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[Thierry Carrez <thierry.carrez+lp@xxxxxxxxx>]

** Changed in: nova
       Status: Fix Committed => Fix Released

** Changed in: nova
    Milestone: None => juno-1

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https://bugs.launchpad.net/bugs/1309154

Title:
  Detach Volume Ordering Has Bad User Experience

Status in OpenStack Compute (Nova):
  Fix Released

Bug description:
  Currently when detaching a volume we do:

  1. driver.detach() -> detaches the volume in the hypervisor
  2. cinder.detach() -> marks the volume detached in cinder
  3. bdm.delete() -> stops the nova side from reporting an attached volume.

  This leads to bad UX for two reasons:

  a. If the cinder detach fails, the bdm still exists so nova reports a volume attached even when the hypervisor
      has detached it.
  b. There is a window where cinder reports the volume available but nova still thinks the attachment exists

  I propose we reverse the order of 2. and 3.

  This reverses a. so that a detach fail will show the volume as attached in cinder but nova will not show it. The nova side more accurately reflects what nova knows about.
  This reverses b. so that there is a window where nova has removed the attachment but cinder still reports it in use. This is a fairly minor difference, but leads to a nicer experience when you are detaching and re-attaching the same volume because it can be reattached once it becomes available.

  This also may help with https://bugs.launchpad.net/nova/+bug/1172695

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