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https://github.com/anycable/graphql-anycable

A drop-in replacement for GraphQL ActionCable subscriptions. Works with AnyCable.
https://github.com/anycable/graphql-anycable

anycable graphql hacktoberfest rails ruby

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A drop-in replacement for GraphQL ActionCable subscriptions. Works with AnyCable.

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# GraphQL subscriptions for AnyCable



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



[![Gem Version](https://badge.fury.io/rb/graphql-anycable.svg)](https://badge.fury.io/rb/graphql-anycable)

[![Tests](https://github.com/anycable/graphql-anycable/actions/workflows/test.yml/badge.svg)](https://github.com/anycable/graphql-anycable/actions/workflows/test.yml)





Sponsored by Evil Martians




## 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:



```ruby

gem 'graphql-anycable', '~> 1.0'

```



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):

 

    ```ruby

    class MySchema < GraphQL::Schema

      use GraphQL::AnyCable, broadcast: true

    

      subscription SubscriptionType

    end

    ```

 

 2. Execute query in ActionCable/LiteCable channel.

 

    ```ruby

    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

        MySchema.subscriptions.delete_channel_subscriptions(self)

      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:

 

    ```ruby

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

    ```



## Broadcasting



By default, graphql-anycable evaluates queries and transmits results for every subscription client individually. Of course, it is a waste of resources if you have hundreds or thousands clients subscribed to the same data (and has huge negative impact on performance).



Thankfully, GraphQL-Ruby has added [Subscriptions Broadcast](https://graphql-ruby.org/subscriptions/broadcast.html) feature that allows to group exact same subscriptions, execute them and transmit results only once.



To enable this feature, turn on [Interpreter](https://graphql-ruby.org/queries/interpreter.html) and pass `broadcast` option set to `true` to graphql-anycable.



By default all fields are marked as _not safe for broadcasting_. If a subscription has at least one non-broadcastable field in its query, GraphQL-Ruby will execute every subscription for every client independently. If you sure that all your fields are safe to be broadcasted, you can pass `default_broadcastable` option set to `true` (but be aware that it can have security impllications!)



```ruby

class MySchema < GraphQL::Schema

  use GraphQL::Execution::Interpreter # Required for graphql-ruby before 1.12. Remove it when upgrading to 2.0

  use GraphQL::Analysis::AST # Required for graphql-ruby before 1.12. Remove it when upgrading to 2.0

  use GraphQL::AnyCable, broadcast: true, default_broadcastable: true



  subscription SubscriptionType

end

```



See GraphQL-Ruby [broadcasting docs](https://graphql-ruby.org/subscriptions/broadcast.html) for more details.



## 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](#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](https://devcenter.heroku.com/articles/heroku-redis#connection-permissions).



## Configuration



GraphQL-AnyCable uses [anyway_config] to configure itself. There are several possibilities to configure this gem:



 1. Environment variables:



    ```.env

    GRAPHQL_ANYCABLE_SUBSCRIPTION_EXPIRATION_SECONDS=604800

    GRAPHQL_ANYCABLE_USE_REDIS_OBJECT_ON_CLEANUP=true

    GRAPHQL_ANYCABLE_REDIS_PREFIX=graphql

    ```



 2. YAML configuration files (note that this is `config/graphql_anycable.yml`, *not* `config/anycable.yml`):



    ```yaml

    # config/graphql_anycable.yml

    production:

      subscription_expiration_seconds: 300 # 5 minutes

      use_redis_object_on_cleanup: false # For restricted redis installations

      redis_prefix: graphql # You can configure redis_prefix for anycable-graphql subscription prefixes. Default value "graphql"

    ```



 3. Configuration from your application code:



    ```ruby

    GraphQL::AnyCable.configure do |config|

      config.subscription_expiration_seconds = 3600 # 1 hour

      config.redis_prefix = "graphql" # on our side, we add `-` ourselves after the redis_prefix

    end

    ```



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



## Emergency actions

In situations when you don't set `subscription_expiration_seconds`, have a lot of inactive subscriptions, and `GraphQL::AnyCable::Cleaner` does`t help in that, 

you can do the following actions for clearing subscriptions



1. Set `config.subscription_expiration_seconds`. After that, the new subscriptions will have `TTL`

2. Run the script

```ruby

   redis = GraphQL::AnyCable.redis

   config = GraphQL::AnyCable.config

   

   # do it for subscriptions

   redis.scan_each("graphql-subscription:*") do |key|

     redis.expire(key, config.subscription_expiration_seconds) if redis.ttl(key) < 0

     # or you can just remove it immediately

     # redis.del(key) if redis.ttl(key) < 0

   end



   # do it for channels

   redis.scan_each("graphql-channel:*") do |key|

     redis.expire(key, config.subscription_expiration_seconds) if redis.ttl(key) < 0

     # or you can just remove it immediately

     # redis.del(key) if redis.ttl(key) < 0

   end

```



Or you can change the `redis_prefix` in the `configuration` and then remove all records with the old_prefix 

For instance:



1. Change the `redis_prefix`. The default `redis_prefix` is `graphql`

2. Run the ruby script, which remove all records with `old prefix`

```ruby

  redis.scan_each("graphql-*") do |key|

    redis.del(key)

  end

```



## Data model



As in AnyCable there is no place to store subscription data in-memory, it should be persisted somewhere to be retrieved on `GraphQLSchema.subscriptions.trigger` and sent to subscribed clients. `graphql-anycable` uses the same Redis database as AnyCable itself.



 1. Grouped event subscriptions: `graphql-fingerprints:#{event.topic}` sorted set. Used to find all subscriptions on `GraphQLSchema.subscriptions.trigger`.



