Make HostManager.get_all_host_states() return an iterator

Change the method's returning from a dictionary {host: HostState}
to an iterator for HostState, because the only caller of the method
(in filter_scheduler.py) is not interested in its key.

Change-Id: I84f649795a422e392a4c0d555c6cb29a01fae2d9

nova/scheduler/filter_scheduler.py

@@ -257,14 +257,11 @@ class FilterScheduler(driver.Scheduler):
         # host, we virtually consume resources on it so subsequent
         # selections can adjust accordingly.
 
-        # unfiltered_hosts_dict is {host : ZoneManager.HostInfo()}
-        unfiltered_hosts_dict = self.host_manager.get_all_host_states(
-                elevated, topic)
-
         # Note: remember, we are using an iterator here. So only
         # traverse this list once. This can bite you if the hosts
         # are being scanned in a filter or weighing function.
-        hosts = unfiltered_hosts_dict.itervalues()
+        hosts = self.host_manager.get_all_host_states(
+                elevated, topic)
 
         selected_hosts = []
         if instance_uuids:

nova/scheduler/host_manager.py

@@ -336,12 +336,9 @@ class HostManager(object):
         self.service_states[host] = service_caps
 
     def get_all_host_states(self, context, topic):
-        """Returns a dict of all the hosts the HostManager
-        knows about. Also, each of the consumable resources in HostState
-        are pre-populated and adjusted based on data in the db.
-
-        For example:
-        {'192.168.1.100': HostState(), ...}
+        """Returns a list of HostStates that represents all the hosts
+        the HostManager knows about. Also, each of the consumable resources
+        in HostState are pre-populated and adjusted based on data in the db.
 
         Note: this can be very slow with a lot of instances.
         InstanceType table isn't required since a copy is stored
@@ -372,4 +369,4 @@ class HostManager(object):
                 self.host_state_map[host] = host_state
             host_state.update_from_compute_node(compute)
 
-        return self.host_state_map
+        return self.host_state_map.itervalues()

nova/tests/scheduler/test_host_manager.py

@@ -136,27 +136,28 @@ class HostManagerTestCase(test.TestCase):
         host_manager.LOG.warn("No service for compute ID 5")
 
         self.mox.ReplayAll()
-        host_states = self.host_manager.get_all_host_states(context, topic)
+        self.host_manager.get_all_host_states(context, topic)
+        host_states_map = self.host_manager.host_state_map
 
-        self.assertEqual(len(host_states), 4)
+        self.assertEqual(len(host_states_map), 4)
         # Check that .service is set properly
         for i in xrange(4):
             compute_node = fakes.COMPUTE_NODES[i]
             host = compute_node['service']['host']
-            self.assertEqual(host_states[host].service,
+            self.assertEqual(host_states_map[host].service,
                     compute_node['service'])
-        self.assertEqual(host_states['host1'].free_ram_mb, 512)
+        self.assertEqual(host_states_map['host1'].free_ram_mb, 512)
         # 511GB
-        self.assertEqual(host_states['host1'].free_disk_mb, 524288)
-        self.assertEqual(host_states['host2'].free_ram_mb, 1024)
+        self.assertEqual(host_states_map['host1'].free_disk_mb, 524288)
+        self.assertEqual(host_states_map['host2'].free_ram_mb, 1024)
         # 1023GB
-        self.assertEqual(host_states['host2'].free_disk_mb, 1048576)
-        self.assertEqual(host_states['host3'].free_ram_mb, 3072)
+        self.assertEqual(host_states_map['host2'].free_disk_mb, 1048576)
+        self.assertEqual(host_states_map['host3'].free_ram_mb, 3072)
         # 3071GB
-        self.assertEqual(host_states['host3'].free_disk_mb, 3145728)
-        self.assertEqual(host_states['host4'].free_ram_mb, 8192)
+        self.assertEqual(host_states_map['host3'].free_disk_mb, 3145728)
+        self.assertEqual(host_states_map['host4'].free_ram_mb, 8192)
         # 8191GB
-        self.assertEqual(host_states['host4'].free_disk_mb, 8388608)
+        self.assertEqual(host_states_map['host4'].free_disk_mb, 8388608)
 
 
 class HostStateTestCase(test.TestCase):

nova/tests/scheduler/test_least_cost.py

@@ -41,7 +41,7 @@ class LeastCostTestCase(test.TestCase):
         fakes.mox_host_manager_db_calls(self.mox, ctxt)
         self.mox.ReplayAll()
         host_states = self.host_manager.get_all_host_states(ctxt,
-                'compute').values()
+                'compute')
         self.mox.VerifyAll()
         self.mox.ResetAll()
         return host_states