Can't find docs/examples of Subscriptions

[Sequoia]

What happened?

I want to write a Subscription resolver

• Looked through this repo
• Looked through https://gqlgen.com

What did you expect?

• Expected to find a section called "Subscriptions" explaining how to write them with gqlgen

More info

Through some issue searching I found a link to this: https://github.com/99designs/gqlgen/blob/master/example/chat/resolvers.go#L115-L150

That's what I'm working off of currently. It would be useful to have some part of the docs touch on subscriptions.

[arddor]

While the chat example is a good starting point, it misses in my opinion two important parts:

1. The channel is not closed in the cleanup. This leads to gqlgen never being able to terminate the internal go routine.

go func() {
  <-ctx.Done()
  r.mu.Lock()
  delete(room.Observers, id)
  close(events) // <-
  r.mu.Unlock()
}()

2. The lock in this case can get blocked when there are connection issues with one client. The example buffers the channel, but I would argue that at some point the message should just be dropped so that no other clients are blocked from receiving messages.

r.mu.Lock()
for _, observer := range room.Observers {
  if observer.Username == "" || observer.Username == message.CreatedBy {
    select {
    case observer.Message <- &message:
    default:
      log.Printf("could not send message to %v\n", observer.Username)
    }
  }
}
r.mu.Unlock()

[stale[bot]]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[RobertoOrtis]

Yes, it would be nice to have some documentation on subscriptions. I have been trying to figure out how they work.

[txbrown]

The only other reference I can find is https://www.freecodecamp.org/news/https-medium-com-anshap1719-graphql-subscriptions-with-go-gqlgen-and-mongodb-5e008fc46451/

[RobertoOrtis]

The only other reference I can find is https://www.freecodecamp.org/news/https-medium-com-anshap1719-graphql-subscriptions-with-go-gqlgen-and-mongodb-5e008fc46451/

I got them working with arsmn's fork for gofiber framework. However, I am having an issue where I get an error whenever a user abruptly closes the subscription by closing the browser window/tab

https://github.com/99designs/gqlgen/issues/1281

[Naatan]

Bump

[justgook]

Bump

[slayerjain]

bump

[psigen]

The only other reference I can find is https://www.freecodecamp.org/news/https-medium-com-anshap1719-graphql-subscriptions-with-go-gqlgen-and-mongodb-5e008fc46451/

FWIW: this is the original post on medium, which doesn't have broken formatting: https://medium.com/@anshap1719/how-to-handle-graphql-subscriptions-with-go-gqlgen-and-mongodb-1152ee6da82d

[Ammce]

Bump

Why they can't do it in over a year?

[Unkn0wnCat]

Hey everyone,

I've just done the PR #2346 containing my suggestion for the documentation on Subscriptions. I'd be happy if you could all proof-read my document, and give me feedback if anything is unclear or if I did any typos! 🙂

[AndriyKalashnykov]

Thanks @Unkn0wnCat for great Subscriptions recipe! On another note i'm wondering why there is not example of GraphQL client written in Go that subsribes to a subscription? All examples I've seen are NodeJS wondering what is the reason.

[kateile]

Thanks for the docs @Unkn0wnCat It has showed me direction to go however coming from node.js background. There are few concepts like event triggers based on topics like it is shown here I am now wondering how to implement this in go. Can we have similar things to those?

Also I used to see pub/sub things much in nodejs like using Redis or Google pub sub? Do we need the same things in golang?

[Unkn0wnCat]

@AndriyKalashnykov I've not had to implement a subscriptions client in Go myself, but it looks like hasura/go-graphql-client has the feature you're looking for. Keep in mind I've not worked with the linked module, so I can't give you any rating or pointers on the quality of it, but it has a lot of stars as well as an active maintainer - so give it a try!

@kateile In the reference example in the recipe I've left off with the Go routine having an open channel, on top of that you could easily build your own topic-subscriptions or use a module like Google's PubSub, or a Redis client.

Something like this may work for Redis (no warranty on that, I've just typed this off the top of my head, not tried nor compiled it):

func (r *subscriptionResolver) CurrentTime(ctx context.Context) (<-chan *model.Time, error) {
	ch := make(chan *model.Time)
        rdb := GetRedisInstance() // You'll need to provide your own redis client instance 😛 

	go func() {
		for {
			pubsub := rdb.Subscribe(ctx, "timechannel")

                        incoming := pubsub.Channel()

                        for msg := range incoming {
                          myObject := UnmarshalMyObject(msg.Payload) // You'll somehow need to transform your Redis payload into the right object

                          select {
			    case ch <- myObject:

			    default:
				    fmt.Println("Channel closed.")
                                    pubsub.Close()
				    return
			    }
                        }

                        close(ch)
		}
	}()

	return ch, nil
}

Hope this helps for both of you!