Redis - Dealing with (error) NOAUTH Authentication required

Overview

A Redis instance that had been running for years without any memory issues
suddenly started throwing connection errors, so I’ve summarized how I handled it.

The Error

PHP Fatal error:  Uncaught exception 'RedisException' with message 'Failed to AUTH connection'

The authenticated connection failed and an Exception was thrown.

I hadn’t set requirepass anywhere in the Redis configuration,
so it felt like “why all of a sudden?”.

The path to the Redis config differs across environments, but in my case it was as follows:
/etc/redis/6379.conf

As shown below, requirepass is commented out.

# requirepass

The Fix

• Kill the process

• Note: restarting Redis with something like service redis restart did not change the situation.

# ps aux | grep 'redis' | grep -v 'grep'

root     12743  0.1  0.2  40604  2124 ?        Ssl  10:50   0:00 /usr/local/bin/redis-server *:6379

• Start Redis again.

# service redis start

• Set requirepass

Since the system was in operation and I didn’t want to touch the application’s source code itself,
I set an empty requirepass.

redis-cli> CONFIG SET REQUIREPASS ''

The above was enough to handle the immediate situation without problems.

Wrap-up

When using Redis again, it would be better to configure authentication
and have the application connect with a password specified as well.

That said, I’ll continue investigating why this suddenly happened.

If anyone knows the reason, I’d be grateful for a comment.