Add autoexport to automatically configure trace exporters

exporters/autoexport/exporter.go

@@ -0,0 +1,95 @@
+// 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 autoexport // import "go.opentelemetry.io/contrib/exporters/autoexport"
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"os"
+	"strings"
+
+	"go.opentelemetry.io/otel"
+	"go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracegrpc"
+	"go.opentelemetry.io/otel/sdk/trace"
+)
+
+const otelTracesExportersEnvKey = "OTEL_EXPORTERS"
+
+// errUnknownExpoter is returned when an unknown exporter name is used in
+// the OTEL_EXPORTERS environment variable.
+var errUnknownExpoter = errors.New("unknown exporter")
+
+func NewTraceExporters(exporters ...trace.SpanExporter) []trace.SpanExporter {
+	// prefer exporters configured via environment variables over exporters
+	// passed in via exporters paramter
+	envExporters, err := parseEnv()
+	if err != nil {
+		otel.Handle(err)
+	}
+	if len(envExporters) > 0 {
+		return envExporters
+	}
+
+	return exporters
+}
+
+// parseEnv returns an array of SpanExporter's defined by the OTEL_EXPORTERS
+// environment variable.
+// A nil slice is returned if no exporters are defined for the environment variable.
+func parseEnv() ([]trace.SpanExporter, error) {
+	expTypes, defined := os.LookupEnv(otelTracesExportersEnvKey)
+	if !defined {
+		return nil, nil
+	}
+
+	const sep = ","
+
+	var (
+		exporters []trace.SpanExporter
+		unknown   []string
+		errors    []error
+	)
+
+	for _, expType := range strings.Split(expTypes, sep) {
+		switch expType {
+		case "otlp":
+			// TODO: switch between otlp exporter protocol (grpc, http)
+			exp, err := otlptracegrpc.New(context.Background())
+			if err != nil {
+				errors = append(errors, err)
+			} else {
+				exporters = append(exporters, exp)
+			}
+			break
+		default:
+			exp, ok := envRegistry.load(expType)
+			if !ok {
+				unknown = append(unknown, expType)
+				continue
+			}
+			exporters = append(exporters, exp)
+		}
+	}
+
+	var err error
+	if len(unknown) > 0 {
+		joined := strings.Join(unknown, sep)
+		err = fmt.Errorf("%w: %s", errUnknownExpoter, joined)
+	}
+
+	// TODO: combine start errors with unknown exporter error
+	return exporters, err
+}

exporters/autoexport/exporter_test.go

@@ -0,0 +1,41 @@
+// 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 autoexport_test
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"go.opentelemetry.io/contrib/exporters/autoexport"
+	"go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracegrpc"
+)
+
+func TestNoExportersAreConfiguredIfEnvNotSetAndNoExportersProvided(t *testing.T) {
+	exporters := autoexport.NewTraceExporters()
+	assert.Equal(t, 0, len(exporters))
+}
+
+func TestProvidedExportersAreUsedWhenEnvVarIsNotSet(t *testing.T) {
+	exporters := autoexport.NewTraceExporters(
+		otlptracegrpc.NewUnstarted(),
+	)
+	assert.Equal(t, 1, len(exporters))
+}
+
+func TestExportersConfiguredInEnvVarAreReturned(t *testing.T) {
+	t.Setenv("OTEL_TRACES_EXPORTERS", "otlp")
+	exporters := autoexport.NewTraceExporters()
+	assert.Equal(t, 1, len(exporters))
+}

exporters/autoexport/go.mod

@@ -0,0 +1,31 @@
+module go.opentelemetry.io/contrib/exporters/autoexport
+
+go 1.17
+
+require (
+	github.com/stretchr/testify v1.7.1
+	go.opentelemetry.io/otel v1.10.0
+	go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracegrpc v1.10.0
+	go.opentelemetry.io/otel/sdk v1.10.0
+)
+
+require (
+	github.com/cenkalti/backoff/v4 v4.1.3 // indirect
+	github.com/davecgh/go-spew v1.1.0 // indirect
+	github.com/go-logr/logr v1.2.3 // indirect
+	github.com/go-logr/stdr v1.2.2 // indirect
+	github.com/golang/protobuf v1.5.2 // indirect
+	github.com/grpc-ecosystem/grpc-gateway/v2 v2.7.0 // indirect
+	github.com/pmezard/go-difflib v1.0.0 // indirect
+	go.opentelemetry.io/otel/exporters/otlp/internal/retry v1.10.0 // indirect
+	go.opentelemetry.io/otel/exporters/otlp/otlptrace v1.10.0 // indirect
+	go.opentelemetry.io/otel/trace v1.10.0 // indirect
+	go.opentelemetry.io/proto/otlp v0.19.0 // indirect
+	golang.org/x/net v0.0.0-20210405180319-a5a99cb37ef4 // indirect
+	golang.org/x/sys v0.0.0-20210510120138-977fb7262007 // indirect
+	golang.org/x/text v0.3.5 // indirect
+	google.golang.org/genproto v0.0.0-20211118181313-81c1377c94b1 // indirect
+	google.golang.org/grpc v1.46.2 // indirect
+	google.golang.org/protobuf v1.28.0 // indirect
+	gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c // indirect
+)