[openstack-dev] [nova][api] Is this a potential issue
Andrew Laski
andrew.laski at rackspace.com
Tue Nov 12 20:07:19 UTC 2013
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.
>>
>> --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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>
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