Make weigh_hosts() return a host per instance, instead of just a list of hosts.

nova/scheduler/base_scheduler.py

@@ -55,5 +55,17 @@ class BaseScheduler(abstract_scheduler.AbstractScheduler):
         scheduling objectives
         """
         # NOTE(sirp): The default logic is the same as the NoopCostFunction
-        return [dict(weight=1, hostname=hostname, capabilities=capabilities)
+        hosts = [dict(weight=1, hostname=hostname, capabilities=capabilities)
-                for hostname, capabilities in hosts]
+                 for hostname, capabilities in hosts]
+
+        # NOTE(Vek): What we actually need to return is enough hosts
+        #            for all the instances!
+        num_instances = request_spec.get('num_instances', 1)
+        instances = []
+        while num_instances > len(hosts):
+            instances.extend(hosts)
+            num_instances -= len(hosts)
+        if num_instances > 0:
+            instances.extend(hosts[:num_instances])
+
+        return instances

nova/tests/scheduler/test_abstract_scheduler.py

@@ -26,6 +26,7 @@ from nova import test
 from nova.compute import api as compute_api
 from nova.scheduler import driver
 from nova.scheduler import abstract_scheduler
+from nova.scheduler import base_scheduler
 from nova.scheduler import zone_manager
 
 
@@ -65,6 +66,11 @@ class FakeAbstractScheduler(abstract_scheduler.AbstractScheduler):
     pass
 
 
+class FakeBaseScheduler(base_scheduler.BaseScheduler):
+    # No need to stub anything at the moment
+    pass
+
+
 class FakeZoneManager(zone_manager.ZoneManager):
     def __init__(self):
         self.service_states = {
@@ -365,3 +371,30 @@ class AbstractSchedulerTestCase(test.TestCase):
 
         self.assertEqual(fixture._decrypt_blob(test_data),
                          json.dumps(test_data))
+
+
+class BaseSchedulerTestCase(test.TestCase):
+    """Test case for Base Scheduler."""
+
+    def test_weigh_hosts(self):
+        """
+        Try to weigh a short list of hosts and make sure enough
+        entries for a larger number instances are returned.
+        """
+
+        sched = FakeBaseScheduler()
+
+        # Fake out a list of hosts
+        zm = FakeZoneManager()
+        hostlist = [(host, services['compute'])
+                    for host, services in zm.service_states.items()
+                    if 'compute' in services]
+
+        # Call weigh_hosts()
+        num_instances = len(hostlist) * 2 + len(hostlist) / 2
+        instlist = sched.weigh_hosts('compute',
+                                     dict(num_instances=num_instances),
+                                     hostlist)
+
+        # Should be enough entries to cover all instances
+        self.assertEqual(len(instlist), num_instances)