feat: 平台 AI 预算、成本熔断与全局限流 (API-AI-071)

- PlatformBudgetService: checkPlatformBudget / recordSuccess / recordFailure
- 熔断器: closed → open (连续失败N次) → half_open (限制任务数) → closed
- 平台日 token 预算 + 成本预算检查
- Admin 接口: transitionToHalfOpen / closeCircuit / getBudgetState
- PlatformAiBudgetDaily 已存在于 Prisma schema

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

src/modules/ai-runtime/ai-runtime.module.ts

@@ -7,11 +7,12 @@ import { CredentialEncryptionService } from './credential-encryption.service';
 import { RuntimeInternalController } from './internal/runtime-internal.controller';
 import { RuntimeInternalService } from './internal/runtime-internal.service';
 import { UserAiQuotaService } from './user-ai-quota.service';
+import { PlatformBudgetService } from './platform-budget.service';
 
 @Module({
   imports: [ConfigModule, PrismaModule],
   controllers: [UserAiController, RuntimeInternalController],
-  providers: [UserAiService, CredentialEncryptionService, RuntimeInternalService, UserAiQuotaService],
-  exports: [UserAiService, CredentialEncryptionService, RuntimeInternalService, UserAiQuotaService],
+  providers: [UserAiService, CredentialEncryptionService, RuntimeInternalService, UserAiQuotaService, PlatformBudgetService],
+  exports: [UserAiService, CredentialEncryptionService, RuntimeInternalService, UserAiQuotaService, PlatformBudgetService],
 })
 export class AiRuntimeModule {}

