Add otlpmetric Temporality Preference env var

CHANGELOG.md

@@ -14,6 +14,7 @@ This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
 - Add `PeriodicReader` struct in `go.opentelemetry.io/otel/sdk/metric`. (#4244)
 - Add `Exporter` struct in `go.opentelemetry.io/otel/exporters/otlp/otlpmetric/otlpmetricgrpc`. (#4272)
 - Add `Exporter` struct in `go.opentelemetry.io/otel/exporters/otlp/otlpmetric/otlpmetrichttp`. (#4272)
+- OTLP Metrics Exporter now supports the `OTEL_EXPORTER_OTLP_METRICS_TEMPORALITY_PREFERENCE` environment variable. (#4287)
 
 ### Changed
 

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

@@ -24,6 +24,8 @@ import (
 	"time"
 
 	"go.opentelemetry.io/otel/exporters/otlp/internal/envconfig"
+	"go.opentelemetry.io/otel/sdk/metric"
+	"go.opentelemetry.io/otel/sdk/metric/metricdata"
 )
 
 // DefaultEnvOptionsReader is the default environments reader.
@@ -96,6 +98,7 @@ func getOptionsFromEnv() []GenericOption {
 		WithEnvCompression("METRICS_COMPRESSION", func(c Compression) { opts = append(opts, WithCompression(c)) }),
 		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)) }),
 	)
 
 	return opts
@@ -148,3 +151,38 @@ func withTLSConfig(c *tls.Config, fn func(*tls.Config)) func(e *envconfig.EnvOpt
 		}
 	}
 }
+
+func withEnvTemporalityPreference(n string, fn func(metric.TemporalitySelector)) func(e *envconfig.EnvOptionsReader) {
+	return func(e *envconfig.EnvOptionsReader) {
+		if s, ok := e.GetEnvValue(n); ok {
+			switch strings.ToLower(s) {
+			case "cumulative":
+				fn(cumulativeTemporality)
+			case "delta":
+				fn(deltaTemporality)
+			case "lowmemory":
+				fn(lowMemory)
+			}
+		}
+	}
+}
+
+func cumulativeTemporality(metric.InstrumentKind) metricdata.Temporality {
+	return metricdata.CumulativeTemporality
+}
+func deltaTemporality(ik metric.InstrumentKind) metricdata.Temporality {
+	switch ik {
+	case metric.InstrumentKindCounter, metric.InstrumentKindHistogram, metric.InstrumentKindObservableCounter:
+		return metricdata.DeltaTemporality
+	default:
+		return metricdata.CumulativeTemporality
+	}
+}
+func lowMemory(ik metric.InstrumentKind) metricdata.Temporality {
+	switch ik {
+	case metric.InstrumentKindCounter, metric.InstrumentKindHistogram:
+		return metricdata.DeltaTemporality
+	default:
+		return metricdata.CumulativeTemporality
+	}
+}

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

@@ -0,0 +1,102 @@
+// Copyright The OpenTelemetry Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package oconf
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	"go.opentelemetry.io/otel/sdk/metric"
+	"go.opentelemetry.io/otel/sdk/metric/metricdata"
+)
+
+func TestWithEnvTemporalityPreference(t *testing.T) {
+	origReader := DefaultEnvOptionsReader.GetEnv
+	tests := []struct {
+		name     string
+		envValue string
+		want     map[metric.InstrumentKind]metricdata.Temporality
+	}{
+		{
+			name:     "default do not set the selector",
+			envValue: "",
+		},
+		{
+			name:     "non-normative do not set the selector",
+			envValue: "non-normative",
+		},
+		{
+			name:     "cumulative",
+			envValue: "cumulative",
+			want: map[metric.InstrumentKind]metricdata.Temporality{
+				metric.InstrumentKindCounter:                 metricdata.CumulativeTemporality,
+				metric.InstrumentKindHistogram:               metricdata.CumulativeTemporality,
+				metric.InstrumentKindUpDownCounter:           metricdata.CumulativeTemporality,
+				metric.InstrumentKindObservableCounter:       metricdata.CumulativeTemporality,
+				metric.InstrumentKindObservableUpDownCounter: metricdata.CumulativeTemporality,
+				metric.InstrumentKindObservableGauge:         metricdata.CumulativeTemporality,
+			},
+		},
+		{
+			name:     "delta",
+			envValue: "delta",
+			want: map[metric.InstrumentKind]metricdata.Temporality{
+				metric.InstrumentKindCounter:                 metricdata.DeltaTemporality,
+				metric.InstrumentKindHistogram:               metricdata.DeltaTemporality,
+				metric.InstrumentKindUpDownCounter:           metricdata.CumulativeTemporality,
+				metric.InstrumentKindObservableCounter:       metricdata.DeltaTemporality,
+				metric.InstrumentKindObservableUpDownCounter: metricdata.CumulativeTemporality,
+				metric.InstrumentKindObservableGauge:         metricdata.CumulativeTemporality,
+			},
+		},
+		{
+			name:     "lowmemory",
+			envValue: "lowmemory",
+			want: map[metric.InstrumentKind]metricdata.Temporality{
+				metric.InstrumentKindCounter:                 metricdata.DeltaTemporality,
+				metric.InstrumentKindHistogram:               metricdata.DeltaTemporality,
+				metric.InstrumentKindUpDownCounter:           metricdata.CumulativeTemporality,
+				metric.InstrumentKindObservableCounter:       metricdata.CumulativeTemporality,
+				metric.InstrumentKindObservableUpDownCounter: metricdata.CumulativeTemporality,
+				metric.InstrumentKindObservableGauge:         metricdata.CumulativeTemporality,
+			},
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			DefaultEnvOptionsReader.GetEnv = func(key string) string {
+				if key == "OTEL_EXPORTER_OTLP_METRICS_TEMPORALITY_PREFERENCE" {
+					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.TemporalitySelector)
+				return
+			}
+
+			require.NotNil(t, cfg.Metrics.TemporalitySelector)
+			for ik, want := range tt.want {
+				assert.Equal(t, want, cfg.Metrics.TemporalitySelector(ik))
+			}
+		})
+	}
+	DefaultEnvOptionsReader.GetEnv = origReader
+}