Send status 200 as soon as query parse is valid

[wmertens]

Is your feature request related to a problem? Please describe.

Our nginx proxy automatically sends 502 if the server takes too long to respond. This is a good feature IMHO.

However, if a mutation takes a long time to process, that means the caller will get 502 instead of the result.

Describe the solution you'd like

As soon as the query is parsed and deemed valid, before running the resolvers, yoga should already respond with 200.

Describe alternatives you've considered

Complicated async setups with subscriptions.

[ardatan]

Hmm interesting use case, but if we do that, this won't be valid anymore for status codes;
https://the-guild.dev/graphql/yoga-server/docs/features/error-masking#modifying-http-status-codes-and-headers
Some users want to return different status codes for auth if the query is restricted etc.
However you can use hooks to set your status code earlier than Yoga starts to feed the response stream on your own;
https://the-guild.dev/graphql/yoga-server/docs/features/envelop-plugins

[wmertens]

So it would be after onValidate, but how can I tell yoga to send the 200 but leave the connection open, and won't that interfere with the other plugins?

[ardatan]

Due to the current design of Yoga, it is not possible with the Fetch based API we currently provide but depending on what you use as a server underneath you can manipulate the original response object available in the context. For example, it is "context.res" in vanilla Node.js

[enisdenjo]

As per GraphQL over HTTP spec, the response is to be sent when the operation execution is done. Yoga is following the spec and will stay compliant.

There is a few things you can do:

1. Optimize mutations (recommended)
2. Detect mutations in nginx and allow only those to take longer
3. Increase timeout in nginx
4. Custom Yoga plugin for early responses

If you still decide to go with 4. - you must make sure to handle the following:

1. What should the response body look like? (It's not a GQL response anymore)
2. What happens if the mutation execution fails (but is parsable and valid), how do you notify the client?
3. How do you make sure the mutation does not hang forever

[n1ru4l]

A possible solution could be using a different transport, e.g. GraphQL over SSE, as it also sends pings. But I also noticed that in Yoga for GraphQL over SSE, the status code is blocked by the initial execution result.