src/modules/ai-runtime/platform-budget.service.ts

@@ -0,0 +1,182 @@
+import { Injectable, BadRequestException } from '@nestjs/common';
+import { PrismaService } from '../../infrastructure/database/prisma.service';
+
+interface BudgetConfig {
+  maxDailyTokens: number;
+  maxDailyCostCents: number;
+  consecutiveFailureThreshold: number;
+  halfOpenMaxJobs: number;
+}
+
+const DEFAULT_CONFIG: BudgetConfig = {
+  maxDailyTokens: 10_000_000,
+  maxDailyCostCents: 50_000, // $500
+  consecutiveFailureThreshold: 10,
+  halfOpenMaxJobs: 2,
+};
+
+@Injectable()
+export class PlatformBudgetService {
+  constructor(private readonly prisma: PrismaService) {}
+
+  private today(): Date {
+    const d = new Date();
+    return new Date(Date.UTC(d.getFullYear(), d.getMonth(), d.getDate()));
+  }
+
+  private async getOrCreateDaily(provider: string, model: string) {
+    const localDate = this.today();
+    let budget = await this.prisma.platformAiBudgetDaily.findUnique({
+      where: { localDate_provider_model: { localDate, provider, model } },
+    });
+    if (!budget) {
+      budget = await this.prisma.platformAiBudgetDaily.create({
+        data: { localDate, provider, model },
+      });
+    }
+    return budget;
+  }
+
+  /** Check if platform_key job can be created. Throws if blocked. */
+  async checkPlatformBudget(provider: string, model: string): Promise<void> {
+    const budget = await this.getOrCreateDaily(provider, model);
+
+    if (budget.circuitBreakerStatus === 'open') {
+      throw new BadRequestException({
+        errorCode: 'PLATFORM_CIRCUIT_OPEN',
+        message: `Platform circuit breaker is open. Reason: ${budget.circuitBreakerReason ?? 'failure threshold reached'}`,
+      });
+    }
+
+    if (budget.circuitBreakerStatus === 'half_open') {
+      // Allow only limited jobs in half_open state
+      const halfOpenJobs = await this.prisma.aiRuntimeJob.count({
+        where: {
+          status: { in: ['pending', 'locked', 'running'] },
+          apiKeyMode: 'platform_key',
+        },
+      });
+      if (halfOpenJobs >= DEFAULT_CONFIG.halfOpenMaxJobs) {
+        throw new BadRequestException({
+          errorCode: 'PLATFORM_CIRCUIT_HALF_OPEN',
+          message: 'Platform circuit breaker is half-open; limited capacity reached',
+        });
+      }
+    }
+
+    if (budget.totalTokens >= DEFAULT_CONFIG.maxDailyTokens) {
+      throw new BadRequestException({
+        errorCode: 'PLATFORM_TOKEN_BUDGET_EXCEEDED',
+        message: `Daily platform token budget (${DEFAULT_CONFIG.maxDailyTokens}) exceeded`,
+      });
+    }
+
+    if (budget.costEstimate >= DEFAULT_CONFIG.maxDailyCostCents) {
+      throw new BadRequestException({
+        errorCode: 'PLATFORM_COST_BUDGET_EXCEEDED',
+        message: `Daily platform cost budget (${DEFAULT_CONFIG.maxDailyCostCents} cents) exceeded`,
+      });
+    }
+  }
+
+  /** Record successful token usage after a platform_key invocation */
+  async recordSuccess(
+    provider: string, model: string,
+    inputTokens: number, outputTokens: number, totalTokens: number,
+    costEstimate: number,
+  ): Promise<void> {
+    const localDate = this.today();
+    await this.prisma.platformAiBudgetDaily.upsert({
+      where: { localDate_provider_model: { localDate, provider, model } },
+      create: {
+        localDate, provider, model,
+        inputTokens, outputTokens, totalTokens,
+        costEstimate, jobCount: 1,
+      },
+      update: {
+        inputTokens: { increment: inputTokens },
+        outputTokens: { increment: outputTokens },
+        totalTokens: { increment: totalTokens },
+        costEstimate: { increment: costEstimate },
+        jobCount: { increment: 1 },
+        // Success resets consecutive failure count
+        failedCount: 0,
+        // Transition half_open → closed on success
+        circuitBreakerStatus: 'closed',
+        circuitBreakerReason: null,
+      },
+    });
+  }
+
+  /** Record failed platform_key invocation, potentially triggering circuit breaker */
+  async recordFailure(
+    provider: string, model: string,
+    errorCode: string,
+  ): Promise<void> {
+    const localDate = this.today();
+    const budget = await this.getOrCreateDaily(provider, model);
+    const newFailed = budget.failedCount + 1;
+
+    const update: any = {
+      failedCount: newFailed,
+      jobCount: { increment: 1 },
+    };
+
+    if (newFailed >= DEFAULT_CONFIG.consecutiveFailureThreshold) {
+      update.circuitBreakerStatus = 'open';
+      update.circuitBreakerReason = `Consecutive failures reached ${newFailed}/${DEFAULT_CONFIG.consecutiveFailureThreshold}. Last error: ${errorCode}`;
+    }
+
+    await this.prisma.platformAiBudgetDaily.upsert({
+      where: { localDate_provider_model: { localDate, provider, model } },
+      create: {
+        localDate, provider, model,
+        failedCount: 1,
+        jobCount: 1,
+        circuitBreakerStatus: 'closed',
+      },
+      update,
+    });
+  }
+
+  /** Admin: manually transition circuit breaker to half_open for testing */
+  async transitionToHalfOpen(provider: string, model: string): Promise<void> {
+    const localDate = this.today();
+    await this.prisma.platformAiBudgetDaily.upsert({
+      where: { localDate_provider_model: { localDate, provider, model } },
+      create: { localDate, provider, model, circuitBreakerStatus: 'half_open' },
+      update: { circuitBreakerStatus: 'half_open', circuitBreakerReason: 'Manually set to half_open by admin' },
+    });
+  }
+
+  /** Admin: manually close circuit breaker */
+  async closeCircuit(provider: string, model: string): Promise<void> {
+    const localDate = this.today();
+    await this.prisma.platformAiBudgetDaily.upsert({
+      where: { localDate_provider_model: { localDate, provider, model } },
+      create: { localDate, provider, model, circuitBreakerStatus: 'closed' },
+      update: { circuitBreakerStatus: 'closed', circuitBreakerReason: null, failedCount: 0 },
+    });
+  }
+
+  /** Get current platform budget state */
+  async getBudgetState(provider: string, model: string) {
+    const budget = await this.getOrCreateDaily(provider, model);
+    return {
+      provider: budget.provider,
+      model: budget.model,
+      localDate: budget.localDate.toISOString(),
+      totalTokens: budget.totalTokens,
+      costEstimateCents: budget.costEstimate,
+      jobCount: budget.jobCount,
+      failedCount: budget.failedCount,
+      circuitBreakerStatus: budget.circuitBreakerStatus,
+      circuitBreakerReason: budget.circuitBreakerReason,
+      limits: {
+        maxDailyTokens: DEFAULT_CONFIG.maxDailyTokens,
+        maxDailyCostCents: DEFAULT_CONFIG.maxDailyCostCents,
+        consecutiveFailureThreshold: DEFAULT_CONFIG.consecutiveFailureThreshold,
+      },
+    };
+  }
+}