Node.js Winston logger wrapper to display filename

index.js

var log = require('./lib/logger')(module);

log.info('foo');

logger.js

var winston = require('winston');

var getLogger = function(module) {
    var path = module.filename.split('/').slice(-2).join('/');

    return new winston.Logger({
        transports: [
            new winston.transports.Console({
                colorize: true,
                level: 'debug',
                label: path
            }),
            new (winston.transports.File)({filename: 'debug.log', silent: false})
        ]
    });
};

module.exports = getLogger;

Thanks!! 👍

If we require to import getLogger in lot of files then this will create lot of winston logger instance which will create a problem

Problems like this => (node:13236) MaxListenersExceededWarning: Possible EventEmitter memory leak detected. 31 unpipe listeners added to [Console]. Use emitter.setMaxListeners() to increase limit

I think I found a somewhat good solution/middleway to just being able to print informative stuff with winston, without having to manually specify, where the message came from.
Please test it out, following these steps:

1. Prepare server class in file server.js:

const winston = require('winston');
const Log2gelf = require('winston-log2gelf');
const getCurrentLine = require('get-current-line').default;

// PREPARE CONSTANTS:
// From Log2gelf (index.js) (since I use graylog as transport too):
const WINSTON_LEVELS = {
  error: 0,
  warn: 1,
  info: 2,
  verbose: 3,
  debug: 4,
  silly: 5
};

// SEE: https://github.com/Buzut/winston-log2gelf#protocol-specific-options
const glTransportOpts = {
  level: 'silly',
  name: 'Graylog',
  hostname: process.env.MY_IP, // custom to my setup
  host: process.env.GL_HOST,
  port: 12201,
  protocol: 'tcp', // only with Log2gelf (winston-log2gelf)
  silent: false,
  handleExceptions: true,
  exitOnError: false,
  reconnect: -1,
  wait: 2000,
  service: process.env.API_CONTAINER || 'node-api',
  release: process.env.MAX_VERSION || '0.0.0',
  environment: process.env.ENV || 'development',
};
const glTransport = new Log2gelf(glTransportOpts);

class SERVER {
  constructor() {
    // SETUP LOGGING
    this._logger = winston.createLogger({
      levels: WINSTON_LEVELS,
      exitOnError: false,
      transports: [
        new winston.transports.Console({
          format: winston.format.json(),
          level: 'silly',
        }),
        ...(process.env.GL_HOST ? glTransport : []),
      ],
    });

    this.logger = {}
    this.logger.prepareLog = function () {
      let newArguments = arguments;
      // newArguments: { "0": <message>, ("1": <details>) }
      let msg_location = getCurrentLine({ frames: 3 });
      if (newArguments["1"]) {
        newArguments["1"].msg_location = msg_location;
      } else {
        // https://microsoft.github.io/PowerBI-JavaScript/interfaces/_node_modules_typedoc_node_modules_typescript_lib_lib_es5_d_.iarguments.html
        newArguments["1"] = { "msg_location": msg_location };
        newArguments.length = 2;
      }
      return newArguments;
    };
    Object.keys(WINSTON_LEVELS).forEach(level => {
      this.logger[level] = function () { this._logger[level](...this.logger.prepareLog(...arguments)) }.bind(this)
    });
  }
}

this.server = new SERVER();
// Used like this (from basically anywhere, where this.server is an instance of class SERVER):
this.server.logger.info("Test-Message");
// SHOULD PRINT:
/*
{
  "level": "info",
  "message": "Test-Message",
  "msg_location": {
    "char": 20,
    "file": "[redacted]/test.js",
    "line": 73,
    "method": "Object.<anonymous>"
  }
}
*/
this.server.logger.info("Test-Message", { "withadditionalinfo": "Here is more info about the message" });
// SHOULD PRINT:
/*
{
  "level": "info",
  "message": "Test-Message",
  "msg_location": {
    "char": 20,
    "file": "[redacted]/test.js",
    "line": 87,
    "method": "Object.<anonymous>"
  },
  "withadditionalinfo": "Here is more info about the message"
}
*/

2. In a different file (e.g. utils/Test.js):

class Test {
  constructor(server) {
    this.server = server;
  }

  testlog(){
    this.server.logger.error("Testerror...can you find me? :)")
  }
}

module.exports = Test;

3. add test to server.js:

// [...] (see above)
const Test = require('./utils/Test.js')

let testinstance = new Test(this.server);
testinstance.testlog();
// SHOULD PRINT:
/*
{
  "level": "error",
  "message": "Testerror...can you find me? :)",
  "msg_location": {
    "char": 24,
    "file": "[redacted]/utils/Test.js",
    "line": 7,
    "method": "Test.testlog"
  }
}
*/

4. run node server.js to see the result. Please let me know, if there is anything off.

You can also omit printing the char (for me at least it does not contain information I would want or need in my graylog-logs) with an instant anonymous function call and javacsript object deconstruction:

// [...]
    newArguments[1].msg_location = (({ method, file, line }) => ({ method, file, line }))(getCurrentLine({ frames: 3 }));
// [...]

But this is of course up to you.