Get the list of all subscribers to a public graphql subscription

You will need to create a Publisher/Subscriber instance. Check out this example. From there you should be able to implement the counter. So each time you add a subscriber you can increment the count.

This example might also be helpful to you: https://graphql.org/blog/subscriptions-in-graphql-and-relay/

Very useful links for you, please follow instructions from the first link to practice pub/sub and the second link is the recommendations for production.

1. https://docs.nestjs.com/graphql/subscriptions
2. https://github.com/apollographql/graphql-subscriptions#pubsub-implementations