GraphQL Cache

A custom caching plugin for graphql-ruby

Goals

• Provide resolver-level caching for GraphQL APIs written in ruby
• Configurable to work with or without Rails
• API Documentation

Why?

At StackShare we've been rolling out graphql-ruby for several of our new features and found ourselves in need of a caching solution. We could have simply used Rails.cache in our resolvers, but this creates very verbose types or resolver classes. It also means that each and every resolver must define it's own expiration and key. GraphQL Cache solves that problem by integrating caching functionality into the graphql-ruby resolution process making caching transparent on most fields except for a metadata flag denoting the field as cached. More details on our motivation for creating this here.

Installation

Add this line to your application's Gemfile:

gem 'graphql-cache'

And then execute:

$ bundle

Or install it yourself as:

$ gem install graphql-cache

Setup

1. Use GraphQL Cache as a plugin in your schema.

class MySchema < GraphQL::Schema
  query Types::Query

  use GraphQL::Cache
end

2. Add the custom caching field class to your base object class. This adds the cache metadata key when defining fields.

module Types
  class Base < GraphQL::Schema::Object
    field_class GraphQL::Cache::Field
  end
end

Also note that if you want access to the cache keyword param in interface fields, the field_class directive must be added to your base interface module as well

Configuration

GraphQL Cache can be configured in an initializer:

# config/initializers/graphql_cache.rb

GraphQL::Cache.configure do |config|
  config.namespace = 'GraphQL::Cache' # Cache key prefix for keys generated by graphql-cache
  config.cache     = Rails.cache      # The cache object to use for caching
  config.logger    = Rails.logger     # Logger to receive cache-related log messages
  config.expiry    = 5400             # 90 minutes (in seconds)
end

Usage

Any object, list, or connection field can be cached by simply adding cache: true to the field definition:

field :calculated_field, Int, cache: true

Custom Expirations

By default all keys will have an expiration of GraphQL::Cache.expiry which defaults to 90 minutes. If you want to set a field-specific expiration time pass a hash to the cache parameter like this:

field :calculated_field, Int, cache: { expiry: 10800 } # expires key after 180 minutes

Custom cache keys

GraphQL Cache generates a cache key using the context of a query during execution. A custom key can be included to implement versioned caching as well. By providing a :key value to the cache config hash on a field definition. For example, to use a custom method that returns the cache key for an object use:

field :calculated_field, Int, cache: { key: :custom_cache_key }

With this configuration the cache key used for this resolved value will use the result of the method custom_cache_key called on the parent object.

Forcing the cache

It is possible to force graphql-cache to resolve and write all cached fields to cache regardless of the presence of a given key in the cache store. This will effectively "renew" any existing cached expirations and warm any that don't exist. To use forced caching, add a value to :force_cache in the query context:

MySchema.execute('{ company(id: 123) { cachedField }}', context: { force_cache: true })

This will resolve all cached fields using the field's resolver and write them to cache without first reading the value at their respective cache keys. This is useful for structured cache warming strategies where the cache expiration needs to be updated when a warming query is made.

Development

After checking out the repo, run bin/setup to install dependencies. Then, run rake spec to run the tests. You can also 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.

Contributing

Bug reports and pull requests are welcome on GitHub at https://github.com/stackshareio/graphql-cache. This project is intended to be a safe, welcoming space for collaboration, and contributors are expected to adhere to the Contributor Covenant code of conduct.

License

The gem is available as open source under the terms of the MIT License.

Code of Conduct

Everyone interacting in the graphql-cache project's codebases, issue trackers, chat rooms and mailing lists is expected to follow the code of conduct..