Improve scheduler performance when thin provisioning

The scheduler need to estimate the allocated capacity for thin
provisioning hosts. To do this more efficiently, use a sum fucntion in
query, instead of loading all share instances for a specific host.

manila/db/api.py

@@ -376,6 +376,11 @@ def share_instances_get_all_by_share_group_id(context, share_group_id):
         context, share_group_id)
 
 
+def share_instance_sizes_sum_by_host(context, host):
+    """Returns sum of sizes of all share instances on given host."""
+    return IMPL.share_instance_sizes_sum_by_host(context, host)
+
+
 def share_instance_purge(context, instance_id):
     """Removes share instance from database."""
     return IMPL.share_instance_purge(context, instance_id)

manila/db/sqlalchemy/api.py

@@ -1784,6 +1784,19 @@ def share_instances_get_all_by_host(context, host, with_share_data=False,
     return instances
 
 
+@require_context
+def share_instance_sizes_sum_by_host(context, host):
+    result = model_query(
+        context, models.Share, func.sum(models.Share.size),
+    ).join(
+        models.ShareInstance.share,
+    ).filter(or_(
+        models.ShareInstance.host == host,
+        models.ShareInstance.host.like("{0}#%".format(host)),
+    )).first()
+    return int(result[0] or 0)
+
+
 @require_context
 def share_instances_get_all_by_share_network(context, share_network_id):
     """Returns list of share instances that belong to given share network."""

manila/scheduler/host_manager.py

@@ -418,15 +418,7 @@ def __init__(self, host, capabilities, pool_name):
 
     def _estimate_provisioned_capacity(self, host_name, context=None):
         """Estimate provisioned capacity from share sizes on backend."""
-        provisioned_capacity = 0
-
-        instances = db.share_instances_get_all_by_host(
-            context, host_name, with_share_data=True)
-
-        for instance in instances:
-            # Size of share instance that's still being created, will be None.
-            provisioned_capacity += instance['size'] or 0
-        return provisioned_capacity
+        return db.share_instance_sizes_sum_by_host(context, host_name)
 
     def update_from_share_capability(
             self, capability, service=None, context=None):

manila/tests/scheduler/test_host_manager.py

@@ -1196,9 +1196,10 @@ class PoolStateTestCase(test.TestCase):
     @ddt.unpack
     def test_update_from_share_capability(self, share_capability, instances):
         fake_context = context.RequestContext('user', 'project', is_admin=True)
+        sizes = [instance['size'] or 0 for instance in instances]
         self.mock_object(
-            db, 'share_instances_get_all_by_host',
-            mock.Mock(return_value=instances))
+            db, 'share_instance_sizes_sum_by_host',
+            mock.Mock(return_value=sum(sizes)))
         fake_pool = host_manager.PoolState('host1', None, 'pool0')
         self.assertIsNone(fake_pool.free_capacity_gb)
 
@@ -1221,19 +1222,19 @@ def test_update_from_share_capability(self, share_capability, instances):
             self.assertEqual(thin_provisioned, fake_pool.thin_provisioning)
             if 'provisioned_capacity_gb' not in share_capability or (
                     share_capability['provisioned_capacity_gb'] is None):
-                db.share_instances_get_all_by_host.assert_called_once_with(
-                    fake_context, fake_pool.host, with_share_data=True)
+                db.share_instance_sizes_sum_by_host.assert_called_once_with(
+                    fake_context, fake_pool.host)
                 if len(instances) > 0:
                     self.assertEqual(4, fake_pool.provisioned_capacity_gb)
                 else:
                     self.assertEqual(0, fake_pool.provisioned_capacity_gb)
             else:
-                self.assertFalse(db.share_instances_get_all_by_host.called)
+                self.assertFalse(db.share_instance_sizes_sum_by_host.called)
                 self.assertEqual(share_capability['provisioned_capacity_gb'],
                                  fake_pool.provisioned_capacity_gb)
         else:
             self.assertFalse(fake_pool.thin_provisioning)
-            self.assertFalse(db.share_instances_get_all_by_host.called)
+            self.assertFalse(db.share_instance_sizes_sum_by_host.called)
             if 'provisioned_capacity_gb' not in share_capability or (
                     share_capability['provisioned_capacity_gb'] is None):
                 self.assertIsNone(fake_pool.provisioned_capacity_gb)