Pep8 fixes

nova/scheduler/least_cost.py

@@ -13,16 +13,19 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 """
-Helpful docstring here
+Least Cost Scheduler is a mechanism for choosing which host machines to
+provision a set of resources to. The input of the least-cost-scheduler is a
+set of objective-functions, called the 'cost-functions', a weight for each
+cost-function, and a list of candidate hosts (gathered via FilterHosts).
+
+The cost-function and weights are tabulated, and the host with the least cost
+is then selected for provisioning.
 """
 
 import collections
 
 from nova import flags
 from nova import log as logging
-# TODO(sirp): this should be just `zone_aware` to match naming scheme
-# TODO(sirp): perhaps all zone-aware stuff should go under a `zone_aware`
-# module
 from nova.scheduler import zone_aware_scheduler
 from nova import utils
 
@@ -38,6 +41,8 @@ flags.DEFINE_list('least_cost_scheduler_cost_functions',
 # cost_functions.py file (perhaps in a least_cost_scheduler directory)
 flags.DEFINE_integer('noop_cost_fn_weight', 1,
                      'How much weight to give the noop cost function')
+
+
 def noop_cost_fn(host):
     """Return a pre-weight cost of 1 for each host"""
     return 1
@@ -45,6 +50,8 @@ def noop_cost_fn(host):
 
 flags.DEFINE_integer('fill_first_cost_fn_weight', 1,
                      'How much weight to give the fill-first cost function')
+
+
 def fill_first_cost_fn(host):
     """Prefer hosts that have less ram available, filter_hosts will exclude
     hosts that don't have enough ram"""
@@ -68,7 +75,7 @@ class LeastCostScheduler(zone_aware_scheduler.ZoneAwareScheduler):
             except exception.ClassNotFound:
                 raise exception.SchedulerCostFunctionNotFound(
                     cost_fn_str=cost_fn_str)
-          
+
             try:
                 weight = getattr(FLAGS, "%s_weight" % cost_fn.__name__)
             except AttributeError:
@@ -82,17 +89,22 @@ class LeastCostScheduler(zone_aware_scheduler.ZoneAwareScheduler):
     def weigh_hosts(self, num, request_spec, hosts):
         """Returns a list of dictionaries of form:
             [ {weight: weight, hostname: hostname} ]"""
+
         # FIXME(sirp): weigh_hosts should handle more than just instances
-        hostnames = [hostname for hostname, _ in hosts]
+        hostnames = [hostname for hostname, caps in hosts]
 
         cost_fns = self.get_cost_fns()
         costs = weighted_sum(domain=hosts, weighted_fns=cost_fns)
-        
+
         weighted = []
+        weight_log = []
         for cost, hostname in zip(costs, hostnames):
+            weight_log.append("%s: %s" % (hostname, "%.2f" % cost))
             weight_dict = dict(weight=cost, hostname=hostname)
             weighted.append(weight_dict)
-        return weighted 
+
+        LOG.debug(_("Weighted Costs => %s") % weight_log)
+        return weighted
 
 
 def normalize_list(L):
@@ -110,7 +122,7 @@ def weighted_sum(domain, weighted_fns, normalize=True):
     """Use the weighted-sum method to compute a score for an array of objects.
     Normalize the results of the objective-functions so that the weights are
     meaningful regardless of objective-function's range.
-    
+
     domain - input to be scored
     weighted_fns - list of weights and functions like:
         [(weight, objective-functions)]

nova/scheduler/zone_aware_scheduler.py

@@ -80,7 +80,7 @@ class ZoneAwareScheduler(driver.Scheduler):
             LOG.debug(_("Casted to compute %(host)s for run_instance")
                                 % locals())
         else:
-            # TODO(sandy) Provision in child zone ... 
+            # TODO(sandy) Provision in child zone ...
             LOG.warning(_("Provision to Child Zone not supported (yet)")
                                 % locals())
             pass
@@ -117,11 +117,11 @@ class ZoneAwareScheduler(driver.Scheduler):
         # Filter local hosts based on requirements ...
         host_list = self.filter_hosts(num_instances, request_spec)
 
