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# Copyright 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.
from openstack.common import log as logging
LOG = logging.getLogger(__name__)
class Plugin(object):
"""Defines an interface for adding functionality to an OpenStack service.
A plugin interacts with a service via the following pathways:
- An optional set of notifiers, managed by calling add_notifier()
or by overriding _notifiers()
- A set of api extensions, managed via add_api_extension_descriptor()
- Direct calls to service functions.
- Whatever else the plugin wants to do on its own.
This is the reference implementation.
"""
# The following functions are provided as convenience methods
# for subclasses. Subclasses should call them but probably not
# override them.
def _add_api_extension_descriptor(self, descriptor):
"""Subclass convenience method which adds an extension descriptor.
Subclass constructors should call this method when
extending a project's REST interface.
Note that once the api service has loaded, the
API extension set is more-or-less fixed, so
this should mainly be called by subclass constructors.
"""
self._api_extension_descriptors.append(descriptor)
def _add_notifier(self, notifier):
"""Subclass convenience method which adds a notifier.
Notifier objects should implement the function notify(message).
Each notifier receives a notify() call whenever an openstack
service broadcasts a notification.
Best to call this during construction. Notifiers are enumerated
and registered by the pluginmanager at plugin load time.
"""
self._notifiers.append(notifier)
# The following methods are called by OpenStack services to query
# plugin features. Subclasses should probably not override these.
def _notifiers(self):
"""Returns list of notifiers for this plugin."""
return self._notifiers
notifiers = property(_notifiers)
def _api_extension_descriptors(self):
"""Return a list of API extension descriptors.
Called by a project API during its load sequence.
"""
return self._api_extension_descriptors
api_extension_descriptors = property(_api_extension_descriptors)
# Most plugins will override this:
def __init__(self, service_name):
self._notifiers = []
self._api_extension_descriptors = []
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