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https://issues.apache.org/jira/browse/HBASE-29070?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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ASF GitHub Bot updated HBASE-29070:
-----------------------------------
Labels: pull-request-available (was: )
> Balancer cost function epsilon is imprecise
> -------------------------------------------
>
> Key: HBASE-29070
> URL: https://issues.apache.org/jira/browse/HBASE-29070
> Project: HBase
> Issue Type: Bug
> Affects Versions: 2.6.1
> Reporter: Ray Mattingly
> Assignee: Ray Mattingly
> Priority: Major
> Labels: pull-request-available
>
> The balancer cost function is imprecise. This means that the balancer can
> behave in unexpected ways at certain scales. For example, with enough regions
> and replicas, it's very possible for the
> StochasticLoadBalancers#areReplicasColocated (paraphrased) method to return a
> false negative, and fail to trigger a balancer run despite bad replica
> locations existing.
> One immediate consequence of this bug is that our test suites are designed in
> slow and flappy ways. They all have huge balancer run times, but really our
> tests should be designed with tight balancer run times and iteration if
> necessary (in most cases). If we had done that, then it would've exposed this
> failure of the balancer to act as necessary, and our test suite would be much
> faster.
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