How to manage Log and rotate-file in Nodejs

Why log and log rotate?

Log is a file that records either events that occur in an application or messages between different users of a communication.

Benefits

• For better debugging and find the problems.
• For better application management. 
• For security reason to tracking an application behaviors. 

How we can achieve these above points in Nodesjs 

Step 1-  Require a npm modules - winston and winston-daily-rotate-file

• npm i winsto

• npm i winston-daily-rotate-file

Step 2-  Create a logger configuration JavaScript (.js) file and add below code inside created file. I have created logger.js file.
logger.js : 

var winston = require('winston');

require('winston-daily-rotate-file');
  
  var transport = new winston.transports.DailyRotateFile({
    filename: './log',                            // Log file name  and location 
    datePattern: 'yyyy-MM-ddTHH.',  // Log rotate duration is hourly basis
    prepend: true,
    level: process.env.ENV == 'development' ? 'info' : 'debug'  //As per requirement - local server or production 
  });
  
  var logger = new (winston.Logger)({
    transports: [
      transport
    ]
  });

module.exports = logger;  //Export it as module

Step 3- We have created a module called logger. Now we need to include it on our app.js or server.js (Enter point of Node server where we include all other dependency)

i.e - app.js (I have created a app.js file as entry file in node run environment)

global.logger = require('logger'); //Include a Export Module 

logger.info('Hello World!');         // set logger for information - same as console.log() function 

logger.debug('Hello World!');     // set logger for debug purpose  - log and debug as per your requirement  

Step 4- Run your application - node app.js

It creates file on hourly basis. In our case it created file 2017-01-27T11.log file in parallel of app.js file.

content of 2017-01-27T11.log file is : 

{"level":"info","message":"Hello World!","timestamp":"2017-01-27T11:43:22.529Z"}
{"level":"debug","message":"Hello World!","timestamp":"2017-01-27T11:43:22.570Z"}

- It will create new log file as hourly basis.
i.e  2017-01-27T11.log 
     2017-01-27T12.log

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