Refactoring of extensions

This is a refactoring of API extensions.  Changes include better use
of Python idioms and improved support for loading extensions.

Change-Id: I9279c4e5781f049ab9e0e995f6aeda48f17c5831

25 files changed, 291 insertions, 461 deletions

diff --git a/nova/api/openstack/contrib/__init__.py b/nova/api/openstack/contrib/__init__.py
index acb5eb280..b3d4df69b 100644
--- a/nova/api/openstack/contrib/__init__.py
+++ b/nova/api/openstack/contrib/__init__.py
@@ -20,3 +20,71 @@
 It can't be called 'extensions' because that causes namespacing problems.
 
 """
+
+import os
+
+from nova import exception
+from nova import log as logging
+from nova import utils
+
+
+LOG = logging.getLogger('nova.api.openstack.contrib')
+
+
+def standard_extensions(ext_mgr):
+    """Registers all standard API extensions."""
+
+    # Walk through all the modules in our directory...
+    our_dir = __path__[0]
+    for dirpath, dirnames, filenames in os.walk(our_dir):
+        # Compute the relative package name from the dirpath
+        relpath = os.path.relpath(dirpath, our_dir)
+        if relpath == '.':
+            relpkg = ''
+        else:
+            relpkg = '.%s' % '.'.join(relpath.split(os.sep))
+
+        # Now, consider each file in turn, only considering .py files
+        for fname in filenames:
+            root, ext = os.path.splitext(fname)
+
+            # Skip __init__ and anything that's not .py
+            if ext != '.py' or root == '__init__':
+                continue
+
+            # Try loading it
+            classname = ("%s%s.%s.%s%s" %
+                         (__package__, relpkg, root,
+                          root[0].upper(), root[1:]))
+            try:
+                ext_mgr.load_extension(classname)
+            except Exception as exc:
+                LOG.warn(_('Failed to load extension %(classname)s: '
+                           '%(exc)s') % locals())
+
+        # Now, let's consider any subdirectories we may have...
+        subdirs = []
+        for dname in dirnames:
+            # Skip it if it does not have __init__.py
+            if not os.path.exists(os.path.join(dirpath, dname,
+                                               '__init__.py')):
+                continue
+
+            # If it has extension(), delegate...
+            ext_name = ("%s%s.%s.extension" %
+                        (__package__, relpkg, dname))
+            try:
+                ext = utils.import_class(ext_name)
+            except exception.ClassNotFound:
+                # extension() doesn't exist on it, so we'll explore
+                # the directory for ourselves
+                subdirs.append(dname)
+            else:
+                try:
+                    ext(ext_mgr)
+                except Exception as exc:
+                    LOG.warn(_('Failed to load extension %(ext_name)s: '
+                               '%(exc)s') % locals())
+
+        # Update the list of directories we'll explore...
+        dirnames[:] = subdirs
diff --git a/nova/api/openstack/contrib/admin_actions.py b/nova/api/openstack/contrib/admin_actions.py
index be00eaf29..f501e9a41 100644
--- a/nova/api/openstack/contrib/admin_actions.py
+++ b/nova/api/openstack/contrib/admin_actions.py
@@ -34,10 +34,17 @@ LOG = logging.getLogger("nova.api.openstack.contrib.admin_actions")
 
 
 class Admin_actions(extensions.ExtensionDescriptor):
-    """Adds a set of admin-only actions to servers"""
+    """Adds admin-only server actions: pause, unpause, suspend,
+    resume, migrate, resetNetwork, injectNetworkInfo, lock and unlock
+    """
 
-    def __init__(self):
-        super(Admin_actions, self).__init__()
+    name = "AdminActions"
+    alias = "os-admin-actions"
+    namespace = "http://docs.openstack.org/ext/admin-actions/api/v1.1"
+    updated = "2011-09-20T00:00:00+00:00"
+
+    def __init__(self, ext_mgr):
+        super(Admin_actions, self).__init__(ext_mgr)
         self.compute_api = compute.API()
 
     @extensions.admin_only
@@ -164,23 +171,6 @@ class Admin_actions(extensions.ExtensionDescriptor):
             raise exc.HTTPUnprocessableEntity()
         return webob.Response(status_int=202)
 
-    def get_name(self):
-        return "AdminActions"
-
-    def get_alias(self):
-        return "os-admin-actions"
-
-    def get_description(self):
-        return "Adds admin-only server actions: pause, unpause, " + \
-               "suspend, resume, migrate, resetNetwork, " +\
-               "injectNetworkInfo, lock and unlock"
-
-    def get_namespace(self):
-        return "http://docs.openstack.org/ext/admin-actions/api/v1.1"
-
-    def get_updated(self):
-        return "2011-09-20T00:00:00+00:00"
-
     def get_actions(self):
         actions = [
             extensions.ActionExtension("servers", "pause", self._pause),
diff --git a/nova/api/openstack/contrib/createserverext.py b/nova/api/openstack/contrib/createserverext.py
index 7546bdeaa..da95164e8 100644
--- a/nova/api/openstack/contrib/createserverext.py
+++ b/nova/api/openstack/contrib/createserverext.py
@@ -40,21 +40,12 @@ class CreateServerController(servers.Controller):
 
 
 class Createserverext(extensions.ExtensionDescriptor):
-    """The servers create ext"""
-    def get_name(self):
-        return "Createserverext"
+    """Extended support to the Create Server v1.1 API"""
 
