Using ProtoBuf-net with gRPC

Question

I am trying to build a PoC at work that utilizes gRPC. The google document here takes us through a sample application. I was wondering if protobuf-net, and specifically protogen, had the capability to understand service definitions and classes necessary to perform gRPC calls? Or is this something being worked on? Would it work if I use google's protoc for client and server code generation(which involves the service definitions and RPC calls) and protobuf-net for my business objects.

Answer 1

protobuf-net.Grpc is now a thing... albeit in preview. When .NET Core 3 comes out, we should be able to make this available.

It is inspired by the WCF approach, so your service interfaces are defined via:

namespace Whatever {
    [ServiceContract]
    public interface IMyAmazingService {
        ValueTask<SearchResponse> SearchAsync(SearchRequest request);
        // ... etc
    }
}

Servers just implement the interface:

public class MyServer : IMyAmazingService {
    // ...
}

(how you host them depends on whether you're using ASP.NET Core, or the native/unmanaged gRPC libraries; both work)

and clients just request the interface:

var client = http.CreateGrpcService<IMyAmazingService>();
var result = await client.SearchAsync(query);

In the above case, this would be inferred to be the Whatever.MyAmazingService / Search service in gRPC terms, i.e.

package Whatever;
// ...
service MyAmazingService {
    rpc Search (SearchRequest) returns (SearchResponse) {}
}

but the service/method names can be configured more explicitly if you prefer. The above is a unary example; for unary operations, the result can be any of T, Task<T>, ValueTask<T> - or void / Task / ValueTask (which all map to .google.protobuf.Empty, as does a method without a suitable input parameter).

The streaming/duplex operations are inferred automatically if you use IAsyncEnumerable<T> (for some T) for the input parameter (client-streaming), the return type (server-streaming), or both (duplex).

Answer 2

It is something that I would love to get around to, but to date, no: I haven't had need to look into this, and it hasn't hit the top of my backlog. I try and keep an eye on what features people want, so it is good to know that you're after it, but today: no. Mostly this is a time thing - protobuf-net gets progressed out of my free/spare time, unless I have a genuine justification to spend "work time" on it.

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Update: I'm actively talking with the Microsoft folks who are working on gRPC for .NET, and it seems likely that we're going to try to work together here so that this becomes possible with the gRPC things in the .NET Core 3.0 timescale - meaning: we'd share an implementation of the service invocation code, but allow it to work with multiple serializer APIs.