Merge "Lazy import oslo_config as required"

keystoneauth1/loading/_utils.py

@@ -0,0 +1,40 @@
+# 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.
+
+cfg = None
+_NOT_FOUND = object()
+
+
+def get_oslo_config():
+    """Runtime load the oslo.config object.
+
+    In performance optimization of openstackclient it was determined that even
+    optimistically loading oslo.config if available had a performance cost.
+    Given that we used to only raise the ImportError when the function was
+    called also attempt to do the import to do everything at runtime.
+    """
+    global cfg
+
+    # First Call
+    if not cfg:
+        try:
+            from oslo_config import cfg
+        except ImportError:
+            cfg = _NOT_FOUND
+
+    if cfg is _NOT_FOUND:
+        raise ImportError("oslo.config is not an automatic dependency of "
+                          "keystoneauth. If you wish to use oslo.config "
+                          "you need to import it into your application's "
+                          "requirements file. ")
+
+    return cfg

keystoneauth1/loading/opts.py

@@ -15,10 +15,7 @@ import os
 
 from positional import positional
 
-try:
-    from oslo_config import cfg
-except ImportError:
-    cfg = None
+from keystoneauth1.loading import _utils
 
 
 __all__ = ('Opt',)
@@ -99,12 +96,7 @@ class Opt(object):
         return '<Opt: %s>' % self.name
 
     def _to_oslo_opt(self):
-        if not cfg:
-            raise ImportError("oslo.config is not an automatic dependency of "
-                              "keystoneauth. If you wish to use oslo.config "
-                              "you need to import it into your application's "
-                              "requirements file. ")
-
+        cfg = _utils.get_oslo_config()
         deprecated_opts = [cfg.DeprecatedOpt(o.name) for o in self.deprecated]
 
         return cfg.Opt(name=self.name,

keystoneauth1/loading/session.py

@@ -15,11 +15,7 @@ import os
 
 from positional import positional
 
-try:
-    from oslo_config import cfg
-except ImportError:
-    cfg = None
-
+from keystoneauth1.loading import _utils
 from keystoneauth1.loading import base
 from keystoneauth1 import session
 
@@ -160,11 +156,7 @@ class Session(base.BaseLoader):
 
         :returns: A list of oslo_config options.
         """
-        if not cfg:
-            raise ImportError("oslo.config is not an automatic dependency of "
-                              "keystoneauth. If you wish to use oslo.config "
-                              "you need to import it into your application's "
-                              "requirements file. ")
+        cfg = _utils.get_oslo_config()
 
         if deprecated_opts is None:
             deprecated_opts = {}
@@ -214,7 +206,7 @@ class Session(base.BaseLoader):
         :returns: The list of options that was registered.
         """
         opts = self.get_conf_options(deprecated_opts=deprecated_opts)
-        conf.register_group(cfg.OptGroup(group))
+        conf.register_group(_utils.get_oslo_config().OptGroup(group))
         conf.register_opts(opts, group=group)
         return opts