OpenStack Study: isolated_hosts_filter.py

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# Copyright (c) 2011-2012 OpenStack Foundation

# All Rights Reserved.

#

# Licensed under the Apache License, Version 2.0 (the "License"); you may

# not use this file except in compliance with the License. You may obtain

# a copy of the License at

#

# http://www.apache.org/licenses/LICENSE-2.0

#

# Unless required by applicable law or agreed to in writing, software

# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT

# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the

# License for the specific language governing permissions and limitations

# under the License.

from oslo.config import cfg

from nova.scheduler import filters

isolated_opts = [

cfg.ListOpt('isolated_images',

default=[],

help='Images to run on isolated host'),

cfg.ListOpt('isolated_hosts',

default=[],

help='Host reserved for specific images'),

cfg.BoolOpt('restrict_isolated_hosts_to_isolated_images',

default=True,

help='Whether to force isolated hosts to run only isolated '

'images'),

]

CONF = cfg.CONF

CONF.register_opts(isolated_opts)

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class IsolatedHostsFilter(filters.BaseHostFilter):

"""Keep specified images to selected hosts."""

# The configuration values do not change within a request

run_filter_once_per_request = True

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    def host_passes(self, host_state, filter_properties):

        """Result Matrix with 'restrict_isolated_hosts_to_isolated_images' set

        to True:

                     | isolated_image | non_isolated_image

        -------------+----------------+-------------------

        iso_host     |    True        |     False

        non_iso_host |    False       |      True

        Result Matrix with 'restrict_isolated_hosts_to_isolated_images' set

        to False:

                     | isolated_image | non_isolated_image

        -------------+----------------+-------------------

        iso_host     |    True        |      True

        non_iso_host |    False       |      True

        """

        # If the configuration does not list any hosts, the filter will always

        # return True, assuming a configuration error, so letting all hosts

        # through.

        isolated_hosts = CONF.isolated_hosts

        isolated_images = CONF.isolated_images

        restrict_isolated_hosts_to_isolated_images = (CONF.

                                   restrict_isolated_hosts_to_isolated_images)

        if not isolated_images:

            # As there are no images to match, return True if the filter is

            # not restrictive otherwise return False if the host is in the

            # isolation list.

            return ((not restrict_isolated_hosts_to_isolated_images) or

                   (host_state.host not in isolated_hosts))

        spec = filter_properties.get('request_spec', {})

        props = spec.get('instance_properties', {})

        image_ref = props.get('image_ref')

        image_isolated = image_ref in isolated_images

        host_isolated = host_state.host in isolated_hosts

        if restrict_isolated_hosts_to_isolated_images:

            return (image_isolated == host_isolated)

        else:

            return (not image_isolated) or host_isolated