redis-py Bug in PubSub client health check handling (Fix)

The Fix

Fixes the health check handling in the PubSub client to ensure consistent responses based on the decode_responses setting.

Based on closed redis/redis-py issue #3791 · PR/commit linked

Jump to Verify Open PR/Commit

@@ -1009,10 +1009,22 @@ def is_health_check_response(self, response) -> bool:
         bulk response, instead of a multi-bulk with "pong" and the response.
         """
-        return response in [
-            self.health_check_response,  # If there was a subscription
-            self.health_check_response_b,  # If there wasn't

repro.py

File "/usr/local/lib/python3.12/dist-packages/redis/client.py", line 1016, in punsubscribe
    return self.execute_command("PUNSUBSCRIBE", *args)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.12/dist-packages/redis/client.py", line 874, in execute_command
    self.clean_health_check_responses()
  File "/usr/local/lib/python3.12/dist-packages/redis/client.py", line 890, in clean_health_check_responses
    raise PubSubError(
redis.exceptions.PubSubError: A non health check response was cleaned by execute_command: redis-py-health-check

verify

Re-run the minimal reproduction on your broken version, then apply the fix and re-run.

fix.md

Option A — Apply the official fix\nFixes the health check handling in the PubSub client to ensure consistent responses based on the decode_responses setting.\nWhen NOT to use: This fix should not be applied if the application relies on the previous inconsistent behavior.\n\n

Why This Fix Works in Production

Trigger: return self.execute_command("PUNSUBSCRIBE", *args)
Mechanism: Inconsistent handling of health check responses in the PubSub client based on decode_responses setting

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 3.12 in real deployments (not just unit tests).
Inconsistent handling of health check responses in the PubSub client based on decode_responses setting
Surfaces as: File "/usr/local/lib/python3.12/dist-packages/redis/client.py", line 1016, in punsubscribe

Proof / Evidence

GitHub issue: #3791
Fix PR: https://github.com/redis/redis-py/pull/3870
Reproduced locally: No (not executed)
Last verified: 2026-02-12
Confidence: 0.80
Did this fix it?: Yes (upstream fix exists)
Own content ratio: 0.47

Discussion

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

Jump to Sources Open on GitHub

“Hi @ManelCoutinhoSensei, thank you for reporting this! We will have a look at it.”

@petyaslavova · 2025-10-08 · source

“@petyaslavova would it make you life easier if opened a PR with just this change and then you only have to think about it/review it”

@ManelCoutinhoSensei · 2025-11-06 · source

Failure Signature (Search String)

return self.execute_command("PUNSUBSCRIBE", *args)

Error Message

Stack trace

error.txt

Error Message
-------------
File "/usr/local/lib/python3.12/dist-packages/redis/client.py", line 1016, in punsubscribe
    return self.execute_command("PUNSUBSCRIBE", *args)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.12/dist-packages/redis/client.py", line 874, in execute_command
    self.clean_health_check_responses()
  File "/usr/local/lib/python3.12/dist-packages/redis/client.py", line 890, in clean_health_check_responses
    raise PubSubError(
redis.exceptions.PubSubError: A non health check response was cleaned by execute_command: redis-py-health-check

Minimal Reproduction

repro.py

File "/usr/local/lib/python3.12/dist-packages/redis/client.py", line 1016, in punsubscribe
    return self.execute_command("PUNSUBSCRIBE", *args)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.12/dist-packages/redis/client.py", line 874, in execute_command
    self.clean_health_check_responses()
  File "/usr/local/lib/python3.12/dist-packages/redis/client.py", line 890, in clean_health_check_responses
    raise PubSubError(
redis.exceptions.PubSubError: A non health check response was cleaned by execute_command: redis-py-health-check

Environment

Python: 3.12

What Broke

Encountered PubSubError during health check response handling, causing application errors.

Why It Broke

Inconsistent handling of health check responses in the PubSub client based on decode_responses setting

Fix Options (Details)

Option A — Apply the official fix

Fixes the health check handling in the PubSub client to ensure consistent responses based on the decode_responses setting.

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

Fix reference: https://github.com/redis/redis-py/pull/3870

Last verified: 2026-02-12. Validate in your environment.

When NOT to Use This Fix

This fix should not be applied if the application relies on the previous inconsistent 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

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.

Related Issues

No related fixes found.

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Related clusters: Configuration error Retry storm Race condition

Sources

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