ログの補足ガイドライン

import (
	"context"
	"strings"

	"go.opentelemetry.io/otel/log"
	sdklog "go.opentelemetry.io/otel/sdk/log"
)

// RedactTokensProcessor redacts values from attributes
// that contain "token" in the key.
type RedactTokensProcessor struct{}

// OnEmit redacts values from attributes containing "token" in the key
// by replacing them with "REDACTED".
func (p *RedactTokensProcessor) OnEmit(ctx context.Context, record *sdklog.Record) error {
	record.WalkAttributes(func(kv log.KeyValue) bool {
		if strings.Contains(strings.ToLower(kv.Key), "token") {
			record.AddAttributes(log.String(kv.Key, "REDACTED"))
		}
		return true
	})
	return nil
}

import (
	"context"

	"go.opentelemetry.io/otel/log"
	sdklog "go.opentelemetry.io/otel/sdk/log"
)

// SeverityProcessor filters out log records with severity below the given threshold.
type SeverityProcessor struct {
	sdklog.Processor
	Min log.Severity
}

// OnEmit passes ctx and record to the wrapped sdklog.Processor
// if the record's severity is greater than or equal to p.Min.
// Otherwise, the record is dropped (the wrapped processor is not invoked).
func (p *SeverityProcessor) OnEmit(ctx context.Context, record *sdklog.Record) error {
	if record.Severity() < p.Min {
		return nil
	}
	return p.Processor.OnEmit(ctx, record)
}

// Enabled returns false if the severity is lower than p.Min.
func (p *SeverityProcessor) Enabled(ctx context.Context, param sdklog.EnabledParameters) bool {
	if param.Severity < p.Min {
		return false
	}
	if fp, ok := p.Processor.(sdklog.FilterProcessor); ok {
		// The wrapped processor is also a filtering processor.
		return p.Processor.Enabled(ctx, param)
	}
	return true
}

import (
	"context"
	"errors"

	"go.opentelemetry.io/otel/sdk/log"
)

// IsolatedProcessor composes multiple processors so that they are isolated.
type IsolatedProcessor struct {
	Processors []log.Processor
}

// OnEmit passes ctx and a clone of record to the each wrapped sdklog.Processor.
func (p *IsolatedProcessor) OnEmit(ctx context.Context, record *log.Record) error {
	var rErr error
	r := record.Clone()
	for _, proc := range p.Processors {
		if err := proc.OnEmit(ctx, &r); err != nil {
			rErr = errors.Join(rErr, err)
		}
	}
	return rErr
}

// Enabled honors Enabled of the wrapped processors.
func (p *IsolatedProcessor) Enabled(ctx context.Context, param sdklog.EnabledParameters) bool  {
	fltrProcessors := make([]sdklog.FilterProcessor, len(p.Processors))
	for i, proc := range p.Processors {
		fp, ok := proc.(sdklog.FilterProcessor)
		if !ok {
			// Processor not implementing Enabled.
			// We assume it will be processed.
			return true
		}
		fltrProcessors[i] = fp
	}

	for _, proc := range fltrProcessors {
		if proc.Enabled(ctx, param) {
			// At least one Processor will process the Record.
			return true
		}
	}
	// No processor will process the record.
	return false
}

import (
	"context"

	"go.opentelemetry.io/otel/sdk/log"
)

// LogEventRouteProcessor routes log records and event records separately.
type LogEventRouteProcessor struct {
	LogProcessor log.Processor
	EventProcessor log.Processor
}

// OnEmit calls EventProcessor if the record has a non-empty event name.
// Otherwise, it calls LogProcessor.
func (p *LogEventRouteProcessor) OnEmit(ctx context.Context, record *log.Record) error {
	if record.EventName() != "" {
		return p.EventProcessor.OnEmit(ctx, record)
	}
	return p.LogProcessor.OnEmit(ctx, record)
}

// Enabled honors Enabled of the wrapped processors.
func (p *LogEventRouteProcessor) Enabled(ctx context.Context, param sdklog.EnabledParameters) bool  {
	fp1, ok := p.EventProcessor.(sdklog.FilterProcessor)
	if !ok {
		// Processor not implementing Enabled.
		return true
	}
	fp2, ok := p.LogProcessor.(sdklog.FilterProcessor)
	if !ok {
		// Processor not implementing Enabled.
		return true
	}

	if fp1.Enabled(ctx, param) {
		return true
	}
	if fp2.Enabled(ctx, param) {
		return true
	}
	// No processor will process the record.
	return false
}

import (
	"context"

	"go.opentelemetry.io/otel/exporters/otlp/otlplog/otlploghttp"
	"go.opentelemetry.io/otel/exporters/stdout/stdoutlog"
	"go.opentelemetry.io/otel/log"
	sdklog "go.opentelemetry.io/otel/sdk/log"
)


// NewLoggerProvider creates a new logger provider.
// - Event records with severity not lower than Info are exported via OTLP.
// - Event records have token attributes redacted.
// - Non-event log records with severity not lower than Debug are synchronously emitted to stdout.
func NewLoggerProvider() (*sdklog.LoggerProvider, error) {
	// Events processing setup.
	otlpExp, err := otlploghttp.New(context.Background())
	if err != nil {
		return nil, err
	}
	evtProc := &SeverityProcessor{
		// This processing is isolated so that there is no chance
		// that log records send to stdout have their token attributes redacted.
		Processor: &IsolatedProcessor{
			Processors: []sdklog.Processor{
				&RedactTokensProcessor{},
				sdklog.NewBatchProcessor(otlpExp),
			},
		},
		Min: log.SeverityInfo,
	}

	// Logs processing setup.
	stdoutExp, err := stdoutlog.New()
	if err != nil {
		return nil, err
	}
	logProc := &SeverityProcessor{
		Processor: sdklog.NewSimpleProcessor(stdoutExp),
		Min:       log.SeverityDebug,
	}

	// Create logs provider with log/event routing.
	provider := sdklog.NewLoggerProvider(
		sdklog.WithProcessor(&LogEventRouteProcessor{
			LogProcessor:   logProc,
			EventProcessor: evtProc,
		}),
	)
	return provider, nil
}