feat(cache): 实现 RoutingCache 和 StatsBuffer 优化数据库写入

- 新增 RoutingCache 组件，使用 sync.Map 缓存 Provider 和 Model
- 新增 StatsBuffer 组件，使用 sync.Map + atomic.Int64 缓冲统计数据
- 扩展 StatsRepository.BatchUpdate 支持批量增量更新
- 改造 RoutingService/StatsService/ProviderService/ModelService 集成缓存
- 更新 usage-statistics spec，新增 routing-cache 和 stats-buffer spec
- 新增单元测试覆盖缓存命中/失效/并发场景

backend/internal/service/service_test.go

@@ -8,6 +8,7 @@ import (
 	"github.com/google/uuid"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
+	"go.uber.org/zap"
 	"gorm.io/gorm"
 
 	testHelpers "nex/backend/tests"
@@ -22,13 +23,21 @@ func setupServiceTestDB(t *testing.T) *gorm.DB {
 	return testHelpers.SetupTestDB(t)
 }
 
+func setupRoutingCache(t *testing.T, db *gorm.DB) *RoutingCache {
+	t.Helper()
+	providerRepo := repository.NewProviderRepository(db)
+	modelRepo := repository.NewModelRepository(db)
+	return NewRoutingCache(modelRepo, providerRepo, zap.NewNop())
+}
+
 // ============ RoutingService - RouteByModelName 测试 ============
 
 func TestRoutingService_RouteByModelName_Success(t *testing.T) {
 	db := setupServiceTestDB(t)
 	providerRepo := repository.NewProviderRepository(db)
 	modelRepo := repository.NewModelRepository(db)
-	svc := NewRoutingService(modelRepo, providerRepo)
+	cache := setupRoutingCache(t, db)
+	svc := NewRoutingService(cache)
 
 	require.NoError(t, providerRepo.Create(&domain.Provider{ID: "openai", Name: "OpenAI", APIKey: "key", BaseURL: "https://api.openai.com", Enabled: true}))
 	require.NoError(t, modelRepo.Create(&domain.Model{ID: "m1", ProviderID: "openai", ModelName: "gpt-4", Enabled: true}))
@@ -41,9 +50,8 @@ func TestRoutingService_RouteByModelName_Success(t *testing.T) {
 
 func TestRoutingService_RouteByModelName_NotFound(t *testing.T) {
 	db := setupServiceTestDB(t)
-	providerRepo := repository.NewProviderRepository(db)
-	modelRepo := repository.NewModelRepository(db)
-	svc := NewRoutingService(modelRepo, providerRepo)
+	cache := setupRoutingCache(t, db)
+	svc := NewRoutingService(cache)
 
 	_, err := svc.RouteByModelName("openai", "nonexistent-model")
 	assert.True(t, errors.Is(err, appErrors.ErrModelNotFound))
@@ -53,7 +61,8 @@ func TestRoutingService_RouteByModelName_DisabledModel(t *testing.T) {
 	db := setupServiceTestDB(t)
 	providerRepo := repository.NewProviderRepository(db)
 	modelRepo := repository.NewModelRepository(db)
-	svc := NewRoutingService(modelRepo, providerRepo)
+	cache := setupRoutingCache(t, db)
+	svc := NewRoutingService(cache)
 
 	require.NoError(t, providerRepo.Create(&domain.Provider{ID: "openai", Name: "OpenAI", APIKey: "key", BaseURL: "https://api.openai.com", Enabled: true}))
 	require.NoError(t, modelRepo.Create(&domain.Model{ID: "m1", ProviderID: "openai", ModelName: "gpt-4", Enabled: true}))
@@ -67,7 +76,8 @@ func TestRoutingService_RouteByModelName_DisabledProvider(t *testing.T) {
 	db := setupServiceTestDB(t)
 	providerRepo := repository.NewProviderRepository(db)
 	modelRepo := repository.NewModelRepository(db)
-	svc := NewRoutingService(modelRepo, providerRepo)
+	cache := setupRoutingCache(t, db)
+	svc := NewRoutingService(cache)
 
 	require.NoError(t, providerRepo.Create(&domain.Provider{ID: "openai", Name: "OpenAI", APIKey: "key", BaseURL: "https://api.openai.com", Enabled: true}))
 	require.NoError(t, modelRepo.Create(&domain.Model{ID: "m1", ProviderID: "openai", ModelName: "gpt-4", Enabled: true}))
@@ -83,7 +93,8 @@ func TestModelService_Create_GeneratesUUID(t *testing.T) {
 	db := setupServiceTestDB(t)
 	providerRepo := repository.NewProviderRepository(db)
 	modelRepo := repository.NewModelRepository(db)
-	svc := NewModelService(modelRepo, providerRepo)
+	cache := setupRoutingCache(t, db)
+	svc := NewModelService(modelRepo, providerRepo, cache)
 
 	require.NoError(t, providerRepo.Create(&domain.Provider{ID: "openai", Name: "OpenAI", APIKey: "key", BaseURL: "https://api.openai.com"}))
 