-    def get_alias(self):
-        return "os-create-server-ext"
-
-    def get_description(self):
-        return "Extended support to the Create Server v1.1 API"
-
-    def get_namespace(self):
-        return "http://docs.openstack.org/ext/createserverext/api/v1.1"
-
-    def get_updated(self):
-        return "2011-07-19T00:00:00+00:00"
+    name = "Createserverext"
+    alias = "os-create-server-ext"
+    namespace = "http://docs.openstack.org/ext/createserverext/api/v1.1"
+    updated = "2011-07-19T00:00:00+00:00"
 
     def get_resources(self):
         resources = []
diff --git a/nova/api/openstack/contrib/deferred_delete.py b/nova/api/openstack/contrib/deferred_delete.py
index 13ee5511e..58223e901 100644
--- a/nova/api/openstack/contrib/deferred_delete.py
+++ b/nova/api/openstack/contrib/deferred_delete.py
@@ -31,8 +31,15 @@ LOG = logging.getLogger("nova.api.contrib.deferred-delete")
 
 
 class Deferred_delete(extensions.ExtensionDescriptor):
-    def __init__(self):
-        super(Deferred_delete, self).__init__()
+    """Instance deferred delete"""
+
+    name = "DeferredDelete"
+    alias = "os-deferred-delete"
+    namespace = "http://docs.openstack.org/ext/deferred-delete/api/v1.1"
+    updated = "2011-09-01T00:00:00+00:00"
+
+    def __init__(self, ext_mgr):
+        super(Deferred_delete, self).__init__(ext_mgr)
         self.compute_api = compute.API()
 
     def _restore(self, input_dict, req, instance_id):
@@ -49,21 +56,6 @@ class Deferred_delete(extensions.ExtensionDescriptor):
         self.compute_api.force_delete(context, instance_id)
         return webob.Response(status_int=202)
 
-    def get_name(self):
-        return "DeferredDelete"
-
-    def get_alias(self):
-        return "os-deferred-delete"
-
-    def get_description(self):
-        return "Instance deferred delete"
-
-    def get_namespace(self):
-        return "http://docs.openstack.org/ext/deferred-delete/api/v1.1"
-
-    def get_updated(self):
-        return "2011-09-01T00:00:00+00:00"
-
     def get_actions(self):
         """Return the actions the extension adds, as required by contract."""
         actions = [
diff --git a/nova/api/openstack/contrib/diskconfig.py b/nova/api/openstack/contrib/diskconfig.py
index 5173050fd..2225a30fb 100644
--- a/nova/api/openstack/contrib/diskconfig.py
+++ b/nova/api/openstack/contrib/diskconfig.py
@@ -92,23 +92,12 @@ class ImageDiskConfigController(object):
 
 
 class Diskconfig(extensions.ExtensionDescriptor):
-    def __init__(self):
-        super(Diskconfig, self).__init__()
-
-    def get_name(self):
-        return "DiskConfig"
-
-    def get_alias(self):
-        return "OS-DCFG"
-
-    def get_description(self):
-        return "Disk Configuration support"
-
-    def get_namespace(self):
-        return "http://docs.openstack.org/ext/disk_config/api/v1.1"
+    """Disk Configuration support"""
 
-    def get_updated(self):
-        return "2011-08-31T00:00:00+00:00"
+    name = "DiskConfig"
+    alias = "OS-DCFG"
+    namespace = "http://docs.openstack.org/ext/disk_config/api/v1.1"
+    updated = "2011-08-31T00:00:00+00:00"
 
     def _server_extension_controller(self):
         metadata = {
diff --git a/nova/api/openstack/contrib/flavorextradata.py b/nova/api/openstack/contrib/flavorextradata.py
index d0554c7b4..f696d161b 100644
--- a/nova/api/openstack/contrib/flavorextradata.py
+++ b/nova/api/openstack/contrib/flavorextradata.py
@@ -26,21 +26,11 @@ from nova.api.openstack import extensions
 
 
 class Flavorextradata(extensions.ExtensionDescriptor):
-    """The Flavor extra data extension for the OpenStack API."""
+    """Provide additional data for flavors"""
 
-    def get_name(self):
-        return "FlavorExtraData"
-
-    def get_alias(self):
-        return "os-flavor-extra-data"
-
-    def get_description(self):
-        return "Provide additional data for flavors"
-
-    def get_namespace(self):
-        return "http://docs.openstack.org/ext/flavor_extra_data/api/v1.1"
-
-    def get_updated(self):
-        return "2011-09-14T00:00:00+00:00"
+    name = "FlavorExtraData"
+    alias = "os-flavor-extra-data"
+    namespace = "http://docs.openstack.org/ext/flavor_extra_data/api/v1.1"
+    updated = "2011-09-14T00:00:00+00:00"
 
 # vim: tabstop=4 shiftwidth=4 softtabstop=4
diff --git a/nova/api/openstack/contrib/flavorextraspecs.py b/nova/api/openstack/contrib/flavorextraspecs.py
index 2d897a1da..8d2bea88a 100644
--- a/nova/api/openstack/contrib/flavorextraspecs.py
+++ b/nova/api/openstack/contrib/flavorextraspecs.py
@@ -98,22 +98,12 @@ class FlavorExtraSpecsController(object):
 
 
 class Flavorextraspecs(extensions.ExtensionDescriptor):
+    """Instance type (flavor) extra specs"""
 
