Compute manager calls DB directly

[Kyle L. Henderson]

During the course of a resize operation if the compute manager's _poll_unconfirmed_resizes() is used to automatically confirm the resize, the code path eventually tries to access the DB without going through Conductor.

The code path is something like this:

    def _poll_unconfirmed_resizes(self, context):
calls:
 self.compute_api.confirm_resize(context, instance,
                                                migration=migration)

confirm_resize contains:
        # reserve quota only for any decrease in resource usage
        deltas = self._downsize_quota_delta(context, instance)
        reservations = self._reserve_quota_delta(context, deltas)

so eventually calls:
    def _reserve_quota_delta(context, deltas, project_id=None):
        if not deltas:
            return
        return QUOTAS.reserve(context, project_id=project_id, **deltas)

quota.reserve calls the db directly:

        # Get the applicable quotas.
        # NOTE(Vek): We're not worried about races at this point.
        # Yes, the admin may be in the process of reducing
        # quotas, but that's a pretty rare thing.
        project_quotas = db.quota_get_all_by_project(context, project_id)

[Matt Riedemann (mriedem)]

(2:29:31 PM) mriedem: comstud: was just looking at this bug https://bugs.launchpad.net/nova/+bug/1293756, quotas goes directly to the database and is called from compute api, should that be going through conductor?
(2:29:54 PM) comstud: mriedem: compute API, no
(2:30:07 PM) comstud: typically it's only called from nova-api
(2:30:33 PM) comstud: there are a couple of cases where compute manager calls back to it
(2:30:50 PM) comstud: ah is ee
(2:30:53 PM) comstud: this is one of them, I guess
(2:31:03 PM) mriedem: comstud: yeah, confirming resizes
(2:31:12 PM) comstud: just switch that to use the quotas object
(2:31:31 PM) mriedem: ah, ok - was wondering about that given the quotas object stuff last week
(2:31:35 PM) mriedem: cool, easy enough, thanks
(2:31:40 PM) comstud: np

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/81099