Improve gauge performance

modules/generator/registry/gauge.go

@@ -24,13 +24,17 @@ type gauge struct {
 
 	onAddSeries    func(count uint32) bool
 	onRemoveSeries func(count uint32)
+
+	externalLabels map[string]string
 }
 
 type gaugeSeries struct {
 	// labelValueCombo should not be modified after creation
 	labels      LabelPair
 	value       *atomic.Float64
 	lastUpdated *atomic.Int64
+	lb          *labels.Builder
+	baseLabels  labels.Labels
 }
 
 var (
@@ -43,7 +47,7 @@ const (
 	set = "set"
 )
 
-func newGauge(name string, onAddSeries func(uint32) bool, onRemoveSeries func(count uint32)) *gauge {
+func newGauge(name string, onAddSeries func(uint32) bool, onRemoveSeries func(count uint32), externalLabels map[string]string) *gauge {
 	if onAddSeries == nil {
 		onAddSeries = func(uint32) bool {
 			return true
@@ -58,6 +62,7 @@ func newGauge(name string, onAddSeries func(uint32) bool, onRemoveSeries func(co
 		series:         make(map[uint64]*gaugeSeries),
 		onAddSeries:    onAddSeries,
 		onRemoveSeries: onRemoveSeries,
+		externalLabels: externalLabels,
 	}
 }
 
@@ -107,10 +112,23 @@ func (g *gauge) updateSeries(labelValueCombo *LabelValueCombo, value float64, op
 }
 
 func (g *gauge) newSeries(labelValueCombo *LabelValueCombo, value float64) *gaugeSeries {
+	// base labels
+	baseLabels := make(labels.Labels, 1+len(g.externalLabels))
+
+	// add metric name
+	baseLabels = append(baseLabels, labels.Label{Name: labels.MetricName, Value: g.metricName})
+
+	// add external labels
+	for name, value := range g.externalLabels {
+		baseLabels = append(baseLabels, labels.Label{Name: name, Value: value})
+	}
+
 	return &gaugeSeries{
 		labels:      labelValueCombo.getLabelPair(),
 		value:       atomic.NewFloat64(value),
 		lastUpdated: atomic.NewInt64(time.Now().UnixMilli()),
+		lb:          labels.NewBuilder(baseLabels),
+		baseLabels:  baseLabels,
 	}
 }
 
@@ -127,43 +145,24 @@ func (g *gauge) name() string {
 	return g.metricName
 }
 
-func (g *gauge) collectMetrics(appender storage.Appender, timeMs int64, externalLabels map[string]string) (activeSeries int, err error) {
+func (g *gauge) collectMetrics(appender storage.Appender, timeMs int64, _ map[string]string) (activeSeries int, err error) {
 	g.seriesMtx.RLock()
 	defer g.seriesMtx.RUnlock()
 
 	activeSeries = len(g.series)
 
-	labelsCount := 0
-	if activeSeries > 0 && g.series[0] != nil {
-		labelsCount = len(g.series[0].labels.names)
-	}
-
-	// base labels
-	baseLabels := make(labels.Labels, 1+len(externalLabels)+labelsCount)
-
-	// add metric name
-	baseLabels = append(baseLabels, labels.Label{Name: labels.MetricName, Value: g.metricName})
-
-	// add external labels
-	for name, value := range externalLabels {
-		baseLabels = append(baseLabels, labels.Label{Name: name, Value: value})
-	}
-
-	// TODO: avoid allocation on each collection
-	lb := labels.NewBuilder(baseLabels)
-
 	for _, s := range g.series {
 		t := time.UnixMilli(timeMs)
 
 		// reset labels for every series
-		lb.Reset(baseLabels)
+		s.lb.Reset(s.baseLabels)
 
 		// set series-specific labels
 		for i, name := range s.labels.names {
-			lb.Set(name, s.labels.values[i])
+			s.lb.Set(name, s.labels.values[i])
 		}
 
