Add options, and tests

exporters/stdout/stdoutmetric/config.go

@@ -0,0 +1,78 @@
+// 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 stdoutmetric // import "go.opentelemetry.io/otel/exporters/stdout/stdoutmetric"
+
+import (
+	"io"
+	"os"
+)
+
+var (
+	defaultWriter      = os.Stdout
+	defaultPrettyPrint = false
+)
+
+// config contains options for the STDOUT exporter.
+type config struct {
+	// Writer is the destination.  If not set, os.Stdout is used.
+	Writer io.Writer
+
+	// PrettyPrint will encode the output into readable JSON. Default is
+	// false.
+	PrettyPrint bool
+}
+
+// newConfig creates a validated Config configured with options.
+func newConfig(options ...Option) (config, error) {
+	cfg := config{
+		Writer:      defaultWriter,
+		PrettyPrint: defaultPrettyPrint,
+	}
+	for _, opt := range options {
+		cfg = opt.apply(cfg)
+	}
+	return cfg, nil
+}
+
+// Option sets the value of an option for a Config.
+type Option interface {
+	apply(config) config
+}
+
+// WithWriter sets the export stream destination.
+func WithWriter(w io.Writer) Option {
+	return writerOption{w}
+}
+
+type writerOption struct {
+	W io.Writer
+}
+
+func (o writerOption) apply(cfg config) config {
+	cfg.Writer = o.W
+	return cfg
+}
+
+// WithPrettyPrint sets the export stream format to use JSON.
+func WithPrettyPrint() Option {
+	return prettyPrintOption(true)
+}
+
+type prettyPrintOption bool
+
+func (o prettyPrintOption) apply(cfg config) config {
+	cfg.PrettyPrint = bool(o)
+	return cfg
+}

