How to use Winston in several modules?

Question

I have several modules - let\'s say server.js, module1.js,...,moduleN.js.

I would like define the log file in my server.js:

winston.add(winston.trans         


        

Answer 1

Here is my logger configuration with winston version is 3.2.1.

It storing logs in application.log file and for error stack trace I am using errors({ stack: true }) and small trick in printf function to print stack trace in error case.

Configuration

const {format, transports} = require('winston');
const { timestamp, colorize, printf, errors } = format;
const { Console, File } = transports;
LoggerConfig = {
        level: process.env.LOGGER_LEVEL || 'debug',
        transports: [
            new Console(),
            new File({filename: 'application.log'})
        ],
        format: format.combine(
            errors({ stack: true }),
            timestamp(),
            colorize(),
            printf(({ level, message, timestamp, stack }) => {
                if (stack) {
                    // print log trace 
                    return `${timestamp} ${level}: ${message} - ${stack}`;
                }
                return `${timestamp} ${level}: ${message}`;
            }),
        ),
        expressFormat: true, // Use the default Express/morgan request formatting
        colorize: false, // Color the text and status code, using the Express/morgan color palette (text: gray, status: default green, 3XX cyan, 4XX yellow, 5XX red).
        ignoreRoute: function (req, res) {
            return false;
        } // optional: allows to skip some log messages based on request and/or response
}

Declare

I am using this same configuration in express-winston and for general log also. I declared __logger object globally so that you don't need to import every time in every file. Generally in node js all the global variable prefix with 2 time underscore(__) so it will be good to follow this.

Server.js

const winston = require('winston');
const expressWinston = require('express-winston');

/**
 * winston.Logger
 * logger for specified log message like console.log
 */
global.__logger = winston.createLogger(LoggerConfig);
/**
 * logger for every HTTP request comes to app
 */
app.use(expressWinston.logger(LoggerConfig));

Use

__logger is global so you can use it any place, for example:

blog.controller.js

function save(req, res) {
  try {
    __logger.debug('Blog add operation');
    .
    .
    return res.send(blog);
  } catch (error) {
    __logger.error(error);
    return res.status(500).send(error);
  }
}

Hope this will help !