Argument to NewFooClient() in generated proto code is a grpc.ClientConn struct

[zellyn]

The argument to NewFooClient() in the generated proto code (eg. pb.NewGreeterClient(conn) here) is grpc.ClientConn, a concrete struct type, rather than an interface.

This prevents us from creating stubs against our own types. We'd like to (a) create a "client" object that has a collection of connections configured from a yaml config file, and dispatches Calls to the right connection based on service name, and (b) add interception on the client side.

[dsymonds]

I'm not sure that would help, without making a truly massive interface for ClientConn. That type has a good number of internals that the grpc package uses (via, say, grpc.Invoke).

What is the bigger task you are trying to achieve? There's probably a better approach. Can you describe your goal in a bit more detail?

[zellyn]

Yeah, after posting that I noticed that the whole clientConn is passed to Invoke and NewClientStream 😞

(Our internal stubby-alike passes a "Channel" interface, which is much narrower, and I got the two mixed up.)

I think we've figured out workarounds for our use case, so I'll close this. Sorry for the noise.

[iamqizhao]

Yes, we had a lot of discussions with Go team and decided not to make ClientConn an interface (which is kinda common thing to do in other languages to support load balance channel).

I think your requirements can be addressed once we have a good client interceptor solution. You can probably summarize your requirements and put it into a comment in the designdoc of the interceptor.

[zellyn]

I created a separate doc instead.