Support default histogram selection in OTLP exporter (#4437)

* Support default histogram selection in OTLP exporter

* Add changes to changelog

CHANGELOG.md

@@ -24,6 +24,7 @@ This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
 - Accept 201 to 299 HTTP status as success in `go.opentelemetry.io/otel/exporters/otlp/otlpmetric/otlpmetrichttp` and `go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracehttp`. (#4365)
 - Document the `Temporality` and `Aggregation` methods of the `"go.opentelemetry.io/otel/sdk/metric".Exporter"` need to be concurrent safe. (#4381)
 - Expand the set of units supported by the prometheus exporter, and don't add unit suffixes if they are already present in `go.opentelemetry.op/otel/exporters/prometheus` (#4374)
+- The exporters in `go.opentelemetry.io/otel/exporters/otlp/otlpmetric/otlpmetricgrpc` and `go.opentelemetry.io/otel/exporters/otlp/otlpmetric/otlpmetrichttp` support the `OTEL_EXPORTER_OTLP_METRICS_DEFAULT_HISTOGRAM_AGGREGATION` environment variable. (#4437)
 
 ### Changed
 

exporters/otlp/otlpmetric/otlpmetricgrpc/internal/oconf/envconfig.go

@@ -29,6 +29,7 @@ import (
 	"go.opentelemetry.io/otel/exporters/otlp/otlpmetric/otlpmetricgrpc/internal/envconfig"
 	"go.opentelemetry.io/otel/internal/global"
 	"go.opentelemetry.io/otel/sdk/metric"
+	"go.opentelemetry.io/otel/sdk/metric/aggregation"
 	"go.opentelemetry.io/otel/sdk/metric/metricdata"
 )
 
@@ -103,6 +104,7 @@ func getOptionsFromEnv() []GenericOption {
 		envconfig.WithDuration("TIMEOUT", func(d time.Duration) { opts = append(opts, WithTimeout(d)) }),
 		envconfig.WithDuration("METRICS_TIMEOUT", func(d time.Duration) { opts = append(opts, WithTimeout(d)) }),
 		withEnvTemporalityPreference("METRICS_TEMPORALITY_PREFERENCE", func(t metric.TemporalitySelector) { opts = append(opts, WithTemporalitySelector(t)) }),
+		withEnvAggPreference("METRICS_DEFAULT_HISTOGRAM_AGGREGATION", func(a metric.AggregationSelector) { opts = append(opts, WithAggregationSelector(a)) }),
 	)
 
 	return opts
@@ -194,3 +196,27 @@ func lowMemory(ik metric.InstrumentKind) metricdata.Temporality {
 		return metricdata.CumulativeTemporality
 	}
 }
+
+func withEnvAggPreference(n string, fn func(metric.AggregationSelector)) func(e *envconfig.EnvOptionsReader) {
+	return func(e *envconfig.EnvOptionsReader) {
+		if s, ok := e.GetEnvValue(n); ok {
+			switch strings.ToLower(s) {
+			case "explicit_bucket_histogram":
+				fn(metric.DefaultAggregationSelector)
+			case "base2_exponential_bucket_histogram":
+				fn(func(kind metric.InstrumentKind) aggregation.Aggregation {
+					if kind == metric.InstrumentKindHistogram {
+						return aggregation.Base2ExponentialHistogram{
+							MaxSize:  160,
+							MaxScale: 20,
+							NoMinMax: false,
+						}
+					}
+					return metric.DefaultAggregationSelector(kind)
+				})
+			default:
+				global.Warn("OTEL_EXPORTER_OTLP_METRICS_DEFAULT_HISTOGRAM_AGGREGATION is set to an invalid value, ignoring.", "value", s)
+			}
+		}
+	}
+}

exporters/otlp/otlpmetric/otlpmetricgrpc/internal/oconf/envconfig_test.go

@@ -24,6 +24,7 @@ import (
 	"github.com/stretchr/testify/require"
 
 	"go.opentelemetry.io/otel/sdk/metric"
+	"go.opentelemetry.io/otel/sdk/metric/aggregation"
 	"go.opentelemetry.io/otel/sdk/metric/metricdata"
 )
 
