---
features:
  - |
    Compute drivers now expose capabilities via traits in the
    Placement API.  Capabilities must map to standard traits defined
    in `the os-traits project
    <https://docs.openstack.org/os-traits/latest/>`_; for now these
    are:

    * ``COMPUTE_NET_ATTACH_INTERFACE``
    * ``COMPUTE_DEVICE_TAGGING``
    * ``COMPUTE_NET_ATTACH_INTERFACE_WITH_TAG``
    * ``COMPUTE_VOLUME_ATTACH_WITH_TAG``
    * ``COMPUTE_VOLUME_EXTEND``
    * ``COMPUTE_VOLUME_MULTI_ATTACH``
    * ``COMPUTE_TRUSTED_CERTS``

    Any traits provided by the driver will be automatically added
    during startup or a periodic update of a compute node.  Similarly
    any traits later retracted by the driver will be automatically
    removed.

    However any traits which are removed by the admin from the compute
    node resource provider via the Placement API will not be
    reinstated until the compute service's provider cache is reset.
    This can be triggered via a ``SIGHUP``.
