autoexport: OTLP exporter defaults to http/protobuf protocol instead of grpc

CHANGELOG.md

@@ -12,7 +12,7 @@ This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
 
 - Add `NewMiddleware` function in `go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp`. (#2964)
 - Add the new `go.opentelemetry.io/contrib/instrgen` package to provide auto-generated source code instrumentation. (#3068, #3108)
-- The `go.opentelemetry.io/contrib/exporters/autoexport` package to provide configuration of trace exporters with useful defaults and envar support. (#2753)
+- The `go.opentelemetry.io/contrib/exporters/autoexport` package to provide configuration of trace exporters with useful defaults and envar support. (#2753, #4100)
 
 ### Fixed
 

exporters/autoexport/exporter.go

@@ -90,8 +90,8 @@ func NewSpanExporter(ctx context.Context, opts ...Option) (trace.SpanExporter, e
 // environment variable.
 // nil is returned if no exporter is defined for the environment variable.
 func makeExporterFromEnv(ctx context.Context) (trace.SpanExporter, error) {
-	expType, defined := os.LookupEnv(otelTracesExportersEnvKey)
-	if !defined {
+	expType := os.Getenv(otelTracesExportersEnvKey)
+	if expType == "" {
 		return nil, nil
 	}
 	return spanExporter(ctx, expType)

exporters/autoexport/exporter_test.go

@@ -16,6 +16,7 @@ package autoexport
 
 import (
 	"context"
+	"reflect"
 	"testing"
 
 	"github.com/stretchr/testify/assert"
@@ -26,7 +27,7 @@ import (
 
 func TestOTLPExporterReturnedWhenNoEnvOrFallbackExporterConfigured(t *testing.T) {
 	exporter, err := NewSpanExporter(context.Background())
-	assert.Nil(t, err)
+	assert.NoError(t, err)
 	assert.NotNil(t, exporter)
 	assert.IsType(t, &otlptrace.Exporter{}, exporter)
 }
@@ -37,7 +38,7 @@ func TestFallbackExporterReturnedWhenNoEnvExporterConfigured(t *testing.T) {
 		context.Background(),
 		WithFallbackSpanExporter(testExporter),
 	)
-	assert.Nil(t, err)
+	assert.NoError(t, err)
 	assert.Equal(t, testExporter, exporter)
 }
 
@@ -49,8 +50,59 @@ func TestEnvExporterIsPreferredOverFallbackExporter(t *testing.T) {
 		context.Background(),
 		WithFallbackSpanExporter(testExporter),
 	)
-	assert.Nil(t, err)
-	assert.IsType(t, &otlptrace.Exporter{}, exporter)
+	assert.NoError(t, err)
+	assertOTLPHTTPExporter(t, exporter)
+}
+
+func TestEnvExporterOTLPOverHTTP(t *testing.T) {
+	t.Setenv("OTEL_TRACES_EXPORTER", "otlp")
+	t.Setenv("OTEL_EXPORTER_OTLP_PROTOCOL", "http/protobuf")
+
+	exporter, err := NewSpanExporter(context.Background())
+	assert.NoError(t, err)
+	assertOTLPHTTPExporter(t, exporter)
+}
+
+func TestEnvExporterOTLPOverGRPC(t *testing.T) {
+	t.Setenv("OTEL_TRACES_EXPORTER", "otlp")
+	t.Setenv("OTEL_EXPORTER_OTLP_PROTOCOL", "grpc")
+
+	exporter, err := NewSpanExporter(context.Background())
+	assert.NoError(t, err)
+	assertOTLPGRPCExporter(t, exporter)
+}
+
+func TestEnvExporterOTLPInvalidProtocol(t *testing.T) {
+	t.Setenv("OTEL_TRACES_EXPORTER", "otlp")
+	t.Setenv("OTEL_EXPORTER_OTLP_PROTOCOL", "invalid")
+
+	exporter, err := NewSpanExporter(context.Background())
+	assert.Error(t, err)
+	assert.Nil(t, exporter)
+}
+
+func assertOTLPHTTPExporter(t *testing.T, got trace.SpanExporter) {
+	t.Helper()
+
+	if !assert.IsType(t, &otlptrace.Exporter{}, got) {
+		return
+	}
+
+	// Implementation detail hack. This may break when bumping OTLP exporter modules as it uses unexported API.
+	clientType := reflect.Indirect(reflect.ValueOf(got)).FieldByName("client").Elem().Type().String()
+	assert.Equal(t, "*otlptracehttp.client", clientType)
+}
+
+func assertOTLPGRPCExporter(t *testing.T, got trace.SpanExporter) {
+	t.Helper()
+
+	if !assert.IsType(t, &otlptrace.Exporter{}, got) {
+		return
+	}
+
+	// Implementation detail hack. This may break when bumping OTLP exporter modules as it uses unexported API.
+	clientType := reflect.Indirect(reflect.ValueOf(got)).FieldByName("client").Elem().Type().String()
+	assert.Equal(t, "*otlptracegrpc.client", clientType)
 }
 
 type testExporter struct{}

exporters/autoexport/registry.go

@@ -130,10 +130,11 @@ func spanExporter(ctx context.Context, name string) (trace.SpanExporter, error)
 
 // buildOTLPExporter creates an OTLP exporter using the environment variable
 // OTEL_EXPORTER_OTLP_PROTOCOL to determine the exporter protocol.
+// Defaults to http/protobuf protocol.
 func buildOTLPExporter(ctx context.Context) (trace.SpanExporter, error) {
-	proto := "grpc"
-	if protoStr, ok := os.LookupEnv(otelExporterOTLPProtoEnvKey); ok {
-		proto = protoStr
+	proto := os.Getenv(otelExporterOTLPProtoEnvKey)
+	if proto == "" {
+		proto = "http/protobuf"
 	}
 
 	switch proto {

exporters/autoexport/registry_test.go

@@ -75,7 +75,7 @@ func TestRegistryIsConcurrentSafe(t *testing.T) {
 		defer wg.Done()
 		assert.NotPanics(t, func() {
 			exp, err := r.load(context.Background(), exporterName)
-			assert.Nil(t, err, "missing exporter in registry")
+			assert.NoError(t, err, "missing exporter in registry")
 			assert.IsType(t, &stdouttrace.Exporter{}, exp)
 		})
 	}()
@@ -86,12 +86,13 @@ func TestRegistryIsConcurrentSafe(t *testing.T) {
 func TestSubsequentCallsToGetExporterReturnsNewInstances(t *testing.T) {
 	const exporterType = "otlp"
 	exp1, err := spanExporter(context.Background(), exporterType)
-	assert.Nil(t, err)
-	assert.IsType(t, &otlptrace.Exporter{}, exp1)
+	assert.NoError(t, err)
+	assertOTLPHTTPExporter(t, exp1)
 
 	exp2, err := spanExporter(context.Background(), exporterType)
-	assert.Nil(t, err)
-	assert.IsType(t, &otlptrace.Exporter{}, exp2)
+	assert.NoError(t, err)
+	assertOTLPHTTPExporter(t, exp2)
+
 	assert.NotSame(t, exp1, exp2)
 }