Data field different format

[piotrkochan]

I've made some change in order to parse "data" field differently.
Right now .info, .warning etc methods accepts multiple arguments and they are collapsed into one string finally.
In this version:

• first argument from .info is passed to data
• all others are passed to additional field "extra" and merged together via Object.assign

[okkez]

Thank you for new feature PR.
But CI is failed. Could you support Node.js 4 to pass CI?

[okkez]

Don't use spread operator.
I want to support Node.js 4 until its EOL (2018-04-30).

[okkez]

Remove this change, please.
I don't want to add IDE specific configuration in this repository.

[piotrkochan]

ok

[piotrkochan]

I've used object.assign polyfill and get rid of spread operator. I've removed .idea from .gitignore.

[okkez]

How do you think about log4js's context API?
logger.info() can accept multiple arguments and format log string using format string like following.

const log4js = require('log4js');

log4js.configure({
  appenders: {
    fluent: {
      type: 'log4js-fluent-appender',
      tag_prefix: 'tag_prefix',
      options: {
        levelTag: true,
        host: 'localhost',
        port: 24224
      }
    }
  },
  categories: {
    default: {
      appenders: ['fluent'],
      level: 'info'
    }
  }
});

const logger = log4js.getLogger();

logger.info('This is info message! %d', 1);
logger.addContext("extra1", "1");
logger.info('This is info message! %d', 2);
logger.addContext("extra2", "2");
logger.info('This is info message! %d', 3);
logger.removeContext("extra1");
logger.info('This is info message! %d', 4);
logger.removeContext("extra2");
logger.info('This is info message! %d', 5);

setTimeout(() => {
  log4js.shutdown(() => {});
}, 1000);

[piotrkochan]

I think context is OK but not for everything. For example if you just want to add request ID to every request then context is nice tool to use. But in other places you just want to log for example user logged event and add some information about what is this user id. So when you add user id to the context then this context is shared between everything else and you need to remove it as you wrote. For me this is unexpected behavior and I'm looking for something more close to the PHP's monolog usage.

So check this example:

const log4js = require('log4js');
const requestLogger = log4js.getLogger('request');

router.get('/', function(req, res, next) {
  requestLogger.addContext('number', 12341234);
  requestLogger.info('test with context');

  res.render('index', { title: 'This log will contain context' });
});

router.get('/test', function(req,res,next) {
  requestLogger.info('test without context');
  
  res.render('index', { title: 'There will be no context in this log' });
});

So if I request / then message "test with context" will be logger together with "number": 12341234 context. But just after that when I'll request /test then logger will log extra data which I don't want.

As I said before, I think that .addContext methods should care about global logger data.

[okkez]

You can remove extra data added by .addContext using .removeContext or .clearContext.

BTW .addContext is log4js API.
So I don't want to add extended API to this library for this purpose.

You can add simple wrapper function for your purpose:

pseudo code (not tested):

const logger = log4js.getLogger('mylogger');

function logWithContext(level, message, context) {
  context.forEach((value, key) => { logger.addContext(key, value)});
  logger.log(level, message);
  logger.clearContext();
}