rabbit: shuffle hosts before building kombu URL

This restores behavior as it was back in the Juno cycle.  This was
changed in a refactor during the Kilo cycle (973301aa) when the kombu
failover_strategy was set to shuffle.  But the failover_strategy only
affects failovers; it does not influence which host receives the
initial connection.

Thus, if multiple hosts are given, the first host will receive all of
the initial connections.  By shuffling the hosts before building the
URL given to kombu, rudimentary load balancing is achieved and
connections are more evenly spread across broker nodes.

Change-Id: Ieecaf5f286f49302db29df9854359ef5d36b7a89
(cherry picked from commit f2beb5eaf158f76cdb8be0ca72965503be423ee2)

1 files changed, 3 insertions, 0 deletions

diff --git a/oslo_messaging/_drivers/impl_rabbit.py b/oslo_messaging/_drivers/impl_rabbit.py
index fe279c4..9716b9c 100644
--- a/oslo_messaging/_drivers/impl_rabbit.py
+++ b/oslo_messaging/_drivers/impl_rabbit.py
@@ -17,6 +17,7 @@ import functools
 import itertools
 import logging
 import os
+import random
 import socket
 import ssl
 import threading
@@ -627,6 +628,7 @@ class Connection(object):
                 LOG.warn(_LW('Selecting the kombu transport through the '
                              'transport url (%s) is a experimental feature '
                              'and this is not yet supported.') % url.transport)
+            random.shuffle(url.hosts)
             for host in url.hosts:
                 transport = url.transport.replace('kombu+', '')
                 transport = transport.replace('rabbit', 'amqp')
@@ -644,6 +646,7 @@ class Connection(object):
             transport = url.transport.replace('kombu+', '')
             self._url = "%s://%s" % (transport, virtual_host)
         else:
+            random.shuffle(self.driver_conf.rabbit_hosts)
             for adr in self.driver_conf.rabbit_hosts:
                 hostname, port = netutils.parse_host_port(
                     adr, default_port=self.driver_conf.rabbit_port)