Celery Multiple Database Connections Django [Question] (Fix)

The Fix

pip install celery==4.4.0rc5

Based on closed celery/celery issue #6062 · 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.

Jump to Verify Open PR/Commit

@@ -183,7 +183,7 @@ def close_database(self, **kwargs):
         for conn in self._db.connections.all():
             try:
-                conn.close()
+                conn.close_if_unusable_or_obsolete()
             except self.interface_errors:

repro

this bug

verify

Follow the reproduction steps, confirm the failure, apply the fix, and repeat the same steps to verify the behavior changes.

fix.md

Option A — Upgrade to fixed release\npip install celery==4.4.0rc5\nWhen NOT to use: This fix is not suitable if your application does not use Django or does not require connection reuse.\n\n

Why This Fix Works in Production

Trigger: - [ ] I have included all related issues and possible duplicate issues
Mechanism: Celery does not re-use database connections with Django when `CONN_MAX_AGE` is set, causing high database load
Why the fix works: Fixes the issue of Celery not re-using database connections with Django when the setting `CONN_MAX_AGE` is set, leading to high database load. (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

Celery does not re-use database connections with Django when `CONN_MAX_AGE` is set, causing high database load
Production symptom (often without a traceback): - [ ] I have included all related issues and possible duplicate issues

Proof / Evidence

GitHub issue: #6062
Fix PR: https://github.com/celery/celery/pull/4292
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: 0.79

Discussion

High-signal excerpts from the issue thread (symptoms, repros, edge-cases).

Jump to Sources Open on GitHub

“# Checklist - [x] I have verified that the issue exists against the master branch of Celery. - [ ] This has already been asked to the discussion group first. - [x] I have read the relevant section in the contribution guide on reporting bugs”

Issue thread · issue description · source

Failure Signature (Search String)

- [ ] I have included all related issues and possible duplicate issues
https://github.com/celery/celery/pull/4292

Copy-friendly signature

signature.txt

Failure Signature
-----------------
- [ ] I have included all related issues and possible duplicate issues
https://github.com/celery/celery/pull/4292

Error Message

Signature-only (no traceback captured)

error.txt

Error Message
-------------
- [ ] I have included all related issues and possible duplicate issues
https://github.com/celery/celery/pull/4292

Minimal Reproduction

this bug

What Broke

High database load and degraded query performance due to immediate closure of connections.

Why It Broke

Celery does not re-use database connections with Django when `CONN_MAX_AGE` is set, causing high database load

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 suitable if your application does not use Django or does not require connection reuse.

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)

See OnceOnly SDK

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/4292

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 suitable if your application does not use Django or does not require connection reuse.
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

Follow the reproduction steps, confirm the failure, apply the fix, and repeat the same steps to verify the behavior changes.

Did This Fix Work in Your Case?

Quick signal helps us prioritize which fixes to verify and improve.

Prevention

Track RSS + object counts after deployments; alert on monotonic growth and GC pressure.
Add a long-running test that repeats the failing call path and asserts stable memory.

Version Compatibility Table

Version	Status
4.4.0rc5	Fixed

Related Issues

No related fixes found.

Cluster: celery:configuration-error Celery hub Celery best practices All hubs All clusters

Related clusters: Data consistency Duplicates Duplicate processing

Sources

We don’t republish the full GitHub discussion text. Use the links above for context.