Winston does not log events in productions version of Node.js app hosted on Google Cloud Compute Engine

I am using winston to log some events in my application. When I run my code from node app.js

locally, winston logs events just fine. But when I push my code to the server ( gcloud preview app deploy app.yaml

), or even run it in the production environment locally ( gcloud preview app run app.yaml

), it doesn't log any event. Locally winston creates general.log

and request.log

and edits them as needed, but in production mode it doesn't work.

Here is my logging.js code

"use strict";

var fs = require('fs');
var path = require('path');
var winston = require('winston');
var expressWinston = require('express-winston');


module.exports = function(logPath) {

  // Create logging directory if necessary.
  if (!fs.existsSync(logPath)) {
    fs.mkdirSync(logPath);
  }


  /*
    Logger to capture all requests and output them to the console
    as well as request.log.
  */
  // [START requests]
  var requestLogger = expressWinston.logger({
    transports: [
      new winston.transports.Console({
        json: false
      }),
      new winston.transports.File({
        filename: path.join(logPath, 'request.log'),
      })
    ],
    expressFormat: true
  });
  // [END requests]


  /*
    Logger to capture any top-level errors from requests and
    output them in error.log
  */
  // [START errors]
  var errorLogger = expressWinston.errorLogger({
    transports: [
      new winston.transports.Console({
        json: false
      }),
      new winston.transports.File({
        filename: path.join(logPath, 'error.log'),
      })
    ]
  });
  // [END errors]


  /*
    General logger used for .log, .info, etc. Outputs all logs
    to the console as well as general.log.
  */
  // [START general]
  winston.add(winston.transports.File, {
    filename: path.join(logPath, 'general.log')
  });
  // [END general]


  return {
    requestLogger: requestLogger,
    errorLogger: errorLogger,
    error: winston.error,
    warn: winston.warn,
    info: winston.info,
    log: winston.log,
    verbose: winston.verbose,
    debug: winston.debug,
    silly: winston.silly
  };

};

      

        
        
        
      

    

Here is an example (unimportant) event that I log for testing purposes in app.js

var logging = require('./lib/logging')(process.env.LOG_PATH || './');
app.use(logging.requestLogger);
app.use(logging.errorLogger);
logging.info("Sample test log");

      

        
        
        
      

    

Why doesn't this code work in production mode?

PS I followed the below steps to set up this code

https://cloud.google.com/nodejs/getting-started/logging-application-events