Add select_hosts to scheduler manager rpc

This adds a select_hosts(...) method to the scheduler manager
rpc that allows other services to query it for the best suited
host instead of relying on it to proxy its messages.

This can be used by extensions that need the scheduler to determine
the best-fit host but want to prepare and send their own messages
to that host.

Change-Id: I5b4760114dfcdb0464fac8ea81f46f7532ac0580

1 files changed, 5 insertions, 0 deletions

diff --git a/nova/scheduler/driver.py b/nova/scheduler/driver.py
index 2565e4e40..1a2e8254a 100644
--- a/nova/scheduler/driver.py
+++ b/nova/scheduler/driver.py
@@ -160,6 +160,11 @@ class Scheduler(object):
         msg = _("Driver must implement schedule_run_instance")
         raise NotImplementedError(msg)
 
+    def select_hosts(self, context, request_spec, filter_properties):
+        """Must override select_hosts method for scheduler to work."""
+        msg = _("Driver must implement select_hosts")
+        raise NotImplementedError(msg)
+
     def schedule_live_migration(self, context, instance, dest,
                                 block_migration, disk_over_commit):
         """Live migration scheduling method.