The Fix
pip install celery==4.4.0rc5
Based on closed celery/celery issue #5643 · 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.
@@ -506,14 +506,18 @@ class: :class:`celery.Task`.
def __call__(self, *args, **kwargs):
print('TASK STARTING: {0.name}[{0.request.id}]'.format(self))
- return super(DebugTask, self).__call__(*args, **kwargs)
+ return self.run(*args, **kwargs)
repro.py
from celery import Task
class DebugTask(Task):
def __call__(self, *args, **kwargs):
print('TASK STARTING: {0.name}[{0.request.id}]'.format(self))
return self.run(*args, **kwargs)
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==4.4.0rc5\nWhen NOT to use: This fix is not applicable if the task's __call__ method is not overridden.\n\n
Why This Fix Works in Production
- Trigger: - [x] I have included all related issues and possible duplicate issues in this issue
- Mechanism: Updated documentation to clarify that when overriding __call__ in a custom Task class, self.run should be called instead of super().__call__.
- Why the fix works: Updated documentation to clarify that when overriding __call__ in a custom Task class, self.run should be called instead of super().__call__. (first fixed release: 4.4.0rc5).
Production impact:
- 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
- Production symptom (often without a traceback): - [x] I have included all related issues and possible duplicate issues in this issue
Proof / Evidence
- GitHub issue: #5643
- Fix PR: https://github.com/celery/celery/pull/5652
- First fixed release: 4.4.0rc5
- Reproduced locally: No (not executed)
- Last verified: 2026-02-09
- Confidence: 0.85
- Did this fix it?: Yes (upstream fix exists)
- Own content ratio: 0.63
Discussion
High-signal excerpts from the issue thread (symptoms, repros, edge-cases).
“Given the following snippets, I believe that the documentation has to be updated to be in line with optimizations made to Celery at some point…”
Failure Signature (Search String)
- - [x] I have included all related issues and possible duplicate issues in this issue
- 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 in this issue
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 in this issue
or possible duplicates to this issue as requested by the checklist above.
Minimal Reproduction
repro.py
from celery import Task
class DebugTask(Task):
def __call__(self, *args, **kwargs):
print('TASK STARTING: {0.name}[{0.request.id}]'.format(self))
return self.run(*args, **kwargs)
What Broke
Tasks fail to re-enqueue properly during retries, leading to TimeoutError.
Fix Options (Details)
Option A — Upgrade to fixed release Safe default (recommended)
pip install celery==4.4.0rc5
When NOT to use: This fix is not applicable if the task's __call__ method is not overridden.
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.
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/5652
First fixed release: 4.4.0rc5
Last verified: 2026-02-09. Validate in your environment.
When NOT to Use This Fix
- This fix is not applicable if the task's __call__ method is not overridden.
- 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.
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 |
|---|---|
| 4.4.0rc5 | Fixed |
Related Issues
No related fixes found.
Sources
We don’t republish the full GitHub discussion text. Use the links above for context.