openstack/swift
Code Issues Proposed changes

Unify different ring-balancing methods.

Browse Source 
RingBuilder._initial_balance() gathers partitions differently from
.rebalance(), but the assignment algorithm is the same. However, there
were two nearly-identical implementations; these have been combined.

Also extracted a couple of utility methods to reduce duplication.

Change-Id: Ia5442782a8285dc14aa9a93878a7b0e8d1bb1be5
This commit is contained in:
Samuel Merritt 2012-03-29 22:40:14 -07:00
parent 0becfab629
commit ca6d418fa5
1 changed files with 26 additions and 50 deletions
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76
swift/common/ring/builder.py
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@ -391,46 +391,17 @@ class RingBuilder(object):
def _initial_balance(self):
"""
Initial partition assignment is treated separately from rebalancing an
existing ring. Initial assignment is performed by ordering all the
devices by how many partitions they still want (and kept in order
during the process). The partitions are then iterated through,
assigning them to the next "most wanted" device, with distinct zone
restrictions.
Initial partition assignment is the same as rebalancing an
existing ring, but with some initial setup beforehand.
"""
for dev in self._iter_devs():
dev['sort_key'] = \
'%08x.%04x' % (dev['parts_wanted'], randint(0, 0xffff))
available_devs = sorted((d for d in self._iter_devs()),
key=lambda x: x['sort_key'])
self._replica2part2dev = \
[array('H') for _junk in xrange(self.replicas)]
for _junk in xrange(self.parts):
other_zones = array('H')
for replica in xrange(self.replicas):
index = len(available_devs) - 1
while available_devs[index]['zone'] in other_zones:
index -= 1
dev = available_devs.pop(index)
self._replica2part2dev[replica].append(dev['id'])
dev['parts_wanted'] -= 1
dev['parts'] += 1
dev['sort_key'] = \
'%08x.%04x' % (dev['parts_wanted'], randint(0, 0xffff))
index = 0
end = len(available_devs)
while index < end:
mid = (index + end) // 2
if dev['sort_key'] < available_devs[mid]['sort_key']:
end = mid
else:
index = mid + 1
available_devs.insert(index, dev)
other_zones.append(dev['zone'])
[array('H', (0 for _junk in xrange(self.parts)))
for _junk in xrange(self.replicas)]
replicas = range(self.replicas)
self._last_part_moves = array('B', (0 for _junk in xrange(self.parts)))
self._last_part_moves_epoch = int(time())
for dev in self._iter_devs():
del dev['sort_key']
self._reassign_parts((p, replicas) for p in xrange(self.parts))
def _update_last_part_moves(self):
"""
@ -493,8 +464,7 @@ class RingBuilder(object):
according to the "most wanted" and distinct zone restrictions.
"""
for dev in self._iter_devs():
dev['sort_key'] = '%08x.%04x' % (self.parts +
dev['parts_wanted'], randint(0, 0xffff))
dev['sort_key'] = self._sort_key_for(dev)
available_devs = \
sorted((d for d in self._iter_devs() if d['weight']),
key=lambda x: x['sort_key'])
@ -518,17 +488,23 @@ class RingBuilder(object):
self._replica2part2dev[replica][part] = dev['id']
dev['parts_wanted'] -= 1
dev['parts'] += 1
dev['sort_key'] = \
'%08x.%04x' % (self.parts + dev['parts_wanted'],
randint(0, 0xffff))
index = 0
end = len(available_devs)
while index < end:
mid = (index + end) // 2
if dev['sort_key'] < available_devs[mid]['sort_key']:
end = mid
else:
index = mid + 1
available_devs.insert(index, dev)
dev['sort_key'] = self._sort_key_for(dev)
self._insert_dev_sorted(available_devs, dev)
for dev in self._iter_devs():
del dev['sort_key']
def _insert_dev_sorted(self, devs, dev):
index = 0
end = len(devs)
while index < end:
mid = (index + end) // 2
if dev['sort_key'] < devs[mid]['sort_key']:
end = mid
else:
index = mid + 1
devs.insert(index, dev)
def _sort_key_for(self, dev):
return '%08x.%04x' % (self.parts + dev['parts_wanted'],
randint(0, 0xffff))