Rails 4 Simple Model Caching With Redis

Question

I am new to Redis and Rails caching, and would like to perform simple model caching. I have just read these 2 articles :

http://www.sitepoint.com/rails-model-caching-redis/

http://www.victorareba.com/tutorials/speed-your-rails-app-with-model-caching-using-redis

Since Redis model caching consists in storing JSON strings in redis and retrieving them with code like

def fetch_snippets
  snippets =  $redis.get("snippets")
  if snippets.nil?
    snippets = Snippet.all.to_json
    $redis.set("snippets", snippets)
  end
  @snippets = JSON.load snippets
end

I don't understand what is the need of using

gem 'redis-rails'
gem 'redis-rack-cache'

I don't see where the cache store or other caching mechanisms are at use in that kind of examples, since they consist only in reading/writing to Redis.

Thank you for any help.

Answer 1

Here is what I have in my Gemfile

gem 'redis'
gem 'readthis'
gem 'hiredis'
gem 'redis-browser'

readthis - recently implemented nice feature to not crash Rails when Redis is down Disable Rails caching if Redis is down. And it supports advanced Redis data types (not just strings as redis-rails).

hiredis - is a little faster

redis-browser - allows me to see what is actually cached (easier than cli).

Here is my application.rb

config.cache_store = :readthis_store, { expires_in: 1.hour.to_i, namespace: 'foobar', redis: { host: config.redis_host, port: 6379, db: 0 }, driver: :hiredis }

Then in my models I do:

def my_method_name
  Rails.cache.fetch("#{cache_key}/#{__method__}", expires_in: 1.hour) do
    # put my code here
  end
end

I used https://github.com/MiniProfiler/rack-mini-profiler to see which queries were firing lots of DB request and determined what I should cache.