[Bug 1900775] Re: Cinder fails to create image-based volume if mirroring is enabled

[Corey Bryant]

** Also affects: cinder (Ubuntu)
   Importance: Undecided
       Status: New

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https://bugs.launchpad.net/bugs/1900775

Title:
  Cinder fails to create image-based volume if mirroring is enabled

Status in charm-ceph-rbd-mirror:
  Invalid
Status in Cinder:
  New
Status in cinder package in Ubuntu:
  New

Bug description:
  OpenStack Train, Ceph Nautilus, ceph-rbd-mirror is deployed in dual-way.
  Cinder has Ceph as backend for volumes.

  Creating a volume from qcow2 image.
  Current flow is the following:
  1. Cinder creates empty volume in Ceph
  2. Cinder downloads the image
  3. Image is converted to raw
  4. Volume is deleted https://github.com/openstack/cinder/blob/master/cinder/volume/drivers/rbd.py#L1611
  5. Cinder performs "rbd import" using unpacked raw image as source.

  Apparently rbd-mirror daemon creates a snapshot upon the image creation in Ceph (seems for mirroring purposes) which for empty image lasts for about a second.
  It happens that step4 may be performed (very often) during the period of time when the snapshot exists, and it fails with "Cannot delete the volume with snapshots" error.
  The only way to fix this behaviour - disable mirroring of the backend pool which is not desired.

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