yahoo-eng-team team mailing list archive

[Paul Murray <pmurray@xxxxxx>]

Public bug reported:

Ironic nodes can only be assigned to a single instances. So resource
allocation is "all or nothing" - i.e. if an instance is spawned on a
node all the resources become unavailable no mater how much was stated
in the flavor used. The view of the resource tracker does not match this
behavior, leading to attempts to spawn instances that can not be
accommodated.

More specifically, when an instance is sent to a host manager to spawn,
the resource tracker for a target node will test to see if the node has
sufficient resources to accept the instance. This test checks to see if
the amount of resource available on the host (ram, disk, cpu, etc.) is
more than the amount requested. If the instance passes this test, the
resource tracker will deduct the amount of resource requested from the
amount that is available. This may leave a lesser amount still
available.

If there is a subsequent instance sent for that node, the resource
tracker will accept it if the amount of resource it requests is less
than the remaining amount available.

In ironic, spawning an instance will result in no resources left
available on that host. So the resource tracker has the wrong view of
how much resource is available at the node.

Note that the ironic driver is complemented by an ironic version of the
host manager at the scheduler that does do the right thing for ironic in
its consume method. However, its values are overridden by those
retrieved from the resource tracker, so it is overridden by the values
provided by the resource tracker.

Also, the get_available_resource() method on the ironic virt driver
returns the correct resource availability to the resource tracker, but
the resource tracker only uses the resource totals and recalculates the
availability, thus overriding the values from the driver as well.

Resource tracking can only work with ironic if the exact match filters
are used. In which case it works by coincidence. The resource tracker
resource consumption should be specialised to deal with ironic nodes
correctly.

** Affects: nova
     Importance: Undecided
         Status: New

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https://bugs.launchpad.net/bugs/1402658

Title:
  resource tracking is incorrect for ironic

Status in OpenStack Compute (Nova):
  New

Bug description:
  Ironic nodes can only be assigned to a single instances. So resource
  allocation is "all or nothing" - i.e. if an instance is spawned on a
  node all the resources become unavailable no mater how much was stated
  in the flavor used. The view of the resource tracker does not match
  this behavior, leading to attempts to spawn instances that can not be
  accommodated.

  More specifically, when an instance is sent to a host manager to
  spawn, the resource tracker for a target node will test to see if the
  node has sufficient resources to accept the instance. This test checks
  to see if the amount of resource available on the host (ram, disk,
  cpu, etc.) is more than the amount requested. If the instance passes
  this test, the resource tracker will deduct the amount of resource
  requested from the amount that is available. This may leave a lesser
  amount still available.

  If there is a subsequent instance sent for that node, the resource
  tracker will accept it if the amount of resource it requests is less
  than the remaining amount available.

  In ironic, spawning an instance will result in no resources left
  available on that host. So the resource tracker has the wrong view of
  how much resource is available at the node.

  Note that the ironic driver is complemented by an ironic version of
  the host manager at the scheduler that does do the right thing for
  ironic in its consume method. However, its values are overridden by
  those retrieved from the resource tracker, so it is overridden by the
  values provided by the resource tracker.

  Also, the get_available_resource() method on the ironic virt driver
  returns the correct resource availability to the resource tracker, but
  the resource tracker only uses the resource totals and recalculates
  the availability, thus overriding the values from the driver as well.

  Resource tracking can only work with ironic if the exact match filters
  are used. In which case it works by coincidence. The resource tracker
  resource consumption should be specialised to deal with ironic nodes
  correctly.

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