diff options
Diffstat (limited to 'openstack/common/plugin')
| -rw-r--r-- | openstack/common/plugin/__init__.py | 14 | ||||
| -rw-r--r-- | openstack/common/plugin/callbackplugin.py | 93 | ||||
| -rw-r--r-- | openstack/common/plugin/plugin.py | 87 | ||||
| -rw-r--r-- | openstack/common/plugin/pluginmanager.py | 86 |
4 files changed, 280 insertions, 0 deletions
diff --git a/openstack/common/plugin/__init__.py b/openstack/common/plugin/__init__.py new file mode 100644 index 0000000..63c3905 --- /dev/null +++ b/openstack/common/plugin/__init__.py @@ -0,0 +1,14 @@ +# Copyright 2012 OpenStack LLC. +# 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. diff --git a/openstack/common/plugin/callbackplugin.py b/openstack/common/plugin/callbackplugin.py new file mode 100644 index 0000000..bb56a40 --- /dev/null +++ b/openstack/common/plugin/callbackplugin.py @@ -0,0 +1,93 @@ +# Copyright 2012 OpenStack LLC. +# 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.plugin import plugin +from openstack.common import log as logging + + +LOG = logging.getLogger(__name__) + + +class _CallbackNotifier(object): + """Manages plugin-defined notification callbacks. + + For each Plugin, a CallbackNotifier will be added to the + notification driver list. Calls to notify() with appropriate + messages will be hooked and prompt callbacks. + + A callback should look like this: + def callback(context, message, user_data) + """ + + def __init__(self): + self._callback_dict = {} + + def _add_callback(self, event_type, callback, user_data): + callback_list = self._callback_dict.get(event_type, []) + callback_list.append({'function': callback, + 'user_data': user_data}) + self._callback_dict[event_type] = callback_list + + def _remove_callback(self, callback): + for callback_list in self._callback_dict.values(): + for entry in callback_list: + if entry['function'] == callback: + callback_list.remove(entry) + + def notify(self, context, message): + if message.get('event_type') not in self._callback_dict: + return + + for entry in self._callback_dict[message.get('event_type')]: + entry['function'](context, message, entry.get('user_data')) + + def callbacks(self): + return self._callback_dict + + +class CallbackPlugin(plugin.Plugin): + """ Plugin with a simple callback interface. + + This class is provided as a convenience for producing a simple + plugin that only watches a couple of events. For example, here's + a subclass which prints a line the first time an instance is created. + + class HookInstanceCreation(CallbackPlugin): + + def __init__(self, _service_name): + super(HookInstanceCreation, self).__init__() + self._add_callback(self.magic, 'compute.instance.create.start') + + def magic(self): + print "An instance was created!" + self._remove_callback(self, self.magic) + """ + + def __init__(self, service_name): + super(CallbackPlugin, self).__init__(service_name) + self._callback_notifier = _CallbackNotifier() + self._add_notifier(self._callback_notifier) + + def _add_callback(self, callback, event_type, user_data=None): + """Add callback for a given event notification. + + Subclasses can call this as an alternative to implementing + a fullblown notify notifier. + """ + self._callback_notifier._add_callback(event_type, callback, user_data) + + def _remove_callback(self, callback): + """Remove all notification callbacks to specified function.""" + self._callback_notifier._remove_callback(callback) diff --git a/openstack/common/plugin/plugin.py b/openstack/common/plugin/plugin.py new file mode 100644 index 0000000..9f06342 --- /dev/null +++ b/openstack/common/plugin/plugin.py @@ -0,0 +1,87 @@ +# Copyright 2012 OpenStack LLC. +# 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 +from openstack.common.notifier import list_notifier + + +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 = [] diff --git a/openstack/common/plugin/pluginmanager.py b/openstack/common/plugin/pluginmanager.py new file mode 100644 index 0000000..0095135 --- /dev/null +++ b/openstack/common/plugin/pluginmanager.py @@ -0,0 +1,86 @@ +# Copyright 2012 OpenStack LLC. +# 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 imp +import os +import pkg_resources + +from openstack.common import cfg +from openstack.common import log as logging +from openstack.common.notifier import list_notifier + + +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 = [] + + # Make sure we're using the list_notifier. + if not hasattr(CONF, "list_notifier_drivers"): + CONF.list_notifier_drivers = [] + old_notifier = CONF.notification_driver + CONF.notification_driver = 'openstack.common.notifier.list_notifier' + if (old_notifier and + old_notifier != 'openstack.common.notifier.list_notifier'): + list_notifier.add_driver(old_notifier) + + 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, exc: + LOG.error(_("Failed to load plugin %(plug)s: %(exc)s") % + {'plug': entrypoint, 'exc': exc}) + + for plugin in self.plugins: + for notifier in plugin.notifiers: + list_notifier.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) |