QEMU built-in iscsi initiator support should be version-constrained in the driver

[Matt Riedemann]

This spec was approved in kilo:

http://specs.openstack.org/openstack/nova-specs/specs/kilo/implemented/qemu-built-in-iscsi-initiator.html

With the code change here:

https://review.openstack.org/#/c/135854/

The spec and code change says:

"QEMU binary of Ubuntu 14.04 doesn’t have iSCSI support. Users have to install libiscsi2 package and libiscsi-dev from Debian and rebuild QEMU binary with libiscsi support by themselves."

This is a pretty terrible way of determining if this can be supported. It also basically says if you're not using ubuntu/debian you're on your own for figuring out what version of qemu (and what version your distro supports) is required to make this work.

This should have really had a version constraint in the driver code such that if the version of qemu is not new enough we can't support the volume backend.

[Matt Riedemann (mriedem)]

See related ubuntu bug:

https://bugs.launchpad.net/ubuntu/+source/qemu/+bug/1271573

[Sean Dague (sdague)]

Automatically discovered version kilo in description. If this is incorrect, please update the description to include 'nova version: ...'

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.opendev.org/668750

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.opendev.org/668750
Committed: https://git.openstack.org/cgit/openstack/nova/commit/?id=b8c55d1d3c3b9dfd3b962e092e4fd80f2b0dfac3
Submitter: Zuul
Branch: master

commit b8c55d1d3c3b9dfd3b962e092e4fd80f2b0dfac3
Author: Lee Yarwood <email address hidden>
Date: Tue Jul 2 20:14:21 2019 +0100

    libvirt: Remove unreachable native QEMU iSCSI initiator config code

    Ieb9a03d308495be4e8c54b5c6c0ff781ea7f0559 introduced support for using
    QEMU's native iSCSI initiator support way back in Kilo. However this was
    only enabled when the LibvirtNetVolumeDriver class was configured as the
    ``iscsi`` volume driver via the ``[libvirt]/volume_drivers`` configurable.

    Unfortunately this configurable was removed in Liberty by
    I832820499ec3304132379ad9b9d1ee92c5a75b61 essentially rendering this
    ``iscsi`` based code path dead ever since unless operators manually
    hacked the now static ``libvirt_volume_drivers`` list within driver.py.

    As a result of this and a complete lack of any test coverage in the gate
    we can now remove this unreachable code from Nova. It might be desirable
    to reintroduce this support later but this should take the form of an
    extracted volume driver and a new configurable within nova.conf to
    switch between the two available drivers.

    Closes-Bug: #1501447
    Change-Id: I1043287fe8063c4b2af07c997a931a7097518ca9

[OpenStack Infra (hudson-openstack)]

This issue was fixed in the openstack/nova 20.0.0.0rc1 release candidate.