Subscription with SSE

[ruben-garciapariente]

Are you planning to add support for subscriptions over Server-Side Event?

Many thanks & regards

[hantsy]

Although there is no specification for SSE, I think it is the simple way to get subscription support in a Spring MVC project.

[rstoyanchev]

No plans to support SSE as there is no spec. Yes it can be done, but SSE by itself is only a way to define messages, like WebSocket.

For example, there is no way to map error and completion signals from a Subscription Publisher. For error, you could create a final ExecutionResult and close the connection, but the client can't properly turn that into an error signal to the client side subscription Flux. By comparison GraphQL over WebSocket defines an error message and in the new GraphQlClient, subscriptions can end with an error signal. See the GraphQlTransport for executeSubscription. We cannot support that contract for SSE without a protocol like GraphQL over WebSocket but for SSE.

GraphQL for WebSocket also defines ping and pong messages which is important for connectivity issues with long running streams. For the time being, while there is no spec, we have no plans to support it.

[jma-9code]

It might be a good time to reconsider it.

For Websockets, Spring utilizes the specification found at https://github.com/graphql/graphql-over-http/blob/main/rfcs/GraphQLOverWebSocket.md.

Regarding SSE, we've had a specification available for the past year at https://github.com/graphql/graphql-over-http/blob/main/rfcs/GraphQLOverSSE.md. (from the same guy who work on graphql-ws)

It appears that SSE offers several advantages for various use cases when compared to Websockets. Is it possible to consider its implementation in light of these new developments?

[rstoyanchev]

Thanks for the pointer. Yes, we can add an option for SSE.