More Cleanup of code

Moved code in AuthManager init to new so it isn't called multiple times
Changed AuthManager flag to specify class name as well as module name
Added exception for missing auth_driver
Changed import to use "recommended" style for nested imports
  http://docs.python.org/dev/library/functions.html#__import__

bin/nova-dhcpbridge

@@ -78,7 +78,7 @@ def main():
         FLAGS.network_size = 32
         FLAGS.fake_libvirt=True
         FLAGS.fake_network=True
-        FLAGS.auth_driver='nova.auth.fakeldapdriver'
+        FLAGS.auth_driver='nova.auth.ldapdriver.FakeLdapDriver'
     action = argv[1]
     if action in ['add','del','old']:
         mac = argv[2]

nova/auth/fakeldapdriver.py

@@ -1,32 +0,0 @@
-# vim: tabstop=4 shiftwidth=4 softtabstop=4
-
-# Copyright 2010 United States Government as represented by the
-# Administrator of the National Aeronautics and Space Administration.
-# All Rights Reserved.
-#
-#    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.
-
-"""
-Fake Auth driver for ldap
-
-"""
-
-from nova.auth import ldapdriver
-
-class AuthDriver(ldapdriver.AuthDriver):
-    """Ldap Auth driver
-
-    Defines enter and exit and therefore supports the with/as syntax.
-    """
-    def __init__(self):
-        self.ldap = __import__('nova.auth.fakeldap', fromlist=True)

nova/auth/ldapdriver.py

@@ -17,7 +17,7 @@
 #    under the License.
 
 """
-Auth driver for ldap
+Auth driver for ldap.  Includes FakeLdapDriver.
 
 It should be easy to create a replacement for this driver supporting
 other backends by creating another class that exposes the same
@@ -25,6 +25,7 @@ public methods.
 """
 
 import logging
+import sys
 
 from nova import exception
 from nova import flags
@@ -61,7 +62,7 @@ flags.DEFINE_string('ldap_developer',
 #             to define a set interface for AuthDrivers. I'm delaying
 #             creating this now because I'm expecting an auth refactor
 #             in which we may want to change the interface a bit more.
-class AuthDriver(object):
+class LdapDriver(object):
     """Ldap Auth driver
 
     Defines enter and exit and therefore supports the with/as syntax.
@@ -471,3 +472,10 @@ class AuthDriver(object):
         """Convert uid to dn"""
         return 'uid=%s,%s' % (dn, FLAGS.ldap_user_subtree)
 
+
+class FakeLdapDriver(LdapDriver):
+    """Fake Ldap Auth driver"""
+    def __init__(self):
+        __import__('nova.auth.fakeldap')
+        self.ldap = sys.modules['nova.auth.fakeldap']
+

nova/auth/manager.py

@@ -24,6 +24,7 @@ import logging
 import os
 import shutil
 import string
+import sys
 import tempfile
 import uuid
 import zipfile
@@ -75,7 +76,7 @@ flags.DEFINE_string('credential_cert_subject',
 flags.DEFINE_string('vpn_ip', '127.0.0.1',
                     'Public IP for the cloudpipe VPN servers')
 
-flags.DEFINE_string('auth_driver', 'fakeldapdriver',
+flags.DEFINE_string('auth_driver', 'nova.auth.ldapdriver.AuthDriver',
                     'Driver that auth manager uses')
 
 class AuthBase(object):
@@ -320,16 +321,25 @@ class AuthManager(object):
     """
     _instance=None
     def __new__(cls, *args, **kwargs):
+        """Returns the AuthManager singleton with driver set
+
+        __init__ is run every time AuthManager() is called, so we need to do
+        any constructor related stuff here. The driver that is specified
+        in the flagfile is loaded here.
+        """
         if not cls._instance:
             cls._instance = super(AuthManager, cls).__new__(
                     cls, *args, **kwargs)
+            mod_str, sep, driver_str = FLAGS.auth_driver.rpartition('.')
+            try:
+                mod = __import__(mod_str)
+                cls._instance.driver = getattr(sys.modules[mod_str],
+                                               driver_str)
+            except (ImportError, AttributeError):
+                raise exception.Error('Auth driver %s cannot be found'
+                                      % FLAGS.auth_driver)
         return cls._instance
 
-    def __init__(self, *args, **kwargs):
-        """Imports the driver module and saves the Driver class"""
-        mod = __import__(FLAGS.auth_driver, fromlist=True)
-        self.driver = mod.AuthDriver
-
     def authenticate(self, access, signature, params, verb='GET',
                      server_string='127.0.0.1:8773', path='/',
                      verify_signature=True):

nova/tests/fake_flags.py

@@ -24,5 +24,5 @@ FLAGS.fake_libvirt = True
 FLAGS.fake_storage = True
 FLAGS.fake_rabbit = True
 FLAGS.fake_network = True
-FLAGS.auth_driver = 'nova.auth.fakeldapdriver'
+FLAGS.auth_driver = 'nova.auth.ldapdriver.FakeLdapDriver'
 FLAGS.verbose = True

nova/tests/network_unittest.py

@@ -37,7 +37,7 @@ class NetworkTestCase(test.TrialTestCase):
         self.flags(fake_libvirt=True,
                    fake_storage=True,
                    fake_network=True,
-                   auth_driver='nova.auth.fakeldapdriver',
+                   auth_driver='nova.auth.ldapdriver.FakeLdapDriver',
                    network_size=32)
         logging.getLogger().setLevel(logging.DEBUG)
         self.manager = manager.AuthManager()