fix(usage): 使用日志事务和幂等性修复

- UsageLogRepository.Create 返回 inserted 标志
- UsageService 使用事务保证原子性
- 避免重复扣费（幂等重试场景）
- 更新依赖注入和测试

backend/cmd/server/wire_gen.go

@@ -62,7 +62,7 @@ func initializeApplication(buildInfo handler.BuildInfo) (*Application, error) {
 	apiKeyService := service.NewApiKeyService(apiKeyRepository, userRepository, groupRepository, userSubscriptionRepository, apiKeyCache, configConfig)
 	apiKeyHandler := handler.NewAPIKeyHandler(apiKeyService)
 	usageLogRepository := repository.NewUsageLogRepository(client, db)
-	usageService := service.NewUsageService(usageLogRepository, userRepository)
+	usageService := service.NewUsageService(usageLogRepository, userRepository, client)
 	usageHandler := handler.NewUsageHandler(usageService, apiKeyService)
 	redeemCodeRepository := repository.NewRedeemCodeRepository(client)
 	billingCache := repository.NewBillingCache(redisClient)
@@ -100,7 +100,7 @@ func initializeApplication(buildInfo handler.BuildInfo) (*Application, error) {
 	antigravityOAuthService := service.NewAntigravityOAuthService(proxyRepository)
 	antigravityTokenProvider := service.NewAntigravityTokenProvider(accountRepository, geminiTokenCache, antigravityOAuthService)
 	httpUpstream := repository.NewHTTPUpstream(configConfig)
-	antigravityGatewayService := service.NewAntigravityGatewayService(accountRepository, gatewayCache, antigravityTokenProvider, rateLimitService, httpUpstream)
+	antigravityGatewayService := service.NewAntigravityGatewayService(accountRepository, gatewayCache, antigravityTokenProvider, rateLimitService, httpUpstream, settingService)
 	accountTestService := service.NewAccountTestService(accountRepository, oAuthService, openAIOAuthService, geminiTokenProvider, antigravityGatewayService, httpUpstream)
 	concurrencyCache := repository.ProvideConcurrencyCache(redisClient, configConfig)
 	concurrencyService := service.ProvideConcurrencyService(concurrencyCache, accountRepository, configConfig)

backend/internal/repository/usage_log_repo.go

@@ -61,9 +61,16 @@ func (r *usageLogRepository) getPerformanceStats(ctx context.Context, userID int
 	return requestCount / 5, tokenCount / 5, nil
 }
 
-func (r *usageLogRepository) Create(ctx context.Context, log *service.UsageLog) error {
+func (r *usageLogRepository) Create(ctx context.Context, log *service.UsageLog) (bool, error) {
 	if log == nil {
-		return nil
+		return false, nil
+	}
+
+	// 在事务上下文中，使用 tx 绑定的 ExecQuerier 执行原生 SQL，保证与其他更新同事务。
+	// 无事务时回退到默认的 *sql.DB 执行器。
+	sqlq := r.sql
+	if tx := dbent.TxFromContext(ctx); tx != nil {
+		sqlq = tx.Client()
 	}
 
 	createdAt := log.CreatedAt
@@ -152,18 +159,20 @@ func (r *usageLogRepository) Create(ctx context.Context, log *service.UsageLog)
 		firstToken,
 		createdAt,
 	}
-	if err := scanSingleRow(ctx, r.sql, query, args, &log.ID, &log.CreatedAt); err != nil {
+	if err := scanSingleRow(ctx, sqlq, query, args, &log.ID, &log.CreatedAt); err != nil {
 		if errors.Is(err, sql.ErrNoRows) && requestID != "" {
 			selectQuery := "SELECT id, created_at FROM usage_logs WHERE request_id = $1 AND api_key_id = $2"
-			if err := scanSingleRow(ctx, r.sql, selectQuery, []any{requestID, log.ApiKeyID}, &log.ID, &log.CreatedAt); err != nil {
-				return err
+			if err := scanSingleRow(ctx, sqlq, selectQuery, []any{requestID, log.ApiKeyID}, &log.ID, &log.CreatedAt); err != nil {
+				return false, err
 			}
+			log.RateMultiplier = rateMultiplier
+			return false, nil
 		} else {
-			return err
+			return false, err
 		}
 	}
 	log.RateMultiplier = rateMultiplier
-	return nil
+	return true, nil
 }
 
 func (r *usageLogRepository) GetByID(ctx context.Context, id int64) (log *service.UsageLog, err error) {

backend/internal/server/api_contract_test.go

@@ -380,7 +380,7 @@ func newContractDeps(t *testing.T) *contractDeps {
 	apiKeyService := service.NewApiKeyService(apiKeyRepo, userRepo, groupRepo, userSubRepo, apiKeyCache, cfg)
 
 	usageRepo := newStubUsageLogRepo()
-	usageService := service.NewUsageService(usageRepo, userRepo)
+	usageService := service.NewUsageService(usageRepo, userRepo, client)
 
 	settingRepo := newStubSettingRepo()
 	settingService := service.NewSettingService(settingRepo, cfg)

backend/internal/service/account_usage_service.go

@@ -12,7 +12,9 @@ import (
 )
 
 type UsageLogRepository interface {
-	Create(ctx context.Context, log *UsageLog) error
+	// Create creates a usage log and returns whether it was actually inserted.
+	// inserted is false when the insert was skipped due to conflict (idempotent retries).
+	Create(ctx context.Context, log *UsageLog) (inserted bool, err error)
 	GetByID(ctx context.Context, id int64) (*UsageLog, error)
 	Delete(ctx context.Context, id int64) error
 

backend/internal/service/openai_gateway_service.go

@@ -1026,22 +1026,23 @@ func (s *OpenAIGatewayService) RecordUsage(ctx context.Context, input *OpenAIRec
 		usageLog.SubscriptionID = &subscription.ID
 	}
 
