WIP: Add support for prometheus with exemplars

Gopkg.toml

@@ -12,7 +12,7 @@
 
 [[constraint]]
   name = "github.com/prometheus/client_golang"
-  version = "1.1.0"
+  version = "1.4.1"
 
 [[constraint]]
   name = "github.com/stretchr/testify"

metrics/counter.go

@@ -20,9 +20,18 @@ type Counter interface {
 	Inc(int64)
 }
 
+// CounterWithExemplar tracks the number of times an event has occurred and
+// supports exemplars
+type CounterWithExemplar interface {
+	Counter
+	IncWithExemplar(int64, map[string]string)
+}
+
 // NullCounter counter that does nothing
-var NullCounter Counter = nullCounter{}
+var NullCounter CounterWithExemplar = nullCounter{}
 
 type nullCounter struct{}
 
 func (nullCounter) Inc(int64) {}
+
+func (nullCounter) IncWithExemplar(int64, map[string]string) {}

metrics/histogram.go

@@ -20,9 +20,18 @@ type Histogram interface {
 	Record(float64)
 }
 
+// HistogramWithExemplar that keeps track of a distribution of values and
+// supports exemplars.
+type HistogramWithExemplar interface {
+	Histogram
+	RecordWithExemplar(float64, map[string]string)
+}
+
 // NullHistogram that does nothing
-var NullHistogram Histogram = nullHistogram{}
+var NullHistogram HistogramWithExemplar = nullHistogram{}
 
 type nullHistogram struct{}
 
 func (nullHistogram) Record(float64) {}
+
+func (nullHistogram) RecordWithExemplar(float64, map[string]string) {}

metrics/prometheus/factory.go

@@ -138,8 +138,16 @@ func (f *Factory) Counter(options metrics.Options) metrics.Counter {
 		Help: help,
 	}
 	cv := f.cache.getOrMakeCounterVec(opts, labelNames)
+
+	ctr := cv.WithLabelValues(f.tagsAsLabelValues(labelNames, tags)...)
+	exemplarAdder, ok := ctr.(prometheus.ExemplarAdder)
+	if !ok {
+		exemplarAdder = nil
+	}
+
 	return &counter{
-		counter: cv.WithLabelValues(f.tagsAsLabelValues(labelNames, tags)...),
+		counter:       ctr,
+		exemplarAdder: exemplarAdder,
 	}
 }
 
@@ -177,8 +185,14 @@ func (f *Factory) Timer(options metrics.TimerOptions) metrics.Timer {
 		Buckets: asFloatBuckets(options.Buckets),
 	}
 	hv := f.cache.getOrMakeHistogramVec(opts, labelNames)
+	hist := hv.WithLabelValues(f.tagsAsLabelValues(labelNames, tags)...)
+	exemplarObserver, ok := hist.(prometheus.ExemplarObserver)
+	if !ok {
+		exemplarObserver = nil
+	}
 	return &timer{
-		histogram: hv.WithLabelValues(f.tagsAsLabelValues(labelNames, tags)...),
+		histogram:        hist,
+		exemplarObserver: exemplarObserver,
 	}
 }
 
@@ -205,8 +219,14 @@ func (f *Factory) Histogram(options metrics.HistogramOptions) metrics.Histogram
 		Buckets: options.Buckets,
 	}
 	hv := f.cache.getOrMakeHistogramVec(opts, labelNames)
+	hist := hv.WithLabelValues(f.tagsAsLabelValues(labelNames, tags)...)
+	exemplarObserver, ok := hist.(prometheus.ExemplarObserver)
+	if !ok {
+		exemplarObserver = nil
+	}
 	return &histogram{
-		histogram: hv.WithLabelValues(f.tagsAsLabelValues(labelNames, tags)...),
+		histogram:        hist,
+		exemplarObserver: exemplarObserver,
 	}
 }
 
@@ -216,13 +236,22 @@ func (f *Factory) Namespace(scope metrics.NSOptions) metrics.Factory {
 }
 
 type counter struct {
-	counter prometheus.Counter
+	counter       prometheus.Counter
+	exemplarAdder prometheus.ExemplarAdder
 }
 
 func (c *counter) Inc(v int64) {
 	c.counter.Add(float64(v))
 }
 
+func (c *counter) IncWithExemplar(v int64, l map[string]string) {
+	if c.exemplarAdder != nil {
+		c.exemplarAdder.AddWithExemplar(float64(v), l)
+		return
+	}
+	c.Inc(v)
+}
+
 type gauge struct {
 	gauge prometheus.Gauge
 }
@@ -236,21 +265,39 @@ type observer interface {
 }
 
 type timer struct {
-	histogram observer
+	histogram        observer
+	exemplarObserver prometheus.ExemplarObserver
 }
 
 func (t *timer) Record(v time.Duration) {
 	t.histogram.Observe(float64(v.Nanoseconds()) / float64(time.Second/time.Nanosecond))
 }
 
+func (t *timer) RecordWithExemplar(v time.Duration, l map[string]string) {
+	if t.exemplarObserver != nil {
+		t.exemplarObserver.ObserveWithExemplar(float64(v.Nanoseconds())/float64(time.Second/time.Nanosecond), l)
+		return
+	}
+	t.Record(v)
+}
+
 type histogram struct {
-	histogram observer
+	histogram        observer
+	exemplarObserver prometheus.ExemplarObserver
 }
 
 func (h *histogram) Record(v float64) {
 	h.histogram.Observe(v)
 }
 
+func (h *histogram) RecordWithExemplar(v float64, l map[string]string) {
+	if h.exemplarObserver != nil {
+		h.exemplarObserver.ObserveWithExemplar(v, l)
+		return
+	}
+	h.Record(v)
+}
+
 func (f *Factory) subScope(name string) string {
 	if f.scope == "" {
 		return f.normalize(name)

metrics/timer.go

@@ -19,15 +19,24 @@ import (
 )
 
 // Timer accumulates observations about how long some operation took,
-// and also maintains a historgam of percentiles.
+// and also maintains a histogram of percentiles.
 type Timer interface {
 	// Records the time passed in.
 	Record(time.Duration)
 }
 
+// TimerWithExemplar accumulates observations about how long some operation
+// took, maintains a histogram of percentiles and supports exemplars.
+type TimerWithExemplar interface {
+	Timer
+	RecordWithExemplar(time.Duration, map[string]string)
+}
+
 // NullTimer timer that does nothing
 var NullTimer Timer = nullTimer{}
 
 type nullTimer struct{}
 
 func (nullTimer) Record(time.Duration) {}
+
+func (nullTimer) RecordWithExemplar(time.Duration, map[string]string) {}