log4js for Node doesn't output to file, only to console

Question

I need a basic logging system for a NodeJS application, so I'm doing some tests with log4js , which seems to be the standard for these cases. I need to print the messages both to the console and a file, so I wrote this code:

// Logger
var log4js = require('log4js');

log4js.configure({
  appenders: {
    'console': { type: 'console' },
    'file': { type: 'file', filename: 'logs/mailer.log' }
  },
  categories: {
    default: { appenders: ['file', 'console'], level: 'DEBUG' },
  }
});

var logger = log4js.getLogger("Mailer");

logger.info("Starting application");

try {
  // CODE TO READ APP CONFIG FILE
}
catch(e) {
  logger.error("Couldn't read app configuration file (config.yml)");

  // This is the trouble maker. It kills the app without flushing the logs
  process.exit(1);
}

When I run the application, the logs appear like this:

[2019-07-29T16:07:24.763] [INFO] Mailer - Starting application

The problem is that I can see the messages in the console, but the log file remains empty. If I delete it and run the application again, it's created, so I suppose that the problem is a missing option or something like that.

Any suggestion?

Answer 1

To avoid changing the application logic and all the process.exit() calls, I've replaced the file appender by its synchronous version fileSync and now everything works as expected. So, the only thing I changed is the line where I declare the 'file' appender:

    'file': { type: 'fileSync', filename: 'logs/mailer.log' }

Cheers!

Answer 2

You could use loggerWinston...I used it in my nodejs application and it works fine.
You should add it in your server.js (the file you use to start node)

const winston = require('winston');

const tsFormat = () => (new Date()).toLocaleTimeString();
global.loggerWinston = new (winston.Logger)({
  transports: [
    // colorize the output to the console
    new (winston.transports.Console)({
      timestamp: tsFormat,
      colorize: true,
      level: 'debug'
    }),
    new (winston.transports.File)({
      filename: 'results.log',
      timestamp: tsFormat,
//      level: (process.env.NODE_ENV || 'development') === 'development' ? 'debug' : 'info'
      level: 'info'
    })
  ]
});

The results.log file should be added in your project folder.

This is the reference https://www.npmjs.com/package/winston