The Fix
pip install celery==5.6.0
Based on closed celery/celery issue #9960 · 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.
@@ -37,9 +37,10 @@ jobs:
REDIS_PORT: 6379
rabbitmq:
- image: rabbitmq
+ image: rabbitmq:management
ports:
repro.py
"""
Celery application configuration for reproducing native delayed delivery bug.
"""
from celery import Celery
from kombu import Exchange, Queue
app = Celery()
# Configure broker
app.conf.broker_url = 'amqp://guest:guest@localhost:5672//'
app.conf.result_backend = None
# Single exchange for all queues
default_exchange = Exchange('celery.topic', type='topic')
# Define multiple task queues with quorum type triggering native delayed
# delivery
app.conf.task_queues = [
Queue('queue-a', exchange=default_exchange, routing_key='queue-a',
queue_arguments={'x-queue-type': 'quorum'}),
Queue('queue-b', exchange=default_exchange, routing_key='queue-b',
queue_arguments={'x-queue-type': 'quorum'}),
Queue('queue-c', exchange=default_exchange, routing_key='queue-c',
queue_arguments={'x-queue-type': 'quorum'}),
]
# Task routing
app.conf.task_routes = {
'celery_app.task_for_queue_a': {'queue': 'queue-a'},
'celery_app.task_for_queue_c': {'queue': 'queue-c'},
}
@app.task
def task_for_queue_a(message):
"""Task that should be routed to queue-a."""
print(f"[queue-a] Received: {message}")
@app.task
def task_for_queue_c(message):
"""Task that should be routed to queue-c."""
print(f"[queue-c] Received: {message}")
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==5.6.0\nWhen NOT to use: This fix is not safe if the application relies on strict queue binding behavior.\n\n
Why This Fix Works in Production
- Trigger: - [x] I have included all related issues and possible duplicate issues
- Mechanism: A failure in binding one queue prevents subsequent queues from being bound for native delayed delivery in AMQP
- Why the fix works: Fixes the issue where a failure in binding one queue prevents subsequent queues from being bound for native delayed delivery in AMQP. (first fixed release: 5.6.0).
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
- Triggered by an upgrade/regression window: 3.9–3.10 breaks; 5.6.0 is the first fixed release.
- A failure in binding one queue prevents subsequent queues from being bound for native delayed delivery in AMQP
- Production symptom (often without a traceback): - [x] I have included all related issues and possible duplicate issues
Proof / Evidence
- GitHub issue: #9960
- Fix PR: https://github.com/celery/celery/pull/9959
- First fixed release: 5.6.0
- Affected versions: 3.9–3.10
- Reproduced locally: No (not executed)
- Last verified: 2026-02-08
- Confidence: 0.85
- Did this fix it?: Yes (upstream fix exists)
- Own content ratio: 0.45
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)
- - [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
"""
Celery application configuration for reproducing native delayed delivery bug.
"""
from celery import Celery
from kombu import Exchange, Queue
app = Celery()
# Configure broker
app.conf.broker_url = 'amqp://guest:guest@localhost:5672//'
app.conf.result_backend = None
# Single exchange for all queues
default_exchange = Exchange('celery.topic', type='topic')
# Define multiple task queues with quorum type triggering native delayed
# delivery
app.conf.task_queues = [
Queue('queue-a', exchange=default_exchange, routing_key='queue-a',
queue_arguments={'x-queue-type': 'quorum'}),
Queue('queue-b', exchange=default_exchange, routing_key='queue-b',
queue_arguments={'x-queue-type': 'quorum'}),
Queue('queue-c', exchange=default_exchange, routing_key='queue-c',
queue_arguments={'x-queue-type': 'quorum'}),
]
# Task routing
app.conf.task_routes = {
'celery_app.task_for_queue_a': {'queue': 'queue-a'},
'celery_app.task_for_queue_c': {'queue': 'queue-c'},
}
@app.task
def task_for_queue_a(message):
"""Task that should be routed to queue-a."""
print(f"[queue-a] Received: {message}")
@app.task
def task_for_queue_c(message):
"""Task that should be routed to queue-c."""
print(f"[queue-c] Received: {message}")
What Broke
Tasks sent to undeclared queues are discarded, leading to potential data loss.
Why It Broke
A failure in binding one queue prevents subsequent queues from being bound for native delayed delivery in AMQP
Fix Options (Details)
Option A — Upgrade to fixed release Safe default (recommended)
pip install celery==5.6.0
When NOT to use: This fix is not safe if the application relies on strict queue binding behavior.
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/9959
First fixed release: 5.6.0
Last verified: 2026-02-08. Validate in your environment.
When NOT to Use This Fix
- This fix is not safe if the application relies on strict queue binding behavior.
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
- 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 |
|---|---|
| 3.10 | Broken |
| 3.9 | Broken |
| 5.6.0 | Fixed |
Related Issues
No related fixes found.
Sources
We don’t republish the full GitHub discussion text. Use the links above for context.