The Fix
pip install celery==4.4.1
Based on closed celery/celery issue #5897 · 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.
@@ -102,7 +102,7 @@ def stop(self):
def ensure_started(self):
- if not self.running and not self.isAlive():
+ if not self.running and not self.is_alive():
if self.on_start:
Option A — Upgrade to fixed release\npip install celery==4.4.1\nWhen NOT to use: This fix is not applicable if maintaining compatibility with Python versions prior to 3.9.\n\n
Why This Fix Works in Production
- Trigger: - [ ] I have included all related issues and possible duplicate issues
- Mechanism: Updates the usage of threading.Thread.isAlive to is_alive for compatibility with Python 3.9, fixing issue #5897.
- Why the fix works: Updates the usage of threading.Thread.isAlive to is_alive for compatibility with Python 3.9, fixing issue #5897. (first fixed release: 4.4.1).
- If left unfixed, the same config can fail only in production (env differences), causing startup failures or partial feature outages.
Why This Breaks in Prod
- Shows up under Python 3.9 in real deployments (not just unit tests).
- Production symptom (often without a traceback): - [ ] I have included all related issues and possible duplicate issues
Proof / Evidence
- GitHub issue: #5897
- Fix PR: https://github.com/celery/celery/pull/5898
- First fixed release: 4.4.1
- Reproduced locally: No (not executed)
- Last verified: 2026-02-09
- Confidence: 0.85
- Did this fix it?: Yes (upstream fix exists)
- Own content ratio: 0.67
Discussion
High-signal excerpts from the issue thread (symptoms, repros, edge-cases).
“<!-- Please fill this template entirely and do not erase parts of it. We reserve the right to close without a response bug reports which are incomplete. --> # Checklist <!-- To check an item on the list replace [ ] with [x]. --> - [x] I hav”
Failure Signature (Search String)
- - [ ] I have included all related issues and possible duplicate issues
- `isAlive` was deprecated and removed in Python 3.9 . Celery has the deprecation warning that will become error in Python 3.9 .
Copy-friendly signature
Failure Signature
-----------------
- [ ] I have included all related issues and possible duplicate issues
`isAlive` was deprecated and removed in Python 3.9 . Celery has the deprecation warning that will become error in Python 3.9 .
Error Message
Signature-only (no traceback captured)
Error Message
-------------
- [ ] I have included all related issues and possible duplicate issues
`isAlive` was deprecated and removed in Python 3.9 . Celery has the deprecation warning that will become error in Python 3.9 .
Environment
- Python: 3.9
Fix Options (Details)
Option A — Upgrade to fixed release Safe default (recommended)
pip install celery==4.4.1
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/5898
First fixed release: 4.4.1
Last verified: 2026-02-09. Validate in your environment.
When NOT to Use This Fix
- This fix is not applicable if maintaining compatibility with Python versions prior to 3.9.
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 |
|---|---|
| 4.4.1 | Fixed |
Related Issues
No related fixes found.
Sources
We don’t republish the full GitHub discussion text. Use the links above for context.