opentelemetry-instrumentation-celery: normalize Kombu routing span attributes

[EM-Tim]

Description

Kombu routing objects can reach Celery publish signals and be passed directly to span.set_attribute, producing an invalid type warning for celery.exchange. Normalize known Kombu Exchange and Queue values to their .name, and skip names that are empty. Normal string names, valid OpenTelemetry primitives, and homogeneous sequences remain unchanged; unknown objects are not generically stringified.

The custom-routing report is in #1195. Source inspection of Celery 5.6.3 found an additional native delayed-delivery path: it requires quorum queues to be detected, a non-direct selected exchange, and a countdown/ETA that resolves to a positive delay. Under those conditions Celery can construct Exchange("celery_delayed_27", type="topic") and pass it through before_task_publish. This is source-level evidence only; the delayed-delivery trigger has not been reproduced with RabbitMQ or in deployed services.

Related earlier proposals #1196 and #4393 closed without merging. This change uses Kombu public types and avoids generic stringification; thanks to Heatstealer for the earlier work on this issue.

Fixes #1195

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature
• Breaking change
• Documentation update required

How Has This Been Tested?

Local checks on the current single-commit PR head (10d5261):

• uv tool run --from tox tox -e py312-test-instrumentation-celery — 34 passed, 31 dependency/Celery deprecation warnings. This tox environment uses the repository-pinned Celery 5.3.6 and Kombu 5.3.5.
• uv tool run --from tox tox -e lint-instrumentation-celery — pylint 10.00/10.
• Ruff check and Ruff format check passed for all three changed Python files.
• The strengthened empty-name regression test passes and asserts there are no opentelemetry.attributes warnings.
• Public Exchange/Queue imports and .name checks passed with Celery 5.6.3 and Kombu 5.6.2.
• Exchange-value and empty-name regression tests were observed failing before the corresponding fixes; the full package suite passes on this head.

The publish-signal regression dispatches Celery signals locally and does not require RabbitMQ. The native delayed-delivery path has not been reproduced against RabbitMQ or in production. GitHub Actions CI and changelog runs for this head are action_required with no jobs started (CI run, changelog run). The run-approval API requires repository admin rights, which this account does not have. Local test and lint results above are reproducible but are not GitHub-hosted checks. This PR remains a draft and no review was requested.

Does This PR Require a Core Repo Change?

• Yes
• No

Checklist

• Followed the style guidelines
• Changelog fragment added
• Unit tests added
• Documentation updated (not required)

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: EM-Tim / name: EM-Tim (9e716a8, eb38ef4)

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Pull request dashboard status

Waiting on maintainers · refreshed 2026-10-01 16:11 UTC

Merge when ready.

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