nova/releasenotes/notes/scheduler-can-discover-hosts-4b799cbd14dbc7dc.yaml
Dan Smith 9eb7bcea05 Allow scheduler to run cell host discovery periodically
Since cellsv2 has required host mappings to be present, we have lost
our automatic host registration behavior. This is a conscious choice,
given that we do not want to have upcalls from the cells to the API
database. This adds a periodic task to have the scheduler do the
discovery routine, which for small deployments may be an acceptable
amount of background overhead in exchange for the automatic behavior.

There is also probably some amount of performance improvement that
can be added to the host discovery routine to make it less of an
issue. However, just generalizing the existing routine and letting
it run periodically gives us some coverage, given where we are in
the current cycle.

Related to blueprint cells-scheduler-integration

Change-Id: Iab5f172cdef35645bae56b9b384e032f3160e826
2017-02-01 12:22:23 -08:00

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YAML

---
features:
- As new hosts are added to Nova, the `nova-manage cell_v2
discover_hosts` command must be run in order to map them into
their cell. For deployments with proper automation, this is a
trivial extra step in that process. However, for smaller or
non-automated deployments, there is a new configuration variable
for the scheduler process which will perform this discovery
periodically. By setting
`scheduler.discover_hosts_in_cells_interval` to a positive value,
the scheduler will handle this for you. Note that this process
involves listing all hosts in all cells, and is likely to be too
heavyweight for large deployments to run all the time.