@@ -104,3 +105,73 @@ func TestWithEnvTemporalityPreference(t *testing.T) {
 	}
 	DefaultEnvOptionsReader.GetEnv = origReader
 }
+
+func TestWithEnvAggPreference(t *testing.T) {
+	origReader := DefaultEnvOptionsReader.GetEnv
+	tests := []struct {
+		name     string
+		envValue string
+		want     map[metric.InstrumentKind]aggregation.Aggregation
+	}{
+		{
+			name:     "default do not set the selector",
+			envValue: "",
+		},
+		{
+			name:     "non-normative do not set the selector",
+			envValue: "non-normative",
+		},
+		{
+			name:     "explicit_bucket_histogram",
+			envValue: "explicit_bucket_histogram",
+			want: map[metric.InstrumentKind]aggregation.Aggregation{
+				metric.InstrumentKindCounter:                 metric.DefaultAggregationSelector(metric.InstrumentKindCounter),
+				metric.InstrumentKindHistogram:               metric.DefaultAggregationSelector(metric.InstrumentKindHistogram),
+				metric.InstrumentKindUpDownCounter:           metric.DefaultAggregationSelector(metric.InstrumentKindUpDownCounter),
+				metric.InstrumentKindObservableCounter:       metric.DefaultAggregationSelector(metric.InstrumentKindObservableCounter),
+				metric.InstrumentKindObservableUpDownCounter: metric.DefaultAggregationSelector(metric.InstrumentKindObservableUpDownCounter),
+				metric.InstrumentKindObservableGauge:         metric.DefaultAggregationSelector(metric.InstrumentKindObservableGauge),
+			},
+		},
+		{
+			name:     "base2_exponential_bucket_histogram",
+			envValue: "base2_exponential_bucket_histogram",
+			want: map[metric.InstrumentKind]aggregation.Aggregation{
+				metric.InstrumentKindCounter: metric.DefaultAggregationSelector(metric.InstrumentKindCounter),
+				metric.InstrumentKindHistogram: aggregation.Base2ExponentialHistogram{
+					MaxSize:  160,
+					MaxScale: 20,
+					NoMinMax: false,
+				},
+				metric.InstrumentKindUpDownCounter:           metric.DefaultAggregationSelector(metric.InstrumentKindUpDownCounter),
+				metric.InstrumentKindObservableCounter:       metric.DefaultAggregationSelector(metric.InstrumentKindObservableCounter),
+				metric.InstrumentKindObservableUpDownCounter: metric.DefaultAggregationSelector(metric.InstrumentKindObservableUpDownCounter),
+				metric.InstrumentKindObservableGauge:         metric.DefaultAggregationSelector(metric.InstrumentKindObservableGauge),
+			},
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			DefaultEnvOptionsReader.GetEnv = func(key string) string {
+				if key == "OTEL_EXPORTER_OTLP_METRICS_DEFAULT_HISTOGRAM_AGGREGATION" {
+					return tt.envValue
+				}
+				return origReader(key)
+			}
+			cfg := Config{}
+			cfg = ApplyGRPCEnvConfigs(cfg)
+
+			if tt.want == nil {
+				// There is no function set, the SDK's default is used.
+				assert.Nil(t, cfg.Metrics.AggregationSelector)
+				return
+			}
+
+			require.NotNil(t, cfg.Metrics.AggregationSelector)
+			for ik, want := range tt.want {
+				assert.Equal(t, want, cfg.Metrics.AggregationSelector(ik))
+			}
+		})
+	}
+	DefaultEnvOptionsReader.GetEnv = origReader
+}

exporters/otlp/otlpmetric/otlpmetrichttp/internal/oconf/envconfig.go

@@ -29,6 +29,7 @@ import (
 	"go.opentelemetry.io/otel/exporters/otlp/otlpmetric/otlpmetrichttp/internal/envconfig"
 	"go.opentelemetry.io/otel/internal/global"
 	"go.opentelemetry.io/otel/sdk/metric"
+	"go.opentelemetry.io/otel/sdk/metric/aggregation"
 	"go.opentelemetry.io/otel/sdk/metric/metricdata"
 )
 
