Ensure storage hooks observe disable-ring-rebalance

When adding new storage capacity, its desirable to disable ring
rebalancing until all new storage has been added, allowing the
end-user to determing when all new capacity has been added and its
OK to rebalance the rings and re-distribute.

Ensure that storage hook events from swift-storage observe the
'disable-ring-rebalance' configuration option, enabling end users
to perform this type of orchestration storage expansion.

Change-Id: I95727e663b369d5feb28147b19edcc6cab36b905
Closes-Bug: 1638981

hooks/swift_hooks.py

@@ -171,7 +171,8 @@ def config_changed():
         status_set('maintenance', 'Running openstack upgrade')
 
     status_set('maintenance', 'Updating and (maybe) balancing rings')
-    update_rings(min_part_hours=config('min-hours'))
+    update_rings(min_part_hours=config('min-hours'),
+                 rebalance=not config('disable-ring-balance'))
 
     if not config('disable-ring-balance') and is_elected_leader(SWIFT_HA_RES):
         # Try ring balance. If rings are balanced, no sync will occur.
@@ -324,7 +325,11 @@ def storage_changed():
             node['device'] = dev
             nodes.append(node)
 
-    update_rings(nodes)
+    # NOTE(jamespage): ensure that disable-ring-balance is observed
+    #                  whilst new storage is added - rebalance will
+    #                  happen when configuration is toggled later
+    update_rings(nodes, rebalance=not config('disable-ring-balance'))
+
     if not openstack.is_unit_paused_set():
         # Restart proxy here in case no config changes made (so
         # restart_on_change() ineffective).

lib/swift_utils.py

@@ -861,7 +861,7 @@ def sync_builders_and_rings_if_changed(f):
 
 
 @sync_builders_and_rings_if_changed
-def update_rings(nodes=[], min_part_hours=None):
+def update_rings(nodes=[], min_part_hours=None, rebalance=True):
     """Update builder with node settings and balance rings if necessary.
 
     Also update min_part_hours if provided.
@@ -899,7 +899,7 @@ def update_rings(nodes=[], min_part_hours=None):
                 add_to_ring(ring, node)
                 balance_required = True
 
-    if balance_required:
+    if rebalance and balance_required:
         balance_rings()
 
 

unit_tests/test_swift_utils.py

@@ -90,6 +90,13 @@ class SwiftUtilsTestCase(unittest.TestCase):
         self.assertTrue(mock_set_min_hours.called)
         self.assertTrue(mock_balance_rings.called)
 
+        mock_balance_rings.reset_mock()
+        swift_utils.update_rings(min_part_hours=10,
+                                 rebalance=False)
+        self.assertTrue(mock_get_min_hours.called)
+        self.assertTrue(mock_set_min_hours.called)
+        self.assertFalse(mock_balance_rings.called)
+
     @mock.patch('lib.swift_utils.previously_synced')
     @mock.patch('lib.swift_utils._load_builder')
     @mock.patch('lib.swift_utils.initialize_ring')