[nova] Does anyone remember why server_group_members quota is enforced at the user rather than project level?

Jay Pipes jaypipes at gmail.com
Wed Mar 13 14:41:17 UTC 2019

On Mon, Mar 11, 2019 at 4:10 PM melanie witt <melwittt at gmail.com> wrote:

> On Thu, 7 Mar 2019 09:08:46 -0600, Matt Riedemann <mriedemos at gmail.com>
> wrote:
> > Change [1] in Juno added the server_groups and server_group_members
> quotas.
> >
> > Server group quota is counted per project and user [2].
> >
> > Server group member quota is only counted per group and user [3].
> >
> > The question coming up in IRC today is why is the server group member
> > count not also constrained by project? Or is project implied since the
> > member count is within the scope of a group, which is itself per-project?
> >
> > Note that the original change that added these quotas said, "They can be
> > defined per project or per user within a project".
> When it says, "they can be defined per project or per user within a
> project," that means the quota _limit_ can be defined per project or per
> user. Which means, you can define a quota of 100 server group members
> for anyone in project A, but could restrict user B in project A to only
> 10 server group members, if you wanted to. So, the quota limit is
> definable per project or per project + user.
> This is different than how the server group members are counted. As you
> pointed out, server group members are counted only per user, not per
> project. I don't know the reasoning behind it either. It might be like
> you speculated, that since server groups are owned by a project, then
> server group members have a project implied.
> > Given none of the people that originally added this are around still
> > maintaining it, nor was there a spec (we didn't have specs in Juno),
> > we're left to guess as to the reasons.
> >
> > If we changed the server_group_members quota enforcement to count per
> > group/project/user, would that break anything?
> It would behave differently, but I'm not aware of anything that would
> break. When we talked about moving nova to unified limits, I think the
> plan was to change any existing per-user counts to count by project
> instead (along with deprecating any per-user quota limit setting). I
> think that server group members and key pairs are the only two that
> count by user only, today.

Yep, and IMHO, keypairs is the one and only valid user-specific limit.

A quota on server group members just never really made any sense to me to
begin with. a) making it per-user doesn't make much sense and b) this is a
perfect example of using quotas as a poor man's rate-limiting middleware
(just like having quotas on any "resource" that is essentially just a
record in a database -- i.e. any of the quotas on things like metadata

We should just get rid of the server group and server group members quotas
entirely, IMHO.

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