opentelemetry-go/exporters/stdout/stdouttrace/trace.go

// Copyright The OpenTelemetry Authors
// SPDX-License-Identifier: Apache-2.0

package stdouttrace // import "go.opentelemetry.io/otel/exporters/stdout/stdouttrace"

import (
	"context"
	"encoding/json"
	"errors"
	"fmt"
	"sync"
	"time"

	"go.opentelemetry.io/otel/exporters/stdout/stdouttrace/internal/counter"
	"go.opentelemetry.io/otel/exporters/stdout/stdouttrace/internal/observ"
	"go.opentelemetry.io/otel/sdk/trace"
	"go.opentelemetry.io/otel/sdk/trace/tracetest"
)

var zeroTime time.Time

var _ trace.SpanExporter = &Exporter{}

// New creates an Exporter with the passed options.
func New(options ...Option) (*Exporter, error) {
	cfg := newConfig(options...)

	enc := json.NewEncoder(cfg.Writer)
	if cfg.PrettyPrint {
		enc.SetIndent("", "\t")
	}

	exporter := &Exporter{
		encoder:    enc,
		timestamps: cfg.Timestamps,
	}

	var err error
	exporter.inst, err = observ.NewInstrumentation(counter.NextExporterID())
	return exporter, err
}

// Exporter is an implementation of trace.SpanSyncer that writes spans to stdout.
type Exporter struct {
	encoder    *json.Encoder
	encoderMu  sync.Mutex
	timestamps bool

	stoppedMu sync.RWMutex
	stopped   bool

	inst *observ.Instrumentation
}

// ExportSpans writes spans in json format to stdout.
func (e *Exporter) ExportSpans(ctx context.Context, spans []trace.ReadOnlySpan) (err error) {
	var success int64
	if e.inst != nil {
		end := e.inst.ExportSpans(ctx, len(spans))
		defer func() { end(success, err) }()
	}

	if err := ctx.Err(); err != nil {
		return err
	}
	e.stoppedMu.RLock()
	stopped := e.stopped
	e.stoppedMu.RUnlock()
	if stopped {
		return nil
	}

	if len(spans) == 0 {
		return nil
	}

	stubs := tracetest.SpanStubsFromReadOnlySpans(spans)

	e.encoderMu.Lock()
	defer e.encoderMu.Unlock()
	for i := range stubs {
		stub := &stubs[i]
		// Remove timestamps
		if !e.timestamps {
			stub.StartTime = zeroTime
			stub.EndTime = zeroTime
			for j := range stub.Events {
				ev := &stub.Events[j]
				ev.Time = zeroTime
			}
		}

		// Encode span stubs, one by one
		if e := e.encoder.Encode(stub); e != nil {
			err = errors.Join(err, fmt.Errorf("failed to encode span %d: %w", i, e))
			continue
		}
		success++
	}
	return err
}

// Shutdown is called to stop the exporter, it performs no action.
func (e *Exporter) Shutdown(context.Context) error {
	e.stoppedMu.Lock()
	e.stopped = true
	e.stoppedMu.Unlock()

	return nil
}

// MarshalLog is the marshaling function used by the logging system to represent this Exporter.
func (e *Exporter) MarshalLog() any {
	return struct {
		Type           string
		WithTimestamps bool
	}{
		Type:           "stdout",
		WithTimestamps: e.timestamps,
	}
}