Daniel Roudnitsky created HBASE-28559:
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Summary: Region quotas: Multi-region merge causes inaccurate
accounting of region counts
Key: HBASE-28559
URL: https://issues.apache.org/jira/browse/HBASE-28559
Project: HBase
Issue Type: Bug
Components: Quotas
Affects Versions: 3.0.0-beta-2
Reporter: Daniel Roudnitsky
Assignee: Daniel Roudnitsky
There is support for merging more than two regions in one merge procedure with
multi-region merge, but if region quotas are enabled, [NamespaceAuditor assumes
that every merge is a two region
merge|https://github.com/apache/hbase/blob/branch-3/hbase-server/src/main/java/org/apache/hadoop/hbase/namespace/NamespaceAuditor.java#L128-L129].
This causes an inaccurate in memory accounting of region counts in
NamespaceStateManager, leading MasterQuotaManager to believe there are more
regions than actually exist if multi-region merge is used.
To demonstrate the issue:
1. Start with a table with 3 regions in a namespace with a region quota limit
of 3
2. Merge all 3 regions leaving 1 region, NamespaceAuditor assumed it was a 2
region merge and believes the number of regions to be 2.
3. Split a region, number of regions is now 2, and NamespaceAuditor believe it
to be 3.
4. Attempt another region split, which will fail because NamespaceAuditor
believes the ns to be at its region limit of 3 when there are actually only 2
regions.
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