Add unit suffixes to prometheus metric names

CHANGELOG.md

@@ -21,7 +21,8 @@ This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
 - The `"go.opentelemetry.io/otel/exporters/prometheus".New` now also returns an error indicating the failure to register the exporter with Prometheus. (#3239)
 - The prometheus exporter will no longer try to enumerate the metrics it will send to prometheus on startup.
    This fixes the `reader is not registered` warning currently emitted on startup. (#3291 #3342)
-- The `go.opentelemetry.io/otel/exporters/prometheus` exporter now correctly adds _total suffixes to counter metrics. (#3360)
+- The `go.opentelemetry.io/otel/exporters/prometheus` exporter now adds a unit suffix to metric names.
+   This can be disabled with the `WithoutUnits()` option. (#3352)
 
 ### Fixed
 

exporters/prometheus/confg_test.go

@@ -89,11 +89,20 @@ func TestNewConfig(t *testing.T) {
 				disableTargetInfo: true,
 			},
 		},
+		{
+			name: "unit suffixes disabled",
+			options: []Option{
+				WithoutUnits(),
+			},
+			wantConfig: config{
+				registerer:   prometheus.DefaultRegisterer,
+				withoutUnits: true,
+			},
+		},
 	}
 	for _, tt := range testCases {
 		t.Run(tt.name, func(t *testing.T) {
 			cfg := newConfig(tt.options...)
-
 			// tested by TestConfigManualReaderOptions
 			cfg.aggregation = nil
 

exporters/prometheus/config.go

@@ -24,6 +24,7 @@ import (
 type config struct {
 	registerer        prometheus.Registerer
 	disableTargetInfo bool
+	withoutUnits      bool
 	aggregation       metric.AggregationSelector
 }
 
@@ -89,3 +90,18 @@ func WithoutTargetInfo() Option {
 		return cfg
 	})
 }
+
+// WithoutUnits disables exporter's addition of unit suffixes to metric names,
+// and will also prevent unit comments from being added in OpenMetrics once
+// unit comments are supported.
+//
+// By default, metric names include a unit suffix to follow Prometheus naming
+// conventions. For example, the counter metric request.duration, with unit
+// milliseconds would become request_duration_milliseconds_total.
+// With this option set, the name would instead be request_duration_total.
+func WithoutUnits() Option {
+	return optionFunc(func(cfg config) config {
+		cfg.withoutUnits = true
+		return cfg
+	})
+}

exporters/prometheus/exporter.go

@@ -27,6 +27,7 @@ import (
 
 	"go.opentelemetry.io/otel"
 	"go.opentelemetry.io/otel/attribute"
+	"go.opentelemetry.io/otel/metric/unit"
 	"go.opentelemetry.io/otel/sdk/metric"
 	"go.opentelemetry.io/otel/sdk/metric/metricdata"
 	"go.opentelemetry.io/otel/sdk/resource"
@@ -50,6 +51,7 @@ type collector struct {
 	reader metric.Reader
 
 	disableTargetInfo    bool
+	withoutUnits         bool
 	targetInfo           *metricData
 	createTargetInfoOnce sync.Once
 }
@@ -70,6 +72,7 @@ func New(opts ...Option) (*Exporter, error) {
 	collector := &collector{
 		reader:            reader,
 		disableTargetInfo: cfg.disableTargetInfo,
+		withoutUnits:      cfg.withoutUnits,
 	}
 
 	if err := cfg.registerer.Register(collector); err != nil {
@@ -151,28 +154,28 @@ func (c *collector) getMetricData(metrics metricdata.ResourceMetrics) []*metricD
 		for _, m := range scopeMetrics.Metrics {
 			switch v := m.Data.(type) {
 			case metricdata.Histogram:
-				allMetrics = append(allMetrics, getHistogramMetricData(v, m)...)
+				allMetrics = append(allMetrics, getHistogramMetricData(v, m, c.getName(m))...)
 			case metricdata.Sum[int64]:
-				allMetrics = append(allMetrics, getSumMetricData(v, m)...)
+				allMetrics = append(allMetrics, getSumMetricData(v, m, c.getName(m))...)
 			case metricdata.Sum[float64]:
-				allMetrics = append(allMetrics, getSumMetricData(v, m)...)
+				allMetrics = append(allMetrics, getSumMetricData(v, m, c.getName(m))...)
 			case metricdata.Gauge[int64]:
-				allMetrics = append(allMetrics, getGaugeMetricData(v, m)...)
+				allMetrics = append(allMetrics, getGaugeMetricData(v, m, c.getName(m))...)
 			case metricdata.Gauge[float64]:
-				allMetrics = append(allMetrics, getGaugeMetricData(v, m)...)
+				allMetrics = append(allMetrics, getGaugeMetricData(v, m, c.getName(m))...)
 			}
 		}
 	}
 
