block_device mapping identifies ephemeral disks incorrectly

[Vish Ishaya]

Ephemeral drives are destinaton == local, but the new bdm code bases it on source instead. This leads to improper errors:

$ nova boot --flavor m1.tiny --block-device source=blank,dest=volume,bus=virtio,size=1,bootindex=0 test
ERROR (BadRequest): Ephemeral disks requested are larger than the instance type allows. (HTTP 400) (Request-ID: req-53247c8e-d14e-43e2-b01e-85b49f520e61)

The code is here:

https://github.com/openstack/nova/blob/106fb458c7ac3cc17bb42d1b83ec3f4fa8284e71/nova/block_device.py#L411

This should be checking destination_type == 'local' instead of source type.

[Vish Ishaya (vishvananda)]

Assigned to nikolain case there is some reason that it has been coded this way.

[Nikola Đipanov (ndipanov)]

yeah, this is a bug. The only reason the code is written in that way is because the author was trying to be clever :).

Also (based on your example), currently source=blank, destination=volume will not work. We should either make it create an empty volume and attach it, or disallow it in the API.

I'm going to report a different bug for this so we can track it as well.

[Thang Pham (thang-pham)]

Not sure why the patch is not showing up here, but this patch should fix it: https://review.openstack.org/#/c/109834/

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/109834
Committed: https://git.openstack.org/cgit/openstack/nova/commit/?id=9d64a827b9c2c5f332b3e57f6cb818d3f4735d23
Submitter: Jenkins
Branch: master

commit 9d64a827b9c2c5f332b3e57f6cb818d3f4735d23
Author: Thang Pham <email address hidden>
Date: Wed Jul 23 17:15:52 2014 -0400

    Allow empty volumes to be created

    The following patch allows an empty volume to be created and
    attached to an instance at boot time. Today, you can define a
    bootable volume that is sourced from an image, volume, or
    snapshot. However, you cannot define a volume that is sourced
    from 'blank', even though it is one of the source options
    available. For example, the following command will not work:
    nova boot --flavor m1.tiny
    --block-device source=blank,dest=volume,size=1,bootindex=0 test.
    This is because the method used to identify ephemeral volumes
    (new_format_is_ephemeral) believes any block device with
    source_type=blank is an ephemeral, and there is no logic to
    handle volumes where source_type=blank. The following patch
    fixes these bugs by properly identifying ephemeral block
    devices and creating blank/empty volumes when source_type=blank
    and destination_type=volume.

    Change-Id: I5aa9684bfad1749fadff3018b13a225ed8f16fe8
    Closes-Bug: #1347028
    Closes-Bug: #1347499