GraphQL subscriptions for AnyCable

A (mostly) drop-in replacement for default ActionCable subscriptions adapter shipped with graphql gem but works with AnyCable!

Why?

AnyCable is fast because it does not execute any Ruby code. But default subscription implementation shipped with graphql gem requires to do exactly that: re-evaluate GraphQL queries in ActionCable process. AnyCable doesn't support this (it's possible but hard to implement).

See https://github.com/anycable/anycable-rails/issues/40 for more details and discussion.

Differences

• Subscription information is stored in Redis database configured to be used by AnyCable. Expiration or data cleanup should be configured separately (see below).
• GraphQL queries for all subscriptions are re-executed in the process that triggers event (it may be web server, async jobs, rake tasks or whatever)

Compatibility

• Should work with ActionCable in development
• Should work without Rails via LiteCable

Requirements

AnyCable must be configured with redis broadcast adapter (this is default).

Installation

Add this line to your application's Gemfile:

gem 'graphql-anycable'

And then execute:

$ bundle

Or install it yourself as:

$ gem install graphql-anycable

Usage

1. Plug it into the schema (replace from ActionCable adapter if you have one):

   class MySchema < GraphQL::Schema
     use GraphQL::Subscriptions::AnyCableSubscriptions
   
     subscription SubscriptionType
   end
   

2. Execute query in ActionCable/LiteCable channel.

   class GraphqlChannel < ApplicationCable::Channel
     def execute(data)
       result = 
         MySchema.execute(
           query: data["query"],
           context: context,
           variables: Hash(data["variables"]),
           operation_name: data["operationName"],
         )
   
       transmit(
         result: result.subscription? ? { data: nil } : result.to_h,
         more: result.subscription?,
       )
     end
   
     def unsubscribed
       channel_id = params.fetch("channelId")
       MySchema.subscriptions.delete_channel_subscriptions(channel_id)
     end
   
     private
   
     def context
       {
         account_id: account&.id,
         channel: self,
       }
     end
   end
   

   Make sure that you're passing channel instance as channel key to the context.

3. Trigger events as usual:

   MySchema.subscriptions.trigger(:product_updated, {}, Product.first!, scope: account.id)
   

Operations

To avoid filling Redis storage with stale subscription data:

1. Set subscription_expiration_seconds setting to number of seconds (e.g. 604800 for 1 week). See configuration section below for details.

2. Execute rake graphql:anycable:clean once in a while to clean up stale subscription data.

   Heroku users should set up use_redis_object_on_cleanup setting to false due to limitations in Heroku Redis.

Configuration

GraphQL-Anycable uses anyway_config to configure itself. There are several possibilities to configure this gem:

1. Environment variables:

   GRAPHQL_ANYCABLE_SUBSCRIPTION_EXPIRATION_SECONDS=604800
   GRAPHQL_ANYCABLE_USE_REDIS_OBJECT_ON_CLEANUP=true
   

2. YAML configuration files:

   # config/graphql_anycable.yml
   production:
     subscription_expiration_seconds: 300 # 5 minutes
     use_redis_object_on_cleanup: false # For restricted redis installations
   

3. Configuration from your application code:

   GraphQL::Anycable.configure do |config|
     config.subscription_expiration_seconds = 3600 # 1 hour
   end
   

And any other way provided by anyway_config. Check its documentation!

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. To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and tags, and push the .gem file to rubygems.org.

Contributing

Bug reports and pull requests are welcome on GitHub at https://github.com/Envek/graphql-anycable.

License

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