On Thu, 2012-03-22 at 09:36 -0400, Eoghan Glynn wrote: > It's ability to easily see the remaining headroom for each > per-project quota, e.g. > > $ nova-manage quota --headroom --project=admin > ... > instances: 10 (of which 1 remaining) > floating_ips: 10 (of which 8 remaining) > ...
I recently got the quota classes stuff merged into master (after the RC branch for Essex was cut, of course). After I had completed that work, I started thinking about quotas in general, and I think there's a better way to organize how we do quotas in the first place. One potential side effect I see of that possible work would be to address this particular feature. My idea here is not really very well fleshed out or architected yet, and I have other things I'm focusing on right now (caching), but perhaps I should mention them on the list, in order to get a discussion going…and perhaps a summit discussion of the topic would be in order? The basic thought I had here was to create a "quota manager" or "quota plugin" infrastructure, instead of a bunch of fixed functions in quota.py that we use to test certain specific quotas. Having it as a plugin that you specify in configuration means you can easily substitute out the default implementation, if necessary—maybe you want quotas to be enforced across several cells instead of just one, for instance. Then, checking a quota would be a matter of simply calling a method on the quota plugin class. The side effect is that, in order to properly impose quotas in a flexible architecture, you would need to keep the quota plugin up-to-date on the current numbers of whatever resource is being limited anyway—in the example above, of having one quota applied across a number of cells, you don't want to have to ask each cell how many instances the user currently has. That makes implementation of your headroom concept pretty trivial, and I could see it implemented by attaching a little more data to the /limits endpoint's returned data. (The current quota code has to count how many instances there are each time it checks the quota; I think other parts that use quotas may do the counting themselves and just ask quota.py what the upper limit is.) -- Kevin L. Mitchell <[email protected]> _______________________________________________ Mailing list: https://launchpad.net/~openstack Post to : [email protected] Unsubscribe : https://launchpad.net/~openstack More help : https://help.launchpad.net/ListHelp
