Is there a way to get Rust tonic gRPC client streams to start without waiting for the first message?

Question

It seems that the following code blocks until the first streamed object arrives:

let mut stream = client
        .stream_something(StreamRequest {})
        .await
        .unwrap()
        .into_inner();

Specifically I want to start the stream, and then send other RPCs that may trigger a state change that sends a message on the stream.

But I can't start the stream first, because that can block forever. And I don't want to send the other RPC first, because then I may miss the streamed update triggered by my other RPC.

I hope that I don't have to resort to wrapping the whole thing, and provide a new interface such as mpsc.

Answer 1

I was in a similar situation, but we had access to the server.

I was considering two options:

1. Modify the server (written in python) to give a 200 response (in my case, just an empty message).

2. Spawn a separate task using channels so that it waits for a response to the request.

I chose the first option. I haven't tried the second one, but here's a piece of code that might be useful: https://gist.github.com/kyle-mccarthy/73ab6c78e6d3bf0819fc7c00b90161f4