Add a RequestSpec generation migration script

In Mitaka, we began to create and persist a RequestSpec object every time
a new instance was requested. Given that instances that were created before
that commit do not have a related RequestSpec, we needed to check
every time in the conductor methods whether the instance had a request spec
associated with it.

Now that we are in Newton, we can provide an online data migration script
that iterates over all the instances (using a marker), verify if the
RequestSpec object is created, and if not, try to persist into that object
the legacy fields we already know.

The marker uses the request_specs table for persisting itself, and
yes this is a hack, but that's the only solution we agreed for making sure
we were not looping every time on all the instances (which would be a
performance problem). When we finish looping over the instances, we
keep that marker so that the next call to that migration script
would not again iterate over all the instances (using the limit).

Change-Id: I61b9b50436d8bdb8ff06259cc2f876502d688b91
Partially-Implements: blueprint check-destination-on-migrations-newton

nova/cmd/manage.py

@@ -82,6 +82,7 @@ from nova.i18n import _
 from nova import objects
 from nova.objects import flavor as flavor_obj
 from nova.objects import instance as instance_obj
+from nova.objects import request_spec
 from nova import quota
 from nova import rpc
 from nova import utils
@@ -727,6 +728,7 @@ class DbCommands(object):
         flavor_obj.migrate_flavors,
         flavor_obj.migrate_flavor_reset_autoincrement,
         instance_obj.migrate_instance_keypairs,
+        request_spec.migrate_instances_add_request_spec,
     )
 
     def __init__(self):

nova/objects/request_spec.py

@@ -22,6 +22,7 @@ from nova import objects
 from nova.objects import base
 from nova.objects import fields
 from nova.objects import instance as obj_instance
+from nova.scheduler import utils as scheduler_utils
 from nova.virt import hardware
 
 
@@ -463,6 +464,90 @@ class RequestSpec(base.NovaObject):
         self.obj_reset_changes(['force_hosts', 'force_nodes'])
 
 
+# NOTE(sbauza): Since verifying a huge list of instances can be a performance
+# impact, we need to use a marker for only checking a set of them.
+# As the current model doesn't expose a way to persist that marker, we propose
+# here to use the request_specs table with a fake (and impossible) instance
+# UUID where the related spec field (which is Text) would be the marker, ie.
+# the last instance UUID we checked.
+# TODO(sbauza): Remove the CRUD helpers and the migration script in Ocata.
+
+# NOTE(sbauza): RFC4122 (4.1.7) allows a Nil UUID to be semantically accepted.
+FAKE_UUID = '00000000-0000-0000-0000-000000000000'
+
+
+@db.api_context_manager.reader
+def _get_marker_for_migrate_instances(context):
+    req_spec = (context.session.query(api_models.RequestSpec).filter_by(
+                instance_uuid=FAKE_UUID)).first()
+    marker = req_spec['spec'] if req_spec else None
+    return marker
+
+
+@db.api_context_manager.writer
+def _set_or_delete_marker_for_migrate_instances(context, marker=None):
+    # We need to delete the old marker anyway, which no longer corresponds to
+    # the last instance we checked (if there was a marker)...
+    # NOTE(sbauza): delete() deletes rows that match the query and if none
+    # are found, returns 0 hits.
+    context.session.query(api_models.RequestSpec).filter_by(
+        instance_uuid=FAKE_UUID).delete()
+    if marker is not None:
+        # ... but there can be a new marker to set
+        db_mapping = api_models.RequestSpec()
+        db_mapping.update({'instance_uuid': FAKE_UUID, 'spec': marker})
+        db_mapping.save(context.session)
+
+
+def _create_minimal_request_spec(context, instance):
+    image = instance.image_meta
+    # TODO(sbauza): Modify that once setup_instance_group() accepts a
+    # RequestSpec object
+    request_spec = {'instance_properties': {'uuid': instance.uuid}}
+    filter_properties = {}
+    scheduler_utils.setup_instance_group(context, request_spec,
+                                         filter_properties)
+    # This is an old instance. Let's try to populate a RequestSpec
+    # object using the existing information we have previously saved.
+    request_spec = objects.RequestSpec.from_components(
+        context, instance.uuid, image,
+        instance.flavor, instance.numa_topology,
+        instance.pci_requests,
+        filter_properties, None, instance.availability_zone
+    )
+    request_spec.create()
+
+
+def migrate_instances_add_request_spec(context, max_count):
+    """Creates and persists a RequestSpec per instance not yet having it."""
+    marker = _get_marker_for_migrate_instances(context)
+    # Prevent lazy-load of those fields for every instance later.
+    attrs = ['system_metadata', 'flavor', 'pci_requests', 'numa_topology',
+             'availability_zone']
+    instances = objects.InstanceList.get_by_filters(context,
+                                                    filters={'deleted': False},
+                                                    sort_key='created_at',
+                                                    sort_dir='asc',
+                                                    limit=max_count,
+                                                    marker=marker,
+                                                    expected_attrs=attrs)
+    count_all = len(instances)
+    count_hit = 0
+    for instance in instances:
+        try:
+            RequestSpec.get_by_instance_uuid(context, instance.uuid)
+        except exception.RequestSpecNotFound:
+            _create_minimal_request_spec(context, instance)
+            count_hit += 1
+    if count_all > 0:
+        # We want to persist which last instance was checked in order to make
+        # sure we don't review it again in a next call.
+        marker = instances[-1].uuid
+
+    _set_or_delete_marker_for_migrate_instances(context, marker)
+    return count_all, count_hit
+
+
 @base.NovaObjectRegistry.register
 class SchedulerRetries(base.NovaObject):
     # Version 1.0: Initial version

