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

1 files changed, 11 insertions, 0 deletions

diff --git a/ironic/conductor/rpcapi.py b/ironic/conductor/rpcapi.py
index 8971360cb..6284e4034 100644
--- a/ironic/conductor/rpcapi.py
+++ b/ironic/conductor/rpcapi.py
@@ -29,6 +29,7 @@ from ironic.common import release_mappings as versions
 from ironic.common import rpc
 from ironic.conductor import manager
 from ironic.conf import CONF
+from ironic.db import api as dbapi
 from ironic.objects import base as objects_base
 
 
@@ -154,6 +155,16 @@ class ConductorAPI(object):
         hostname = self.get_conductor_for(node)
         return '%s.%s' % (self.topic, hostname)
 
+    def get_random_topic(self):
+        """Get an RPC topic for a random conductor service."""
+        conductors = dbapi.get_instance().get_online_conductors()
+        try:
+            hostname = random.choice(conductors)
+        except IndexError:
+            # There are no conductors - return 503 Service Unavailable
+            raise exception.TemporaryFailure()
+        return '%s.%s' % (self.topic, hostname)
+
     def get_topic_for_driver(self, driver_name):
         """Get RPC topic name for a conductor supporting the given driver.