Celery 5.6.3 removes deprecated redis get_connection args — verify Scout instrumentation

[mitchh456]

Background

Celery 5.6.3 was released on March 26, 2026. This substantial patch release includes 30+ changes, most notably:

• Removed deprecated arguments from redis get_connection call (#10036) — previously deprecated keyword arguments have been removed.
• Fixed Django worker recursion bug with defensive checks for pool_cls.__module__ (#10048).
• Fixed worker reconnection after Redis failover (#10151).
• Fixed O(K^2) message bloat in chain of chords (#10171) — performance improvement for complex task workflows.
• Fixed warm shutdown RuntimeError with eventlet>=0.37.0 (#10123).

Impact

Scout's Celery instrumentation may be affected by:

1. Removed deprecated redis get_connection args — If Scout's instrumentation touches Celery's redis connection handling (e.g., for result backend monitoring or broker interaction tracing), the removal of deprecated arguments could cause TypeError exceptions at runtime.
2. Worker pool behavior changes — The Django worker recursion fix and pool module checks alter worker startup behavior, which could affect how Scout attaches instrumentation during worker initialization.

Suggested Action

1. Check whether Scout's Celery instrumentation calls or wraps get_connection on redis backends. If so, verify the call signature is compatible with the updated code in #10036.
2. Run the Scout Python agent test suite against Celery 5.6.3 with both redis and non-redis backends.
3. Verify worker startup instrumentation works correctly with the updated pool initialization logic.
4. Update version constraints to include Celery 5.6.3 if compatible.

References

• Celery 5.6.3 release
• Remove deprecated redis get_connection args (#10036)
• Fix worker reconnection after Redis failover (#10151)