Filtering hosts by isolating aggregates¶
Background¶
I want to set up an aggregate ABC
with hosts that allow you to run only
certain licensed images. I could tag the aggregate with metadata such as
<LICENSED=WINDOWS>
. Then if I boot an instance with an image containing the
property <LICENSED=WINDOWS>
, it will land on one of the hosts in aggregate
ABC
. But if the user creates a new image which does not include
<LICENSED=WINDOWS>
metadata, an instance booted with that image could still
land on a host in aggregate ABC
as reported in launchpad bug 1677217.
The AggregateImagePropertiesIsolation scheduler filter passes even
though the aggregate metadata <LICENSED=WINDOWS>
is not present in the
image properties.
Solution¶
The above problem is addressed by blueprint placement-req-filter-forbidden-aggregates which was implemented in the 20.0.0 Train release.
The following example assumes you have configured aggregate ABC
and added
hosts HOST1
and HOST2
to it in Nova, and that you want to isolate those
hosts to run only instances requiring Windows licensing.
Set the
scheduler.enable_isolated_aggregate_filtering
config option totrue
in nova.conf and restart the nova-scheduler service.Add trait
CUSTOM_LICENSED_WINDOWS
to the resource providers forHOST1
andHOST2
in the Placement service.First create the
CUSTOM_LICENSED_WINDOWS
trait# openstack --os-placement-api-version 1.6 trait create CUSTOM_LICENSED_WINDOWS
Assume
<HOST1_UUID>
is the UUID ofHOST1
, which is the same as its resource provider UUID.Start to build the command line by first collecting existing traits for
HOST1
# traits=$(openstack --os-placement-api-version 1.6 resource provider trait list -f value <HOST1_UUID> | sed 's/^/--trait /')
Replace
HOST1
’s traits, addingCUSTOM_LICENSED_WINDOWS
# openstack --os-placement-api-version 1.6 resource provider trait set $traits --trait CUSTOM_LICENSED_WINDOWS <HOST1_UUID>
Repeat the above steps for
HOST2
.Add the
trait:CUSTOM_LICENSED_WINDOWS=required
metadata property to aggregateABC
.# openstack --os-compute-api-version 2.53 aggregate set --property trait:CUSTOM_LICENSED_WINDOWS=required ABC
As before, any instance spawned with a flavor or image containing
trait:CUSTOM_LICENSED_WINDOWS=required
will land on HOST1
or HOST2
because those hosts expose that trait.
However, now that the isolate_aggregates
request filter is configured,
any instance whose flavor or image does not contain
trait:CUSTOM_LICENSED_WINDOWS=required
will not land on HOST1
or
HOST2
because aggregate ABC
requires that trait.
The above example uses a CUSTOM_LICENSED_WINDOWS
trait, but you can use any
custom or standard trait in a similar fashion.
The filter supports the use of multiple traits across multiple aggregates. The combination of flavor and image metadata must require all of the traits configured on the aggregate in order to pass.