feat(observability): add structured request logs with request-id middleware

Fabric.Backend.Center/src/common/request-context.middleware.ts

@@ -0,0 +1,30 @@
+import { randomUUID } from 'crypto';
+import { NextFunction, Request, Response } from 'express';
+
+type ReqWithId = Request & { requestId?: string };
+
+export function requestContextMiddleware(req: ReqWithId, res: Response, next: NextFunction): void {
+  const headerId = req.headers['x-request-id'];
+  const requestId =
+    (Array.isArray(headerId) ? headerId[0] : headerId) || randomUUID();
+
+  req.requestId = requestId;
+  res.setHeader('x-request-id', requestId);
+
+  const startedAt = Date.now();
+  res.on('finish', () => {
+    const log = {
+      level: 'info',
+      service: 'center',
+      requestId,
+      method: req.method,
+      path: req.originalUrl,
+      statusCode: res.statusCode,
+      durationMs: Date.now() - startedAt,
+      timestamp: new Date().toISOString(),
+    };
+    console.log(JSON.stringify(log));
+  });
+
+  next();
+}

Fabric.Backend.Center/src/main.ts

@@ -3,6 +3,7 @@ import { ValidationPipe } from '@nestjs/common';
 import { NestFactory } from '@nestjs/core';
 import { DocumentBuilder, SwaggerModule } from '@nestjs/swagger';
 import { AppModule } from './app.module';
+import { requestContextMiddleware } from './common/request-context.middleware';
 
 function requireEnv(name: string): string {
   const value = process.env[name];
@@ -28,6 +29,7 @@ async function bootstrap() {
 
   const app = await NestFactory.create(AppModule);
   app.setGlobalPrefix('api');
+  app.use(requestContextMiddleware);
   app.useGlobalPipes(
     new ValidationPipe({
       whitelist: true,