    ```

    ZREVRANGE graphql-fingerprints:1:myStats: 0 -1

    => 1:myStats:/MyStats/fBDZmJU1UGTorQWvOyUeaHVwUxJ3T9SEqnetj6SKGXc=/0/RBNvo1WzZ4oRRq0W9-hknpT7T8If536DEMBg9hyq_4o=

    ```



 2. Event subscriptions: `graphql-subscriptions:#{event.fingerptint}` set containing identifiers for all subscriptions for given operation with certain context and arguments (serialized in _topic_). Fingerprints are already scoped by topic.



    ```

    SMEMBERS graphql-subscriptions:1:myStats:/MyStats/fBDZmJU1UGTorQWvOyUeaHVwUxJ3T9SEqnetj6SKGXc=/0/RBNvo1WzZ4oRRq0W9-hknpT7T8If536DEMBg9hyq_4o=

    => 52ee8d65-275e-4d22-94af-313129116388

    ```



 3. Subscription data: `graphql-subscription:#{subscription_id}` hash contains everything required to evaluate subscription on trigger and create data for client.



    ```

    HGETALL graphql-subscription:52ee8d65-275e-4d22-94af-313129116388

    => {

      context:        '{"user_id":1,"user":{"__gid__":"Z2lkOi8vZWJheS1tYWcyL1VzZXIvMQ"}}',

      variables:      '{}',

      operation_name: 'MyStats'

      query_string:   'subscription MyStats { myStatsUpdated { completed total processed __typename } }',

    }

    ```



 4. Channel subscriptions: `graphql-channel:#{subscription_id}` set containing identifiers for subscriptions created in ActionCable channel to delete them on client disconnect.



    ```

    SMEMBERS graphql-channel:17420c6ed9e

    => 52ee8d65-275e-4d22-94af-313129116388

    ```



## Stats



You can grab Redis subscription statistics by calling



```ruby

    GraphQL::AnyCable.stats

```



It will return a total of the amount of the key with the following prefixes



```

    graphql-subscription

    graphql-fingerprints

    graphql-subscriptions

    graphql-channel

```



The response will look like this



```json

  {

    "total": {

      "subscription":22646,

      "fingerprints":3200,

      "subscriptions":20101,

      "channel": 4900

    }

  }

```



You can also grab the number of subscribers grouped by subscriptions



```ruby

    GraphQL::AnyCable.stats(include_subscriptions: true)

```



It will return the response that contains `subscriptions`



```json

  {

    "total": {

      "subscription":22646,

      "fingerprints":3200,

      "subscriptions":20101,

      "channel": 4900

    },

    "subscriptions": {

      "productCreated": 11323,

      "productUpdated": 11323

    }

  }

```



Also, you can set another `scan_count`, if needed.

The default value is 1_000



```ruby

    GraphQL::AnyCable.stats(scan_count: 100)

```



We can set statistics data to [Yabeda][] for tracking amount of subscriptions



```ruby

  # config/initializers/metrics.rb

  Yabeda.configure do

    group :graphql_anycable_statistics do

      gauge :subscriptions_count,  comment: "Number of graphql-anycable subscriptions"

    end

  end

```



```ruby

  # in your app

  statistics = GraphQL::AnyCable.stats[:total]



  statistics.each do |key , value|

    Yabeda.graphql_anycable_statistics.subscriptions_count.set({name: key}, value)

  end

```



Or you can use `collect`

```ruby

  # config/initializers/metrics.rb

  Yabeda.configure do

    group :graphql_anycable_statistics do

      gauge :subscriptions_count,  comment: "Number of graphql-anycable subscriptions"

    end

    

    collect do

      statistics = GraphQL::AnyCable.stats[:total]



      statistics.each do |redis_prefix, value|

        graphql_anycable_statistics.subscriptions_count.set({name: redis_prefix}, value)

      end

    end

  end

```



## Testing applications which use `graphql-anycable`



You can pass custom redis-server URL to AnyCable using ENV variable.



    ```bash

    REDIS_URL=redis://localhost:6379/5 bundle exec rspec

    ```



## 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](https://rubygems.org).



### Releasing new versions



1. Bump version number in `lib/graphql/anycable/version.rb`



   In case of pre-releases keep in mind [rubygems/rubygems#3086](https://github.com/rubygems/rubygems/issues/3086) and check version with command like `Gem::Version.new(AfterCommitEverywhere::VERSION).to_s`



2. Fill `CHANGELOG.md` with missing changes, add header with version and date.



3. Make a commit:



   ```sh

   git add lib/graphql/anycable/version.rb CHANGELOG.md

   version=$(ruby -r ./lib/graphql/anycable/version.rb -e "puts Gem::Version.new(GraphQL::AnyCable::VERSION)")

   git commit --message="${version}: " --edit

   ```



4. Create annotated tag:



   ```sh

   git tag v${version} --annotate --message="${version}: " --edit --sign

   ```



5. Fill version name into subject line and (optionally) some description (list of changes will be taken from `CHANGELOG.md` and appended automatically)



6. Push it:



   ```sh

   git push --follow-tags

   ```



7. GitHub Actions will create a new release, build and push gem into [rubygems.org](https://rubygems.org)! You're done!



## 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](https://opensource.org/licenses/MIT).



[graphql gem]: https://github.com/rmosolgo/graphql-ruby "Ruby implementation of GraphQL"

[AnyCable]: https://github.com/anycable/anycable "Polyglot replacement for Ruby WebSocket servers with Action Cable protocol"

[LiteCable]: https://github.com/palkan/litecable "Lightweight Action Cable implementation (Rails-free)"

[anyway_config]: https://github.com/palkan/anyway_config "Ruby libraries and applications configuration on steroids!"

[Yabeda]: https://github.com/yabeda-rb/yabeda "Extendable solution for easy setup of monitoring in your Ruby apps"