Add support attach cinder volume to scale cluster

Partially implement blueprint attach-cinder-volume-scaling-support

Change-Id: I54d23195c208ccd808d83c1d44a45014df5d3bae

savanna/service/instances.py

@@ -62,6 +62,7 @@ def scale_cluster(cluster, node_group_names_map):
         instances_list = _scale_cluster_instances(
             cluster, node_groups_map)
         _await_instances(cluster)
+        volumes.attach_to_instances(instances_list)
     except Exception as ex:
         LOG.warn("Can't scale cluster: %s", ex)
         with excutils.save_and_reraise_exception():
@@ -261,7 +262,12 @@ def _rollback_cluster_creation(cluster, ex):
 
 
 def _rollback_cluster_scaling(instances):
-    # if some nodes are up we should shut them down and update "count" in
+    try:
+        volumes.detach_from_instances(instances)
+    except Exception:
+        raise
+    finally:
+        #if some nodes are up we should shut them down and update "count" in
         # node_group
         ng_to_delete = []
         for i in instances:

savanna/service/volumes.py

@@ -30,6 +30,11 @@ def attach(cluster):
             _attach_volumes_to_node(node_group, instance)
 
 
+def attach_to_instances(instances):
+    for instance in instances:
+        _attach_volumes_to_node(instance.node_group, instance)
+
+
 def _await_attach_volume(instance, device_path):
     timeout = 10
     for _ in six.moves.xrange(timeout):
@@ -124,6 +129,15 @@ def _mount_volume(instance, device_path, mount_point):
 def detach(cluster):
     for node_group in cluster.node_groups:
         for instance in node_group.instances:
+            _detach_volume_from_instance(instance)
+
+
+def detach_from_instances(instances):
+    for instance in instances:
+        _detach_volume_from_instance(instance)
+
+
+def _detach_volume_from_instance(instance):
     for volume_id in instance.volumes:
         volume = cinder.get_volume(volume_id)
         try: