What's the best practice for expressjs logging

Question

I am building an application based on expressjs and I'd like to log all events in it. I could find winston, which seems to be cool. Anyway, I am looking for a way how to connect it to my expressjs app.

What I also want is logging inside the application. My reqeusts are not so simple, so I'd like to log everything inside my app (not only requests).

My current situation:

server.js (I'd like to log http requests on this level)

var express = require('express');
var app = express();
var fs = require('fs');

// Post parser
app.configure(function(){
    app.use(express.bodyParser());
});

// Load routes
require('fs').readdirSync(__dirname + '/routes').forEach(function(file) {
    require(__dirname + '/routes/' + file)(app);
});

// 404: Not found
app.use(function(req, res, next){
    res.json(404, {ERROR: 'Page not found.'});
});

// 500: Error reporing
app.use(function(err, req, res, next){
    console.error(err.stack);
    res.json(500, {ERROR: 'Internal server error.'} );
});

// Startup new server
app.listen(900);

routes/something.js

var something = require(__dirname + '/../controller/something.js');

module.exports = function(app) {
    app.get('/v1/something', function(req, res, next) { new something().getAll(req, res, next); });
};

controller/something.js (I'd like to use the same logger for debug logging)

/**
 * Constructor
 *
 */
function Something() {
};

/**
 * Get all the data
 *
 */
Something.prototype.getAll = function(req, res, next) {
    // I want to log some very important information here
    res.json({result: true, data: ['hello', 'hi', 'ciao', 'buf']});
}

module.exports = Something;

The other thing I am thinking about is logging all the events in functions that are called from controllers (e.g. models or other libraries).

So I think, the good way might to create some logger library, that will be called using:

var logger = require(__dirname + '/../libraries/logger.js');

containing logger definition. The other issue I don't know how to solve is how to prefix data. You know, I have a lot of concurrent requests and I'd like to see which debug message was called by each request.

Answer 1

If you're using express you may want to look at express-winston package. Then you can use winston as middleware and easily log requests/errors without making your code messy...

Answer 2

I love the following Rails-style logging:

[2017-11-02T11:13:54.545 #07738a81] Started GET /api/url for 10.0.0.1
[2017-11-02T11:13:54.550 #07738a81] Completed 200 31739 in 5.635 ms

The code below does it

addRequestId = require('express-request-id')(setHeader: false)
app.use(addRequestId)

morgan = require('morgan')
morgan.token('id', (req) -> req.id.split('-')[0])

app.use(morgan(
  "[:date[iso] #:id] Started :method :url for :remote-addr",
  immediate: true))

app.use(morgan("
  [:date[iso] #:id] Completed :status :res[content-length] in :response-time ms"))

app.use('/api', router)

Answer 3

We use winston, it's probably the most robust logging package out there.

We ended up setting it up exactly like you suggested. Creating a common library used for wrapping the logger object around our definitions and transports, and then handling any other type of objects we want to be handled differently.

https://gist.github.com/rtgibbons/7354879