From d05d4e77df0bdfd2b802186762391d7f91361701 Mon Sep 17 00:00:00 2001 From: "Kevin L. Mitchell" Date: Fri, 9 Sep 2011 14:35:38 -0500 Subject: Add comment to document why random.shuffle() works --- nova/scheduler/abstract_scheduler.py | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/nova/scheduler/abstract_scheduler.py b/nova/scheduler/abstract_scheduler.py index b4c2bf4f1..e4f615b94 100644 --- a/nova/scheduler/abstract_scheduler.py +++ b/nova/scheduler/abstract_scheduler.py @@ -296,6 +296,13 @@ class AbstractScheduler(driver.Scheduler): "child_blob": weighting["blob"]} weighted_hosts.append(host_dict) if FLAGS.spread_first: + # NOTE(Vek): If all the weights are unique, then the sort + # below undoes this shuffle; however, if + # several responses from several zones have the + # same weight, then this shuffle serves to + # break up the monolithic blocks and cause the + # instances to be uniformly spread across the + # zones. random.shuffle(weighted_hosts) weighted_hosts.sort(key=operator.itemgetter('weight')) return weighted_hosts -- cgit