NIO's connect errors make it impossible to know what it actually tried to connect to

[weissi]

For example if you get a ChannelError.connectTimeout(...) from Channel.connect(host: "foo.com", port: 1234) you don't get told what address(es) NIO actually resolved and tried to connect to. Also, the HappyEyeballsConnector also throws ChannelError.connectTimeout(...) when it times out resolving.

That's quite problematic.

I know that it would be source breaking if NIO just started throwing different errors but to alleviate this we could have a ClientBootstrap (etc) property bootstrap.useModernErrors(true) or similar to opt into better errors.

[weissi]

Ah, I think it's kinda weird:

• If you connect to host:port: and ...
  • ... the DNS resolution worked but the connect failed, you get a good error (NIOConnectionError) with all detais
  • ... the DNS resolution itself took longer than the connect timeout you get ChannelError.connectTimeout(...)
• If you connect to a SocketAddress and the connect times out you get a ChannelError.connectTimeout(...)

[Lukasa]

Yeah, opting into better errors here is definitely valuable.