[openstack-dev] [nova] [neutron] Should we continue providing FQDNs for instance hostnames?

Gary Kotton gkotton at vmware.com
Tue Sep 5 06:18:39 UTC 2017

On 9/4/17, 3:47 PM, "Stephen Finucane" <stephen at that.guru> wrote:

    On Mon, 2017-09-04 at 11:51 +0000, Gary Kotton wrote:
    > On 9/4/17, 11:18 AM, "Stephen Finucane" <sfinucan at redhat.com> wrote:
    > > Nova has a feature whereby it will provide instance host names that cloud-
    > > init can extract and use inside the guest, i.e. this won't happen without
    > > cloud-init. These host names are fully qualified domain names (FQDNs) based
    > > upon the instance name and local domain name. However, as noted in bug
    > > #1698010 [1], the domain name part of this is based up nova's 'dhcp_domain'
    > > option, which is a nova-network option that has been deprecated [2].
    > >     
    > > I've started work on a fix [3] that will allow us to retrieve this
    > > information from neutron instead, uncoupling us from this legacy option.
    > > However, some commentators have pointed out that this may not necessarily 
    > > be what we want to do: a FQDN is a hostname and domain name, and using one 
    > > as a hostname may not be that clever nor correct.
    > >
    > > My networking fu isn't strong enough to deliver a verdict so I'm hoping
    > > someone else can make my mind up for me: do we want to migrate this feature
    > > to neutron, or do we want to stop using FQDN and just use instance names?
    > Hi,
    > Your patch https://review.openstack.org/#/c/480616/ requires that neutron
    > expose the ‘DNS Integration’ extension be support by neutron and the relevant
    > networking plugin. If it does not then will be a regression and things will
    > not work.
    > In addition to this that is per network and not global so there will also be
    > a regression for running instances if nova is updated.
    OK, so ultimately this isn't something we can rely on from neutron?
[Gary] No, you can rely on it from Neutron – you just need to be aware that if the extension is supported then it can be used. If not then you should continue to use the existing configuration vaiable

 Does that
    mean we should abandon the idea of providing FQDN when using neutron? Mores to
    the original point, is there any reason we would want to/should use FQDN?

[Gary] Yes, we should support this. Applications make use of this and hence the support
    > > [1] https://bugs.launchpad.net/nova/+bug/1698010
    > > [2] https://review.openstack.org/#/c/395683/
    > > [3] https://review.openstack.org/#/c/480616/

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