feat(autometer): add WithLookupExporter option

autometer/autometer.go

@@ -60,11 +60,6 @@ func getEnvOr(name, def string) string {
 
 func noopHandler(_ context.Context) error { return nil }
 
-type stoppableReader interface {
-	sdkmetric.Reader
-	Shutdown(ctx context.Context) error
-}
-
 // ShutdownFunc is a function that shuts down the MeterProvider.
 type ShutdownFunc func(ctx context.Context) error
 
@@ -81,13 +76,14 @@ func NewMeterProvider(ctx context.Context, options ...Option) (
 		metricOptions = append(metricOptions, sdkmetric.WithResource(cfg.res))
 	}
 
-	ret := func(r stoppableReader) (metric.MeterProvider, func(ctx context.Context) error, error) {
+	ret := func(r sdkmetric.Reader) (metric.MeterProvider, func(ctx context.Context) error, error) {
 		metricOptions = append(metricOptions, sdkmetric.WithReader(r))
 		return sdkmetric.NewMeterProvider(metricOptions...), r.Shutdown, nil
 	}
 
 	// Metrics exporter.
-	switch exporter := strings.TrimSpace(getEnvOr("OTEL_METRICS_EXPORTER", expOTLP)); exporter {
+	exporter := strings.TrimSpace(getEnvOr("OTEL_METRICS_EXPORTER", expOTLP))
+	switch exporter {
 	case expPrometheus:
 		lg.Debug("Using Prometheus metrics exporter")
 		reg := cfg.prom
@@ -154,6 +150,21 @@ func NewMeterProvider(ctx context.Context, options ...Option) (
 		lg.Debug("Using no-op metrics exporter")
 		return noop.NewMeterProvider(), noopHandler, nil
 	default:
-		return nil, nil, errors.Errorf("unsupported OTEL_METRICS_EXPORTER %q", exporter)
+		lookup := cfg.lookup
+		if lookup == nil {
+			break
+		}
+		lg.Debug("Looking for metrics exporter", zap.String("exporter", exporter))
+		exp, ok, err := lookup(ctx, exporter)
+		if err != nil {
+			return nil, nil, errors.Wrap(err, exporter)
+		}
+		if !ok {
+			break
+		}
+
+		lg.Debug("Using user-defined metrics exporter", zap.String("exporter", exporter))
+		return ret(exp)
 	}
+	return nil, nil, errors.Errorf("unsupported OTEL_METRICS_EXPORTER %q", exporter)
 }

autometer/config.go

@@ -1,16 +1,19 @@
 package autometer
 
 import (
+	"context"
 	"io"
 
 	"github.com/prometheus/client_golang/prometheus"
+	sdkmetric "go.opentelemetry.io/otel/sdk/metric"
 	"go.opentelemetry.io/otel/sdk/resource"
 )
 
 // config contains configuration options for a MeterProvider.
 type config struct {
 	res    *resource.Resource
 	writer io.Writer
+	lookup LookupExporter
 
 	prom         prometheus.Registerer
 	promCallback func(reg *prometheus.Registry)
@@ -72,3 +75,14 @@ func WithWriter(out io.Writer) Option {
 		return conf
 	})
 }
+
+// LookupExporter creates exporter by name.
+type LookupExporter func(ctx context.Context, name string) (sdkmetric.Reader, bool, error)
+
+// WithLookupExporter sets exporter lookup function.
+func WithLookupExporter(lookup LookupExporter) Option {
+	return optionFunc(func(conf config) config {
+		conf.lookup = lookup
+		return conf
+	})
+}

autometer/config_test.go

@@ -0,0 +1,47 @@
+package autometer
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+	sdkmetric "go.opentelemetry.io/otel/sdk/metric"
+)
+
+func TestWithLookupExporter(t *testing.T) {
+	var lookup LookupExporter = func(ctx context.Context, name string) (sdkmetric.Reader, bool, error) {
+		switch name {
+		case "return_something":
+			r := sdkmetric.NewManualReader()
+			return r, true, nil
+		case "return_error":
+			return nil, false, errors.New("test error")
+		default:
+			return nil, false, nil
+		}
+	}
+
+	for i, tt := range []struct {
+		name        string
+		containsErr string
+	}{
+		{"return_something", ``},
+		{"return_error", `test error`},
+		{"return_not_exist", `unsupported OTEL_METRICS_EXPORTER "return_not_exist"`},
+	} {
+		tt := tt
+		t.Run(fmt.Sprintf("Test%d", i+1), func(t *testing.T) {
+			t.Setenv("OTEL_METRICS_EXPORTER", tt.name)
+			ctx := context.Background()
+
+			_, _, err := NewMeterProvider(ctx, WithLookupExporter(lookup))
+			if tt.containsErr != "" {
+				require.ErrorContains(t, err, tt.containsErr)
+				return
+			}
+			require.NoError(t, err)
+		})
+	}
+}

