Celery Make redis use of sorted sets for group results

The Fix

pip install celery==5.0.0

Based on closed celery/celery issue #6290 · PR/commit linked

Production note: Most teams hit this during upgrades or environment changes. Roll out with a canary and smoke critical endpoints (health, OpenAPI/docs) before 100%.

Open PR/Commit

@@ -405,7 +405,7 @@ def _chord_zset(self):
             'result_backend_transport_options', {}
         )
-        return transport_options.get('result_chord_ordered', False)
+        return transport_options.get('result_chord_ordered', True)

fix.md

Option A — Upgrade to fixed release\npip install celery==5.0.0\nWhen NOT to use: Do not apply this fix if you require the previous behavior of ordered results.\n\n

Why This Fix Works in Production

Trigger: Following up on #6245 - can we make the use of sorted set opt-out for 5.0 as discussed? In particular, this would simply be a change to the default value of…
Mechanism: The default configuration for using ordered sets in Redis was not set to opt-out
Why the fix works: Makes the use of ordered sets in Redis opt-out for Celery 5.0, changing the default configuration value and updating documentation and tests accordingly. (first fixed release: 5.0.0).

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

The default configuration for using ordered sets in Redis was not set to opt-out
Production symptom (often without a traceback): Following up on #6245 - can we make the use of sorted set opt-out for 5.0 as discussed? In particular, this would simply be a change to the default value of the config value, and associated changes to tests and doco merged in #6245.

Proof / Evidence

GitHub issue: #6290
Fix PR: https://github.com/celery/celery/pull/6294
First fixed release: 5.0.0
Reproduced locally: No (not executed)
Last verified: 2026-02-09
Confidence: 0.85
Did this fix it?: Yes (upstream fix exists)
Own content ratio: 0.72

Discussion

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

Jump to Sources Open on GitHub

“ping @thedrow - if you're on board with getting this into 5.0, would you please add it to the milestone? I'll get a PR up…”

@maybe-sybr · 2020-08-06 · source

Failure Signature (Search String)

Following up on #6245 - can we make the use of sorted set opt-out for 5.0 as discussed? In particular, this would simply be a change to the default value of the config value, and

Copy-friendly signature

signature.txt

Failure Signature
-----------------
Following up on #6245 - can we make the use of sorted set opt-out for 5.0 as discussed? In particular, this would simply be a change to the default value of the config value, and associated changes to tests and doco merged in #6245.

Error Message

Signature-only (no traceback captured)

error.txt

Error Message
-------------
Following up on #6245 - can we make the use of sorted set opt-out for 5.0 as discussed? In particular, this would simply be a change to the default value of the config value, and associated changes to tests and doco merged in #6245.

What Broke

Users experienced unexpected ordering of group results in Redis backend.

Why It Broke

The default configuration for using ordered sets in Redis was not set to opt-out

Fix Options (Details)

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

pip install celery==5.0.0

When NOT to use: Do not apply this fix if you require the previous behavior of ordered results.

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/6294

First fixed release: 5.0.0

Last verified: 2026-02-09. Validate in your environment.

When NOT to Use This Fix

Do not apply this fix if you require the previous behavior of ordered results.

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
5.0.0	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.

Celery Make redis use of sorted sets for group results opt-out (Fix)