Respect co-builder partition moves when min_part_hours is zero

Repeated calls to each co-builder's _update_last_part_moves() are
unnecessary and have the unfortunate side effect of resetting the
_last_part_moved bitmap. When a component builder has zero
min_part_hours this results in it not preventing its co-builders from
moving parts that it has already moved.

This patch changes the CompositeRingBuilder to call each component
builder _update_last_part_moves() *once* before rebalancing any
component builder. CooperativeRingBuilder's no longer forward calls to
their _update_last_part_moves() method. Each component's
_last_part_moved bitmap is therefore preserved until for the duration
of the composite rebalance.

The initialisation of the RingBuilder _last_part_moves array is moved
to the RingBuilder __init__ method, so that calls to
_update_last_part_moves() are effective even when rebalance() has
never been called on that builder. Otherwise, during a composite
rebalance, a component that has not previously been rebalanced will
not have its _last_part_moves_epoch updated during rebalance and as a
result may report erroneous min_part_seconds_left after its first
rebalance.

Related-Change: I1b30cb3d776be441346a4131007d2487a5440a81
Closes-Bug: #1714274
Change-Id: Ib165cf974c865d47c2d9e8f7b3641971d2e9f404

swift/common/ring/builder.py

@@ -130,7 +130,7 @@ class RingBuilder(object):
         # within a given number of hours (24 is my usual test). Removing
         # a device overrides this behavior as it's assumed that's only
         # done because of device failure.
-        self._last_part_moves = None
+        self._last_part_moves = array('B', itertools.repeat(0, self.parts))
         # _part_moved_bitmap record parts have been moved
         self._part_moved_bitmap = None
         # _last_part_moves_epoch indicates the time the offsets in
@@ -167,7 +167,7 @@ class RingBuilder(object):
 
     @property
     def ever_rebalanced(self):
-        return self._last_part_moves is not None
+        return self._replica2part2dev is not None
 
     def _set_part_moved(self, part):
         self._last_part_moves[part] = 0
@@ -507,7 +507,7 @@ class RingBuilder(object):
 
         if not self.ever_rebalanced:
             self.logger.debug("New builder; performing initial balance")
-            self._last_part_moves = array('B', itertools.repeat(0, self.parts))
+
         self._update_last_part_moves()
 
         with _set_random_seed(seed):
@@ -925,7 +925,7 @@ class RingBuilder(object):
         """
         self._part_moved_bitmap = bytearray(max(2 ** (self.part_power - 3), 1))
         elapsed_hours = int(time() - self._last_part_moves_epoch) / 3600
-        if elapsed_hours <= 0 or not self._last_part_moves:
+        if elapsed_hours <= 0:
             return
         for part in range(self.parts):
             # The "min(self._last_part_moves[part] + elapsed_hours, 0xff)"

swift/common/ring/composite_builder.py

@@ -639,6 +639,7 @@ class CompositeRingBuilder(object):
             component builder.
         """
         self._load_components()
+        self.update_last_part_moves()
         component_builders = zip(self._builder_files, self._builders)
         # don't let the same builder go first each time
         shuffle(component_builders)
@@ -678,10 +679,10 @@ class CompositeRingBuilder(object):
         Updates the record of how many hours ago each partition was moved in
         all component builders.
         """
-        # Called by component builders. We need all component builders to be at
-        # same last_part_moves epoch before any builder starts moving parts;
-        # this will effectively be a no-op for builders that have already been
-        # updated in last hour
+        # Called at start of each composite rebalance. We need all component
+        # builders to be at same last_part_moves epoch before any builder
+        # starts moving parts; this will effectively be a no-op for builders
+        # that have already been updated in last hour
         for b in self._builders:
             b.update_last_part_moves()
 
@@ -723,8 +724,11 @@ class CooperativeRingBuilder(RingBuilder):
                 super(CooperativeRingBuilder, self)._can_part_move(part))
 
     def _update_last_part_moves(self):
-        # overrides superclass method to delegate to parent builder
-        return self.parent_builder.update_last_part_moves()
+        # overrides superclass method - parent builder should have called
+        # update_last_part_moves() before rebalance; calling the superclass
+        # method here would reset _part_moved_bitmap which is state we rely on
+        # when min_part_hours is zero
+        pass
 
     def update_last_part_moves(self):
         """

test/unit/common/ring/test_builder.py

@@ -69,6 +69,7 @@ class TestRingBuilder(unittest.TestCase):
         self.assertEqual(rb.devs, [])
         self.assertFalse(rb.devs_changed)
         self.assertEqual(rb.version, 0)
+        self.assertIsNotNone(rb._last_part_moves)
 
     def test_overlarge_part_powers(self):
         expected_msg = 'part_power must be at most 32 (was 33)'
@@ -841,6 +842,25 @@ class TestRingBuilder(unittest.TestCase):
         }
         self.assertEqual(parts_with_moved_count, expected)
 
