Comment 5 for bug 1739323

Actually I'm not sure how you're hitting this, unless a concurrent thread is modifying the host_state_map dict at the same time.

When we're looping, we add the state_key (host,node) entry to host_state_map if it's not in there:

https://github.com/openstack/nova/blob/3ebc358002d3f62a9ff0a3b0f50fea4f2a5c2c91/nova/scheduler/host_manager.py#L698

and then we add that key to seen_nodes:

https://github.com/openstack/nova/blob/3ebc358002d3f62a9ff0a3b0f50fea4f2a5c2c91/nova/scheduler/host_manager.py#L708

so everything in seen_nodes should also be in host_state_map when we return the tuple of HostState objects:

https://github.com/openstack/nova/blob/3ebc358002d3f62a9ff0a3b0f50fea4f2a5c2c91/nova/scheduler/host_manager.py#L718