OpenStack Block Storage (Cinder)
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# Copyright (c) 2011-2013 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.
"""
A common base for handling extension classes.
Used by BaseFilterHandler and BaseWeightHandler
"""
import inspect
from stevedore import extension
class BaseHandler(object):
"""Base class to handle loading filter and weight classes."""
def __init__(self, modifier_class_type, modifier_namespace):
self.namespace = modifier_namespace
self.modifier_class_type = modifier_class_type
self.extension_manager = extension.ExtensionManager(modifier_namespace)
def _is_correct_class(self, cls):
"""Return whether an object is a class of the correct type.
(or is not prefixed with an underscore)
"""
return (inspect.isclass(cls) and
not cls.__name__.startswith('_') and
issubclass(cls, self.modifier_class_type))
def get_all_classes(self):
# We use a set, as some classes may have an entrypoint of their own,
# and also be returned by a function such as 'all_filters' for example
return [ext.plugin for ext in self.extension_manager if
self._is_correct_class(ext.plugin)]