The Fix
pip install celery==5.5.0
Based on closed celery/celery issue #9149 · PR/commit linked
@@ -249,9 +249,13 @@ def Queues(self, queues, create_missing=None,
max_priority = conf.task_queue_max_priority
if not queues and conf.task_default_queue:
+ queue_arguments = None
+ if conf.task_default_queue_type == 'quorum':
+ queue_arguments = {'x-queue-type': 'quorum'}
fix.md
Option A — Upgrade to fixed release\npip install celery==5.5.0\nWhen NOT to use: Do not use this fix if you require full ETA support for quorum queues.\n\n
Why This Fix Works in Production
- Trigger: For more details see the PR changes.
- Mechanism: Quorum queues were not properly handling ETA tasks, causing potential task loss
- Why the fix works: Added support for Quorum Queues, including feature flags for queue type and detection. (first fixed release: 5.5.0).
Production impact:
- If left unfixed, this can cause silent data inconsistencies that propagate (bad cache entries, incorrect downstream decisions).
Why This Breaks in Prod
- Quorum queues were not properly handling ETA tasks, causing potential task loss
- Production symptom (often without a traceback): For more details see the PR changes.
Proof / Evidence
- GitHub issue: #9149
- Fix PR: https://github.com/celery/celery/pull/9121
- First fixed release: 5.5.0
- Reproduced locally: No (not executed)
- Last verified: 2026-02-09
- Confidence: 0.85
- Did this fix it?: Yes (upstream fix exists)
- Own content ratio: 0.66
Discussion
High-signal excerpts from the issue thread (symptoms, repros, edge-cases).
“@Nusnus hope you don't mind, but I figured I'd open a follow up issue for improving the ETA support based on the findings from the…”
“I do not, but we have a bunch of ETA / countdown tasks in our code base, so wanted to make sure there was a…”
“@Nusnus What was the resolution here? I guess the relation implementation is updated but the issue doesn't have a PR attached. Can we attach the…”
“> @Nusnus hope you don't mind, but I figured I'd open a follow up issue for improving the ETA support based on the findings from…”
Failure Signature (Search String)
- For more details see the PR changes.
- It includes proper documentation for these flags, a new example project and 100% test coverage, so it should be clear what was changed from all angles.
Copy-friendly signature
signature.txt
Failure Signature
-----------------
For more details see the PR changes.
It includes proper documentation for these flags, a new example project and 100% test coverage, so it should be clear what was changed from all angles.
Error Message
Signature-only (no traceback captured)
error.txt
Error Message
-------------
For more details see the PR changes.
It includes proper documentation for these flags, a new example project and 100% test coverage, so it should be clear what was changed from all angles.
What Broke
Tasks could be lost in a RabbitMQ cluster using quorum queues without proper configuration.
Why It Broke
Quorum queues were not properly handling ETA tasks, causing potential task loss
Fix Options (Details)
Option A — Upgrade to fixed release Safe default (recommended)
pip install celery==5.5.0
When NOT to use: Do not use this fix if you require full ETA support for quorum queues.
Use when you can deploy the upstream fix. It is usually lower-risk than long-lived workarounds.
Option D — Guard side-effects with OnceOnly Guardrail for side-effects
Mitigate duplicate external side-effects under retries/timeouts/agent loops by gating the operation before calling external systems.
- Place OnceOnly between your code/agent and real side-effects (Stripe, emails, CRM, APIs).
- Use a stable key per side-effect (e.g., customer_id + action + idempotency_key).
- Fail-safe: configure fail-open vs fail-closed based on blast radius and spend risk.
- This does NOT fix data corruption; it only prevents duplicate side-effects.
Show example snippet (optional)
onceonly.py
from onceonly import OnceOnly
import os
once = OnceOnly(api_key=os.environ["ONCEONLY_API_KEY"], fail_open=True)
# Stable idempotency key per real side-effect.
# Use a request id / job id / webhook delivery id / Stripe event id, etc.
event_id = "evt_..." # replace
key = f"stripe:webhook:{event_id}"
res = once.check_lock(key=key, ttl=3600)
if res.duplicate:
return {"status": "already_processed"}
# Safe to execute the side-effect exactly once.
handle_event(event_id)
When NOT to use: Do not use this to hide logic bugs or data corruption. Use it to block duplicate external side-effects and enforce tool permissions/spend caps.
Fix reference: https://github.com/celery/celery/pull/9121
First fixed release: 5.5.0
Last verified: 2026-02-09. Validate in your environment.
When NOT to Use This Fix
- Do not use this fix if you require full ETA support for quorum queues.
- Do not use this to hide logic bugs or data corruption. Use it to block duplicate external side-effects and enforce tool permissions/spend caps.
Did This Fix Work in Your Case?
Quick signal helps us prioritize which fixes to verify and improve.
Prevention
- Capture the exact failing error string in logs and tests so you can reproduce via a minimal script.
- Pin production dependencies and upgrade only with a reproducible test that hits the failing path.
Version Compatibility Table
| Version | Status |
|---|---|
| 5.5.0 | Fixed |
Related Issues
No related fixes found.
Sources
We don’t republish the full GitHub discussion text. Use the links above for context.