unsubscribe function for subscriptionField

[boenni23]

I want to implement my own subscription manager. I can't use the plugin because I need a different API. How do I know if a subscription was ended / lost?

I need something like this:

builder.subscriptionField('station', (t) =>
  t.field({
    args: {
      where: t.arg({
        type: "StationWhereInput"
      })
    },
    type: 'StationSubscriptionPayload',
    subscribe: (_parent: any, args: any, context: any, { fieldName }: ResolveShape) => {
      const channel = uid()
      SUBSCRIPTIONS[channel] = { ...args, channelName: fieldName }
      return pubsub.subscribe(channel)
    },
    unsubscribe: ???,
    resolve: async ({ node, mutation }) => {
      return {
        mutation,
        node
      }
    }
  })
)

I need to track active Subscriptions and want to know when someone stopped a subscription. (remove it from my SUBSCRIPTIONS object).

Or if this is not possible, is there something like apollo's withFilter? That would be even cooler. https://www.apollographql.com/docs/apollo-server/data/subscriptions/#filtering-events

[boenni23]

I found a workaround for all interested. The socket can be found in the context variable. { req: { socket: Socket } } = context You can now listen for the close event.

  socket.addListener('close', () => {
    delete SUBSCRIPTIONS[channel]
  })

[hayes]

I think this is mostly a documentation issue. Subscriptions in graphql are a little weird, and are driven through async-iterators in the core graphql package.

I'll try to find some time to improve the documentation around this, because it's not very straight forward. Listening to the socket closing is probably okay, but ideally I think using the return() feature of the subscription async iterator is probably a more correct solution.

Examples integrating with existing solutions would probably also be helpful.

You can see an example of an async iterator with a return callback here: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/for-await...of#iterating_over_async_iterables