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https://issues.apache.org/jira/browse/HBASE-12762?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Andrew Purtell resolved HBASE-12762.
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Resolution: Fixed
> Region with no hfiles will have the highest locality cost in
> LocalityCostFunction
> ---------------------------------------------------------------------------------
>
> Key: HBASE-12762
> URL: https://issues.apache.org/jira/browse/HBASE-12762
> Project: HBase
> Issue Type: Improvement
> Components: Balancer
> Affects Versions: 0.99.2
> Reporter: cuijianwei
> Assignee: cuijianwei
> Priority: Minor
> Fix For: 1.0.0, 2.0.0, 0.98.10, 1.1.0
>
> Attachments: HBASE-12762-trunk.patch
>
>
> The locality cost of region will be computed in LocalityCostFunction.cost as:
> {code}
> double cost() {
> ...
> int index = -1;
> for (int j = 0; j < regionLocations.length; j++) {
> if (regionLocations[j] >= 0 && regionLocations[j] == serverIndex) {
> index = j;
> break;
> }
> }
> if (index < 0) {
> cost += 1; // ==> region with no hfiles will have the highest cost
> } else {
> cost += (double) index / (double) regionLocations.length;
> }
> ...
> }
> {code}
> The region with no hfiles(such as empty region) will have the highest cost
> which represents the worst case that region located in the server with no
> locality for hfiles. However, this might be the best case because there are
> no hlogs for the region. Although the absolute cost value won't affect the
> balance process, will it be more reasonable to have zero cost for such
> regions? such as:
> {code}
> ...
> if (index < 0) {
> if (regionLocation.length > 0) { // ==> only consider regions with
> hfiles
> cost += 1;
> }
> } else {
> cost += (double) index / (double) regionLocations.length;
> }
> ...
> {code}
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