NodeJS Request Log Tracing: Express Middleware

request-tracing-middleware.js

const cls = require('cls-hooked');
const generate = require('nanoid/generate');
const alphaNumeric = '0123456789abcdefghijklmnopqrstuvwxyz';

const requestTracingNamespace = cls.createNamespace('request-tracing');

const middleware = () => {
  return (req, res, next) => {
    requestTracingNamespace.bindEmitter(req);
    requestTracingNamespace.bindEmitter(res);

    const tracingId = req.header('X-Tracing-Id') || generate(alphaNumeric, 10);

    requestTracingNamespace.run(() => {
      requestTracingNamespace.set('tracingId', tracingId);
      next();
    });
  };
};