-    def get_name(self):
-        return "FlavorExtraSpecs"
-
-    def get_alias(self):
-        return "os-flavor-extra-specs"
-
-    def get_description(self):
-        return "Instance type (flavor) extra specs"
-
-    def get_namespace(self):
-        return \
-         "http://docs.openstack.org/ext/flavor_extra_specs/api/v1.1"
-
-    def get_updated(self):
-        return "2011-06-23T00:00:00+00:00"
+    name = "FlavorExtraSpecs"
+    alias = "os-flavor-extra-specs"
+    namespace = "http://docs.openstack.org/ext/flavor_extra_specs/api/v1.1"
+    updated = "2011-06-23T00:00:00+00:00"
 
     def get_resources(self):
         resources = []
diff --git a/nova/api/openstack/contrib/floating_ips.py b/nova/api/openstack/contrib/floating_ips.py
index 22d7d1a1d..c6d0a80d2 100644
--- a/nova/api/openstack/contrib/floating_ips.py
+++ b/nova/api/openstack/contrib/floating_ips.py
@@ -121,10 +121,17 @@ class FloatingIPController(object):
 
 
 class Floating_ips(extensions.ExtensionDescriptor):
-    def __init__(self):
+    """Floating IPs support"""
+
+    name = "Floating_ips"
+    alias = "os-floating-ips"
+    namespace = "http://docs.openstack.org/ext/floating_ips/api/v1.1"
+    updated = "2011-06-16T00:00:00+00:00"
+
+    def __init__(self, ext_mgr):
         self.compute_api = compute.API()
         self.network_api = network.API()
-        super(Floating_ips, self).__init__()
+        super(Floating_ips, self).__init__(ext_mgr)
 
     def _add_floating_ip(self, input_dict, req, instance_id):
         """Associate floating_ip to an instance."""
@@ -172,21 +179,6 @@ class Floating_ips(extensions.ExtensionDescriptor):
 
         return webob.Response(status_int=202)
 
-    def get_name(self):
-        return "Floating_ips"
-
-    def get_alias(self):
-        return "os-floating-ips"
-
-    def get_description(self):
-        return "Floating IPs support"
-
-    def get_namespace(self):
-        return "http://docs.openstack.org/ext/floating_ips/api/v1.1"
-
-    def get_updated(self):
-        return "2011-06-16T00:00:00+00:00"
-
     def get_resources(self):
         resources = []
 
diff --git a/nova/api/openstack/contrib/hosts.py b/nova/api/openstack/contrib/hosts.py
index 4cd908370..736843c3d 100644
--- a/nova/api/openstack/contrib/hosts.py
+++ b/nova/api/openstack/contrib/hosts.py
@@ -118,20 +118,12 @@ class HostController(object):
 
 
 class Hosts(extensions.ExtensionDescriptor):
-    def get_name(self):
-        return "Hosts"
+    """Host administration"""
 
-    def get_alias(self):
-        return "os-hosts"
-
-    def get_description(self):
-        return "Host administration"
-
-    def get_namespace(self):
-        return "http://docs.openstack.org/ext/hosts/api/v1.1"
-
-    def get_updated(self):
-        return "2011-06-29T00:00:00+00:00"
+    name = "Hosts"
+    alias = "os-hosts"
+    namespace = "http://docs.openstack.org/ext/hosts/api/v1.1"
+    updated = "2011-06-29T00:00:00+00:00"
 
     def get_resources(self):
         resources = [extensions.ResourceExtension('os-hosts',
diff --git a/nova/api/openstack/contrib/keypairs.py b/nova/api/openstack/contrib/keypairs.py
index 201648ab5..c7965b8c4 100644
--- a/nova/api/openstack/contrib/keypairs.py
+++ b/nova/api/openstack/contrib/keypairs.py
@@ -117,22 +117,12 @@ class KeypairController(object):
 
 
 class Keypairs(extensions.ExtensionDescriptor):
+    """Keypair Support"""
 
-    def get_name(self):
-        return "Keypairs"
-
-    def get_alias(self):
-        return "os-keypairs"
-
-    def get_description(self):
-        return "Keypair Support"
-
-    def get_namespace(self):
-        return \
-         "http://docs.openstack.org/ext/keypairs/api/v1.1"
-
-    def get_updated(self):
-        return "2011-08-08T00:00:00+00:00"
+    name = "Keypairs"
+    alias = "os-keypairs"
+    namespace = "http://docs.openstack.org/ext/keypairs/api/v1.1"
+    updated = "2011-08-08T00:00:00+00:00"
 
     def get_resources(self):
         resources = []
diff --git a/nova/api/openstack/contrib/multinic.py b/nova/api/openstack/contrib/multinic.py
index da8dcee5d..c39b87b84 100644
--- a/nova/api/openstack/contrib/multinic.py
+++ b/nova/api/openstack/contrib/multinic.py
@@ -30,47 +30,23 @@ LOG = logging.getLogger("nova.api.multinic")
 # Note: The class name is as it has to be for this to be loaded as an
 # extension--only first character capitalized.
 class Multinic(extensions.ExtensionDescriptor):
-    """The multinic extension.
+    """Multiple network support"""
 
-    Exposes addFixedIp and removeFixedIp actions on servers.
+    name = "Multinic"
+    alias = "NMN"
+    namespace = "http://docs.openstack.org/ext/multinic/api/v1.1"
+    updated = "2011-06-09T00:00:00+00:00"
 
-    """
-
-    def __init__(self, *args, **kwargs):
+    def __init__(self, ext_mgr):
         """Initialize the extension.
 
         Gets a compute.API object so we can call the back-end
         add_fixed_ip() and remove_fixed_ip() methods.
         """
 
-        super(Multinic, self).__init__(*args, **kwargs)
+        super(Multinic, self).__init__(ext_mgr)
         self.compute_api = compute.API()
 
-    def get_name(self):
-        """Return the extension name, as required by contract."""
-
-        return "Multinic"
-
-    def get_alias(self):
-        """Return the extension alias, as required by contract."""
-
-        return "NMN"
-
-    def get_description(self):
-        """Return the extension description, as required by contract."""
-
-        return "Multiple network support"
-
-    def get_namespace(self):
-        """Return the namespace, as required by contract."""
-
-        return "http://docs.openstack.org/ext/multinic/api/v1.1"
-
-    def get_updated(self):
-        """Return the last updated timestamp, as required by contract."""
-
-        return "2011-06-09T00:00:00+00:00"
-
     def get_actions(self):
         """Return the actions the extension adds, as required by contract."""
 
