Allocation API: allow picking random conductor for RPC topic

Allocations are not initially tied to nodes, so to process them we need
to pick a random alive conductor. This change enables that.

Change-Id: I6c950bc4f49aa03026bc7925f8c699d10cedc310
Story: #2004341

2 files changed, 15 insertions, 4 deletions

diff --git a/ironic/db/api.py b/ironic/db/api.py
index e43dc55da..c21d7454d 100644
--- a/ironic/db/api.py
+++ b/ironic/db/api.py
@@ -556,6 +556,13 @@ class Connection(object):
         """
 
     @abc.abstractmethod
+    def get_online_conductors(self):
+        """Get a list conductor hostnames that are online and active.
+
+        :returns: A list of conductor hostnames.
+        """
+
+    @abc.abstractmethod
     def list_conductor_hardware_interfaces(self, conductor_id):
         """List all registered hardware interfaces for a conductor.
 
diff --git a/ironic/db/sqlalchemy/api.py b/ironic/db/sqlalchemy/api.py
index beaca9339..65c436e96 100644
--- a/ironic/db/sqlalchemy/api.py
+++ b/ironic/db/sqlalchemy/api.py
@@ -916,10 +916,14 @@ class Connection(api.Connection):
     def get_offline_conductors(self):
         interval = CONF.conductor.heartbeat_timeout
         limit = timeutils.utcnow() - datetime.timedelta(seconds=interval)
-        result = (model_query(models.Conductor).filter_by()
-                  .filter(models.Conductor.updated_at < limit)
-                  .all())
-        return [row['hostname'] for row in result]
+        result = (model_query(models.Conductor.hostname)
+                  .filter(models.Conductor.updated_at < limit))
+        return [row[0] for row in result]
+
+    def get_online_conductors(self):
+        query = model_query(models.Conductor.hostname)
+        query = _filter_active_conductors(query)
+        return [row[0] for row in query]
 
     def list_conductor_hardware_interfaces(self, conductor_id):
         query = (model_query(models.ConductorHardwareInterfaces)