feature(voucher):single-instance service with mutex for thread safety

biz/dal/mysql/voucher.go

@@ -3,6 +3,7 @@ package mysql
 import (
 	"context"
 	"errors"
+	"fmt"
 	"gorm.io/gorm"
 	"xzdp/biz/model/voucher"
 )
@@ -25,16 +26,28 @@ func QueryVoucherByID(ctx context.Context, id int64) (*voucher.SeckillVoucher, e
 	return &seckillVoucher, err
 }
 
-func QueryVoucherOrderByVoucherID(ctx context.Context, userId int64, id int64) (*voucher.VoucherOrder, error) {
+func QueryVoucherOrderByVoucherID(ctx context.Context, userId int64, id int64) error {
 	var voucherOrder voucher.VoucherOrder
-	if !errors.Is(DB.WithContext(ctx).Where("voucher_id = ? and user_id=?", id, userId).Limit(1).Find(&voucherOrder).Error, gorm.ErrRecordNotFound) {
-		return nil, errors.New("重复下单")
+	err = DB.WithContext(ctx).Where("voucher_id = ? and user_id=?", id, userId).Limit(1).Find(&voucherOrder).Error
+	fmt.Printf("voucherOrder: %v\n", voucherOrder)
+	if err != nil {
+		if !errors.Is(err, gorm.ErrRecordNotFound) {
+			return errors.New("重复下单")
+		}
+	} else if voucherOrder.ID != 0 {
+		return errors.New("重复下单")
 	}
-	return &voucherOrder, nil
+	return nil
 }
 
 func UpdateVoucherStock(ctx context.Context, id int64) error {
-	return DB.WithContext(ctx).Model(&voucher.SeckillVoucher{}).Where("voucher_id = ?", id).Update("stock", gorm.Expr("stock - ?", 1)).Error
+	result := DB.WithContext(ctx).Model(&voucher.SeckillVoucher{}).
+		Where("voucher_id = ? and stock > 0", id).
+		Update("stock", gorm.Expr("stock - ?", 1))
+	if result.RowsAffected == 0 {
+		return errors.New("库存不足，扣减失败")
+	}
+	return result.Error
 }
 
 func CreateVoucherOrder(ctx context.Context, voucherOrder *voucher.VoucherOrder) error {

biz/service/voucher/seckill_voucher.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"errors"
 	"github.com/cloudwego/hertz/pkg/app"
+	"sync"
 	"time"
 	"xzdp/biz/dal/mysql"
 	"xzdp/biz/dal/redis"
@@ -16,6 +17,8 @@ type SeckillVoucherService struct {
 	Context        context.Context
 }
 
+var mu sync.Mutex
+
 func NewSeckillVoucherService(Context context.Context, RequestContext *app.RequestContext) *SeckillVoucherService {
 	return &SeckillVoucherService{RequestContext: RequestContext, Context: Context}
 }
@@ -46,14 +49,20 @@ func (h *SeckillVoucherService) Run(req *int64) (resp *int64, err error) {
 	if voucher.GetStock() <= 0 {
 		return nil, errors.New("已抢空")
 	}
+	mu.Lock()
+	defer mu.Unlock()
+	return h.createOrder(*req)
+}
+
+func (h *SeckillVoucherService) createOrder(voucherId int64) (resp *int64, err error) {
 	//3.判断是否已经购买
 	userId := utils.GetUser(h.Context).GetID()
-	order, err := mysql.QueryVoucherOrderByVoucherID(h.Context, userId, *req)
-	if order != nil {
+	err = mysql.QueryVoucherOrderByVoucherID(h.Context, userId, voucherId)
+	if err != nil {
 		return nil, err
 	}
 	//4.扣减库存
-	err = mysql.UpdateVoucherStock(h.Context, *req)
+	err = mysql.UpdateVoucherStock(h.Context, voucherId)
 	if err != nil {
 		return nil, err
 	}
@@ -64,9 +73,9 @@ func (h *SeckillVoucherService) Run(req *int64) (resp *int64, err error) {
 	}
 	voucherOrder := &voucherModel.VoucherOrder{
 		UserId:     userId,
-		VoucherId:  *req,
+		VoucherId:  voucherId,
 		OrderId:    orderId,
-		PayTime:    time.Now().Format(layout),
+		PayTime:    time.Now().Format("2006-01-02T15:04:05+08:00"),
 		UseTime:    "0000-00-00 00:00:00",
 		RefundTime: "0000-00-00 00:00:00",
 	}