@@ -91,12 +102,10 @@ func TestModelService_Create_GeneratesUUID(t *testing.T) {
 	err := svc.Create(model)
 	require.NoError(t, err)
 
-	// 验证返回的 model 拥有有效的 UUID
 	assert.NotEmpty(t, model.ID)
 	_, err = uuid.Parse(model.ID)
 	assert.NoError(t, err, "model.ID should be a valid UUID")
 
-	// 通过 Get 验证持久化
 	stored, err := svc.Get(model.ID)
 	require.NoError(t, err)
 	assert.Equal(t, model.ID, stored.ID)
@@ -107,7 +116,8 @@ func TestModelService_Create_DuplicateModelName(t *testing.T) {
 	db := setupServiceTestDB(t)
 	providerRepo := repository.NewProviderRepository(db)
 	modelRepo := repository.NewModelRepository(db)
-	svc := NewModelService(modelRepo, providerRepo)
+	cache := setupRoutingCache(t, db)
+	svc := NewModelService(modelRepo, providerRepo, cache)
 
 	require.NoError(t, providerRepo.Create(&domain.Provider{ID: "openai", Name: "OpenAI", APIKey: "key", BaseURL: "https://api.openai.com"}))
 
@@ -115,7 +125,6 @@ func TestModelService_Create_DuplicateModelName(t *testing.T) {
 	err := svc.Create(model1)
 	require.NoError(t, err)
 
-	// 使用相同的 (providerID, modelName) 创建第二个模型应失败
 	model2 := &domain.Model{ProviderID: "openai", ModelName: "gpt-4"}
 	err = svc.Create(model2)
 	assert.True(t, errors.Is(err, appErrors.ErrDuplicateModel))
@@ -125,7 +134,8 @@ func TestModelService_Create_ProviderNotFound(t *testing.T) {
 	db := setupServiceTestDB(t)
 	providerRepo := repository.NewProviderRepository(db)
 	modelRepo := repository.NewModelRepository(db)
-	svc := NewModelService(modelRepo, providerRepo)
+	 cache := setupRoutingCache(t, db)
+	svc := NewModelService(modelRepo, providerRepo, cache)
 
 	model := &domain.Model{ProviderID: "nonexistent", ModelName: "gpt-4"}
 	err := svc.Create(model)
@@ -138,7 +148,8 @@ func TestProviderService_Create_InvalidID(t *testing.T) {
 	db := setupServiceTestDB(t)
 	repo := repository.NewProviderRepository(db)
 	modelRepo := repository.NewModelRepository(db)
-	svc := NewProviderService(repo, modelRepo)
+	 cache := setupRoutingCache(t, db)
+	svc := NewProviderService(repo, modelRepo, cache)
 
 	provider := &domain.Provider{ID: "open-ai", Name: "OpenAI", APIKey: "key", BaseURL: "https://api.openai.com"}
 	err := svc.Create(provider)
@@ -149,7 +160,8 @@ func TestProviderService_Create_ValidID(t *testing.T) {
 	db := setupServiceTestDB(t)
 	repo := repository.NewProviderRepository(db)
 	modelRepo := repository.NewModelRepository(db)
-	svc := NewProviderService(repo, modelRepo)
+	 cache := setupRoutingCache(t, db)
+	svc := NewProviderService(repo, modelRepo, cache)
 
 	provider := &domain.Provider{ID: "openai", Name: "OpenAI", APIKey: "key", BaseURL: "https://api.openai.com"}
 	err := svc.Create(provider)
@@ -164,7 +176,8 @@ func TestModelService_Update_DuplicateModelName(t *testing.T) {
 	db := setupServiceTestDB(t)
 	providerRepo := repository.NewProviderRepository(db)
 	modelRepo := repository.NewModelRepository(db)
-	svc := NewModelService(modelRepo, providerRepo)
+	 cache := setupRoutingCache(t, db)
+	svc := NewModelService(modelRepo, providerRepo, cache)
 
 	require.NoError(t, providerRepo.Create(&domain.Provider{ID: "openai", Name: "OpenAI", APIKey: "key", BaseURL: "https://api.openai.com"}))
 	require.NoError(t, providerRepo.Create(&domain.Provider{ID: "anthropic", Name: "Anthropic", APIKey: "key", BaseURL: "https://api.anthropic.com"}))
@@ -189,7 +202,8 @@ func TestModelService_Update_ModelNotFound(t *testing.T) {
 	db := setupServiceTestDB(t)
 	providerRepo := repository.NewProviderRepository(db)
 	modelRepo := repository.NewModelRepository(db)
-	svc := NewModelService(modelRepo, providerRepo)
+	 cache := setupRoutingCache(t, db)
+	svc := NewModelService(modelRepo, providerRepo, cache)
 
