Caching in Ruby Gem, possibly not using Rails

Question

I am rewriting an existing Ruby Gem to include caching. This is for a gem that is relatively commonly used, and accesses a large amount of static data on a web service. Currently, I have a small number of gem users doing a large number of accesses to the service that under normal conditions would be swamping / downing the service , and we're going to put the gem up on github for general consumption.

Right now, users can choose between using the rails cache mechanism, a simple disk cache, or no cache.

What is best practice for letting people choose what cache to use like this (being able to use this outside of rails is a priority so i can't just bail to the underlying caching mechanism)? I'm looking for suggestions/examples for configuration and interface, especially.

Thanks for your suggestions

Answer 1

I wrote a gem called "cachecataz" that has lets any embedder define the caching mechanism/provider they want to use. You can easily use the same methodology to allow the users to pick between multiple different caching mechanisms.

I chose to define the api as a "Provider" and then an "api" which defines which methods are required for any provider. This is what the "Rails.cache" provider and api look like.

Cachecataz.provider = Rails.cache
Cachecataz.api = {:get => :read, :set => :write, :incr => :increment, :exist? => :exist?}

This is a really simple way to have someone choose the Object that responds to the needed methods by the gem writer. Each value in the api hash can either be a symbol or an Object that responds to :call (like Proc or lambda). Then I just use my internal representation in my gem (:get, :set, :incr, :exist?) and lookup the Object/method that needs to be called to execute it at runtime:

def make_api_call(method, *args)
  if Cachecataz.api[method].respond_to?(:call)
    Cachecataz.api[method].call(*args)
  else
    Cachecataz.provider.send(Cachecataz.api[method], *args)
  end
end

This is not all the code, but it is close enough to illustrate how quickly you can implement a pluggable caching api in your own gem and support many cache mechanisms/providers. Cachecataz is open source and up on github if you want to look through the code, it is pretty short and documented.