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https://issues.apache.org/jira/browse/HBASE-29707?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Wellington Chevreuil resolved HBASE-29707.
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Resolution: Fixed
Merged into master, branch-3, branch-2 and branch-2.6. Thanks for the reviews,
[~psomogyi] and [~kgeiszler]!
> Fix region cache % metrics miss calculation
> -------------------------------------------
>
> Key: HBASE-29707
> URL: https://issues.apache.org/jira/browse/HBASE-29707
> Project: HBase
> Issue Type: Bug
> Components: BucketCache
> Affects Versions: 3.0.0-beta-1, 2.7.0, 2.6.4
> Reporter: Wellington Chevreuil
> Assignee: Wellington Chevreuil
> Priority: Major
> Labels: pull-request-available
> Fix For: 2.7.0, 3.0.0-beta-2, 2.6.5
>
>
> HBASE-28246 has introduced this metric that tracks the percentage of regions
> data that is cached, displaying this info on the RS UI store file metrics
> tab.
> Unfortunately, under the following scenarios, this metric can be
> miscalculated and display wrong information:
> 1) Region compactions: During compactions with cacheCompactedOnWrite set to
> true, we cache the new blocks written during compaction, which correctly
> updates the related metric, but once compaction is finished and compacted
> files have its readers closed, we are evicting the blocks but missing to
> decrease those from the metric.
> 2) Cache of hlinks pointing to files in archive: When caching an HLink for a
> file in the archive folder from a region that's still online, we are adding
> that file cached size to the original region, which is wrong, since the
> archived file blocks are not relevant for the original region, but to the
> region containing the link.
> In both cases, affected regions will show the “% Cache” metric beyond 100% on
> the Web UI, which can be misleading. Also, this metric is used by the
> CacheAwareLoadBalancer, and over counting region cache percentage can impact
> this balancer efficiency.
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