Open Stack

> -----Original Message-----
> From: Andrew Laski [mailto:andrew.laski at rackspace.com]
> Sent: Tuesday, November 12, 2013 12:07 PM
> To: OpenStack Development Mailing List (not for usage questions)
> Subject: Re: [openstack-dev] [nova][api] Is this a potential issue
> 
> On 11/11/13 at 05:27pm, Jiang, Yunhong wrote:
> >Resend after the HK summit, hope someone can give me hint on it.
> >
> >Thanks
> >--jyh
> >
> >> -----Original Message-----
> >> From: Jiang, Yunhong [mailto:yunhong.jiang at intel.com]
> >> Sent: Thursday, November 07, 2013 5:39 PM
> >> To: openstack-dev at lists.openstack.org
> >> Subject: [openstack-dev] [nova][api] Is this a potential issue
> >>
> >> Hi, all
> >> 	I'm a bit confused of followed code in ./compute/api.py, which will be
> >> invoked by api/openstack/compute/servers.py,
> _action_revert_resize().
> >> 	From the code seems there is a small windows between get the
> >> migration object and update migration.status. If another API request
> >> comes at this small window, it means two utility will try to revert resize
> at
> >> same time. Is this a potential issue?
> >> 	Currently implementation already roll back the reservation if
> >> something wrong, but not sure if we should update state to "reverting"
> as
> >> a transaction in get_by_instance_and_status()?
> 
> The migration shouldn't end up being set to 'reverting' twice because of
> the expected_task_state set and check in
> instance.save(expected_task_state=None).  The quota reservation could
> happen twice, so a rollback in the case of a failure in instance.save
> could be good.

Aha, didn't notice that's a guard. It's really cool.

--jyh

> 
> >>
> >> --jyh
> >>
> >>     def revert_resize(self, context, instance):
> >>         """Reverts a resize, deleting the 'new' instance in the
> process."""
> >>         elevated = context.elevated()
> >>         migration =
> >> migration_obj.Migration.get_by_instance_and_status(
> >>             elevated, instance.uuid, 'finished')
> >> 	>>>>>>>>>>>>>>>>>>>>>>Here we get the migration object
> >>
> >>         # reverse quota reservation for increased resource usage
> >>         deltas = self._reverse_upsize_quota_delta(context, migration)
> >>         reservations = self._reserve_quota_delta(context, deltas)
> >>
> >>         instance.task_state = task_states.RESIZE_REVERTING
> >>         instance.save(expected_task_state=None)
> >>
> >>         migration.status = 'reverting'			>>>>>>>>>>>>>>Here
> >> we update the status.
> >>         migration.save()
> >>
> >> _______________________________________________
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> >> OpenStack-dev at lists.openstack.org
> >> http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev
> >
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