"IndexError: string index out of range" on get_message from PubSub

[jmspereira]

Version: What redis-py and what redis version is the issue happening on? redis-py 5.2.0 with redis 7.2.4

Platform: What platform / version? Python 3.10.12 on Ubuntu 22.04

Description:

Hey everyone,

I have an application that uses Redis in a production environment, but the service crashed during a call to the get_message method from PubSub with the following error (unfortunately I am not able to reproduce the error after several attempts):

  File "/usr/local/lib/python3.10/dist-packages/redis/client.py", line 1056, in get_message
    return self.handle_message(response, ignore_subscribe_messages)
  File "/usr/local/lib/python3.10/dist-packages/redis/client.py", line 1098, in handle_message
    "data": response[2],
IndexError: string index out of range

Do you have any ideas on how this is possible?

Best regards, Jorge

[petyaslavova]

Hi @jmspereira, can you please share more details about how you are initialising your client and using the pubsub? Some small code example would be great!

[jmspereira]

Hey @petyaslavova, thank you for the response!

This minimal example should illustrate how I am initializing the connection with redis and using the pubsub:

import socket

from redis import Sentinel
from redis.backoff import ExponentialBackoff
from redis.retry import Retry
from redis.exceptions import ConnectionError as RedisConnectionError
from redis.exceptions import TimeoutError as RedisTimeoutError


def main():
    sentinel = Sentinel(
        [('localhost', 26379), ('localhost', 26380), ('localhost', 26381)],
        min_other_sentinels=0,
        encoding="utf-8",
        decode_responses=True,
        socket_keepalive=True,
        socket_timeout=30,
        socket_connect_timeout=30,
        health_check_interval=5,
        retry_on_error=(RedisConnectionError, RedisTimeoutError, socket.timeout),
        retry=Retry(ExponentialBackoff(10, 0.5), 5),
        db=0,
    )

    connection = sentinel.master_for("mymaster")
    connection.config_set("notify-keyspace-events", "KEA")
    pub_sub = connection.pubsub()

    while True:
        event = pub_sub.get_message(timeout=1, ignore_subscribe_messages=True)
        if event:
            print(event)
        else:
            print("No event")


if __name__ == '__main__':
    main()

Additional notes:

• I was not able to replicate the error using the minimal example;
• In the production environment where the error occurs it happens once every week;
• The redis database in the production environment has around ~40k clients, ~75k keys and is receiving ~4k commands/per second.