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https://issues.apache.org/jira/browse/HBASE-23073?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16941253#comment-16941253
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Pierre Zemb commented on HBASE-23073:
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I just opened the PR: https://github.com/apache/hbase/pull/677
> Add an optional costFunction to balance regions according to a capacity rule
> ----------------------------------------------------------------------------
>
> Key: HBASE-23073
> URL: https://issues.apache.org/jira/browse/HBASE-23073
> Project: HBase
> Issue Type: Improvement
> Components: master
> Reporter: Pierre Zemb
> Assignee: Pierre Zemb
> Priority: Minor
>
> Based on the work in
> [HBASE-22618|https://issues.apache.org/jira/browse/HBASE-22618], users can
> now load custom costFunctions inside the main balancer used by HBase. As an
> example, we like like to add upstream an optional cost function called
> HeterogeneousRegionCountCostFunction that will deal with our issue: how to
> balance regions according to the capacity of a RS instead of using the
> RegionCountSkewCostFunction that is trying to avoid skew.
> A rule file is loaded from HDFS before balancing. It contains lines of rules.
> A rule is composed of a regexp for hostname, and a limit. For example, we
> could have:
> * rs[0-9] 200
> * rs1[0-9] 50
> RegionServers with hostname matching the first rules will have a limit of
> 200, and the others 50. If there's no match, a default is set.
> Thanks to the rule, we have two informations: the max number of regions for
> this cluster, and the rules for each servers. HeterogeneousBalancer will try
> to balance regions according to their capacity.
> Let's take an example. Let's say that we have 20 RS:
> 10 RS, named through rs0 to rs9 loaded with 60 regions each, and each can
> handle 200 regions.
> 10 RS, named through rs10 to rs19 loaded with 60 regions each, and each
> can support 50 regions.
> Based on the following rules:
> rs[0-9] 200
> rs1[0-9] 50
> The second group is overloaded, whereas the first group has plenty of space.
> Moving a region from the first group to the second should provide a lower
> cost.
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