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[Matt Riedemann <mriedem.os@xxxxxxxxx>]

There could be any number of reasons really why the instance can't do
multiattach. I don't think exposing the underlying versions of the
libvirt/qemu packages on the system is worthwhile, nor does it help the
user. To the user, it just means, you can't do this thing.

If the operator is getting flooded with issues about failed multiattach
attempts because their computes aren't setup to handle it yet, they
should disable the ability to do multiattach in cinder, via policy, or
setup host aggregates and special flavors for the ones that can.

I'm going to mark this as invalid as I don't think it's something we
need to fix.

** Changed in: nova
       Status: New => Won't Fix

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https://bugs.launchpad.net/bugs/1746029

Title:
  Unclear libvirt error message when attaching multiattach volume

Status in OpenStack Compute (nova):
  Won't Fix

Bug description:
  There is a known problem using certain versions of qemu and libvirt
  with multiattach. Nova will not let you attach a multiattach enabled
  volume if the version of libvirt is <= 3.10 or qemu >= 2.10. This bug
  is only about the user error message that is displayed when you hit
  this error.

  Ubuntu 16.04:

  $ virsh --version
  3.6.0

  $ kvm --version
  QEMU emulator version 2.10.1(Debian 1:2.10+dfsg-0ubuntu3.1~cloud0)

  $ nova volume-attach vm1 a7de1d48-fe81-402b-a8ed-656e27ff0d08

  ERROR (Conflict): Volume a7de1d48-fe81-402b-a8ed-656e27ff0d08 has
  'multiattach' set, which is not supported for this instance. (HTTP
  409) (Request-ID: req-f34d2c90-559f-4646-903c-60661b082c85)

  This CLI message does not give the user any indication that there is a
  version issue with libvirt/qemu.

  The n-cpu log has a clearer debug message:

  ... DEBUG nova.virt.libvirt.driver ... Volume multiattach is not
  supported based on current versions of QEMU and libvirt. QEMU must be
  less than 2.10 or libvirt must be greater than or equal to 3.10.

  
  It would be better if the message returned by the cli command was more specific to the reason why the attach failed.

  nova$ git show
  commit 87ea686f9f2cc706205d188922bb14272625e7be
  Merge: dc63965 8ec0b43
  Author: Zuul <zuul@xxxxxxxxxxxxxxxxxxxx>
  Date:   Wed Jan 24 13:53:24 2018 +0000

      Merge "Transform instance.resize_confirm notification"

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