Node.js Logging

Question

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 ro

Answer 1

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

Answer 2

Observe that errorLogger is a wrapper around logger.trace. But the level of logger is ERROR so logger.trace will not log its message to logger's appenders.

The fix is to change logger.trace to logger.error in the body of errorLogger.

Answer 3

A 'nodejslogger' module can be used for simple logging. It has three levels of logging (INFO, ERROR, DEBUG)

var logger = require('nodejslogger')
logger.init({"file":"output-file", "mode":"DIE"})

D : Debug, I : Info, E : Error

logger.debug("Debug logs")
logger.info("Info logs")
logger.error("Error logs")

The module can be accessed at : https://www.npmjs.com/package/nodejslogger

Answer 4

Each answer is 5 6 years old, so bit outdated or depreciated. Let's talk in 2020.

simple-node-logger is simple multi-level logger for console, file, and rolling file appenders. Features include:

1. levels: trace, debug, info, warn, error and fatal levels (plus all and off)

2. flexible appender/formatters with default to HH:mm:ss.SSS LEVEL message add appenders to send output to console, file, rolling file, etc

3. change log levels on the fly

4. domain and category columns

5. overridable format methods in base appender

6. stats that track counts of all log statements including warn, error, etc

You can easily use it in any nodejs web application:

   // create a stdout console logger
  const log = require('simple-node-logger').createSimpleLogger();

or

  // create a stdout and file logger
  const log = require('simple-node-logger').createSimpleLogger('project.log');

or

  // create a custom timestamp format for log statements
  const SimpleNodeLogger = require('simple-node-logger'),
  opts = {
      logFilePath:'mylogfile.log',
      timestampFormat:'YYYY-MM-DD HH:mm:ss.SSS'
   },
  log = SimpleNodeLogger.createSimpleLogger( opts );

or

  // create a file only file logger
  const log = require('simple-node-logger').createSimpleFileLogger('project.log');

or

  // create a rolling file logger based on date/time that fires process events
  const opts = {
      errorEventName:'error',
       logDirectory:'/mylogfiles', // NOTE: folder must exist and be writable...
        fileNamePattern:'roll-<DATE>.log',
         dateFormat:'YYYY.MM.DD'
  };
  const log = require('simple-node-logger').createRollingFileLogger( opts );

Messages can be logged by

  log.info('this is logged info message')
  log.warn('this is logged warn message')//etc..

PLUS POINT: It can send logs to console or socket. You can also append to log levels.

This is the most effective and easy way to handle logs functionality.

Answer 5

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.

Answer 6

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');