+    def test_ever_rebalanced(self):
+        rb = ring.RingBuilder(8, 3, 1)
+        rb.add_dev({'id': 0, 'region': 0, 'zone': 0, 'weight': 1,
+                    'ip': '127.0.0.1', 'port': 10000, 'device': 'sda1'})
+        rb.add_dev({'id': 1, 'region': 0, 'zone': 1, 'weight': 1,
+                    'ip': '127.0.0.1', 'port': 10001, 'device': 'sda1'})
+        rb.add_dev({'id': 2, 'region': 0, 'zone': 2, 'weight': 1,
+                    'ip': '127.0.0.1', 'port': 10002, 'device': 'sda1'})
+        self.assertFalse(rb.ever_rebalanced)
+        builder_file = os.path.join(self.testdir, 'test.buider')
+        rb.save(builder_file)
+        rb = ring.RingBuilder.load(builder_file)
+        self.assertFalse(rb.ever_rebalanced)
+        rb.rebalance()
+        self.assertTrue(rb.ever_rebalanced)
+        rb.save(builder_file)
+        rb = ring.RingBuilder.load(builder_file)
+        self.assertTrue(rb.ever_rebalanced)
+
     def test_rerebalance(self):
         rb = ring.RingBuilder(8, 3, 1)
         rb.add_dev({'id': 0, 'region': 0, 'zone': 0, 'weight': 1,
@@ -849,13 +869,16 @@ class TestRingBuilder(unittest.TestCase):
                     'ip': '127.0.0.1', 'port': 10001, 'device': 'sda1'})
         rb.add_dev({'id': 2, 'region': 0, 'zone': 2, 'weight': 1,
                     'ip': '127.0.0.1', 'port': 10002, 'device': 'sda1'})
+        self.assertFalse(rb.ever_rebalanced)
         rb.rebalance()
+        self.assertTrue(rb.ever_rebalanced)
         counts = self._partition_counts(rb)
         self.assertEqual(counts, {0: 256, 1: 256, 2: 256})
         rb.add_dev({'id': 3, 'region': 0, 'zone': 3, 'weight': 1,
                     'ip': '127.0.0.1', 'port': 10003, 'device': 'sda1'})
         rb.pretend_min_part_hours_passed()
         rb.rebalance()
+        self.assertTrue(rb.ever_rebalanced)
         counts = self._partition_counts(rb)
         self.assertEqual(counts, {0: 192, 1: 192, 2: 192, 3: 192})
         rb.set_dev_weight(3, 100)

test/unit/common/ring/test_composite_builder.py

@@ -22,6 +22,7 @@ import tempfile
 import unittest
 import shutil
 import copy
+import time
 
 from collections import defaultdict, Counter
 
@@ -965,8 +966,9 @@ class TestComposeLoadComponents(TestLoadComponents):
 
 
 class TestCooperativeRingBuilder(BaseTestCompositeBuilder):
-    def _make_coop_builder(self, region, composite_builder, rebalance=False):
-        rb = CooperativeRingBuilder(8, 3, 1, composite_builder)
+    def _make_coop_builder(self, region, composite_builder, rebalance=False,
+                           min_part_hours=1):
+        rb = CooperativeRingBuilder(8, 3, min_part_hours, composite_builder)
         if composite_builder._builders is None:
             composite_builder._builders = [rb]
         for i in range(3):
@@ -986,93 +988,231 @@ class TestCooperativeRingBuilder(BaseTestCompositeBuilder):
                        for part2dev_id in builder._replica2part2dev
                        for dev_id in part2dev_id)
 
