Refactors select_destinations to return HostState objects

This is needed because we will need to pass 'limits'
(resource oversubscription values for the compute host)
attribute along with filter_properties to the compute manager.

Partially implements bp cold-migrations-to-conductor

Change-Id: Ide3a9781f66f961ff4aceadc00275de91c6c1030

nova/scheduler/chance.py

@@ -28,6 +28,7 @@ from oslo.config import cfg
 from nova.compute import rpcapi as compute_rpcapi
 from nova import exception
 from nova.scheduler import driver
+from nova.scheduler import host_manager
 
 CONF = cfg.CONF
 CONF.import_opt('compute_topic', 'nova.compute.rpcapi')
@@ -75,10 +76,15 @@ class ChanceScheduler(driver.Scheduler):
     def select_destinations(self, context, request_spec, filter_properties):
         """Selects random destinations."""
         num_instances = request_spec['num_instances']
-        # NOTE(alaski): Returns a list of tuples for compatibility with
-        # filter_scheduler
-        dests = [(self._schedule(context, CONF.compute_topic, request_spec,
-                filter_properties), None) for i in range(num_instances)]
+        # NOTE(alaski): Returns a list of HostState objects for compatibility
+        # with filter_scheduler
+        dests = []
+        for i in range(num_instances):
+            host = self._schedule(context, CONF.compute_topic,
+                    request_spec, filter_properties)
+            host_state = host_manager.HostState(host, None)
+            dests.append(host_state)
+
         if len(dests) < num_instances:
             raise exception.NoValidHost(reason='')
         return dests

nova/scheduler/filter_scheduler.py

@@ -172,9 +172,8 @@ class FilterScheduler(driver.Scheduler):
         if len(selected_hosts) < num_instances:
             raise exception.NoValidHost(reason='')
 
-        dests = []
-        for host in selected_hosts:
-            dests.append((host.obj.host, host.obj.nodename))
+        # Returns HostState objects.
+        dests = [host.obj for host in selected_hosts]
         return dests
 
     def _provision_resource(self, context, weighed_host, request_spec,

nova/tests/scheduler/test_chance_scheduler.py

@@ -220,10 +220,10 @@ class ChanceSchedulerTestCase(test_scheduler.SchedulerTestCase):
         self.mox.ReplayAll()
         dests = self.driver.select_destinations(ctxt, request_spec, {})
         self.assertEquals(2, len(dests))
-        (host, node) = dests[0]
+        (host, node) = (dests[0].host, dests[0].nodename)
         self.assertEquals('host3', host)
         self.assertEquals(None, node)
-        (host, node) = dests[1]
+        (host, node) = (dests[1].host, dests[1].nodename)
         self.assertEquals('host2', host)
         self.assertEquals(None, node)
 

nova/tests/scheduler/test_filter_scheduler.py

@@ -651,7 +651,7 @@ class FilterSchedulerTestCase(test_scheduler.SchedulerTestCase):
                         'num_instances': 1}
         self.mox.ReplayAll()
         dests = sched.select_destinations(fake_context, request_spec, {})
-        (host, node) = dests[0]
+        (host, node) = (dests[0].host, dests[0].nodename)
         self.assertEquals(host, selected_hosts[0])
         self.assertEquals(node, selected_nodes[0])