Add InventoryList.find() method

Needed by following code, this patch adds a simple InventoryList.find()
method that searches for a resource class in an InventoryList and
returns the inventory record matching that resource class, or None if
that resource class is not contained in the InventoryList.

Change-Id: I64757c2115f12788eab46627b0f0a2c8a37433f4

nova/objects/resource_provider.py

@@ -10,6 +10,7 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 
+import six
 from sqlalchemy.orm import joinedload
 
 from nova.db.sqlalchemy import api as db_api
@@ -203,6 +204,22 @@ class InventoryList(base.ObjectListBase, base.NovaObject):
         'objects': fields.ListOfObjectsField('Inventory'),
     }
 
+    def find(self, res_class):
+        """Return the inventory record from the list of Inventory records that
+        matches the supplied resource class, or None.
+
+        :param res_class: An integer or string representing a resource
+                          class. If the value is a string, the method first
+                          looks up the resource class identifier from the
+                          string.
+        """
+        if isinstance(res_class, six.string_types):
+            res_class = fields.ResourceClass.index(res_class)
+
+        for inv_rec in self.objects:
+            if fields.ResourceClass.index(inv_rec.resource_class) == res_class:
+                return inv_rec
+
     @staticmethod
     @db_api.api_context_manager.reader
     def _get_all_by_resource_provider(context, rp_uuid):

nova/tests/unit/objects/test_resource_provider.py

@@ -14,6 +14,7 @@ import mock
 
 from nova import exception
 from nova import objects
+from nova.objects import fields
 from nova.tests.unit.objects import test_objects
 from nova.tests import uuidsentinel as uuids
 
@@ -279,3 +280,33 @@ class TestInventory(test_objects._LocalTest):
         inventory_dict.pop('id')
         inventory = objects.Inventory(self.context, **inventory_dict)
         self.assertRaises(exception.ObjectActionError, inventory.save)
+
+    def test_find(self):
+        rp = objects.ResourceProvider(uuid=uuids.rp_uuid)
+        inv_list = objects.InventoryList(objects=[
+                objects.Inventory(
+                    resource_provider=rp,
+                    resource_class=fields.ResourceClass.VCPU,
+                    total=24),
+                objects.Inventory(
+                    resource_provider=rp,
+                    resource_class=fields.ResourceClass.MEMORY_MB,
+                    total=10240),
+        ])
+
+        found = inv_list.find(fields.ResourceClass.MEMORY_MB)
+        self.assertIsNotNone(found)
+        self.assertEqual(10240, found.total)
+
+        found = inv_list.find(fields.ResourceClass.VCPU)
+        self.assertIsNotNone(found)
+        self.assertEqual(24, found.total)
+
+        found = inv_list.find(fields.ResourceClass.DISK_GB)
+        self.assertIsNone(found)
+
+        # Try an integer resource class identifier...
+        found = inv_list.find(fields.ResourceClass.index(
+            fields.ResourceClass.VCPU))
+        self.assertIsNotNone(found)
+        self.assertEqual(24, found.total)