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[sean mooney <1915055@xxxxxxxxxxxxxxxxxx>]

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

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https://bugs.launchpad.net/bugs/1915055

Title:
  launched_at's reset when resizing/reverting and unshelving impacts
  "openstack usage show"

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

Bug description:
  environment: devstack-master stacked Jan 28th 2021

  The "openstack usage show" commands provide metrics related to run time of the instance, as seen below:
  +---------------+----------+
  | Field         | Value    |
  +---------------+----------+
  | CPU Hours     | 260.68   |
  | Disk GB-Hours | 260.68   |
  | RAM MB-Hours  | 66733.63 |
  | Servers       | 3        |
  +---------------+----------+

  The logic in [0] determines how those values are calculated. They are
  based on the launched_at and terminated_at fields.

  Some operations, such as resize and unshelve, reset the launched_at
  field. Therefore, for a given instance, the run time information is
  wiped, as if it had never run before.

  Steps to reproduce:
  1. Create an instance.
  2. Wait a few minutes, start monitoring usage with "watch openstack usage show --project admin" on a separate tab.
  3. Either shelve and unshelve an instance, or resize the instance and revert the resize.
  4. Notice how the "openstack usage show" statistics suddenly drops to a lower value and then continues to increase.

  Expected result:
  Statistics would not drop, should continue measuring.

  Some possible solutions:
  1. Stop resetting the launched_at field
  2. Change the field used for calculation at [0] to something else (maybe created_at?)

  [0]
  https://github.com/openstack/nova/blob/6c0ceda3659405149b7c0b5c283275ef0a896269/nova/api/openstack/compute/simple_tenant_usage.py#L74

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