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OpenStack Study: filters.py**** CubicPower OpenStack Study ****
# Copyright (c) 2011-2012 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. """ Filter support """ from nova import loadables from nova.openstack.common.gettextutils import _ from nova.openstack.common import log as logging LOG = logging.getLogger(__name__)
**** CubicPower OpenStack Study **** class BaseFilter(object): """Base class for all filter classes."""
**** CubicPower OpenStack Study **** def _filter_one(self, obj, filter_properties): """Return True if it passes the filter, False otherwise. Override this in a subclass. """ return True
**** CubicPower OpenStack Study **** def filter_all(self, filter_obj_list, filter_properties): """Yield objects that pass the filter. Can be overridden in a subclass, if you need to base filtering decisions on all objects. Otherwise, one can just override _filter_one() to filter a single object. """ for obj in filter_obj_list: if self._filter_one(obj, filter_properties): yield obj # Set to true in a subclass if a filter only needs to be run once # for each request rather than for each instance run_filter_once_per_request = False
**** CubicPower OpenStack Study **** def run_filter_for_index(self, index): """Return True if the filter needs to be run for the "index-th" instance in a request. Only need to override this if a filter needs anything other than "first only" or "all" behaviour. """ if self.run_filter_once_per_request and index > 0: return False else: return True
**** CubicPower OpenStack Study **** class BaseFilterHandler(loadables.BaseLoader): """Base class to handle loading filter classes. This class should be subclassed where one needs to use filters. """
**** CubicPower OpenStack Study **** def get_filtered_objects(self, filter_classes, objs, filter_properties, index=0): list_objs = list(objs) LOG.debug(_("Starting with %d host(s)"), len(list_objs)) for filter_cls in filter_classes: cls_name = filter_cls.__name__ filter = filter_cls() if filter.run_filter_for_index(index): objs = filter.filter_all(list_objs, filter_properties) if objs is None: LOG.debug(_("Filter %(cls_name)s says to stop filtering"), {'cls_name': cls_name}) return list_objs = list(objs) if not list_objs: LOG.info(_("Filter %s returned 0 hosts"), cls_name) break LOG.debug(_("Filter %(cls_name)s returned " "%(obj_len)d host(s)"), {'cls_name': cls_name, 'obj_len': len(list_objs)}) return list_objs
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