Celery Celery hangs indefinitely (instead of failing) if

The Fix

pip install celery==4.4.1

Based on closed celery/celery issue #4556 · 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

@@ -51,7 +51,7 @@
 
 CONNECTION_RETRY_STEP = """\
-Trying again {when}...\
+Trying again {when}... ({retries}/{max_retries})\
 """

repro.py

software -> celery:4.1.0 (latentcall) kombu:4.1.0 py:2.7.12
            billiard:3.5.0.3 redis:2.10.6
platform -> system:Linux arch:64bit, ELF imp:CPython
loader   -> celery.loaders.app.AppLoader
settings -> transport:redis results:disabled

broker_url: u'redis://localhost:6379/0'

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==4.4.1\nWhen NOT to use: This fix is not suitable if you require immediate failure on connection issues.\n\n

Why This Fix Works in Production

Trigger: Celery hangs indefinitely (instead of failing) if redis is not started
Mechanism: Celery does not handle connection errors properly when Redis is not started
Why the fix works: Adds progress indication for retry connections to the broker, addressing the issue where Celery hangs indefinitely when Redis is not started. (first fixed release: 4.4.1).

Production impact:

If left unfixed, retry loops can amplify load and turn a small outage into a cascade (thundering herd).

Why This Breaks in Prod

Celery does not handle connection errors properly when Redis is not started
Production symptom (often without a traceback): Celery hangs indefinitely (instead of failing) if redis is not started

Proof / Evidence

GitHub issue: #4556
Fix PR: https://github.com/celery/celery/pull/5915
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: 0.65

Discussion

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

Jump to Sources Open on GitHub

“@keaneokelley I'm testing this in a development environment with no firewall: ip6tables output: I have tracked similar issues here on github and it seems to…”

@nemesifier · 2018-02-23 · source

“Sounds similar to #4328 to me, we've been running into a similar issue, although with RabbitMQ.”

@clokep · 2018-02-22 · source

“I have seen this issue with Redis stopped and when Celery tries to connect to the broker over IPv6 but the firewall is configured to…”

@k3an3 · 2018-02-23 · source

“if you can install celery and kombu from master and try to find the root cause of this hang?”

@auvipy · 2019-05-23 · source

Failure Signature (Search String)

Celery hangs indefinitely (instead of failing) if redis is not started
I expected an `OperationalError` or another exception communicating that celery cannot connect to the broker server.

Copy-friendly signature

signature.txt

Failure Signature
-----------------
Celery hangs indefinitely (instead of failing) if redis is not started
I expected an `OperationalError` or another exception communicating that celery cannot connect to the broker server.

Error Message

Signature-only (no traceback captured)

error.txt

Error Message
-------------
Celery hangs indefinitely (instead of failing) if redis is not started
I expected an `OperationalError` or another exception communicating that celery cannot connect to the broker server.

Minimal Reproduction

repro.py

software -> celery:4.1.0 (latentcall) kombu:4.1.0 py:2.7.12
            billiard:3.5.0.3 redis:2.10.6
platform -> system:Linux arch:64bit, ELF imp:CPython
loader   -> celery.loaders.app.AppLoader
settings -> transport:redis results:disabled

broker_url: u'redis://localhost:6379/0'

What Broke

Celery hangs indefinitely instead of failing when the Redis broker is unavailable.

Why It Broke

Celery does not handle connection errors properly when Redis is not started

Fix Options (Details)

Option A — Upgrade to fixed release Safe default (recommended)

pip install celery==4.4.1

When NOT to use: This fix is not suitable if you require immediate failure on connection issues.

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/5915

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 suitable if you require immediate failure on connection issues.

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
4.4.1	Fixed

Related Issues

No related fixes found.

Cluster: celery:retry-storm Celery hub Celery best practices All hubs All clusters

Related clusters: Configuration error Data consistency Duplicates

Sources

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

Celery Celery hangs indefinitely (instead of failing) if redis is not started (Fix)