+    def get_moved_parts(self, after, before):
+        def uniqueness(dev):
+            return dev['ip'], dev['port'], dev['device']
+        moved_parts = set()
+        for p in range(before.parts):
+            if ({uniqueness(dev) for dev in before._devs_for_part(p)} !=
+                    {uniqueness(dev) for dev in after._devs_for_part(p)}):
+                    moved_parts.add(p)
+        return moved_parts
+
+    def num_parts_can_move(self, builder):
+        # note that can_part_move() gives consideration to the
+        # _part_moved_bitmap which is only reset when a rebalance starts
+        return len(
+            [p for p in range(builder.parts)
+             if super(CooperativeRingBuilder, builder)._can_part_move(p)])
+
     @mock.patch('swift.common.ring.builder.time')
-    def test_rebalance_respects_cobuilder_part_moves(self, mock_time):
-        def do_rebalance(builder):
-            old_part_devs = [builder._devs_for_part(part)
-                             for part in range(builder.parts)]
-            num_moved, _, _ = builder.rebalance()
-            moved_parts = {
-                p for p in range(builder.parts)
-                if old_part_devs[p] != builder._devs_for_part(p)}
-            self.assertEqual(len(moved_parts), num_moved)  # sanity check
-            return num_moved, moved_parts
-
-        def num_parts_can_move(builder):
-            # note that can_part_move() gives consideration to the
-            # _part_moved_bitmap which is only reset when a rebalance starts
-            return len(
-                [p for p in range(builder.parts)
-                 if super(CooperativeRingBuilder, builder)._can_part_move(p)])
-
-        mock_time.return_value = 0
+    def _check_rebalance_respects_cobuilder_part_moves(
+            self, min_part_hours, mock_time):
+        mock_time.return_value = now = int(time.time())
+        builder_files = []
         cb = CompositeRingBuilder()
-        rb1 = self._make_coop_builder(1, cb)
-        rb2 = self._make_coop_builder(2, cb)
-        rb3 = self._make_coop_builder(3, cb)
-        cb._builders = [rb1, rb2, rb3]
+        for i in (1, 2, 3):
+            b = self._make_coop_builder(i, cb, min_part_hours=min_part_hours)
+            fname = os.path.join(self.tmpdir, 'builder_%s.builder' % i)
+            b.save(fname)
+            builder_files.append(fname)
+        builder_files, builders = cb.load_components(builder_files)
 
