[openstack-dev] [nova][cell] Can nova do live migration cross cells?
lvmxhster at gmail.com
Fri Jan 8 15:01:26 UTC 2016
still a question in line.
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
>>> I read up the nova cell doc.
>>> 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
>>> 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.
why get_migrations in the above link still need to route a request to a
cell database, or broadcast to all cell database?
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