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On Thu, Mar 31, 2016 at 10:39 AM, Matt Riedemann
<mriedem at linux.vnet.ibm.com> wrote:
>
>
> On 3/30/2016 8:20 PM, Matt Riedemann wrote:
>>
>>
>>
>> On 3/30/2016 7:56 PM, Matt Riedemann wrote:
>>>
>>>
>>>
>>> On 3/30/2016 7:38 PM, Matt Riedemann wrote:
>>>>
>>>>
>>>>
>>>> On 2/25/2016 5:31 AM, Takashi Natsume wrote:
>>>>>
>>>>> Hi Nova and Cinder developers.
>>>>>
>>>>> As I reported in a bug report [1], nova swap volume
>>>>> (updating an attached volume) fuction does not work
>>>>> in the case of non admin users by default.
>>>>> (Volumes are stuck.)
>>>>>
>>>>> Before I was working for fixing another swap volume bug [2][3].
>>>>> But Ryan fixed it on the Cinder side [4].
>>>>> As a result, admin users can execute swap volume function,
>>>>> but it was not fixed in the case of non admin users.
>>>>> So I reported the bug report [1].
>>>>>
>>>>> In the patch[5], I tried to change the default cinder's policy
>>>>> to allow non admin users to execute migrate_volume_completion API.
>>>>> But it was rejected by the cinder project ('-2' was voted).
>>>>>
>>>>> In the patch[5], it was suggested to make the swap volume API admin
>>>>> only
>>>>> on the Nova side.
>>>>> But IMO, the swap volume function should be allowed to non admin users
>>>>> because attaching a volume and detaching a volume can be performed
>>>>> by non admin users.
>>>>
>>>>
>>>> I agree with this. DuncanT said in IRC that he didn't think non-admin
>>>> users should be using the swap-volume API in nova because it can be
>>>> problematic, but I'm not sure why, is there more history or detail
>>>> there? I'd think it shouldn't be any worse than doing a detach/attach in
>>>> quick succession (like in a CI test for example).
>>>>
>>>>>
>>>>> If migrate_volume_completion is only allowed to admin users
>>>>> by default on the Cinder side, attaching a new volume and
>>>>> detaching an old volume should be performed on the Nova side
>>>>> when swapping volumes.
>>>>
>>>>
>>>> My understanding of the problem is as follows:
>>>>
>>>> 1. Admin-initiated volume migration in Cinder calls off to Nova to
>>>> perform the swap-volume, and then Nova calls back to Cinder's
>>>> migrate_volume_completion API. This is fine since it's an admin that
>>>> initiated this series of operations on the Cinder side (that's by
>>>> default, however, this is broken if the policy file for Cinder is change
>>>> to allow non-admins to migrate volumes).
>>>>
>>>> 2. A non-admin swap-volume API call in Nova fails because Nova blindly
>>>> makes the migrate_volume_completion call to Cinder which fails with a
>>>> 403 because the Cinder API policy has that as an admin action by
>>>> default.
>>>>
>>>> I don't know the history around when the swap-volume API was added to
>>>> Nova, was it specifically for this volume migration scenario in Cinder?
>>>>   Are there other use cases?  Knowing those would be good to determine
>>>> if Nova should change it's default policy for swap-volume, although,
>>>> again, that's only a default and can be changed per deployment so we
>>>> probably shouldn't rely on it.
>>>>
>>>> Ideally we would have implemented this like the nova/neutron server
>>>> events callback API in Nova during vif plugging (nova does the vif plug
>>>> on the host then waits for neutron to update it's database for the port
>>>> status and sends an event (API call) to nova to continue booting the
>>>> server). That server events API in nova is admin-only by default and
>>>> neutron is configured with admin credentials for nova to use it.
>>>>
>>>> Another option would be for Nova to handle a 403 response when calling
>>>> Cinder's migrate_volume_completion API and ignore it if we don't have an
>>>> admin context. This is pretty hacky though. It assumes that it's a
>>>> non-admin user initiating the swap-volume operation. It wouldn't be a
>>>> problem for the volume migration operation initiated in Cinder since by
>>>> default that's admin-only, so nova shouldn't get a 403 when calling
>>>> migrate_volume_completion. The trap would be if the cinder policy for
>>>> volume migration was changed to allow non-admins, but if someone did
>>>> that, they should also change the policy for migrate_volume_completion
>>>> to allow non-admin too.
>>>>
>>>>>
>>>>> If you have a good idea, please let me know it.
>>>>>
>>>>> [1] Cinder volumes are stuck when non admin user executes nova swap
>>>>> volume API
>>>>>      https://bugs.launchpad.net/cinder/+bug/1522705
>>>>>
>>>>> [2] Cinder volume stuck in swap_volume
>>>>>      https://bugs.launchpad.net/nova/+bug/1471098
>>>>>
>>>>> [3] Fix cinder volume stuck in swap_volume
>>>>>      https://review.openstack.org/#/c/207385/
>>>>>
>>>>> [4] Fix swap_volume for case without migration
>>>>>      https://review.openstack.org/#/c/247767/
>>>>>
>>>>> [5] Enable volume owners to execute migrate_volume_completion
>>>>>      https://review.openstack.org/#/c/253363/
>>>>>
>>>>> Regards,
>>>>> Takashi Natsume
>>>>> NTT Software Innovation Center
>>>>> E-mail: natsume.takashi at lab.ntt.co.jp
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>> __________________________________________________________________________
>>>>>
>>>>>
>>>>>
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>>>>>
>>>>
>>>
>>> I also just checked Tempest and apparently we have no coverage for the
>>> swap-volume API in Nova, we should fix that as part of this.
>>>
>>
>> I've done some more digging. The swap-volume functionality was added to
>> nova here [1].  The cinder use of it for volume migration was added here
>> [2].
>>
>> Looking at the cinder volume API for migrate_volume_completion, it
>> expects the source (old) volume to have migration_status set [3].
>>
>> So, I think we can easily fix this in Nova by simply not calling
>> volume_migration_completion if old_volume['migration_status'] is None.
>>
>> [1]
>>
>> https://github.com/openstack/nova/commit/8f51b120b430c7c21399256f37e1d8f75d030484
>>
>> [2]
>>
>> https://github.com/openstack/nova/commit/0e4bd7f93b9bfadcc2bb6dfaeae7bb5ee00c194b
>>
>> [3]
>>
>> http://git.openstack.org/cgit/openstack/cinder/tree/cinder/volume/api.py#n1358
>>
>>
>
> Of course that had to be too easy to be true. The volume 'migration_status'
> is only returned for the volume details if you're calling with an admin
> context [1].
>
> I think we can still use this, we just can't expect
> volume['migration_status'] to be in the response from the volume GET. If
> it's not there, we can assume we're not doing a migration and we're not an
> admin anyway, so we can't call migrate_volume_completion.

So in that case, we need to attach, detach volume on nova side right?
I mean if migrate_volume_completion is not being called then
new volume attachment and old volume detachment should be initiated explicitly.

Can we make Nova default policy same as cinder, i mean swap volume
allowed only for admin? Because if there is simple swap initiated from
nova(not cinder migration), Nova allow that operation for non-admin
user and get stuck to attaching/detaching status.

>
> [1]
> http://git.openstack.org/cgit/openstack/cinder/tree/cinder/api/v2/views/volumes.py#n82-L84
>
> --
>
> Thanks,
>
> Matt Riedemann
>
>
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