Add debug logs for weigher filters

Add logs for weigher filters so that we can debug from
the log.

Change-Id: I95f6145c77028aee4cce310c7b2a9636fdeed5d8

cinder/scheduler/base_weight.py

@@ -19,11 +19,15 @@ Pluggable Weighing support
 
 import abc
 
+from oslo_log import log as logging
 import six
 
 from cinder.scheduler import base_handler
 
 
+LOG = logging.getLogger(__name__)
+
+
 def normalize(weight_list, minval=None, maxval=None):
     """Normalize the values in a list between 0 and 1.0.
 
@@ -142,4 +146,10 @@ class BaseWeightHandler(base_handler.BaseHandler):
                 obj = weighed_objs[i]
                 obj.weight += weigher.weight_multiplier() * weight
 
+            LOG.debug("Weigher %(cls_name)s returned, "
+                      "weigher value is {max: %(maxval)s, min: %(minval)s}",
+                      {'cls_name': weigher_cls.__name__,
+                       'maxval': weigher.maxval,
+                       'minval': weigher.minval})
+
         return sorted(weighed_objs, key=lambda x: x.weight, reverse=True)

cinder/scheduler/host_manager.py

@@ -493,9 +493,12 @@ class HostManager(object):
                              weigher_class_names=None):
         """Weigh the backends."""
         weigher_classes = self._choose_backend_weighers(weigher_class_names)
-        return self.weight_handler.get_weighed_objects(weigher_classes,
-                                                       backends,
-                                                       weight_properties)
+
+        weighed_backends = self.weight_handler.get_weighed_objects(
+            weigher_classes, backends, weight_properties)
+
+        LOG.debug("Weighed %s", weighed_backends)
+        return weighed_backends
 
     def update_service_capabilities(self, service_name, host, capabilities,
                                     cluster_name, timestamp):