Histograms for the exposition library.

extraction/metricfamilyprocessor.go

@@ -16,6 +16,7 @@ package extraction
 import (
 	"fmt"
 	"io"
+	"math"
 
 	dto "github.com/prometheus/client_model/go"
 
@@ -85,24 +86,23 @@ func extractCounter(out Ingester, o *ProcessOptions, f *dto.MetricFamily) error
 			continue
 		}
 
-		sample := new(model.Sample)
+		sample := &model.Sample{
+			Metric: model.Metric{},
+			Value:  model.SampleValue(m.Counter.GetValue()),
+		}
 		samples = append(samples, sample)
 
 		if m.TimestampMs != nil {
 			sample.Timestamp = model.TimestampFromUnixNano(*m.TimestampMs * 1000000)
 		} else {
 			sample.Timestamp = o.Timestamp
 		}
-		sample.Metric = model.Metric{}
-		metric := sample.Metric
 
+		metric := sample.Metric
 		for _, p := range m.Label {
 			metric[model.LabelName(p.GetName())] = model.LabelValue(p.GetValue())
 		}
-
 		metric[model.MetricNameLabel] = model.LabelValue(f.GetName())
-
-		sample.Value = model.SampleValue(m.Counter.GetValue())
 	}
 
 	return out.Ingest(samples)
@@ -116,24 +116,23 @@ func extractGauge(out Ingester, o *ProcessOptions, f *dto.MetricFamily) error {
 			continue
 		}
 
-		sample := new(model.Sample)
+		sample := &model.Sample{
+			Metric: model.Metric{},
+			Value:  model.SampleValue(m.Gauge.GetValue()),
+		}
 		samples = append(samples, sample)
 
 		if m.TimestampMs != nil {
 			sample.Timestamp = model.TimestampFromUnixNano(*m.TimestampMs * 1000000)
 		} else {
 			sample.Timestamp = o.Timestamp
 		}
-		sample.Metric = model.Metric{}
-		metric := sample.Metric
 
+		metric := sample.Metric
 		for _, p := range m.Label {
 			metric[model.LabelName(p.GetName())] = model.LabelValue(p.GetValue())
 		}
-
 		metric[model.MetricNameLabel] = model.LabelValue(f.GetName())
-
-		sample.Value = model.SampleValue(m.Gauge.GetValue())
 	}
 
 	return out.Ingest(samples)
@@ -153,48 +152,50 @@ func extractSummary(out Ingester, o *ProcessOptions, f *dto.MetricFamily) error
 		}
 
 		for _, q := range m.Summary.Quantile {
-			sample := new(model.Sample)
+			sample := &model.Sample{
+				Metric:    model.Metric{},
+				Value:     model.SampleValue(q.GetValue()),
+				Timestamp: timestamp,
+			}
 			samples = append(samples, sample)
 
-			sample.Timestamp = timestamp
-			sample.Metric = model.Metric{}
 			metric := sample.Metric
-
 			for _, p := range m.Label {
 				metric[model.LabelName(p.GetName())] = model.LabelValue(p.GetValue())
 			}
 			// BUG(matt): Update other names to "quantile".
-			metric[model.LabelName("quantile")] = model.LabelValue(fmt.Sprint(q.GetQuantile()))
-
+			metric[model.LabelName(model.QuantileLabel)] = model.LabelValue(fmt.Sprint(q.GetQuantile()))
 			metric[model.MetricNameLabel] = model.LabelValue(f.GetName())
-
-			sample.Value = model.SampleValue(q.GetValue())
 		}
 
 		if m.Summary.SampleSum != nil {
-			sum := new(model.Sample)
-			sum.Timestamp = timestamp
-			metric := model.Metric{}
+			sum := &model.Sample{
+				Metric:    model.Metric{},
+				Value:     model.SampleValue(m.Summary.GetSampleSum()),
+				Timestamp: timestamp,
+			}
+			samples = append(samples, sum)
+
+			metric := sum.Metric
 			for _, p := range m.Label {
 				metric[model.LabelName(p.GetName())] = model.LabelValue(p.GetValue())
 			}
 			metric[model.MetricNameLabel] = model.LabelValue(f.GetName() + "_sum")
-			sum.Metric = metric
-			sum.Value = model.SampleValue(m.Summary.GetSampleSum())
-			samples = append(samples, sum)
 		}
 
 		if m.Summary.SampleCount != nil {
-			count := new(model.Sample)
-			count.Timestamp = timestamp
-			metric := model.Metric{}
+			count := &model.Sample{
+				Metric:    model.Metric{},
+				Value:     model.SampleValue(m.Summary.GetSampleCount()),
+				Timestamp: timestamp,
+			}
+			samples = append(samples, count)
+
+			metric := count.Metric
 			for _, p := range m.Label {
 				metric[model.LabelName(p.GetName())] = model.LabelValue(p.GetValue())
 			}
 			metric[model.MetricNameLabel] = model.LabelValue(f.GetName() + "_count")
-			count.Metric = metric
-			count.Value = model.SampleValue(m.Summary.GetSampleCount())
-			samples = append(samples, count)
 		}
 	}
 
