vm: make Instance.migrate(to_node) optional

circle/vm/models/instance.py

@@ -1068,10 +1068,15 @@ class Instance(AclBase, VirtualMachineDescModel, TimeStampedModel):
         return local_tasks.migrate.apply_async(args=[self, to_node, user],
                                                queue="localhost.man")
 
-    def migrate(self, to_node, user=None, task_uuid=None, timeout=120):
+    def migrate(self, to_node=None, user=None, task_uuid=None, timeout=120):
         """Live migrate running vm to another node. """
         with instance_activity(code_suffix='migrate', instance=self,
                                task_uuid=task_uuid, user=user) as act:
+            if not to_node:
+                with act.sub_activity('scheduling') as sa:
+                    to_node = self.select_node()
+                    sa.result = to_node
+
             # Destroy networks
             with act.sub_activity('destroying_net'):
                 for net in self.interface_set.all():

circle/vm/tests/test_models.py

 from django.test import TestCase
-from mock import Mock
+from mock import Mock, MagicMock, patch, call
 
 from ..models.common import (
     Lease
@@ -10,6 +10,7 @@ from ..models.instance import (
 from ..models.network import (
     Interface
 )
+from ..models.node import Node
 
 
 class PortFinderTestCase(TestCase):
@@ -39,6 +40,33 @@ class InstanceTestCase(TestCase):
         inst = Mock(state='RUNNING')
         assert Instance.is_running.getter(inst)
 
+    def test_migrate_with_scheduling(self):
+        inst = MagicMock(spec=Instance)
+        inst.interface_set.all.return_value = []
+        inst.node = MagicMock(spec=Node)
+        with patch('vm.models.instance.instance_activity') as ia, \
+                patch('vm.models.instance.vm_tasks.migrate') as migr:
+            Instance.migrate(inst)
+
+            migr.apply_async.assert_called()
+            self.assertIn(call().__enter__().sub_activity(u'scheduling'),
+                          ia.mock_calls)
+            inst.select_node.assert_called()
+
+    def test_migrate_wo_scheduling(self):
+        inst = MagicMock(spec=Instance)
+        inst.interface_set.all.return_value = []
+        inst.node = MagicMock(spec=Node)
+        with patch('vm.models.instance.instance_activity') as ia, \
+                patch('vm.models.instance.vm_tasks.migrate') as migr:
+            inst.select_node.side_effect = AssertionError
+
+            Instance.migrate(inst, inst.node)
+
+            migr.apply_async.assert_called()
+            self.assertNotIn(call().__enter__().sub_activity(u'scheduling'),
+                             ia.mock_calls)
+
 
 class InterfaceTestCase(TestCase):