 	return allMetrics
 }
 
-func getHistogramMetricData(histogram metricdata.Histogram, m metricdata.Metrics) []*metricData {
+func getHistogramMetricData(histogram metricdata.Histogram, m metricdata.Metrics, name string) []*metricData {
 	// TODO(https://github.com/open-telemetry/opentelemetry-go/issues/3163): support exemplars
 	dataPoints := make([]*metricData, 0, len(histogram.DataPoints))
 	for _, dp := range histogram.DataPoints {
 		keys, values := getAttrs(dp.Attributes)
-		desc := prometheus.NewDesc(sanitizeName(m.Name), m.Description, keys, nil)
+		desc := prometheus.NewDesc(name, m.Description, keys, nil)
 		buckets := make(map[float64]uint64, len(dp.Bounds))
 
 		cumulativeCount := uint64(0)
@@ -194,15 +197,15 @@ func getHistogramMetricData(histogram metricdata.Histogram, m metricdata.Metrics
 	return dataPoints
 }
 
-func getSumMetricData[N int64 | float64](sum metricdata.Sum[N], m metricdata.Metrics) []*metricData {
+func getSumMetricData[N int64 | float64](sum metricdata.Sum[N], m metricdata.Metrics, name string) []*metricData {
 	valueType := prometheus.CounterValue
 	if !sum.IsMonotonic {
 		valueType = prometheus.GaugeValue
 	}
 	dataPoints := make([]*metricData, 0, len(sum.DataPoints))
 	for _, dp := range sum.DataPoints {
-		name := sanitizeName(m.Name)
 		if sum.IsMonotonic {
+			// Add _total suffix for counters
 			name += counterSuffix
 		}
 		keys, values := getAttrs(dp.Attributes)
@@ -219,11 +222,11 @@ func getSumMetricData[N int64 | float64](sum metricdata.Sum[N], m metricdata.Met
 	return dataPoints
 }
 
-func getGaugeMetricData[N int64 | float64](gauge metricdata.Gauge[N], m metricdata.Metrics) []*metricData {
+func getGaugeMetricData[N int64 | float64](gauge metricdata.Gauge[N], m metricdata.Metrics, name string) []*metricData {
 	dataPoints := make([]*metricData, 0, len(gauge.DataPoints))
 	for _, dp := range gauge.DataPoints {
 		keys, values := getAttrs(dp.Attributes)
-		desc := prometheus.NewDesc(sanitizeName(m.Name), m.Description, keys, nil)
+		desc := prometheus.NewDesc(name, m.Description, keys, nil)
 		md := &metricData{
 			name:            m.Name,
 			description:     desc,
@@ -289,6 +292,24 @@ func sanitizeRune(r rune) rune {
 	return '_'
 }
 
+var unitSuffixes = map[unit.Unit]string{
+	unit.Dimensionless: "_ratio",
+	unit.Bytes:         "_bytes",
+	unit.Milliseconds:  "_milliseconds",
+}
+
+// getName returns the sanitized name, including unit suffix.
+func (c *collector) getName(m metricdata.Metrics) string {
+	name := sanitizeName(m.Name)
+	if c.withoutUnits {
+		return name
+	}
+	if suffix, ok := unitSuffixes[m.Unit]; ok {
+		name += suffix
+	}
+	return name
+}
+
 func sanitizeName(n string) string {
 	// This algorithm is based on strings.Map from Go 1.19.
 	const replacement = '_'

