Request ID + structured logging (Express + pino)

                  import type { NextFunction, Request, Response } from 'express';
import crypto from 'node:crypto';
import pino from 'pino';

const baseLogger = pino({
  level: process.env.LOG_LEVEL ?? 'info',
  redact: ['req.headers.authorization', 'req.headers.cookie']
});

declare global {
  namespace Express {
    interface Request {
      requestId: string;
      log: pino.Logger;
    }
  }
}

export function requestIdAndLogger(req: Request, res: Response, next: NextFunction) {
  const incoming = req.header('x-request-id');
  const requestId = incoming && incoming.length < 128 ? incoming : crypto.randomUUID();

  req.requestId = requestId;
  res.setHeader('x-request-id', requestId);

  req.log = baseLogger.child({ requestId });
  req.log.info({ req: { method: req.method, path: req.path } }, 'request.start');

  res.on('finish', () => {
    req.log.info(
      { res: { statusCode: res.statusCode }, durationMs: Date.now() - (res.locals._startMs ?? Date.now()) },
      'request.finish'
    );
  });

  res.locals._startMs = Date.now();
  next();
}