- A new nova-manage command has been added to discover any new hosts that are
added to a cell. If a deployment has migrated to cellsv2 using either the
simple_cell_setup or the map_cell0/map_cell_and_hosts/map_instances combo
then anytime a new host is added to a cell this new
"nova-manage cell_v2 discover_hosts" needs to be run before instances can
be booted on that host. If multiple hosts are added at one time the command
only needs to be run one time to discover all of them. This command should
be run from an API host, or a host that is configured to use the nova_api
Please note that adding a host to a cell and not running this command could
lead to build failures/reschedules if that host is selected by the
scheduler. The discover_hosts command is necessary to route requests to the
host but is not necessary in order for the scheduler to be aware of the
host. It is advised that nova-compute hosts are configured with
"enable_new_services=False" in order to avoid failures before the hosts
have been discovered.
- If a deployer has updated their deployment to using cellsv2 using either
the simple_cell_setup or the map_cell0/map_cell_and_hosts/map_instances
combo and they add a new host into the cell it may cause build failures
or reschedules until they run the "nova-manage cell_v2 discover_hosts"
command. This is because the scheduler will quickly become aware of the
host but nova-api will not know how to route the request to that host until
it has been "discovered". In order to avoid that it is advised that
new computes are disabled until the discover command has been run.