Prevent caller from specifying id during Service.create()

The patch is to remove id when it was set before creating a service
in objects, and check if the service exists before it is created.

Related to blueprint icehouse-objects.

Change-Id: I688bfc98234f4bc27fb15474e05c7f25753efaf7

nova/objects/service.py

@@ -107,7 +107,11 @@ class Service(base.NovaPersistentObject, base.NovaObject):
 
     @base.remotable
     def create(self, context):
+        if self.obj_attr_is_set('id'):
+            raise exception.ObjectActionError(action='create',
+                                              reason='already created')
         updates = self.obj_get_changes()
+        updates.pop('id', None)
         db_service = db.service_create(context, updates)
         self._from_db_object(context, self, db_service)
 

nova/tests/objects/test_service.py

@@ -85,6 +85,17 @@ class _TestServiceObject(object):
         service_obj.create(self.context)
         self.assertEqual(fake_service['id'], service_obj.id)
 
+    def test_recreate_fails(self):
+        self.mox.StubOutWithMock(db, 'service_create')
+        db.service_create(self.context, {'host': 'fake-host'}).AndReturn(
+            fake_service)
+        self.mox.ReplayAll()
+        service_obj = service.Service()
+        service_obj.host = 'fake-host'
+        service_obj.create(self.context)
+        self.assertRaises(exception.ObjectActionError, service_obj.create,
+                          self.context)
+
     def test_save(self):
         self.mox.StubOutWithMock(db, 'service_update')
         db.service_update(self.context, 123, {'host': 'fake-host'}).AndReturn(