[Openstack] Pondering multi-tenant needs in nova.

Jay Pipes jaypipes at gmail.com
Tue Feb 8 16:11:14 UTC 2011


Hey Paul, yeah, see what happens when you take a little time away from email? ;P

So, I'm satisfied that I've highlighted the trade-offs that come along
with Nova not "inherently understanding the relationships between
accounts".

Having an external system understand these account relationships is
fine, and the posters on this thread have done a good job explaining
the benefits that come along with federating the responsibility to an
external plugin/service, but there are some performance issues that
come along with it. However, as long as these inefficiencies are
known, I'm satisfied. :)

Cheers!
jay

On Mon, Feb 7, 2011 at 11:37 PM, Paul Voccio <paul.voccio at rackspace.com> wrote:
> Woah, seems I missed a lot by not being around email today.
>
> I was a bit confused at to why we would want to have nova trackif an
> account was being used by a reseller. In digging back through the
> blueprint associated with this, it seems the idea is for the operator (in
> this case Rackspace, but whoever) of Nova should track the idea of a
> reseller and accounts associated with that reseller. Nova itself would
> still retain the idea of a single account and the resources associated
> with that account. I guess this doesn't feel any different than another
> managed service provider who is doing add-on business on top of a amazon,
> rackspace, linode or other cloud business.
>
> https://blueprints.launchpad.net/nova/+spec/multi-tenant-accounting,
> specifically:
>
> http://wiki.openstack.org/openstack-accounting?action=AttachFile&do=view&ta
> rget=accounts.pdf
>
> While an operator *could* implement the account id as an arbitrary string
> and map inefficient queries to it as Jay mentions, I'm not sure they would
> (or even should).
>
> Jay -- I think I understand your concerns, but are you suggesting we
> implement the idea layer of resellers into Nova? Did I miss the point?
> Sorry if I'm late to the party on this one.
>
> Pvo
>
>
> On 2/7/11 8:20 PM, "Eric Day" <eday at oddments.org> wrote:
>
>>On Mon, Feb 07, 2011 at 08:50:58PM -0500, Jay Pipes wrote:
>>> Eric, you and I have a database background. I know you understand that
>>>this:
>>
>>Of course, but the first pair of queries is not as bad as a query
>>for every entity ID returned, which was in one of the previous emails
>>(the main thing I was trying to address).
>>
>>There are other indexing tricks we can do as well, but lets not bother
>>pre-optimizing in email pseudo code. :)
>>
>>-Eric
>>
>>> # Executed in the "auth service" or "configuration management
>>> database" as Jorge calls it:
>>> SELECT entity_id FROM entities
>>> WHERE user_id = <request.user_id>
>>>
>>> # Executed in the Nova database:
>>> SELECT * FROM instances
>>> JOIN instance_entity_map ON instance.id=instance_entity_map.instance_id
>>> WHERE instance_entity_map.entity_id in (<entity_ids>);
>>>
>>> is not the same as this:
>>>
>>> # Executed in the Nova database:
>>> SELECT * FROM instances
>>> JOIN instance_entity_map iem ON instance.id=iem.instance_id
>>> JOIN entities ON entities.entity_id = iem.entity_id
>>> JOIN users ON iem.user_id = <request.user_id> # This last join would,
>>> in practice, be a BETWEEN predicate on a self-join to the entities
>>> table
>>>
>>> One query on a database versus two queries (one on each database).
>>>
>>> Let's not talk about distributed join flattening as if it somehow is a
>>> single query when in fact it isn't.
>>>
>>> -jay
>>
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