[hw-5] concurrency, graceful shutdown, concurrent tests

cart/internal/clients/products/client.go

@@ -10,23 +10,40 @@ import (
 
 	"route256/cart/internal/domain/entity"
 	"route256/cart/internal/domain/model"
+	"route256/cart/internal/infra/errgroup"
+
+	"github.com/rs/zerolog/log"
+	"golang.org/x/time/rate"
 )
 
 type ProductService struct {
 	httpClient http.Client
 	token      string
 	address    string
+
+	limiter *rate.Limiter
+
+	workers int
 }
 
-func NewProductService(httpClient http.Client, token string, address string) *ProductService {
+func NewProductService(httpClient http.Client, token, address string, limitRPS, burst, workers int) *ProductService {
+	log.Debug().Msgf("creating product server with %d worker limit", workers)
+
 	return &ProductService{
 		httpClient: httpClient,
 		token:      token,
 		address:    address,
+
+		limiter: rate.NewLimiter(rate.Limit(limitRPS), burst),
+		workers: workers,
 	}
 }
 
 func (s *ProductService) GetProductBySku(ctx context.Context, sku entity.Sku) (*model.Product, error) {
+	if err := s.limiter.Wait(ctx); err != nil {
+		return nil, fmt.Errorf("limiter.Wait: %w", err)
+	}
+
 	ctx, cancel := context.WithTimeout(ctx, 5*time.Second)
 	defer cancel()
 
@@ -73,3 +90,32 @@ type GetProductResponse struct {
 	Price int32  `json:"price"`
 	Sku   int64  `json:"sku"`
 }
+
+func (s *ProductService) GetProducts(ctx context.Context, skus []entity.Sku) ([]*model.Product, error) {
+	if len(skus) == 0 {
+		return []*model.Product{}, nil
+	}
+
+	results := make([]*model.Product, len(skus))
+
+	g, _ := errgroup.WithContext(ctx, s.workers)
+
+	for i, sku := range skus {
+		g.Go(func(groupCtx context.Context) error {
+			p, err := s.GetProductBySku(groupCtx, sku)
+			if err != nil {
+				return err
+			}
+
+			results[i] = p
+
+			return nil
+		})
+	}
+
+	if err := g.Wait(); err != nil {
+		return nil, err
+	}
+
+	return results, nil
+}