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Instances and networking to those instances will continue to work as expected during the maintenance time. Functions that try to provision new instances or volumes will not work, however.
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Maintenance was completed at 12:00pm CST
The controller node was upgraded to CentOS 7.2 and the openstack-nova-compute service was restarted on all compute nodes. We also installed some monitoring for common errors we've seen so we can be more proactive then reactive with problems.