Comment 4 for bug 1716706

This is a script that can be used to recreate this. Pass in the number of instances you want, I used 30 and had one instance go over the quota limit and fail the recheck in conductor.

#!/bin/bash

set -x

NUM=$1
IMAGE=$2

for i in `seq 1 $NUM`; do
   nova boot --flavor 1 --image $IMAGE test-over-quota-$i &
done

As a result of this, I found that the instance didn't actually go into ERROR state because of another bug:

Sep 13 17:58:26 devstack-queens nova-conductor[3129]: WARNING nova.scheduler.utils [None req-90a115b2-5838-4be2-afe2-a3b755015e19 demo demo] [instance: 888925b0-164a-4d4a-bb6c-c0426f904e95] Setting instance to ERROR state.: TooManyInstances: Quota exceeded for instances: Requested 1, but already used 10 of 10 instances
Sep 13 17:58:26 devstack-queens nova-conductor[3129]: ERROR root [None req-90a115b2-5838-4be2-afe2-a3b755015e19 demo demo] Original exception being dropped: ['Traceback (most recent call last):\n', ' File "/opt/stack/nova/nova/conductor/manager.py", line 1003, in schedule_and_build_instances\n orig_num_req=len(build_requests))\n', ' File "/opt/stack/nova/nova/compute/utils.py", line 764, in check_num_instances_quota\n allowed=total_alloweds)\n', 'TooManyInstances: Quota exceeded for instances: Requested 1, but already used 10 of 10 instances\n']: InstanceNotFound: Instance 888925b0-164a-4d4a-bb6c-c0426f904e95 could not be found.
Sep 13 17:58:26 devstack-queens nova-conductor[3129]: ERROR oslo_messaging.rpc.server [None req-90a115b2-5838-4be2-afe2-a3b755015e19 demo demo] Exception during message handling: InstanceNotFound: Instance 888925b0-164a-4d4a-bb6c-c0426f904e95 could not be found.
Sep 13 17:58:26 devstack-queens nova-conductor[3129]: ERROR oslo_messaging.rpc.server InstanceNotFound: Instance 888925b0-164a-4d4a-bb6c-c0426f904e95 could not be found.

Because we don't target the cell when updating the instance.

https://github.com/openstack/nova/blob/cfdec41eeec5fab220702efefdaafc45559aeb14/nova/conductor/manager.py#L1168