[ops][nova][designate] Does anyone rely on fully-qualified instance names?

Michael Johnson johnsomor at gmail.com
Mon Nov 30 18:13:00 UTC 2020

I think we should align to the RFCs.

First thing to note is hostnames do not have the same rules as domain names.

For terminology purposes, I will use the RFC terminology:
<hostname>.<domain name>

RFC 952 [1] and RFC 1123 [2] define the valid strings for a hostname.
A short summary is alphabet (A-Z), digits (0-9), minus sign (-) up to
255 characters.

Internationalized hostnames are converted to these rules using
Punycode [3]. This is also true for domain names.

One of the most common differences between hostnames and domain names
is underscores. Underscore is invalid in a hostname, but valid in a
domain name.

So, I think I am in alignment with Sean. The hostname component should
return a 400 if there is an illegal character in the string, such as a
period. We also should use Punycode to store/handle unicode hostnames


[1] https://tools.ietf.org/html/rfc952
[2] https://tools.ietf.org/html/rfc1123#page-13
[3] https://www.rfc-editor.org/rfc/rfc3492.txt

On Mon, Nov 30, 2020 at 8:54 AM Jeremy Stanley <fungi at yuggoth.org> wrote:
> On 2020-11-30 15:16:08 +0000 (+0000), Sean Mooney wrote:
> [...]
> > so that has never actully been supported, the server name has to
> > be a hostname not a FQDN. any use of a an fqdn has never been
> > intended to be supproted.
> [...]
> > techinally you can set an fqdn in /etc/hostname but its discuraged
> [...]
> Yes, we directly set /etc/hostname to contain the "short" hostname
> and set the FQDN in /etc/hosts as an alias for it bound to a
> (secondary) v4 loopback consistent with the default configurations
> for Debian/Ubuntu systems. We don't rely on hostname metadata or
> cloud-init to provide correct representations, as cloud providers
> like to mess around with things like default domains and that leads
> to an inconsistent experience across different environments.
> --
> Jeremy Stanley

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