aggregate_image_os_type_isolation.py

from oslo_config import cfg
from oslo_log import log as logging

from nova import db
from nova.scheduler import filters

isolated_opts = [
    cfg.ListOpt('isolated_image_os_type',
                default=[],
                help='Image os_type to run on isolated host'),
]
CONF = cfg.CONF
CONF.register_opts(isolated_opts)

LOG = logging.getLogger(__name__)


class AggregateImageOsTypeIsolationFilter(filters.BaseHostFilter):
    """Filter compute nodes that satisfy instance image os_type property.

    The AggregateImageOsTypeIsolationFilter filters compute nodes that satisfy
    the os_type property specified on the instance's image properties.
    Image properties are contained in the image dictionary in the request_spec.
    """

    # Aggregate data and Image Properties do not change within a request
    run_filter_once_per_request = True

    def host_passes(self, host_state, filter_properties):
        """Check if host passes specified os_type image property.

        Returns True for compute nodes that satisfy image properties
        contained in the request_spec.
        """

        spec = filter_properties.get('request_spec', {})
        image_props = spec.get('image', {}).get('properties', {})
        image_os_type = image_props.get('os_type')

        context = filter_properties['context'].elevated()
        metadata = db.aggregate_metadata_get_by_host(context, host_state.host)
        host_os_type = metadata.get('os_type')

        # If host has os_type part of its aggregate metadatas, it is reserved
        # for images with the matching os_type property.
        if host_os_type:
            return image_os_type in host_os_type
        else:
            # Host without os_type can only run images not in the list of
            # isolated os_type.
            return image_os_type not in CONF.isolated_image_os_type