-        # then weigh the selected hosts.
-        # weighted = [{weight=weight, name=hostname}, ...]
-
         # TODO(sirp): weigh_hosts should also be a function of 'topic' or
         # resources, so that we can apply different objective functions to it
+
+        # then weigh the selected hosts.
+        # weighted = [{weight=weight, name=hostname}, ...]
         weighted = self.weigh_hosts(num_instances, request_spec, host_list)
 
         # Next, tack on the best weights from the child zones ...
@@ -145,8 +145,9 @@ class ZoneAwareScheduler(driver.Scheduler):
         """Derived classes must override this method and return
            a list of hosts in [(hostname, capability_dict)] format."""
         # NOTE(sirp): The default logic is the equivalent to AllHostsFilter
+        service_states = self.zone_manager.service_states
         return [(host, services)
-                for host, services in self.zone_manager.service_states.iteritems()]
+                for host, services in service_states.iteritems()]
 
     def weigh_hosts(self, num, request_spec, hosts):
         """Derived classes may override this to provide more sophisticated

nova/tests/test_least_cost_scheduler.py

@@ -30,6 +30,7 @@ class FakeHost(object):
         self.free_ram = free_ram
         self.io = io
 
+
 class WeightedSumTestCase(test.TestCase):
     def test_empty_domain(self):
         domain = []
@@ -50,14 +51,15 @@ class WeightedSumTestCase(test.TestCase):
             (2, lambda h: h.io),  # Avoid high I/O
         ]
 
-        costs = least_cost.weighted_sum(domain=hosts, weighted_fns=weighted_fns)
+        costs = least_cost.weighted_sum(
+            domain=hosts, weighted_fns=weighted_fns)
 
         # Each 256 MB unit of free-ram contributes 0.5 points by way of:
         #   cost = weight * (score/max_score) = 1 * (256/512) = 0.5
         # Each 100 iops of IO adds 0.5 points by way of:
         #   cost = 2 * (100/400) = 2 * 0.25 = 0.5
         expected = [1.5, 2.5, 1.5]
-        self.assertEqual(expected, costs) 
+        self.assertEqual(expected, costs)
 
 
 # TODO(sirp): unify this with test_host_filter tests? possibility of sharing
@@ -65,6 +67,7 @@ class WeightedSumTestCase(test.TestCase):
 class FakeZoneManager:
     pass
 
+
 class LeastCostSchedulerTestCase(test.TestCase):
     def _host_caps(self, multiplier):
         # Returns host capabilities in the following way:
@@ -116,7 +119,6 @@ class LeastCostSchedulerTestCase(test.TestCase):
         #FLAGS.default_host_filter_driver = self.old_flag
         super(LeastCostSchedulerTestCase, self).tearDown()
 
-
     def assertWeights(self, expected, num, request_spec, hosts):
         weighted = self.sched.weigh_hosts(num, request_spec, hosts)
         self.assertDictListMatch(weighted, expected, approx_equal=True)
@@ -138,8 +140,9 @@ class LeastCostSchedulerTestCase(test.TestCase):
         num = 1
         request_spec = {}
         hosts = self.sched.filter_hosts(num, request_spec)
-        
+
-        expected = [ dict(weight=1, hostname=hostname) for hostname, caps in hosts]
+        expected = [dict(weight=1, hostname=hostname)
+                    for hostname, caps in hosts]
         self.assertWeights(expected, num, request_spec, hosts)
 
     def test_cost_fn_weights(self):
@@ -152,7 +155,8 @@ class LeastCostSchedulerTestCase(test.TestCase):
         request_spec = {}
         hosts = self.sched.filter_hosts(num, request_spec)
 
-        expected = [ dict(weight=2, hostname=hostname) for hostname, caps in hosts]
+        expected = [dict(weight=2, hostname=hostname)
+                    for hostname, caps in hosts]
         self.assertWeights(expected, num, request_spec, hosts)
 
     def test_fill_first_cost_fn(self):
@@ -164,7 +168,7 @@ class LeastCostSchedulerTestCase(test.TestCase):
         num = 1
         request_spec = {}
         hosts = self.sched.filter_hosts(num, request_spec)
-       
+
         expected = []
         for idx, (hostname, caps) in enumerate(hosts):
             # Costs are normalized so over 10 hosts, each host with increasing