Rehome ServicePluginBase

A number of subprojects inherit neutron's ServicePluginBase
class [1]. This patch rehomes ServicePluginBase into
neutron-lib along with 2 other classes required for the
implementation of ServicePluginBase.

UTs and a release note are also included.

[1] http://codesearch.openstack.org/?q=ServicePluginBase

Change-Id: I2b1131ac53e9bfeb42a92f9ef134be6ff4cfe5a3

neutron_lib/services/base.py

@@ -0,0 +1,92 @@
+#    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 _PluginInterface(object):
+
+    @classmethod
+    def __subclasshook__(cls, klass):
+        """Checking plugin class.
+
+        The __subclasshook__ method is a class method
+        that will be called every time a class is tested
+        using issubclass(klass, _PluginInterface).
+        In that case, it will check that every method
+        marked with the abstractmethod decorator is
+        provided by the plugin class.
+        """
+
+        if not cls.__abstractmethods__:
+            return NotImplemented
+
+        for method in cls.__abstractmethods__:
+            if any(method in base.__dict__ for base in klass.__mro__):
+                continue
+            return NotImplemented
+        return True
+
+
+class _WorkerSupportServiceMixin(object):
+
+    @property
+    def _workers(self):
+        try:
+            return self.__workers
+        except AttributeError:
+            self.__workers = []
+        return self.__workers
+
+    def get_workers(self):
+        """Returns a collection NeutronWorker instances needed by this service.
+
+        """
+        return list(self._workers)
+
+    def add_worker(self, worker):
+        """Adds NeutronWorker needed for this service
+
+        If a object needs to define workers thread/processes outside of API/RPC
+        workers then it will call this method to register worker. Should be
+        called on initialization stage before running services
+        """
+        self._workers.append(worker)
+
+    def add_workers(self, workers):
+        """Adds NeutronWorker list needed for this service
+
+        The same as add_worker but adds a list of workers
+        """
+        self._workers.extend(workers)
+
+
+@six.add_metaclass(abc.ABCMeta)
+class ServicePluginBase(_PluginInterface,
+                        _WorkerSupportServiceMixin):
+    """Define base interface for any Advanced Service plugin."""
+    supported_extension_aliases = []
+
+    @abc.abstractmethod
+    def get_plugin_type(self):
+        """Return one of predefined service types.
+
+        """
+        pass
+
+    @abc.abstractmethod
+    def get_plugin_description(self):
+        """Return string description of the plugin."""
+        pass

neutron_lib/tests/unit/services/test_base.py

@@ -0,0 +1,85 @@
+#    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 neutron_lib.services import base
+from neutron_lib.tests import _base as test_base
+
+
+class _Worker(base._WorkerSupportServiceMixin):
+    pass
+
+
+class Test_WorkerSupportServiceMixin(test_base.BaseTestCase):
+
+    def setUp(self):
+        super(Test_WorkerSupportServiceMixin, self).setUp()
+        self.worker = _Worker()
+
+    def test_allocate_workers(self):
+        self.assertEqual([], self.worker.get_workers())
+
+    def test_add_worker(self):
+        workers = [object(), object()]
+        for w in workers:
+            self.worker.add_worker(w)
+
+        self.assertSequenceEqual(workers, self.worker.get_workers())
+
+    def test_add_workers(self):
+        workers = [object(), object(), object()]
+        self.worker.add_workers(workers)
+
+        self.assertSequenceEqual(workers, self.worker.get_workers())
+
+
+class Test_PluginInterface(test_base.BaseTestCase):
+
+    def test_issubclass_hook(self):
+        class A(object):
+            def f(self):
+                pass
+
+        class B(base._PluginInterface):
+            @abc.abstractmethod
+            def f(self):
+                pass
+
+        self.assertTrue(issubclass(A, B))
+
+    def test_issubclass_hook_class_without_abstract_methods(self):
+        class A(object):
+            def f(self):
+                pass
+
+        class B(base._PluginInterface):
+            def f(self):
+                pass
+
+        self.assertFalse(issubclass(A, B))
+
+    def test_issubclass_hook_not_all_methods_implemented(self):
+        class A(object):
+            def f(self):
+                pass
+
+        class B(base._PluginInterface):
+            @abc.abstractmethod
+            def f(self):
+                pass
+
+            @abc.abstractmethod
+            def g(self):
+                pass
+
+        self.assertFalse(issubclass(A, B))

releasenotes/notes/service-plugin-base-a42c2241a2fe0d26.yaml

@@ -0,0 +1,4 @@
+---
+features:
+  - The class ``neutron.services.service_base.ServicePluginBase`` is
+    now available as ``neutron_lib.services.base.ServicePluginBase``.