Trace back everything (tested)

Signed-off-by: Asai Neko <sugar@sne.moe>

logger/slog.go

@@ -7,15 +7,57 @@ import (
 	"os"
 	"strings"
 
+	"github.com/spf13/viper"
+	"go.opentelemetry.io/contrib/bridges/otelslog"
 	"go.opentelemetry.io/otel/trace"
 )
 
-type otlpHandler struct {
-	slog.Handler
+type multiHandler struct {
+	handlers []slog.Handler
+}
+
+func (m *multiHandler) Enabled(ctx context.Context, l slog.Level) bool {
+	for _, h := range m.handlers {
+		if h.Enabled(ctx, l) {
+			return true
+		}
+	}
+	return false
+}
+
+func (m *multiHandler) Handle(ctx context.Context, r slog.Record) error {
+	span := trace.SpanFromContext(ctx)
+	if span.SpanContext().HasTraceID() {
+		r.AddAttrs(
+			slog.String("trace_id", span.SpanContext().TraceID().String()),
+			slog.String("span_id", span.SpanContext().SpanID().String()),
+		)
+	}
+
+	for _, h := range m.handlers {
+		_ = h.Handle(ctx, r)
+	}
+	return nil
+}
+
+func (m *multiHandler) WithAttrs(attrs []slog.Attr) slog.Handler {
+	newHandlers := make([]slog.Handler, len(m.handlers))
+	for i, h := range m.handlers {
+		newHandlers[i] = h.WithAttrs(attrs)
+	}
+	return &multiHandler{handlers: newHandlers}
+}
+
+func (m *multiHandler) WithGroup(name string) slog.Handler {
+	newHandlers := make([]slog.Handler, len(m.handlers))
+	for i, h := range m.handlers {
+		newHandlers[i] = h.WithGroup(name)
+	}
+	return &multiHandler{handlers: newHandlers}
 }
 
 func Init() {
-	levelStr := strings.ToLower(os.Getenv("LOG_LEVEL"))
+	levelStr := strings.ToLower(viper.GetString("server.log_level"))
 	var level slog.Level
 	switch levelStr {
 	case "debug":
@@ -34,7 +76,7 @@ func Init() {
 		writer = io.MultiWriter(os.Stdout, file)
 	}
 
-	opts := &slog.HandlerOptions{
+	localHandler := slog.NewJSONHandler(writer, &slog.HandlerOptions{
 		Level:     level,
 		AddSource: true,
 		ReplaceAttr: func(groups []string, a slog.Attr) slog.Attr {
@@ -43,21 +85,13 @@ func Init() {
 			}
 			return a
 		},
+	})
+
+	otelHandler := otelslog.NewHandler(viper.GetString("server.service_name"))
+
+	combinedHandler := &multiHandler{
+		handlers: []slog.Handler{localHandler, otelHandler},
 	}
 
-	baseHandler := slog.NewJSONHandler(writer, opts)
-	handler := &otlpHandler{baseHandler}
-	logger := slog.New(handler)
-	slog.SetDefault(logger)
-}
-
-func (h *otlpHandler) Handle(ctx context.Context, r slog.Record) error {
-	span := trace.SpanFromContext(ctx)
-	if span.SpanContext().HasTraceID() {
-		r.AddAttrs(
-			slog.String("trace_id", span.SpanContext().TraceID().String()),
-			slog.String("span_id", span.SpanContext().SpanID().String()),
-		)
-	}
-	return h.Handler.Handle(ctx, r)
+	slog.SetDefault(slog.New(combinedHandler))
 }