96 lines
3.4 KiB
Python
96 lines
3.4 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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import imp
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import os
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import pkg_resources
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from nova.openstack.common import cfg
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from nova.openstack.common import log as logging
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from nova.openstack.common.notifier import list_notifier
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CONF = cfg.CONF
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LOG = logging.getLogger(__name__)
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class PluginManager(object):
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"""Manages plugin entrypoints and loading.
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For a service to implement this plugin interface for callback purposes:
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- Make use of the openstack-common notifier system
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- Instantiate this manager in each process (passing in
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project and service name)
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For an API service to extend itself using this plugin interface,
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it needs to query the plugin_extension_factory provided by
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the already-instantiated PluginManager.
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"""
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def __init__(self, project_name, service_name):
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""" Construct Plugin Manager; load and initialize plugins.
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project_name (e.g. 'nova' or 'glance') is used
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to construct the entry point that identifies plugins.
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The service_name (e.g. 'compute') is passed on to
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each plugin as a raw string for it to do what it will.
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"""
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self._project_name = project_name
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self._service_name = service_name
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self.plugins = []
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def _force_use_list_notifier(self):
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if (CONF.notification_driver !=
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'nova.openstack.common.notifier.list_notifier'):
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if not hasattr(CONF, "list_notifier_drivers"):
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CONF.list_notifier_drivers = []
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old_notifier = CONF.notification_driver
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drvstring = 'nova.openstack.common.notifier.list_notifier'
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CONF.notification_driver = drvstring
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if old_notifier:
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list_notifier.add_driver(old_notifier)
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def load_plugins(self):
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self.plugins = []
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for entrypoint in pkg_resources.iter_entry_points('%s.plugin' %
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self._project_name):
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try:
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pluginclass = entrypoint.load()
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plugin = pluginclass(self._service_name)
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self.plugins.append(plugin)
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except Exception, exc:
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LOG.error(_("Failed to load plugin %(plug)s: %(exc)s") %
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{'plug': entrypoint, 'exc': exc})
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# See if we need to turn on the list notifier
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for plugin in self.plugins:
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if plugin.notifiers:
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self._force_use_list_notifier()
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break
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# Register individual notifiers.
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for plugin in self.plugins:
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for notifier in plugin.notifiers:
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list_notifier.add_driver(notifier)
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def plugin_extension_factory(self, ext_mgr):
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for plugin in self.plugins:
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descriptors = plugin.api_extension_descriptors
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for descriptor in descriptors:
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ext_mgr.load_extension(descriptor)
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