Support streaming calls in the `SubchannelCallTracker`

What version of gRPC and what language are you using?

Grpc.AspNetCore v2.53.0 in C#

What operating system (Linux, Windows,…) and version?

Mac OSX Ventura

What runtime / compiler are you using (e.g. .NET Core SDK version dotnet --info)

.NET 7.0.200

What did you do?

I wrote a custom load balancer for client side load balancing. I used the ISubchannelCallTracker interface to detect when calls happen and complete on a subchannel to know what load they are bearing. This works fine for non-streaming grpc-calls, but it breaks down for streaming-calls.

What did you expect to see?

That the Complete-function of the ISubchannelCallTracker is called once the AsyncServerStreamingCall is disposed in the user-code.

What did you see instead?

The Complete-function is called right after the grpc-call is made, before even the first item is retriebed from the ResponseStream via MoveNext.

Thoughts

I saw this comment in the source and wondered what it would take to handle this case correctly. AsyncServerStreamingCall does have a disposeAction already, but its not clear how it relates to the HttpResponseMessage in the other place and what else needs to be thought of. I would be happy to provide a PR if I could get some pointers.

[JamesNK]

Thank you for creating a PR.

I need to test this thoroughly and write unit tests. I’m sure it works for calls that successfully read to the end of the request. This is what you probably tested. But I want to verify calls are correctly ended for failure conditions. Does it still work if the gRPC call ends because of cancellation? Or deadline. Or server abort. Or someone doesn’t read from the stream, and it times out. And so on.

[JamesNK]

I don’t believe this is possible without changes to HttpClient.