How to set log level in Winston/Node.js

Question

I am using Winston logging with my Node.js app and have defined a file transport. Throughout my code, I log using either logger.error, logger.warn, or

Answer 1

If you are using the default logger, you can adjust the log levels like this:

const winston = require('winston');
// ...
winston.level = 'debug';

will set the log level to 'debug'. (Tested with winston 0.7.3, default logger is still around in 3.2.1).

However, the documentation recommends creating a new logger with the appropriate log levels and then using that logger:

const myLogger = winston.createLogger({
  level: 'debug'
});
myLogger.debug('hello world');

If you are already using the default logger in your code base this may require you to replace all usages with this new logger that you are using:

const winston = require('winston');
// default logger
winston.log('debug', 'default logger being used');

// custom logger
myLogger.log('debug', 'custom logger being used');

Answer 2

Looks like there is a level option in the options passed covered here

From that doc:

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

Now, those examples show passing level in the option object to the console transport. When you use a file transport, I believe you would pass an options object that not only contains the filepath but also the level.

That should lead to something like:

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

Per that doc, note also that as of 2.0, it exposes a setLevel method to change at runtime. Look in the Using Log Levels section of that doc.