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[Bug 1621582] [NEW] use_usb_tablet and pointer_model have different defaults making switching hard

 

Public bug reported:

The use_usb_tablet config option is deprecated in Newton and replaced
with the pointer_model config option. The use_usb_tablet option defaults
to True, and pointer_model defaults to None, and the only choices are
None and 'usbtablet'.

If pointer_model is not set, then use_usb_tablet is used as a fallback
while transitioning to the new pointer_model option.

The problem is they have different default values/behaviors.

Currently devstack sets use_usb_tablet=False, which gives us warnings in
CI runs because the option is deprecated. But changing it to None will
make the nova code fallback to CONF.use_usb_tablet:

https://github.com/openstack/nova/blob/df15e467b61fee781e78b07bf910d6b411bafd44/nova/virt/libvirt/driver.py#L4541

So you can't just remove using use_usb_tablet if you want it disabled
(set to False) because the code will use the default and set it to True.

I tried setting pointer_model to '' to get around the None check in the
nova code, but that fails because we're using choices with the config
option so only None and 'usbtablet' are allowed:

http://logs.openstack.org/26/367526/1/check/gate-tempest-dsvm-neutron-
full-ubuntu-
xenial/1479bdd/logs/screen-n-api.txt.gz?level=TRACE#_2016-09-08_17_31_42_490

This makes the transition from use_usb_tablet to pointer_model hard for
anyone that wants this set to False like devstack does.

We could allow setting '' as a choice for pointer_model to workaround
this until use_usb_tablet is gone. We could also default use_usb_tablet
to False to mimic pointer_model, but that's a change in default behavior
without any warning for a release.

We could also just ignore this and drop use_usb_tablet in Ocata and
anyone that was setting it in nova.conf will just not have it picked up
and used, but that's annoying for anyone that wants to get ahead of
cleaning out deprecation warnings before upgrading to ocata.

** Affects: nova
     Importance: Undecided
         Status: Confirmed

** Changed in: nova
       Status: New => Confirmed

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https://bugs.launchpad.net/bugs/1621582

Title:
  use_usb_tablet and pointer_model have different defaults making
  switching hard

Status in OpenStack Compute (nova):
  Confirmed

Bug description:
  The use_usb_tablet config option is deprecated in Newton and replaced
  with the pointer_model config option. The use_usb_tablet option
  defaults to True, and pointer_model defaults to None, and the only
  choices are None and 'usbtablet'.

  If pointer_model is not set, then use_usb_tablet is used as a fallback
  while transitioning to the new pointer_model option.

  The problem is they have different default values/behaviors.

  Currently devstack sets use_usb_tablet=False, which gives us warnings
  in CI runs because the option is deprecated. But changing it to None
  will make the nova code fallback to CONF.use_usb_tablet:

  https://github.com/openstack/nova/blob/df15e467b61fee781e78b07bf910d6b411bafd44/nova/virt/libvirt/driver.py#L4541

  So you can't just remove using use_usb_tablet if you want it disabled
  (set to False) because the code will use the default and set it to
  True.

  I tried setting pointer_model to '' to get around the None check in
  the nova code, but that fails because we're using choices with the
  config option so only None and 'usbtablet' are allowed:

  http://logs.openstack.org/26/367526/1/check/gate-tempest-dsvm-neutron-
  full-ubuntu-
  xenial/1479bdd/logs/screen-n-api.txt.gz?level=TRACE#_2016-09-08_17_31_42_490

  This makes the transition from use_usb_tablet to pointer_model hard
  for anyone that wants this set to False like devstack does.

  We could allow setting '' as a choice for pointer_model to workaround
  this until use_usb_tablet is gone. We could also default
  use_usb_tablet to False to mimic pointer_model, but that's a change in
  default behavior without any warning for a release.

  We could also just ignore this and drop use_usb_tablet in Ocata and
  anyone that was setting it in nova.conf will just not have it picked
  up and used, but that's annoying for anyone that wants to get ahead of
  cleaning out deprecation warnings before upgrading to ocata.

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