495 lines
26 KiB
Python
495 lines
26 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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from nova.compute import utils as compute_utils
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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 objects
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from nova.objects import fields as fields_obj
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from nova import rpc
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from nova.scheduler.client import report
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from nova.scheduler import driver
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from nova.scheduler import utils
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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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self.placement_client = report.SchedulerReportClient()
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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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allocation_request_version=None, return_alternates=False):
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"""Returns a list of lists of Selection objects, which represent the
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hosts and (optionally) alternates for each instance.
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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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:param allocation_request_version: The microversion used to request the
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allocations.
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:param return_alternates: When True, zero or more alternate hosts are
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returned with each selected host. The number
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of alternates is determined by the
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configuration option
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`CONF.scheduler.max_attempts`.
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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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compute_utils.notify_about_scheduler_action(
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context=context, request_spec=spec_obj,
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action=fields_obj.NotificationAction.SELECT_DESTINATIONS,
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phase=fields_obj.NotificationPhase.START)
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host_selections = self._schedule(context, spec_obj, instance_uuids,
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alloc_reqs_by_rp_uuid, provider_summaries,
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allocation_request_version, return_alternates)
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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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compute_utils.notify_about_scheduler_action(
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context=context, request_spec=spec_obj,
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action=fields_obj.NotificationAction.SELECT_DESTINATIONS,
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phase=fields_obj.NotificationPhase.END)
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return host_selections
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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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allocation_request_version=None, return_alternates=False):
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"""Returns a list of lists of Selection objects.
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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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:param allocation_request_version: The microversion used to request the
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allocations.
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:param return_alternates: When True, zero or more alternate hosts are
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returned with each selected host. The number
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of alternates is determined by the
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configuration option
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`CONF.scheduler.max_attempts`.
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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 a generator-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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# 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 each requested instance, we want to return a host whose resources
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# for the instance have been claimed, along with zero or more
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# alternates. These alternates will be passed to the cell that the
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# selected host is in, so that if for some reason the build fails, the
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# cell conductor can retry building the instance on one of these
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# alternates instead of having to simply fail. The number of alternates
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# is based on CONF.scheduler.max_attempts; note that if there are not
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# enough filtered hosts to provide the full number of alternates, the
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# list of hosts may be shorter than this amount.
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num_alts = (CONF.scheduler.max_attempts - 1
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if return_alternates else 0)
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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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# We still support external scheduler drivers that don't use the
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# placement API (and set USES_ALLOCATION_CANDIDATE = False) and
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# therefore we skip all the claiming logic for those scheduler
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# drivers. Also, if there was a problem communicating with the
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# placement API, alloc_reqs_by_rp_uuid will be None, so we skip
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# claiming in that case as well. In the case where instance_uuids
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# is None, that indicates an older conductor, so we need to return
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# the objects without alternates. They will be converted back to
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# the older dict format representing HostState objects.
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return self._legacy_find_hosts(context, num_instances, spec_obj,
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hosts, num_alts,
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instance_uuids=instance_uuids)
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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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# The list of hosts that have been selected (and claimed).
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claimed_hosts = []
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for num, instance_uuid in enumerate(instance_uuids):
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# In a multi-create request, the first request spec from the list
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# is passed to the scheduler and that request spec's instance_uuid
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# might not be the same as the instance we're processing, so we
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# update the instance_uuid in that case before passing the request
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# spec to filters since at least one filter
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# (ServerGroupAntiAffinityFilter) depends on that information being
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# accurate.
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spec_obj.instance_uuid = instance_uuid
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# Reset the field so it's not persisted accidentally.
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spec_obj.obj_reset_changes(['instance_uuid'])
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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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# Any allocations will be cleaned up in the
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# _ensure_sufficient_hosts() call.
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break
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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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msg = ("A host state with uuid = '%s' that did not have a "
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"matching allocation_request was encountered while "
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"scheduling. This host was skipped.")
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LOG.debug(msg, cn_uuid)
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continue
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alloc_reqs = alloc_reqs_by_rp_uuid[cn_uuid]
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# TODO(jaypipes): Loop through all allocation_requests instead
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# of just trying the first one. For now, since we'll likely
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# want to order the allocation_requests in the future based on
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# information in the provider summaries, we'll just try to
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# claim resources using the first allocation_request
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alloc_req = alloc_reqs[0]
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if utils.claim_resources(elevated, self.placement_client,
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spec_obj, instance_uuid, alloc_req,
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allocation_request_version=allocation_request_version):
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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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break
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claimed_instance_uuids.append(instance_uuid)
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claimed_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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self._consume_selected_host(claimed_host, spec_obj,
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instance_uuid=instance_uuid)
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# Check if we were able to fulfill the request. If not, this call will
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# raise a NoValidHost exception.
