Add ability to find an available floating ip

Add method to find the first available floating IP address.

Change-Id: I7b1ff09e0df69f43ddbf20c1b49e26ae649f6cd3

openstack/network/v2/floatingip.py

@@ -10,6 +10,7 @@
 # License for the specific language governing permissions and limitations
 # under the License.
 
+from openstack import exceptions
 from openstack.network import network_service
 from openstack import resource
 
@@ -37,3 +38,14 @@ class FloatingIP(resource.Resource):
     port_id = resource.prop('port_id')
     project_id = resource.prop('tenant_id')
     router_id = resource.prop('router_id')
+
+    @classmethod
+    def find_available(cls, session):
+        args = {
+            'port_id': '',
+            'fields': cls.id_attribute,
+        }
+        info = cls.list(session, **args)
+        if len(info) > 0:
+            return info[0]
+        raise exceptions.ResourceNotFound("No available floating ips exist.")

openstack/tests/network/v2/test_floatingip.py

@@ -10,8 +10,10 @@
 # License for the specific language governing permissions and limitations
 # under the License.
 
+import mock
 import testtools
 
+from openstack import exceptions
 from openstack.network.v2 import floatingip
 
 IDENTIFIER = '10.0.0.1'
@@ -50,3 +52,31 @@ class TestFloatingIP(testtools.TestCase):
         self.assertEqual(EXAMPLE['port_id'], sot.port_id)
         self.assertEqual(EXAMPLE['tenant_id'], sot.project_id)
         self.assertEqual(EXAMPLE['router_id'], sot.router_id)
+
+    def test_find_available(self):
+        mock_session = mock.Mock()
+        mock_get = mock.Mock()
+        mock_session.get = mock_get
+        data = {'floating_ip_address': '10.0.0.1'}
+        fake_response = mock.Mock()
+        fake_response.body = {floatingip.FloatingIP.resources_key: [data]}
+        mock_get.return_value = fake_response
+
+        result = floatingip.FloatingIP.find_available(mock_session)
+
+        self.assertEqual('10.0.0.1', result.id)
+        p = {'fields': 'floating_ip_address', 'port_id': ''}
+        mock_get.assert_called_with(floatingip.FloatingIP.base_path,
+                                    params=p,
+                                    service=floatingip.FloatingIP.service)
+
+    def test_find_available_nada(self):
+        mock_session = mock.Mock()
+        mock_get = mock.Mock()
+        mock_session.get = mock_get
+        fake_response = mock.Mock()
+        fake_response.body = {floatingip.FloatingIP.resources_key: []}
+        mock_get.return_value = fake_response
+
+        self.assertRaises(exceptions.ResourceNotFound,
+                          floatingip.FloatingIP.find_available, mock_session)