redis-py 4.0.0b1 breaks script_flush on pre-6.2 server (Fix)

The Fix

pip install redis==7.1.0

Based on closed redis/redis-py issue #1639 · 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%.

Jump to Verify Open PR/Commit

@@ -2922,16 +2922,22 @@ def script_debug(self, *args):
         )
 
-    def script_flush(self, sync_type="SYNC"):
+    def script_flush(self, sync_type=None):
         """Flush all scripts from the script cache.

repro

(assuming a Redis server on localhost):

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 redis==7.1.0\nWhen NOT to use: Do not use if it changes public behavior or if the failure cannot be reproduced.\n\n

Why This Fix Works in Production

Trigger: 4.0.0b1 breaks script_flush on pre-6.2 server
Mechanism: Modifies the script_flush method to default to None for pre-6.2 Redis servers, resolving compatibility issues.
Why the fix works: Modifies the script_flush method to default to None for pre-6.2 Redis servers, resolving compatibility issues. (first fixed release: 7.1.0).

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

Shows up under Python 3.8.10 in real deployments (not just unit tests).
Production symptom (often without a traceback): 4.0.0b1 breaks script_flush on pre-6.2 server

Proof / Evidence

GitHub issue: #1639
Fix PR: https://github.com/redis/redis-py/pull/1641
First fixed release: 7.1.0
Reproduced locally: No (not executed)
Last verified: 2026-02-07
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).

Jump to Sources Open on GitHub

“Thank you for reporting @bmerry”

@chayim · 2021-10-25 · source

Failure Signature (Search String)

4.0.0b1 breaks script_flush on pre-6.2 server
**Description**: In 4.0.0b1, the implementation of `script_flush` always calls either `SCRIPT FLUSH SYNC` or `SCRIPT FLUSH ASYNC` on the server. However, the SYNC/ASYNC modifier

Copy-friendly signature

signature.txt

Failure Signature
-----------------
4.0.0b1 breaks script_flush on pre-6.2 server
**Description**: In 4.0.0b1, the implementation of `script_flush` always calls either `SCRIPT FLUSH SYNC` or `SCRIPT FLUSH ASYNC` on the server. However, the SYNC/ASYNC modifier was only added in Redis 6.2, making it fail on older versions.

Error Message

Signature-only (no traceback captured)

error.txt

Error Message
-------------
4.0.0b1 breaks script_flush on pre-6.2 server
**Description**: In 4.0.0b1, the implementation of `script_flush` always calls either `SCRIPT FLUSH SYNC` or `SCRIPT FLUSH ASYNC` on the server. However, the SYNC/ASYNC modifier was only added in Redis 6.2, making it fail on older versions.

Minimal Reproduction

(assuming a Redis server on localhost):

Environment

Python: 3.8.10

Fix Options (Details)

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

pip install redis==7.1.0

When NOT to use: Do not use if it changes public behavior or if the failure cannot be reproduced.

Use when you can deploy the upstream fix. It is usually lower-risk than long-lived workarounds.

Fix reference: https://github.com/redis/redis-py/pull/1641

First fixed release: 7.1.0

Last verified: 2026-02-07. Validate in your environment.

When NOT to Use This Fix

Do not use if it changes public behavior or if the failure cannot be reproduced.

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

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
7.1.0	Fixed

Related Issues

No related fixes found.

Cluster: redis-py:configuration-error redis-py hub redis-py best practices All hubs All clusters

Related clusters: Retry storm Data consistency Race condition

Sources

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