80 lines
2.8 KiB
Python
80 lines
2.8 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 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.scheduler import driver
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CONF = nova.conf.CONF
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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 _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):
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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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return random.choice(hosts)
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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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"""Selects random destinations."""
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num_instances = spec_obj.num_instances
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# NOTE(timello): Returns a list of dicts with 'host', 'nodename' and
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# 'limits' as keys for compatibility with filter_scheduler.
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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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dests = []
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for i in range(num_instances):
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host = self._schedule(context, compute_rpcapi.RPC_TOPIC,
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spec_obj)
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host_state = self.host_manager.host_state_cls(host, None, None)
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dests.append(host_state)
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if len(dests) < 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 dests
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