Open Stack

Hi.

Since that bdm v2 was introduced for Havana, it requires a caller to
specify bdm for an image together with imageRef to boot an instance in a
case of using bdm v2 to attach additional volumes.

{"server": {"imageRef": "xxx",
                       "block_device_mapping_v2": [
                           {"uuid": "xxx",
                            "source_type": "image",
                            "destination_type": "local",
                            "boot_index": 0,
                           },
                           <other_mappings>
                       ],
                       ...}}

If we specify imageRef or the bdm record only, the launch will be failed.

Novaclient does it [1] for shell invokes like
nova boot --image xxx --block_device <other mappings> ...
, but does nothing for client API calls.

Such feature of usage is unclear. I've not found any documentation for the
usage. Wiki [2] doesn't mention this feature, but refers to a deleted API
sample [3]. Before deleting [4] that sample didn't consider the feature, so
it was wrong.

As a result the need to specify an image in two arguments seems a temprary
workaround for some problems. And whole bdm v2 conception looks not well
designed, not finished.

The question is: is this feature correct? Shall we specify an image twice
for the long term? Otherwise which manner should be established finally: by
imageRef or by an bdm record?

ps. There are a review [5] and a linked bug [6] which require clarification
of this question.

[1]
https://github.com/openstack/python-novaclient/commit/6a85c954c53f868251413db51cc1d9616acd4d02#diff-4812fe2b8b37d18cf9498f9fbbab17beR125
[2]
https://wiki.openstack.org/wiki/BlockDeviceConfig#API_data_model_and_backwards_compat_issues
[3]
https://github.com/openstack/nova/tree/master/doc/api_samples/os-block-device-mapping-v2-boot
[4]
https://github.com/openstack/nova/blob/2f32996c3e5625245a4d0588ab32880d41400b9e/doc/api_samples/os-block-device-mapping-v2-boot/server-post-req.json
[5] https://review.openstack.org/#/c/171984/
[6] https://bugs.launchpad.net/nova/+bug/1441990
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