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# vim: tabstop=4 shiftwidth=4 softtabstop=4
# Copyright (c) 2010 Openstack, LLC.
# Copyright 2010 United States Government as represented by the
# Administrator of the National Aeronautics and Space Administration.
# All Rights Reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License"); you may
# not use this file except in compliance with the License. You may obtain
# a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
# License for the specific language governing permissions and limitations
# under the License.
"""
Chance (Random) Scheduler implementation
"""
import random
from nova import exception
from nova.scheduler import driver
class ChanceScheduler(driver.Scheduler):
"""Implements Scheduler as a random node selector."""
def _filter_hosts(self, request_spec, hosts, **kwargs):
"""Filter a list of hosts based on request_spec."""
filter_properties = kwargs.get('filter_properties', {})
ignore_hosts = filter_properties.get('ignore_hosts', [])
hosts = [host for host in hosts if host not in ignore_hosts]
return hosts
def _schedule(self, context, topic, request_spec, **kwargs):
"""Picks a host that is up at random."""
elevated = context.elevated()
hosts = self.hosts_up(elevated, topic)
if not hosts:
msg = _("Is the appropriate service running?")
raise exception.NoValidHost(reason=msg)
hosts = self._filter_hosts(request_spec, hosts, **kwargs)
if not hosts:
msg = _("Could not find another compute")
raise exception.NoValidHost(reason=msg)
return hosts[int(random.random() * len(hosts))]
def schedule(self, context, topic, method, *_args, **kwargs):
"""Picks a host that is up at random."""
host = self._schedule(context, topic, None, **kwargs)
driver.cast_to_host(context, topic, host, method, **kwargs)
def schedule_run_instance(self, context, request_spec, *_args, **kwargs):
"""Create and run an instance or instances"""
num_instances = request_spec.get('num_instances', 1)
instances = []
for num in xrange(num_instances):
host = self._schedule(context, 'compute', request_spec, **kwargs)
request_spec['instance_properties']['launch_index'] = num
instance = self.create_instance_db_entry(context, request_spec)
driver.cast_to_compute_host(context, host,
'run_instance', instance_uuid=instance['uuid'], **kwargs)
instances.append(driver.encode_instance(instance))
# So if we loop around, create_instance_db_entry will actually
# create a new entry, instead of assume it's been created
# already
del request_spec['instance_properties']['uuid']
return instances
def schedule_prep_resize(self, context, request_spec, *args, **kwargs):
"""Select a target for resize."""
host = self._schedule(context, 'compute', request_spec, **kwargs)
driver.cast_to_compute_host(context, host, 'prep_resize', **kwargs)
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