Remove db session hack from conductor's vol_usage_update()

Commit 3cf4cb2534c387f287f118d4185d54b1435d3bc0 made the
vol_usage_update() in conductor hack around a stale sqlalchemy
object issue by keeping session active in the current context
until the notification was completed. This layering violation
led to some "creative" tests to try to verify this behavior.

This removes that and refreshes the object before letting it
out of the db/api layer so that all the attributes are present,
thus avoiding the dynamic load during notification.

Change-Id: Ia6ef5cb7f462ff72d170f3af33f2d020ee4d3e3c

4 files changed, 8 insertions, 13 deletions

diff --git a/nova/conductor/manager.py b/nova/conductor/manager.py
index 6693e7fee..3b8c5f55d 100644
--- a/nova/conductor/manager.py
+++ b/nova/conductor/manager.py
@@ -26,7 +26,6 @@ from nova import network
 from nova.network.security_group import openstack_driver
 from nova import notifications
 from nova.objects import base as nova_object
-from nova.openstack.common.db.sqlalchemy import session as db_session
 from nova.openstack.common import jsonutils
 from nova.openstack.common import log as logging
 from nova.openstack.common.notifier import api as notifier
@@ -343,9 +342,6 @@ class ConductorManager(manager.Manager):
     def vol_usage_update(self, context, vol_id, rd_req, rd_bytes, wr_req,
                          wr_bytes, instance, last_refreshed=None,
                          update_totals=False):
-        # The session object is needed here, as the vol_usage object returned
-        # needs to bound to it in order to refresh its data
-        session = db_session.get_session()
         vol_usage = self.db.vol_usage_update(context, vol_id,
                                              rd_req, rd_bytes,
                                              wr_req, wr_bytes,
@@ -353,8 +349,7 @@ class ConductorManager(manager.Manager):
                                              instance['project_id'],
                                              instance['user_id'],
                                              instance['availability_zone'],
-                                             update_totals,
-                                             session)
+                                             update_totals)
 
         # We have just updated the database, so send the notification now
         notifier.notify(context, 'conductor.%s' % self.host, 'volume.usage',
diff --git a/nova/db/api.py b/nova/db/api.py
index ceab5fcd8..973be1a26 100644
--- a/nova/db/api.py
+++ b/nova/db/api.py
@@ -1561,7 +1561,7 @@ def vol_get_usage_by_time(context, begin):
 
 def vol_usage_update(context, id, rd_req, rd_bytes, wr_req, wr_bytes,
                      instance_id, project_id, user_id, availability_zone,
-                     update_totals=False, session=None):
+                     update_totals=False):
     """Update cached volume usage for a volume
 
        Creates new record if needed.
@@ -1569,8 +1569,7 @@ def vol_usage_update(context, id, rd_req, rd_bytes, wr_req, wr_bytes,
     return IMPL.vol_usage_update(context, id, rd_req, rd_bytes, wr_req,
                                  wr_bytes, instance_id, project_id, user_id,
                                  availability_zone,
-                                 update_totals=update_totals,
-                                 session=session)
+                                 update_totals=update_totals)
 
 
 ###################
diff --git a/nova/db/sqlalchemy/api.py b/nova/db/sqlalchemy/api.py
index 25108b062..b8ee76053 100644
--- a/nova/db/sqlalchemy/api.py
+++ b/nova/db/sqlalchemy/api.py
@@ -4408,9 +4408,8 @@ def vol_get_usage_by_time(context, begin):
 @require_context
 def vol_usage_update(context, id, rd_req, rd_bytes, wr_req, wr_bytes,
                      instance_id, project_id, user_id, availability_zone,
-                     update_totals=False, session=None):
-    if not session:
-        session = get_session()
+                     update_totals=False):
+    session = get_session()
 
     refreshed = timeutils.utcnow()
 
@@ -4483,6 +4482,8 @@ def vol_usage_update(context, id, rd_req, rd_bytes, wr_req, wr_bytes,
                         current_usage['curr_write_bytes'] + wr_bytes)
 
             current_usage.update(values)
+            current_usage.save(session=session)
+            session.refresh(current_usage)
             return current_usage
 
         vol_usage = models.VolumeUsage()
diff --git a/nova/tests/conductor/test_conductor.py b/nova/tests/conductor/test_conductor.py
index 7a33cfbb9..9bb2c00ec 100644
--- a/nova/tests/conductor/test_conductor.py
+++ b/nova/tests/conductor/test_conductor.py
@@ -389,7 +389,7 @@ class _BaseTestCase(object):
                             fake_inst['project_id'],
                             fake_inst['user_id'],
                             fake_inst['availability_zone'],
-                            False, mox.IgnoreArg()).AndReturn('fake-usage')
+                            False).AndReturn('fake-usage')
         compute_utils.usage_volume_info('fake-usage').AndReturn('fake-info')
         notifier_api.notify(self.context,
                             'conductor.%s' % self.conductor_manager.host,