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

Sean Mooney smooney at redhat.com
Mon Nov 30 19:50:22 UTC 2020

On Mon, 2020-11-30 at 18:16 +0000, Jeremy Stanley wrote:
> On 2020-11-30 10:13:00 -0800 (-0800), Michael Johnson wrote:
> [...]
> > 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
> > correctly.
> [...]
> So to be clear, you're suggesting that if someone asks for an
> instance name which can't be converted to a (legal) hostname, then
> the nova boot call be rejected outright, even though there are
> likely plenty of people who 1. (manually) align their instance names
> with FQDNs, and 2. don't use the hostname metadata anyway?
unfortunetly we cant do that even if its the right thing to do technically.

i think the path forward has to be something more like this.

1.) add a new workaround config option e.g. disable_strict_server_name_check.
    for upgrade reason it would default to true in wallaby
    when strict server name checking is disabled we will transform any malformed
    numeric  tld by replacing the '.' with '-' or by replacing the hostname with server-<uuid> as we do
    with unicode hostnames.
2.) add a new api micro versions and do one of:
   a.) reject servers with invlaid server names that contain '.' with a 400
   b.) transform server names according to the RFEs (replace all '.' and other disallowed charaters with -)
   c.) add support for FQDNs to the api.
	this coudl be something like adding a new field to store the fqdn  as a top level filed on the server.
        make hostname contain jsut the host name with the full FQDN in the new fqdn field.
        if the server name is an fqdn the the fqdn field would just be the server name.
        if the server name is the a hostname then the nova dhcp_domain will be appended to servername
        this will allow the remvoal of dhcp_domain from the compute node for config driver generateion and
        we can generate the metadat form teh new fqdn filed.
        if designate is enabled then the fqdn will be taken form the port info.
        in the metadata we will store the instance.hostname which will never be an fqdn in all local hostname keys.
        we can store teh fqdn in the public_hostname key in the ec2 metadata and in a new fqdn filed.
        this will make the values consitent and useful.
        with the new microversion we will nolonger transform the hostname except for multi-create where it will be used
        as a template i.e. <server name>-<vm index>
        TBD if the new micorversion will continue to transform unicode hostname to server-<uuid> or allow them out of scope for now.
3.) change workaround config option default to false enforcing the new behavior for old micorverions but do not remove it.
    this will enable all vm even with old clinets to have to correct behavior. of requiring the hostname to be an actul hostname
    we will not remove this workaround option going forward allowing cloud that want the old behavior to contiue to have it but
    endusers can realy on the consitent behavior by opting in to the new microverion if they have a perference.

this is a log way to say that i think we need a spec for the new api behavior that adds support for FQDN offically
whatever we decide we need to document the actually expected behavior in both the api refernce and general server careate

if we backport any part of this i think the new behavior should be disabled by default e.g. transfroming the numeric top level domain
so that the api behavior continues to be unaffected unless operators opt in to enabling it.


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