338 lines
17 KiB
Python
338 lines
17 KiB
Python
# Copyright (c) 2011 OpenStack Foundation
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# All Rights Reserved.
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#
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# Licensed under the Apache License, Version 2.0 (the "License"); you may
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# not use this file except in compliance with the License. You may obtain
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# 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, WITHOUT
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# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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# License for the specific language governing permissions and limitations
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# under the License.
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"""
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The FilterScheduler is for creating instances locally.
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You can customize this scheduler by specifying your own Host Filters and
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Weighing Functions.
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"""
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import random
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from oslo_log import log as logging
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from six.moves import range
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import nova.conf
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from nova import exception
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from nova.i18n import _
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from nova import rpc
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from nova.scheduler import client
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from nova.scheduler import driver
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CONF = nova.conf.CONF
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LOG = logging.getLogger(__name__)
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class FilterScheduler(driver.Scheduler):
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"""Scheduler that can be used for filtering and weighing."""
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def __init__(self, *args, **kwargs):
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super(FilterScheduler, self).__init__(*args, **kwargs)
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self.notifier = rpc.get_notifier('scheduler')
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scheduler_client = client.SchedulerClient()
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self.placement_client = scheduler_client.reportclient
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def select_destinations(self, context, spec_obj, instance_uuids,
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alloc_reqs_by_rp_uuid, provider_summaries):
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"""Returns a sorted list of HostState objects that satisfy the
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supplied request_spec.
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These hosts will have already had their resources claimed in Placement.
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:param context: The RequestContext object
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:param spec_obj: The RequestSpec object
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:param instance_uuids: List of UUIDs, one for each value of the spec
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object's num_instances attribute
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:param alloc_reqs_by_rp_uuid: Optional dict, keyed by resource provider
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UUID, of the allocation requests that may
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be used to claim resources against
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matched hosts. If None, indicates either
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the placement API wasn't reachable or
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that there were no allocation requests
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returned by the placement API. If the
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latter, the provider_summaries will be an
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empty dict, not None.
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:param provider_summaries: Optional dict, keyed by resource provider
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UUID, of information that will be used by
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the filters/weighers in selecting matching
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hosts for a request. If None, indicates that
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the scheduler driver should grab all compute
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node information locally and that the
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Placement API is not used. If an empty dict,
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indicates the Placement API returned no
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potential matches for the requested
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resources.
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"""
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self.notifier.info(
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context, 'scheduler.select_destinations.start',
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dict(request_spec=spec_obj.to_legacy_request_spec_dict()))
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num_instances = spec_obj.num_instances
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selected_hosts = self._schedule(context, spec_obj, instance_uuids,
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alloc_reqs_by_rp_uuid, provider_summaries)
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# Couldn't fulfill the request_spec
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if len(selected_hosts) < num_instances:
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# NOTE(Rui Chen): If multiple creates failed, set the updated time
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# of selected HostState to None so that these HostStates are
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# refreshed according to database in next schedule, and release
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# the resource consumed by instance in the process of selecting
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# host.
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for host in selected_hosts:
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host.updated = None
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# Log the details but don't put those into the reason since
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# we don't want to give away too much information about our
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# actual environment.
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LOG.debug('There are %(hosts)d hosts available but '
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'%(num_instances)d instances requested to build.',
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{'hosts': len(selected_hosts),
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'num_instances': num_instances})
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reason = _('There are not enough hosts available.')
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raise exception.NoValidHost(reason=reason)
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self.notifier.info(
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context, 'scheduler.select_destinations.end',
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dict(request_spec=spec_obj.to_legacy_request_spec_dict()))
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return selected_hosts
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def _schedule(self, context, spec_obj, instance_uuids,
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alloc_reqs_by_rp_uuid, provider_summaries):
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"""Returns a list of hosts that meet the required specs, ordered by
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their fitness.
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These hosts will have already had their resources claimed in Placement.
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:param context: The RequestContext object
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:param spec_obj: The RequestSpec object
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:param instance_uuids: List of instance UUIDs to place or move.
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:param alloc_reqs_by_rp_uuid: Optional dict, keyed by resource provider
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UUID, of the allocation requests that may
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be used to claim resources against
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matched hosts. If None, indicates either
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the placement API wasn't reachable or
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that there were no allocation requests
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returned by the placement API. If the
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latter, the provider_summaries will be an
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empty dict, not None.