 	err := svc.Update("nonexistent-id", map[string]interface{}{
 		"model_name": "gpt-4",
@@ -201,7 +215,8 @@ func TestModelService_Update_Success(t *testing.T) {
 	db := setupServiceTestDB(t)
 	providerRepo := repository.NewProviderRepository(db)
 	modelRepo := repository.NewModelRepository(db)
-	svc := NewModelService(modelRepo, providerRepo)
+	 cache := setupRoutingCache(t, db)
+	svc := NewModelService(modelRepo, providerRepo, cache)
 
 	require.NoError(t, providerRepo.Create(&domain.Provider{ID: "openai", Name: "OpenAI", APIKey: "key", BaseURL: "https://api.openai.com"}))
 
@@ -226,7 +241,8 @@ func TestProviderService_Update_ImmutableID(t *testing.T) {
 	db := setupServiceTestDB(t)
 	repo := repository.NewProviderRepository(db)
 	modelRepo := repository.NewModelRepository(db)
-	svc := NewProviderService(repo, modelRepo)
+	 cache := setupRoutingCache(t, db)
+	svc := NewProviderService(repo, modelRepo, cache)
 
 	provider := &domain.Provider{ID: "openai", Name: "OpenAI", APIKey: "key", BaseURL: "https://api.openai.com"}
 	err := svc.Create(provider)
@@ -243,7 +259,8 @@ func TestProviderService_Update_Success(t *testing.T) {
 	db := setupServiceTestDB(t)
 	repo := repository.NewProviderRepository(db)
 	modelRepo := repository.NewModelRepository(db)
-	svc := NewProviderService(repo, modelRepo)
+	 cache := setupRoutingCache(t, db)
+	svc := NewProviderService(repo, modelRepo, cache)
 
 	provider := &domain.Provider{ID: "openai", Name: "OpenAI", APIKey: "key", BaseURL: "https://api.openai.com"}
 	err := svc.Create(provider)
@@ -301,7 +318,7 @@ func TestStatsService_Aggregate_ByModel(t *testing.T) {
 		t.Run(tt.name, func(t *testing.T) {
 			db := setupServiceTestDB(t)
 			statsRepo := repository.NewStatsRepository(db)
-			svc := NewStatsService(statsRepo)
+			buffer := NewStatsBuffer(statsRepo, nil); svc := NewStatsService(statsRepo, buffer)
 
 			result := svc.Aggregate(tt.stats, "model")
 
@@ -362,7 +379,7 @@ func TestStatsService_Aggregate_ByDate(t *testing.T) {
 		t.Run(tt.name, func(t *testing.T) {
 			db := setupServiceTestDB(t)
 			statsRepo := repository.NewStatsRepository(db)
-			svc := NewStatsService(statsRepo)
+			buffer := NewStatsBuffer(statsRepo, nil); svc := NewStatsService(statsRepo, buffer)
 
 			result := svc.Aggregate(tt.stats, "date")
 
@@ -431,7 +448,8 @@ func TestProviderService_List_APIKeyNotMasked(t *testing.T) {
 	db := setupServiceTestDB(t)
 	repo := repository.NewProviderRepository(db)
 	modelRepo := repository.NewModelRepository(db)
-	svc := NewProviderService(repo, modelRepo)
+	 cache := setupRoutingCache(t, db)
+	svc := NewProviderService(repo, modelRepo, cache)
 
 	provider1 := &domain.Provider{ID: "openai", Name: "OpenAI", APIKey: "sk-1234567890", BaseURL: "https://api.openai.com"}
 	provider2 := &domain.Provider{ID: "anthropic", Name: "Anthropic", APIKey: "sk-anthropic1234", BaseURL: "https://api.anthropic.com"}
@@ -456,7 +474,8 @@ func TestModelService_ConcurrentCreate(t *testing.T) {
 	db := setupServiceTestDB(t)
 	providerRepo := repository.NewProviderRepository(db)
 	modelRepo := repository.NewModelRepository(db)
-	svc := NewModelService(modelRepo, providerRepo)
+	 cache := setupRoutingCache(t, db)
+	svc := NewModelService(modelRepo, providerRepo, cache)
 
 	require.NoError(t, providerRepo.Create(&domain.Provider{ID: "openai", Name: "OpenAI", APIKey: "key", BaseURL: "https://api.openai.com"}))