Child logger from winston default logger

[bobvanderlinden]

Please tell us about your environment:

• winston version?
  • winston@2
  • winston@3
• node -v outputs: v12.13.0
• Operating System? MacOS
• Language? ES5

What is the problem?

The following is not possible:

const mychildlog = winston.child({ label: 'somelabel' })

While the documentation gives the following 2 statements:

You can create child loggers from existing loggers to pass metadata overrides

See https://github.com/winstonjs/winston#creating-child-loggers

and

The default logger is accessible through the winston module directly. Any method that you could call on an instance of a logger is available on the default logger

See https://github.com/winstonjs/winston#using-the-default-logger

However, it is not possible to call child on winston. This is inconvenient.

My usecase is the following:

const getLogger = function(module) {
    const path = module.filename.split('/').slice(-2).join('/');

    return winston.child({
      label: path
    });
};

So that I can have the module filename in the logs.

The documentation says the following:

What do you expect to happen instead?

I expect the following to work:

const mychildlog = winston.child({ label: 'somelabel' })
mychildlog.info('hello')

[Wernfried]

I guess you are looking for a solution like this:

const logger = createLogger({
   defaultMeta: { mainLabel: 'default label' },
   level: 'info',
   format: combine(
      timestamp({ format: 'YYYY-MM-DD HH:mm:ss.SSS' }),
      printf(({ message, timestamp, level, mainLabel, childLabel }) => {
         return `${timestamp} (${childLabel || mainLabel}) [${level}] -> ${message}`;
      })
   ),
   transports: [
      new transports.Console()
   ],
});

const childLogger = logger.child({ childLabel: 'child label' });

logger.info('the message');
childLogger.info('the child message');

Output

2021-12-17 17:46:07.781 (default label) [info] -> the message
2021-12-17 17:46:07.784 (child label) [info] -> the child message

Note, you cannot overwrite defaultMeta: { mainLabel: 'default label' }, (at least I did not manage it) thus you have to work with different variables.

[wbt]

This looks related to PR #1989, regarding the overwriting with the same variables.

[maverick1872]

@bobvanderlinden @wbt Per the issue author they wanted to be able to create a new child logger from the default logger instance that is exported. It appears that this was solved by #1603. As such I am closing this issue.

@DABH do you know if we've cut a release and published it to NPM, that has this feature in it? If you don't know off the top of your head, that's fine and I'll confirm later.

[DABH]

Yeah, we have done a release since then, so this must be included now