Can we stream results?

[ddeboer]

When querying multiple sources, if one times out, the combined result must wait for the timeout.

Can we instead stream results using GraphQL?

[sdevalk]

Cool idea! Would server-sent events (SSE) work, sending results from individual sources to the client if/when they arrive?

Such an implementation probably comes with backwards incompatible changes to both the NoT server and its clients, though. Unless the 'streamed results' get their own, new endpoint, e.g. /graphql-stream?

[ddeboer]

Hey @sdevalk, SSE would work but is a different protocol, so would require a separate endpoint where we push SSE events to.

GraphQL itself has two ‘new’ directives for incremental query delivery: @defer and @stream. They are not yet supported in Mercurius, the GraphQL server that we use in conjunction with Fastify. Once Mercurius adds support, it should work on our current endpoint, without having to introduce a new one.

For now, I’m inclined to wait a bit for Mercurius to support the new directives because it seems the most idiomatic way to go about this in GraphQL. Or we could switch to Apollo Server or GraphQL Yoga, both of which already implement the new directives.

In the meantime, we can recommend users that suffer from long wait times to fire a separate GraphQL query for each (unreliable) source. An alternative solution is discussed in #1599.