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# 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 oslo_log import log as logging
from nova import loadables
LOG = logging.getLogger(__name__)
class BaseFilter(object):
"""Base class for all filter classes."""
def _filter_one(self, obj, spec_obj):
"""Return True if it passes the filter, False otherwise.
Override this in a subclass.
"""
return True
def filter_all(self, filter_obj_list, spec_obj):
"""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, spec_obj):
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
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
class BaseFilterHandler(loadables.BaseLoader):
"""Base class to handle loading filter classes.
This class should be subclassed where one needs to use filters.
"""
def get_filtered_objects(self, filters, objs, spec_obj, index=0):
list_objs = list(objs)
LOG.debug("Starting with %d host(s)", len(list_objs))
# Track the hosts as they are removed. The 'full_filter_results' list
# contains the host/nodename info for every host that passes each
# filter, while the 'part_filter_results' list just tracks the number
# removed by each filter, unless the filter returns zero hosts, in
# which case it records the host/nodename for the last batch that was
# removed. Since the full_filter_results can be very large, it is only
# recorded if the LOG level is set to debug.
part_filter_results = []
full_filter_results = []
log_msg = "%(cls_name)s: (start: %(start)s, end: %(end)s)"
for filter_ in filters:
if filter_.run_filter_for_index(index):
cls_name = filter_.__class__.__name__
start_count = len(list_objs)
objs = filter_.filter_all(list_objs, spec_obj)
if objs is None:
LOG.debug("Filter %s says to stop filtering", cls_name)
return
list_objs = list(objs)
end_count = len(list_objs)
part_filter_results.append(log_msg % {"cls_name": cls_name,
"start": start_count, "end": end_count})
if list_objs:
remaining = [(getattr(obj, "host", obj),
getattr(obj, "nodename", ""))
for obj in list_objs]
full_filter_results.append((cls_name, remaining))
else:
LOG.info("Filter %s returned 0 hosts", cls_name)
full_filter_results.append((cls_name, None))
break
LOG.debug("Filter %(cls_name)s returned %(obj_len)d host(s)",
{'cls_name': cls_name, 'obj_len': len(list_objs)})
if not list_objs:
# Log the filtration history
msg_dict = {
"inst_uuid": spec_obj.instance_uuid,
"str_results": str(full_filter_results),
}
full_msg = ("Filtering removed all hosts for the request with "
"instance ID "
"'%(inst_uuid)s'. Filter results: %(str_results)s"
) % msg_dict
LOG.debug(full_msg)
msg_dict["str_results"] = str(part_filter_results)
part_msg = ("Filtering removed all hosts for the request with "
"instance ID "
"'%(inst_uuid)s'. Filter results: %(str_results)s"
) % msg_dict
LOG.info(part_msg)
return list_objs
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