diff --git a/nova/api/openstack/contrib/quotas.py b/nova/api/openstack/contrib/quotas.py
index 459b71dfd..83d75394a 100644
--- a/nova/api/openstack/contrib/quotas.py
+++ b/nova/api/openstack/contrib/quotas.py
@@ -73,21 +73,12 @@ class QuotaSetsController(object):
 
 
 class Quotas(extensions.ExtensionDescriptor):
+    """Quotas management support"""
 
-    def get_name(self):
-        return "Quotas"
-
-    def get_alias(self):
-        return "os-quota-sets"
-
-    def get_description(self):
-        return "Quotas management support"
-
-    def get_namespace(self):
-        return "http://docs.openstack.org/ext/quotas-sets/api/v1.1"
-
-    def get_updated(self):
-        return "2011-08-08T00:00:00+00:00"
+    name = "Quotas"
+    alias = "os-quota-sets"
+    namespace = "http://docs.openstack.org/ext/quotas-sets/api/v1.1"
+    updated = "2011-08-08T00:00:00+00:00"
 
     def get_resources(self):
         resources = []
diff --git a/nova/api/openstack/contrib/rescue.py b/nova/api/openstack/contrib/rescue.py
index 3e3459bfe..4e1beb0ba 100644
--- a/nova/api/openstack/contrib/rescue.py
+++ b/nova/api/openstack/contrib/rescue.py
@@ -30,9 +30,15 @@ LOG = logging.getLogger("nova.api.contrib.rescue")
 
 
 class Rescue(exts.ExtensionDescriptor):
-    """The Rescue controller for the OpenStack API."""
-    def __init__(self):
-        super(Rescue, self).__init__()
+    """Instance rescue mode"""
+
+    name = "Rescue"
+    alias = "os-rescue"
+    namespace = "http://docs.openstack.org/ext/rescue/api/v1.1"
+    updated = "2011-08-18T00:00:00+00:00"
+
+    def __init__(self, ext_mgr):
+        super(Rescue, self).__init__(ext_mgr)
         self.compute_api = compute.API()
 
     @exts.wrap_errors
@@ -55,21 +61,6 @@ class Rescue(exts.ExtensionDescriptor):
 
         return webob.Response(status_int=202)
 
-    def get_name(self):
-        return "Rescue"
-
-    def get_alias(self):
-        return "os-rescue"
-
-    def get_description(self):
-        return "Instance rescue mode"
-
-    def get_namespace(self):
-        return "http://docs.openstack.org/ext/rescue/api/v1.1"
-
-    def get_updated(self):
-        return "2011-08-18T00:00:00+00:00"
-
     def get_actions(self):
         """Return the actions the extension adds, as required by contract."""
         actions = [
diff --git a/nova/api/openstack/contrib/security_groups.py b/nova/api/openstack/contrib/security_groups.py
index 1fd64f3b8..dd8333525 100644
--- a/nova/api/openstack/contrib/security_groups.py
+++ b/nova/api/openstack/contrib/security_groups.py
@@ -332,25 +332,16 @@ class SecurityGroupRulesController(SecurityGroupController):
 
 
 class Security_groups(extensions.ExtensionDescriptor):
+    """Security group support"""
 
-    def __init__(self):
-        self.compute_api = compute.API()
-        super(Security_groups, self).__init__()
-
-    def get_name(self):
-        return "SecurityGroups"
-
-    def get_alias(self):
-        return "security_groups"
+    name = "SecurityGroups"
+    alias = "security_groups"
+    namespace = "http://docs.openstack.org/ext/securitygroups/api/v1.1"
+    updated = "2011-07-21T00:00:00+00:00"
 
-    def get_description(self):
-        return "Security group support"
-
-    def get_namespace(self):
-        return "http://docs.openstack.org/ext/securitygroups/api/v1.1"
-
-    def get_updated(self):
-        return "2011-07-21T00:00:00+00:00"
+    def __init__(self, ext_mgr):
+        self.compute_api = compute.API()
+        super(Security_groups, self).__init__(ext_mgr)
 
     def _addSecurityGroup(self, input_dict, req, instance_id):
         context = req.environ['nova.context']
diff --git a/nova/api/openstack/contrib/simple_tenant_usage.py b/nova/api/openstack/contrib/simple_tenant_usage.py
index 42691a9fa..3399ac2be 100644
--- a/nova/api/openstack/contrib/simple_tenant_usage.py
+++ b/nova/api/openstack/contrib/simple_tenant_usage.py
@@ -211,20 +211,12 @@ class SimpleTenantUsageController(object):
 
 
 class Simple_tenant_usage(extensions.ExtensionDescriptor):
-    def get_name(self):
-        return "SimpleTenantUsage"
+    """Simple tenant usage extension"""
 
-    def get_alias(self):
-        return "os-simple-tenant-usage"
-
-    def get_description(self):
-        return "Simple tenant usage extension"
-
-    def get_namespace(self):
-        return "http://docs.openstack.org/ext/os-simple-tenant-usage/api/v1.1"
-
-    def get_updated(self):
-        return "2011-08-19T00:00:00+00:00"
+    name = "SimpleTenantUsage"
+    alias = "os-simple-tenant-usage"
+    namespace = "http://docs.openstack.org/ext/os-simple-tenant-usage/api/v1.1"
+    updated = "2011-08-19T00:00:00+00:00"
 
     def get_resources(self):
         resources = []
diff --git a/nova/api/openstack/contrib/virtual_interfaces.py b/nova/api/openstack/contrib/virtual_interfaces.py
index 1981cd372..0afd2119d 100644
--- a/nova/api/openstack/contrib/virtual_interfaces.py
+++ b/nova/api/openstack/contrib/virtual_interfaces.py
@@ -64,21 +64,12 @@ class ServerVirtualInterfaceController(object):
 
 
 class Virtual_interfaces(extensions.ExtensionDescriptor):
+    """Virtual interface support"""
 
