125 lines
5.2 KiB
Python
125 lines
5.2 KiB
Python
# Copyright (c) 2010 OpenStack Foundation
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# Copyright 2010 United States Government as represented by the
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# Administrator of the National Aeronautics and Space Administration.
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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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Chance (Random) Scheduler implementation
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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 nova.compute import rpcapi as compute_rpcapi
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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.scheduler import driver
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CONF = nova.conf.CONF
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LOG = logging.getLogger(__name__)
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class ChanceScheduler(driver.Scheduler):
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"""Implements Scheduler as a random node selector."""
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USES_ALLOCATION_CANDIDATES = False
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def __init__(self, *args, **kwargs):
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super(ChanceScheduler, self).__init__(*args, **kwargs)
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LOG.warning('ChanceScheduler is deprecated in Pike and will be '
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'removed in a subsequent release.')
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def _filter_hosts(self, hosts, spec_obj):
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"""Filter a list of hosts based on RequestSpec."""
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ignore_hosts = spec_obj.ignore_hosts or []
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hosts = [host for host in hosts if host not in ignore_hosts]
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return hosts
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def _schedule(self, context, topic, spec_obj, instance_uuids,
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return_alternates=False):
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"""Picks a host that is up at random."""
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elevated = context.elevated()
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hosts = self.hosts_up(elevated, topic)
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if not hosts:
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msg = _("Is the appropriate service running?")
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raise exception.NoValidHost(reason=msg)
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hosts = self._filter_hosts(hosts, spec_obj)
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if not hosts:
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msg = _("Could not find another compute")
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raise exception.NoValidHost(reason=msg)
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# Note that we don't claim in the chance scheduler
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num_instances = len(instance_uuids)
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# If possible, we'd like to return distinct hosts for each instance.
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# But when there are fewer available hosts than requested instances, we
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# will need to return some duplicates.
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if len(hosts) >= num_instances:
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selected_hosts = random.sample(hosts, num_instances)
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else:
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selected_hosts = [random.choice(hosts)
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for i in range(num_instances)]
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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 that item will be a list of Selection objects
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# representing the selected host and zero or more alternates.
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# NOTE(edleafe): in a multi-cell environment, this can return
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# alternates from different cells. When support for multiple cells is
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# implemented in select_destinations, this will have to be updated to
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# restrict alternates to come from the same cell.
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selections_to_return = []
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# We can't return dupes as alternates, since alternates are used when
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# building to the selected host fails.
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if return_alternates:
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alts_per_instance = min(len(hosts), CONF.scheduler.max_attempts)
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else:
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alts_per_instance = 0
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for sel_host in selected_hosts:
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selection = objects.Selection.from_host_state(sel_host)
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sel_plus_alts = [selection]
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while len(sel_plus_alts) < alts_per_instance:
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candidate = random.choice(hosts)
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if (candidate not in sel_plus_alts) and (
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candidate not in selected_hosts):
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# We don't want to include a selected host as an alternate,
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# as it will have a high likelihood of not having enough
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# resources left after it has an instance built on it.
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alt_select = objects.Selection.from_host_state(candidate)
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sel_plus_alts.append(alt_select)
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selections_to_return.append(sel_plus_alts)
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return selections_to_return
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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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"""Selects random destinations. Returns a list of list of Selection
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objects.
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"""
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num_instances = spec_obj.num_instances
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# TODO(danms): This needs to be extended to support multiple cells
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# and limiting the destination scope to a single requested cell
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host_selections = self._schedule(context, compute_rpcapi.RPC_TOPIC,
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spec_obj, instance_uuids)
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if len(host_selections) < 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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return host_selections
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