@@ -209,24 +210,23 @@ func extractUntyped(out Ingester, o *ProcessOptions, f *dto.MetricFamily) error
 			continue
 		}
 
-		sample := new(model.Sample)
+		sample := &model.Sample{
+			Metric: model.Metric{},
+			Value:  model.SampleValue(m.Untyped.GetValue()),
+		}
 		samples = append(samples, sample)
 
 		if m.TimestampMs != nil {
 			sample.Timestamp = model.TimestampFromUnixNano(*m.TimestampMs * 1000000)
 		} else {
 			sample.Timestamp = o.Timestamp
 		}
-		sample.Metric = model.Metric{}
-		metric := sample.Metric
 
+		metric := sample.Metric
 		for _, p := range m.Label {
 			metric[model.LabelName(p.GetName())] = model.LabelValue(p.GetValue())
 		}
-
 		metric[model.MetricNameLabel] = model.LabelValue(f.GetName())
-
-		sample.Value = model.SampleValue(m.Untyped.GetValue())
 	}
 
 	return out.Ingest(samples)
@@ -245,49 +245,72 @@ func extractHistogram(out Ingester, o *ProcessOptions, f *dto.MetricFamily) erro
 			timestamp = model.TimestampFromUnixNano(*m.TimestampMs * 1000000)
 		}
 
+		infSeen := false
+
 		for _, q := range m.Histogram.Bucket {
-			sample := new(model.Sample)
+			sample := &model.Sample{
+				Metric:    model.Metric{},
+				Value:     model.SampleValue(q.GetCumulativeCount()),
+				Timestamp: timestamp,
+			}
 			samples = append(samples, sample)
 
-			sample.Timestamp = timestamp
-			sample.Metric = model.Metric{}
 			metric := sample.Metric
-
 			for _, p := range m.Label {
 				metric[model.LabelName(p.GetName())] = model.LabelValue(p.GetValue())
 			}
-			metric[model.LabelName("le")] = model.LabelValue(fmt.Sprint(q.GetUpperBound()))
-
+			metric[model.LabelName(model.BucketLabel)] = model.LabelValue(fmt.Sprint(q.GetUpperBound()))
 			metric[model.MetricNameLabel] = model.LabelValue(f.GetName() + "_bucket")
 
-			sample.Value = model.SampleValue(q.GetCumulativeCount())
+			if math.IsInf(q.GetUpperBound(), +1) {
+				infSeen = true
+			}
 		}
-		// TODO: If +Inf bucket is missing, add it.
 
 		if m.Histogram.SampleSum != nil {
-			sum := new(model.Sample)
-			sum.Timestamp = timestamp
-			metric := model.Metric{}
+			sum := &model.Sample{
+				Metric:    model.Metric{},
+				Value:     model.SampleValue(m.Histogram.GetSampleSum()),
+				Timestamp: timestamp,
+			}
+			samples = append(samples, sum)
+
+			metric := sum.Metric
 			for _, p := range m.Label {
 				metric[model.LabelName(p.GetName())] = model.LabelValue(p.GetValue())
 			}
 			metric[model.MetricNameLabel] = model.LabelValue(f.GetName() + "_sum")
-			sum.Metric = metric
-			sum.Value = model.SampleValue(m.Histogram.GetSampleSum())
-			samples = append(samples, sum)
 		}
 
 		if m.Histogram.SampleCount != nil {
-			count := new(model.Sample)
-			count.Timestamp = timestamp
-			metric := model.Metric{}
+			count := &model.Sample{
+				Metric:    model.Metric{},
+				Value:     model.SampleValue(m.Histogram.GetSampleCount()),
+				Timestamp: timestamp,
+			}
+			samples = append(samples, count)
+
+			metric := count.Metric
 			for _, p := range m.Label {
 				metric[model.LabelName(p.GetName())] = model.LabelValue(p.GetValue())
 			}
 			metric[model.MetricNameLabel] = model.LabelValue(f.GetName() + "_count")
-			count.Metric = metric
-			count.Value = model.SampleValue(m.Histogram.GetSampleCount())
-			samples = append(samples, count)
+
+			if !infSeen {
+				infBucket := &model.Sample{
+					Metric:    model.Metric{},
+					Value:     count.Value,
+					Timestamp: timestamp,
+				}
+				samples = append(samples, infBucket)
+
+				metric := infBucket.Metric
+				for _, p := range m.Label {
+					metric[model.LabelName(p.GetName())] = model.LabelValue(p.GetValue())
+				}
+				metric[model.LabelName(model.BucketLabel)] = model.LabelValue("+Inf")
+				metric[model.MetricNameLabel] = model.LabelValue(f.GetName() + "_bucket")
+			}
 		}
 	}
 

model/labelname.go

@@ -33,6 +33,14 @@ const (
 	// JobLabel is the label name indicating the job from which a timeseries
 	// was scraped.
 	JobLabel LabelName = "job"
+
+	// BucketLabel is used for the label that defines the upper bound of a
+	// bucket of a histogram ("le" -> "less or equal").
+	BucketLabel = "le"
+
+	// QuantileLabel is used for the label that defines the quantile in a
+	// summary.
+	QuantileLabel = "quantile"
 )
 
