Recreating Openstack Swift Builder files

August 08, 2016

Having lost the original Openstack Swift builder files but still having the ring.gz files it is possible to recreate the builder files.

Samuel Merritt gives the answer here, however, the code has a few bugs.

So using correcting these the following should do the job.

After generating the new builder file using the following (which you can just run using Pythons REPL), you can compare it with the original ring.gz with zcat. Just write the new ring swift-ring-builder account.builder write_ring.

from swift.common.ring import RingData, RingBuilder
ring = RingData.load('/etc/swift/account.ring.gz')

import math
partitions = len(ring._replica2part2dev_id[0])
replicas = len(ring._replica2part2dev_id)

from array import array
builder = RingBuilder(int(math.log(partitions, 2)), replicas, 1)
builder.devs = ring.devs
builder._replica2part2dev = ring._replica2part2dev_id
builder._last_part_moves_epoch = 0
builder._last_part_moves = array('B', (0 for _ in xrange(
for d in builder._iter_devs():
        d['parts'] = 0

for p2d in builder._replica2part2dev:
            for dev_id in p2d:
                builder.devs[dev_id]['parts'] += 1

builder.change_min_part_hours(24) # or whatever you want it to be


import pickle
pickle.dump(builder.to_dict(), open('account.builder', 'wb'), protocol=2)
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Morten Møller Riis

By Morten Møller Riis

I am a programmer, sysadmin, devops. I work for Gigahost in Copenhagen, Denmark. I am based in Odense, Denmark.

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