openstack/swift
Code Issues Proposed changes

Respect device weights when adding replicas

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Previously, any new (partition, replica) pairs created by adding
replicas were spread evenly across the whole ring. Now it respects
device weights, so more (partition, replica) pairs are placed on
higher-weight devices.

Note that this only affects partition assignment *when the replica
count is increased*. Normal adding of disks without changing the
replica count is, and was, just fine.

The cause was that the devices' parts_wanted values weren't being
updated when the replica count went up. Since adding replicas makes
more things to assign, each device's desired share should have gone
up, but it didn't. This appears to be a simple oversight on the part
of the original author (me).

Change-Id: Idab14be90fab243c1077a584396a9981a4bd8638
This commit is contained in:
Samuel Merritt 2014-08-19 14:50:44 -07:00
parent 8eb8bb0a36
commit 8fecf490fe
2 changed files with 61 additions and 1 deletions
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4
swift/common/ring/builder.py
View File

@ -345,6 +345,8 @@ class RingBuilder(object):
last_balance = 0
new_parts, removed_part_count = self._adjust_replica2part2dev_size()
retval += removed_part_count
if new_parts or removed_part_count:
self._set_parts_wanted()
self._reassign_parts(new_parts)
retval += len(new_parts)
while True:
@ -584,7 +586,7 @@ class RingBuilder(object):
self._replica2part2dev.append(
array('H', (0 for _junk in xrange(desired_length))))
return (list(to_assign.iteritems()), removed_replicas)
return (to_assign.items(), removed_replicas)
def _initial_balance(self):
"""

58
test/unit/common/ring/test_builder.py
View File

@ -698,6 +698,64 @@ class TestRingBuilder(unittest.TestCase):
self.assertEqual([len(p2d) for p2d in rb._replica2part2dev],
[256, 256, 128])
def test_add_replicas_then_rebalance_respects_weight(self):
rb = ring.RingBuilder(8, 3, 1)
rb.add_dev({'id': 0, 'region': 0, 'region': 0, 'zone': 0, 'weight': 3,
'ip': '127.0.0.1', 'port': 10000, 'device': 'sda'})
rb.add_dev({'id': 1, 'region': 0, 'region': 0, 'zone': 0, 'weight': 3,
'ip': '127.0.0.1', 'port': 10000, 'device': 'sdb'})
rb.add_dev({'id': 2, 'region': 0, 'region': 0, 'zone': 0, 'weight': 1,
'ip': '127.0.0.1', 'port': 10000, 'device': 'sdc'})
rb.add_dev({'id': 3, 'region': 0, 'region': 0, 'zone': 0, 'weight': 1,
'ip': '127.0.0.1', 'port': 10000, 'device': 'sdd'})
rb.add_dev({'id': 4, 'region': 0, 'region': 0, 'zone': 1, 'weight': 3,
'ip': '127.0.0.1', 'port': 10000, 'device': 'sde'})
rb.add_dev({'id': 5, 'region': 0, 'region': 0, 'zone': 1, 'weight': 3,
'ip': '127.0.0.1', 'port': 10000, 'device': 'sdf'})
rb.add_dev({'id': 6, 'region': 0, 'region': 0, 'zone': 1, 'weight': 1,
'ip': '127.0.0.1', 'port': 10000, 'device': 'sdg'})
rb.add_dev({'id': 7, 'region': 0, 'region': 0, 'zone': 1, 'weight': 1,
'ip': '127.0.0.1', 'port': 10000, 'device': 'sdh'})
rb.add_dev({'id': 8, 'region': 0, 'region': 0, 'zone': 2, 'weight': 3,
'ip': '127.0.0.1', 'port': 10000, 'device': 'sdi'})
rb.add_dev({'id': 9, 'region': 0, 'region': 0, 'zone': 2, 'weight': 3,
'ip': '127.0.0.1', 'port': 10000, 'device': 'sdj'})
rb.add_dev({'id': 10, 'region': 0, 'region': 0, 'zone': 2, 'weight': 1,
'ip': '127.0.0.1', 'port': 10000, 'device': 'sdk'})
rb.add_dev({'id': 11, 'region': 0, 'region': 0, 'zone': 2, 'weight': 1,
'ip': '127.0.0.1', 'port': 10000, 'device': 'sdl'})
rb.rebalance(seed=1)
r = rb.get_ring()
counts = {}
for part2dev_id in r._replica2part2dev_id:
for dev_id in part2dev_id:
counts[dev_id] = counts.get(dev_id, 0) + 1
self.assertEquals(counts, {0: 96, 1: 96,
2: 32, 3: 32,
4: 96, 5: 96,
6: 32, 7: 32,
8: 96, 9: 96,
10: 32, 11: 32})
rb.replicas *= 2
rb.rebalance(seed=1)
r = rb.get_ring()
counts = {}
for part2dev_id in r._replica2part2dev_id:
for dev_id in part2dev_id:
counts[dev_id] = counts.get(dev_id, 0) + 1
self.assertEquals(counts, {0: 192, 1: 192,
2: 64, 3: 64,
4: 192, 5: 192,
6: 64, 7: 64,
8: 192, 9: 192,
10: 64, 11: 64})
def test_load(self):
rb = ring.RingBuilder(8, 3, 1)
devs = [{'id': 0, 'region': 0, 'zone': 0, 'weight': 1,