@@ -103,6 +104,7 @@ func getOptionsFromEnv() []GenericOption {
 		envconfig.WithDuration("TIMEOUT", func(d time.Duration) { opts = append(opts, WithTimeout(d)) }),
 		envconfig.WithDuration("METRICS_TIMEOUT", func(d time.Duration) { opts = append(opts, WithTimeout(d)) }),
 		withEnvTemporalityPreference("METRICS_TEMPORALITY_PREFERENCE", func(t metric.TemporalitySelector) { opts = append(opts, WithTemporalitySelector(t)) }),
+		withEnvAggPreference("METRICS_DEFAULT_HISTOGRAM_AGGREGATION", func(a metric.AggregationSelector) { opts = append(opts, WithAggregationSelector(a)) }),
 	)
 
 	return opts
@@ -194,3 +196,27 @@ func lowMemory(ik metric.InstrumentKind) metricdata.Temporality {
 		return metricdata.CumulativeTemporality
 	}
 }
+
+func withEnvAggPreference(n string, fn func(metric.AggregationSelector)) func(e *envconfig.EnvOptionsReader) {
+	return func(e *envconfig.EnvOptionsReader) {
+		if s, ok := e.GetEnvValue(n); ok {
+			switch strings.ToLower(s) {
+			case "explicit_bucket_histogram":
+				fn(metric.DefaultAggregationSelector)
+			case "base2_exponential_bucket_histogram":
+				fn(func(kind metric.InstrumentKind) aggregation.Aggregation {
+					if kind == metric.InstrumentKindHistogram {
+						return aggregation.Base2ExponentialHistogram{
+							MaxSize:  160,
+							MaxScale: 20,
+							NoMinMax: false,
+						}
+					}
+					return metric.DefaultAggregationSelector(kind)
+				})
+			default:
+				global.Warn("OTEL_EXPORTER_OTLP_METRICS_DEFAULT_HISTOGRAM_AGGREGATION is set to an invalid value, ignoring.", "value", s)
+			}
+		}
+	}
+}

exporters/otlp/otlpmetric/otlpmetrichttp/internal/oconf/envconfig_test.go

@@ -24,6 +24,7 @@ import (
 	"github.com/stretchr/testify/require"
 
 	"go.opentelemetry.io/otel/sdk/metric"
+	"go.opentelemetry.io/otel/sdk/metric/aggregation"
 	"go.opentelemetry.io/otel/sdk/metric/metricdata"
 )
 
