winston-log-space

Per-module wrapper over a winston v3 logger

Motivation

Winston is a great logger platform, but it lacks abilities to provide different subloggers with different loglevels, as one can find in, for example, log4j

Thus, I decided to see if such a thing would be easy to do on top of the freshly-released winston v3

Structure

winston-log-space (wls henceforth) works in the following way:

• a single winston logger is created; it can have whatever transports as desired, and its format can also be specified. Its level will be set to silly
• a set of shallow, light loggers with the usual 'log()' and 'debug()/verbose()/info()... ' interface are created on demand, using a hierarchical module naming (separator is ':'). Each of this shallow loggers will have its own level and a simple check on it, so they will or will not cal the root winston logger depending on their level
• many aspects such as the associations of loglevels to name hierarchies are configurable via env vars, command line options or even js files

Quick start

Let us have a test.js file:

var Log = require ('winston-log-space');

Log.init ((err) => {
  if (err) return console.error(err)

  l1 = Log.logger ('s1');
  l2 = Log.logger ('s2:s3:s4');

  l1.info    ('this is l1 on info %s, %d', 'ggg', 666);
  l1.verbose ('this is l1 on verbose %s, %d', 'ggg', 666);

  l2.info    ('this is l2 on info %s, %d', 'ggg', 666);
  l2.verbose ('this is l2 on verbose %s, %d', 'ggg', 666);
});

then, running it with various command line options we get:

$ node test.js 
2018-06-27T15:17:09.554Z [s1] info: this is l1 on info ggg, 666
2018-06-27T15:17:09.556Z [s2:s3:s4] info: this is l2 on info ggg, 666

$ node test.js --log__level__s1=debug
2018-06-27T15:17:12.331Z [s1] info: this is l1 on info ggg, 666
2018-06-27T15:17:12.333Z [s1] verbose: this is l1 on verbose ggg, 666
2018-06-27T15:17:12.333Z [s2:s3:s4] info: this is l2 on info ggg, 666

$ node test.js --log__level__s2=debug
2018-06-27T15:17:18.415Z [s1] info: this is l1 on info ggg, 666
2018-06-27T15:17:18.417Z [s2:s3:s4] info: this is l2 on info ggg, 666
2018-06-27T15:17:18.417Z [s2:s3:s4] verbose: this is l2 on verbose ggg, 666

Alternatively, we can use env vars:

$ LOG_level__s1=debug node test.js 
2018-06-27T15:19:39.274Z [s1] info: this is l1 on info ggg, 666
2018-06-27T15:19:39.276Z [s1] verbose: this is l1 on verbose ggg, 666
2018-06-27T15:19:39.277Z [s2:s3:s4] info: this is l2 on info ggg, 666

$ LOG_level__s2=debug node test.js 
2018-06-27T15:20:15.196Z [s1] info: this is l1 on info ggg, 666
2018-06-27T15:20:15.199Z [s2:s3:s4] info: this is l2 on info ggg, 666
2018-06-27T15:20:15.199Z [s2:s3:s4] verbose: this is l2 on verbose ggg, 666

Configuration

All of the configuration magic inside init() is done using cascade-config, using the following config cascade:

• a defaults object
• the opts object passed as first param to init() if any
• env vars, with prefix: LOG_
• args, with prefix: log.
• contents of file process.cwd() + '/log.js'
• contents of file process.cwd() + '/log-{env}.js'
• contents of a file whose name is specified in config as wlsconfig

using init(opts, cb)

As stated, you can inline your confi, or extra defults, by passing them to init():

var Log = require ('../');
var winston = require ('winston');


var config = {
  level: {
    s1: 'silly'
  },
  format: winston.format.combine(
    winston.format.timestamp(),
    winston.format.splat(),
    winston.format.printf(info => `${info.timestamp} | ${info.area} | ${info.level} | ${info.message}`)
  ),
  transports: [
    new winston.transports.Console(),
    new winston.transports.File({filename: 'test.log'})
  ]
};

Log.init (config, (err) => {
  if (err) return console.error(err)
  l1 = Log.logger ('s1');
  l2 = Log.logger ('s2:s3:s4');

  l1.info    ('this is l1 on info %s, %d', 'ggg', 666);
  l1.verbose ('this is l1 on verbose %s, %d', 'ggg', 666);

  l2.info    ('this is l2 on info %s, %d', 'ggg', 666);
  l2.verbose ('this is l2 on verbose %s, %d', 'ggg', 666);
});

This will get you:

$ node inline-config.js 
2018-06-28T06:23:02.817Z | s1 | info | this is l1 on info ggg, 666
2018-06-28T06:23:02.819Z | s1 | verbose | this is l1 on verbose ggg, 666
2018-06-28T06:23:02.820Z | s2:s3:s4 | info | this is l2 on info ggg, 666

$ cat test.log 
2018-06-28T06:23:02.817Z | s1 | info | this is l1 on info ggg, 666
2018-06-28T06:23:02.819Z | s1 | verbose | this is l1 on verbose ggg, 666
2018-06-28T06:23:02.820Z | s2:s3:s4 | info | this is l2 on info ggg, 666

using files

Creating a log.js file in your PWD is also a way:

var winston = require ('winston');

module.exports = {
  level: {
    s1: 'silly'
  },
  format: winston.format.combine(
    winston.format.timestamp(),
    winston.format.splat(),
    winston.format.printf(info => `${info.timestamp} | ${info.area} | ${info.level} | ${info.message}`)
  ),
  transports: [
    new winston.transports.Console(),
    new winston.transports.File({filename: 'test.log'})
  ]
};

so, running your js in the same directory:

$ node basic.js 
2018-06-28T06:25:56.812Z | s1 | info | this is l1 on info ggg, 666
2018-06-28T06:25:56.815Z | s1 | verbose | this is l1 on verbose ggg, 666
2018-06-28T06:25:56.815Z | s2:s3:s4 | info | this is l2 on info ggg, 666

or, passing any file as config

You can also pass any file, not just ./log.js as source for your config; simply specify anywhere in your config sources a key wlsconfig which should contain the filename (as an absolute path). For example, passing it via cli:

$ node basic.js --log__wlsconfig=$PWD/config-log.js
2018-06-28T06:29:15.413Z | s1 | info | this is l1 on info ggg, 666
2018-06-28T06:29:15.415Z | s1 | verbose | this is l1 on verbose ggg, 666
2018-06-28T06:29:15.416Z | s2:s3:s4 | info | this is l2 on info ggg, 666