Proposal: Fix inconsistent DNS driver API implementations

[aaron-sierra]

Summary

While comparing the LuaDNS driver to other DNS drivers, I noticed that there are a number of subtly incompatible implementations sharing an otherwise common API which limit portability between providers.

For example, some drivers use empty strings to represent apex/naked records (e.g. example.com.), while others use None. Both categories of drivers employ explicit unit testing to confirm their preferred Record.name value.

Similarly, some drivers want Record.name as a rooted FQDN (e.g. "host.example.com."), others as an unrooted FQDN (e.g. "host.example.com"), and still others as a bare host name (e.g. "host").

Proposal

Assuming that the libcloud DNS class/driver APIs are intended to provide a consistent interface for users and drivers should provide logic within themselves to adapt the common objects and interfaces for their respective services, I propose the following:

1. Add common logic to the Record class to standardize apex/naked record names on the empty string (or None).
2. Add common logic to the Record class to enforce that .name represents the host name, without the domain suffix. This would likely involve adding new .fqdn and .hostname properties to expose rooted and unrooted FQDN strings, respectively.
   • For the sake of compatibility with existing uses, __init__() would accept a rooted/unrooted FQDN, a bare host name, or None.
3. Refactor Record.update() to leverage common code to enforce the items above, while being kind to existing users.
4. Expand DNS driver unit tests to validate data sent to the provider. Presently, it appears that testing primarily validates the formatting of (canned) responses received from a provider.