-    def get_name(self):
-        return "VirtualInterfaces"
-
-    def get_alias(self):
-        return "virtual_interfaces"
-
-    def get_description(self):
-        return "Virtual interface support"
-
-    def get_namespace(self):
-        return "http://docs.openstack.org/ext/virtual_interfaces/api/v1.1"
-
-    def get_updated(self):
-        return "2011-08-17T00:00:00+00:00"
+    name = "VirtualInterfaces"
+    alias = "virtual_interfaces"
+    namespace = "http://docs.openstack.org/ext/virtual_interfaces/api/v1.1"
+    updated = "2011-08-17T00:00:00+00:00"
 
     def get_resources(self):
         resources = []
diff --git a/nova/api/openstack/contrib/virtual_storage_arrays.py b/nova/api/openstack/contrib/virtual_storage_arrays.py
index ca219cfa8..5c5afdd22 100644
--- a/nova/api/openstack/contrib/virtual_storage_arrays.py
+++ b/nova/api/openstack/contrib/virtual_storage_arrays.py
@@ -545,21 +545,12 @@ class VsaVCController(servers.Controller):
 
 
 class Virtual_storage_arrays(extensions.ExtensionDescriptor):
+    """Virtual Storage Arrays support"""
 
-    def get_name(self):
-        return "VSAs"
-
-    def get_alias(self):
-        return "zadr-vsa"
-
-    def get_description(self):
-        return "Virtual Storage Arrays support"
-
-    def get_namespace(self):
-        return "http://docs.openstack.org/ext/vsa/api/v1.1"
-
-    def get_updated(self):
-        return "2011-08-25T00:00:00+00:00"
+    name = "VSAs"
+    alias = "zadr-vsa"
+    namespace = "http://docs.openstack.org/ext/vsa/api/v1.1"
+    updated = "2011-08-25T00:00:00+00:00"
 
     def get_resources(self):
         resources = []
diff --git a/nova/api/openstack/contrib/volumes.py b/nova/api/openstack/contrib/volumes.py
index 50a1e42ab..f706ebfe1 100644
--- a/nova/api/openstack/contrib/volumes.py
+++ b/nova/api/openstack/contrib/volumes.py
@@ -339,20 +339,12 @@ class BootFromVolumeController(servers.Controller):
 
 
 class Volumes(extensions.ExtensionDescriptor):
-    def get_name(self):
-        return "Volumes"
+    """Volumes support"""
 
-    def get_alias(self):
-        return "os-volumes"
-
-    def get_description(self):
-        return "Volumes support"
-
-    def get_namespace(self):
-        return "http://docs.openstack.org/ext/volumes/api/v1.1"
-
-    def get_updated(self):
-        return "2011-03-25T00:00:00+00:00"
+    name = "Volumes"
+    alias = "os-volumes"
+    namespace = "http://docs.openstack.org/ext/volumes/api/v1.1"
+    updated = "2011-03-25T00:00:00+00:00"
 
     def get_resources(self):
         resources = []
diff --git a/nova/api/openstack/contrib/volumetypes.py b/nova/api/openstack/contrib/volumetypes.py
index ed33a8819..947dcad2d 100644
--- a/nova/api/openstack/contrib/volumetypes.py
+++ b/nova/api/openstack/contrib/volumetypes.py
@@ -163,22 +163,12 @@ class VolumeTypeExtraSpecsController(object):
 
 
 class Volumetypes(extensions.ExtensionDescriptor):
+    """Volume types support"""
 
-    def get_name(self):
-        return "VolumeTypes"
-
-    def get_alias(self):
-        return "os-volume-types"
-
-    def get_description(self):
-        return "Volume types support"
-
-    def get_namespace(self):
-        return \
-         "http://docs.openstack.org/ext/volume_types/api/v1.1"
-
-    def get_updated(self):
-        return "2011-08-24T00:00:00+00:00"
+    name = "VolumeTypes"
+    alias = "os-volume-types"
+    namespace = "http://docs.openstack.org/ext/volume_types/api/v1.1"
+    updated = "2011-08-24T00:00:00+00:00"
 
     def get_resources(self):
         resources = []
diff --git a/nova/api/openstack/contrib/zones.py b/nova/api/openstack/contrib/zones.py
index 5901e321e..628b8182f 100644
--- a/nova/api/openstack/contrib/zones.py
+++ b/nova/api/openstack/contrib/zones.py
@@ -28,22 +28,15 @@ FLAGS = flags.FLAGS
 
 
 class Zones(extensions.ExtensionDescriptor):
-    def get_name(self):
-        return "Zones"
-
-    def get_alias(self):
-        return "os-zones"
-
-    def get_description(self):
-        return """Enables zones-related functionality such as adding
-child zones, listing child zones, getting the capabilities of the
-local zone, and returning build plans to parent zones' schedulers"""
-
-    def get_namespace(self):
-        return "http://docs.openstack.org/ext/zones/api/v1.1"
-
-    def get_updated(self):
-        return "2011-09-21T00:00:00+00:00"
+    """Enables zones-related functionality such as adding child zones,
+    listing child zones, getting the capabilities of the local zone,
+    and returning build plans to parent zones' schedulers
+    """
+
+    name = "Zones"
+    alias = "os-zones"
+    namespace = "http://docs.openstack.org/ext/zones/api/v1.1"
+    updated = "2011-09-21T00:00:00+00:00"
 
     def get_resources(self):
         # Nothing yet.
diff --git a/nova/api/openstack/extensions.py b/nova/api/openstack/extensions.py
index 6eb085d09..23e8f71ed 100644
--- a/nova/api/openstack/extensions.py
+++ b/nova/api/openstack/extensions.py
@@ -53,46 +53,26 @@ class ExtensionDescriptor(object):
 
