---
features:
  - |
    It is now possible to configure multiple *nova-scheduler* workers via the
    ``[scheduler]workers`` configuration option. By default, the option runs
    ``ncpu`` workers if using the ``filter_scheduler`` scheduler driver,
    otherwise the default is 1.

    Since `blueprint placement-claims`_ in Pike, the FilterScheduler
    uses the Placement service to create resource allocations (claims)
    against a resource provider (i.e. compute node) chosen by the scheduler.
    That reduces the risk of scheduling collisions when running multiple
    schedulers.

    Since other scheduler drivers, like the CachingScheduler, do not
    use Placement, it is recommended to set workers=1 (default) for those
    other scheduler drivers.

    .. _blueprint placement-claims: https://specs.openstack.org/openstack/nova-specs/specs/pike/implemented/placement-claims.html
upgrade:
  - |
    The new ``[scheduler]workers`` configuration option defaults to ``ncpu``
    workers if using the ``filter_scheduler`` scheduler driver. If you are
    running *nova-scheduler* on the same host as other services, you may want
    to change this default value, or to otherwise account for running other
    instances of the *nova-scheduler* service.