HTTP2 - sending server trailers

[prohazko2]

Hi,

Was playing around with gRPC implementation and almost succeed with basic unary calls serving
https://github.com/prohazko2/deno-grpc/blob/0.1.3/serve.ts

1. http2 with Deno.serveHttp was ok
2. protobuf msgs decoding/encoding with protobuf.js was ok
3. thing that I didn't figure out - how to send OK status back to client

Similar node's @grpc/grpc-js response has two server trailers:

[0] Received server trailers:
		grpc-status: 0
		grpc-message: OK

[0] received status code 0 from server
[0] received status details string "OK" from server

Seems like they are sent with this call to node http2stream.sendTrailers
@grpc/grpc-js@1.3.x ... server-call.ts

But I didn't have any luck with sending them with Deno's respondWith / Response API's

[kitsonk]

I haven't tried it yet, but I believe the way it should work is set response.trailers to a promise that resolves with a headers object with the trailing headers (that is according to the Response standard).

[lucacasonato]

Trailers are not supported in the fetch spec anymore, and likely will not be re-introduced unless there is significant demand: whatwg/fetch#981. I don't think we will be supporting them either if the web does not. Removal happened in whatwg/fetch#772.

[kitsonk]

Looking at this more, it feels like instead of "trailers" you want to do something like SSE... where you return a ReadableStream as a body, and continue to .enqueue() Uint8Arrays in the streams controller for as long as you need before closing the controller and ending the response.

[prohazko2]

Thanks, will try.
Also closing issue since trailers out of spec