Child Logger Doesn't Override Parent Metadata

[mplover]

Please tell us about your environment:

• winston version?
  • winston@2
  • winston@3
• node -v outputs: v13.13.0
• Operating System? Linux
• Language? TypeScript 3.8

What is the problem?

The documentation states:

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

But the metadata specified in defaultMeta in createLogger is not overridden.

What do you expect to happen instead?

I expect the metadata (options) provided to the child logger to override the defaultMeta provided in an upstream logger

Other information

Looking at the Logger class (logger.js; Line 58), the write method overridden by the child uses Object.assign() to merge the info and child metadata objects, but they appear to be in the wrong order.

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/assign#Merging_objects_with_same_properties

defaultRequestMetadata should come after info in the sources list to allow for child metadata to override the parent logger's metadata.

[NtsDK]

I also want to use child loggers to get more log control. And got this problem too.
I use such workaround. Maybe it will be useful for somebody.

function customChild(logger, defaultMeta) {
  const childLogger = logger.child();
  childLogger.defaultMeta = { ...logger.defaultMeta, ...defaultMeta };
  childLogger.customChild = customChild;
  return childLogger;
}

winstonLogger.customChild = customChild;

Also documentation about child loggers is poor. It has no example of using defaultMeta usage in log messages and there is no child logger examples in examples folder.

[jrasm91]

I am having this same problem. Is there a reason why this hasn't been fixed already? Seems like a very simple PR to swap the order of requestDefaultMetadata and info.

https://github.com/winstonjs/winston/blob/master/lib/winston/logger.js#L52-L53

[maverick1872]

Closing as this issue is being consolidated into #2029