         # all cobuilders can perform initial rebalance
-        for rb in (rb1, rb2, rb3):
-            rb.rebalance()
-            actual = self._partition_counts(rb)
-            exp = {0: 256, 1: 256, 2: 256}
-            self.assertEqual(exp, actual,
-                             'Expected %s but got %s for region %s' %
-                             (exp, actual, next(rb._iter_devs())['region']))
-
-        # jump forwards min_part_hours, both builders can move all parts
-        mock_time.return_value = 3600
-        self.add_dev(rb1)
-        # sanity checks: rb1 and rb2 are both ready for rebalance
-        self.assertEqual(0, rb2.min_part_seconds_left)
-        self.assertEqual(0, rb1.min_part_seconds_left)
+        cb.rebalance()
+        exp = {0: 256, 1: 256, 2: 256}
+        self.assertEqual(exp, self._partition_counts(builders[0]))
+        self.assertEqual(exp, self._partition_counts(builders[1]))
+        self.assertEqual(exp, self._partition_counts(builders[2]))
+        exp = min_part_hours * 3600
+        self.assertEqual(exp, builders[0].min_part_seconds_left)
+        self.assertEqual(exp, builders[1].min_part_seconds_left)
+        self.assertEqual(exp, builders[2].min_part_seconds_left)
+
+        # jump forwards min_part_hours
+        now += min_part_hours * 3600
+        mock_time.return_value = now
+        old_builders = []
+        for builder in builders:
+            old_builder = CooperativeRingBuilder(8, 3, min_part_hours, None)
+            old_builder.copy_from(copy.deepcopy(builder.to_dict()))
+            old_builders.append(old_builder)
+
+        for builder in builders:
+            self.add_dev(builder)
+        # sanity checks: all builders are ready for rebalance
+        self.assertEqual(0, builders[0].min_part_seconds_left)
+        self.assertEqual(0, builders[1].min_part_seconds_left)
+        self.assertEqual(0, builders[2].min_part_seconds_left)
         # ... but last_part_moves not yet updated to current epoch
-        self.assertEqual(0, num_parts_can_move(rb1))
-        self.assertEqual(0, num_parts_can_move(rb2))
-        # rebalancing rb1 will update epoch for both builders' last_part_moves
-        num_moved, rb1_parts_moved = do_rebalance(rb1)
-        self.assertEqual(192, num_moved)
-        self.assertEqual(self._partition_counts(rb1),
+        if min_part_hours > 0:
+            self.assertEqual(0, self.num_parts_can_move(builders[0]))
+            self.assertEqual(0, self.num_parts_can_move(builders[1]))
+            self.assertEqual(0, self.num_parts_can_move(builders[2]))
+
+        with mock.patch('swift.common.ring.composite_builder.shuffle',
+                        lambda x: x):
+            cb.rebalance()
+
+        rb1_parts_moved = self.get_moved_parts(builders[0], old_builders[0])
+        self.assertEqual(192, len(rb1_parts_moved))
+        self.assertEqual(self._partition_counts(builders[0]),
                          {0: 192, 1: 192, 2: 192, 3: 192})
+
+        rb2_parts_moved = self.get_moved_parts(builders[1], old_builders[1])
+        self.assertEqual(64, len(rb2_parts_moved))
+        counts = self._partition_counts(builders[1])
+        self.assertEqual(counts[3], 64)
+        self.assertEqual([234, 235, 235], sorted(counts.values()[:3]))
+        self.assertFalse(rb2_parts_moved.intersection(rb1_parts_moved))
+
+        # rb3 can't rebalance - all parts moved while rebalancing rb1 and rb2
+        self.assertEqual(
+            0, len(self.get_moved_parts(builders[2], old_builders[2])))
+
+        # jump forwards min_part_hours, all builders can move all parts again,
+        # so now rb2 should be able to further rebalance
+        now += min_part_hours * 3600
+        mock_time.return_value = now
+        old_builders = []
+        for builder in builders:
+            old_builder = CooperativeRingBuilder(8, 3, min_part_hours, None)
+            old_builder.copy_from(copy.deepcopy(builder.to_dict()))
+            old_builders.append(old_builder)
+        with mock.patch('swift.common.ring.composite_builder.shuffle',
+                        lambda x: x):
+            cb.rebalance()
+
+        rb2_parts_moved = self.get_moved_parts(builders[1], old_builders[1])
+        self.assertGreater(len(rb2_parts_moved), 64)
+        self.assertGreater(self._partition_counts(builders[1])[3], 64)
+        self.assertLess(self.num_parts_can_move(builders[2]), 256)
+        self.assertEqual(256, self.num_parts_can_move(builders[0]))
+        # and rb3 should also have been able to move some parts
+        rb3_parts_moved = self.get_moved_parts(builders[2], old_builders[2])
+        self.assertGreater(len(rb3_parts_moved), 0)
+        self.assertFalse(rb3_parts_moved.intersection(rb2_parts_moved))
+
+        # but cobuilders will not prevent a new rb rebalancing for first time
