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[Richard Jones <r1chardj0n3s@xxxxxxxxx>]

Public bug reported:

The SQL underlying the os-simple-tenant-usage API call results in very
slow operations when the database has many (20,000+) instances. In
testing, the objects.InstanceList.get_active_by_window_joined call in
nova/api/openstack/compute/contrib/simple_tenant_usage.py:SimpleTenantUsageController._tenant_usages_for_period
takes 24 seconds to run.

Some basic timing analysis has shown that the initial query in
nova/db/sqlalchemy/api.py:instance_get_active_by_window_joined runs in
*reasonable* time (though still 5-6 seconds) and the bulk of the time is
spent in the subsequent _instances_fill_metadata call which pulls in
system_metadata info by using a SELECT with an IN clause containing the
20,000 uuids listed, resulting in execution times over 15 seconds.

** Affects: nova
     Importance: Undecided
         Status: Confirmed

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https://bugs.launchpad.net/bugs/1421471

Title:
  os-simple-tenant-usage performs poorly with many instances

Status in OpenStack Compute (Nova):
  Confirmed

Bug description:
  The SQL underlying the os-simple-tenant-usage API call results in very
  slow operations when the database has many (20,000+) instances. In
  testing, the objects.InstanceList.get_active_by_window_joined call in
  nova/api/openstack/compute/contrib/simple_tenant_usage.py:SimpleTenantUsageController._tenant_usages_for_period
  takes 24 seconds to run.

  Some basic timing analysis has shown that the initial query in
  nova/db/sqlalchemy/api.py:instance_get_active_by_window_joined runs in
  *reasonable* time (though still 5-6 seconds) and the bulk of the time
  is spent in the subsequent _instances_fill_metadata call which pulls
  in system_metadata info by using a SELECT with an IN clause containing
  the 20,000 uuids listed, resulting in execution times over 15 seconds.

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