nodejs-logging-made-right-5.js

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

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()
  const loggerWithTraceId = logger.child({ traceID })

  clsNamespace.run(() => {
    clsNamespace.set('loggerCls', loggerWithTraceId)

    next()
  })
}