Add a common generic dynamic loader for watcher

In watcher, an audit generates a set of actions which
aims at achieving a given goal (lower energy consumption, ...).
It is possible to configure different strategies in order to achieve
each goal. Each strategy is written as a Python class which produces
a set of actions. Today, the set of possible actions is fixed for a
given version of Watcher and enables optimization algorithms to
include actions such as instance migration, changing hypervisor state,
changing power state (ACPI level, ...).

This patchset add a common generic dynamic loader for plugins,
such as for custom Actions, Strategies, Planners, etc.

Partially implements: blueprint watcher-add-actions-via-conf

Change-Id: I59d031b93865fff2540e3973921e1bdafa95f88e

watcher/applier/primitives/loading/default.py

@@ -0,0 +1,29 @@
+# -*- encoding: utf-8 -*-
+# Copyright (c) 2015 b<>com
+#
+# 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 __future__ import unicode_literals
+
+from oslo_log import log
+
+from watcher.common.loader.default import DefaultLoader
+
+LOG = log.getLogger(__name__)
+
+
+class DefaultActionLoader(DefaultLoader):
+    def __init__(self):
+        super(DefaultActionLoader, self).__init__(namespace='watcher_actions')

watcher/common/exception.py

@@ -297,3 +297,7 @@ class VMNotFound(WatcherException):
 
 class HypervisorNotFound(WatcherException):
     message = _("The hypervisor could not be found")
+
+
+class LoadingError(WatcherException):
+    message = _("Error loading plugin '%(name)s'")

watcher/common/loader/base.py

@@ -0,0 +1,32 @@
+# -*- encoding: utf-8 -*-
+# Copyright (c) 2015 b<>com
+#
+# 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 __future__ import unicode_literals
+
+import abc
+import six
+
+
+@six.add_metaclass(abc.ABCMeta)
+class BaseLoader(object):
+
+    @abc.abstractmethod
+    def list_available(self):
+        raise NotImplementedError()
+
+    @abc.abstractmethod
+    def load(self, name):
+        raise NotImplementedError()

watcher/common/loader/default.py

@@ -0,0 +1,48 @@
+# -*- encoding: utf-8 -*-
+# Copyright (c) 2015 b<>com
+#
+# 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 __future__ import unicode_literals
+
+from oslo_log import log
+from stevedore.driver import DriverManager
+from stevedore import ExtensionManager
+
+from watcher.common import exception
+from watcher.common.loader.base import BaseLoader
+
+LOG = log.getLogger(__name__)
+
+
+class DefaultLoader(BaseLoader):
+    def __init__(self, namespace):
+        super(DefaultLoader, self).__init__()
+        self.namespace = namespace
+
+    def load(self, name):
+        try:
+            LOG.debug("Loading in namespace %s => %s ", self.namespace, name)
+            driver_manager = DriverManager(namespace=self.namespace,
+                                           name=name)
+            loaded = driver_manager.driver
+        except Exception as exc:
+            LOG.exception(exc)
+            raise exception.LoadingError(name=name)
+
+        return loaded()
+
+    def list_available(self):
+        extension_manager = ExtensionManager(namespace=self.namespace)
+        return {ext.name: ext.plugin for ext in extension_manager.extensions}

watcher/decision_engine/planner/loading/default.py

@@ -0,0 +1,30 @@
+# -*- encoding: utf-8 -*-
+# Copyright (c) 2015 b<>com
+#
+# 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 __future__ import unicode_literals
+
+from oslo_log import log
+
+from watcher.common.loader.default import DefaultLoader
+
+LOG = log.getLogger(__name__)
+
+
+class DefaultPlannerLoader(DefaultLoader):
+    def __init__(self):
+        super(DefaultPlannerLoader, self).__init__(
+            namespace='watcher_planners')

watcher/decision_engine/strategy/loading/base.py

@@ -1,49 +0,0 @@
-# -*- encoding: utf-8 -*-
-# Copyright (c) 2015 b<>com
-#
-# Authors: Jean-Emile DARTOIS <jean-emile.dartois@b-com.com>
-#
-# 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 abc
-from oslo_log import log
-import six
-
-from watcher.decision_engine.strategy.strategies.dummy_strategy import \
-    DummyStrategy
-
-LOG = log.getLogger(__name__)
-
-
-@six.add_metaclass(abc.ABCMeta)
-class BaseStrategyLoader(object):
-    default_strategy_cls = DummyStrategy
-
-    @abc.abstractmethod
-    def load_available_strategies(self):
-        raise NotImplementedError()
-
-    def load(self, strategy_to_load=None):
-        strategy_selected = None
-        try:
-            available_strategies = self.load_available_strategies()
-            LOG.debug("Available strategies: %s ", available_strategies)
-            strategy_cls = available_strategies.get(
-                strategy_to_load, self.default_strategy_cls
-            )
-            strategy_selected = strategy_cls()
-        except Exception as exc:
-            LOG.exception(exc)
-
-        return strategy_selected

watcher/decision_engine/strategy/loading/default.py

@@ -20,19 +20,13 @@
 from __future__ import unicode_literals
 
 from oslo_log import log
-from stevedore import ExtensionManager
-
-from watcher.decision_engine.strategy.loading.base import BaseStrategyLoader
 
+from watcher.common.loader.default import DefaultLoader
 
 LOG = log.getLogger(__name__)
 