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self._ensure_sufficient_hosts(context, claimed_hosts, num_instances,
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claimed_instance_uuids)
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# We have selected and claimed hosts for each instance. Now we need to
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# find alternates for each host.
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selections_to_return = self._get_alternate_hosts(
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claimed_hosts, spec_obj, hosts, num, num_alts,
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alloc_reqs_by_rp_uuid, allocation_request_version)
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return selections_to_return
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def _ensure_sufficient_hosts(self, context, hosts, required_count,
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claimed_uuids=None):
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"""Checks that we have selected a host for each requested instance. If
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not, log this failure, remove allocations for any claimed instances,
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and raise a NoValidHost exception.
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"""
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if len(hosts) == required_count:
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# We have enough hosts.
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return
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if claimed_uuids:
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self._cleanup_allocations(context, claimed_uuids)
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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 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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'%(required_count)d instances requested to build.',
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{'hosts': len(hosts),
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'required_count': required_count})
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reason = _('There are not enough hosts available.')
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raise exception.NoValidHost(reason=reason)
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def _cleanup_allocations(self, context, 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(context, uuid)
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def _legacy_find_hosts(self, context, num_instances, spec_obj, hosts,
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num_alts, instance_uuids=None):
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"""Some schedulers do not do claiming, or we can sometimes not be able
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to if the Placement service is not reachable. Additionally, we may be
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working with older conductors that don't pass in instance_uuids.
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"""
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# The list of hosts selected for each instance
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selected_hosts = []
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for num in range(num_instances):
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instance_uuid = instance_uuids[num] if instance_uuids else None
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if instance_uuid:
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# Update the RequestSpec.instance_uuid before sending it to
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# the filters in case we're doing a multi-create request, but
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# don't persist the change.
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spec_obj.instance_uuid = instance_uuid
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spec_obj.obj_reset_changes(['instance_uuid'])
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hosts = self._get_sorted_hosts(spec_obj, hosts, num)
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if not hosts:
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# No hosts left, so break here, and the
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# _ensure_sufficient_hosts() call below will handle this.
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break
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selected_host = hosts[0]
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selected_hosts.append(selected_host)
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self._consume_selected_host(selected_host, spec_obj,
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instance_uuid=instance_uuid)
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# Check if we were able to fulfill the request. If not, this call will
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# raise a NoValidHost exception.
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self._ensure_sufficient_hosts(context, selected_hosts, num_instances)
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# This the overall list of values to be returned. There will be one
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# item per instance, and each item will be a list of Selection objects
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# representing the selected host along with zero or more alternates
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# from the same cell.
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selections_to_return = self._get_alternate_hosts(selected_hosts,
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spec_obj, hosts, num, num_alts)
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return selections_to_return
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@staticmethod
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def _consume_selected_host(selected_host, spec_obj, instance_uuid=None):
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LOG.debug("Selected host: %(host)s", {'host': selected_host},
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instance_uuid=instance_uuid)
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selected_host.consume_from_request(spec_obj)
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# If we have a server group, add the selected host to it for the
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# (anti-)affinity filters to filter out hosts for subsequent instances
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# in a multi-create request.
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if spec_obj.instance_group is not None:
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spec_obj.instance_group.hosts.append(selected_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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# The ServerGroupAntiAffinityFilter also relies on
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# HostState.instances being accurate within a multi-create request.
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if instance_uuid and instance_uuid not in selected_host.instances:
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# Set a stub since ServerGroupAntiAffinityFilter only cares
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# about the keys.
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selected_host.instances[instance_uuid] = (
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objects.Instance(uuid=instance_uuid))
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def _get_alternate_hosts(self, selected_hosts, spec_obj, hosts, index,
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num_alts, alloc_reqs_by_rp_uuid=None,
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allocation_request_version=None):
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# We only need to filter/weigh the hosts again if we're dealing with
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# more than one instance and are going to be picking alternates.
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if index > 0 and num_alts > 0:
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# The selected_hosts have all had resources 'claimed' via
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# _consume_selected_host, so we need to filter/weigh and sort the
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# hosts again to get an accurate count for alternates.
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hosts = self._get_sorted_hosts(spec_obj, hosts, index)
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# This is the overall list of values to be returned. There will be one
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# item per instance, and each item will be a list of Selection objects
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# representing the selected host along with alternates from the same
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# cell.
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selections_to_return = []
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for selected_host in selected_hosts:
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# This is the list of hosts for one particular instance.
