Node.js Logging

Is there any library which will help me to handle logging in my Node.Js application? All I want to do is, I want to write all logs into a File and also I need an options like rolling out the file after certain size or date.

I have incorporated log4js im trying to keep all the configuration details in one file and use only the methods in other application files for ease of maintenance. But it doesnt work as expected. Here is what I'm trying to do

var log4js = require('log4js'); 
log4js.clearAppenders()
log4js.loadAppender('file');
log4js.addAppender(log4js.appenders.file('test.log'), 'test');
var logger = log4js.getLogger('test');
logger.setLevel('ERROR');


var traceLogger = function (message) {
        logger.trace('message');
    };

var errorLogger = function (message) {
        logger.trace(message);
    };


exports.trace = traceLogger;
exports.error = errorLogger;

I have included this file in other files and tried

log.error ("Hello Error Message");

But it is not working. Is there anything wrong in this ?

Winston is a pretty good logging library. You can write logs out to a file using it.

Code would look something like:

var winston = require('winston');

var logger = new (winston.Logger)({
  transports: [
    new (winston.transports.Console)({ json: false, timestamp: true }),
    new winston.transports.File({ filename: __dirname + '/debug.log', json: false })
  ],
  exceptionHandlers: [
    new (winston.transports.Console)({ json: false, timestamp: true }),
    new winston.transports.File({ filename: __dirname + '/exceptions.log', json: false })
  ],
  exitOnError: false
});

module.exports = logger;

You can then use this like:

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

logger.info('log to file');

Scribe.JS Lightweight Logger

I have looked through many loggers, and I wasn't able to find a lightweight solution - so I decided to make a simple solution that is posted on github.

  • Saves the file which are organized by user, date, and level
  • Gives you a pretty output (we all love that)
  • Easy-to-use HTML interface

I hope this helps you out.

Online Demo

http://bluejamesbond.github.io/Scribe.js/

Secure Web Access to Logs

A

Prints Pretty Text to Console Too!

A

Web-based Log Explorer

A

Github

https://github.com/bluejamesbond/Scribe.js

Log4js is one of the most popular logging library for nodejs application.

It supports many cool features:

  1. coloured console logging
  2. replacement of node's console.log functions (optional)
  3. file appender, with log rolling based on file size
  4. SMTP appender
  5. GELF appender
  6. hook.io appender
  7. Loggly appender
  8. multiprocess appender (useful when you've got worker processes)
  9. a logger for connect/express servers
  10. configurable log message layout/patterns
  11. different log levels for different log categories (make some parts of your app log as DEBUG, others only ERRORS, etc.)

Example:

  1. Configuration file:

    {"appenders": [
    {
        "type": "console",
        "layout": {
            "type": "pattern",
            "pattern": "%m"
        },
        "category": "app"
    },{
        "category": "test-file-appender",
        "type": "file",
        "filename": "log_file.log",
        "maxLogSize": 10240,
        "backups": 3,
        "layout": {
            "type": "pattern",
            "pattern": "%d{dd/MM hh:mm} %-5p %m"
        }
    }
],
"replaceConsole": true }

  2. Configure and use 

    var log4js = require( "log4js" );
log4js.configure( "./config/log4js.json" );
var logger = log4js.getLogger( "test-file-appender" );
// log4js.getLogger("app") will return logger that prints log to the console
logger.debug("Hello log4js");// store log in file

You can also use npmlog by issacs, recommended in https://npmjs.org/doc/coding-style.html.

You can find this module here https://github.com/isaacs/npmlog

Is this what you are looking for ?

http://nodejs.org/api/all.html#all_util_log_string

The "logger.setLevel('ERROR');" is causing the problem. I do not understand why, but when I set it to anything other than "ALL", nothing gets printed in the file. I poked around a little bit and modified your code. It is working fine for me. I created two files.

logger.js

var log4js = require('log4js');
log4js.clearAppenders()
log4js.loadAppender('file');
log4js.addAppender(log4js.appenders.file('test.log'), 'test');
var logger = log4js.getLogger('test');
logger.setLevel('ERROR');

var getLogger = function() {
   return logger;
};

exports.logger = getLogger();

logger.test.js

var logger = require('./logger.js')

var log = logger.logger;

log.error("ERROR message");
log.trace("TRACE message");

When I run "node logger.test.js", I see only "ERROR message" in test.log file. If I change the level to "TRACE" then both lines are printed on test.log.