     """
 
-    def get_name(self):
-        """The name of the extension.
+    # The name of the extension, e.g., 'Fox In Socks'
+    name = None
 
-        e.g. 'Fox In Socks'
+    # The alias for the extension, e.g., 'FOXNSOX'
+    alias = None
 
-        """
-        raise NotImplementedError()
-
-    def get_alias(self):
-        """The alias for the extension.
+    # Description comes from the docstring for the class
 
-        e.g. 'FOXNSOX'
+    # The XML namespace for the extension, e.g.,
+    # 'http://www.fox.in.socks/api/ext/pie/v1.0'
+    namespace = None
 
-        """
-        raise NotImplementedError()
+    # The timestamp when the extension was last updated, e.g.,
+    # '2011-01-22T13:25:27-06:00'
+    updated = None
 
-    def get_description(self):
-        """Friendly description for the extension.
+    def __init__(self, ext_mgr):
+        """Register extension with the extension manager."""
 
-        e.g. 'The Fox In Socks Extension'
-
-        """
-        raise NotImplementedError()
-
-    def get_namespace(self):
-        """The XML namespace for the extension.
-
-        e.g. 'http://www.fox.in.socks/api/ext/pie/v1.0'
-
-        """
-        raise NotImplementedError()
-
-    def get_updated(self):
-        """The timestamp when the extension was last updated.
-
-        e.g. '2011-01-22T13:25:27-06:00'
-
-        """
-        # NOTE(justinsb): Not sure of the purpose of this is, vs the XML NS
-        raise NotImplementedError()
+        ext_mgr.register(self)
 
     def get_resources(self):
         """List of extensions.ResourceExtension extension objects.
@@ -194,11 +174,11 @@ class ExtensionsResource(wsgi.Resource):
 
     def _translate(self, ext):
         ext_data = {}
-        ext_data['name'] = ext.get_name()
-        ext_data['alias'] = ext.get_alias()
-        ext_data['description'] = ext.get_description()
-        ext_data['namespace'] = ext.get_namespace()
-        ext_data['updated'] = ext.get_updated()
+        ext_data['name'] = ext.name
+        ext_data['alias'] = ext.alias
+        ext_data['description'] = ext.__doc__
+        ext_data['namespace'] = ext.namespace
+        ext_data['updated'] = ext.updated
         ext_data['links'] = []  # TODO(dprince): implement extension links
         return ext_data
 
@@ -275,7 +255,7 @@ class ExtensionMiddleware(base_wsgi.Middleware):
     def __init__(self, application, ext_mgr=None):
 
         if ext_mgr is None:
-            ext_mgr = ExtensionManager(FLAGS.osapi_extensions_path)
+            ext_mgr = ExtensionManager()
         self.ext_mgr = ext_mgr
 
         mapper = nova.api.openstack.ProjectMapper()
@@ -352,19 +332,30 @@ class ExtensionManager(object):
 
     """
 
-    def __init__(self, path):
+    def __init__(self):
         LOG.audit(_('Initializing extension manager.'))
 
-        self.path = path
         self.extensions = {}
-        self._load_all_extensions()
+        self._load_extensions()
+
+    def register(self, ext):
+        # Do nothing if the extension doesn't check out
+        if not self._check_extension(ext):
+            return
+
+        alias = ext.alias
+        LOG.audit(_('Loaded extension: %s'), alias)
+
+        if alias in self.extensions:
+            raise exception.Error("Found duplicate extension: %s" % alias)
+        self.extensions[alias] = ext
 
     def get_resources(self):
         """Returns a list of ResourceExtension objects."""
         resources = []
         resources.append(ResourceExtension('extensions',
                                             ExtensionsResource(self)))
-        for alias, ext in self.extensions.iteritems():
+        for ext in self.extensions.values():
             try:
                 resources.extend(ext.get_resources())
             except AttributeError:
@@ -376,7 +367,7 @@ class ExtensionManager(object):
     def get_actions(self):
         """Returns a list of ActionExtension objects."""
         actions = []
-        for alias, ext in self.extensions.iteritems():
+        for ext in self.extensions.values():
             try:
                 actions.extend(ext.get_actions())
             except AttributeError:
@@ -388,7 +379,7 @@ class ExtensionManager(object):
     def get_request_extensions(self):
         """Returns a list of RequestExtension objects."""
         request_exts = []
-        for alias, ext in self.extensions.iteritems():
+        for ext in self.extensions.values():
             try:
                 request_exts.extend(ext.get_request_extensions())
             except AttributeError:
@@ -400,66 +391,44 @@ class ExtensionManager(object):
     def _check_extension(self, extension):
         """Checks for required methods in extension objects."""
         try:
-            LOG.debug(_('Ext name: %s'), extension.get_name())
-            LOG.debug(_('Ext alias: %s'), extension.get_alias())
-            LOG.debug(_('Ext description: %s'), extension.get_description())
-            LOG.debug(_('Ext namespace: %s'), extension.get_namespace())
-            LOG.debug(_('Ext updated: %s'), extension.get_updated())
+            LOG.debug(_('Ext name: %s'), extension.name)
+            LOG.debug(_('Ext alias: %s'), extension.alias)
+            LOG.debug(_('Ext description: %s'),
+                      ' '.join(extension.__doc__.strip().split()))
+            LOG.debug(_('Ext namespace: %s'), extension.namespace)
+            LOG.debug(_('Ext updated: %s'), extension.updated)
         except AttributeError as ex:
             LOG.exception(_("Exception loading extension: %s"), unicode(ex))
             return False
         return True
 
-    def _load_all_extensions(self):
-        """Load extensions from the configured path.
+    def load_extension(self, ext_factory):
+        """Execute an extension factory.
 
-        Load extensions from the configured path. The extension name is
-        constructed from the module_name. If your extension module was named
-        widgets.py the extension class within that module should be
-        'Widgets'.
+        Loads an extension.  The 'ext_factory' is the name of a
+        callable that will be imported and called with one
+        argument--the extension manager.  The factory callable is
+        expected to call the register() method at least once.
+        """
 
-        In addition, extensions are loaded from the 'contrib' directory.
+        LOG.debug(_("Loading extension %s"), ext_factory)
 
-        See nova/tests/api/openstack/extensions/foxinsocks.py for an example
-        extension implementation.
+        # Load the factory
+        factory = utils.import_class(ext_factory)
 
-        """
-        if os.path.exists(self.path):
-            self._load_all_extensions_from_path(self.path)
-
-        contrib_path = os.path.join(os.path.dirname(__file__), "contrib")
-        if os.path.exists(contrib_path):
-            self._load_all_extensions_from_path(contrib_path)
-
-    def _load_all_extensions_from_path(self, path):
-        for f in os.listdir(path):
-            LOG.audit(_('Loading extension file: %s'), f)
-            mod_name, file_ext = os.path.splitext(os.path.split(f)[-1])
-            ext_path = os.path.join(path, f)
-            if file_ext.lower() == '.py' and not mod_name.startswith('_'):
-                mod = imp.load_source(mod_name, ext_path)
-                ext_name = mod_name[0].upper() + mod_name[1:]
-                new_ext_class = getattr(mod, ext_name, None)
-                if not new_ext_class:
-                    LOG.warn(_('Did not find expected name '
-                               '"%(ext_name)s" in %(file)s'),
-                             {'ext_name': ext_name,
-                              'file': ext_path})
-                    continue
-                new_ext = new_ext_class()
-                self.add_extension(new_ext)
-
-    def add_extension(self, ext):
-        # Do nothing if the extension doesn't check out
-        if not self._check_extension(ext):
-            return
+        # Call it
+        LOG.debug(_("Calling extension factory %s"), ext_factory)
+        factory(self)
 
-        alias = ext.get_alias()
-        LOG.audit(_('Loaded extension: %s'), alias)
+    def _load_extensions(self):
+        """Load extensions specified on the command line."""
 
-        if alias in self.extensions:
-            raise exception.Error("Found duplicate extension: %s" % alias)
-        self.extensions[alias] = ext
+        for ext_factory in FLAGS.osapi_extension:
+            try:
+                self.load_extension(ext_factory)
+            except Exception as exc:
+                LOG.warn(_('Failed to load extension %(ext_factory)s: '
+                           '%(exc)s') % locals())
 
 
 class RequestExtension(object):
diff --git a/nova/flags.py b/nova/flags.py
index a70a361a8..e98c487aa 100644
--- a/nova/flags.py
+++ b/nova/flags.py
@@ -341,8 +341,9 @@ DEFINE_string('ec2_dmz_host', '$my_ip', 'internal ip of api server')
 DEFINE_integer('ec2_port', 8773, 'cloud controller port')
 DEFINE_string('ec2_scheme', 'http', 'prefix for ec2')
 DEFINE_string('ec2_path', '/services/Cloud', 'suffix for ec2')
-DEFINE_string('osapi_extensions_path', '/var/lib/nova/extensions',
-               'default directory for nova extensions')
+DEFINE_multistring('osapi_extension',
+                   ['nova.api.openstack.contrib.standard_extensions'],
+                   'osapi extension to load')
 DEFINE_string('osapi_host', '$my_ip', 'ip of api server')
 DEFINE_string('osapi_scheme', 'http', 'prefix for openstack')
 DEFINE_integer('osapi_port', 8774, 'OpenStack API port')
diff --git a/nova/tests/api/openstack/extensions/foxinsocks.py b/nova/tests/api/openstack/extensions/foxinsocks.py
index 70556a28d..d72365620 100644
--- a/nova/tests/api/openstack/extensions/foxinsocks.py
+++ b/nova/tests/api/openstack/extensions/foxinsocks.py
@@ -27,24 +27,15 @@ class FoxInSocksController(object):
 
 
 class Foxinsocks(object):
+    """The Fox In Socks Extension"""
 
-    def __init__(self):
-        pass
+    name = "Fox In Socks"
+    alias = "FOXNSOX"
+    namespace = "http://www.fox.in.socks/api/ext/pie/v1.0"
+    updated = "2011-01-22T13:25:27-06:00"
 
-    def get_name(self):
-        return "Fox In Socks"
-
-    def get_alias(self):
-        return "FOXNSOX"
-
-    def get_description(self):
-        return "The Fox In Socks Extension"
-
-    def get_namespace(self):
-        return "http://www.fox.in.socks/api/ext/pie/v1.0"
-
-    def get_updated(self):
-        return "2011-01-22T13:25:27-06:00"
+    def __init__(self, ext_mgr):
+        ext_mgr.register(self)
 
     def get_resources(self):
         resources = []
diff --git a/nova/tests/api/openstack/test_extensions.py b/nova/tests/api/openstack/test_extensions.py
index 92e74e545..f3a9c26e3 100644
--- a/nova/tests/api/openstack/test_extensions.py
+++ b/nova/tests/api/openstack/test_extensions.py
@@ -21,6 +21,7 @@ import webob
 from lxml import etree
 
 from nova import context
+from nova import flags
 from nova import test
 from nova import wsgi as base_wsgi
 from nova.api import openstack
@@ -30,6 +31,8 @@ from nova.api.openstack import wsgi
 from nova.api.openstack import xmlutil
 from nova.tests.api.openstack import fakes
 
