productcatalogservice

productcatalog service

The productcatalog service provides details about all products in the application.

Dynamic catalog reloading / artificial delay

This service has a "dynamic catalog reloading" feature that is purposefully not well implemented. The goal of this feature is to allow you to modify the products.json file and have the changes be picked up without having to restart the service.

However, this feature is bugged: the catalog is actually reloaded on each request, introducing a noticeable delay in the frontend. This delay will also show up in profiling tools: the parseCatalog function will take more than 80% of the CPU time.

You can trigger this feature (and the delay) by sending a USR1 signal and remove it (if needed) by sending a USR2 signal:

# Trigger bug
kubectl exec \
    $(kubectl get pods -l app=productcatalogservice -o jsonpath='{.items[0].metadata.name}') \
    -c server -- kill -USR1 1
# Remove bug
kubectl exec \
    $(kubectl get pods -l app=productcatalogservice -o jsonpath='{.items[0].metadata.name}') \
    -c server -- kill -USR2 1

OpenTelemetry instrumentation

Initialization

The OpenTelemetry SDK is initialized in main using the initOtelTracing function

func initOtelTracing(ctx context.Context, log logrus.FieldLogger) *sdktrace.TracerProvider {
	endpoint := os.Getenv("OTEL_EXPORTER_OTLP_ENDPOINT")
	if endpoint == "" {
		endpoint = "opentelemetry-collector:4317"
	}

	// Set GRPC options to establish an insecure connection to an OpenTelemetry Collector
	// To establish a TLS connection to a secured endpoint use:
	//   otlptracegrpc.WithTLSCredentials(credentials.NewClientTLSFromCert(nil, ""))
	opts := []otlptracegrpc.Option{
		otlptracegrpc.WithEndpoint(endpoint),
		otlptracegrpc.WithInsecure(),
	}

	// Create the exporter
	exporter, err := otlptrace.New(ctx, otlptracegrpc.NewClient(opts...))
	if err != nil {
		log.Fatal(err)
	}

	// Specify the TextMapPropagator to ensure spans propagate across service boundaries
	otel.SetTextMapPropagator(propagation.NewCompositeTextMapPropagator(propagation.Baggage{}, propagation.TraceContext{}))

	// Set standard attributes per semantic conventions
	res := resource.NewWithAttributes(
		semconv.SchemaURL,
		semconv.ServiceNameKey.String("productcatalog"),
	)

	// Create and set the TraceProvider
	tp := sdktrace.NewTracerProvider(
		sdktrace.WithBatcher(exporter),
		sdktrace.WithResource(res),
	)
	otel.SetTracerProvider(tp)

	return tp
}

You should call TraceProvider.shutdown() when your service is shutdown to ensure all spans are exported. This service makes that call as part of a deferred function in main

	// Initialize OpenTelemetry Tracing
	ctx := context.Background()
	tp := initOtelTracing(ctx, log)
	defer func() { _ = tp.Shutdown(ctx) }()

gRPC instrumentation

This service receives gRPC requests, which are instrumented in the run function as part of the gRPC server creation.

	// create gRPC server with OpenTelemetry instrumentation on all incoming requests
	srv := grpc.NewServer(
		grpc.UnaryInterceptor(otelgrpc.UnaryServerInterceptor(otelgrpc.WithTracerProvider(otel.GetTracerProvider()))),
		grpc.StreamInterceptor(otelgrpc.StreamServerInterceptor(otelgrpc.WithTracerProvider(otel.GetTracerProvider()))),
	)