redis-py TimeoutError in 2.10.2 (Fix)

The Fix

pip install redis==4.0.0

Based on closed redis/redis-py issue #521 · PR/commit linked

Production note: Watch p95/p99 latency and retry volume; timeouts can turn into retry storms and duplicate side-effects.

Jump to Verify Open PR/Commit

@@ -348,7 +348,7 @@ def read_response(self):
             # buffer. if the data received doesn't end with \r\n, there's more.
             if HIREDIS_USE_BYTE_BUFFER:
-                if self._buffer[bufflen - 2:bufflen] != SYM_CRLF:
+                if bufflen > 2 and self._buffer[bufflen - 2:bufflen] != SYM_CRLF:
                     continue

repro.py

File "/app/.heroku/python/lib/python2.7/site-packages/redis/client.py", line 2593, in execute
    return execute(conn, stack, raise_on_error)
  File "/app/.heroku/python/lib/python2.7/site-packages/redis/client.py", line 2514, in _execute_pipeline
    self.parse_response(connection, args[0], **options))
  File "/app/.heroku/python/lib/python2.7/site-packages/redis/client.py", line 2536, in parse_response
    self, connection, command_name, **options)
  File "/app/.heroku/python/lib/python2.7/site-packages/redis/client.py", line 577, in parse_response
    response = connection.read_response()
  File "/app/.heroku/python/lib/python2.7/site-packages/redis/connection.py", line 569, in read_response
    response = self._parser.read_response()
  File "/app/.heroku/python/lib/python2.7/site-packages/redis/connection.py", line 339, in read_response
    raise TimeoutError("Timeout reading from socket")
TimeoutError: Timeout reading from socket

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==4.0.0\nWhen NOT to use: This fix should not be applied if the application relies on the previous buffer handling behavior.\n\n

Why This Fix Works in Production

Trigger: return execute(conn, stack, raise_on_error)
Mechanism: An edge case in buffer handling caused a TimeoutError during pipeline execution
Why the fix works: Handles an edge case in buffer handling that caused a TimeoutError in version 2.10.2. (first fixed release: 4.0.0).

Production impact:

If left unfixed, this can cause silent data inconsistencies that propagate (bad cache entries, incorrect downstream decisions).

Why This Breaks in Prod

Shows up under Python 2.7 in real deployments (not just unit tests).
An edge case in buffer handling caused a TimeoutError during pipeline execution
Surfaces as: File "/app/.heroku/python/lib/python2.7/site-packages/redis/client.py", line 2593, in execute

Proof / Evidence

GitHub issue: #521
Fix PR: https://github.com/redis/redis-py/pull/522
First fixed release: 4.0.0
Reproduced locally: No (not executed)
Last verified: 2026-02-09
Confidence: 0.70
Did this fix it?: Yes (upstream fix exists)
Own content ratio: 0.33

Discussion

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

Jump to Sources Open on GitHub

“I'm able to reproduce this with HIREDIS_USE_BYTE_BUFFER == False. In the last iteration, the only character received is \n And self._reader.gets() evals True.”

@joshowen · 2014-08-13 · source

Failure Signature (Search String)

return execute(conn, stack, raise_on_error)

Error Message

Stack trace

error.txt

Error Message
-------------
File "/app/.heroku/python/lib/python2.7/site-packages/redis/client.py", line 2593, in execute
    return execute(conn, stack, raise_on_error)
  File "/app/.heroku/python/lib/python2.7/site-packages/redis/client.py", line 2514, in _execute_pipeline
    self.parse_response(connection, args[0], **options))
  File "/app/.heroku/python/lib/python2.7/site-packages/redis/client.py", line 2536, in parse_response
    self, connection, command_name, **options)
  File "/app/.heroku/python/lib/python2.7/site-packages/redis/client.py", line 577, in parse_response
    response = connection.read_response()
  File "/app/.heroku/python/lib/python2.7/site-packages/redis/connection.py", line 569, in read_response
    response = self._parser.read_response()
  File "/app/.heroku/python/lib/python2.7/site-packages/redis/connection.py", line 339, in read_response
    raise TimeoutError("Timeout reading from socket")
TimeoutError: Timeout reading from socket

Minimal Reproduction

repro.py

File "/app/.heroku/python/lib/python2.7/site-packages/redis/client.py", line 2593, in execute
    return execute(conn, stack, raise_on_error)
  File "/app/.heroku/python/lib/python2.7/site-packages/redis/client.py", line 2514, in _execute_pipeline
    self.parse_response(connection, args[0], **options))
  File "/app/.heroku/python/lib/python2.7/site-packages/redis/client.py", line 2536, in parse_response
    self, connection, command_name, **options)
  File "/app/.heroku/python/lib/python2.7/site-packages/redis/client.py", line 577, in parse_response
    response = connection.read_response()
  File "/app/.heroku/python/lib/python2.7/site-packages/redis/connection.py", line 569, in read_response
    response = self._parser.read_response()
  File "/app/.heroku/python/lib/python2.7/site-packages/redis/connection.py", line 339, in read_response
    raise TimeoutError("Timeout reading from socket")
TimeoutError: Timeout reading from socket

Environment

Python: 2.7

What Broke

Timeouts occurred when executing a pipeline with certain arguments, impacting application performance.

Why It Broke

An edge case in buffer handling caused a TimeoutError during pipeline execution

Fix Options (Details)

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

pip install redis==4.0.0

When NOT to use: This fix should not be applied if the application relies on the previous buffer handling behavior.

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/522

First fixed release: 4.0.0

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 previous buffer handling behavior.

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

Make timeouts explicit and test them (unit + integration) to avoid silent behavior changes.
Instrument retries (attempt count + reason) and alert on spikes to catch dependency slowdowns.

Version Compatibility Table

Version	Status
4.0.0	Fixed

Related Issues

No related fixes found.

Cluster: redis-py:data-consistency redis-py hub redis-py best practices All hubs All clusters

Related clusters: Configuration error Retry storm Race condition

Sources

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