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https://issues.apache.org/jira/browse/HBASE-30303?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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chaijunjie updated HBASE-30303:
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Attachment: screenshot-2.png
> Regions can not balance when enable rsgroup fallback and all regionservers
> dead in one group
> --------------------------------------------------------------------------------------------
>
> Key: HBASE-30303
> URL: https://issues.apache.org/jira/browse/HBASE-30303
> Project: HBase
> Issue Type: Bug
> Components: Balancer
> Affects Versions: 2.6.6
> Reporter: chaijunjie
> Priority: Major
> Attachments: screenshot-2.png
>
>
> With RSGroup fallback enabled, a table may belong to an RSGroup that has no
> online RegionServers. Its regions are therefore assigned to the default
> RSGroup, or to any available RegionServer if the default group also has no
> online servers.
> The regions remain available on these fallback servers. However, *during
> every balance run, RSGroupBasedLoadBalancer validates their current locations
> only against the table’s original RSGroup.* *Because that group still has no
> online RegionServers, all fallback-hosted regions are classified as
> misplaced. The balancer then creates region move plans with no explicit
> destination, causing the regions to be randomly reassigned among the fallback
> candidates*. The same process repeats on every balance run, resulting in
> continuous and unnecessary region movement even when the fallback servers are
> already balanced.
> !screenshot-1.png!
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