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https://github.com/vasilakisfil/active_cash

Simple active record caching strategies
https://github.com/vasilakisfil/active_cash

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Simple active record caching strategies

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# ActiveCash

Drop in cache strategies for ActiveRecord.



I named the gem ActiveCash in case an official gem arrives with the name

ActiveCache.



## Installation



Add this line to your application's Gemfile:



```ruby

gem 'active_cash'

```



And then execute:



    $ bundle



Or install it yourself as:



    $ gem install active_cash



## Usage

We will add more strategies soon..



#### Existence strategy

``` ruby

class Like < ActiveRecord::Base

  include ActiveCash



         # type      # matched conditions                     # cache name (default is strategy name)

  caches :existence, find_by: [:user_id, :video_id]

  caches :existence, find_by: [:user_id, :video_id, :hidden], as: :hidden #also name: :hidden is supported

end



# Check if Like exists for specific :user_id, :video_id.

@like = Like.cached_existence_by(user_id: 1, video_id: 2)



# Check if a hidden Like exists for specific :user_id, :video_id.

# not sure what hidden could be but let's say that likes table has a boolean hidden column :)

@like = Like.cached_hidden_by(user_id: 1, video_id: 2, hidden: true)

```



I am open for better naming conventions :)



Cache will be created and updated on every object creation, update and deletion

using an `after_commit` callback. Only a string value is saved (true or false)

in Redis (using [redis-objects](https://github.com/nateware/redis-objects) underneath)

making it extremely efficient.



If you want to have a read-driven cache (which could

enhance your hit ratio depending on your read/writes ratio) you can provide an

empty `update_on` array (by default it includes `[:create, :update, :destroy]`):



``` ruby

class Like < ActiveRecord::Base

  include ActiveCash



         # type      # matched conditions  # updating strategies

  caches :existence, find_by: [:video_id], update_on: []

end



# Check if Like exists for specific :user_id, :video_id.

@like = Like.cached_existence_by(user_id: 1, video_id: 2)



# Check if a hidden Like exists for specific :user_id, :video_id.

# not sure what hidden could be but let's say that likes table has a boolean hidden column :)

@like = Like.cached_hidden_by(user_id: 1, video_id: 2, hidden: true)

```



Now cache will be created and updated ONLY IF there is a reference to Redis.



You can also specify the return value (the symbol must be a method defined in the class instance):

``` ruby

class Like < ActiveRecord::Base

  include ActiveCash



  caches :existence, find_by: [:user_id, :video_id, :state], as: :state, returns: :state

end



# Check if Like exists for specific :user_id, :video_id.

# returns the state

# returns false if state.nil?

@like = Like.cached_existence_by(user_id: 1, video_id: 2)

```



Not though that cache will return false if state is nil.



## Todo

Only existence strategy is supported at the moment but the code is designed to

support other kind of caching strategies as well, like caching the whole object

or some parts of it. Also:



* Refactor a bit :(

* We should provide named callbacks

* It's super easy to extend for Mongoid

* Add memcached adapter



## Relevant projects

There is [identity_cache](https://github.com/Shopify/identity_cache) built by Shopify.

It uses memcached unfortunately that's why I needed something else.

For existence strategy ActiveCash is definitely better when it comes to space optimizations.

But I would use that if I wanted a full bloated solution.



Unfortunately I couldn't find any other gem for database caching :(



## Development



After checking out the repo, run `bin/setup` to install dependencies. Then, run `bin/console` for an interactive prompt that will allow you to experiment. 



To install this gem onto your local machine, run `bundle exec rake install`. To release a new version, update the version number in `version.rb`, and then run `bundle exec rake release` to create a git tag for the version, push git commits and tags, and push the `.gem` file to [rubygems.org](https://rubygems.org).



## Contributing



1. Fork it ( https://github.com/vasilakisfil/active_cash/fork )

2. Create your feature branch (`git checkout -b my-new-feature`)

3. Commit your changes (`git commit -am 'Add some feature'`)

4. Push to the branch (`git push origin my-new-feature`)

5. Create a new Pull Request