redis-py redis's connection pool makes me wonder (Fix)

The Fix

pip install redis==7.1.0

Based on closed redis/redis-py issue #2832 · 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

@@ -1532,7 +1532,7 @@ def release(self, connection: "Connection") -> None:
                 # Gracefully fail when a connection is returned to this pool
                 # that the pool doesn't actually own
-                pass
+                return

repro.py

def release(self, connection):
    self._checkpid()
    with self._lock:
        try:
            self._in_use_connections.remove(connection)
        except KeyError:
            pass

        if self.owns_connection(connection):
            self._available_connections.append(connection)
        else:
            # pool doesn't own this connection. do not add it back
            # to the pool and decrement the count so that another
            # connection can take its place if needed
            self._created_connections -= 1
            connection.disconnect()
            return

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==7.1.0\nWhen NOT to use: Do not apply this fix if the connection management logic is altered in other parts of the code.\n\n

Why This Fix Works in Production

Trigger: except KeyError:
Mechanism: The connection pool incorrectly decremented the created connections count when releasing a connection not owned by the pool
Why the fix works: Removes the decrement of the created connections count when releasing a connection not owned by the pool, addressing issue #2832. (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

The connection pool incorrectly decremented the created connections count when releasing a connection not owned by the pool
Production symptom (often without a traceback): except KeyError:

Proof / Evidence

GitHub issue: #2832
Fix PR: https://github.com/redis/redis-py/pull/3514
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: 0.58

Discussion

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

Jump to Sources Open on GitHub

“PR is created with a fix: https://github.com/redis/redis-py/pull/3514”

@petyaslavova · 2025-02-18 · source

Failure Signature (Search String)

except KeyError:

Copy-friendly signature

signature.txt

Failure Signature
-----------------
except KeyError:

Error Message

Signature-only (no traceback captured)

error.txt

Error Message
-------------
except KeyError:

Minimal Reproduction

repro.py

def release(self, connection):
    self._checkpid()
    with self._lock:
        try:
            self._in_use_connections.remove(connection)
        except KeyError:
            pass

        if self.owns_connection(connection):
            self._available_connections.append(connection)
        else:
            # pool doesn't own this connection. do not add it back
            # to the pool and decrement the count so that another
            # connection can take its place if needed
            self._created_connections -= 1
            connection.disconnect()
            return

What Broke

This led to incorrect tracking of available connections, potentially causing connection exhaustion.

Why It Broke

The connection pool incorrectly decremented the created connections count when releasing a connection not owned by the pool

Fix Options (Details)

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

pip install redis==7.1.0

When NOT to use: Do not apply this fix if the connection management logic is altered in other parts of the code.

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/3514

First fixed release: 7.1.0

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

When NOT to Use This Fix

Do not apply this fix if the connection management logic is altered in other parts of the code.

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

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.