stdoutlog: Add exporter (#5172)

exporters/stdout/stdoutlog/config.go

@@ -9,9 +9,9 @@ import (
 )
 
 var (
-	defaultWriter      = os.Stdout
-	defaultPrettyPrint = false
-	defaultTimestamps  = true
+	defaultWriter      io.Writer = os.Stdout
+	defaultPrettyPrint           = false
+	defaultTimestamps            = true
 )
 
 // config contains options for the STDOUT exporter.

exporters/stdout/stdoutlog/exporter.go

@@ -0,0 +1,72 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+package stdoutlog // import "go.opentelemetry.io/otel/exporters/stdout/stdoutlog"
+
+import (
+	"context"
+	"encoding/json"
+	"sync/atomic"
+
+	"go.opentelemetry.io/otel/sdk/log"
+)
+
+var _ log.Exporter = &Exporter{}
+
+// Exporter writes JSON-encoded log records to an [io.Writer] ([os.Stdout] by default).
+// Exporter must be created with [New].
+type Exporter struct {
+	encoder    atomic.Pointer[json.Encoder]
+	timestamps bool
+}
+
+// New creates an [Exporter].
+func New(options ...Option) (*Exporter, error) {
+	cfg := newConfig(options)
+
+	enc := json.NewEncoder(cfg.Writer)
+	if cfg.PrettyPrint {
+		enc.SetIndent("", "\t")
+	}
+
+	e := Exporter{
+		timestamps: cfg.Timestamps,
+	}
+	e.encoder.Store(enc)
+
+	return &e, nil
+}
+
+// Export exports log records to writer.
+func (e *Exporter) Export(ctx context.Context, records []log.Record) error {
+	enc := e.encoder.Load()
+	if enc == nil {
+		return nil
+	}
+
+	for _, record := range records {
+		// Honor context cancellation.
+		if err := ctx.Err(); err != nil {
+			return err
+		}
+
+		// Encode record, one by one.
+		recordJSON := e.newRecordJSON(record)
+		if err := enc.Encode(recordJSON); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+// Shutdown shuts down the Exporter.
+// Calls to Export will perform no operation after this is called.
+func (e *Exporter) Shutdown(context.Context) error {
+	e.encoder.Store(nil)
+	return nil
+}
+
+// ForceFlush performs no action.
+func (e *Exporter) ForceFlush(context.Context) error {
+	return nil
+}