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