Comment 0 for bug 1587285

[Summary]
Unexpected volume-detach happen under a specific condition.

[Version]
Later than 13.0.0

[Steps to reproduce]

1. Attach "volume-A" to "VM-A" by volume-attach API.

e.g.
$ nova volume-attach <VM-A id> <volume-A id> /dev/vdb

2. Volume-attach API is failed in nova-api by unexpected reasons(e.g. terminating nova-api), and destroying block_device_mapping is failed too.
   "volume-A"'s status is still "available".

* If you want to reproduce, you should apply following code instead of terminating nova-api.
  (Terminating nova-api in good timing is so difficult.)
-------------------------------------------------------
--- a/nova/compute/api.py
+++ b/nova/compute/api.py
@@ -3108,10 +3108,12 @@ class API(base.Base):
         volume_bdm = self._create_volume_bdm(
             context, instance, device, volume_id, disk_bus=disk_bus,
             device_type=device_type)
+ raise Exception
         try:
             self._check_attach_and_reserve_volume(context, volume_id, instance)
             self.compute_rpcapi.attach_volume(context, instance, volume_bdm)
         except Exception:
+ raise Exception
             with excutils.save_and_reraise_exception():
                 volume_bdm.destroy()
-------------------------------------------------------

* Before do step-3, please remove the applied code and restart nova-api.

3. Attach "volume-A" to "VM-B" by volume-attach API.

e.g.
$ nova volume-attach <VM-B id> <volume-A id> /dev/vdb

4. Volume-attach API is completed.
   "volume-A"'s status is changed to "in-use" from "available".

5. Delete "VM-A".

e.g.
$ nova delete <VM-A id>

6. Deleting "VM-A" is completed.
   And "volume-A"'s status is changed to "available" from "in-use"!

I think "volume-A"'s status should not be changed by deleting "VM-A" at step-6 because "volume-A" was attached to "VM-B".