From 3ab91c47708ec6158a7319b9c3a7e357b756df44 Mon Sep 17 00:00:00 2001
From: Rick Harris <rconradharris@gmail.com>
Date: Tue, 8 Oct 2013 21:08:23 +0000
Subject: [PATCH] Use `versionutils.is_compatible` for Nova Objects

Oslo's check is designed to support version checking for a number of different
existing use-cases, including this one.

Related-Oslo-Commit: d7d74a752e34d5249fa47c8e8252da491d46012a
Change-Id: I8e03c7781330b02deb7af815d68538b5c0245c4d
---
 nova/objects/base.py                  | 38 ++++++----------------
 nova/openstack/common/versionutils.py | 45 +++++++++++++++++++++++++++
 openstack-common.conf                 |  1 +
 3 files changed, 55 insertions(+), 29 deletions(-)
 create mode 100644 nova/openstack/common/versionutils.py

diff --git a/nova/objects/base.py b/nova/objects/base.py
index aafe386375ac..24df30f93782 100644
--- a/nova/objects/base.py
+++ b/nova/objects/base.py
@@ -25,6 +25,7 @@ from nova.openstack.common.gettextutils import _
 from nova.openstack.common import log as logging
 from nova.openstack.common.rpc import common as rpc_common
 import nova.openstack.common.rpc.serializer
+from nova.openstack.common import versionutils
 
 
 LOG = logging.getLogger('object')
@@ -149,30 +150,6 @@ def remotable(fn):
     return wrapper
 
 
-# Object versioning rules
-#
-# Each service has its set of objects, each with a version attached. When
-# a client attempts to call an object method, the server checks to see if
-# the version of that object matches (in a compatible way) its object
-# implementation. If so, cool, and if not, fail.
-def check_object_version(server, client):
-    try:
-        client_major, _client_minor = client.split('.')
-        server_major, _server_minor = server.split('.')
-        client_minor = int(_client_minor)
-        server_minor = int(_server_minor)
-    except ValueError:
-        raise exception.IncompatibleObjectVersion(
-            _('Invalid version string'))
-
-    if client_major != server_major:
-        raise exception.IncompatibleObjectVersion(
-            dict(client=client_major, server=server_major))
-    if client_minor > server_minor:
-        raise exception.IncompatibleObjectVersion(
-            dict(client=client_minor, server=server_minor))
-
-
 class NovaObject(object):
     """Base class and object factory.
 
@@ -184,7 +161,12 @@ class NovaObject(object):
     """
     __metaclass__ = NovaObjectMetaclass
 
-    # Version of this object (see rules above check_object_version())
+    # Object versioning rules
+    #
+    # Each service has its set of objects, each with a version attached. When
+    # a client attempts to call an object method, the server checks to see if
+    # the version of that object matches (in a compatible way) its object
+    # implementation. If so, cool, and if not, fail.
     VERSION = '1.0'
 
     # The fields present in this object as key:field pairs. For example:
@@ -218,11 +200,9 @@ class NovaObject(object):
         for objclass in cls._obj_classes[objname]:
             if objclass.VERSION == objver:
                 return objclass
-            try:
-                check_object_version(objclass.VERSION, objver)
+
+            if versionutils.is_compatible(objver, objclass.VERSION):
                 compatible_match = objclass
-            except exception.IncompatibleObjectVersion:
-                pass
 
         if compatible_match:
             return compatible_match
diff --git a/nova/openstack/common/versionutils.py b/nova/openstack/common/versionutils.py
new file mode 100644
index 000000000000..f7b1f8a822aa
--- /dev/null
+++ b/nova/openstack/common/versionutils.py
@@ -0,0 +1,45 @@
+# vim: tabstop=4 shiftwidth=4 softtabstop=4
+
+# Copyright (c) 2013 OpenStack Foundation
+# 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.
+
+"""
+Helpers for comparing version strings.
+"""
+
+import pkg_resources
+
+
+def is_compatible(requested_version, current_version, same_major=True):
+    """Determine whether `requested_version` is satisfied by
+    `current_version`; in other words, `current_version` is >=
+    `requested_version`.
+
+    :param requested_version: version to check for compatibility
+    :param current_version: version to check against
+    :param same_major: if True, the major version must be identical between
+        `requested_version` and `current_version`. This is used when a
+        major-version difference indicates incompatibility between the two
+        versions. Since this is the common-case in practice, the default is
+        True.
+    :returns: True if compatible, False if not
+    """
+    requested_parts = pkg_resources.parse_version(requested_version)
+    current_parts = pkg_resources.parse_version(current_version)
+
+    if same_major and (requested_parts[0] != current_parts[0]):
+        return False
+
+    return current_parts >= requested_parts
diff --git a/openstack-common.conf b/openstack-common.conf
index 151526b95b49..3c05fd65c301 100644
--- a/openstack-common.conf
+++ b/openstack-common.conf
@@ -33,6 +33,7 @@ module=strutils
 module=threadgroup
 module=timeutils
 module=uuidutils
+module=versionutils
 module=xmlutils
 
 # The base module to hold the copy of openstack.common