feat: slog baggage option (#21)

Co-authored-by: Aleksandr Nekrasov <aleksandr.nekrasov@agoda.com>

Author: chameleon82

otelslog/CHANGELOG

@@ -8,6 +8,12 @@ This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
 
 ## [Unreleased]
 
+## [v0.1.2] 2024-09-30
+
+### Added
+
+- `AddBaggage` option to add baggage attributes as log attributes
+
 ## [v0.1.1] 2023-12-24
 
 ### Added

otelslog/otel_handler.go

@@ -20,6 +20,7 @@ import (
 	"context"
 	otel "github.com/agoda-com/opentelemetry-logs-go/logs"
 	"go.opentelemetry.io/otel/attribute"
+	"go.opentelemetry.io/otel/baggage"
 	"go.opentelemetry.io/otel/sdk/instrumentation"
 	semconv "go.opentelemetry.io/otel/semconv/v1.21.0"
 	"go.opentelemetry.io/otel/trace"
@@ -41,6 +42,7 @@ type OtelHandler struct {
 // A zero HandlerOptions consists entirely of default values.
 type HandlerOptions struct {
 	Level slog.Leveler
+	AddBaggage bool
 }
 
 type otelHandler struct {
@@ -88,10 +90,18 @@ func (o otelHandler) Handle(ctx context.Context, record slog.Record) error {
 
 	var attributes []attribute.KeyValue
 
+	if o.opts.AddBaggage {
+		b := baggage.FromContext(ctx)
+		// Iterate over baggage items and add them to log attributes
+		for _, i := range b.Members() {
+			attributes = append(attributes, attribute.String(i.Key(), i.Value()))
+		}
+	}
 	for _, attr := range o.attrs {
 		attributes = append(attributes, otelAttribute(attr)...)
 	}
 
+
 	record.Attrs(func(attr slog.Attr) bool {
 		attributes = append(attributes, otelAttribute(withGroupPrefix(o.groupPrefix, attr))...)
 		return true

otelslog/otel_handler_test.go

@@ -3,6 +3,7 @@ package otelslog
 import (
 	"bytes"
 	"context"
+	"go.opentelemetry.io/otel/baggage"
 	"log/slog"
 	"os"
 	"testing"
@@ -44,7 +45,8 @@ func TestNewOtelHandler(t *testing.T) {
 	)
 
 	handler := NewOtelHandler(loggerProvider, &HandlerOptions{
-		Level: slog.LevelInfo,
+		Level:      slog.LevelInfo,
+		AddBaggage: true,
 	}).
 		WithAttrs([]slog.Attr{slog.String("first", "value1")}).
 		WithGroup("group1").
@@ -54,12 +56,16 @@ func TestNewOtelHandler(t *testing.T) {
 	otelLogger := slog.New(handler)
 	slog.SetDefault(otelLogger)
 
+	member, _ := baggage.NewMember("baggage.key", "true")
+	bag, _ := baggage.New(member)
+	ctx = baggage.ContextWithBaggage(ctx, bag)
+
 	doSomething(ctx)
 
 	loggerProvider.Shutdown(ctx)
 
 	actual := buf.String()
 
 	assert.Contains(t, actual, "INFO hello slog [scopeInfo: github.com/agoda-com/otelslog:0.0.1] {host.name=")
-	assert.Contains(t, actual, "service.name=otelslog-example, service.version=1.0.0, first=value1, group1.second=value2, group1.group2.myKey=myValue, group1.group2.myGroup.groupKey=groupValue}")
+	assert.Contains(t, actual, "service.name=otelslog-example, service.version=1.0.0, baggage.key=true, first=value1, group1.second=value2, group1.group2.myKey=myValue, group1.group2.myGroup.groupKey=groupValue}")
 }