sdk/resource: add WithContext variants for Default and Environment (#7808)

CHANGELOG.md

@@ -12,6 +12,7 @@ This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
 
 - Add `IsRandom` and `WithRandom` on `TraceFlags`, and `IsRandom` on `SpanContext` in `go.opentelemetry.io/otel/trace` for [W3C Trace Context Level 2 Random Trace ID Flag](https://www.w3.org/TR/trace-context-2/#random-trace-id-flag) support. (#8012)
 - Add service detection with `WithService` in `go.opentelemetry.io/otel/sdk/resource`. (#7642)
+- Add `DefaultWithContext` and `EnvironmentWithContext` in `go.opentelemetry.io/otel/sdk/resource` to support plumbing `context.Context` through default and environment detectors. (#8051)
 - Support attributes with empty value (`attribute.EMPTY`) in OTLP exporters (`go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracegrpc`, `go.opentelemetry.io/otel/exporters/otlp/otlpmetric/otlpmetricgrpc`, `go.opentelemetry.io/otel/exporters/otlp/otlplog/otlploggrpc`, `go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracehttp`, `go.opentelemetry.io/otel/exporters/otlp/otlpmetric/otlpmetrichttp`, `go.opentelemetry.io/otel/exporters/otlp/otlplog/otlploghttp`). (#8038)
 - Support attributes with empty value (`attribute.EMPTY`) in `go.opentelemetry.io/otel/sdk/metric/metricdata/metricdatatest`. (#8038)
 

sdk/resource/resource.go

@@ -232,6 +232,15 @@ func Empty() *Resource {
 // Default returns an instance of Resource with a default
 // "service.name" and OpenTelemetrySDK attributes.
 func Default() *Resource {
+	return DefaultWithContext(context.Background())
+}
+
+// DefaultWithContext returns an instance of Resource with a default
+// "service.name" and OpenTelemetrySDK attributes.
+//
+// If the default resource has already been initialized, the provided ctx
+// is ignored and the cached resource is returned.
+func DefaultWithContext(ctx context.Context) *Resource {
 	defaultResourceOnce.Do(func() {
 		var err error
 		defaultDetectors := []Detector{
@@ -243,7 +252,7 @@ func Default() *Resource {
 			defaultDetectors = append([]Detector{defaultServiceInstanceIDDetector{}}, defaultDetectors...)
 		}
 		defaultResource, err = Detect(
-			context.Background(),
+			ctx,
 			defaultDetectors...,
 		)
 		if err != nil {
@@ -260,8 +269,14 @@ func Default() *Resource {
 // Environment returns an instance of Resource with attributes
 // extracted from the OTEL_RESOURCE_ATTRIBUTES environment variable.
 func Environment() *Resource {
+	return EnvironmentWithContext(context.Background())
+}
+
+// EnvironmentWithContext returns an instance of Resource with attributes
+// extracted from the OTEL_RESOURCE_ATTRIBUTES environment variable.
+func EnvironmentWithContext(ctx context.Context) *Resource {
 	detector := &fromEnv{}
-	resource, err := detector.Detect(context.Background())
+	resource, err := detector.Detect(ctx)
 	if err != nil {
 		otel.Handle(err)
 	}

sdk/resource/resource_test.go

@@ -249,6 +249,20 @@ func TestDefault(t *testing.T) {
 	require.Contains(t, res.Attributes(), semconv.TelemetrySDKName("opentelemetry"))
 }
 
+func TestDefaultWithContext(t *testing.T) {
+	ctx := t.Context()
+	res1 := resource.DefaultWithContext(ctx)
+	res2 := resource.DefaultWithContext(ctx)
+	assert.Same(t, res1, res2)
+}
+
+func TestEnvironmentWithContext(t *testing.T) {
+	t.Setenv(envVar, "key=value")
+	ctx := t.Context()
+	res := resource.EnvironmentWithContext(ctx)
+	assert.Equal(t, map[string]string{"key": "value"}, toMap(res))
+}
+
 func TestEquivalentStability(t *testing.T) {
 	r1 := resource.NewSchemaless(
 		attribute.String("a", "1"),