+FLAGS = flags.FLAGS
+
 NS = "{http://docs.openstack.org/compute/api/v1.1}"
 ATOMNS = "{http://www.w3.org/2005/Atom}"
 response_body = "Try to say this Mr. Knox, sir..."
@@ -45,21 +48,16 @@ class StubController(object):
 
 
 class StubExtensionManager(object):
+    """Provides access to Tweedle Beetles"""
+
+    name = "Tweedle Beetle Extension"
+    alias = "TWDLBETL"
 
     def __init__(self, resource_ext=None, action_ext=None, request_ext=None):
         self.resource_ext = resource_ext
         self.action_ext = action_ext
         self.request_ext = request_ext
 
-    def get_name(self):
-        return "Tweedle Beetle Extension"
-
-    def get_alias(self):
-        return "TWDLBETL"
-
-    def get_description(self):
-        return "Provides access to Tweedle Beetles"
-
     def get_resources(self):
         resource_exts = []
         if self.resource_ext:
@@ -79,12 +77,19 @@ class StubExtensionManager(object):
         return request_extensions
 
 
-class ExtensionControllerTest(test.TestCase):
+class ExtensionTestCase(test.TestCase):
+    def setUp(self):
+        super(ExtensionTestCase, self).setUp()
+        ext_list = FLAGS.osapi_extension[:]
+        ext_list.append('nova.tests.api.openstack.extensions.'
+                        'foxinsocks.Foxinsocks')
+        self.flags(osapi_extension=ext_list)
+
+
+class ExtensionControllerTest(ExtensionTestCase):
 
     def setUp(self):
         super(ExtensionControllerTest, self).setUp()
-        ext_path = os.path.join(os.path.dirname(__file__), "extensions")
-        self.flags(osapi_extensions_path=ext_path)
         self.ext_list = [
             "AdminActions",
             "Createserverext",
@@ -212,12 +217,7 @@ class ExtensionControllerTest(test.TestCase):
         xmlutil.validate_schema(root, 'extension')
 
 
-class ResourceExtensionTest(test.TestCase):
-
-    def setUp(self):
-        super(ResourceExtensionTest, self).setUp()
-        ext_path = os.path.join(os.path.dirname(__file__), "extensions")
-        self.flags(osapi_extensions_path=ext_path)
+class ResourceExtensionTest(ExtensionTestCase):
 
     def test_no_extension_present(self):
         manager = StubExtensionManager(None)
@@ -255,19 +255,13 @@ class ResourceExtensionTest(test.TestCase):
 
 class InvalidExtension(object):
 
-    def get_alias(self):
-        return "THIRD"
+    alias = "THIRD"
 
 
-class ExtensionManagerTest(test.TestCase):
+class ExtensionManagerTest(ExtensionTestCase):
 
     response_body = "Try to say this Mr. Knox, sir..."
 
-    def setUp(self):
-        super(ExtensionManagerTest, self).setUp()
-        ext_path = os.path.join(os.path.dirname(__file__), "extensions")
-        self.flags(osapi_extensions_path=ext_path)
-
     def test_get_resources(self):
         app = openstack.APIRouter()
         ext_midware = extensions.ExtensionMiddleware(app)
@@ -283,17 +277,12 @@ class ExtensionManagerTest(test.TestCase):
         app = openstack.APIRouter()
         ext_midware = extensions.ExtensionMiddleware(app)
         ext_mgr = ext_midware.ext_mgr
-        ext_mgr.add_extension(InvalidExtension())
+        ext_mgr.register(InvalidExtension())
         self.assertTrue('FOXNSOX' in ext_mgr.extensions)
         self.assertTrue('THIRD' not in ext_mgr.extensions)
 
 
-class ActionExtensionTest(test.TestCase):
-
-    def setUp(self):
-        super(ActionExtensionTest, self).setUp()
-        ext_path = os.path.join(os.path.dirname(__file__), "extensions")
-        self.flags(osapi_extensions_path=ext_path)
+class ActionExtensionTest(ExtensionTestCase):
 
     def _send_server_action_request(self, url, body):
         app = openstack.APIRouter()
@@ -331,12 +320,7 @@ class ActionExtensionTest(test.TestCase):
         self.assertEqual(404, response.status_int)
 
 
-class RequestExtensionTest(test.TestCase):
-
-    def setUp(self):
-        super(RequestExtensionTest, self).setUp()
-        ext_path = os.path.join(os.path.dirname(__file__), "extensions")
-        self.flags(osapi_extensions_path=ext_path)
+class RequestExtensionTest(ExtensionTestCase):
 
     def test_get_resources_with_stub_mgr(self):
 
diff --git a/nova/tests/integrated/test_extensions.py b/nova/tests/integrated/test_extensions.py
index c22cf0be0..958f584ab 100644
--- a/nova/tests/integrated/test_extensions.py
+++ b/nova/tests/integrated/test_extensions.py
@@ -17,18 +17,21 @@
 
 import os
 
+from nova import flags
 from nova.log import logging
 from nova.tests.integrated import integrated_helpers
 
 
+FLAGS = flags.FLAGS
 LOG = logging.getLogger('nova.tests.integrated')
 
 
 class ExtensionsTest(integrated_helpers._IntegratedTestBase):
     def _get_flags(self):
         f = super(ExtensionsTest, self)._get_flags()
-        f['osapi_extensions_path'] = os.path.join(os.path.dirname(__file__),
-                                                "../api/openstack/extensions")
+        f['osapi_extension'] = FLAGS.osapi_extension[:]
+        f['osapi_extension'].append('nova.tests.api.openstack.extensions.'
+                                    'foxinsocks.Foxinsocks')
         return f
 
     def test_get_foxnsocks(self):