From cf8e81699c90c396b76e3252579acfc5cb722621 Mon Sep 17 00:00:00 2001
From: Balazs Gibizer <balazs.gibizer@est.tech>
Date: Thu, 11 Nov 2021 19:06:56 +0100
Subject: [PATCH] Add debug log for scheduler weight calculation

We have all the weighers enabled by default and each can have its own
multiplier making the final compute node order calculation pretty
complex. This patch adds some debug logging that helps understanding how
the final ordering was reached.

Change-Id: I7606d6eb3e08548c1df9dc245ab39cced7de1fb5
(cherry picked from commit 154ab7b2f9ad80fe432d2c036d5e8c4ee171897b)
(cherry picked from commit 30c7180e1e655176952609e80f1f21cf8b6d13a0)
---
 nova/weights.py | 40 ++++++++++++++++++++++++++++++++++++----
 1 file changed, 36 insertions(+), 4 deletions(-)

diff --git a/nova/weights.py b/nova/weights.py
index a093df03455..b88caaa1862 100644
--- a/nova/weights.py
+++ b/nova/weights.py
@@ -19,9 +19,14 @@
 
 import abc
 
+from oslo_log import log as logging
+
 from nova import loadables
 
 
+LOG = logging.getLogger(__name__)
+
+
 def normalize(weight_list, minval=None, maxval=None):
     """Normalize the values in a list between 0 and 1.0.
 
@@ -127,13 +132,40 @@ def get_weighed_objects(self, weighers, obj_list, weighing_properties):
         for weigher in weighers:
             weights = weigher.weigh_objects(weighed_objs, weighing_properties)
 
+            LOG.debug(
+                "%s: raw weights %s",
+                weigher.__class__.__name__,
+                {(obj.obj.host, obj.obj.nodename): weight
+                 for obj, weight in zip(weighed_objs, weights)}
+            )
+
             # Normalize the weights
-            weights = normalize(weights,
-                                minval=weigher.minval,
-                                maxval=weigher.maxval)
+            weights = list(
+                normalize(
+                    weights, minval=weigher.minval, maxval=weigher.maxval))
+
+            LOG.debug(
+                "%s: normalized weights %s",
+                weigher.__class__.__name__,
+                {(obj.obj.host, obj.obj.nodename): weight
+                 for obj, weight in zip(weighed_objs, weights)}
+            )
+
+            log_data = {}
 
             for i, weight in enumerate(weights):
                 obj = weighed_objs[i]
-                obj.weight += weigher.weight_multiplier(obj.obj) * weight
+                multiplier = weigher.weight_multiplier(obj.obj)
+                weigher_score = multiplier * weight
+                obj.weight += weigher_score
+
+                log_data[(obj.obj.host, obj.obj.nodename)] = (
+                    f"{multiplier} * {weight}")
+
+            LOG.debug(
+                "%s: score (multiplier * weight) %s",
+                weigher.__class__.__name__,
+                {name: log for name, log in log_data.items()}
+            )
 
         return sorted(weighed_objs, key=lambda x: x.weight, reverse=True)