Added ability to configure default architecture for ImagePropertiesFilter

When using ImagePropertiesFilter with multiple architectures inside the
same deployment, it is possible that images can be uploaded without the
hw_architecture property defined.

This results in behaviour where the instance could be scheduled on any
type of hypervisor, resulting in an instance that will successfully
transition to ACTIVE but never properly run because of the difference
in architecture.

This makes the ImagePropertiesFilter problematic as most images are
generally uploaded without the architecture property set because
most documentation does not encourage doing that.

The addition of this flag allows to make using the filter possible
because it allows the deployer to assume a default architecture if
the user did not supply one (assuming it would be the most common
architecture in their deployment, such as x86_64) yet if the user
wants a more specific architecture, they can do it in their image
properties.

In order to avoid a circular import loop, the references to the
architecture field have been moved to a seperate module so that
they can be properly and cleaned imported inside configuration.

Change-Id: Ib52deb095028e93619b93ef9e5f70775df2a403a
Closes-Bug: #1769283
(cherry picked from commit aa5b1326c86c408ce9cc4546e1c7a310fbce3136)

1 files changed, 17 insertions, 0 deletions

diff --git a/nova/conf/scheduler.py b/nova/conf/scheduler.py
index 2cb66e1aa3..84eb790566 100644
--- a/nova/conf/scheduler.py
+++ b/nova/conf/scheduler.py
@@ -15,6 +15,8 @@
 
 from oslo_config import cfg
 
+from nova.virt import arch
+
 
 scheduler_group = cfg.OptGroup(name="scheduler",
                                title="Scheduler configuration")
@@ -516,6 +518,21 @@ rescheduling events.
 At the same time it will make the instance packing (even in unweighed case)
 less dense.
 """),
+    cfg.StrOpt(
+        "image_properties_default_architecture",
+        choices=arch.ALL,
+        help="""
+The default architecture to be used when using the image properties filter.
+
+When using the ImagePropertiesFilter, it is possible that you want to define
+a default architecture to make the user experience easier and avoid having
+something like x86_64 images landing on aarch64 compute nodes because the
+user did not specify the 'hw_architecture' property in Glance.
+
+Possible values:
+
+* CPU Architectures such as x86_64, aarch64, s390x.
+"""),
     # TODO(mikal): replace this option with something involving host aggregates
     cfg.ListOpt("isolated_images",
         default=[],