@@ -104,3 +105,73 @@ func TestWithEnvTemporalityPreference(t *testing.T) {
 	}
 	DefaultEnvOptionsReader.GetEnv = origReader
 }
+
+func TestWithEnvAggPreference(t *testing.T) {
+	origReader := DefaultEnvOptionsReader.GetEnv
+	tests := []struct {
+		name     string
+		envValue string
+		want     map[metric.InstrumentKind]aggregation.Aggregation
+	}{
+		{
+			name:     "default do not set the selector",
+			envValue: "",
+		},
+		{
+			name:     "non-normative do not set the selector",
+			envValue: "non-normative",
+		},
+		{
+			name:     "explicit_bucket_histogram",
+			envValue: "explicit_bucket_histogram",
+			want: map[metric.InstrumentKind]aggregation.Aggregation{
+				metric.InstrumentKindCounter:                 metric.DefaultAggregationSelector(metric.InstrumentKindCounter),
+				metric.InstrumentKindHistogram:               metric.DefaultAggregationSelector(metric.InstrumentKindHistogram),
+				metric.InstrumentKindUpDownCounter:           metric.DefaultAggregationSelector(metric.InstrumentKindUpDownCounter),
+				metric.InstrumentKindObservableCounter:       metric.DefaultAggregationSelector(metric.InstrumentKindObservableCounter),
+				metric.InstrumentKindObservableUpDownCounter: metric.DefaultAggregationSelector(metric.InstrumentKindObservableUpDownCounter),
+				metric.InstrumentKindObservableGauge:         metric.DefaultAggregationSelector(metric.InstrumentKindObservableGauge),
+			},
+		},
+		{
+			name:     "base2_exponential_bucket_histogram",
+			envValue: "base2_exponential_bucket_histogram",
+			want: map[metric.InstrumentKind]aggregation.Aggregation{
+				metric.InstrumentKindCounter: metric.DefaultAggregationSelector(metric.InstrumentKindCounter),
+				metric.InstrumentKindHistogram: aggregation.Base2ExponentialHistogram{
+					MaxSize:  160,
+					MaxScale: 20,
+					NoMinMax: false,
+				},
+				metric.InstrumentKindUpDownCounter:           metric.DefaultAggregationSelector(metric.InstrumentKindUpDownCounter),
+				metric.InstrumentKindObservableCounter:       metric.DefaultAggregationSelector(metric.InstrumentKindObservableCounter),
+				metric.InstrumentKindObservableUpDownCounter: metric.DefaultAggregationSelector(metric.InstrumentKindObservableUpDownCounter),
+				metric.InstrumentKindObservableGauge:         metric.DefaultAggregationSelector(metric.InstrumentKindObservableGauge),
+			},
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			DefaultEnvOptionsReader.GetEnv = func(key string) string {
+				if key == "OTEL_EXPORTER_OTLP_METRICS_DEFAULT_HISTOGRAM_AGGREGATION" {
+					return tt.envValue
+				}
+				return origReader(key)
+			}
+			cfg := Config{}
+			cfg = ApplyGRPCEnvConfigs(cfg)
+
+			if tt.want == nil {
+				// There is no function set, the SDK's default is used.
+				assert.Nil(t, cfg.Metrics.AggregationSelector)
+				return
+			}
+
+			require.NotNil(t, cfg.Metrics.AggregationSelector)
+			for ik, want := range tt.want {
+				assert.Equal(t, want, cfg.Metrics.AggregationSelector(ik))
+			}
+		})
+	}
+	DefaultEnvOptionsReader.GetEnv = origReader
+}

internal/shared/otlp/otlpmetric/oconf/envconfig.go.tmpl

@@ -29,6 +29,7 @@ import (
 	"{{ .envconfigImportPath }}"
 	"go.opentelemetry.io/otel/internal/global"
 	"go.opentelemetry.io/otel/sdk/metric"
+	"go.opentelemetry.io/otel/sdk/metric/aggregation"
 	"go.opentelemetry.io/otel/sdk/metric/metricdata"
 )
 
@@ -103,6 +104,7 @@ func getOptionsFromEnv() []GenericOption {
 		envconfig.WithDuration("TIMEOUT", func(d time.Duration) { opts = append(opts, WithTimeout(d)) }),
 		envconfig.WithDuration("METRICS_TIMEOUT", func(d time.Duration) { opts = append(opts, WithTimeout(d)) }),
 		withEnvTemporalityPreference("METRICS_TEMPORALITY_PREFERENCE", func(t metric.TemporalitySelector) { opts = append(opts, WithTemporalitySelector(t)) }),
+		withEnvAggPreference("METRICS_DEFAULT_HISTOGRAM_AGGREGATION", func(a metric.AggregationSelector) { opts = append(opts, WithAggregationSelector(a)) }),
 	)
 
 	return opts
@@ -194,3 +196,27 @@ func lowMemory(ik metric.InstrumentKind) metricdata.Temporality {
 		return metricdata.CumulativeTemporality
 	}
 }
+
+func withEnvAggPreference(n string, fn func(metric.AggregationSelector)) func(e *envconfig.EnvOptionsReader) {
+	return func(e *envconfig.EnvOptionsReader) {
+		if s, ok := e.GetEnvValue(n); ok {
+			switch strings.ToLower(s) {
+			case "explicit_bucket_histogram":
+				fn(metric.DefaultAggregationSelector)
+			case "base2_exponential_bucket_histogram":
+				fn(func(kind metric.InstrumentKind) aggregation.Aggregation {
+					if kind == metric.InstrumentKindHistogram {
+						return aggregation.Base2ExponentialHistogram{
+							MaxSize:  160,
+							MaxScale: 20,
+							NoMinMax: false,
+						}
+					}
+					return metric.DefaultAggregationSelector(kind)
+				})
+			default:
+				global.Warn("OTEL_EXPORTER_OTLP_METRICS_DEFAULT_HISTOGRAM_AGGREGATION is set to an invalid value, ignoring.", "value", s)
+			}
+		}
+	}
+}

internal/shared/otlp/otlpmetric/oconf/envconfig_test.go.tmpl

@@ -24,6 +24,7 @@ import (
 	"github.com/stretchr/testify/require"
 
