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

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

Answer 2

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...