Add OpenTelemetry instrumentation with middleware-only approach

pkg/telemetry/telemetry.go

@@ -0,0 +1,100 @@
+// Package telemetry provides OpenTelemetry instrumentation for the DanceLessonsCoach application
+package telemetry
+
+import (
+	"context"
+	"log"
+
+	"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/v1.21.0"
+	"go.opentelemetry.io/otel/trace"
+)
+
+// Setup initializes OpenTelemetry tracing with the given configuration
+type Setup struct {
+	ServiceName  string
+	OTLPEndpoint string
+	Insecure     bool
+	SamplerType  string
+	SamplerRatio float64
+}
+
+// InitializeTracing sets up OpenTelemetry tracing provider
+func (s *Setup) InitializeTracing(ctx context.Context) (*sdktrace.TracerProvider, error) {
+	// Create OTLP gRPC exporter
+	exporter, err := otlptracegrpc.New(ctx,
+		otlptracegrpc.WithEndpoint(s.OTLPEndpoint),
+		otlptracegrpc.WithInsecure(),
+	)
+	if err != nil {
+		return nil, err
+	}
+
+	// Create resource with service name
+	res, err := resource.New(ctx,
+		resource.WithAttributes(
+			semconv.ServiceName(s.ServiceName),
+		),
+	)
+	if err != nil {
+		return nil, err
+	}
+
+	// Create sampler based on configuration
+	sampler := s.getSampler()
+
+	// Create trace provider
+	tp := sdktrace.NewTracerProvider(
+		sdktrace.WithBatcher(exporter),
+		sdktrace.WithResource(res),
+		sdktrace.WithSampler(sampler),
+	)
+
+	// Set global tracer provider and propagator
+	otel.SetTracerProvider(tp)
+	otel.SetTextMapPropagator(propagation.NewCompositeTextMapPropagator(
+		propagation.TraceContext{},
+		propagation.Baggage{},
+	))
+
+	return tp, nil
+}
+
+// Shutdown performs cleanup of the tracer provider
+func Shutdown(ctx context.Context, tp *sdktrace.TracerProvider) error {
+	if tp == nil {
+		return nil
+	}
+	return tp.Shutdown(ctx)
+}
+
+// getSampler returns the appropriate sampler based on configuration
+func (s *Setup) getSampler() sdktrace.Sampler {
+	switch s.SamplerType {
+	case "always_on":
+		return sdktrace.AlwaysSample()
+	case "always_off":
+		return sdktrace.NeverSample()
+	case "traceidratio":
+		return sdktrace.TraceIDRatioBased(s.SamplerRatio)
+	case "parentbased_always_on":
+		return sdktrace.ParentBased(sdktrace.AlwaysSample())
+	case "parentbased_always_off":
+		return sdktrace.ParentBased(sdktrace.NeverSample())
+	case "parentbased_traceidratio":
+		return sdktrace.ParentBased(sdktrace.TraceIDRatioBased(s.SamplerRatio))
+	default:
+		log.Printf("Unknown sampler type: %s, defaulting to always_on", s.SamplerType)
+		return sdktrace.AlwaysSample()
+	}
+}
+
+// GetTracer returns a named tracer from the global provider
+// Returns a no-op tracer if OpenTelemetry is not initialized
+func GetTracer(name string) trace.Tracer {
+	return otel.Tracer(name)
+}