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[Matt Riedemann <mriedem.os@xxxxxxxxx>]

Public bug reported:

We do a pretty good job of testing that notifications are sent during
certain operations, like live migration, but not so great a job at
making sure that notifications are sent at expected times, like that
start and end notifications actually happen at the start and end of a
method (seems we should really use a decorator function for something
like this for future proofing...).

This is a follow on from bug 1762876 where I thought about relying on
the "live_migration._post.end" notification to be able to tell when a
migration record should be 'completed' but that notification is sent
*before* we change the status on the migration record:

https://github.com/openstack/nova/blob/fe976dcc559d059589a9ccf953a28e855abf50fb/nova/compute/manager.py#L6323

If you look at the beginning of the same method, the start notification
is sent well after we've already started doing some work:

https://github.com/openstack/nova/blob/fe976dcc559d059589a9ccf953a28e855abf50fb/nova/compute/manager.py#L6261

So this bug is primarily meant to be an audit of at least the live
migration flows where the methods are big and hairy so it's easy to see
how over the years, the notifications got pushed into weird spots in
those methods, and should be moved back to the appropriate start/end
locations (or write a decorator to handle this).

** Affects: nova
     Importance: Medium
         Status: Triaged


** Tags: live-migration notifications

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https://bugs.launchpad.net/bugs/1763051

Title:
  Need to audit when notifications are sent during live migration

Status in OpenStack Compute (nova):
  Triaged

Bug description:
  We do a pretty good job of testing that notifications are sent during
  certain operations, like live migration, but not so great a job at
  making sure that notifications are sent at expected times, like that
  start and end notifications actually happen at the start and end of a
  method (seems we should really use a decorator function for something
  like this for future proofing...).

  This is a follow on from bug 1762876 where I thought about relying on
  the "live_migration._post.end" notification to be able to tell when a
  migration record should be 'completed' but that notification is sent
  *before* we change the status on the migration record:

  https://github.com/openstack/nova/blob/fe976dcc559d059589a9ccf953a28e855abf50fb/nova/compute/manager.py#L6323

  If you look at the beginning of the same method, the start
  notification is sent well after we've already started doing some work:

  https://github.com/openstack/nova/blob/fe976dcc559d059589a9ccf953a28e855abf50fb/nova/compute/manager.py#L6261

  So this bug is primarily meant to be an audit of at least the live
  migration flows where the methods are big and hairy so it's easy to
  see how over the years, the notifications got pushed into weird spots
  in those methods, and should be moved back to the appropriate
  start/end locations (or write a decorator to handle this).

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