Le 18/11/2014 20:05, Doug Hellmann a écrit :
On Nov 17, 2014, at 7:18 PM, Kevin L. Mitchell <kevin.mitch...@rackspace.com> 

On Mon, 2014-11-17 at 18:48 -0500, Doug Hellmann wrote:
I’ve spent a bit of time thinking about the resource ownership issue.
The challenge there is we don’t currently have any libraries that
define tables in the schema of an application. I think that’s a good
pattern to maintain, since it avoids introducing a lot of tricky
issues like how to manage migrations for the library, how to ensure
they are run by the application, etc. The fact that this common quota
thing needs to store some data in a schema that it controls says to me
that it is really an app and not a library. Making the quota manager
an app solves the API definition issue, too, since we can describe a
generic way to configure quotas and other applications can then use
that API to define specific rules using the quota manager’s API.

I don’t know if we need a new application or if it would make sense
to, as with policy, add quota management features to keystone. A
single well-defined app has some appeal, but there’s also a certain
amount of extra ramp-up time needed to go that route that we wouldn’t
need if we added the features directly to keystone.
I'll also point out that it was largely because of the storage needs
that I chose to propose Boson[1] as a separate app, rather than as a
library.  Further, the dimensions over which quota-covered resources
needed to be tracked seemed to me to be complicated enough that it would
be better to define a new app and make it support that one domain well,
which is why I didn't propose it as something to add to Keystone.
Consider: nova has quotas that are applied by user, other quotas that
are applied by tenant, and even some quotas on what could be considered
sub-resources—a limit on the number of security group rules per security
group, for instance.

My current feeling is that, if we can figure out a way to make the quota
problem into an acceptable library, that will work; it would probably
have to maintain its own database separate from the client app and have
features for automatically managing the schema, since we couldn't
necessarily rely on the client app to invoke the proper juju there.  If,
on the other hand, that ends up failing, then the best route is probably
to begin by developing a separate app, like Boson, as a PoC; then, after
we have some idea of just how difficult it is to actually solve the
problem, we can evaluate whether it makes sense to actually fold it into
a service like Keystone, or whether it should stand on its own.

(Personally, I think Boson should be created and should stand on its
own, but I also envision using it for purposes outside of OpenStack…)
Thanks for mentioning Boson again. I’m embarrassed that I completely forgot 
about the fact that you mentioned this at the summit.

I’ll have to look at the proposal more closely before I comment in any detail, 
but I take it as a good sign that we’re coming back around to the idea of 
solving this with an app instead of a library.

I assume I'm really late in the thread so I can just sit and give +1 to this direction : IMHO, quotas need to managed thanks to a CRUD interface which implies to get an app, as it sounds unreasonable to extend each consumer app API.

That said, back to Blazar, I just would like to emphasize that Blazar is not trying to address the quota enforcement level, but rather provide a centralized endpoint for managing reservations. Consequently, Blazar can also be considered as a consumer of this quota system, whatever it's in a library or on a separate REST API.

Last thing, I don't think that a quota application necessarly means that quotas enforcement should be managed thanks to external calls to this app. I can rather see an external system able to set for each project a local view of what should be enforced locally. If operators don't want to deploy that quota management project, it's up to them to address the hetergenous setups for each project.

My 2 cts (too),


Just my $.02…

[1] https://wiki.openstack.org/wiki/Boson
Kevin L. Mitchell <kevin.mitch...@rackspace.com>

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