Fix driver task pattern to reduce periodic db load

Previously, a pattern of periodic tasks was created where
nodes, and in many cases, all nodes not actively locked nor
those in maintenance state, were pulled in by a periodic task.
These periodic tasks would then create tasks which generated
additional database queries in order to populate the task object.

With the task object populated, the driver would then evaluate
if the driver in question was for the the driver interface in
question and *then* evaluate if work had to be performed.

However, that field containing a pointer to if work needed to be
performed as often already queried from the database on the
very initial query to generate the list of nodes to evaluate.

In essence, we've moved this up in the sequence so we evaluate
that field in question prior to creating the task, potentially
across every conductor, depending on the query, and ultimately
which drivers are enabled.

This saves potentially saves hundreds of thousands of needless
database queries on a medium size deployment per single day,
depending on which drivers and driver interfaces are in use.

Change-Id: I409e87de2808d442d39e4d0ae6e995668230cbba

1 files changed, 7 insertions, 2 deletions

diff --git a/ironic/drivers/modules/irmc/raid.py b/ironic/drivers/modules/irmc/raid.py
index 901695632..34d1c3f38 100644
--- a/ironic/drivers/modules/irmc/raid.py
+++ b/ironic/drivers/modules/irmc/raid.py
@@ -434,6 +434,13 @@ class IRMCRAID(base.RAIDInterface):
         node_list = manager.iter_nodes(fields=fields, filters=filters)
         for (node_uuid, driver, conductor_group, raid_config) in node_list:
             try:
+                # NOTE(TheJulia): Evaluate based upon presence of raid
+                # configuration before triggering a task, as opposed to after
+                # so we don't create excess node task objects with related
+                # DB queries.
+                if not raid_config or raid_config.get('fgi_status'):
+                    continue
+
                 lock_purpose = 'checking async RAID configuration tasks'
                 with task_manager.acquire(context, node_uuid,
                                           purpose=lock_purpose,
@@ -444,8 +451,6 @@ class IRMCRAID(base.RAIDInterface):
                         continue
                     if task.node.target_raid_config is None:
                         continue
-                    if not raid_config or raid_config.get('fgi_status'):
-                        continue
                     task.upgrade_lock()
                     if node.provision_state != states.CLEANWAIT:
                         continue