 	"go.opentelemetry.io/otel/sdk/metric"
+	"go.opentelemetry.io/otel/sdk/metric/aggregation"
 	"go.opentelemetry.io/otel/sdk/metric/metricdata"
 )
 
@@ -104,3 +105,73 @@ func TestWithEnvTemporalityPreference(t *testing.T) {
 	}
 	DefaultEnvOptionsReader.GetEnv = origReader
 }
+
+func TestWithEnvAggPreference(t *testing.T) {
+	origReader := DefaultEnvOptionsReader.GetEnv
+	tests := []struct {
+		name     string
+		envValue string
+		want     map[metric.InstrumentKind]aggregation.Aggregation
+	}{
+		{
+			name:     "default do not set the selector",
+			envValue: "",
+		},
+		{
+			name:     "non-normative do not set the selector",
+			envValue: "non-normative",
+		},
+		{
+			name:     "explicit_bucket_histogram",
+			envValue: "explicit_bucket_histogram",
+			want: map[metric.InstrumentKind]aggregation.Aggregation{
+				metric.InstrumentKindCounter:                 metric.DefaultAggregationSelector(metric.InstrumentKindCounter),
+				metric.InstrumentKindHistogram:               metric.DefaultAggregationSelector(metric.InstrumentKindHistogram),
+				metric.InstrumentKindUpDownCounter:           metric.DefaultAggregationSelector(metric.InstrumentKindUpDownCounter),
+				metric.InstrumentKindObservableCounter:       metric.DefaultAggregationSelector(metric.InstrumentKindObservableCounter),
+				metric.InstrumentKindObservableUpDownCounter: metric.DefaultAggregationSelector(metric.InstrumentKindObservableUpDownCounter),
+				metric.InstrumentKindObservableGauge:         metric.DefaultAggregationSelector(metric.InstrumentKindObservableGauge),
+			},
+		},
+		{
+			name:     "base2_exponential_bucket_histogram",
+			envValue: "base2_exponential_bucket_histogram",
+			want: map[metric.InstrumentKind]aggregation.Aggregation{
+				metric.InstrumentKindCounter: metric.DefaultAggregationSelector(metric.InstrumentKindCounter),
+				metric.InstrumentKindHistogram: aggregation.Base2ExponentialHistogram{
+					MaxSize:  160,
+					MaxScale: 20,
+					NoMinMax: false,
+				},
+				metric.InstrumentKindUpDownCounter:           metric.DefaultAggregationSelector(metric.InstrumentKindUpDownCounter),
+				metric.InstrumentKindObservableCounter:       metric.DefaultAggregationSelector(metric.InstrumentKindObservableCounter),
+				metric.InstrumentKindObservableUpDownCounter: metric.DefaultAggregationSelector(metric.InstrumentKindObservableUpDownCounter),
+				metric.InstrumentKindObservableGauge:         metric.DefaultAggregationSelector(metric.InstrumentKindObservableGauge),
+			},
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			DefaultEnvOptionsReader.GetEnv = func(key string) string {
+				if key == "OTEL_EXPORTER_OTLP_METRICS_DEFAULT_HISTOGRAM_AGGREGATION" {
+					return tt.envValue
+				}
+				return origReader(key)
+			}
+			cfg := Config{}
+			cfg = ApplyGRPCEnvConfigs(cfg)
+
+			if tt.want == nil {
+				// There is no function set, the SDK's default is used.
+				assert.Nil(t, cfg.Metrics.AggregationSelector)
+				return
+			}
+
+			require.NotNil(t, cfg.Metrics.AggregationSelector)
+			for ik, want := range tt.want {
+				assert.Equal(t, want, cfg.Metrics.AggregationSelector(ik))
+			}
+		})
+	}
+	DefaultEnvOptionsReader.GetEnv = origReader
+}