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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.
import pkg_resources
from oslo.config import cfg
from openstack.common.gettextutils import _
from openstack.common import log as logging
from openstack.common.notifier import api as notifier_api
CONF = cfg.CONF
LOG = logging.getLogger(__name__)
class PluginManager(object):
"""Manages plugin entrypoints and loading.
For a service to implement this plugin interface for callback purposes:
- Make use of the openstack-common notifier system
- Instantiate this manager in each process (passing in
project and service name)
For an API service to extend itself using this plugin interface,
it needs to query the plugin_extension_factory provided by
the already-instantiated PluginManager.
"""
def __init__(self, project_name, service_name):
"""Construct Plugin Manager; load and initialize plugins.
project_name (e.g. 'nova' or 'glance') is used
to construct the entry point that identifies plugins.
The service_name (e.g. 'compute') is passed on to
each plugin as a raw string for it to do what it will.
"""
self._project_name = project_name
self._service_name = service_name
self.plugins = []
def load_plugins(self):
self.plugins = []
for entrypoint in pkg_resources.iter_entry_points('%s.plugin' %
self._project_name):
try:
pluginclass = entrypoint.load()
plugin = pluginclass(self._service_name)
self.plugins.append(plugin)
except Exception as exc:
LOG.error(_("Failed to load plugin %(plug)s: %(exc)s") %
{'plug': entrypoint, 'exc': exc})
# Register individual notifiers.
for plugin in self.plugins:
for notifier in plugin.notifiers:
notifier_api.add_driver(notifier)
def plugin_extension_factory(self, ext_mgr):
for plugin in self.plugins:
descriptors = plugin.api_extension_descriptors
for descriptor in descriptors:
ext_mgr.load_extension(descriptor)
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