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["Dr. Jens Harbott" <1861401@xxxxxxxxxxxxxxxxxx>]

DNS is expected to match the hostname of an instance, which according to
nova above is immutable. If you want an instance with a different
hostname, you need to create a new one.

** Changed in: neutron
       Status: New => Invalid

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https://bugs.launchpad.net/bugs/1861401

Title:
  Renaming instance brokes DNS integration

Status in neutron:
  Invalid
Status in OpenStack Compute (nova):
  Opinion

Bug description:
  Colleagues,

  Description
  ===========
  Renaming instance (e.g. using "openstack server set --name") brokes DNS integration, since it makes it impossible to bind port with new instance's name. So, if user renamed instance and want to access it using name, he can not.

  Steps to reproduce
  ==================
  1) You have an instance with some name (e.g. "web01")

  2) You rename it using "openstack server set --name web02 web01"

  3) You create port with instance's new name (e.g. web02) in order to attach it to the instance
  $ openstack port create --network e-net --fixed-ip subnet=e-subnet --dns-name web02 test_port

  4) You're trying to attach the port to the instance:
  $ nova interface-attach --port-id <uuid> web02

  Expected result
  ===============
  Port binds to the instance and instance can be accessed using hostname "web02"

  Actual result
  =============
  Last command in steps above fails with the following message:

  ERROR (ClientException): Unexpected API Error. Please report this at
  http://bugs.launchpad.net/nova/ and attach the Nova API log if
  possible.

  Nova log says the following:

  2020-01-30 11:43:32.652 17476 ERROR nova.api.openstack.wsgi
  PortNotUsableDNS: Port 0425701f-d958-4c81-931a-9594fba7d7d2 not usable
  for instance 2d49b781-cef5-4cdd-a310-e74eb98aa514. Value web02
  assigned to dns_name attribute does not match instance's hostname
  web01

  MySQL content show that renaming instance changed column
  "display_name", but "hostname" remained with old name:

  mysql> select hostname, display_name from instances where uuid='2d49b781-cef5-4cdd-a310-e74eb98aa514';
  +----------+--------------+
  | hostname | display_name |
  +----------+--------------+
  | web01    | web02        |
  +----------+--------------+

  Thus, DNS integration compares port's dns_name to "hostname" not the
  "display_name", which makes it unusable after renaming instance.
  Either renaming instance need to change both "hostname" and
  "display_name" columns or DNS integration need compare port's dns_name
  with "display_name".

  Environment
  ===========
  Host OS: Ubuntu 18.04 LTS
  Openstack: Rocky
  $ dpkg -l |grep nova
  ii  nova-api           2:18.2.3-0ubuntu1~cloud0
  ii  nova-common        2:18.2.3-0ubuntu1~cloud0
  ii  nova-conductor     2:18.2.3-0ubuntu1~cloud0
  ii  nova-novncproxy    2:18.2.3-0ubuntu1~cloud0
  ii  nova-placement-api 2:18.2.3-0ubuntu1~cloud0
  ii  nova-scheduler     2:18.2.3-0ubuntu1~cloud0
  ii  python-nova        2:18.2.3-0ubuntu1~cloud0
  ii  python-novaclient  2:11.0.0-0ubuntu1~cloud0

  Thank you.

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