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:param provider_summaries: Optional dict, keyed by resource provider
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UUID, of information that will be used by
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the filters/weighers in selecting matching
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hosts for a request. If None, indicates that
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the scheduler driver should grab all compute
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node information locally and that the
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Placement API is not used. If an empty dict,
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indicates the Placement API returned no
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potential matches for the requested
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resources.
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"""
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elevated = context.elevated()
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# Find our local list of acceptable hosts by repeatedly
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# filtering and weighing our options. Each time we choose a
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# host, we virtually consume resources on it so subsequent
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# selections can adjust accordingly.
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# Note: remember, we are using an iterator here. So only
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# traverse this list once. This can bite you if the hosts
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# are being scanned in a filter or weighing function.
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hosts = self._get_all_host_states(elevated, spec_obj,
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provider_summaries)
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# A list of the instance UUIDs that were successfully claimed against
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# in the placement API. If we are not able to successfully claim for
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# all involved instances, we use this list to remove those allocations
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# before returning
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claimed_instance_uuids = []
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selected_hosts = []
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# NOTE(sbauza): The RequestSpec.num_instances field contains the number
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# of instances created when the RequestSpec was used to first boot some
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# instances. This is incorrect when doing a move or resize operation,
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# so prefer the length of instance_uuids unless it is None.
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num_instances = (len(instance_uuids) if instance_uuids
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else spec_obj.num_instances)
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for num in range(num_instances):
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hosts = self._get_sorted_hosts(spec_obj, hosts, num)
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if not hosts:
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# NOTE(jaypipes): If we get here, that means not all instances
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# in instance_uuids were able to be matched to a selected host.
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# So, let's clean up any already-claimed allocations here
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# before breaking and returning
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self._cleanup_allocations(claimed_instance_uuids)
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break
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if (instance_uuids is None or
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not self.USES_ALLOCATION_CANDIDATES or
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alloc_reqs_by_rp_uuid is None):
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# Unfortunately, we still need to deal with older conductors
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# that may not be passing in a list of instance_uuids. In those
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# cases, obviously we can't claim resources because we don't
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# have instance UUIDs to claim with, so we just grab the first
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# host in the list of sorted hosts. In addition to older
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# conductors, we need to support the caching scheduler, which
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# doesn't use the placement API (and has
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# USES_ALLOCATION_CANDIDATE = False) and therefore we skip all
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# the claiming logic for that scheduler driver. Finally, if
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# there was a problem communicating with the placement API,
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# alloc_reqs_by_rp_uuid will be None, so we skip claiming in
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# that case as well
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claimed_host = hosts[0]
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else:
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instance_uuid = instance_uuids[num]
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# Attempt to claim the resources against one or more resource
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# providers, looping over the sorted list of possible hosts
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# looking for an allocation request that contains that host's
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# resource provider UUID
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claimed_host = None
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for host in hosts:
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cn_uuid = host.uuid
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if cn_uuid not in alloc_reqs_by_rp_uuid:
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LOG.debug("Found host state %s that wasn't in "
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"allocation requests. Skipping.", cn_uuid)
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continue
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alloc_reqs = alloc_reqs_by_rp_uuid[cn_uuid]
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if self._claim_resources(elevated, spec_obj, instance_uuid,
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alloc_reqs):
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claimed_host = host
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break
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if claimed_host is None:
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# We weren't able to claim resources in the placement API
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# for any of the sorted hosts identified. So, clean up any
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# successfully-claimed resources for prior instances in
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# this request and return an empty list which will cause
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# select_destinations() to raise NoValidHost
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LOG.debug("Unable to successfully claim against any host.")
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self._cleanup_allocations(claimed_instance_uuids)
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return []
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claimed_instance_uuids.append(instance_uuid)
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LOG.debug("Selected host: %(host)s", {'host': claimed_host})
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selected_hosts.append(claimed_host)
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# Now consume the resources so the filter/weights will change for
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# the next instance.
