Respond to rpc requests on stop until hash ring reset

Currently when a conductor is stopped, the rpc service stops
responding to requests as soon as self.manager.del_host returns. This
means that until the hash ring is reset on the whole cluster, requests
can be sent to a service which is stopped.

This change waits for the remaining seconds to delay stopping until
CONF.hash_ring_reset_interval has elapsed. This will improve the
reliability of the cluster when scaling down or rolling out updates.

This delay only occurs when there is more than one online conductor,
to allow fast restarts on single-node ironic installs (bifrost,
metal3).

Change-Id: I643eb34f9605532c5c12dd2a42f4ea67bf3e0b40

1 files changed, 4 insertions, 0 deletions

diff --git a/ironic/conductor/base_manager.py b/ironic/conductor/base_manager.py
index 22ebd57f5..5c2e4ea95 100644
--- a/ironic/conductor/base_manager.py
+++ b/ironic/conductor/base_manager.py
@@ -334,6 +334,10 @@ class BaseConductorManager(object):
 
         self._started = False
 
+    def get_online_conductor_count(self):
+        """Return a count of currently online conductors"""
+        return len(self.dbapi.get_online_conductors())
+
     def _register_and_validate_hardware_interfaces(self, hardware_types):
         """Register and validate hardware interfaces for this conductor.