Renaming Instance Name doesn't change hostname on a Rebuild

[Antony Messerli]

Renaming an instance name via novaclient only changes the display_name, it doesn't actually update the hostname or display_description in the instances table.

This means if I want to change the name of an instance, and then rebuild it, it will utilize the original name as set in hostname.

Renaming an instance name should also update the other fields.

[Vish Ishaya (vishvananda)]

display_description should stay as it can be updated separately, but updating name should update hostname using the same logic that creating a server does.

We may need to add a new codepath if we want the name changed in dnsmasq as well.

[Thierry Carrez (ttx)]

Could you point to the commit that actually fixes this ?

[Sumanth Nagadavalli (sumanth-nagadavalli)]

The bug description is still seen. Assigning it to myself.

Is the expected behavior just to update the other fields (hostname, display_description) in instances table? Or should it also change the hostname inside the vm?

[Scott Adkins (adkinss)]

My preference would be to see a renamed VM only update the hostname and display_name fields and NOT the display_description field. Also, I would not expect Nova to make changes inside a VM after it has been built. What I would expect is that when a VM is rebuilt, the new hostname would be applied to that VM and not the original hostname. I did some testing in a Havana environment and found that updating the hostname field in addition to display_name seems to fix the bug just fine.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/100125

[Sean Dague (sdague)]

Patch stalled

[OpenStack Infra (hudson-openstack)]

Change abandoned by Sean Dague (<email address hidden>) on branch: master
Review: https://review.openstack.org/100125
Reason: This review is > 4 weeks without comment, and failed Jenkins the last time it was checked. We are abandoning this for now. Feel free to reactivate the review by pressing the restore button and leaving a 'recheck' comment to get fresh test results.

[Davanum Srinivas (DIMS) (dims-v)]

Removing "In Progress" status

[Davanum Srinivas (DIMS) (dims-v)]

as there is no pending review

[Chris Gacsal (chris-gacsal)]

I have recently started to work on this bug and going to reopen the Neill's abandoned patchset.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/170130

[OpenStack Infra (hudson-openstack)]

Change abandoned by Michael Still (<email address hidden>) on branch: master
Review: https://review.openstack.org/170130
Reason: This patch has been stalled for quite a while, so I am going to abandon it to keep the code review queue sane. Please restore the change when it is ready for review.

[Davanum Srinivas (DIMS) (dims-v)]

No updates since 02/26

[Tracy Jones (tjones-i)]

i'll rebase this patch and give it a shot

[Tracy Jones (tjones-i)]

I just retested this on upstream master (devstack) and it worked. The steps I took are

1. create an instance
2. change the name
3. rebuild

the changed name were still there after the rebuild. Did you do some other steps? If not, this may have been fixed by a subsequent patch

[Matt Riedemann (mriedem)]

Per comment 15, I don't think that's what the bug is saying, or requesting. Yes you can rename the instance and rebuild it and the new instance has the same display_name, but the hostname is not changed, and is the same as the original instance, I've recreated with a newton devstack:

http://paste.openstack.org/show/494464/

The question is if we should rename the hostname in the guest when rebuilding it. Maybe that needs to be a parameter on the rebuild API since we preserve the IP network settings and storage for the instance through the rebuild, so changing the hostname could mess with anything that's relying on that to be unchanged through the rebuild.

[Matt Riedemann (mriedem)]

Note in my recreate that the nic doesn't change:

2001:db8::7, 172.24.4.6

So I think changing the hostname during rebuild, at least by default, is wrong.

[Matt Riedemann (mriedem)]

Melanie Witt also makes good points in the old review https://review.openstack.org/#/c/170130/:

melanie witt
May 5, 2015

Patch Set 5: Code-Review-1

The weird thing about this is, it allows one to update the "hostname" of the instance before it is actually using that hostname (and may potentially never use it, if it is never rebuilt). I was also concerned whether the guest will actually consume the hostname from metadata again when rebuilt. I assume from your patch that it does, since virt domain is destroyed and recreated during a rebuild.

Also mentioned in the bug report, what about updating in dnsmasq? Point being, I don't think updating the hostname is as simple and would take more work to change it in the db, make the guest take the new name (without a rebuild or anything), update it in dnsmasq, etc.

--

So I think this is definitely a bigger API change and would require a spec to consider the impact of a change in behavior like this.

See https://specs.openstack.org/openstack/nova-specs/readme.html for submitting a spec.