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claimed_host.consume_from_request(spec_obj)
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if spec_obj.instance_group is not None:
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spec_obj.instance_group.hosts.append(claimed_host.host)
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# hosts has to be not part of the updates when saving
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spec_obj.instance_group.obj_reset_changes(['hosts'])
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return selected_hosts
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def _cleanup_allocations(self, instance_uuids):
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"""Removes allocations for the supplied instance UUIDs."""
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if not instance_uuids:
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return
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LOG.debug("Cleaning up allocations for %s", instance_uuids)
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for uuid in instance_uuids:
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self.placement_client.delete_allocation_for_instance(uuid)
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def _claim_resources(self, ctx, spec_obj, instance_uuid, alloc_reqs):
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"""Given an instance UUID (representing the consumer of resources), the
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HostState object for the host that was chosen for the instance, and a
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list of allocation request JSON objects, attempt to claim resources for
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the instance in the placement API. Returns True if the claim process
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was successful, False otherwise.
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:param ctx: The RequestContext object
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:param spec_obj: The RequestSpec object
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:param instance_uuid: The UUID of the consuming instance
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:param cn_uuid: UUID of the host to allocate against
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:param alloc_reqs: A list of allocation request JSON objects that
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allocate against (at least) the compute host
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selected by the _schedule() method. These allocation
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requests were constructed from a call to the GET
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/allocation_candidates placement API call. Each
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allocation_request satisfies the original request
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for resources and can be supplied as-is (along with
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the project and user ID to the placement API's
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PUT /allocations/{consumer_uuid} call to claim
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resources for the instance
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"""
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LOG.debug("Attempting to claim resources in the placement API for "
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"instance %s", instance_uuid)
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project_id = spec_obj.project_id
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# NOTE(jaypipes): So, the RequestSpec doesn't store the user_id,
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# only the project_id, so we need to grab the user information from
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# the context. Perhaps we should consider putting the user ID in
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# the spec object?
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user_id = ctx.user_id
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# TODO(jaypipes): Loop through all allocation requests instead of just
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# trying the first one. For now, since we'll likely want to order the
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# allocation requests in the future based on information in the
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# provider summaries, we'll just try to claim resources using the first
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# allocation request
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alloc_req = alloc_reqs[0]
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return self.placement_client.claim_resources(instance_uuid,
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alloc_req, project_id, user_id)
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def _get_sorted_hosts(self, spec_obj, host_states, index):
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"""Returns a list of HostState objects that match the required
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scheduling constraints for the request spec object and have been sorted
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according to the weighers.
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"""
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filtered_hosts = self.host_manager.get_filtered_hosts(host_states,
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spec_obj, index)
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LOG.debug("Filtered %(hosts)s", {'hosts': filtered_hosts})
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if not filtered_hosts:
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return []
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weighed_hosts = self.host_manager.get_weighed_hosts(filtered_hosts,
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spec_obj)
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# Strip off the WeighedHost wrapper class...
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weighed_hosts = [h.obj for h in weighed_hosts]
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LOG.debug("Weighed %(hosts)s", {'hosts': weighed_hosts})
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# We randomize the first element in the returned list to alleviate
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# congestion where the same host is consistently selected among
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# numerous potential hosts for similar request specs.
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host_subset_size = CONF.filter_scheduler.host_subset_size
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if host_subset_size < len(weighed_hosts):
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weighed_subset = weighed_hosts[0:host_subset_size]
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else:
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weighed_subset = weighed_hosts
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chosen_host = random.choice(weighed_subset)
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weighed_hosts.remove(chosen_host)
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return [chosen_host] + weighed_hosts
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def _get_all_host_states(self, context, spec_obj, provider_summaries):
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"""Template method, so a subclass can implement caching."""
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# NOTE(jaypipes): provider_summaries being None is treated differently
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# from an empty dict. provider_summaries is None when we want to grab
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# all compute nodes, for instance when using the caching scheduler.
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# The provider_summaries variable will be an empty dict when the
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# Placement API found no providers that match the requested
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# constraints, which in turn makes compute_uuids an empty list and
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# get_host_states_by_uuids will return an empty tuple also, which will
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# eventually result in a NoValidHost error.
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compute_uuids = None
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if provider_summaries is not None:
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compute_uuids = list(provider_summaries.keys())
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return self.host_manager.get_host_states_by_uuids(context,
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compute_uuids,
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spec_obj)
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