-		_, err = appender.Append(0, lb.Labels(), t.UnixMilli(), s.value.Load())
+		_, err = appender.Append(0, s.lb.Labels(), t.UnixMilli(), s.value.Load())
 		if err != nil {
 			return
 		}

modules/generator/registry/gauge_test.go

@@ -17,7 +17,7 @@ func Test_gaugeInc(t *testing.T) {
 		return true
 	}
 
-	c := newGauge("my_gauge", onAdd, nil)
+	c := newGauge("my_gauge", onAdd, nil, nil)
 
 	c.Inc(newLabelValueCombo([]string{"label"}, []string{"value-1"}), 1.0)
 	c.Inc(newLabelValueCombo([]string{"label"}, []string{"value-2"}), 2.0)
@@ -52,7 +52,7 @@ func TestGaugeDifferentLabels(t *testing.T) {
 		return true
 	}
 
-	c := newGauge("my_gauge", onAdd, nil)
+	c := newGauge("my_gauge", onAdd, nil, nil)
 
 	c.Inc(newLabelValueCombo([]string{"label"}, []string{"value-1"}), 1.0)
 	c.Inc(newLabelValueCombo([]string{"another_label"}, []string{"another_value"}), 2.0)
@@ -74,7 +74,7 @@ func Test_gaugeSet(t *testing.T) {
 		return true
 	}
 
-	c := newGauge("my_gauge", onAdd, nil)
+	c := newGauge("my_gauge", onAdd, nil, nil)
 
 	c.Set(newLabelValueCombo([]string{"label"}, []string{"value-1"}), 1.0)
 	c.Set(newLabelValueCombo([]string{"label"}, []string{"value-2"}), 2.0)
@@ -109,7 +109,7 @@ func Test_gauge_cantAdd(t *testing.T) {
 		return canAdd
 	}
 
-	c := newGauge("my_gauge", onAdd, nil)
+	c := newGauge("my_gauge", onAdd, nil, nil)
 
 	// allow adding new series
 	canAdd = true
@@ -145,7 +145,7 @@ func Test_gauge_removeStaleSeries(t *testing.T) {
 		removedSeries++
 	}
 
-	c := newGauge("my_gauge", nil, onRemove)
+	c := newGauge("my_gauge", nil, onRemove, nil)
 
 	timeMs := time.Now().UnixMilli()
 	c.Inc(newLabelValueCombo([]string{"label"}, []string{"value-1"}), 1.0)
@@ -180,7 +180,7 @@ func Test_gauge_removeStaleSeries(t *testing.T) {
 }
 
 func Test_gauge_externalLabels(t *testing.T) {
-	c := newGauge("my_gauge", nil, nil)
+	c := newGauge("my_gauge", nil, nil, map[string]string{"external_label": "external_value"})
 
 	c.Inc(newLabelValueCombo([]string{"label"}, []string{"value-1"}), 1.0)
 	c.Inc(newLabelValueCombo([]string{"label"}, []string{"value-2"}), 2.0)
@@ -190,11 +190,11 @@ func Test_gauge_externalLabels(t *testing.T) {
 		newSample(map[string]string{"__name__": "my_gauge", "label": "value-1", "external_label": "external_value"}, collectionTimeMs, 1),
 		newSample(map[string]string{"__name__": "my_gauge", "label": "value-2", "external_label": "external_value"}, collectionTimeMs, 2),
 	}
-	collectMetricAndAssert(t, c, collectionTimeMs, map[string]string{"external_label": "external_value"}, 2, expectedSamples, nil)
+	collectMetricAndAssert(t, c, collectionTimeMs, nil, 2, expectedSamples, nil)
 }
 
 func Test_gauge_concurrencyDataRace(t *testing.T) {
-	c := newGauge("my_gauge", nil, nil)
+	c := newGauge("my_gauge", nil, nil, nil)
 
 	end := make(chan struct{})
 
@@ -240,7 +240,7 @@ func Test_gauge_concurrencyDataRace(t *testing.T) {
 }
 
 func Test_gauge_concurrencyCorrectness(t *testing.T) {
-	c := newGauge("my_gauge", nil, nil)
+	c := newGauge("my_gauge", nil, nil, nil)
 
 	var wg sync.WaitGroup
 	end := make(chan struct{})

modules/generator/registry/registry.go

@@ -166,7 +166,7 @@ func (r *ManagedRegistry) NewHistogram(name string, buckets []float64, histogram
 }
 
 func (r *ManagedRegistry) NewGauge(name string) Gauge {
-	g := newGauge(name, r.onAddMetricSeries, r.onRemoveMetricSeries)
+	g := newGauge(name, r.onAddMetricSeries, r.onRemoveMetricSeries, r.externalLabels)
 	r.registerMetric(g)
 	return g
 }