Updating dice example based on Updated Specification for the reference application

examples/dice/instrumented/main.go

@@ -40,8 +40,12 @@ func run() error {
 	}()
 
 	// Start HTTP server.
+	port := os.Getenv("APPLICATION_PORT")
+	if port == "" {
+		port = "8080"
+	}
 	srv := &http.Server{
-		Addr:         ":8080",
+		Addr:         ":" + port,
 		BaseContext:  func(net.Listener) context.Context { return ctx },
 		ReadTimeout:  time.Second,
 		WriteTimeout: 10 * time.Second,
@@ -72,8 +76,7 @@ func newHTTPHandler() http.Handler {
 	mux := http.NewServeMux()
 
 	// Register handlers.
-	mux.Handle("/rolldice", http.HandlerFunc(rolldice))
-	mux.Handle("/rolldice/{player}", http.HandlerFunc(rolldice))
+	mux.Handle("/rolldice", http.HandlerFunc(handleRolldice))
 
 	// Add HTTP instrumentation for the whole server.
 	handler := otelhttp.NewHandler(mux, "/")

examples/dice/instrumented/otel.go

@@ -16,6 +16,7 @@ import (
 	"go.opentelemetry.io/otel/propagation"
 	"go.opentelemetry.io/otel/sdk/log"
 	"go.opentelemetry.io/otel/sdk/metric"
+	"go.opentelemetry.io/otel/sdk/resource"
 	"go.opentelemetry.io/otel/sdk/trace"
 )
 
@@ -42,12 +43,19 @@ func setupOTelSDK(ctx context.Context) (func(context.Context) error, error) {
 		err = errors.Join(inErr, shutdown(ctx))
 	}
 
+	res, _ := resource.New(ctx,
+		resource.WithFromEnv(), // reads OTEL_SERVICE_NAME & OTEL_RESOURCE_ATTRIBUTES.
+		resource.WithProcess(),
+		resource.WithHost(),
+		resource.WithTelemetrySDK(),
+	)
+
 	// Set up propagator.
 	prop := newPropagator()
 	otel.SetTextMapPropagator(prop)
 
 	// Set up trace provider.
-	tracerProvider, err := newtracerProvider()
+	tracerProvider, err := newTracerProvider(res)
 	if err != nil {
 		handleErr(err)
 		return shutdown, err
@@ -56,7 +64,7 @@ func setupOTelSDK(ctx context.Context) (func(context.Context) error, error) {
 	otel.SetTracerProvider(tracerProvider)
 
 	// Set up meter provider.
-	meterProvider, err := newMeterProvider()
+	meterProvider, err := newMeterProvider(res)
 	if err != nil {
 		handleErr(err)
 		return shutdown, err
@@ -65,7 +73,7 @@ func setupOTelSDK(ctx context.Context) (func(context.Context) error, error) {
 	otel.SetMeterProvider(meterProvider)
 
 	// Set up logger provider.
-	loggerProvider, err := newLoggerProvider()
+	loggerProvider, err := newLoggerProvider(res)
 	if err != nil {
 		handleErr(err)
 		return shutdown, err
@@ -83,43 +91,41 @@ func newPropagator() propagation.TextMapPropagator {
 	)
 }
 
-func newtracerProvider() (*trace.TracerProvider, error) {
-	traceExporter, err := stdouttrace.New(
-		stdouttrace.WithPrettyPrint())
+func newTracerProvider(res *resource.Resource) (*trace.TracerProvider, error) {
+	traceExporter, err := stdouttrace.New(stdouttrace.WithPrettyPrint())
 	if err != nil {
 		return nil, err
 	}
 
 	tracerProvider := trace.NewTracerProvider(
-		trace.WithBatcher(traceExporter,
-			// Default is 5s. Set to 1s for demonstrative purposes.
-			trace.WithBatchTimeout(time.Second)),
+		trace.WithBatcher(traceExporter, trace.WithBatchTimeout(time.Second)), // Default is 5s. Set to 1s for demonstrative purposes.
+		trace.WithResource(res),
 	)
 	return tracerProvider, nil
 }
 
