Are subscription triggers scoped to the current schema?

[janko]

As part of integration testing subscription triggers with Action Cable, I noticed the internal stream name that was generated didn't appear to embed the current schema identifier. I went digging in graphql gem code, but I couldn't find concrete proof that a triggered subscription update won't be broadcasted across all schemas.

We have multiple GQL schemas, and one are v1 & v2 versions of the same API, which share many of the same subscription fields. For example, let's say I have the following:

class MyApi::V1
  class SubscriptionType < GraphQL::Schema::Object
    field :some_event, ...
  end

  class Schema < GraphQL::Schema
    use GraphQL::Subscriptions::ActionCableSubscriptions
    subscription(SubscriptionType)
  end
end

class MyApi::V2
  class SubscriptionType < GraphQL::Schema::Object
    field :some_event, ...
  end

  class Schema < GraphQL::Schema
    use GraphQL::Subscriptions::ActionCableSubscriptions
    subscription(SubscriptionType)
  end
end

Then one subscriber subscribes to v1 schema's someEvent { ... } and another subscriber subscribes to v2 schema's someEvent { ... }. If I call MyApi::V1.subscriptions.trigger(:some_event, {}, {}), what part of the graphql gem will ensure that only the first subscriber's (subscribed to v1 schema) subscription will get updated and not the second one (subscribed to v2 schema)?

[rmosolgo]

Hey, great question. With ActionCable, you can add a namespace:, for example:

use GraphQL::Subscriptions::ActionCableSubscriptions, namespace: "V2" # or "V1", etc

It will be included in the stream identifiers later on:

graphql-ruby/lib/graphql/subscriptions/action_cable_subscriptions.rb

Lines 245 to 251 in 4836730

	def stream_subscription_name(subscription_id)
	[SUBSCRIPTION_PREFIX, @transmit_ns, subscription_id].join
	end
	def stream_event_name(event)
	[EVENT_PREFIX, @transmit_ns, event.topic].join
	end

Does that work for you?

[janko]

Yes, that works for us 👍🏻 I discovered this when I was reading the source code, I didn't see it mentioned in the guides, so I wasn't sure whether it was intended for this use case. Glad that there is any easy solution 🙂