Namespacing keys in Kredis

#ruby #rails #redis

Kredis is a library that provides an abstraction of higher level data structures for Redis. It's really useful and will be included in Rails 7.

I like to namespace all my keys in Redis because it prevents clashes between keys from multiple apps in development locally. It also opens the door to sharing a single Redis instance between multiple apps in production. That's usually not a good idea but for a few side projects, it might be a viable and economical choice.

At first glance it seems like it's really easy to add a namespace to keys in Kredis. There's a Kredis.namespace= method. However it's primarily meant to prevent clashes in parallel testing. If you look at the implementation, it looks like:

def namespace=(namespace)
  Thread.current[:kredis_namespace] = namespace
end

It only sets the namespace on the current thread. That's fine when using a single threaded process like the Rails Console. But in a multi-threaded process like Sidekiq, you're going to be in trouble.

One approach to solve this could be setting the namespace on every thread. However that's pretty messy.

The redis-namespace gem

A clean way to namespacing Kredis is to install the redis-namespace gem. It provides a namespaced proxy to an underlying Redis connection.

To configure Kredis to use this proxy instead of creating its own connection; we need to add the following line in application.rb:

config.kredis.connector = ->(config) { 
  Redis::Namespace.new("my_app:kredis", redis: Redis.new(config)) 
}

Now all keys we set with Kredis will be namespaced with "my_app:kredis". This also makes it easier to filter keys if you're using a GUI tool like Medis to view your Redis data.