-func newMeterProvider() (*metric.MeterProvider, error) {
+func newMeterProvider(res *resource.Resource) (*metric.MeterProvider, error) {
 	metricExporter, err := stdoutmetric.New()
 	if err != nil {
 		return nil, err
 	}
 
 	meterProvider := metric.NewMeterProvider(
-		metric.WithReader(metric.NewPeriodicReader(metricExporter,
-			// Default is 1m. Set to 3s for demonstrative purposes.
-			metric.WithInterval(3*time.Second))),
+		metric.WithReader(metric.NewPeriodicReader(metricExporter, metric.WithInterval(3*time.Second))), // Default is 1m. Set to 3s for demonstrative purposes.
+		metric.WithResource(res),
 	)
 	return meterProvider, nil
 }
 
-func newLoggerProvider() (*log.LoggerProvider, error) {
+func newLoggerProvider(res *resource.Resource) (*log.LoggerProvider, error) {
 	logExporter, err := stdoutlog.New()
 	if err != nil {
 		return nil, err
 	}
 
 	loggerProvider := log.NewLoggerProvider(
 		log.WithProcessor(log.NewBatchProcessor(logExporter)),
+		log.WithResource(res),
 	)
 	return loggerProvider, nil
 }

examples/dice/instrumented/rolldice.go

@@ -4,10 +4,13 @@
 package main
 
 import (
-	"io"
-	"math/rand"
+	"context"
+	"encoding/json"
+	"errors"
+	"math/rand/v2"
 	"net/http"
 	"strconv"
+	"sync/atomic"
 
 	"go.opentelemetry.io/otel"
 	"go.opentelemetry.io/otel/attribute"
@@ -19,42 +22,149 @@ import (
 const name = "go.opentelemetry.io/contrib/examples/dice"
 
 var (
-	tracer  = otel.Tracer(name)
-	meter   = otel.Meter(name)
-	logger  = otelslog.NewLogger(name)
-	rollCnt metric.Int64Counter
+	tracer         = otel.Tracer(name)
+	meter          = otel.Meter(name)
+	logger         = otelslog.NewLogger(name)
+	rollCnt        metric.Int64Counter
+	outcomeHist    metric.Int64Histogram
+	lastRollsGauge metric.Int64ObservableGauge
+	lastRolls      atomic.Int64
 )
 
 func init() {
 	var err error
 	rollCnt, err = meter.Int64Counter("dice.rolls",
-		metric.WithDescription("The number of rolls by roll value"),
+		metric.WithDescription("The number of rolls"),
 		metric.WithUnit("{roll}"))
 	if err != nil {
 		panic(err)
 	}
+
+	outcomeHist, err = meter.Int64Histogram(
+		"dice.outcome",
+		metric.WithDescription("Distribution of dice outcomes (1-6)"),
+		metric.WithUnit("{count}"),
+	)
+	if err != nil {
+		panic(err)
+	}
+
+	lastRollsGauge, err = meter.Int64ObservableGauge(
+		"dice.last.rolls",
+		metric.WithDescription("The last rolls value observed"),
+	)
+	if err != nil {
+		panic(err)
+	}
+
+	// Register the gauge callback.
+	_, err = meter.RegisterCallback(
+		func(_ context.Context, o metric.Observer) error {
+			o.ObserveInt64(lastRollsGauge, lastRolls.Load())
+			return nil
+		},
+		lastRollsGauge,
+	)
+	if err != nil {
+		panic(err)
+	}
 }
 
-func rolldice(w http.ResponseWriter, r *http.Request) {
-	ctx, span := tracer.Start(r.Context(), "roll")
-	defer span.End()
+func handleRolldice(w http.ResponseWriter, r *http.Request) {
+	const maxRolls = 1000 // Arbitrary limit to prevent Slice memory allocation with excessive size value.
+
+	// Parse query parameters.
+	rollsParam := r.URL.Query().Get("rolls")
+	player := r.URL.Query().Get("player")
+
+	// Default rolls = 1 if not defined.
+	if rollsParam == "" {
+		rollsParam = "1"
+	}
+
+	// Check if rolls is a number.
+	rolls, err := strconv.Atoi(rollsParam)
+	if err != nil {
+		w.Header().Set("Content-Type", "application/json")
+		w.WriteHeader(http.StatusBadRequest)
+		msg := "Parameter rolls must be a positive integer"
+		_ = json.NewEncoder(w).Encode(map[string]string{
+			"status":  "error",
+			"message": msg,
+		})
+		logger.WarnContext(r.Context(), msg)
+		return
+	}
+
+	if rolls > maxRolls {
+		w.WriteHeader(http.StatusInternalServerError)
+		logger.ErrorContext(r.Context(), "rolls parameter exceeds maximum allowed value")
+		return
+	}
 