+        rb4 = self._make_coop_builder(4, cb, rebalance=False,
+                                      min_part_hours=min_part_hours)
+        builders.append(rb4)
+        builder_files = []
+        for i, builder in enumerate(builders):
+            fname = os.path.join(self.tmpdir, 'builder_%s.builder' % i)
+            builder.save(fname)
+            builder_files.append(fname)
+        cb = CompositeRingBuilder()
+        builder_files, builders = cb.load_components(builder_files)
+        cb.rebalance()
+        self.assertEqual(256, len(self.get_moved_parts(builders[3], rb4)))
+
+    def test_rebalance_respects_cobuilder_part_moves(self):
+        self._check_rebalance_respects_cobuilder_part_moves(1)
+        self._check_rebalance_respects_cobuilder_part_moves(0)
+
+    @mock.patch('swift.common.ring.builder.time')
+    def _check_rebalance_cobuilder_states(
+            self, min_part_hours, mock_time):
+
+        @contextmanager
+        def mock_rebalance():
+            # wrap rebalance() in order to capture builder states before and
+            # after each component rebalance
+            orig_rebalance = RingBuilder.rebalance
+            # a dict mapping builder -> (list of captured builder states)
+            captured_builder_states = defaultdict(list)
+
+            def update_states():
+                for b in cb._builders:
+                    rb = CooperativeRingBuilder(8, 3, min_part_hours, None)
+                    rb.copy_from(copy.deepcopy(b.to_dict()))
+                    rb._part_moved_bitmap = bytearray(b._part_moved_bitmap)
+                    captured_builder_states[b].append(rb)
+
+            def wrap_rebalance(builder_instance):
+                update_states()
+                results = orig_rebalance(builder_instance)
+                update_states()
+                return results
+
+            with mock.patch('swift.common.ring.RingBuilder.rebalance',
+                            wrap_rebalance):
+                yield captured_builder_states
+
+        mock_time.return_value = now = int(time.time())
+        builder_files = []
+        cb = CompositeRingBuilder()
+        for i in (1, 2, 3):
+            b = self._make_coop_builder(i, cb, min_part_hours=min_part_hours)
+            fname = os.path.join(self.tmpdir, 'builder_%s.builder' % i)
+            b.save(fname)
+            builder_files.append(fname)
+        builder_files, builders = cb.load_components(builder_files)
+
+        # all cobuilders can perform initial rebalance
+        cb.rebalance()
+        # jump forwards min_part_hours
+        now += min_part_hours * 3600
+        mock_time.return_value = now
+        for builder in builders:
+            self.add_dev(builder)
+
+        with mock.patch('swift.common.ring.composite_builder.shuffle',
+                        lambda x: x):
+            with mock_rebalance() as captured_states:
+                cb.rebalance()
+
+        # sanity - state captured before and after each component rebalance
+        self.assertEqual(len(builders), len(captured_states))
+        for states in captured_states.values():
+            self.assertEqual(2 * len(builders), len(states))
+        # for each component we have a list of it's builder states
+        rb1s = captured_states[builders[0]]
+        rb2s = captured_states[builders[1]]
+        rb3s = captured_states[builders[2]]
+
+        # rebalancing will update epoch for all builders' last_part_moves
+        self.assertEqual(now, rb1s[0]._last_part_moves_epoch)
+        self.assertEqual(now, rb2s[0]._last_part_moves_epoch)
+        self.assertEqual(now, rb3s[0]._last_part_moves_epoch)
+        # so, in state before any component rebalance, all can now move parts
         # N.B. num_parts_can_move gathers super class's (i.e. RingBuilder)
-        # _can_part_move so that it doesn't refer cobuilders state.
-        self.assertEqual(256, num_parts_can_move(rb2))
-        self.assertEqual(64, num_parts_can_move(rb1))
+        # _can_part_move so that it doesn't refer to cobuilders state.
+        self.assertEqual(256, self.num_parts_can_move(rb1s[0]))
+        self.assertEqual(256, self.num_parts_can_move(rb2s[0]))
+        self.assertEqual(256, self.num_parts_can_move(rb3s[0]))
+
+        # after first component has been rebalanced it has moved parts
+        self.assertEqual(64, self.num_parts_can_move(rb1s[1]))
+        self.assertEqual(256, self.num_parts_can_move(rb2s[2]))
+        self.assertEqual(256, self.num_parts_can_move(rb3s[2]))
+
+        rb1_parts_moved = self.get_moved_parts(rb1s[1], rb1s[0])
+        self.assertEqual(192, len(rb1_parts_moved))
+        self.assertEqual(self._partition_counts(rb1s[1]),
+                         {0: 192, 1: 192, 2: 192, 3: 192})
 