autotracer/autotracer.go

@@ -71,7 +71,9 @@ func NewTracerProvider(ctx context.Context, options ...Option) (
 		traceOptions = append(traceOptions, sdktrace.WithBatcher(e))
 		return sdktrace.NewTracerProvider(traceOptions...), e.Shutdown, nil
 	}
-	switch exporter := strings.TrimSpace(getEnvOr("OTEL_TRACES_EXPORTER", expOTLP)); exporter {
+
+	exporter := strings.TrimSpace(getEnvOr("OTEL_TRACES_EXPORTER", expOTLP))
+	switch exporter {
 	case expOTLP:
 		proto := os.Getenv("OTEL_EXPORTER_OTLP_PROTOCOL")
 		if proto == "" {
@@ -112,6 +114,21 @@ func NewTracerProvider(ctx context.Context, options ...Option) (
 		lg.Debug("Using no-op trace exporter")
 		return noop.NewTracerProvider(), nop, nil
 	default:
-		return nil, nil, errors.Errorf("unsupported OTEL_TRACES_EXPORTER %q", exporter)
+		lookup := cfg.lookup
+		if lookup == nil {
+			break
+		}
+		lg.Debug("Looking for traces exporter", zap.String("exporter", exporter))
+		exp, ok, err := lookup(ctx, exporter)
+		if err != nil {
+			return nil, nil, errors.Wrap(err, exporter)
+		}
+		if !ok {
+			break
+		}
+
+		lg.Debug("Using user-defined traces exporter", zap.String("exporter", exporter))
+		return ret(exp)
 	}
+	return nil, nil, errors.Errorf("unsupported OTEL_TRACES_EXPORTER %q", exporter)
 }

autotracer/config.go

@@ -1,15 +1,18 @@
 package autotracer
 
 import (
+	"context"
 	"io"
 
 	"go.opentelemetry.io/otel/sdk/resource"
+	sdktrace "go.opentelemetry.io/otel/sdk/trace"
 )
 
 // config contains configuration options for a MeterProvider.
 type config struct {
 	res    *resource.Resource
 	writer io.Writer
+	lookup LookupExporter
 }
 
 // newConfig returns a config configured with options.
@@ -54,3 +57,14 @@ func WithWriter(out io.Writer) Option {
 		return conf
 	})
 }
+
+// LookupExporter creates exporter by name.
+type LookupExporter func(ctx context.Context, name string) (sdktrace.SpanExporter, bool, error)
+
+// WithLookupExporter sets exporter lookup function.
+func WithLookupExporter(lookup LookupExporter) Option {
+	return optionFunc(func(conf config) config {
+		conf.lookup = lookup
+		return conf
+	})
+}

autotracer/config_test.go

@@ -0,0 +1,49 @@
+package autotracer
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"io"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+	"go.opentelemetry.io/otel/exporters/stdout/stdouttrace"
+	"go.opentelemetry.io/otel/sdk/trace"
+)
+
+func TestWithLookupExporter(t *testing.T) {
+	var lookup LookupExporter = func(ctx context.Context, name string) (trace.SpanExporter, bool, error) {
+		switch name {
+		case "return_something":
+			e, err := stdouttrace.New(stdouttrace.WithWriter(io.Discard))
+			return e, true, err
+		case "return_error":
+			return nil, false, errors.New("test error")
+		default:
+			return nil, false, nil
+		}
+	}
+
+	for i, tt := range []struct {
+		name        string
+		containsErr string
+	}{
+		{"return_something", ``},
+		{"return_error", `test error`},
+		{"return_not_exist", `unsupported OTEL_TRACES_EXPORTER "return_not_exist"`},
+	} {
+		tt := tt
+		t.Run(fmt.Sprintf("Test%d", i+1), func(t *testing.T) {
+			t.Setenv("OTEL_TRACES_EXPORTER", tt.name)
+			ctx := context.Background()
+
+			_, _, err := NewTracerProvider(ctx, WithLookupExporter(lookup))
+			if tt.containsErr != "" {
+				require.ErrorContains(t, err, tt.containsErr)
+				return
+			}
+			require.NoError(t, err)
+		})
+	}
+}