Logging in express js to a output file?

Question

What is best way to log my express js webserver? The inbuilt express.logger() just displays logs on screen. Can I also log them into a file in /log folder? Also the current logger automatically logs the request and responses. I need to log some application data into the log files. Can this be done using express.logger?

Regards, Lalith

score 73 · Answer 1 · edited May 02 '23 at 01:35

73

To send the express or connect logs to a file use Node's writeStream. For example to send the express logs to ./myLogFile.log :

open the stream to your file in append mode with :

var logFile = fs.createWriteStream('./myLogFile.log', {flags: 'a'}); //use {flags: 'w'} to open in write mode

then, in your express config use after doing npm install morgan :

import morgan from 'morgan';
import express from 'express'
const app = express();
app.use(morgan('combined', { stream: logFile }));

should also work for connect.logger.

(Note: We have used import statement for declaring variable assuming user may put in their package.json "type": "module")

edited May 02 '23 at 01:35

Clinto_92_Abraham

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answered Jan 26 '12 at 12:36

Did

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ass express.logger *is* connect.logger it indeed does work. :) – zaphod1984 Feb 04 '12 at 15:52
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express.logger is called [morgan](https://github.com/expressjs/morgan) in express v4 – Niels Abildgaard Oct 27 '14 at 12:22
Most middleware (like logger) is no longer bundled with Express and must be installed separately. Please see https://github.com/senchalabs/connect#middleware. We will have to use morgan as third party dependency – Clinto_92_Abraham Apr 27 '23 at 07:20

score 49 · Accepted Answer · edited Nov 16 '13 at 11:45

49

Look at the connect middleware that express extends. The express.logger() is the same as the connect.logger():

http://expressjs.com/api.html#middleware

http://www.senchalabs.org/connect/logger.html

The logger has a stream option that can be set where you want the output to go. By default it sends it to stdout. Also you can specify the log format you want to use.

edited Nov 16 '13 at 11:45

Jeremy Worboys

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answered Mar 31 '11 at 17:21

Chad Williams

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Thanks Chad, This is exactly what I needed. It clearly gives response time for each connection. – Lalith Apr 04 '11 at 23:56
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Thanks, the link should be fixed now. – Chad Williams Oct 09 '13 at 21:41
how do you do it inside a middleware function? I don't have access to `express` object – chovy Nov 17 '13 at 05:19
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Also note that the logger should be placed before the router object in middleware ordering. – tommy chheng Dec 27 '13 at 01:13
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Since [Express 4](https://expressjs.com/en/guide/migrating-4.html), the default express.logger has been replaced by [Morgan](https://github.com/expressjs/morgan) – appleseedexm Jul 24 '17 at 09:45
The first link is not working any more – Andrew Shaban May 03 '23 at 16:44

score 20 · Answer 3 · edited Jun 11 '12 at 09:43

20

You should try winston

var logger = new (winston.Logger)({
  transports: [
    new (winston.transports.Console)(),
    new (winston.transports.File)({ filename: 'somefile.log' })
  ]
});

edited Jun 11 '12 at 09:43

Shahbaz

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answered Mar 30 '11 at 22:43

generalhenry

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But express creates a /log folder. I thought they have built-in logging facility? – Lalith Mar 31 '11 at 06:19
it does, but winston is more built out with async remote logging on top. – generalhenry Mar 31 '11 at 19:22
1

Best option if you need to log to a file and with json input. +1. Tried morgan also but liked winston better. – Lucas Nov 19 '16 at 02:44

score 8 · Answer 4 · answered Mar 24 '14 at 22:03

Use log4js:

var log4js = require('log4js');
log4js.configure({
    appenders: [{type: 'console'},
                {type: 'file', filename: 'express.log', category: 'dev'}]
});

var logger = log4js.getLogger('dev');
logger.setLevel('DEBUG');

app.use(log4js.connectLogger(logger, {level: log4js.levels.DEBUG}));

score 8 · Answer 5 · answered Sep 27 '11 at 15:11

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winston is kinda silly, multi-transport logging == tee(1), or just tail the file and transfer the data off, easy as pie

answered Sep 27 '11 at 15:11

tjholowaychuk

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We're looking at Winston right now. Curious - is there something wrong with Winston's multi-logging approach? (I.e., a good reason we should avoid it?) And any criticisms of using the other features, which seem kind-of-useful prima facie, like meta-data, etc. ? Is there a reason not to use it – Aneil Mallavarapu Apr 11 '12 at 22:55
2

I just went through setting up logging using papertrail for a nodejs app.. i started off using winston to send express accesses through to paper trail, but then I ended up just setting express to use process.stdout and using tee to pipe to a file and logger syslog utility so I could have stdout, stderr stored locally as well as aggregated to papertrail, i found it to be a simpler setup but perhaps will change in the future. – alex.pilon Oct 29 '13 at 21:15

neurosnap · Answer 6 · 2015-04-26T13:11:44.627

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For HTTP request logging: https://github.com/expressjs/morgan#write-logs-to-a-file

var express = require('express')
var fs = require('fs')
var morgan = require('morgan')

var app = express()

// create a write stream (in append mode)
var accessLogStream = fs.createWriteStream(__dirname + '/access.log', {flags: 'a'})

// setup the logger
app.use(morgan('combined', {stream: accessLogStream}))

app.get('/', function (req, res) {
  res.send('hello, world!')
})

edited Apr 26 '15 at 13:11

answered Apr 26 '15 at 12:49

neurosnap

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Wondering if it also takes care of rotating the log files? – Kiarash Zamanifar Jan 12 '21 at 02:26

score 4 · Answer 7 · edited Feb 01 '23 at 08:32

4

You could try cluster http://learnboost.github.io/cluster/ for Node. Use express to build the app, while the cluster takes over the rest of the tasks including logging.

app.use(express.logger()); - in your express apps, ex: app.js
cluster.use(cluster.logger('logs')); - in your cluster server, ex: server.js

edited Feb 01 '23 at 08:32

zr0gravity7

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answered Oct 17 '11 at 04:10

Len Xu

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score 1 · Answer 8 · edited Jan 11 '23 at 16:25

For logging or debugging, Install winston package

npm i winston

Call package in this file

const { createLogger, transports, format } = require('winston');

const logger = createLogger({
  format: format.combine(
    format.timestamp({ format: 'YYYY-MM-DD HH:mm:ss:ms' }),
    format.printf(info => `${info.timestamp} ${info.level}: ${info.message}`)
  ),
  transports: [
    new transports.File({
      filename: './logs/logs.log',
      json: false,
      maxsize: 5242880,
      maxFiles: 5,
    }),
    new transports.Console(),
  ]
});

Write this code where you want to debug, you can call different log like info, warn, error.

logger.info('some info log message');
logger.warn('some warn log message');
logger.error('some error log message');

Logging in express js to a output file?

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