Periodic task _poll_unconfirmed_resizes can now use slave db

This allows the _poll_unconfirmed_resizes periodic task to use the
slave db for reads if the deployment has a slave configured. For
slaveless deployments behavior remains unchanged.

This commit advances the MigrationList object to version 1.1

Change-Id: I10bf729e92dc599819ef74a97a834c7f2df5b162
Partially-implements: blueprint periodic-tasks-to-db-slave

nova/compute/manager.py

@@ -4530,7 +4530,8 @@ class ComputeManager(manager.SchedulerDependentManager):
 
         mig_list_cls = migration_obj.MigrationList
         migrations = mig_list_cls.get_unconfirmed_by_dest_compute(
-                context, CONF.resize_confirm_window, self.host)
+                context, CONF.resize_confirm_window, self.host,
+                use_slave=True)
 
         migrations_info = dict(migration_count=len(migrations),
                 confirm_window=CONF.resize_confirm_window)
@@ -4557,7 +4558,8 @@ class ComputeManager(manager.SchedulerDependentManager):
             expected_attrs = ['metadata', 'system_metadata']
             try:
                 instance = instance_obj.Instance.get_by_uuid(context,
-                            instance_uuid, expected_attrs=expected_attrs)
+                            instance_uuid, expected_attrs=expected_attrs,
+                            use_slave=True)
             except exception.InstanceNotFound:
                 reason = (_("Instance %s not found") %
                           instance_uuid)

nova/db/api.py

@@ -442,13 +442,13 @@ def migration_get_by_instance_and_status(context, instance_uuid, status):
 
 
 def migration_get_unconfirmed_by_dest_compute(context, confirm_window,
-        dest_compute):
+        dest_compute, use_slave=False):
     """
     Finds all unconfirmed migrations within the confirmation window for
     a specific destination compute host.
     """
     return IMPL.migration_get_unconfirmed_by_dest_compute(context,
-            confirm_window, dest_compute)
+            confirm_window, dest_compute, use_slave=use_slave)
 
 
 def migration_get_in_progress_by_host_and_node(context, host, node):

nova/db/sqlalchemy/api.py

@@ -4025,15 +4025,16 @@ def migration_get_by_instance_and_status(context, instance_uuid, status):
 
 @require_admin_context
 def migration_get_unconfirmed_by_dest_compute(context, confirm_window,
-                                              dest_compute):
+                                              dest_compute, use_slave=False):
     confirm_window = (timeutils.utcnow() -
                       datetime.timedelta(seconds=confirm_window))
 
-    return model_query(context, models.Migration, read_deleted="yes").\
-            filter(models.Migration.updated_at <= confirm_window).\
-            filter_by(status="finished").\
-            filter_by(dest_compute=dest_compute).\
-            all()
+    return model_query(context, models.Migration, read_deleted="yes",
+                       use_slave=use_slave).\
+             filter(models.Migration.updated_at <= confirm_window).\
+             filter_by(status="finished").\
+             filter_by(dest_compute=dest_compute).\
+             all()
 
 
 @require_admin_context

nova/objects/migration.py

@@ -86,15 +86,19 @@ def _make_list(context, list_obj, item_cls, db_list):
 
 
 class MigrationList(base.ObjectListBase, base.NovaObject):
+    # Version 1.0: Initial version
+    # Version 1.1: Added use_slave to get_unconfirmed_by_dest_compute
+    VERSION = '1.1'
+
     fields = {
         'objects': fields.ListOfObjectsField('Migration'),
         }
 
     @base.remotable_classmethod
     def get_unconfirmed_by_dest_compute(cls, context, confirm_window,
-                                        dest_compute):
+                                        dest_compute, use_slave=False):
         db_migrations = db.migration_get_unconfirmed_by_dest_compute(
-            context, confirm_window, dest_compute)
+            context, confirm_window, dest_compute, use_slave=use_slave)
         return _make_list(context, MigrationList(), Migration, db_migrations)
 
     @base.remotable_classmethod

nova/tests/compute/test_compute.py

@@ -5092,7 +5092,7 @@ class ComputeTestCase(BaseTestCase):
                     return instance
 
         def fake_migration_get_unconfirmed_by_dest_compute(context,
-                resize_confirm_window, dest_compute):
+                resize_confirm_window, dest_compute, use_slave=False):
             self.assertEqual(dest_compute, CONF.host)
             return migrations
 

nova/tests/objects/test_migration.py

@@ -118,11 +118,12 @@ class _TestMigrationObject(object):
         self.mox.StubOutWithMock(
             db, 'migration_get_unconfirmed_by_dest_compute')
         db.migration_get_unconfirmed_by_dest_compute(
-            ctxt, 'window', 'foo').AndReturn(db_migrations)
+            ctxt, 'window', 'foo',
+            use_slave=False).AndReturn(db_migrations)
         self.mox.ReplayAll()
         migrations = (
             migration.MigrationList.get_unconfirmed_by_dest_compute(
-                ctxt, 'window', 'foo'))
+                ctxt, 'window', 'foo', use_slave=False))
         self.assertEqual(2, len(migrations))
         for index, db_migration in enumerate(db_migrations):
             self.compare_obj(migrations[index], db_migration)