This topic might be better posted on openstack-dev Vish
On Feb 26, 2013, at 11:24 AM, Kun Huang <[email protected]> wrote: > Hi swift developer, > > I'm confused about implementation of ring structure. > > in the RingBuilder, line 671 ~ 681 > > > for part, replace_replicas in reassign_parts: > > > # Gather up what other tiers (zones, ip_ports, and devices) the > > # replicas not-to-be-moved are in for this part. > > other_replicas = defaultdict(int) > > > unique_tiers_by_tier_len = defaultdict(set) > > > for replica in xrange(self.replicas): > > > if replica not in replace_replicas: > > > dev = self.devs[self._replica2part2dev[replica][part]] > > > for tier in tiers_for_dev(dev): > > > other_replicas[tier] += 1 > > > unique_tiers_by_tier_len[len(tier)].add(tier) > > > > > this while loop results in other_replicas and unique_tiers_by_tier_len, but I > don't have a confirmed understanding about these two data. > > > and in line 684 to 725: (I removed comments) > > > tier = () > > > depth = 1 > > > while depth <= max_tier_depth: > > > candidate_tiers = tier2children[tier] > > > candidates_with_replicas = \ > > unique_tiers_by_tier_len[len(tier) + 1] > > > if len(candidate_tiers) > len(candidates_with_replicas): > > > for t in reversed(candidate_tiers): > > > if other_replicas[t] == 0: > > > tier = t > > > break > > else: > > min_count = min(other_replicas[t] > > > for t in candidate_tiers) > > > tier = (t for t in reversed(candidate_tiers) > > > if other_replicas[t] == min_count).next() > > > depth += 1 > > > > this loop search the tier tree, from () to (zone, ip, device), for finding a > tier, and choosing a dev by that tier, and storing dev id in part key(line > 762, that's a kind of final ring structure?). And the propose of tree > structure is: > > """ > This is already supported in Swift with the concept of availability zones. > Swift will place each replica in different availability zones, if possible. > If you only have one zone, Swift will place the replicas on different > machines. If you only have one machine, Swift will place the replicas on > different drives. > > -- John > """, right? > > > And the last loop line 732 to line 760 only works on sorting for next big > loop? (line 683) > > > The propose of rebalance is to put every replica on correct partition, and > put every partition on correct device? > > > > Gareth > > _______________________________________________ > Mailing list: https://launchpad.net/~openstack > Post to : [email protected] > Unsubscribe : https://launchpad.net/~openstack > More help : https://help.launchpad.net/ListHelp
_______________________________________________ Mailing list: https://launchpad.net/~openstack Post to : [email protected] Unsubscribe : https://launchpad.net/~openstack More help : https://help.launchpad.net/ListHelp
