fix(infra): resolve NestJS dist build and Prometheus target issues

NestJS: disable incremental in 6 services tsconfig.json to fix dist
not emitted when nest-cli deleteOutDir conflicts with tsc tsbuildinfo.
classes/iam: import HealthModule in AppModule to fix /healthz 404.
classes: rewrite HealthController to Drizzle getDb from TypeORM DI.
teacher-bff: add /metrics endpoint for Prometheus scraping.
infra: add node/mysql/redis exporters to observability profile.
mysql-exporter v0.15.1 uses command-line flags not DATA_SOURCE_NAME.
prometheus: enable web.enable-lifecycle for hot reload.

services/classes/src/app.module.ts

@@ -1,7 +1,8 @@
-import { Module } from '@nestjs/common';
-import { ClassesModule } from './classes/classes.module.js';
+import { Module } from "@nestjs/common";
+import { ClassesModule } from "./classes/classes.module.js";
+import { HealthModule } from "./shared/health/health.module.js";
 
 @Module({
-  imports: [ClassesModule],
+  imports: [ClassesModule, HealthModule],
 })
 export class AppModule {}

services/classes/src/shared/health/health.controller.ts

@@ -1,7 +1,8 @@
-import { Controller, Get, HttpException, HttpStatus } from '@nestjs/common';
-import { DataSource } from 'typeorm';
+import { Controller, Get, HttpException, HttpStatus } from "@nestjs/common";
+import { sql } from "drizzle-orm";
+import { getDb } from "../../config/database.js";
 
-const SERVICE_NAME = 'classes';
+const SERVICE_NAME = "classes";
 
 /**
  * 健康检查端点。
@@ -14,33 +15,37 @@ const SERVICE_NAME = 'classes';
  */
 @Controller()
 export class HealthController {
-  constructor(private readonly dataSource: DataSource) {}
-
-  @Get('healthz')
+  @Get("healthz")
   liveness(): { status: string; service: string; timestamp: string } {
     return {
-      status: 'ok',
+      status: "ok",
       service: SERVICE_NAME,
       timestamp: new Date().toISOString(),
     };
   }
 
-  @Get('readyz')
-  async readiness(): Promise<{ status: string; service: string; timestamp: string }> {
+  @Get("readyz")
+  async readiness(): Promise<{
+    status: string;
+    service: string;
+    timestamp: string;
+  }> {
     try {
-      await this.dataSource.query('SELECT 1');
+      const db = getDb();
+      await db.execute(sql`SELECT 1`);
       return {
-        status: 'ok',
+        status: "ok",
         service: SERVICE_NAME,
         timestamp: new Date().toISOString(),
       };
     } catch (error) {
       throw new HttpException(
         {
-          status: 'error',
+          status: "error",
           service: SERVICE_NAME,
           timestamp: new Date().toISOString(),
-          error: error instanceof Error ? error.message : 'database unreachable',
+          error:
+            error instanceof Error ? error.message : "database unreachable",
         },
         HttpStatus.SERVICE_UNAVAILABLE,
       );

services/classes/tsconfig.json

@@ -8,6 +8,7 @@
     "emitDecoratorMetadata": true,
     "outDir": "./dist",
     "rootDir": "./src",
+    "incremental": false,
     "types": ["node"]
   },
   "include": ["src/**/*"],

services/content/tsconfig.json

@@ -8,6 +8,7 @@
     "emitDecoratorMetadata": true,
     "outDir": "./dist",
     "rootDir": "./src",
+    "incremental": false,
     "types": ["node"]
   },
   "include": ["src/**/*"],

services/core-edu/tsconfig.json

@@ -8,6 +8,7 @@
     "emitDecoratorMetadata": true,
     "outDir": "./dist",
     "rootDir": "./src",
+    "incremental": false,
     "types": ["node"]
   },
   "include": ["src/**/*"],

services/iam/src/app.module.ts

@@ -1,7 +1,8 @@
-import { Module } from '@nestjs/common';
-import { IamModule } from './iam/iam.module.js';
+import { Module } from "@nestjs/common";
+import { IamModule } from "./iam/iam.module.js";
+import { HealthModule } from "./shared/health/health.module.js";
 
 @Module({
-  imports: [IamModule],
+  imports: [IamModule, HealthModule],
 })
 export class AppModule {}

services/iam/tsconfig.json

@@ -8,6 +8,7 @@
     "emitDecoratorMetadata": true,
     "outDir": "./dist",
     "rootDir": "./src",
+    "incremental": false,
     "types": ["node"]
   },
   "include": ["src/**/*"],

services/msg/tsconfig.json

@@ -8,6 +8,7 @@
     "emitDecoratorMetadata": true,
     "outDir": "./dist",
     "rootDir": "./src",
+    "incremental": false,
     "types": ["node"]
   },
   "include": ["src/**/*"],

services/teacher-bff/src/main.ts

@@ -3,6 +3,7 @@ import { NestFactory } from "@nestjs/core";
 import { AppModule } from "./app.module.js";
 import { env } from "./config/env.js";
 import { initTracer, shutdownTracer } from "./shared/observability/tracer.js";
+import { metricsRegistry } from "./shared/observability/metrics.js";
 
 async function bootstrap(): Promise<void> {
   initTracer();
@@ -12,6 +13,12 @@ async function bootstrap(): Promise<void> {
 
   app.enableShutdownHooks();
 
+  // Prometheus 指标端点：不鉴权，供 Prometheus 抓取。
+  app.getHttpAdapter().get("/metrics", async (_req, res) => {
+    res.set("Content-Type", metricsRegistry.contentType);
+    res.end(await metricsRegistry.metrics());
+  });
+
   await app.listen(env.PORT);
   console.log(`Teacher BFF started on port ${env.PORT}`);
 

services/teacher-bff/src/shared/observability/metrics.ts

@@ -0,0 +1,26 @@
+import promClient from "prom-client";
+
+const registry = new promClient.Registry();
+registry.setDefaultLabels({ service: "teacher-bff" });
+
+registry.registerMetric(
+  new promClient.Counter({
+    name: "teacher_bff_requests_total",
+    help: "Total number of teacher-bff requests",
+    labelNames: ["method", "endpoint", "status"],
+  }),
+);
+
+registry.registerMetric(
+  new promClient.Histogram({
+    name: "teacher_bff_request_duration_seconds",
+    help: "Teacher-bff request duration in seconds",
+    labelNames: ["method", "endpoint"],
+    buckets: [0.01, 0.05, 0.1, 0.3, 0.5, 1, 3, 5],
+  }),
+);
+
+// 自动收集 Node.js 进程级指标（CPU/内存/事件循环/GC等）
+promClient.collectDefaultMetrics({ register: registry });
+
+export { registry as metricsRegistry };

services/teacher-bff/tsconfig.json

@@ -8,6 +8,7 @@
     "emitDecoratorMetadata": true,
     "outDir": "./dist",
     "rootDir": "./src",
+    "incremental": false,
     "types": ["node"]
   },
   "include": ["src/**/*"],