gRPC Client Telemetry - Ability to filter by Grpc Client

[Simonl9l]

TBH I'm still trying to fully understand the capabilities, so please excuse any ignorance.

It would be great to have the ability to disable trace capture for any given gRPC Client, ether one the client of more generally as part of the provider setup.

I note that the Http Client via .AddHttpClientInstrumentation(c => c.FilterHttpRequestMessage = FilterHttpRequestMessage) allows one to filer specific requests, and whist the gRPC Client implementation appears to be built upon this, and I can filter the HTTP aspect, I can't it seems suppress the gRPC calls.

I also looked at the .AddGrpcClientInstrumentation(opt => opt.SuppressDownstreamInstrumentation = true) but this seems have issues per #1727

I've also attempted to implement a gRPC client Interceptor (given hints from here), but seem the Current Activity is null so it does nothing:

public class ClientTraceInterceptor : Interceptor
{
    public override AsyncUnaryCall<TResponse> AsyncUnaryCall<TRequest, TResponse>(
            TRequest request,
            ClientInterceptorContext<TRequest, TResponse> context,
            AsyncUnaryCallContinuation<TRequest, TResponse> continuation)
    {
        var activity = Activity.Current;
 
        if (activity is not null)
        {
            activity.ActivityTraceFlags &= ~ActivityTraceFlags.Recorded;
            activity.IsAllDataRequested = false;
        }
 
        Activity.Current = null;
        
        var call = continuation(request, context);

        return new AsyncUnaryCall<TResponse>(
            HandleResponse(call.ResponseAsync),
            call.ResponseHeadersAsync,
            call.GetStatus,
            call.GetTrailers,
            call.Dispose);
    }
    private static async Task<TResponse> HandleResponse<TResponse>(Task<TResponse> inner)
    {
        try
        {
            return await inner;
        }
        catch (Exception ex)
        {
            throw new InvalidOperationException("Custom error", ex);
        }
    }
}

My use case, is that I have internal gRPC activity from one gRPC client that is not on the hot path, and only want to show traces for what is actually hot path via other gRPC clients.