94 lines
3.3 KiB
Python
94 lines
3.3 KiB
Python
# Copyright 2012 OpenStack LLC.
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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 kwapi.openstack.common import log as logging
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from kwapi.openstack.common.plugin import plugin
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LOG = logging.getLogger(__name__)
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class _CallbackNotifier(object):
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"""Manages plugin-defined notification callbacks.
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For each Plugin, a CallbackNotifier will be added to the
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notification driver list. Calls to notify() with appropriate
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messages will be hooked and prompt callbacks.
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A callback should look like this:
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def callback(context, message, user_data)
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"""
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def __init__(self):
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self._callback_dict = {}
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def _add_callback(self, event_type, callback, user_data):
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callback_list = self._callback_dict.get(event_type, [])
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callback_list.append({'function': callback,
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'user_data': user_data})
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self._callback_dict[event_type] = callback_list
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def _remove_callback(self, callback):
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for callback_list in self._callback_dict.values():
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for entry in callback_list:
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if entry['function'] == callback:
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callback_list.remove(entry)
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def notify(self, context, message):
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if message.get('event_type') not in self._callback_dict:
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return
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for entry in self._callback_dict[message.get('event_type')]:
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entry['function'](context, message, entry.get('user_data'))
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def callbacks(self):
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return self._callback_dict
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class CallbackPlugin(plugin.Plugin):
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""" Plugin with a simple callback interface.
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This class is provided as a convenience for producing a simple
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plugin that only watches a couple of events. For example, here's
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a subclass which prints a line the first time an instance is created.
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class HookInstanceCreation(CallbackPlugin):
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def __init__(self, _service_name):
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super(HookInstanceCreation, self).__init__()
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self._add_callback(self.magic, 'compute.instance.create.start')
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def magic(self):
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print "An instance was created!"
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self._remove_callback(self, self.magic)
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"""
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def __init__(self, service_name):
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super(CallbackPlugin, self).__init__(service_name)
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self._callback_notifier = _CallbackNotifier()
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self._add_notifier(self._callback_notifier)
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def _add_callback(self, callback, event_type, user_data=None):
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"""Add callback for a given event notification.
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Subclasses can call this as an alternative to implementing
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a fullblown notify notifier.
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"""
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self._callback_notifier._add_callback(event_type, callback, user_data)
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def _remove_callback(self, callback):
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"""Remove all notification callbacks to specified function."""
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self._callback_notifier._remove_callback(callback)
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