👌 A Koa middleware for logging JSON access logs consistently, similar to morgan

Usage no npm install needed!

<script type="module">
  import uswitchKoaAccess from 'https://cdn.skypack.dev/@uswitch/koa-access';


👌 Koa Access

A Koa middleware for creating consistent, per-request access logs for your requests.

Overview | Usage | Api | Contributors

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This package is a Koa middleware inspired by Morgan, an access log middleware for Express.

It tries to address the following;

  • 🖌 Custom formatting - Allow you to inject your own formatting
  • 💰 Custom tokens - Allow you to add your own extra logging tokens
  • 📓 JSON tokens - All of this is handled using JSON rather than strings

All of this allows you to create consistent access logs decoupled from the actual implementation of your code.


import Koa from 'koa'
import access from 'koa-access'

const app = new Koa()

app.use(access())           /* Default configuration */
app.use(access([ 'id' ]))   /* Add `id` from `ctx.state` to access log */

app.use(access(readContext)) /* Read extra poperties by calling `readContext` on `ctx` */

app.on('koa-access:access', Logger.log)

This package uses Event Emitters to decouple the handling of logging from the implementation of your code.


By default, the koa-access will bundle the following properties into an object and fire them on the the koa-access:access event.

  "res": {
    "responseTime": 23    // Response time in `ms`
    "length": 23232       // Content length of the response
    "status": 200         // Response status
    "statusBucket": "2XX" // Status as a bucket string
    "time": "2017-..."    // Timestamp of the response
  "req": {
    "method": "GET"       // Method of request
    "path": "/foo/bar"    // Path being accessed
    "time": "2017-..."    // Timestamp of request start
    "host": ""   // Host of the request

The koa-access can be configured with extra parameters in one of two ways,

Array - access([ 'id', 'errors' ])

This will add the id and errors properties from the Koa ctx.state object onto the access log object.

Function - access((ctx) => ({ id: ctx.state.id, errors: ctx.state.errors }))

This will return an object by calling the function on Koa's ctx object, in this example, it'll just grab the id and errors properties from the state.


Once a request access log has been built, the following event is fired with the access object

koa-access:access => (ctx, { req, res, ...extras })

The event can be imported from the koa-access module, as

import { eventAccess } from 'koa-access


Thanks goes to these wonderful people (emoji key):

Dom Charlesworth

📖 💻 🤔 🔌

David Annez

💻 🤔 🔌

This project follows the all-contributors specification. Contributions of any kind welcome!