exporters/stdout/stdoutmetric/example_test.go

@@ -0,0 +1,275 @@
+// 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.
+
+//go:build go1.18
+// +build go1.18
+
+package stdoutmetric
+
+import (
+	"bytes"
+	"context"
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+
+	"go.opentelemetry.io/otel/attribute"
+	"go.opentelemetry.io/otel/metric/unit"
+	"go.opentelemetry.io/otel/sdk/instrumentation"
+	"go.opentelemetry.io/otel/sdk/metric/metricdata"
+	"go.opentelemetry.io/otel/sdk/resource"
+)
+
+func TestExporterExport(t *testing.T) {
+	now := time.Unix(1558033527, 0)
+
+	exampleData := metricdata.ResourceMetrics{
+		Resource: resource.NewWithAttributes("example", attribute.String("resource-foo", "bar")),
+		ScopeMetrics: []metricdata.ScopeMetrics{
+			{
+				Scope: instrumentation.Scope{
+					Name:      "scope1",
+					Version:   "v1",
+					SchemaURL: "anotherExample",
+				},
+				Metrics: []metricdata.Metrics{
+					{
+						Name:        "gauge",
+						Description: "Gauge's description",
+						Unit:        unit.Dimensionless,
+						Data: metricdata.Gauge[int64]{
+							DataPoints: []metricdata.DataPoint[int64]{
+								{
+									Attributes: attribute.NewSet(),
+									StartTime:  now.Add(-1 * time.Minute),
+									Time:       now,
+									Value:      3,
+								},
+							},
+						},
+					},
+					{
+						Name:        "sum",
+						Description: "Sum's description",
+						Unit:        unit.Bytes,
+						Data: metricdata.Sum[float64]{
+							Temporality: metricdata.DeltaTemporality,
+							IsMonotonic: false,
+							DataPoints: []metricdata.DataPoint[float64]{
+								{
+									Attributes: attribute.NewSet(),
+									StartTime:  now.Add(-1 * time.Minute),
+									Time:       now,
+									Value:      3,
+								},
+								{
+									Attributes: attribute.NewSet(attribute.String("foo", "bar")),
+									StartTime:  now.Add(-1 * time.Minute),
+									Time:       now,
+									Value:      3,
+								},
+							},
+						},
+					},
+					{
+						Name:        "histogram",
+						Description: "Histogram's description",
+						Unit:        unit.Bytes,
+						Data: metricdata.Histogram{
+							Temporality: metricdata.CumulativeTemporality,
+							DataPoints: []metricdata.HistogramDataPoint{
+								{
+									Attributes: attribute.NewSet(),
+									StartTime:  now.Add(-1 * time.Minute),
+									Time:       now,
+									Count:      6,
+									Bounds: []float64{
+										1.0,
+										5.0,
+									},
+									BucketCounts: []uint64{
+										1, 2, 3,
+									},
+									Min: nil,
+									Max: nil,
+									Sum: 200,
+								},
+							},
+						},
+					},
+				},
+			},
+			{
+				Scope: instrumentation.Scope{
+					Name:      "Scope2",
+					Version:   "v2",
+					SchemaURL: "aDifferentExample",
+				},
+				Metrics: []metricdata.Metrics{
+					{
+						Name:        "gauge",
+						Description: "Gauge's description",
+						Unit:        unit.Dimensionless,
+						Data: metricdata.Gauge[int64]{
+							DataPoints: []metricdata.DataPoint[int64]{
+								{
+									Attributes: attribute.NewSet(),
+									StartTime:  now.Add(-1 * time.Minute),
+									Time:       now,
+									Value:      3,
+								},
+							},
+						},
+					},
+				},
+			},
+		},
+	}
+
+	buf := &bytes.Buffer{}
+	exp, err := New(
+		WithWriter(buf),
+		WithPrettyPrint(),
+	)
+	require.NoError(t, err)
+
+	err = exp.Export(context.Background(), exampleData)
+
+	require.NoError(t, err)
+	assert.Equal(t, expectedOutput, buf.String())
+}
+
+var expectedOutput = `{
+	"Resource": [
+		{
+			"Key": "resource-foo",
+			"Value": {
+				"Type": "STRING",
+				"Value": "bar"
+			}
+		}
+	],
+	"ScopeMetrics": [
+		{
+			"Scope": {
+				"Name": "scope1",
+				"Version": "v1",
+				"SchemaURL": "anotherExample"
+			},
+			"Metrics": [
+				{
+					"Name": "gauge",
+					"Description": "Gauge's description",
+					"Unit": "1",
+					"Data": {
+						"DataPoints": [
+							{
+								"Attributes": [],
+								"StartTime": "2019-05-16T19:04:27Z",
+								"Time": "2019-05-16T19:05:27Z",
+								"Value": 3
+							}
+						]
+					}
+				},
+				{
+					"Name": "sum",
+					"Description": "Sum's description",
+					"Unit": "By",
+					"Data": {
+						"DataPoints": [
+							{
+								"Attributes": [],
+								"StartTime": "2019-05-16T19:04:27Z",
+								"Time": "2019-05-16T19:05:27Z",
+								"Value": 3
+							},
+							{
+								"Attributes": [
+									{
+										"Key": "foo",
+										"Value": {
+											"Type": "STRING",
+											"Value": "bar"
+										}
+									}
+								],
+								"StartTime": "2019-05-16T19:04:27Z",
+								"Time": "2019-05-16T19:05:27Z",
+								"Value": 3
+							}
+						],
+						"Temporality": 2,
+						"IsMonotonic": false
+					}
+				},
+				{
+					"Name": "histogram",
+					"Description": "Histogram's description",
+					"Unit": "By",
+					"Data": {
+						"DataPoints": [
+							{
+								"Attributes": [],
+								"StartTime": "2019-05-16T19:04:27Z",
+								"Time": "2019-05-16T19:05:27Z",
+								"Count": 6,
+								"Bounds": [
+									1,
+									5
+								],
+								"BucketCounts": [
+									1,
+									2,
+									3
+								],
+								"Min": null,
+								"Max": null,
+								"Sum": 200
+							}
+						],
+						"Temporality": 1
+					}
+				}
+			]
+		},
+		{
+			"Scope": {
+				"Name": "Scope2",
+				"Version": "v2",
+				"SchemaURL": "aDifferentExample"
+			},
+			"Metrics": [
+				{
+					"Name": "gauge",
+					"Description": "Gauge's description",
+					"Unit": "1",
+					"Data": {
+						"DataPoints": [
+							{
+								"Attributes": [],
+								"StartTime": "2019-05-16T19:04:27Z",
+								"Time": "2019-05-16T19:05:27Z",
+								"Value": 3
+							}
+						]
+					}
+				}
+			]
+		}
+	]
+}
+`

exporters/stdout/stdoutmetric/exporter.go

@@ -20,22 +20,30 @@ package stdoutmetric // import "go.opentelemetry.io/otel/exporters/stdout/stdout
 import (
 	"context"
 	"encoding/json"
-	"os"
 	"sync"
 
 	"go.opentelemetry.io/otel/sdk/metric"
 	"go.opentelemetry.io/otel/sdk/metric/metricdata"
 )
 
-func New() (*Exporter, error) {
+// New creates an Exporter with the passed options.
+func New(options ...Option) (*Exporter, error) {
+	cfg, err := newConfig(options...)
+	if err != nil {
+		return nil, err
+	}
+
+	enc := json.NewEncoder(cfg.Writer)
+	if cfg.PrettyPrint {
+		enc.SetIndent("", "\t")
+	}
 
-	enc := json.NewEncoder(os.Stdout)
-	enc.SetIndent("", "\t")
 	return &Exporter{
 		encoder: enc,
 	}, nil
 }
 
+// Exporter is an implementation of metric.Exporter that writes ResourceMetrics to stdout.
 type Exporter struct {
 	encoder   *json.Encoder
 	encoderMu sync.Mutex