exporters/prometheus/exporter_test.go

@@ -26,6 +26,7 @@ import (
 	"go.opentelemetry.io/otel/attribute"
 	otelmetric "go.opentelemetry.io/otel/metric"
 	"go.opentelemetry.io/otel/metric/instrument"
+	"go.opentelemetry.io/otel/metric/unit"
 	"go.opentelemetry.io/otel/sdk/metric"
 	"go.opentelemetry.io/otel/sdk/metric/aggregation"
 	"go.opentelemetry.io/otel/sdk/metric/view"
@@ -39,7 +40,7 @@ func TestPrometheusExporter(t *testing.T) {
 		emptyResource      bool
 		customResouceAttrs []attribute.KeyValue
 		recordMetrics      func(ctx context.Context, meter otelmetric.Meter)
-		withoutTargetInfo  bool
+		options            []Option
 		expectedFile       string
 	}{
 		{
@@ -52,7 +53,11 @@ func TestPrometheusExporter(t *testing.T) {
 					attribute.Key("E").Bool(true),
 					attribute.Key("F").Int(42),
 				}
-				counter, err := meter.SyncFloat64().Counter("foo", instrument.WithDescription("a simple counter"))
+				counter, err := meter.SyncFloat64().Counter(
+					"foo",
+					instrument.WithDescription("a simple counter"),
+					instrument.WithUnit(unit.Milliseconds),
+				)
 				require.NoError(t, err)
 				counter.Add(ctx, 5, attrs...)
 				counter.Add(ctx, 10.3, attrs...)
@@ -67,10 +72,14 @@ func TestPrometheusExporter(t *testing.T) {
 					attribute.Key("A").String("B"),
 					attribute.Key("C").String("D"),
 				}
-				gauge, err := meter.SyncFloat64().UpDownCounter("bar", instrument.WithDescription("a fun little gauge"))
+				gauge, err := meter.SyncFloat64().UpDownCounter(
+					"bar",
+					instrument.WithDescription("a fun little gauge"),
+					instrument.WithUnit(unit.Dimensionless),
+				)
 				require.NoError(t, err)
-				gauge.Add(ctx, 100, attrs...)
-				gauge.Add(ctx, -25, attrs...)
+				gauge.Add(ctx, 1.0, attrs...)
+				gauge.Add(ctx, -.25, attrs...)
 			},
 		},
 		{
@@ -81,7 +90,11 @@ func TestPrometheusExporter(t *testing.T) {
 					attribute.Key("A").String("B"),
 					attribute.Key("C").String("D"),
 				}
-				histogram, err := meter.SyncFloat64().Histogram("histogram_baz", instrument.WithDescription("a very nice histogram"))
+				histogram, err := meter.SyncFloat64().Histogram(
+					"histogram_baz",
+					instrument.WithDescription("a very nice histogram"),
+					instrument.WithUnit(unit.Bytes),
+				)
 				require.NoError(t, err)
 				histogram.Record(ctx, 23, attrs...)
 				histogram.Record(ctx, 7, attrs...)
@@ -92,6 +105,7 @@ func TestPrometheusExporter(t *testing.T) {
 		{
 			name:         "sanitized attributes to labels",
 			expectedFile: "testdata/sanitized_labels.txt",
+			options:      []Option{WithoutUnits()},
 			recordMetrics: func(ctx context.Context, meter otelmetric.Meter) {
 				attrs := []attribute.KeyValue{
 					// exact match, value should be overwritten
@@ -102,7 +116,12 @@ func TestPrometheusExporter(t *testing.T) {
 					attribute.Key("C.D").String("Y"),
 					attribute.Key("C/D").String("Z"),
 				}
-				counter, err := meter.SyncFloat64().Counter("foo", instrument.WithDescription("a sanitary counter"))
+				counter, err := meter.SyncFloat64().Counter(
+					"foo",
+					instrument.WithDescription("a sanitary counter"),
+					// This unit is not added to
+					instrument.WithUnit(unit.Bytes),
+				)
 				require.NoError(t, err)
 				counter.Add(ctx, 5, attrs...)
 				counter.Add(ctx, 10.3, attrs...)
@@ -177,9 +196,9 @@ func TestPrometheusExporter(t *testing.T) {
 			},
 		},
 		{
-			name:              "without target_info",
-			withoutTargetInfo: true,
-			expectedFile:      "testdata/without_target_info.txt",
+			name:         "without target_info",
+			options:      []Option{WithoutTargetInfo()},
+			expectedFile: "testdata/without_target_info.txt",
 			recordMetrics: func(ctx context.Context, meter otelmetric.Meter) {
 				attrs := []attribute.KeyValue{
 					attribute.Key("A").String("B"),
@@ -200,13 +219,7 @@ func TestPrometheusExporter(t *testing.T) {
 		t.Run(tc.name, func(t *testing.T) {
 			ctx := context.Background()
 			registry := prometheus.NewRegistry()
-
-			opts := []Option{WithRegisterer(registry)}
-			if tc.withoutTargetInfo {
-				opts = append(opts, WithoutTargetInfo())
-			}
-
-			exporter, err := New(opts...)
+			exporter, err := New(append(tc.options, WithRegisterer(registry))...)
 			require.NoError(t, err)
 