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if alloc_reqs_by_rp_uuid:
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selected_alloc_req = alloc_reqs_by_rp_uuid.get(
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selected_host.uuid)[0]
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else:
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selected_alloc_req = None
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selection = objects.Selection.from_host_state(selected_host,
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allocation_request=selected_alloc_req,
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allocation_request_version=allocation_request_version)
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selected_plus_alts = [selection]
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cell_uuid = selected_host.cell_uuid
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# This will populate the alternates with many of the same unclaimed
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# hosts. This is OK, as it should be rare for a build to fail. And
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# if there are not enough hosts to fully populate the alternates,
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# it's fine to return fewer than we'd like. Note that we exclude
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# any claimed host from consideration as an alternate because it
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# will have had its resources reduced and will have a much lower
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# chance of being able to fit another instance on it.
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for host in hosts:
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if len(selected_plus_alts) >= num_alts + 1:
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break
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if host.cell_uuid == cell_uuid and host not in selected_hosts:
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if alloc_reqs_by_rp_uuid is not None:
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alt_uuid = host.uuid
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if alt_uuid not in alloc_reqs_by_rp_uuid:
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msg = ("A host state with uuid = '%s' that did "
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"not have a matching allocation_request "
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"was encountered while scheduling. This "
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"host was skipped.")
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LOG.debug(msg, alt_uuid)
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continue
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# TODO(jaypipes): Loop through all allocation_requests
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# instead of just trying the first one. For now, since
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# we'll likely want to order the allocation_requests in
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# the future based on information in the provider
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# summaries, we'll just try to claim resources using
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# the first allocation_request
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alloc_req = alloc_reqs_by_rp_uuid[alt_uuid][0]
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alt_selection = (
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objects.Selection.from_host_state(host, alloc_req,
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allocation_request_version))
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else:
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alt_selection = objects.Selection.from_host_state(host)
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selected_plus_alts.append(alt_selection)
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selections_to_return.append(selected_plus_alts)
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return selections_to_return
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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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if CONF.filter_scheduler.shuffle_best_same_weighed_hosts:
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# NOTE(pas-ha) Randomize best hosts, relying on weighed_hosts
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# being already sorted by weight in descending order.
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# This decreases possible contention and rescheduling attempts
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# when there is a large number of hosts having the same best
|
|
# weight, especially so when host_subset_size is 1 (default)
|
|
best_hosts = [w for w in weighed_hosts
|
|
if w.weight == weighed_hosts[0].weight]
|
|
random.shuffle(best_hosts)
|
|
weighed_hosts = best_hosts + weighed_hosts[len(best_hosts):]
|
|
# Log the weighed hosts before stripping off the wrapper class so that
|
|
# the weight value gets logged.
|
|
LOG.debug("Weighed %(hosts)s", {'hosts': weighed_hosts})
|
|
# Strip off the WeighedHost wrapper class...
|
|
weighed_hosts = [h.obj for h in weighed_hosts]
|
|
|
|
# We randomize the first element in the returned list to alleviate
|
|
# congestion where the same host is consistently selected among
|
|
# numerous potential hosts for similar request specs.
|
|
host_subset_size = CONF.filter_scheduler.host_subset_size
|
|
if host_subset_size < len(weighed_hosts):
|
|
weighed_subset = weighed_hosts[0:host_subset_size]
|
|
else:
|
|
weighed_subset = weighed_hosts
|
|
chosen_host = random.choice(weighed_subset)
|
|
weighed_hosts.remove(chosen_host)
|
|
return [chosen_host] + weighed_hosts
|
|
|
|
def _get_all_host_states(self, context, spec_obj, provider_summaries):
|
|
"""Template method, so a subclass can implement caching."""
|
|
# NOTE(jaypipes): provider_summaries being None is treated differently
|
|
# from an empty dict. provider_summaries is None when we want to grab
|
|
# all compute nodes, for instance when using a scheduler driver that
|
|
# sets USES_ALLOCATION_CANDIDATES=False.
|
|
# The provider_summaries variable will be an empty dict when the
|
|
# Placement API found no providers that match the requested
|
|
# constraints, which in turn makes compute_uuids an empty list and
|
|
# get_host_states_by_uuids will return an empty generator-iterator
|
|
# also, which will eventually result in a NoValidHost error.
|
|
compute_uuids = None
|
|
if provider_summaries is not None:
|
|
compute_uuids = list(provider_summaries.keys())
|
|
return self.host_manager.get_host_states_by_uuids(context,
|
|
compute_uuids,
|
|
spec_obj)
|