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

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")
@@ -572,6 +574,21 @@ In such case enabling this option will reduce contention and chances for
 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",

nova/objects/fields.py

@@ -22,6 +22,7 @@ import six
 from nova import exception
 from nova.i18n import _
 from nova.network import model as network_model
+from nova.virt import arch
 
 
 # Import field errors from oslo.versionedobjects
@@ -103,56 +104,48 @@ class Architecture(BaseNovaEnum):
     ever adding new ones then ensure it matches libvirt's expectation.
     """
 
-    ALPHA = 'alpha'
-    ARMV6 = 'armv6'
-    ARMV7 = 'armv7l'
-    ARMV7B = 'armv7b'
+    ALPHA = arch.ALPHA
+    ARMV6 = arch.ARMV6
+    ARMV7 = arch.ARMV7
+    ARMV7B = arch.ARMV7B
 
-    AARCH64 = 'aarch64'
-    CRIS = 'cris'
-    I686 = 'i686'
-    IA64 = 'ia64'
-    LM32 = 'lm32'
+    AARCH64 = arch.AARCH64
+    CRIS = arch.CRIS
+    I686 = arch.I686
+    IA64 = arch.IA64
+    LM32 = arch.LM32
 
-    M68K = 'm68k'
-    MICROBLAZE = 'microblaze'
-    MICROBLAZEEL = 'microblazeel'
-    MIPS = 'mips'
-    MIPSEL = 'mipsel'
+    M68K = arch.M68K
+    MICROBLAZE = arch.MICROBLAZE
+    MICROBLAZEEL = arch.MICROBLAZEEL
+    MIPS = arch.MIPS
+    MIPSEL = arch.MIPSEL
 
-    MIPS64 = 'mips64'
-    MIPS64EL = 'mips64el'
-    OPENRISC = 'openrisc'
-    PARISC = 'parisc'
-    PARISC64 = 'parisc64'
+    MIPS64 = arch.MIPS64
+    MIPS64EL = arch.MIPS64EL
+    OPENRISC = arch.OPENRISC
+    PARISC = arch.PARISC
+    PARISC64 = arch.PARISC64
 
-    PPC = 'ppc'
-    PPCLE = 'ppcle'
-    PPC64 = 'ppc64'
-    PPC64LE = 'ppc64le'
-    PPCEMB = 'ppcemb'
+    PPC = arch.PPC
+    PPCLE = arch.PPCLE
+    PPC64 = arch.PPC64
+    PPC64LE = arch.PPC64LE
+    PPCEMB = arch.PPCEMB
 
-    S390 = 's390'
-    S390X = 's390x'
-    SH4 = 'sh4'
-    SH4EB = 'sh4eb'
-    SPARC = 'sparc'
+    S390 = arch.S390
+    S390X = arch.S390X
+    SH4 = arch.SH4
+    SH4EB = arch.SH4EB
+    SPARC = arch.SPARC
 
-    SPARC64 = 'sparc64'
-    UNICORE32 = 'unicore32'
-    X86_64 = 'x86_64'
-    XTENSA = 'xtensa'
-    XTENSAEB = 'xtensaeb'
+    SPARC64 = arch.SPARC64
+    UNICORE32 = arch.UNICORE32
+    X86_64 = arch.X86_64
+    XTENSA = arch.XTENSA
+    XTENSAEB = arch.XTENSAEB
 
-    ALL = (
-        ALPHA, ARMV6, ARMV7, ARMV7B,
-        AARCH64, CRIS, I686, IA64, LM32,
-        M68K, MICROBLAZE, MICROBLAZEEL, MIPS, MIPSEL,
-        MIPS64, MIPS64EL, OPENRISC, PARISC, PARISC64,
-        PPC, PPCLE, PPC64, PPC64LE, PPCEMB,
-        S390, S390X, SH4, SH4EB, SPARC,
-        SPARC64, UNICORE32, X86_64, XTENSA, XTENSAEB,
-    )
+    ALL = arch.ALL
 
     @classmethod
     def from_host(cls):

nova/scheduler/filters/image_props_filter.py

@@ -19,12 +19,15 @@ from distutils import versionpredicate
 from oslo_log import log as logging
 from oslo_utils import versionutils
 
+import nova.conf
 from nova.objects import fields
 from nova.scheduler import filters
 
 
 LOG = logging.getLogger(__name__)
 
+CONF = nova.conf.CONF
+
 
 class ImagePropertiesFilter(filters.BaseHostFilter):
     """Filter compute nodes that satisfy instance image properties.
@@ -41,9 +44,14 @@ class ImagePropertiesFilter(filters.BaseHostFilter):
     # a request
     run_filter_once_per_request = True
 
