Node.js Logging

user_903521 0
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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 ?

node.js libraries logging
10 Answers

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.

user_28089440

Each answer is 5 6 years old, so bit outdated or depreciated.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.

user_126150390

Here is lightweight module for logging data with full stack trace

@grdon/logger

 const logger = require('@grdon/logger')({
   defaultLogDirectory : __dirname + "/logs",
 })
 // ...
logger(someParams, 'logfile.txt')
logger(anotherParams, 'anotherLogFile.log')
user_17467970
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