Add CPU arch filter scheduler support

In a mixed environment of running different CPU architecutres,
one would not want to run an ARM instance on a X86_64 host and
vice versa.

This scheduler filter option will prevent instances running
on a host that it is not intended for.

The libvirt driver queries the guest capabilities of the
host and stores the guest arches in the permitted_instances_types
list in the cpu_info dict of the host.

The Xen equivalent will be done later in another commit.

The arch filter will compare the instance arch against
the permitted_instances_types of a host
and filter out invalid hosts.

Also adds ARM as a valid arch to the filter.

The ArchFilter is not turned on by default.

Change-Id: I17bd103f00c25d6006a421252c9c8dcfd2d2c49b
Signed-off-by: Chuck Short <chuck.short@canonical.com>

5 files changed, 111 insertions, 1 deletions

diff --git a/nova/compute/api.py b/nova/compute/api.py
index 1e28f0190..a5277da15 100644
--- a/nova/compute/api.py
+++ b/nova/compute/api.py
@@ -322,7 +322,6 @@ class API(base.Base):
             return value
 
         options_from_image = {'os_type': prop('os_type'),
-                              'architecture': prop('arch'),
                               'vm_mode': prop('vm_mode')}
 
         # If instance doesn't have auto_disk_config overridden by request, use
diff --git a/nova/scheduler/filters/arch_filter.py b/nova/scheduler/filters/arch_filter.py
new file mode 100644
index 000000000..1f11d07b6
--- /dev/null
+++ b/nova/scheduler/filters/arch_filter.py
@@ -0,0 +1,44 @@
+# Copyright (c) 2011-2012 OpenStack, LLC
+# Copyright (c) 2012 Canonical Ltd
+# 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.
+
+
+from nova import log as logging
+from nova.scheduler import filters
+from nova import utils
+
+
+LOG = logging.getLogger(__name__)
+
+
+class ArchFilter(filters.BaseHostFilter):
+    """Filter out hosts that can not support the guest architecture.
+    Note: This is supported for libvirt only now.
+    """
+
+    def host_passes(self, host_state, filter_properties):
+        spec = filter_properties.get('request_spec', {})
+        props = spec.get('instance_properties', {})
+
+        cpu_info = host_state.capabilities.get('cpu_info')
+        permitted_instances = cpu_info.get('permitted_instance_types', None)
+
+        instance_arch = utils.sys_platform_translate(props.get('architecture'))
+
+        if permitted_instances and instance_arch in permitted_instances:
+            return True
+
+        LOG.warn(_('%(host_state)s fails permitted_instance_types'), locals())
+        return False
diff --git a/nova/tests/scheduler/test_host_filters.py b/nova/tests/scheduler/test_host_filters.py
index 60f3577ac..80da5acd2 100644
--- a/nova/tests/scheduler/test_host_filters.py
+++ b/nova/tests/scheduler/test_host_filters.py
@@ -793,3 +793,57 @@ class HostFiltersTestCase(test.TestCase):
         request = self._make_zone_request('bad')
         host = fakes.FakeHostState('host1', 'compute', {'service': service})
         self.assertFalse(filt_cls.host_passes(host, request))
+
+    def test_arch_filter_same(self):
+        permitted_instances = ['x86_64']
+        filt_cls = self.class_map['ArchFilter']()
+        filter_properties = {
+            'request_spec': {
+                'instance_properties': {'architecture': 'x86_64'}
+            }
+        }
+        capabilities = {'enabled': True,
+                            'cpu_info': {
+                                'permitted_instance_types': permitted_instances
+                            }
+                        }
+        service = {'disabled': False}
+        host = fakes.FakeHostState('host1', 'compute',
+            {'capabilities': capabilities, 'service': service})
+        self.assertTrue(filt_cls.host_passes(host, filter_properties))
+
+    def test_arch_filter_different(self):
+        permitted_instances = ['arm']
+        filt_cls = self.class_map['ArchFilter']()
+        filter_properties = {
+            'request_spec': {
+                    'instance_properties': {'architecture': 'x86_64'}
+                }
+            }
+        capabilities = {'enabled': True,
+                            'cpu_info': {
+                                'permitted_instance_types': permitted_instances
+                            }
+                        }
+        service = {'disabled': False}
+        host = fakes.FakeHostState('host1', 'compute',
+            {'capabilities': capabilities, 'service': service})
+        self.assertFalse(filt_cls.host_passes(host, filter_properties))
+
+    def test_arch_filter_without_permitted_instances(self):
+        permitted_instances = []
+        filt_cls = self.class_map['ArchFilter']()
+        filter_properties = {
+             'request_spec': {
+                'instance_properties': {'architecture': 'x86_64'}
+            }
+        }
+        capabilities = {'enabled': True,
+                            'cpu_info': {
+                                'permitted_instance_types': permitted_instances
+                            }
+                        }
+        service = {'disabled': False}
+        host = fakes.FakeHostState('host1', 'compute',
+            {'capabilities': capabilities, 'service': service})
+        self.assertFalse(filt_cls.host_passes(host, filter_properties))
diff --git a/nova/utils.py b/nova/utils.py
index ddc998524..8bd71359f 100644
--- a/nova/utils.py
+++ b/nova/utils.py
@@ -1321,6 +1321,15 @@ def strcmp_const_time(s1, s2):
     return result == 0
 
 
+def sys_platform_translate(arch):
+    """Translate cpu architecture into supported platforms."""
+    if (arch[0] == 'i' and arch[1].isdigit() and arch[2:4] == '86'):
+        arch = 'i686'
+    elif arch.startswith('arm'):
+        arch = 'arm'
+    return arch
+
+
 class UndoManager(object):
     """Provides a mechanism to facilitate rolling back a series of actions
     when an exception is raised.
diff --git a/nova/virt/libvirt/connection.py b/nova/virt/libvirt/connection.py
index 0dfc91928..7c09acc5a 100644
--- a/nova/virt/libvirt/connection.py
+++ b/nova/virt/libvirt/connection.py
@@ -1996,8 +1996,12 @@ class LibvirtDriver(driver.ComputeDriver):
         for nodes in feature_nodes:
             features.append(nodes.get('name'))
 
+        arch_nodes = xml.findall('.//guest/arch')
+        guest_cpu_arches = list(node.get('name') for node in arch_nodes)
+
         cpu_info['topology'] = topology
         cpu_info['features'] = features
+        cpu_info['permitted_instance_types'] = guest_cpu_arches
         return jsonutils.dumps(cpu_info)
 
     def block_stats(self, instance_name, disk):