         # rebalancing rb2 - rb2 in isolation could potentially move all parts
         # so would move 192 parts to new device, but it is constrained by rb1
         # only having 64 parts that can move
-        self.add_dev(rb2)
-        num_moved, rb2_parts_moved = do_rebalance(rb2)
-        self.assertEqual(64, num_moved)
-        counts = self._partition_counts(rb2)
+        rb2_parts_moved = self.get_moved_parts(rb2s[3], rb2s[2])
+        self.assertEqual(64, len(rb2_parts_moved))
+        counts = self._partition_counts(rb2s[3])
         self.assertEqual(counts[3], 64)
         self.assertEqual([234, 235, 235], sorted(counts.values()[:3]))
         self.assertFalse(rb2_parts_moved.intersection(rb1_parts_moved))
-        self.assertEqual(192, num_parts_can_move(rb2))
-        self.assertEqual(64, num_parts_can_move(rb1))
+        self.assertEqual(192, self.num_parts_can_move(rb2s[3]))
+        self.assertEqual(64, self.num_parts_can_move(rb1s[3]))
 
         # rb3 can't rebalance - all parts moved while rebalancing rb1 and rb2
-        self.add_dev(rb3)
-        num_moved, rb3_parts_moved = do_rebalance(rb3)
-        self.assertEqual(0, num_moved)
+        self.assertEqual(0, len(self.get_moved_parts(rb3s[5], rb3s[0])))
 
-        # jump forwards min_part_hours, both builders can move all parts again,
-        # so now rb2 should be able to further rebalance
-        mock_time.return_value = 7200
-        do_rebalance(rb2)
-        self.assertGreater(self._partition_counts(rb2)[3], 64)
-        self.assertLess(num_parts_can_move(rb2), 256)
-        self.assertEqual(256, num_parts_can_move(rb1))  # sanity check
-
-        # but cobuilders will not prevent a rb rebalancing for first time
-        rb4 = self._make_coop_builder(4, cb, rebalance=False)
-        cb._builders.append(rb4)
-        num_moved, _, _ = rb4.rebalance()
-        self.assertEqual(3 * 256, num_moved)
-
-    def test_rebalance_cobuilders(self):
+    def test_rebalance_cobuilder_states(self):
+        self._check_rebalance_cobuilder_states(1)
+        self._check_rebalance_cobuilder_states(0)
+
+    def _check_rebalance_cobuilders_calls(self, min_part_hours):
         # verify that co-builder methods are called during one builder's
         # rebalance
         @contextmanager
@@ -1107,26 +1247,20 @@ class TestCooperativeRingBuilder(BaseTestCompositeBuilder):
                             fake_can_part_move):
                 yield calls
 
-        # single component builder in parent builder
         cb = CompositeRingBuilder()
-        rb1 = self._make_coop_builder(1, cb)
+        rb1 = self._make_coop_builder(1, cb, min_part_hours=min_part_hours)
+        rb2 = self._make_coop_builder(2, cb, min_part_hours=min_part_hours)
+        cb._builders = [rb1, rb2]
+        # composite rebalance updates last_part_moves before any component
+        # rebalance - after that expect no more updates
         with mock_update_last_part_moves() as update_calls:
-            with mock_can_part_move() as can_part_move_calls:
-                rb1.rebalance()
-        self.assertEqual([rb1], update_calls)
-        self.assertEqual([rb1], can_part_move_calls.keys())
-        self.assertEqual(768, len(can_part_move_calls[rb1]))
+            cb.update_last_part_moves()
+        self.assertEqual(sorted([rb1, rb2]), sorted(update_calls))
 
-        # two component builders with same parent builder
-        cb = CompositeRingBuilder()
-        rb1 = self._make_coop_builder(1, cb)
-        rb2 = self._make_coop_builder(2, cb)
-        cb._builders = [rb1, rb2]
         with mock_update_last_part_moves() as update_calls:
             with mock_can_part_move() as can_part_move_calls:
                 rb2.rebalance()
-        # both builders get updated
-        self.assertEqual(sorted([rb1, rb2]), sorted(update_calls))
+        self.assertFalse(update_calls)
         # rb1 has never been rebalanced so no calls propagate from its
         # can_part_move method to to its superclass _can_part_move method
         self.assertEqual([rb2], can_part_move_calls.keys())
@@ -1134,14 +1268,16 @@ class TestCooperativeRingBuilder(BaseTestCompositeBuilder):
         with mock_update_last_part_moves() as update_calls:
             with mock_can_part_move() as can_part_move_calls:
                 rb1.rebalance()
-        # both builders get updated
-        self.assertEqual(sorted([rb1, rb2]), sorted(update_calls))
-
+        self.assertFalse(update_calls)
         # rb1 is being rebalanced so gets checked, and rb2 also gets checked
         self.assertEqual(sorted([rb1, rb2]), sorted(can_part_move_calls))
         self.assertEqual(768, len(can_part_move_calls[rb1]))
         self.assertEqual(768, len(can_part_move_calls[rb2]))
 
+    def test_rebalance_cobuilders_calls(self):
+        self._check_rebalance_cobuilders_calls(1)
+        self._check_rebalance_cobuilders_calls(0)
+
     def test_save_then_load(self):
         cb = CompositeRingBuilder()
         coop_rb = self._make_coop_builder(1, cb, rebalance=True)