max_net_count doesn't interact properly with min_count when booting multiple instances

[Chris Friesen]

In compute.api.API._create_instance() we have a min_count that is optionally passed in by the end user as part of the boot request.

We calculate max_net_count based on networking constraints.

Currently we error out if max_net_count is zero, but we don't check it against min_count. If the end user specifies a min_count that is greater than the calculated max_net_count the resulting error isn't very useful.

We know that min_count is guaranteed to be at least 1, so we can replace the existing test against zero with one against min_count. Doing this gives a much more reasonable error message:

controller-0:~$ nova boot --image myimage --flavor simple --min-count 2 --max-count 3 test
ERROR (Forbidden): Maximum number of ports exceeded (HTTP 403) (Request-ID: req-f7ff28bf-5708-4cbf-a634-2e9686afd970)

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/283861

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/283861
Committed: https://git.openstack.org/cgit/openstack/nova/commit/?id=e015a98b9e99dca7b97e97bb48af4392fd34dddb
Submitter: Jenkins
Branch: master

commit e015a98b9e99dca7b97e97bb48af4392fd34dddb
Author: Chris Friesen <email address hidden>
Date: Tue Feb 23 17:27:00 2016 -0600

    check max_net_count against min_count when booting

    If the user has specified a min_count when booting instances, and
    our calculated max_net_count is smaller than the specified min_count
    then we want to fail with an easily-interpreted error.

    Change-Id: I7f8bde68e315dc39942faff4065db927e477e1f1
    Closes-Bug: #1549032

[Thierry Carrez (ttx)]

This issue was fixed in the openstack/nova 13.0.0.0rc1 release candidate.