Granola::Cache

Provide caching options for the result of your Granola serializers.

Example

class PersonSerializer < Granola::Serializer
  cache key: "person", expire_in: 3600

  def data
    {
      id: object.id,
      name: object.name,
    }
  end

  def cache_key
    "%s:%s" % [object.id, object.updated_at.to_i]
  end
end

serializer = PersonSerializer.new(person)
serializer.to_json # Generates JSON and stores it in the cache.
serializer.to_json # Retreives from cache without rendering.

person.update(...) # Do something that would change the `cache_key` (e.g. update
                   # the object's `updated_at`.)

serializer.to_json # Generates JSON again, storing the new version in the cache.

NOTE: Changing the cache key will invalidate previous versions of the cached object, but will not delete them from the cache store.

Install

gem install granola-cache

Cache Stores

By default, Granola::Cache stores cached output from serializers in an in-memory Hash. This is not meant for production use. You should provide an alternative store for your application.

Alternative stores should implement a single method:

fetch(key, options = {}, &block)

Where:

• key: The cache key to fetch from cache.
• options: Any options the cache store can take (for example, :expire_in if your store supports Time-based expiration.)

If the key isn't found in the store, the block is invoked, and the result from this block is both returned and stored in the cache for further use.

There's an example Redis Store included in this repository, should you wish to inspect it.

Rails

This is compatible with ActiveSupport::Cache::Store, so if you're in a Rails application, you can just do this in config/initializers/granola.rb:

Granola::Cache.store = Rails.cache

Cache Options

Pass caching options to a serializer by calling the cache singleton method.

Granola::Cache only recognizes these options: :key and :store. Any other option passed will be ignored by Granola, but forwarded to the cache store.

:key

This is meant to be a prefix applied to cache keys. In the example above, any particular serializer will be stored in the cache with the following key:

"#{key}/#{object.id}:#{object.updated_at.to_i}"

:store

This allows overriding the caching store for a specific serializer.

class WeeklyReportSerializer < Granola::Serializer
  cache store: DifferentStore.new
end

See Cache Stores for more on configuring the global store.

License

This project is shared under the MIT license. See the attached LICENSE file for details.