gRPC interface to vtctl to use

[guidoiaquinti]

Pulling this out from an internal conversation

Feature Description

Provide well-defined grpc interface to vtctl to use

Use Case(s)

We were looking at moving some of our operational tooling for Vitess to go, and we noticed that there isn’t a “true” interface into the vtctld in the protobuf definition. While there is a grpc endpoint, it’s not well defined, as it’s mainly a passthrough to all of the different vtctld methods.

For example, instead of there being a FindAllShardsInKeyspace endpoint, we instead call vtctlclient.ExecuteVtctlCommand(vtctldata.ExecuteVtctlCommandRequest{Args: []string{"FindAllShardsInKeyspace", "keyspace_name"}}) and then parse the response into our own user-defined structs, instead of having structs in the .pb.go file that we can use instead.

Quoting @sougou

I've been having similar thoughts, but right now is not a good time. The deprecation of SBR, v2 and old resharding workflows are going to drastically change the list of commands available through vtctld. We can look at doing this after all this stabilizes.

[derekperkins]

We found this out too and it makes tooling more difficult. Having a real API will also make the new UI much easier to build.

[ajm188]

This is a dupe of #7058, I'm going to close this one.