Propagation: only warn about oversized baggage headers when headers exist

[marier-nico]

Description

Warnings were being logged about the baggage header being too long when the header was not present. This PR just adds a check to make sure the warning is only emitted when the header exists.

The main issue is that this was creating a lot of noise in logs, because the project where opentelemetry is used is the first one to receive requests (and thus will never have the baggage header set).

Type of change

• Bug fix (non-breaking change which fixes an issue)

How Has This Been Tested?

Tox has been run. I'm not sure much else is necessary, given that no behavior has been changed, only logging.

• Run tox

Does This PR Require a Contrib Repo Change?

• Yes. - Link to PR:
• No.

Checklist:

• Followed the style guidelines of this project
• Changelogs have been updated
• Unit tests have been added
• Documentation has been updated

[linux-foundation-easycla]

The committers are authorized under a signed CLA.

• ✅ Nicolas Marier (aaf88ea)

[owais]

Looks weird to check for if not something and then immediate if something but approving :)

[marier-nico]

@owais Yeah, I wasn't sure myself, I tried to go for the smallest change and that was probably not the best idea 😅

Do you think the following would be better?

if not header:
    return context

if len(header) > self._MAX_HEADER_LENGTH:
    _logger.warning(
        "Baggage header `%s` exceeded the maximum number of bytes per baggage-string",
        header,
    )
    return context

[owais]

I feel your snippet is more clear and shows the intent of the function better. I'm fine either way.

[owais]

Please add a changelog entry

[marier-nico]

Should be all fixed! 😄

[owais]

Set to auto-merge once it receives a 2nd approval.

[doogle-oss]

You are the savior Thanks a ton for fixing so early.