How to write logs in a file?

[saeta-eth]

Hi all.

I want to do something like it: https://stackoverflow.com/a/26731285/1741027 But I dont know why it return log4js.loadAppender is not a function

I added in each js file this code: const path = require('path') const log4js = require('log4js') const fileName = path.basename(__filename, path.extname(__filename))

log4js.loadAppender('file') log4js.addAppender(log4js.appenders.file('logs/'+ fileName +'.log'), fileName)

const logger = log4js.getLogger(fileName)

Is there a way to get the same behavior? Thanks.

[nomiddlename]

The stack overflow answer will work fine for version 1.x and older of log4js. Version 2.x has a different API. You can't add appenders programmatically. You'd need to do something like this:

log4js.configure({
  appenders: { 'file': { type: 'file', filename: 'logs/file.log' } },
  categories: { default: { appenders: ['file'], level: 'debug' }
});

If you want to dynamically create files based on properties in the log message (like filename above), then take a look at the multiFile appender.

[saeta-eth]

Really cool! Thanks @nomiddlename

[saeta-eth]

Hi @nomiddlename!

I implemented your suggestion. When I added these lines to 12 files appears the following error:

(node:53001) MaxListenersExceededWarning: Possible EventEmitter memory leak detected. 11 SIGHUP listeners added. Use emitter.setMaxListeners() to increase limit

Do you know what happens?

[nomiddlename]

I'd have to see a sample of the code you're using. Are you calling log4js.configure multiple times? It is only supposed to be called once in an application.

[saeta-eth]

Yes, I called log4js.configure multiple times. If I config the module in my main file, the config is propagated in each js file? I ask it because I have to require the module in each file if I wanna use it or is there any better way?

[nomiddlename]

Yes, you can call configure once in your main file. Then just require it in the other files, without calling configure, and it will use the same configuration.

[saeta-eth]

Cool! Thanks @nomiddlename!!