productcatalog: introduce configurable latency (#134)

src/productcatalogservice/README.md

@@ -29,3 +29,10 @@ kubectl exec \
     $(kubectl get pods -l app=productcatalogservice -o jsonpath='{.items[0].metadata.name}') \
     -c server -- kill -USR2 1
 ```
+
+## Latency injection
+
+This service has an `EXTRA_LATENCY` environment variable. This will inject a sleep for the specified [time.Duration](https://golang.org/pkg/time/#ParseDuration) on every call to
+to the server.
+
+For example, use `EXTRA_LATENCY="5.5s"` to sleep for 5.5 seconds on every request.

src/productcatalogservice/server.go

@@ -48,6 +48,7 @@ var (
 	cat          pb.ListProductsResponse
 	catalogMutex *sync.Mutex
 	log          *logrus.Logger
+	extraLatency time.Duration
 
 	port = flag.Int("port", 3550, "port to listen at")
 
@@ -77,6 +78,18 @@ func main() {
 	go initProfiling("productcatalogservice", "1.0.0")
 	flag.Parse()
 
+	// set injected latency
+	if s := os.Getenv("EXTRA_LATENCY"); s != "" {
+		v, err := time.ParseDuration(s)
+		if err != nil {
+			log.Fatalf("failed to parse EXTRA_LATENCY (%s) as time.Duration: %+v", v, err)
+		}
+		extraLatency = v
+		log.Infof("extra latency enabled (duration: %v)", extraLatency)
+	} else {
+		extraLatency = time.Duration(0)
+	}
+
 	sigs := make(chan os.Signal, 1)
 	signal.Notify(sigs, syscall.SIGUSR1, syscall.SIGUSR2)
 	go func() {
@@ -117,7 +130,6 @@ func initJaegerTracing() {
 		log.Info("jaeger initialization disabled.")
 		return
 	}
-
 	// Register the Jaeger exporter to be able to retrieve
 	// the collected spans.
 	exporter, err := jaeger.NewExporter(jaeger.Options{
@@ -226,10 +238,12 @@ func (p *productCatalog) Check(ctx context.Context, req *healthpb.HealthCheckReq
 }
 
 func (p *productCatalog) ListProducts(context.Context, *pb.Empty) (*pb.ListProductsResponse, error) {
+	time.Sleep(extraLatency)
 	return &pb.ListProductsResponse{Products: parseCatalog()}, nil
 }
 
 func (p *productCatalog) GetProduct(ctx context.Context, req *pb.GetProductRequest) (*pb.Product, error) {
+	time.Sleep(extraLatency)
 	var found *pb.Product
 	for i := 0; i < len(parseCatalog()); i++ {
 		if req.Id == parseCatalog()[i].Id {
@@ -243,6 +257,7 @@ func (p *productCatalog) GetProduct(ctx context.Context, req *pb.GetProductReque
 }
 
 func (p *productCatalog) SearchProducts(ctx context.Context, req *pb.SearchProductsRequest) (*pb.SearchProductsResponse, error) {
+	time.Sleep(extraLatency)
 	// Intepret query as a substring match in name or description.
 	var ps []*pb.Product
 	for _, p := range parseCatalog() {