The Fix
pip install celery==5.5.0
Based on closed celery/celery issue #6244 · PR/commit linked
Production note: This usually shows up under retries/timeouts. Treat it as a side-effect risk until you can verify behavior with a canary + real traffic.
@@ -157,7 +157,7 @@ jobs:
Run tox for
"${{ matrix.python-version }}-smoke"
- timeout-minutes: 20
+ timeout-minutes: 30
run: >
repro.py
software -> celery:4.4.6 (cliffs) kombu:4.6.11 py:3.7.6
billiard:3.6.3.0 redis:3.5.3
platform -> system:Darwin arch:64bit
kernel version:19.6.0 imp:CPython
loader -> celery.loaders.app.AppLoader
settings -> transport:redis results:disabled
broker_url: 'redis://h:********@ec2-23-21-96-121.compute-1.amazonaws.com:24849//'
celery_backend_result: 'redis://h:********@ec2-23-21-96-121.compute-1.amazonaws.com:24849/'
task_acks_late: True
task_reject_on_worker_lost: True
task_time_limit: 300
broker_transport_options: {
'visibility_timeout': 3600}
verify
Re-run the minimal reproduction on your broken version, then apply the fix and re-run.
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 immediate termination of tasks without re-queuing.\n\n
Why This Fix Works in Production
- Trigger: - [x] I have included all related issues and possible duplicate issues
- Mechanism: The issue was caused by improper handling of SIGTERM leading to cold shutdown instead of warm shutdown
- Why the fix works: Fixes the issue where REMAP_SIGTERM=SIGQUIT was not functioning correctly by ensuring that a cold shutdown is initiated when SIGTERM is remapped to SIGQUIT. (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
- The issue was caused by improper handling of SIGTERM leading to cold shutdown instead of warm shutdown
- Production symptom (often without a traceback): - [x] I have included all related issues and possible duplicate issues
Proof / Evidence
- GitHub issue: #6244
- Fix PR: https://github.com/celery/celery/pull/9213
- 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: 0.57
Discussion
High-signal excerpts from the issue thread (symptoms, repros, edge-cases).
“> #9213 Adds documentation to REMAP_SIGTERM + smoke tests and also potentially addresses the visibility timeout problem during worker shutdown. Celery v5.5.0b3 released.”
“I might have closed that mistakenly! would you mind come with a PR with a unit test of that code?”
“> Celery's docs indicate that in this situation, tasks won't be lost: You are right that should have been the ideal case”
“Ah, I think I got it. Thanks for your help!”
Failure Signature (Search String)
- - [x] I have included all related issues and possible duplicate issues
- or possible duplicates to this issue as requested by the checklist above.
Copy-friendly signature
signature.txt
Failure Signature
-----------------
- [x] I have included all related issues and possible duplicate issues
or possible duplicates to this issue as requested by the checklist above.
Error Message
Signature-only (no traceback captured)
error.txt
Error Message
-------------
- [x] I have included all related issues and possible duplicate issues
or possible duplicates to this issue as requested by the checklist above.
Minimal Reproduction
repro.py
software -> celery:4.4.6 (cliffs) kombu:4.6.11 py:3.7.6
billiard:3.6.3.0 redis:3.5.3
platform -> system:Darwin arch:64bit
kernel version:19.6.0 imp:CPython
loader -> celery.loaders.app.AppLoader
settings -> transport:redis results:disabled
broker_url: 'redis://h:********@ec2-23-21-96-121.compute-1.amazonaws.com:24849//'
celery_backend_result: 'redis://h:********@ec2-23-21-96-121.compute-1.amazonaws.com:24849/'
task_acks_late: True
task_reject_on_worker_lost: True
task_time_limit: 300
broker_transport_options: {
'visibility_timeout': 3600}
What Broke
Workers were losing unacknowledged tasks during shutdown due to incorrect signal handling.
Why It Broke
The issue was caused by improper handling of SIGTERM leading to cold shutdown instead of warm shutdown
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 immediate termination of tasks without re-queuing.
Use when you can deploy the upstream fix. It is usually lower-risk than long-lived workarounds.
Fix reference: https://github.com/celery/celery/pull/9213
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 immediate termination of tasks without re-queuing.
Verify Fix
verify
Re-run the minimal reproduction on your broken version, then apply the fix and re-run.
Did This Fix Work in Your Case?
Quick signal helps us prioritize which fixes to verify and improve.
Prevention
- Make timeouts explicit and test them (unit + integration) to avoid silent behavior changes.
- Instrument retries (attempt count + reason) and alert on spikes to catch dependency slowdowns.
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.