Better host resolving errors handling (Channel isn't ready.)

[alex-vasenin-peggy]

Guys, I spent an hour figuring out the cause of the following error:

unavailable: "Channel isn't ready."

Turns out, instead of this:

let transport = try! HTTP2ClientTransport.TransportServices(target: .dns(host: "grpc.mydomain.com"), transportSecurity: .tls)

I've been using this:

let transport = try! HTTP2ClientTransport.TransportServices(target: .ipv4(host: "grpc.mydomain.com"), transportSecurity: .tls)

If you expect only IPv4 address in .ipv4(host:) you should crash (or throw) if you get something else, and frankly .ipv4(address:) communicates the idea much better. Sorry for venting out.

[glbrntt]

That's valuable feedback, thanks. I agree the naming here is bad.

I've opened #117 to deprecate that API and replace it with a better spelling (address) and also to check that the value passed in is a valid IP address in debug builds to provide a better error otherwise.

[alex-vasenin-peggy]

Thank you, that's very helpful! 👍