Added OpenTelemetry and use structured logging

Dockerfile

@@ -1,8 +1,7 @@
 FROM golang:1.26 AS build
 
 WORKDIR /app
-#COPY go.mod go.sum ./
+COPY go.mod go.sum ./
-COPY go.mod ./
 
 RUN go mod download
 

cmd/api-server/main.go

@@ -3,7 +3,7 @@ package main
 import (
 	"context"
 	"errors"
-	"log"
+	"log/slog"
 	"net/http"
 	"os"
 	"os/signal"
@@ -11,9 +11,44 @@ import (
 	"time"
 
 	"github.com/robindittmar/dttmr-api/internal/api/router"
+	"github.com/robindittmar/dttmr-api/internal/telemetry"
 )
 
 func main() {
+	serviceName := "dttmr-api"
+	serviceVersion := "0.1.0"
+
+	if err := run(serviceName, serviceVersion); err != nil {
+		slog.Error("Service crashed", slog.Any("error", err))
+		os.Exit(1)
+	}
+}
+
+func run(serviceName string, serviceVersion string) error {
+	baseHandler := slog.NewJSONHandler(os.Stdout, &slog.HandlerOptions{
+		Level: slog.LevelInfo,
+	})
+	traceHandler := &telemetry.TraceHandler{Handler: baseHandler}
+
+	logger := slog.New(traceHandler)
+	slog.SetDefault(logger)
+
+	slog.Info("Starting service", slog.String("service", serviceName), slog.String("version", serviceVersion))
+
+	shutdownTelemetry, err := telemetry.Init(context.Background(), serviceName, serviceVersion)
+	if err != nil {
+		slog.Error("Failed to initialize telemetry", err)
+		return err
+	}
+	defer func() {
+		shutdownCtx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
+		defer cancel()
+
+		if err := shutdownTelemetry(shutdownCtx); err != nil {
+			slog.Error("Failed to shutdown telemetry", err)
+		}
+	}()
+
 	cfg := router.Config{}
 	mux := router.NewMux(cfg)
 
@@ -26,22 +61,26 @@ func main() {
 	}
 
 	go func() {
-		log.Printf("Listening on %s\n", srv.Addr)
+		slog.Info("Starting http server", "addr", srv.Addr)
 		if err := srv.ListenAndServe(); err != nil && !errors.Is(err, http.ErrServerClosed) {
-			log.Fatalf("Failed to start server: %v", err)
+			slog.Error("Failed to start http server", err)
+			os.Exit(1)
 		}
 	}()
 
 	quit := make(chan os.Signal, 1)
 	signal.Notify(quit, syscall.SIGINT, syscall.SIGTERM)
-	<-quit
+	sig := <-quit
-	log.Println("Shutting down server...")
+	slog.Info("Shutting down server...", slog.String("signal", sig.String()))
 
 	ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
 	defer cancel()
 
 	if err := srv.Shutdown(ctx); err != nil {
-		log.Fatalf("Server forced to shutdown: %v", err)
+		slog.Error("Server forced to shutdown", slog.Any("error", err))
+		return err
 	}
-	log.Println("Server shutdown successful!")
+
+	slog.Info("Service shutdown successful!")
+	return nil
 }

go.mod

@@ -1,3 +1,32 @@
 module github.com/robindittmar/dttmr-api
 
 go 1.26
+
+require (
+	go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp v0.69.0
+	go.opentelemetry.io/otel v1.44.0
+	go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracegrpc v1.44.0
+	go.opentelemetry.io/otel/sdk v1.44.0
+)
+
+require (
+	github.com/cenkalti/backoff/v5 v5.0.3 // indirect
+	github.com/cespare/xxhash/v2 v2.3.0 // indirect
+	github.com/felixge/httpsnoop v1.0.4 // indirect
+	github.com/go-logr/logr v1.4.3 // indirect
+	github.com/go-logr/stdr v1.2.2 // indirect
+	github.com/google/uuid v1.6.0 // indirect
+	github.com/grpc-ecosystem/grpc-gateway/v2 v2.29.0 // indirect
+	go.opentelemetry.io/auto/sdk v1.2.1 // indirect
+	go.opentelemetry.io/otel/exporters/otlp/otlptrace v1.44.0 // indirect
+	go.opentelemetry.io/otel/metric v1.44.0 // indirect
+	go.opentelemetry.io/otel/trace v1.44.0 // indirect
+	go.opentelemetry.io/proto/otlp v1.10.0 // indirect
+	golang.org/x/net v0.55.0 // indirect
+	golang.org/x/sys v0.45.0 // indirect
+	golang.org/x/text v0.37.0 // indirect
+	google.golang.org/genproto/googleapis/api v0.0.0-20260526163538-3dc84a4a5aaa // indirect
+	google.golang.org/genproto/googleapis/rpc v0.0.0-20260526163538-3dc84a4a5aaa // indirect
+	google.golang.org/grpc v1.81.1 // indirect
+	google.golang.org/protobuf v1.36.11 // indirect
+)

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 := apiResponse{
-	resp.Url = r.URL.String()
+		Method:     r.Method,
-	resp.Proto = r.Proto
+		Url:        r.URL.String(),
-	resp.Header = make(map[string]string)
+		Proto:      r.Proto,
-	resp.Host = r.Host
+		Header:     make(map[string]string),
-	resp.RemoteAddr = r.RemoteAddr
+		Host:       r.Host,
-	resp.Form = make(map[string]string)
+		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 otelhttp.NewHandler(next, "dttmr-api")
-	return next
 }

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) {
+func Error(ctx context.Context, w http.ResponseWriter, status int, message string) {
-	JSON(w, status, map[string]string{"error": message})
+	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
+}