Dear friends, again need your assistance.

Summary: HEAT stack update fails when adding new block volume to 'block_device_mapping_v2' section in OS::Nova::Server resource.

I'm trying, using Heat, manipulate VM's block volume allocation, using the following template:

  centos_v7:
    type: OS::Glance::Image
    properties:
      [ ... ]
      location: http://cloud.centos.org/centos/7/images/CentOS-7-x86_64-GenericCloud.qcow2

  din3_volume:
    type: OS::Cinder::Volume
    properties:
      size: 30
      name: din3_boot
      image: { get_resource: centos_v7 }

# Aux volume, will be used later in the example
  din3_aux:
    type: OS::Cinder::Volume
    properties:
      size: 15
      name: din3_aux

  din3_init:
    type: OS::Heat::MultipartMime
    properties: [ ... ]

  din3:
    type: OS::Nova::Server
    properties:
      flavor: { get_param: flavor }
      block_device_mapping_v2:
        - delete_on_termination: true
          swap_size: 512
        - delete_on_termination: false
          boot_index: 0
          volume_id: { get_resource: din3_volume }
      networks:
         - port: { get_resource: din3-i2e }
      user_data_format: SOFTWARE_CONFIG
      user_data: { get_resource: din3_init }

There are other resources in the stack and creation of stack ends with success and both volumes are exist in the stack:

doka/doka@doka.ua:~/heat $ openstack volume list
| e15795cb-bea1-4a3b-b910-d39b18541ca3 | din3_boot | in-use | 32 | Attached to din3 on /dev/vda
| f709ab08-0f9d-4ae3-9645-7af7e1ea9659 | din3_aux  | available |   16 |

As soon as I add din3_aux to "block_device_mapping_v2" section, changing nothing more:

  din3:
    type: OS::Nova::Server
    properties:
      flavor: { get_param: flavor }
      block_device_mapping_v2:
        - delete_on_termination: true
          swap_size: 512
        - delete_on_termination: false
          boot_index: 0
          volume_id: { get_resource: din3_volume }
        - delete_on_termination: true
          boot_index: 1
          volume_id: { get_resource: din3_aux }
      networks:
        - port: { get_resource: din3-i2e }
      user_data_format: SOFTWARE_CONFIG
      user_data: { get_resource: din3_init }

update of stack fails with the following message:

stack_status          | UPDATE_FAILED
stack_status_reason   | Resource CREATE failed: BadRequest: resources.din3: Invalid volume:
                        volume 'e15795cb-bea1-4a3b-b910-d39b18541ca3' status must be 'available'.
                        Currently in 'in-use' (HTTP 400)
                        (Request-ID: req-203313ac-e81d-42f5-8a56-c17ad02eb14f)

Of course, din3_volume is in use since VM is running and din3_volume is bootable one. Questions are:

1) is it a bug or a feature? :-)

2) adding new volume is atomic operation and can be successfully done using Openstack CLI - why same operation in Heat results in reconfiguration of existing volumes? Are there ways to make them atomic in Heat as well?

Any recommendations on how to avoid reconfiguration of block volume on update which don't touch this block volume are highly welcome.

Thanks!