Add the plugin framework from common; use and test.

For blueprint novaplugins.

Change-Id: Id4a5ae3ebb91f941956e2f73ecfd9ea1d290a235
This commit is contained in:
Andrew Bogott 2012-07-01 16:37:14 -05:00
parent 9a283c6b37
commit ece205982f
7 changed files with 390 additions and 1 deletions

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@ -56,6 +56,7 @@ This module provides Manager, a base class for managers.
from nova.db import base
from nova import flags
from nova.openstack.common import log as logging
from nova.openstack.common.plugin import pluginmanager
from nova.openstack.common.rpc import dispatcher as rpc_dispatcher
from nova.scheduler import rpcapi as scheduler_rpcapi
from nova import version
@ -138,8 +139,13 @@ class Manager(base.Base):
if not host:
host = FLAGS.host
self.host = host
self.load_plugins()
super(Manager, self).__init__(db_driver)
def load_plugins(self):
pluginmgr = pluginmanager.PluginManager('nova', self.__class__)
pluginmgr.load_plugins()
def create_rpc_dispatcher(self):
'''Get the rpc dispatcher for this manager.
@ -205,6 +211,10 @@ class SchedulerDependentManager(Manager):
self.scheduler_rpcapi = scheduler_rpcapi.SchedulerAPI()
super(SchedulerDependentManager, self).__init__(host, db_driver)
def load_plugins(self):
pluginmgr = pluginmanager.PluginManager('nova', self.service_name)
pluginmgr.load_plugins()
def update_service_capabilities(self, capabilities):
"""Remember these capabilities to send on next periodic update."""
self.last_capabilities = capabilities

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@ -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.

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@ -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 nova.openstack.common import log as logging
from nova.openstack.common.plugin import plugin
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)

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@ -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 nova.openstack.common import log as logging
from nova.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 = []

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@ -0,0 +1,95 @@
# 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 nova.openstack.common import cfg
from nova.openstack.common import log as logging
from nova.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 = []
def _force_use_list_notifier(self):
if (CONF.notification_driver !=
'nova.openstack.common.notifier.list_notifier'):
if not hasattr(CONF, "list_notifier_drivers"):
CONF.list_notifier_drivers = []
old_notifier = CONF.notification_driver
drvstring = 'nova.openstack.common.notifier.list_notifier'
CONF.notification_driver = drvstring
if old_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})
# See if we need to turn on the list notifier
for plugin in self.plugins:
if plugin.notifiers:
self._force_use_list_notifier()
break
# Register individual notifiers.
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)

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@ -0,0 +1,90 @@
# Copyright 2011 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 pkg_resources
import nova
from nova.api.openstack.compute import extensions as computeextensions
from nova.api.openstack import extensions
from nova.openstack.common.plugin import plugin
from nova.openstack.common.plugin import pluginmanager
from nova import test
class StubController(object):
def i_am_the_stub(self):
pass
class StubControllerExtension(extensions.ExtensionDescriptor):
"""This is a docstring. We need it."""
name = 'stubextension'
alias = 'stubby'
def get_resources(self):
resources = []
res = extensions.ResourceExtension('testme',
StubController())
resources.append(res)
return resources
service_list = []
class TestPluginClass(plugin.Plugin):
def __init__(self, service_name):
super(TestPluginClass, self).__init__(service_name)
self._add_api_extension_descriptor(StubControllerExtension)
service_list.append(service_name)
class MockEntrypoint(pkg_resources.EntryPoint):
def load(self):
return TestPluginClass
class APITestCase(test.TestCase):
"""Test case for the plugin api extension interface"""
def test_add_extension(self):
def mock_load(_s):
return TestPluginClass()
def mock_iter_entry_points(_t):
return [MockEntrypoint("fake", "fake", ["fake"])]
self.stubs.Set(pkg_resources, 'iter_entry_points',
mock_iter_entry_points)
global service_list
service_list = []
# Marking out the default extension paths makes this test MUCH faster.
self.flags(osapi_compute_extension=[])
self.flags(osapi_volume_extension=[])
found = False
mgr = computeextensions.ExtensionManager()
for res in mgr.get_resources():
# We have to use this weird 'dir' check because
# the plugin framework muddies up the classname
# such that 'isinstance' doesn't work right.
if 'i_am_the_stub' in dir(res.controller):
found = True
self.assertTrue(found)
self.assertEqual(len(service_list), 1)
self.assertEqual(service_list[0], 'compute-extensions')

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@ -1,7 +1,7 @@
[DEFAULT]
# The list of modules to copy from openstack-common
modules=cfg,context,excutils,gettextutils,importutils,iniparser,jsonutils,local,log,notifier,policy,setup,timeutils,rpc
modules=cfg,context,excutils,gettextutils,importutils,iniparser,jsonutils,local,log,notifier,plugin,policy,setup,timeutils,rpc
# The base module to hold the copy of openstack.common
base=nova