redis-py Async performance issue since version 5.3.0 (Fix)

The Fix

pip install redis==7.1.1

Based on closed redis/redis-py issue #3692 · 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

@@ -1215,16 +1215,17 @@ def can_get_connection(self) -> bool:
     )
     async def get_connection(self, command_name=None, *keys, **options):
+        """Get a connected connection from the pool"""
         async with self._lock:
-            """Get a connected connection from the pool"""

repro.py

self.redis_pool = redis.ConnectionPool.from_url(...)

# Create a Redis client using the connection pool
self.redis_client = redis.Redis(connection_pool=self.redis_pool)

# warm up to create all connections..
conns = []
for _ in range(self.max_connections):
    conn = await self.redis_pool.get_connection('warmup')
    await conn.connect()  # actually opens the TCP connection
    conns.append(conn)

# Release all connections back to the pool
for conn in conns:
    await self.redis_pool.release(conn)

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 redis==7.1.1\nWhen NOT to use: This fix should not be applied if the application relies on the lock for thread safety.\n\n

Why This Fix Works in Production

Trigger: This way, the `ensure_connection` call returns immediately and the lock does not cause a lot of queue up.
Mechanism: Fixes an async connection pool lock contention issue during connection establishment, which was causing performance degradation since version 5.3.0.
Why the fix works: Fixes an async connection pool lock contention issue during connection establishment, which was causing performance degradation since version 5.3.0. (first fixed release: 7.1.1).

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

Production symptom (often without a traceback): This way, the `ensure_connection` call returns immediately and the lock does not cause a lot of queue up.

Proof / Evidence

GitHub issue: #3692
Fix PR: https://github.com/redis/redis-py/pull/3885
First fixed release: 7.1.1
Reproduced locally: No (not executed)
Last verified: 2026-02-09
Confidence: 0.70
Did this fix it?: Yes (upstream fix exists)
Own content ratio: 0.53

Discussion

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

Jump to Sources Open on GitHub

“Hi @d33kayyy, thanks for bringing this to our attention. We will take a look at it soon.”

@petyaslavova · 2025-07-04 · source

“+1 for this issue. In the meantime, we found a solution wherein we warm up the redis pool on service startup: This way, the ensure_connection…”

@rishabhpoddar · 2025-11-11 · source

Failure Signature (Search String)

This way, the `ensure_connection` call returns immediately and the lock does not cause a lot of queue up.

Copy-friendly signature

signature.txt

Failure Signature
-----------------
This way, the `ensure_connection` call returns immediately and the lock does not cause a lot of queue up.

Error Message

Signature-only (no traceback captured)

error.txt

Error Message
-------------
This way, the `ensure_connection` call returns immediately and the lock does not cause a lot of queue up.

Minimal Reproduction

repro.py

self.redis_pool = redis.ConnectionPool.from_url(...)

# Create a Redis client using the connection pool
self.redis_client = redis.Redis(connection_pool=self.redis_pool)

# warm up to create all connections..
conns = []
for _ in range(self.max_connections):
    conn = await self.redis_pool.get_connection('warmup')
    await conn.connect()  # actually opens the TCP connection
    conns.append(conn)

# Release all connections back to the pool
for conn in conns:
    await self.redis_pool.release(conn)

What Broke

Under high load, connection acquisition delays led to noticeable performance degradation.

Fix Options (Details)

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

pip install redis==7.1.1

When NOT to use: This fix should not be applied if the application relies on the lock for thread safety.

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/3885

First fixed release: 7.1.1

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

When NOT to Use This Fix

This fix should not be applied if the application relies on the lock for thread safety.

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

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
7.1.1	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.