116 lines
4.6 KiB
Python
116 lines
4.6 KiB
Python
# Copyright 2013 OpenStack Foundation
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# Copyright 2013 IBM Corp.
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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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import functools
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from keystone import exception
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from keystone.i18n import _
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def truncated(f):
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"""Ensure list truncation is detected in Driver list entity methods.
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This is designed to wrap Driver list_{entity} methods in order to
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calculate if the resultant list has been truncated. Provided a limit dict
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is found in the hints list, we increment the limit by one so as to ask the
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wrapped function for one more entity than the limit, and then once the list
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has been generated, we check to see if the original limit has been
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exceeded, in which case we truncate back to that limit and set the
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'truncated' boolean to 'true' in the hints limit dict.
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"""
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@functools.wraps(f)
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def wrapper(self, hints, *args, **kwargs):
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if not hasattr(hints, 'limit'):
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raise exception.UnexpectedError(
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_('Cannot truncate a driver call without hints list as '
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'first parameter after self '))
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if hints.limit is None or hints.filters:
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return f(self, hints, *args, **kwargs)
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# A limit is set, so ask for one more entry than we need
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list_limit = hints.limit['limit']
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hints.set_limit(list_limit + 1)
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ref_list = f(self, hints, *args, **kwargs)
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# If we got more than the original limit then trim back the list and
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# mark it truncated. In both cases, make sure we set the limit back
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# to its original value.
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if len(ref_list) > list_limit:
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hints.set_limit(list_limit, truncated=True)
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return ref_list[:list_limit]
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else:
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hints.set_limit(list_limit)
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return ref_list
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return wrapper
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class Hints(object):
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"""Encapsulate driver hints for listing entities.
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Hints are modifiers that affect the return of entities from a
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list_<entities> operation. They are typically passed to a driver to give
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direction as to what filtering, pagination or list limiting actions are
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being requested.
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It is optional for a driver to action some or all of the list hints,
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but any filters that it does satisfy must be marked as such by calling
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removing the filter from the list.
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A Hint object contains filters, which is a list of dicts that can be
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accessed publicly. Also it contains a dict called limit, which will
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indicate the amount of data we want to limit our listing to.
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If the filter is discovered to never match, then `cannot_match` can be set
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to indicate that there will not be any matches and the backend work can be
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short-circuited.
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Each filter term consists of:
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* ``name``: the name of the attribute being matched
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* ``value``: the value against which it is being matched
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* ``comparator``: the operation, which can be one of ``equals``,
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``contains``, ``startswith`` or ``endswith``
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* ``case_sensitive``: whether any comparison should take account of
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case
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* ``type``: will always be 'filter'
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"""
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def __init__(self):
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self.limit = None
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self.filters = list()
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self.cannot_match = False
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def add_filter(self, name, value, comparator='equals',
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case_sensitive=False):
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"""Add a filter to the filters list, which is publicly accessible."""
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self.filters.append({'name': name, 'value': value,
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'comparator': comparator,
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'case_sensitive': case_sensitive,
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'type': 'filter'})
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def get_exact_filter_by_name(self, name):
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"""Return a filter key and value if exact filter exists for name."""
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for entry in self.filters:
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if (entry['type'] == 'filter' and entry['name'] == name and
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entry['comparator'] == 'equals'):
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return entry
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def set_limit(self, limit, truncated=False):
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"""Set a limit to indicate the list should be truncated."""
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self.limit = {'limit': limit, 'type': 'limit', 'truncated': truncated}
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