[Bug 1825882] Re: Virsh disk attach errors silently ignored

[Jorge Niedbalski]

** Also affects: nova (Ubuntu Disco)
   Importance: Undecided
       Status: New

** Also affects: nova (Ubuntu Bionic)
   Importance: Undecided
       Status: New

** Also affects: nova (Ubuntu Cosmic)
   Importance: Undecided
       Status: New

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https://bugs.launchpad.net/bugs/1825882

Title:
  Virsh disk attach errors silently ignored

Status in OpenStack Compute (nova):
  Fix Released
Status in OpenStack Compute (nova) queens series:
  Fix Committed
Status in OpenStack Compute (nova) rocky series:
  Fix Committed
Status in OpenStack Compute (nova) stein series:
  Fix Committed
Status in nova package in Ubuntu:
  New
Status in nova source package in Bionic:
  New
Status in nova source package in Cosmic:
  New
Status in nova source package in Disco:
  New

Bug description:
  Description
  ===========
  The following commit (1) is causing volume attachments which fail due to libvirt device attach erros to be silently ignored and Nova report the attachment as successful.

  It seems that the original intention of the commit was to log a
  condition and re-raise the exeption, but if the exception is of type
  libvirt.libvirtError and does not contain the searched pattern, the
  exception is ignored. If you unindent the raise statement, errors are
  reported again.

  In our case we had ceph/apparmor configuration problems in compute
  nodes which prevented virsh attaching the device; volumes appeared as
  successfully attached but the corresponding block device missing in
  guests VMs. Other libvirt attach error conditions are ignored also, as
  when you have already occuppied device names (i.e. 'Target vdb already
  exists', device is busy, etc.)

  (1)
  https://github.com/openstack/nova/commit/78891c2305bff6e16706339a9c5eca99a84e409c

  Steps to reproduce
  ==================
  This is somewhat hacky, but is a quick way to provoke a virsh attach error:
  - virsh detach-disk <domain> vdb
  - update nova & cinder DB as if volume is detached
  - re-attach volume
  - volume is marked as attached, but VM block device is missing

  Expected result
  ===============
  - Error 'libvirtError: Requested operation is not valid: target vdb already exists' should be raised, and volume not attached

  Actual result
  =============
  - Attach successful but virsh block device not created

  Environment
  ===========
  - Openstack version Queens

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