Comment 8 for bug 1781286

I had to re-learn why this part of comment 2 isn't a problem:

"""
The only thing I can figure is maybe you have the max_attempts config option value set to 1 or you're forcing the host/node during the server create?

https://github.com/openstack/nova/blob/39b05ee9e34ae7e7c1854439f887588ec157bc69/nova/scheduler/utils.py#L634

In that case we don't set the retry entry in filter_properties.
"""

That's because if CONF.scheduler.max_attempts=1 or force_hosts/nodes, we don't set the 'retry' entry in the filter_properties dict passed between conductor and compute:

https://github.com/openstack/nova/blob/536e5fa57f72f71217fd9f2160df0284a76102e1/nova/scheduler/utils.py#L638

And then if we hit a build failure in compute, we don't cast back to the cell conductor to reschedule, we just fail:

https://github.com/openstack/nova/blob/536e5fa57f72f71217fd9f2160df0284a76102e1/nova/compute/manager.py#L1825

So if we get here in conductor during a reschedule:

https://github.com/openstack/nova/blob/536e5fa57f72f71217fd9f2160df0284a76102e1/nova/conductor/manager.py#L585

The 'retry' key is going to be set and num_attempts won't be 1.