-	_ = s.usageLogRepo.Create(ctx, usageLog)
-
+	inserted, err := s.usageLogRepo.Create(ctx, usageLog)
 	if s.cfg != nil && s.cfg.RunMode == config.RunModeSimple {
 		log.Printf("[SIMPLE MODE] Usage recorded (not billed): user=%d, tokens=%d", usageLog.UserID, usageLog.TotalTokens())
 		s.deferredService.ScheduleLastUsedUpdate(account.ID)
 		return nil
 	}
 
+	shouldBill := inserted || err != nil
+
 	// Deduct based on billing type
 	if isSubscriptionBilling {
-		if cost.TotalCost > 0 {
+		if shouldBill && cost.TotalCost > 0 {
 			_ = s.userSubRepo.IncrementUsage(ctx, subscription.ID, cost.TotalCost)
 			s.billingCacheService.QueueUpdateSubscriptionUsage(user.ID, *apiKey.GroupID, cost.TotalCost)
 		}
 	} else {
-		if cost.ActualCost > 0 {
+		if shouldBill && cost.ActualCost > 0 {
 			_ = s.userRepo.DeductBalance(ctx, user.ID, cost.ActualCost)
 			s.billingCacheService.QueueDeductBalance(user.ID, cost.ActualCost)
 		}

backend/internal/service/usage_service.go

@@ -2,9 +2,11 @@ package service
 
 import (
 	"context"
+	"errors"
 	"fmt"
 	"time"
 
+	dbent "github.com/Wei-Shaw/sub2api/ent"
 	infraerrors "github.com/Wei-Shaw/sub2api/internal/pkg/errors"
 	"github.com/Wei-Shaw/sub2api/internal/pkg/pagination"
 	"github.com/Wei-Shaw/sub2api/internal/pkg/usagestats"
@@ -54,20 +56,34 @@ type UsageStats struct {
 type UsageService struct {
 	usageRepo UsageLogRepository
 	userRepo  UserRepository
+	entClient *dbent.Client
 }
 
 // NewUsageService 创建使用统计服务实例
-func NewUsageService(usageRepo UsageLogRepository, userRepo UserRepository) *UsageService {
+func NewUsageService(usageRepo UsageLogRepository, userRepo UserRepository, entClient *dbent.Client) *UsageService {
 	return &UsageService{
 		usageRepo: usageRepo,
 		userRepo:  userRepo,
+		entClient: entClient,
 	}
 }
 
 // Create 创建使用日志
 func (s *UsageService) Create(ctx context.Context, req CreateUsageLogRequest) (*UsageLog, error) {
+	// 使用数据库事务保证「使用日志插入」与「扣费」的原子性，避免重复扣费或漏扣风险。
+	tx, err := s.entClient.Tx(ctx)
+	if err != nil && !errors.Is(err, dbent.ErrTxStarted) {
+		return nil, fmt.Errorf("begin transaction: %w", err)
+	}
+
+	txCtx := ctx
+	if err == nil {
+		defer tx.Rollback()
+		txCtx = dbent.NewTxContext(ctx, tx)
+	}
+
 	// 验证用户存在
-	_, err := s.userRepo.GetByID(ctx, req.UserID)
+	_, err = s.userRepo.GetByID(txCtx, req.UserID)
 	if err != nil {
 		return nil, fmt.Errorf("get user: %w", err)
 	}
@@ -96,17 +112,24 @@ func (s *UsageService) Create(ctx context.Context, req CreateUsageLogRequest) (*
 		DurationMs:            req.DurationMs,
 	}
 
-	if err := s.usageRepo.Create(ctx, usageLog); err != nil {
+	inserted, err := s.usageRepo.Create(txCtx, usageLog)
+	if err != nil {
 		return nil, fmt.Errorf("create usage log: %w", err)
 	}
 
 	// 扣除用户余额
-	if req.ActualCost > 0 {
-		if err := s.userRepo.UpdateBalance(ctx, req.UserID, -req.ActualCost); err != nil {
+	if inserted && req.ActualCost > 0 {
+		if err := s.userRepo.UpdateBalance(txCtx, req.UserID, -req.ActualCost); err != nil {
 			return nil, fmt.Errorf("update user balance: %w", err)
 		}
 	}
 
+	if tx != nil {
+		if err := tx.Commit(); err != nil {
+			return nil, fmt.Errorf("commit transaction: %w", err)
+		}
+	}
+
 	return usageLog, nil
 }