101 lines
4.1 KiB
Python
101 lines
4.1 KiB
Python
# -*- coding: utf-8 -*-
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# Copyright 2014, Adrien Vergé <adrien.verge@numergy.com>
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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from oslo_log import log as logging
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from oslo_utils import uuidutils
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from cinder.compute import nova
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from cinder import exception
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from cinder.i18n import _
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from cinder.scheduler import filters
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from cinder.volume import volume_utils
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LOG = logging.getLogger(__name__)
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HINT_KEYWORD = 'local_to_instance'
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INSTANCE_HOST_PROP = 'OS-EXT-SRV-ATTR:host'
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REQUESTS_TIMEOUT = 5
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class InstanceLocalityFilter(filters.BaseBackendFilter):
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"""Schedule volume on the same host as a given instance.
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This filter enables selection of a storage back-end located on the host
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where the instance's hypervisor is running. This provides data locality:
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the instance and the volume are located on the same physical machine.
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In order to work:
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- The Extended Server Attributes extension needs to be active in Nova (this
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is by default), so that the 'OS-EXT-SRV-ATTR:host' property is returned
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when requesting instance info.
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- Either an account with privileged rights for Nova must be configured in
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Cinder configuration (configure a keystone authentication plugin in the
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[nova] section), or the user making the call needs to have sufficient
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rights (see 'extended_server_attributes' in Nova policy).
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"""
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def __init__(self):
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# Cache Nova API answers directly into the Filter object.
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# Since a BaseBackendFilter instance lives only during the volume's
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# scheduling, the cache is re-created for every new volume creation.
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self._cache = {}
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super(InstanceLocalityFilter, self).__init__()
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def backend_passes(self, backend_state, filter_properties):
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context = filter_properties['context']
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backend = volume_utils.extract_host(backend_state.backend_id, 'host')
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scheduler_hints = filter_properties.get('scheduler_hints') or {}
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instance_uuid = scheduler_hints.get(HINT_KEYWORD, None)
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# Without 'local_to_instance' hint
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if not instance_uuid:
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return True
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if not uuidutils.is_uuid_like(instance_uuid):
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raise exception.InvalidUUID(uuid=instance_uuid)
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# TODO(adrienverge): Currently it is not recommended to allow instance
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# migrations for hypervisors where this hint will be used. In case of
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# instance migration, a previously locally-created volume will not be
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# automatically migrated. Also in case of instance migration during the
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# volume's scheduling, the result is unpredictable. A future
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# enhancement would be to subscribe to Nova migration events (e.g. via
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# Ceilometer).
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# First, lookup for already-known information in local cache
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if instance_uuid in self._cache:
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return self._cache[instance_uuid] == backend
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server = nova.API().get_server(context, instance_uuid,
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privileged_user=True,
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timeout=REQUESTS_TIMEOUT)
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if not hasattr(server, INSTANCE_HOST_PROP):
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LOG.warning('Hint "%s" dropped because Nova did not return '
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'enough information. Either Nova policy needs to '
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'be changed or a privileged account for Nova '
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'should be specified in conf.', HINT_KEYWORD)
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raise exception.CinderException(_('Hint "%s" not supported.') %
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HINT_KEYWORD)
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self._cache[instance_uuid] = getattr(server, INSTANCE_HOST_PROP)
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# Match if given instance is hosted on backend
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return self._cache[instance_uuid] == backend
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