+    def _get_default_architecture(self):
+        return CONF.filter_scheduler.image_properties_default_architecture
+
     def _instance_supported(self, host_state, image_props,
                             hypervisor_version):
-        img_arch = image_props.get('hw_architecture')
+        default_img_arch = self._get_default_architecture()
+
+        img_arch = image_props.get('hw_architecture', default_img_arch)
         img_h_type = image_props.get('img_hv_type')
         img_vm_mode = image_props.get('hw_vm_mode')
         checked_img_props = (

nova/tests/unit/scheduler/filters/test_image_props_filters.py

@@ -43,6 +43,21 @@ class TestImagePropsFilter(test.NoDBTestCase):
         host = fakes.FakeHostState('host1', 'node1', capabilities)
         self.assertTrue(self.filt_cls.host_passes(host, spec_obj))
 
+    def test_image_properties_filter_uses_default_conf_value(self):
+        self.flags(image_properties_default_architecture='x86_64',
+                   group='filter_scheduler')
+        img_props = objects.ImageMeta(properties=objects.ImageMetaProps())
+        hypervisor_version = versionutils.convert_version_to_int('6.0.0')
+        spec_obj = objects.RequestSpec(image=img_props)
+        capabilities = {
+            'supported_instances': [(
+                obj_fields.Architecture.AARCH64,
+                obj_fields.HVType.KVM,
+                obj_fields.VMMode.HVM)],
+            'hypervisor_version': hypervisor_version}
+        host = fakes.FakeHostState('host1', 'node1', capabilities)
+        self.assertFalse(self.filt_cls.host_passes(host, spec_obj))
+
     def test_image_properties_filter_fails_different_inst_props(self):
         img_props = objects.ImageMeta(
             properties=objects.ImageMetaProps(

nova/virt/arch.py

@@ -0,0 +1,65 @@
+# Copyright 2018 VEXXHOST, Inc.
+# All Rights Reserved.
+#
+#    Licensed under the Apache License, Version 2.0 (the "License"); you may
+#    not use this file except in compliance with the License. You may obtain
+#    a copy of the License at
+#
+#         http://www.apache.org/licenses/LICENSE-2.0
+#
+#    Unless required by applicable law or agreed to in writing, software
+#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+#    License for the specific language governing permissions and limitations
+#    under the License.
+
+ALPHA = 'alpha'
+ARMV6 = 'armv6'
+ARMV7 = 'armv7l'
+ARMV7B = 'armv7b'
+
+AARCH64 = 'aarch64'
+CRIS = 'cris'
+I686 = 'i686'
+IA64 = 'ia64'
+LM32 = 'lm32'
+
+M68K = 'm68k'
+MICROBLAZE = 'microblaze'
+MICROBLAZEEL = 'microblazeel'
+MIPS = 'mips'
+MIPSEL = 'mipsel'
+
+MIPS64 = 'mips64'
+MIPS64EL = 'mips64el'
+OPENRISC = 'openrisc'
+PARISC = 'parisc'
+PARISC64 = 'parisc64'
+
+PPC = 'ppc'
+PPCLE = 'ppcle'
+PPC64 = 'ppc64'
+PPC64LE = 'ppc64le'
+PPCEMB = 'ppcemb'
+
+S390 = 's390'
+S390X = 's390x'
+SH4 = 'sh4'
+SH4EB = 'sh4eb'
+SPARC = 'sparc'
+
+SPARC64 = 'sparc64'
+UNICORE32 = 'unicore32'
+X86_64 = 'x86_64'
+XTENSA = 'xtensa'
+XTENSAEB = 'xtensaeb'
+
+ALL = (
+    ALPHA, ARMV6, ARMV7, ARMV7B,
+    AARCH64, CRIS, I686, IA64, LM32,
+    M68K, MICROBLAZE, MICROBLAZEEL, MIPS, MIPSEL,
+    MIPS64, MIPS64EL, OPENRISC, PARISC, PARISC64,
+    PPC, PPCLE, PPC64, PPC64LE, PPCEMB,
+    S390, S390X, SH4, SH4EB, SPARC,
+    SPARC64, UNICORE32, X86_64, XTENSA, XTENSAEB,
+)

releasenotes/notes/fix-multiarch-image-props-filter-f2e885aa53d585ea.yaml

@@ -0,0 +1,9 @@
+---
+fixes:
+  - The behaviour of ImagePropertiesFilter when using multiple architectures
+    in a cloud can be unpredictable for a user if they forget to set the
+    architecture property in their image.  Nova now allows the deployer to
+    specify a fallback in ``[filter_scheduler]image_properties_default_architecture``
+    to use a default architecture if none is specified.  Without this, it
+    is possible that a VM would get scheduled on a compute node that does not
+    support the image.