Client streaming from the web browser

[paralin]

Looking into "connect" currently - it's very nice, with clean generated code.

Just one question regarding client-side streams:

This page: https://connect.build/docs/go/streaming - says that:

All that said, connect-go fully supports all three types of streaming. All streaming subtypes work with the gRPC, gRPC-Web, and Connect protocols.

This implies that grpc-web can be used to run client-stream RPCs with Connect, but according to the grpc-web docs:

https://github.com/grpc/grpc-web/blob/master/doc/streaming-roadmap.md

Once the whatwg spec is finalized and upload-streaming is supported by major browsers (2020), we will add client-streaming support in gRPC-Web (and Envoy) which will also enable half-duplex bidi streaming support.

This indicates that client-streaming is not implemented in grpc-web yet.

So I am having trouble understanding how connect implements the client-streaming with grpc-web. Is it actually not implemented?

If not, that above sentence in the docs may be a bit confusing to others looking for client-streaming implementations (like me).

[akshayjshah]

Great question :) To me, that document is confusing because it uses "gRPC-Web" to refer to two different things: a protocol and a specific Javascript implementation.

The gRPC-Web protocol supports unary, client streaming, and server streaming RPCs with HTTP/1.1 or HTTP/2. If you have an HTTP/2 connection, it also supports bidirectional streaming.

The connect-go implementation uses net/http, which has all the capabilities needed for all four RPC types. So connect-go servers and clients will happily handle any RPC type using the gRPC-Web protocol.

The grpc/grpc-web implementation runs in web browsers, which buffer request bodies and therefore can't do client or bidirectional streaming. The upcoming connect-web implementation will have the same limitation.

(Also, I'm going to convert this issue to a discussion. I haven't used discussions before, but we're giving them a try in this repo and this is a really good question!)

[paralin]

Thanks for the detailed answer. The discussion format is definitely more applicable to this.

[akshayjshah]

Ok, awesome - glad I could help!

[gedw99]

@akshayjshah

Can I also ask.

Take the connect demo with the psychotherapist .

Can I generate a golang client ? I did not see that anywhere in the demo.

Can the golang client be transpired to wasm ?

can the server push messages to the client . Like a chat where the psychotherapist initiates the question?

Btw I also read the docs and was confused , hence why I am asking direct use case questions rather than technical questions. Less confusing I hope.

[akshayjshah]

No problem - thanks for reading the docs before asking! Happy to help.

protoc-gen-connect-go does generate Go clients. You can see the client for the demo service here.

I'm not sure if it cross-compiles to WASM. A lot depends on whether you're talking about the standard Go toolchain's WASM target, or if you're trying to use TinyGo. We don't test or support either, but we're also not doing anything particularly unusual - as long as the standard library and google.golang.org/protobuf work, connect-go should work too.

The server can push messages to the client with a server streaming RPC. We don't have one of those defined in the demo service right now, but we'll probably add one when we release connect-web.