SetBaggageItem not working as expected

[andrezszambrano]

Hello. I am encountering the following situation.
My company uses nodejs v20.15.1, and ddtrace v4.17.0. I was asked to include data about the user each time I log information. So if I logger.log('message'), in Datadog the content should also have the request's user information.

To do this, I thought about setting up that data in one of the first spans, and then access that data from the logger.
So basically, I have a middleware like this, that is called before a network request:

export const jwtDatadogHook = (req: any, _res: any, next: NextFunction) => {
const scope = datadog.tracer.scope()?.active();
const ctx: SecurityContext = req.securityContext;

if (scope && ctx) {
  scope.setBaggageItem('user.accountId', ctx.accountId);
}

next();
};

...
router.use(jwtDatadogHook);
...
And then, each time I log when processing the request:

private log(level: 'BIZ' | 'ERROR' | 'WARN' | 'INFO' | 'DEBUG', payload: any, extraPayload?: any) {
const span = datadog.tracer.scope().active();
const timestamp = new Date().toISOString();
const record = {
... this.defaultPayload,
... (typeof payload === 'string' ? { message: payload } : payload),
timestamp,
level
};

if (span) {
  datadog.tracer.inject(span.context(), formats.LOG, record);
  // Add security context data from span baggage items
  const value = span.getBaggageItem('user.accountId');
  if (value !== undefined) {
    record[item] = value;
  }
}
console.log(safeStringify({ ...record, extraPayload }));
}

}

The problem is that the item is always empty. The data is never saved. Even if I add to the baggage items list, and try to get the item right away, I still get empty data.

There are a few clarifications:

1. The reason why I am using setBaggageItem instead of setTag, is that I can actually access the baggage item after using the API. I read this issue (Support iterating over baggage items #2409) and apparently one can also access the items via field span.context()._baggageItems but it tells me there is no such attribute. It seems that its not supported in the version that I have, but that is not good practice in the first place.

2. Another reason is that, setBaggageItem, according to the documentation, actually propagates the data across spans, and with tags that does not happen.