channelz: Exposing channelz data for clients that are not servers

[Jille]

Use case(s) - what problem will this feature solve?

I want to expose channelz information on the debug port of each of my processes.
For servers this is feasible, I register the channelz service on my *grpc.Server and point the UI to use that.
For processes that don't host a gRPC server, I can't access the information.

Proposed Solution

Expose the internal APIs used by https://github.com/grpc/grpc-go/blob/v1.78.0/channelz/service/service.go#L42

Alternatives Considered

1. I could run a server on a random port from all my processes, but that has security implications.
2. I could implement something that implements grpc.ServiceRegistrar so I can extract google.golang.org/grpc/channelz/service.serverImpl{} and do calls on that.

Additional Context

I'm using github.com/rantav/go-grpc-channelz to render a UI

[easwars]

The RegisterChannelzServiceToServer API that you pointed to also accepts a grpc.ServiceRegistrar. How do you plan to implement that interface on processes where you don't run a server?

Also, there is already a way to do this using the admin package: https://github.com/grpc/grpc-go/blob/v1.78.0/admin/admin.go#L56.

github.com/rantav/go-grpc-channelz also talks about using a grpc server to register the channelz service on. That is what I see here: https://pkg.go.dev/github.com/rantav/go-grpc-channelz#CreateHandler

[Jille]

The RegisterChannelzServiceToServer API that you pointed to also accepts a grpc.ServiceRegistrar. How do you plan to implement that interface on processes where you don't run a server?

Horribly: Implement a struct with RegisterService(desc *ServiceDesc, impl any) that ignores desc and type-asserts impl to grpc_channelz_v1.ChannelzServer.
Note that was in my Alternatives Considered section, to illustrate the awfulness of having to work around a nice public API.

Also, there is already a way to do this using the admin package: https://github.com/grpc/grpc-go/blob/v1.78.0/admin/admin.go#L56.

I'm not sure what you mean by this. The admin package only provides mass registering of useful services, no?

github.com/rantav/go-grpc-channelz also talks about using a grpc server to register the channelz service on. That is what I see here: https://pkg.go.dev/github.com/rantav/go-grpc-channelz#CreateHandler

Yeah. Once a public API exists we could edit packages like go-grpc-channelz to use it, if there's no gRPC server available.

[easwars]

I'm not sure what you mean by this. The admin package only provides mass registering of useful services, no?

There are only two services though at this point in time. One is channelz and the other one is CSDS which is related to xDS.

[github-actions]

This issue is labeled as requiring an update from the reporter, and no update has been received after 6 days. If no update is provided in the next 7 days, this issue will be automatically closed.

[Jille]

Is there anything else from me needed?