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