redis-py Possible deadlock in class `Pipeline` (Fix)

The Fix

pip install redis==7.1.0

Based on closed redis/redis-py issue #3289 · PR/commit linked

Production note: This tends to surface only under concurrency. Reproduce with load tests and watch for lock contention/cancellation paths.

Open PR/Commit

@@ -369,6 +369,8 @@ def __init__(
             raise RedisError("Client caching is only supported with RESP version 3")
 
+        # TODO: To avoid breaking changes during the bug fix, we have to keep non-reentrant lock.
+        # TODO: Remove this before next major version (7.0.0)
         self.single_connection_lock = threading.Lock()

fix.md

Option A — Upgrade to fixed release\npip install redis==7.1.0\nWhen NOT to use: Do not use this fix if backward compatibility is a concern.\n\n

Why This Fix Works in Production

Trigger: Possible deadlock in class `Pipeline`
Mechanism: Deadlock occurs when __del__ is called during get_connection while holding a lock
Why the fix works: Fixed potential deadlock when GC takes action and __del__ invoked in the middle of get_connection() or release() methods. (first fixed release: 7.1.0).

Production impact:

If left unfixed, failures can be intermittent under concurrency (hard to reproduce; shows up as sporadic 5xx/timeouts).

Why This Breaks in Prod

Shows up under Python 3.11 in real deployments (not just unit tests).
Deadlock occurs when __del__ is called during get_connection while holding a lock
Production symptom (often without a traceback): Possible deadlock in class `Pipeline`

Proof / Evidence

GitHub issue: #3289
Fix PR: https://github.com/redis/redis-py/pull/3654
First fixed release: 7.1.0
Reproduced locally: No (not executed)
Last verified: 2026-02-08
Confidence: 0.95
Did this fix it?: Yes (upstream fix exists)
Own content ratio: 0.74

Discussion

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

Jump to Sources Open on GitHub

“Could you please include a small MRE (minimal reproducible example)?”

@alessio-locatelli · 2024-10-26 · repro detail · source

Failure Signature (Search String)

Possible deadlock in class `Pipeline`

Copy-friendly signature

signature.txt

Failure Signature
-----------------
Possible deadlock in class `Pipeline`

Error Message

Signature-only (no traceback captured)

error.txt

Error Message
-------------
Possible deadlock in class `Pipeline`

Environment

Python: 3.11

Why It Broke

Deadlock occurs when __del__ is called during get_connection while holding a lock

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 this fix if backward compatibility is a concern.

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/3654

First fixed release: 7.1.0

Last verified: 2026-02-08. Validate in your environment.

When NOT to Use This Fix

Do not use this fix if backward compatibility is a concern.

Did This Fix Work in Your Case?

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

Prevention

Add a stress test that runs high-concurrency workloads and fails on thread dumps / blocked locks.
Enable watchdog dumps in prod (faulthandler, thread dump endpoint) to capture deadlocks quickly.
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
7.1.0	Fixed

Related Issues

No related fixes found.

Cluster: redis-py:race-condition redis-py hub redis-py best practices All hubs All clusters

Related clusters: Configuration error Retry storm Data consistency

Sources

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