 			customBucketsView, err := view.New(

exporters/prometheus/testdata/counter.txt

@@ -1,6 +1,6 @@
-# HELP foo_total a simple counter
-# TYPE foo_total counter
-foo_total{A="B",C="D",E="true",F="42"} 24.3
+# HELP foo_milliseconds_total a simple counter
+# TYPE foo_milliseconds_total counter
+foo_milliseconds_total{A="B",C="D",E="true",F="42"} 24.3
 # HELP target_info Target metadata
 # TYPE target_info gauge
 target_info{service_name="prometheus_test",telemetry_sdk_language="go",telemetry_sdk_name="opentelemetry",telemetry_sdk_version="latest"} 1

exporters/prometheus/testdata/gauge.txt

@@ -1,6 +1,6 @@
-# HELP bar a fun little gauge
-# TYPE bar gauge
-bar{A="B",C="D"} 75
+# HELP bar_ratio a fun little gauge
+# TYPE bar_ratio gauge
+bar_ratio{A="B",C="D"} .75
 # HELP target_info Target metadata
 # TYPE target_info gauge
 target_info{service_name="prometheus_test",telemetry_sdk_language="go",telemetry_sdk_name="opentelemetry",telemetry_sdk_version="latest"} 1

exporters/prometheus/testdata/histogram.txt

@@ -1,18 +1,18 @@
-# HELP histogram_baz a very nice histogram
-# TYPE histogram_baz histogram
-histogram_baz_bucket{A="B",C="D",le="0"} 0
-histogram_baz_bucket{A="B",C="D",le="5"} 0
-histogram_baz_bucket{A="B",C="D",le="10"} 1
-histogram_baz_bucket{A="B",C="D",le="25"} 2
-histogram_baz_bucket{A="B",C="D",le="50"} 2
-histogram_baz_bucket{A="B",C="D",le="75"} 2
-histogram_baz_bucket{A="B",C="D",le="100"} 2
-histogram_baz_bucket{A="B",C="D",le="250"} 4
-histogram_baz_bucket{A="B",C="D",le="500"} 4
-histogram_baz_bucket{A="B",C="D",le="1000"} 4
-histogram_baz_bucket{A="B",C="D",le="+Inf"} 4
-histogram_baz_sum{A="B",C="D"} 236
-histogram_baz_count{A="B",C="D"} 4
+# HELP histogram_baz_bytes a very nice histogram
+# TYPE histogram_baz_bytes histogram
+histogram_baz_bytes_bucket{A="B",C="D",le="0"} 0
+histogram_baz_bytes_bucket{A="B",C="D",le="5"} 0
+histogram_baz_bytes_bucket{A="B",C="D",le="10"} 1
+histogram_baz_bytes_bucket{A="B",C="D",le="25"} 2
+histogram_baz_bytes_bucket{A="B",C="D",le="50"} 2
+histogram_baz_bytes_bucket{A="B",C="D",le="75"} 2
+histogram_baz_bytes_bucket{A="B",C="D",le="100"} 2
+histogram_baz_bytes_bucket{A="B",C="D",le="250"} 4
+histogram_baz_bytes_bucket{A="B",C="D",le="500"} 4
+histogram_baz_bytes_bucket{A="B",C="D",le="1000"} 4
+histogram_baz_bytes_bucket{A="B",C="D",le="+Inf"} 4
+histogram_baz_bytes_sum{A="B",C="D"} 236
+histogram_baz_bytes_count{A="B",C="D"} 4
 # HELP target_info Target metadata
 # TYPE target_info gauge
 target_info{service_name="prometheus_test",telemetry_sdk_language="go",telemetry_sdk_name="opentelemetry",telemetry_sdk_version="latest"} 1