tg.tracker.collect(tg.gauge.DeleteLabelValues)
-	tg.gauge.Collect(ch)
-}
-
 func (tg *trackedGauge) Set(val float64, labels ...string) {
-	tg.gauge.WithLabelValues(labels...).Set(val)
-	tg.tracker.touch(labels)
+	tg.update(labels, func() {
+		tg.gauge.WithLabelValues(labels...).Set(val)
+	})
 }
 
 type trackedCounter struct {
-	tracker *metricTracker
+	*metricTracker
 	counter *prometheus.CounterVec
 }
 
 func NewTrackedCounter(counter *prometheus.CounterVec) *trackedCounter {
 	return &trackedCounter{
-		tracker: newMetricTracker(),
-		counter: counter,
+		metricTracker: newMetricTracker(counter, counter.DeleteLabelValues),
+		counter:       counter,
 	}
 }
 
-func (tc *trackedCounter) Describe(ch chan<- *prometheus.Desc) {
-	tc.counter.Describe(ch)
-}
-
-func (tc *trackedCounter) Collect(ch chan<- prometheus.Metric) {
-	tc.tracker.collect(tc.counter.DeleteLabelValues)
-	tc.counter.Collect(ch)
-}
-
 func (tc *trackedCounter) Add(val float64, labels ...string) {
-	tc.counter.WithLabelValues(labels...).Add(val)
-	tc.tracker.touch(labels)
+	tc.update(labels, func() {
+		tc.counter.WithLabelValues(labels...).Add(val)
+	})
 }