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https://issues.apache.org/jira/browse/PHOENIX-7799?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Rahul Kumar resolved PHOENIX-7799.
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Resolution: Resolved
> Coalesce splits by region server to avoid hotspotting from concurrent mappers
> -----------------------------------------------------------------------------
>
> Key: PHOENIX-7799
> URL: https://issues.apache.org/jira/browse/PHOENIX-7799
> Project: Phoenix
> Issue Type: Sub-task
> Affects Versions: 5.2.0, 5.2.1, 5.3.0
> Reporter: Rahul Kumar
> Assignee: Rahul Kumar
> Priority: Major
>
> PhoenixSyncTableTool creates one MapReduce InputSplit per HBase region,
> causing each split to spawn its own mapper task. When multiple regions reside
> on the same RegionServer, concurrent mappers hit the same server
> simultaneously, leading to hotspotting and resource contention (noisy
> neighbor problem). This degrades performance and can cause timeouts.
> Implement locality-aware split coalescing that groups all InputSplits from
> the same RegionServer into a single coalesced split. This ensures only one
> mapper processes regions from each server sequentially, eliminating
> concurrent requests and hotspotting. The feature will be controlled by the
> configuration property phoenix.sync.table.split.coalescing (default: false).
> For a table with 100 regions across 5 RegionServers, this reduces mapper
> count from 100 to 5, eliminating server-side contention while maintaining
> data locality.
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