Revert volume consumed capacity when rescheduling

Cinder scheduler will consume pool capacity repeatedly
when rescheduling creating request.

Closes-Bug: #1741833
Change-Id: Ib11bda868085dfed0ab0e9018b8ed35956dbdf10

cinder/scheduler/filter_scheduler.py

@@ -316,6 +316,12 @@ class FilterScheduler(driver.Scheduler):
             resource_type['extra_specs'].update(
                 multiattach='<is> True')
 
+        # Revert volume consumed capacity if it's a rescheduled request
+        retry = filter_properties.get('retry', {})
+        if retry.get('backends', []):
+            self.host_manager.revert_volume_consumed_capacity(
+                retry['backends'][-1],
+                request_spec['volume_properties']['size'])
         # Find our local list of acceptable backends by filtering and
         # weighing our options. we virtually consume resources on
         # it so subsequent selections can adjust accordingly.

cinder/scheduler/host_manager.py

@@ -298,7 +298,7 @@ class BackendState(object):
         self.storage_protocol = capability.get('storage_protocol', None)
         self.updated = capability['timestamp']
 
-    def consume_from_volume(self, volume):
+    def consume_from_volume(self, volume, update_time=True):
         """Incrementally update host state from a volume."""
         volume_gb = volume['size']
         self.allocated_capacity_gb += volume_gb
@@ -311,7 +311,8 @@ class BackendState(object):
             pass
         else:
             self.free_capacity_gb -= volume_gb
-        self.updated = timeutils.utcnow()
+        if update_time:
+            self.updated = timeutils.utcnow()
 
     def __repr__(self):
         # FIXME(zhiteng) backend level free_capacity_gb isn't as
@@ -614,6 +615,14 @@ class HostManager(object):
                          "scheduler cache.", {'backend': backend_key})
             del self.backend_state_map[backend_key]
 
+    def revert_volume_consumed_capacity(self, pool_name, size):
+        for backend_key, state in self.backend_state_map.items():
+            for key in state.pools:
+                pool_state = state.pools[key]
+                if pool_name == '#'.join([backend_key, pool_state.pool_name]):
+                    pool_state.consume_from_volume({'size': -size},
+                                                   update_time=False)
+
     def get_all_backend_states(self, context):
         """Returns a dict of all the backends the HostManager knows about.
 

cinder/tests/unit/scheduler/test_filter_scheduler.py

@@ -311,6 +311,22 @@ class FilterSchedulerTestCase(test_scheduler.SchedulerTestCase):
                           self.context, request_spec,
                           filter_properties=filter_properties)
 
+    def test_retry_revert_consumed_capacity(self):
+        sched = fakes.FakeFilterScheduler()
+        request_spec = {'volume_type': {'name': 'LVM_iSCSI'},
+                        'volume_properties': {'project_id': 1,
+                                              'size': 2}}
+        request_spec = objects.RequestSpec.from_primitives(request_spec)
+        retry = dict(num_attempts=1, backends=['fake_backend_name'])
+        filter_properties = dict(retry=retry)
+
+        with mock.patch.object(
+                sched.host_manager,
+                'revert_volume_consumed_capacity') as mock_revert:
+            sched._schedule(self.context, request_spec,
+                            filter_properties=filter_properties)
+            mock_revert.assert_called_once_with('fake_backend_name', 2)
+
     def test_add_retry_backend(self):
         retry = dict(num_attempts=1, backends=[])
         filter_properties = dict(retry=retry)