nova/tests/functional/db/test_request_spec.py

@@ -10,14 +10,23 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 
+from oslo_config import cfg
+
 from nova import context
+from nova.db.sqlalchemy import api as db
+from nova.db.sqlalchemy import api_models
 from nova import exception
+from nova import objects
 from nova.objects import base as obj_base
 from nova.objects import request_spec
 from nova import test
 from nova.tests import fixtures
+from nova.tests.functional import integrated_helpers
+from nova.tests.unit import fake_network
 from nova.tests.unit import fake_request_spec
 
+CONF = cfg.CONF
+
 
 class RequestSpecTestCase(test.NoDBTestCase):
     USES_DB_SELF = True
@@ -62,3 +71,84 @@ class RequestSpecTestCase(test.NoDBTestCase):
     def test_double_create(self):
         spec = self._create_spec()
         self.assertRaises(exception.ObjectActionError, spec.create)
+
+
+@db.api_context_manager.writer
+def _delete_request_spec(context, instance_uuid):
+    """Deletes a RequestSpec by the instance_uuid."""
+    context.session.query(api_models.RequestSpec).filter_by(
+        instance_uuid=instance_uuid).delete()
+
+
+class RequestSpecInstanceMigrationTestCase(
+        integrated_helpers._IntegratedTestBase):
+    api_major_version = 'v2.1'
+    _image_ref_parameter = 'imageRef'
+    _flavor_ref_parameter = 'flavorRef'
+
+    def setUp(self):
+        super(RequestSpecInstanceMigrationTestCase, self).setUp()
+
+        self.context = context.get_admin_context()
+        fake_network.set_stub_network_methods(self)
+
+    def _create_instances(self, old=2, total=5):
+        request = self._build_minimal_create_server_request()
+        # Create all instances that would set a RequestSpec object
+        request.update({'max_count': total})
+        self.api.post_server({'server': request})
+
+        self.instances = objects.InstanceList.get_all(self.context)
+        # Make sure that we have all the needed instances
+        self.assertEqual(total, len(self.instances))
+
+        # Fake the legacy behaviour by removing the RequestSpec for some old.
+        for i in range(0, old):
+            _delete_request_spec(self.context, self.instances[i].uuid)
+
+        # Just add a deleted instance to make sure we don't create
+        # a RequestSpec object for it.
+        del request['max_count']
+        server = self.api.post_server({'server': request})
+        self.api.delete_server(server['id'])
+        # Make sure we have the deleted instance only soft-deleted in DB
+        deleted_instances = objects.InstanceList.get_by_filters(
+            self.context, filters={'deleted': True})
+        self.assertEqual(1, len(deleted_instances))
+
+    def test_migration(self):
+        self._create_instances(old=2, total=5)
+
+        match, done = request_spec.migrate_instances_add_request_spec(
+            self.context, 2)
+        self.assertEqual(2, match)
+        self.assertEqual(2, done)
+
+        # Run again the migration call for making sure that we don't check
+        # again the same instances
+        match, done = request_spec.migrate_instances_add_request_spec(
+            self.context, 3)
+        self.assertEqual(3, match)
+        self.assertEqual(0, done)
+
+        # Make sure we ran over all the instances
+        match, done = request_spec.migrate_instances_add_request_spec(
+            self.context, 50)
+        self.assertEqual(0, match)
+        self.assertEqual(0, done)
+
+        # Make sure all instances have now a related RequestSpec
+        for uuid in [instance.uuid for instance in self.instances]:
+            try:
+                objects.RequestSpec.get_by_instance_uuid(self.context, uuid)
+            except exception.RequestSpecNotFound:
+                self.fail("RequestSpec not found for instance UUID :%s ", uuid)
+
+    def test_migration_with_none_old(self):
+        self._create_instances(old=0, total=5)
+
+        # Make sure no migrations can be found
+        match, done = request_spec.migrate_instances_add_request_spec(
+            self.context, 50)
+        self.assertEqual(5, match)
+        self.assertEqual(0, done)