support console key in trace/metric exporter env var config

This adds support for the standard output exporter for traces and metrics. To remain consistent with other implementations, i used the key `console` as the identifier for the exporter. This change is related to the specification pull request open-telemetry/opentelemetry-specification#3742

Signed-off-by: Alex Boten <[email protected]>

CHANGELOG.md

@@ -15,6 +15,7 @@ This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
 - Add `"go.opentelemetry.io/contrib/config"` package that includes configuration models generated via go-jsonschema. (#4376)
 - Add `NewSDK` function to `"go.opentelemetry.io/contrib/config"`. The initial implementation only returns noop providers. (#4414)
 - Add metrics support to `go.opentelemetry.io/contrib/exporters/autoexport`. (#4229)
+- Add support for standard output exporter via environment variables for the metric and trace signals identified by the key: `console`. ()
 
 ### Changed
 

exporters/autoexport/metrics.go

@@ -20,6 +20,7 @@ import (
 
 	"go.opentelemetry.io/otel/exporters/otlp/otlpmetric/otlpmetricgrpc"
 	"go.opentelemetry.io/otel/exporters/otlp/otlpmetric/otlpmetrichttp"
+	"go.opentelemetry.io/otel/exporters/stdout/stdoutmetric"
 	"go.opentelemetry.io/otel/sdk/metric"
 )
 
@@ -38,6 +39,7 @@ func WithFallbackMetricReader(exporter metric.Reader) MetricOption {
 // OTEL_METRICS_EXPORTER defines the metrics exporter; supported values:
 //   - "none" - "no operation" exporter
 //   - "otlp" (default) - OTLP exporter; see [go.opentelemetry.io/otel/exporters/otlp/otlpmetric]
+//   - "console" - Standard output exporter; see [https://pkg.go.dev/go.opentelemetry.io/otel/exporters/stdout/stdoutmetric]
 //
 // OTEL_EXPORTER_OTLP_PROTOCOL defines OTLP exporter's transport protocol;
 // supported values:
@@ -91,6 +93,13 @@ func init() {
 			return nil, errInvalidOTLPProtocol
 		}
 	})
+	RegisterMetricReader("console", func(ctx context.Context) (metric.Reader, error) {
+		r, err := stdoutmetric.New()
+		if err != nil {
+			return nil, err
+		}
+		return metric.NewPeriodicReader(r), nil
+	})
 	RegisterMetricReader("none", func(ctx context.Context) (metric.Reader, error) {
 		return newNoopMetricReader(), nil
 	})

exporters/autoexport/metrics_test.go

@@ -32,6 +32,15 @@ func TestMetricExporterNone(t *testing.T) {
 	assert.True(t, IsNoneMetricReader(got))
 }
 
+func TestMetricExporterConsole(t *testing.T) {
+	t.Setenv("OTEL_METRICS_EXPORTER", "console")
+	got, err := NewMetricReader(context.Background())
+	assert.NoError(t, err)
+	assert.IsType(t, &metric.PeriodicReader{}, got)
+	exporterType := reflect.Indirect(reflect.ValueOf(got)).FieldByName("exporter").Elem().Type()
+	assert.Equal(t, "*stdoutmetric.exporter", exporterType.String())
+}
+
 func TestMetricExporterOTLP(t *testing.T) {
 	t.Setenv("OTEL_METRICS_EXPORTER", "otlp")
 

exporters/autoexport/spans.go

@@ -20,6 +20,7 @@ import (
 
 	"go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracegrpc"
 	"go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracehttp"
+	"go.opentelemetry.io/otel/exporters/stdout/stdouttrace"
 	"go.opentelemetry.io/otel/sdk/trace"
 )
 
@@ -43,6 +44,7 @@ func WithFallbackSpanExporter(exporter trace.SpanExporter) SpanOption {
 // OTEL_TRACES_EXPORTER defines the traces exporter; supported values:
 //   - "none" - "no operation" exporter
 //   - "otlp" (default) - OTLP exporter; see [go.opentelemetry.io/otel/exporters/otlp/otlptrace]
+//   - "console" - Standard output exporter; see [https://pkg.go.dev/go.opentelemetry.io/otel/exporters/stdout/stdouttrace]
 //
 // OTEL_EXPORTER_OTLP_PROTOCOL defines OTLP exporter's transport protocol;
 // supported values:
@@ -88,6 +90,9 @@ func init() {
 			return nil, errInvalidOTLPProtocol
 		}
 	})
+	RegisterSpanExporter("console", func(ctx context.Context) (trace.SpanExporter, error) {
+		return stdouttrace.New()
+	})
 	RegisterSpanExporter("none", func(ctx context.Context) (trace.SpanExporter, error) {
 		return noopSpanExporter{}, nil
 	})

exporters/autoexport/spans_test.go

@@ -21,6 +21,7 @@ import (
 	"testing"
 
 	"go.opentelemetry.io/otel/exporters/otlp/otlptrace"
+	"go.opentelemetry.io/otel/exporters/stdout/stdouttrace"
 
 	"github.com/stretchr/testify/assert"
 )
@@ -32,6 +33,13 @@ func TestSpanExporterNone(t *testing.T) {
 	assert.True(t, IsNoneSpanExporter(got))
 }
 
+func TestSpanExporterConsole(t *testing.T) {
+	t.Setenv("OTEL_TRACES_EXPORTER", "console")
+	got, err := NewSpanExporter(context.Background())
+	assert.NoError(t, err)
+	assert.IsType(t, &stdouttrace.Exporter{}, got)
+}
+
 func TestSpanExporterOTLP(t *testing.T) {
 	t.Setenv("OTEL_TRACES_EXPORTER", "otlp")