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still a question in line.
Thanks.

2016-01-08 21:53 GMT+08:00 Andrew Laski <andrew at lascii.com>:

> On 01/08/16 at 12:33pm, John Garbutt wrote:
>
>> On 8 January 2016 at 08:17, 少合冯 <lvmxhster at gmail.com> wrote:
>>
>>> Hi, all
>>>
>>> Now I'm working on the migrations list/show API.
>>> The new api defines  migrations is a sub-collection of an instance.
>>> GET   v2.1/tenant_id/servers/server-id/migrations/migration-id
>>>
>>> I need to support  the new cell API to get a migration of a specified
>>> instance.
>>> get_migration_by_instance_and_id
>>>
>>> I read up the nova cell doc.
>>> http://docs.openstack.org/developer/nova/cells.html
>>>
>>> It tells us that, the migrations table will be API-level.
>>> The instances table is Cell-level.
>>> So does that means that we can do live migration cross cells?
>>>
>>
>> In sort, you can't currently live-migrate between cells.
>>
>> So there is the current cells v1. When using cells v1 you will never
>> be able to move between cells. In addition, when using nova-network,
>> network assumptions generally mean IPs can't move between cells.
>>
>
> Assuming a global network the limitation is just within Nova.  There is no
> mechanism for moving instance data from one cell database to another.  And
> it's not something that will be added since v1 is in a freeze.
>
>
>> In cells v2, we were talking about ways that could happen. Its still
>> hard, because you would need to copy the instance record between one
>> cell database to another, with the API understanding how the move is
>> going. Complexity best avoided, if possible.
>>
>
> Cells v2 makes some architecture choices that will make it easier to
> accomplish this.  But it's not necessary to have for cells v2 so it's not
> likely to be in place initially.
>
>
>> And also this will affect my code.
>>> If the migrations is API-level, so I do not need a cell name to get the
>>> migrations info from DB.
>>>
>>> Or I need to get the cell name by the specified instance, and then get
>>> the
>>> migrations info by _TargetedMessage.
>>>
>>
>> Afraid I don't have enough context from the rest of your email to
>> answer these questions.
>>
>
> I'm not entirely clear on the question either, but if the migration is in
> the api level database then you do not need a cell name to get the
> migration from the db.  The cell name is only used to route a request to a
> cell database.
>

still puzzle the current nova code.
https://github.com/openstack/nova/blob/master/nova/cells/messaging.py#L1668
https://github.com/openstack/nova/blob/master/nova/cells/messaging.py#L1330

why get_migrations in the above link still need to route a request  to a
cell database, or broadcast to all cell database?


>
>> Thanks,
>> John
>>
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>
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