Question

I’ve been struggling with this error for quite some time:

Redis::ProtocolError: Got 'i' as initial reply byte. 
If you're running in a multi-threaded environment, make sure you pass the :thread_safe
option when initializing the connection. If you're in a forking environment, such as 
Unicorn, you need to connect to Redis after forking.

It happens intermittently in apps that use Unicorn and Redis. From this redis-rb Github issue it looks the :thread_safe option is now enabled by default. I am using redis 2.2.2 because redis 3.0.1 is not compatible with the latest version of resque.

In my Unicorn config I’m using Redis.current.quit after the fork.

I’m also connecting to Redis with a gem called ruote-redis which is a storage implementation for the workflow engine Ruote.

How can I ensure that all of my Redis connections are stable and that I don’t get this error anymore which is disrupting to the normal use of our app?

Answer 1

Unicorn is not multi-threaded. Are you using threads yourself?

As stated in the docs, the problem you’re hitting is that multiple Unicorn workers are sharing the same connection (ie the same underlying file descriptor).

This change, included in version redis-rb 3.0, makes it even clearer.

If you’re still hitting this error please post your Unicorn configuration.