Move common libs to libs/common

libs/common/stevedore/enabled.py

@@ -0,0 +1,84 @@
+#  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 logging
+
+from .extension import ExtensionManager
+
+
+LOG = logging.getLogger(__name__)
+
+
+class EnabledExtensionManager(ExtensionManager):
+    """Loads only plugins that pass a check function.
+
+    The check_func argument should return a boolean, with ``True``
+    indicating that the extension should be loaded and made available
+    and ``False`` indicating that the extension should be ignored.
+
+    :param namespace: The namespace for the entry points.
+    :type namespace: str
+    :param check_func: Function to determine which extensions to load.
+    :type check_func: callable, taking an :class:`Extension`
+        instance as argument
+    :param invoke_on_load: Boolean controlling whether to invoke the
+        object returned by the entry point after the driver is loaded.
+    :type invoke_on_load: bool
+    :param invoke_args: Positional arguments to pass when invoking
+        the object returned by the entry point. Only used if invoke_on_load
+        is True.
+    :type invoke_args: tuple
+    :param invoke_kwds: Named arguments to pass when invoking
+        the object returned by the entry point. Only used if invoke_on_load
+        is True.
+    :type invoke_kwds: dict
+    :param propagate_map_exceptions: Boolean controlling whether exceptions
+        are propagated up through the map call or whether they are logged and
+        then ignored
+    :type propagate_map_exceptions: bool
+    :param on_load_failure_callback: Callback function that will be called when
+        a entrypoint can not be loaded. The arguments that will be provided
+        when this is called (when an entrypoint fails to load) are
+        (manager, entrypoint, exception)
+    :type on_load_failure_callback: function
+    :param verify_requirements: Use setuptools to enforce the
+        dependencies of the plugin(s) being loaded. Defaults to False.
+    :type verify_requirements: bool
+
+    """
+
+    def __init__(self, namespace, check_func, invoke_on_load=False,
+                 invoke_args=(), invoke_kwds={},
+                 propagate_map_exceptions=False,
+                 on_load_failure_callback=None,
+                 verify_requirements=False,):
+        self.check_func = check_func
+        super(EnabledExtensionManager, self).__init__(
+            namespace,
+            invoke_on_load=invoke_on_load,
+            invoke_args=invoke_args,
+            invoke_kwds=invoke_kwds,
+            propagate_map_exceptions=propagate_map_exceptions,
+            on_load_failure_callback=on_load_failure_callback,
+            verify_requirements=verify_requirements,
+        )
+
+    def _load_one_plugin(self, ep, invoke_on_load, invoke_args, invoke_kwds,
+                         verify_requirements):
+        ext = super(EnabledExtensionManager, self)._load_one_plugin(
+            ep, invoke_on_load, invoke_args, invoke_kwds,
+            verify_requirements,
+        )
+        if ext and not self.check_func(ext):
+            LOG.debug('ignoring extension %r', ep.name)
+            return None
+        return ext