Activesupport::Db::Cache

ActiveSupport::Cache store that stores data in a database table. Useful for NOT highload applications, when you do not want to use separate cache server like Memcache, Redis etc.. I am going to use it with Heroku application because of limitation of FREE cache storages.

Ruby on Rails support out of box.

Features

Very LOW speed: think twice before use it! :)
persistence: store cache after rails restart
:expire_in option: cache lifetime for each item separetely
total rows limit: auto clean old items when large (5000 rows max)
ability to use external databse for cache store
debug mode: ability to gather information about cache usage (access_time, access_counter)

Installation

Add this line to your application's Gemfile:

gem 'activesupport-db-cache'

And then execute:

$ bundle

Or install it yourself as:

$ gem install activesupport-db-cache

Set cache store in a config/environments/production.rb:

..
config.cache_store = ActiveSupport::Cache::ActiveRecordStore.new
..

Create migration for cache_items table:

$ rails g migration create_cache_items

Copy migration paste

  def up
    connection = ActiveSupport::Cache::ActiveRecordStore::CacheItem.connection
    connection.create_table :cache_items do |t|
      t.string :key
      t.text :value
      t.text :meta_info
      t.datetime :expires_at
      t.datetime :created_at
      t.datetime :updated_at
    end

    connection.add_index :cache_items, :key, :unique => true
    connection.add_index :cache_items, :expires_at
    connection.add_index :cache_items, :updated_at
  end

  def down
    ActiveSupport::Cache::ActiveRecordStore::CacheItem.connection.drop_table :cache_items
  end

Migrate database:

$ rake db:migrate

Done!

Usage

For usage details see ActiveSupport::Cache

External database

By default ActiveRecordStore uses your ActiveRecord::Base.connection. If you whant to use some external database for cache pupose you should set ACTIVE_RECORD_CACHE_STORE_DATABASE_URL env variable:

$ ACTIVE_RECORD_CACHE_STORE_DATABASE_URL="sqlite3://./db/test2.sqlite3" rails s

or postgres:

$ ACTIVE_RECORD_CACHE_STORE_DATABASE_URL="postgresql://user:password@host/database" rails s

or any other.

For Heroku you should add config variable:

$ heroku config:add ACTIVE_RECORD_CACHE_STORE_DATABASE_URL="postgresql://user:password@host/database"

Debug mode

To profile your application you can use debug mode. In debug mode additional meta information is gathered: access_counter, access_time. Be careful: debug mode is EXTREMELY SLOW. Do not use in production for a long time.

To enable debug mode you should set ACTIVE_RECORD_CACHE_STORE_DEBUG_MODE:

$ ACTIVE_RECORD_CACHE_STORE_DEBUG_MODE=1 rails s

For Heroku you should add config variable:

$ heroku config:add ACTIVE_RECORD_CACHE_STORE_DEBUG_MODE=1

Display debug information for a cache item:

$ rails c
> ActiveSupport::Cache::ActiveRecordStore::CacheItem.find_by_key(:foo).meta_info

>

Contributing

Fork it
Create your feature branch (git checkout -b my-new-feature)
Commit your changes (git commit -am 'Added some feature')
Push to the branch (git push origin my-new-feature)
Create new Pull Request