http-request-context

HTTP Request Context

Set and get request-scoped context anywhere.

Requirement

Nodejs version >= 8.2.0

This module uses the newer async_hooks API which is considered Experimental by Nodejs.

Parameter

Parameter configuration must be require before, but normally no config are required.

Name	Description	Default
process.env.HTTP_REQUEST_CONTEXT_INTERVAL	remove expired callstack interval(ms)	10000
process.env.HTTP_REQUEST_CONTEXT_EXPIRE	callstack expire time(ms)	150000

Middleware

• httpRequestContext.middleware Express middleware.
• httpRequestContext.koaMiddleware Koa middleware.

Set Context

• httpRequestContext.set(key, value) Set context anywhere.
• httpRequestContext.set({ key: value }) This is also OK.

Get Context

• httpRequestContext.get(key) Get the [key] attribute of the context.
• httpRequestContext.get() Gets an object containing all context properties.

How to Use

see example here.

Install

npm install http-request-context --save

Express

Init

const httpRequestContext = require('http-request-context')

app.use(httpRequestContext.middleware)

Set Context

const httpRequestContext = require('http-request-context')

// set context by key-value
app.use((req, res, next) => {
  setTimeout(() => {
    httpRequestContext.set('foo', 'bar')
    next()
  }, 100)
})

Get Context

const httpRequestContext = require('http-request-context')

httpRequestContext.get('foo') // 'bar'

Koa

Init

const httpRequestContext = require('http-request-context')

app.use(httpRequestContext.koaMiddleware)

Set Context

const httpRequestContext = require('http-request-context')

// set context by key-value
app.use(async (ctx, next) => {
  await new Promise(resolve => {
    setTimeout(() => {
      httpRequestContext.set('user', 'user')
      resolve()
    }, 300)
  })
  await next()
})

Get Context

const httpRequestContext = require('http-request-context')

httpRequestContext.get('foo') // 'bar'

Tips

MySQL

If you init mysql connect before http server start, you may get context undefined in mysql query callback scope.

googleapis/cloud-trace-nodejs #946

nodejs/node #22360

mysqlConnection.query('SELECT * FROM table', (error, results, fields) => {
  httpRequestContext.get('foo') // undefined
})

You can use util.promisify to avoid it.

util.promisify(mysqlConnection.query).bind(mysqlConnection)('SELECT * FROM table')
  .then((results, fields) => {
    httpRequestContext.get('foo') // 'bar'
  })
  .catch(error => {})