Simple Cacheable

Simple Cacheable is a simple cache implementation based on activerecord, it is extracted from rails-bestpractices.com.

it supports activerecord >= 3.0.0, tested on 2.0.0 and works with jruby.

Introduction

Here is a blog post to introduce simple_cacheable gem, http://rails-bestpractices.com/blog/posts/24-simple_cacheable

Usage

class User < ActiveRecord::Base
  include Cacheable

  has_many :posts
  has_one :account

  model_cache do
    with_key                          # User.find_cached(1)
    with_attribute :login             # User.find_cached_by_login('flyerhzm')
    with_method :last_post            # user.cached_last_post
    with_association :posts, :account # user.cached_posts, user.cached_account
  end

  def last_post
    posts.last
  end
end

class Account < ActiveRecord::Base
  belongs_to :user
end

class Post < ActiveRecord::Base
  include Cacheable

  belongs_to :user
  has_many :comments, :as => :commentable

  model_cache do
    with_key                                # post.find_cached(1)
    with_class_method  :default_post        # Post.cached_default_post
    with_association   :user, :comments     # post.cached_user, post.cached_comments
  end

  def self.default_post
    Post.first
  end
end

class Comment < ActiveRecord::Base
  include Cacheable

  belongs_to :commentable, :polymorphic => true

  model_cache do
    with_association :commentable  # comment.cached_commentable
  end
end

Advanced Usage

Utilize Simple Cacheable to cache ActiveRecord objects without marshalling errors:

  Cacheable.fetch "collection_of_twelve_users", expires_in: 1.day do
    User.limit(12)
  end

Override modified_cache_key to customize cache keys. Single point for dependency injection.

  # E.G. if you wanted to version your cache:
  class User < ActiveRecord::Base
    has_one :cache_version

    def self.modified_cache_key(key)
      "#{cache_version.version}/#{key}"
    end
  end

(modified_cache_key can be overriden at the class level or the instance level. By default the instance implementation falls back to the class implementation.)

Install

add the following code to your Gemfile

gem "simple_cacheable"

Gotchas

Caching, and caching invalidation specifically, can be hard and confusing. Simple Cacheable methods should expire correctly in most cases. Be careful using with_method and with_class_method, they should specifically not be used to return collections. This is demonstrated well in Tobias Lutke's presentation: Rockstar Memcaching.