Logging with Winston

We will now add logging to our application using Winston; let's install Winston:

npm install winston --save

The 404 middleware will need to log 404 not found, so let's create a simple logger module, ./lib/logger/index.js; the details of our logger will be configured with Nconf. We import Winston and the configuration modules. We define our Logger function, which constructs and returns a file logger—winston.transports.File—that we configure using values from our config. We default the loggers maximum size to 1 MB, with a maximum of three rotating files. We instantiate the Logger function, returning it as a singleton.

var winston = require('winston')
 , config = require('../configuration');

function Logger(){
  return winston.add(winston.transports.File, {
    filename: config.get('logger:filename'),
    maxsize: 1048576,
    maxFiles: 3,
    level: config.get('logger:level')
  });
}

module.exports = new Logger();

Let's add the Logger configuration details to our config files ./config/development.json and ./config/test.json:

{
  "express": {
    "port": 3000
  },
  "logger" : {
    "filename": "logs/run.log",
    "level": "silly",
  }
}

Let's alter the ./lib/middleware/notFound.js middleware to log errors. We import our logger and log an error message via logger when a 404 Not Found response is thrown:

var logger = require("../logger");

exports.index = function(req, res, next){
  logger.error('Not Found');
  res.json(404, 'Not Found');
};