 
-class DefaultStrategyLoader(BaseStrategyLoader):
+class DefaultStrategyLoader(DefaultLoader):
-
+    def __init__(self):
-    def load_available_strategies(self):
+        super(DefaultStrategyLoader, self).__init__(
-        extension_manager = ExtensionManager(
+            namespace='watcher_strategies')
-            namespace='watcher_strategies',
-            invoke_on_load=False,
-        )
-        return {ext.name: ext.plugin for ext in extension_manager.extensions}

watcher/locale/fr/LC_MESSAGES/watcher.po

@@ -8,7 +8,7 @@ msgid ""
 msgstr ""
 "Project-Id-Version: python-watcher 0.21.1.dev32\n"
 "Report-Msgid-Bugs-To: EMAIL@ADDRESS\n"
-"POT-Creation-Date: 2016-01-05 14:22+0100\n"
+"POT-Creation-Date: 2016-01-12 18:12+0100\n"
 "PO-Revision-Date: 2015-12-11 15:42+0100\n"
 "Last-Translator: FULL NAME <EMAIL@ADDRESS>\n"
 "Language: fr\n"
@@ -258,6 +258,11 @@ msgstr ""
 msgid "The hypervisor could not be found"
 msgstr ""
 
+#: watcher/common/exception.py:303
+#, fuzzy, python-format
+msgid "Error loading plugin '%(name)s'"
+msgstr "Erreur lors du chargement du module '%(name)s'"
+
 #: watcher/common/keystone.py:59
 msgid "No Keystone service catalog loaded"
 msgstr ""
@@ -291,7 +296,7 @@ msgstr ""
 msgid "'obj' argument type is not valid"
 msgstr ""
 
-#: watcher/decision_engine/strategy/selection/default.py:58
+#: watcher/decision_engine/strategy/selection/default.py:59
 #, python-format
 msgid "Incorrect mapping: could not find associated strategy for '%s'"
 msgstr ""

watcher/locale/watcher.pot

@@ -7,9 +7,9 @@
 #, fuzzy
 msgid ""
 msgstr ""
-"Project-Id-Version: python-watcher 0.21.1.dev79\n"
+"Project-Id-Version: python-watcher 0.22.1.dev9\n"
 "Report-Msgid-Bugs-To: EMAIL@ADDRESS\n"
-"POT-Creation-Date: 2016-01-05 14:22+0100\n"
+"POT-Creation-Date: 2016-01-12 18:12+0100\n"
 "PO-Revision-Date: YEAR-MO-DA HO:MI+ZONE\n"
 "Last-Translator: FULL NAME <EMAIL@ADDRESS>\n"
 "Language-Team: LANGUAGE <LL@li.org>\n"
@@ -256,6 +256,11 @@ msgstr ""
 msgid "The hypervisor could not be found"
 msgstr ""
 
+#: watcher/common/exception.py:303
+#, python-format
+msgid "Error loading plugin '%(name)s'"
+msgstr ""
+
 #: watcher/common/keystone.py:59
 msgid "No Keystone service catalog loaded"
 msgstr ""
@@ -289,7 +294,7 @@ msgstr ""
 msgid "'obj' argument type is not valid"
 msgstr ""
 
-#: watcher/decision_engine/strategy/selection/default.py:58
+#: watcher/decision_engine/strategy/selection/default.py:59
 #, python-format
 msgid "Incorrect mapping: could not find associated strategy for '%s'"
 msgstr ""

watcher/tests/common/loader/FakeLoadable.py

@@ -0,0 +1,28 @@
+# -*- encoding: utf-8 -*-
+# Copyright (c) 2015 b<>com
+#
+# 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 abc
+import six
+
+
+@six.add_metaclass(abc.ABCMeta)
+class FakeLoadable(object):
+    @classmethod
+    def namespace(cls):
+        return "TESTING"
+
+    @classmethod
+    def get_name(cls):
+        return 'fake'

watcher/tests/common/loader/test_loader.py

@@ -0,0 +1,53 @@
+# -*- encoding: utf-8 -*-
+# Copyright (c) 2015 b<>com
+#
+# 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 __future__ import unicode_literals
+
+import mock
+
+from oslotest.base import BaseTestCase
+from stevedore.driver import DriverManager
+from stevedore.extension import Extension
+
+from watcher.common import exception
+from watcher.common.loader.default import DefaultLoader
+from watcher.tests.common.loader.FakeLoadable import FakeLoadable
+
+
+class TestLoader(BaseTestCase):
+    @mock.patch("watcher.common.loader.default.DriverManager")
+    def test_load_driver_no_opt(self, m_driver_manager):
+        m_driver_manager.return_value = DriverManager.make_test_instance(
+            extension=Extension(name=FakeLoadable.get_name(),
+                                entry_point="%s:%s" % (
+                                FakeLoadable.__module__,
+                                FakeLoadable.__name__),
+                                plugin=FakeLoadable,
+                                obj=None),
+            namespace=FakeLoadable.namespace())
+
+        loader_manager = DefaultLoader(namespace='TESTING')
+        loaded_driver = loader_manager.load(name='fake')
+
+        self.assertEqual(loaded_driver.get_name(), FakeLoadable.get_name())
+
+    @mock.patch("watcher.common.loader.default.DriverManager")
+    def test_load_driver_bad_plugin(self, m_driver_manager):
+        m_driver_manager.side_effect = Exception()
+
+        loader_manager = DefaultLoader(namespace='TESTING')
+        self.assertRaises(exception.LoadingError, loader_manager.load,
+                          name='bad_driver')