nodejs-logging-made-right-1.js

const cls = require('cls-hooked')
const uuidv4 = require('uuid/v4')

const clsNamespace = cls.createNamespace('app')

const clsMiddleware = (req, res, next) => {
  // req and res are event emitters. We want to access CLS context inside of their event callbacks
  clsNamespace.bind(req)
  clsNamespace.bind(res)

  const traceID = uuidv4()

  clsNamespace.run(() => {
    clsNamespace.set('traceID', traceID)

    next()
  })
}