JbuilderCacheMulti

Useful when you need to retrieve fragments for a collection of objects from the cache. This plugin gives you method called 'cache_collection!' which uses fetch_multi (new in Rails 4.1) to retrieve multiple keys in a single go.

This means less queries to the cache == faster responses. If items are not found, they are writen to the cache (individualy. memcache doesn't support writing items in batch...yet).

Tested with Rails 4.1 + Memcached + Dalli

Installation

Add this line to your application's Gemfile:

gem 'jbuilder_cache_multi'

And then execute:

$ bundle

Or install it yourself as:

$ gem install jbuilder_cache_multi

Usage

Renders the given block for each item in the collection. Accepts optional 'key' attribute in options (e.g. key: 'v1').

Note: At the moment, does not accept the partial name as an argument (#todo)

Examples:

json.cache_collection! @people, expires_in: 10.minutes do |person|
  json.partial! 'person', :person => person
end

# Or with optional key

json.cache_collection! @people, expires_in: 10.minutes, key: 'v1' do |person|
  json.partial! 'person', :person => person
end

# Or with a proc as a key 

json.cache_collection! @people, expires_in: 10.minutes, key: proc {|person| person.last_posted_at } do |person|
  json.partial! 'person', :person => person
end

NOTE: If the items in your collection don't change frequently, it might be better to cache the entire collection like this: (in which case you don't need this gem)

json.cache! @people do
  json.partial! 'person', collection: @people, as: :person
end

Or you can use a combination of both! This will cache the entire collection. If a single item changes it will use read_multi to get all unchanged items and regenerate only the changed item(s).

json.cache! @people do
  json.cache_collection! @people do |person|
    json.partial! 'person', :person => person
  end
end

Last thing: If you are using a collection for the cache key, may I recommend the 'scope_cache_key' gem? (check out my fork for a Rails 4 version: https://github.com/joshblour/scope_cache_key). It very quickly calculates a hash for all items in the collection (MD5 hash of updated_at + IDs).

You can also conditionally cache a block by using cache_collection_if! like this:

json.cache_collection_if! do_cache?, @people, expires_in: 10.minutes do |person|
  json.partial! 'person', :person => person
end

Todo

• Add support for passing a partial name as an argument (e.g. json.cache_collection! @people, partial: 'person') or maybe even just "json.cache_collection! @people" and infer the partial name from the collection...

• When rendering other partials, use the hash of THAT partial for the cache_key (I beleieve it currently uses the view from where cache_collection! is called to calculate the cache_key) #not_good

Contributing

1. Fork it ( https://github.com/joshblour/jbuilder_cache_multi/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

Testing

bundle install
appraisal install
appraisal rake test

Credit

Inspired by https://github.com/n8/multi_fetch_fragments. Thank you! And of course https://github.com/rails/jbuilder