-	roll := 1 + rand.Intn(6) //nolint:gosec // G404: Use of weak random number generator (math/rand instead of crypto/rand) is ignored as this is not security-sensitive.
+	results, err := rollDice(r.Context(), rolls)
+	if err != nil {
+		// Signals invalid input (<=0).
+		w.WriteHeader(http.StatusInternalServerError)
+		logger.ErrorContext(r.Context(), err.Error())
+		return
+	}
+
+	if player == "" {
+		logger.DebugContext(r.Context(), "anonymous player rolled", "results", results)
+	} else {
+		logger.DebugContext(r.Context(), "player rolled dice", "player", player, "results", results)
+	}
+	logger.InfoContext(r.Context(), "Some player rolled a dice.")
 
-	var msg string
-	if player := r.PathValue("player"); player != "" {
-		msg = player + " is rolling the dice"
+	w.Header().Set("Content-Type", "application/json")
+	if len(results) == 1 {
+		writeJSON(r.Context(), w, results[0])
 	} else {
-		msg = "Anonymous player is rolling the dice"
+		writeJSON(r.Context(), w, results)
 	}
-	logger.InfoContext(ctx, msg, "result", roll)
+}
+
+func writeJSON(ctx context.Context, w http.ResponseWriter, v any) {
+	if err := json.NewEncoder(w).Encode(v); err != nil {
+		w.WriteHeader(http.StatusInternalServerError)
+		logger.ErrorContext(ctx, "json encode failed", "error", err)
+	}
+}
+
+// rollDice is the outer function which Does the error handling.
+func rollDice(ctx context.Context, rolls int) ([]int, error) {
+	ctx, span := tracer.Start(ctx, "rollDice")
+	defer span.End()
+
+	if rolls <= 0 {
+		err := errors.New("rolls must be positive")
+		span.RecordError(err)
+		return nil, err
+	}
+
+	results := make([]int, rolls)
+	for i := range rolls {
+		results[i] = rollOnce(ctx)
+		outcomeHist.Record(ctx, int64(results[i]))
+	}
+
+	rollsAttr := attribute.Int("rolls", rolls)
+	span.SetAttributes(rollsAttr)
+	rollCnt.Add(ctx, 1, metric.WithAttributes(rollsAttr))
+	lastRolls.Store(int64(rolls))
+	return results, nil
+}
+
+// rollOnce is the inner function — returns a random number 1–6.
+func rollOnce(ctx context.Context) int {
+	_, span := tracer.Start(ctx, "rollOnce")
+	defer span.End()
+
+	roll := 1 + rand.IntN(6) //nolint:gosec // G404: Use of weak random number generator (math/rand instead of crypto/rand) is ignored as this is not security-sensitive.
 
 	rollValueAttr := attribute.Int("roll.value", roll)
 	span.SetAttributes(rollValueAttr)
-	rollCnt.Add(ctx, 1, metric.WithAttributes(rollValueAttr))
 
-	resp := strconv.Itoa(roll) + "\n"
-	if _, err := io.WriteString(w, resp); err != nil {
-		logger.ErrorContext(ctx, "Write failed", "error", err)
-	}
+	return roll
 }

examples/dice/uninstrumented/main.go

@@ -27,8 +27,13 @@ func run() (err error) {
 	defer stop()
 
 	// Start HTTP server.
+	port := os.Getenv("APPLICATION_PORT")
+	if port == "" {
+		port = "8080"
+	}
+
 	srv := &http.Server{
-		Addr:         ":8080",
+		Addr:         ":" + port,
 		BaseContext:  func(net.Listener) context.Context { return ctx },
 		ReadTimeout:  time.Second,
 		WriteTimeout: 10 * time.Second,
@@ -60,8 +65,6 @@ func newHTTPHandler() http.Handler {
 	mux := http.NewServeMux()
 
 	// Register handlers.
-	mux.HandleFunc("/rolldice/", rolldice)
-	mux.HandleFunc("/rolldice/{player}", rolldice)
-
+	mux.HandleFunc("/rolldice", handleRolldice)
 	return mux
 }