 // A LabelName is a key for a LabelSet or Metric.  It has a value associated

prometheus/benchmark_test.go

@@ -129,3 +129,31 @@ func BenchmarkSummaryNoLabels(b *testing.B) {
 		m.Observe(3.1415)
 	}
 }
+
+func BenchmarkHistogramWithLabelValues(b *testing.B) {
+	m := NewHistogramVec(
+		HistogramOpts{
+			Name: "benchmark_histogram",
+			Help: "A histogram to benchmark it.",
+		},
+		[]string{"one", "two", "three"},
+	)
+	b.ReportAllocs()
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		m.WithLabelValues("eins", "zwei", "drei").Observe(3.1415)
+	}
+}
+
+func BenchmarkHistogramNoLabels(b *testing.B) {
+	m := NewHistogram(HistogramOpts{
+		Name: "benchmark_histogram",
+		Help: "A histogram to benchmark it.",
+	},
+	)
+	b.ReportAllocs()
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		m.Observe(3.1415)
+	}
+}

prometheus/counter.go

@@ -74,7 +74,7 @@ func (c *counter) Add(v float64) {
 // CounterVec is a Collector that bundles a set of Counters that all share the
 // same Desc, but have different values for their variable labels. This is used
 // if you want to count the same thing partitioned by various dimensions
-// (e.g. number of http requests, partitioned by response code and
+// (e.g. number of HTTP requests, partitioned by response code and
 // method). Create instances with NewCounterVec.
 //
 // CounterVec embeds MetricVec. See there for a full list of methods with

prometheus/examples_test.go

@@ -129,7 +129,7 @@ func ExampleCounterVec() {
 	httpReqs := prometheus.NewCounterVec(
 		prometheus.CounterOpts{
 			Name:        "http_requests_total",
-			Help:        "How many HTTP requests processed, partitioned by status code and http method.",
+			Help:        "How many HTTP requests processed, partitioned by status code and HTTP method.",
 			ConstLabels: prometheus.Labels{"env": *binaryVersion},
 		},
 		[]string{"code", "method"},
@@ -200,7 +200,7 @@ func ExampleRegister() {
 		fmt.Println("taskCounter registered.")
 	}
 	// Don't forget to tell the HTTP server about the Prometheus handler.
-	// (In a real program, you still need to start the http server...)
+	// (In a real program, you still need to start the HTTP server...)
 	http.Handle("/metrics", prometheus.Handler())
 
 	// Now you can start workers and give every one of them a pointer to
@@ -240,7 +240,7 @@ func ExampleRegister() {
 
 	// Prometheus will not allow you to ever export metrics with
 	// inconsistent help strings or label names. After unregistering, the
-	// unregistered metrics will cease to show up in the /metrics http
+	// unregistered metrics will cease to show up in the /metrics HTTP
 	// response, but the registry still remembers that those metrics had
 	// been exported before. For this example, we will now choose a
 	// different name. (In a real program, you would obviously not export
@@ -452,3 +452,49 @@ func ExampleSummaryVec() {
 	// >
 	// ]
 }
+
+func ExampleHistogram() {
+	temps := prometheus.NewHistogram(prometheus.HistogramOpts{
+		Name:    "pond_temperature_celsius",
+		Help:    "The temperature of the frog pond.", // Sorry, we can't measure how badly it smells.
+		Buckets: prometheus.LinearBuckets(20, 5, 5),  // 5 buckets, each 5 centigrade wide.
+	})
+
+	// Simulate some observations.
+	for i := 0; i < 1000; i++ {
+		temps.Observe(30 + math.Floor(120*math.Sin(float64(i)*0.1))/10)
+	}
+
+	// Just for demonstration, let's check the state of the histogram by
+	// (ab)using its Write method (which is usually only used by Prometheus
+	// internally).
+	metric := &dto.Metric{}
+	temps.Write(metric)
+	fmt.Println(proto.MarshalTextString(metric))
+
+	// Output:
+	// histogram: <
+	//   sample_count: 1000
+	//   sample_sum: 29969.50000000001
+	//   bucket: <
+	//     cumulative_count: 192
+	//     upper_bound: 20
+	//   >
+	//   bucket: <
+	//     cumulative_count: 366
+	//     upper_bound: 25
+	//   >
+	//   bucket: <
+	//     cumulative_count: 501
+	//     upper_bound: 30
+	//   >
+	//   bucket: <
+	//     cumulative_count: 638
+	//     upper_bound: 35
+	//   >
+	//   bucket: <
+	//     cumulative_count: 816
+	//     upper_bound: 40
+	//   >
+	// >
+}