59 lines
2.1 KiB
Python
59 lines
2.1 KiB
Python
# vim: tabstop=4 shiftwidth=4 softtabstop=4
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# Copyright (c) 2010 Openstack, LLC.
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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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Scheduler base class that all Schedulers should inherit from
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"""
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import datetime
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from nova import db
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from nova import exception
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from nova import flags
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FLAGS = flags.FLAGS
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flags.DEFINE_integer('service_down_time', 60,
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'maximum time since last checkin for up service')
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class NoValidHost(exception.Error):
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"""There is no valid host for the command."""
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pass
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class Scheduler(object):
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"""The base class that all Scheduler clases should inherit from."""
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@staticmethod
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def service_is_up(service):
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"""Check whether a service is up based on last heartbeat."""
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last_heartbeat = service['updated_at'] or service['created_at']
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elapsed = datetime.datetime.now() - last_heartbeat
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return elapsed < datetime.timedelta(seconds=FLAGS.service_down_time)
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def hosts_up(self, context, topic):
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"""Return the list of hosts that have a running service for topic."""
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services = db.service_get_all_by_topic(context, topic)
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return [service.host
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for service in services
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if self.service_is_up(service)]
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def schedule(self, context, topic, *_args, **_kwargs):
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"""Must override at least this method for scheduler to work."""
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raise NotImplementedError("Must implement a fallback schedule")
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