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OpenStack Study: scheduler_options.py**** CubicPower OpenStack Study ****
# Copyright (c) 2011 OpenStack Foundation # 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. """ SchedulerOptions monitors a local .json file for changes and loads it if needed. This file is converted to a data structure and passed into the filtering and weighing functions which can use it for dynamic configuration. """ import datetime import json import os from oslo.config import cfg from nova.openstack.common import excutils from nova.openstack.common.gettextutils import _ from nova.openstack.common import log as logging from nova.openstack.common import timeutils scheduler_json_config_location_opt = cfg.StrOpt( 'scheduler_json_config_location', default='', help='Absolute path to scheduler configuration JSON file.') CONF = cfg.CONF CONF.register_opt(scheduler_json_config_location_opt) LOG = logging.getLogger(__name__)
**** CubicPower OpenStack Study **** class SchedulerOptions(object): """SchedulerOptions monitors a local .json file for changes and loads it if needed. This file is converted to a data structure and passed into the filtering and weighing functions which can use it for dynamic configuration. """
**** CubicPower OpenStack Study **** def __init__(self): super(SchedulerOptions, self).__init__() self.data = {} self.last_modified = None self.last_checked = None
**** CubicPower OpenStack Study **** def _get_file_handle(self, filename): """Get file handle. Broken out for testing.""" return open(filename)
**** CubicPower OpenStack Study **** def _get_file_timestamp(self, filename): """Get the last modified datetime. Broken out for testing.""" try: return os.path.getmtime(filename) except os.error as e: with excutils.save_and_reraise_exception(): LOG.exception(_("Could not stat scheduler options file " "%(filename)s: '%(e)s'"), {'filename': filename, 'e': e})
**** CubicPower OpenStack Study **** def _load_file(self, handle): """Decode the JSON file. Broken out for testing.""" try: return json.load(handle) except ValueError as e: LOG.exception(_("Could not decode scheduler options: '%s'"), e) return {}
**** CubicPower OpenStack Study **** def _get_time_now(self): """Get current UTC. Broken out for testing.""" return timeutils.utcnow()
**** CubicPower OpenStack Study **** def get_configuration(self, filename=None): """Check the json file for changes and load it if needed.""" if not filename: filename = CONF.scheduler_json_config_location if not filename: return self.data if self.last_checked: now = self._get_time_now() if now - self.last_checked < datetime.timedelta(minutes=5): return self.data last_modified = self._get_file_timestamp(filename) if (not last_modified or not self.last_modified or last_modified > self.last_modified): self.data = self._load_file(self._get_file_handle(filename)) self.last_modified = last_modified if not self.data: self.data = {} return self.data
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