Sync up plugin code from Moniker

Use the get_plugin of StorageEngine instead
Add get_plugin() to Plugin

Change-Id: Icc52b65d7ce98d19da54ffaac523d729feffdeb6

bufunfa/plugin.py

@@ -14,6 +14,7 @@
 # License for the specific language governing permissions and limitations
 # under the License.
 import abc
+from stevedore import driver
 
 from bufunfa.openstack.common import cfg
 from bufunfa.openstack.common import log as logging
@@ -42,6 +43,22 @@ class Plugin(object):
         """
         return True
 
+    @classmethod
+    def get_plugin(cls, name, ns=None, conf=None, invoke_on_load=False,
+                   invoke_args=(), invoke_kwds={}):
+        """
+        Load a plugin from namespace
+        """
+        ns = ns or cls.__plugin_ns__
+        if ns is None:
+            raise RuntimeError('No namespace provided or __plugin_ns__ unset')
+        LOG.debug('Looking for plugin %s in %s', name, ns)
+        mgr = driver.DriverManager(ns, name)
+        if conf:
+            mgr.driver.register_opts(conf)
+        return mgr.driver(*invoke_args, **invoke_kwds) if invoke_on_load \
+            else mgr.driver
+
     @classmethod
     def get_canonical_name(cls):
         """

bufunfa/storage/__init__.py

@@ -17,14 +17,12 @@
 # under the License.
 # NOTE(zykes): Copied from Ceilometer
 from urlparse import urlparse
-from stevedore import driver
 from bufunfa.openstack.common import cfg
 from bufunfa.openstack.common import log
+from bufunfa.storage.base import StorageEngine
 
 LOG = log.getLogger(__name__)
 
-DRIVER_NAMESPACE = 'bufunfa.storage'
-
 cfg.CONF.register_opts([
     cfg.StrOpt('database_connection',
                default='sqlite:///$state_path/bufunfa.db',
@@ -42,13 +40,8 @@ def get_engine_name(string):
 def get_engine(conf):
     scheme = urlparse(conf.database_connection).scheme
     engine_name = get_engine_name(scheme)
-    LOG.debug('looking for %r engine in %r', engine_name, DRIVER_NAMESPACE)
-    mgr = driver.DriverManager(
-        DRIVER_NAMESPACE,
-        engine_name,
-        invoke_on_load=False)
-    mgr.driver.register_opts(conf)
-    return mgr.driver()
+    return StorageEngine.get_plugin(
+        engine_name, conf=conf, invoke_on_load=True)
 
 
 def get_connection(conf):

bufunfa/storage/base.py

@@ -23,6 +23,7 @@ class StorageEngine(Plugin):
     Base class for storage engines
     """
 
+    __plugin_ns__ = 'bufunfa.storage'
     __plugin_type__ = 'storage'
 
     @abc.abstractmethod