Added OpenTelemetry and use structured logging

internal/api/handler/default.go

@@ -1,7 +1,7 @@
 package handler
 
 import (
-	"log"
+	"log/slog"
 	"net/http"
 
 	"github.com/robindittmar/dttmr-api/internal/api/response"
@@ -18,15 +18,17 @@ type apiResponse struct {
 }
 
 func DefaultHandler(w http.ResponseWriter, r *http.Request) {
-	var resp apiResponse
+	ctx := r.Context()
 
-	resp.Method = r.Method
-	resp.Url = r.URL.String()
-	resp.Proto = r.Proto
-	resp.Header = make(map[string]string)
-	resp.Host = r.Host
-	resp.RemoteAddr = r.RemoteAddr
-	resp.Form = make(map[string]string)
+	resp := apiResponse{
+		Method:     r.Method,
+		Url:        r.URL.String(),
+		Proto:      r.Proto,
+		Header:     make(map[string]string),
+		Host:       r.Host,
+		RemoteAddr: r.RemoteAddr,
+		Form:       make(map[string]string),
+	}
 
 	for k, v := range r.Header {
 		resp.Header[k] = v[0]
@@ -37,8 +39,8 @@ func DefaultHandler(w http.ResponseWriter, r *http.Request) {
 			resp.Form[k] = v[0]
 		}
 	} else {
-		log.Println(err)
+		slog.ErrorContext(ctx, "Error parsing form", slog.Any("error", err))
 	}
 
-	response.JSON(w, http.StatusOK, resp)
+	response.JSON(ctx, w, http.StatusOK, resp)
 }

internal/api/handler/health.go

@@ -11,9 +11,10 @@ type healthResponse struct {
 }
 
 func HealthHandler(w http.ResponseWriter, r *http.Request) {
-	_ = r
+	ctx := r.Context()
+
 	resp := healthResponse{
 		Status: "ok",
 	}
-	response.JSON(w, http.StatusOK, resp)
+	response.JSON(ctx, w, http.StatusOK, resp)
 }

internal/api/middleware/telemetry.go

@@ -2,9 +2,10 @@ package middleware
 
 import (
 	"net/http"
+
+	"go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp"
 )
 
 func WithTelemetry(next http.Handler) http.Handler {
-	//return otelhttp.NewHandler(next, "dttmr-api")
-	return next
+	return otelhttp.NewHandler(next, "dttmr-api")
 }

internal/api/response/json.go

@@ -1,19 +1,20 @@
 package response
 
 import (
+	"context"
 	"encoding/json"
-	"log"
+	"log/slog"
 	"net/http"
 )
 
-func JSON(w http.ResponseWriter, status int, data any) {
+func JSON(ctx context.Context, w http.ResponseWriter, status int, data any) {
 	payload, err := json.Marshal(data)
 	if err != nil {
 		w.Header().Set("Content-Type", "application/json")
 		w.WriteHeader(http.StatusInternalServerError)
 		_, err := w.Write([]byte(`{"error": "internal server error: failed to marshal response"}`))
 		if err != nil {
-			log.Println(err)
+			slog.ErrorContext(ctx, "Failed to write JSON", slog.Any("error", err))
 			return
 		}
 		return
@@ -23,11 +24,11 @@ func JSON(w http.ResponseWriter, status int, data any) {
 	w.WriteHeader(status)
 	_, err = w.Write(payload)
 	if err != nil {
-		log.Println(err)
+		slog.ErrorContext(ctx, "Failed to write response", slog.Any("error", err))
 		return
 	}
 }
 
-func Error(w http.ResponseWriter, status int, message string) {
-	JSON(w, status, map[string]string{"error": message})
+func Error(ctx context.Context, w http.ResponseWriter, status int, message string) {
+	JSON(ctx, w, status, map[string]string{"error": message})
 }

internal/telemetry/logger.go

@@ -0,0 +1,32 @@
+package telemetry
+
+import (
+	"context"
+	"log/slog"
+
+	"go.opentelemetry.io/otel/trace"
+)
+
+type TraceHandler struct {
+	slog.Handler
+}
+
+func (h *TraceHandler) Handle(ctx context.Context, r slog.Record) error {
+	spanCtx := trace.SpanContextFromContext(ctx)
+	if spanCtx.HasTraceID() {
+		r.AddAttrs(
+			slog.String("trace_id", spanCtx.TraceID().String()),
+			slog.String("span_id", spanCtx.SpanID().String()),
+		)
+	}
+
+	return h.Handler.Handle(ctx, r)
+}
+
+func (h *TraceHandler) WithAttrs(attrs []slog.Attr) slog.Handler {
+	return &TraceHandler{Handler: h.Handler.WithAttrs(attrs)}
+}
+
+func (h *TraceHandler) WithGroup(name string) slog.Handler {
+	return &TraceHandler{Handler: h.Handler.WithGroup(name)}
+}

internal/telemetry/otel.go

@@ -0,0 +1,57 @@
+package telemetry
+
+import (
+	"context"
+	"errors"
+
+	"go.opentelemetry.io/otel"
+	"go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracegrpc"
+	"go.opentelemetry.io/otel/propagation"
+	"go.opentelemetry.io/otel/sdk/resource"
+	sdktrace "go.opentelemetry.io/otel/sdk/trace"
+	semconv "go.opentelemetry.io/otel/semconv/v1.24.0"
+)
+
+func Init(ctx context.Context, serviceName string, version string) (func(context.Context) error, error) {
+	var shutdownFns []func(context.Context) error
+
+	shutdown := func(ctx context.Context) error {
+		var err error
+		for _, fn := range shutdownFns {
+			err = errors.Join(err, fn(ctx))
+		}
+		shutdownFns = nil
+		return err
+	}
+
+	res, err := resource.New(ctx,
+		resource.WithAttributes(
+			semconv.ServiceName(serviceName),
+			semconv.ServiceVersion(version),
+		),
+	)
+	if err != nil {
+		return shutdown, err
+	}
+
+	otel.SetTextMapPropagator(
+		propagation.NewCompositeTextMapPropagator(
+			propagation.TraceContext{},
+			propagation.Baggage{},
+		),
+	)
+
+	traceExporter, err := otlptracegrpc.New(ctx)
+	if err != nil {
+		return shutdown, err
+	}
+
+	tracerProvider := sdktrace.NewTracerProvider(
+		sdktrace.WithBatcher(traceExporter),
+		sdktrace.WithResource(res),
+	)
+	otel.SetTracerProvider(tracerProvider)
+	shutdownFns = append(shutdownFns, tracerProvider.Shutdown)
+
+	return shutdown, nil
+}