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https://issues.apache.org/jira/browse/HBASE-30305?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Vladimir Rodionov resolved HBASE-30305.
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Fix Version/s: 4.0.0-alpha-1
Resolution: Implemented
> Replace CombinedBlockCache orchestration with TieredExclusiveTopology-backed
> CacheAccessService
> -----------------------------------------------------------------------------------------------
>
> Key: HBASE-30305
> URL: https://issues.apache.org/jira/browse/HBASE-30305
> Project: HBase
> Issue Type: New Feature
> Components: BlockCache, Performance
> Affects Versions: 4.0.0-alpha-1
> Reporter: Vladimir Rodionov
> Assignee: Vladimir Rodionov
> Priority: Major
> Labels: pull-request-available
> Fix For: 4.0.0-alpha-1
>
>
> h3. Description
> HBASE-30024 introduced BlockCacheBackedCacheEngine, allowing existing
> BlockCache
> implementations to participate as CacheEngine instances.
> HBASE-30025 added the construction path for creating a
> TopologyBackedCacheAccessService
> from existing L1 and L2 BlockCache instances using TieredExclusiveTopology.
> The next step is to replace CombinedBlockCache as the primary L1/L2
> orchestration object
> used by CacheAccessService.
> Today, the combined block cache path is assembled as:
> LruBlockCache + BucketCache
> -> CombinedBlockCache
> -> BlockCacheBackedCacheAccessService
> This ticket should change the CacheAccessService construction path to use:
> LruBlockCache + BucketCache
> -> BlockCacheBackedCacheEngine
> -> TieredExclusiveTopology
> -> TopologyBackedCacheAccessService
> CombinedBlockCache should not be removed in this ticket. It should remain
> available for
> legacy APIs, diagnostics, tests, and any code paths that still require a
> BlockCache instance.
> However, new cache access should no longer depend on CombinedBlockCache for
> tiered
> orchestration.
> The goal is to make TieredExclusiveTopology the primary orchestration model
> for the
> combined L1/L2 cache path while preserving existing behavior and keeping
> CombinedBlockCache
> as a compatibility object.
> h3. Scope
> * Change CacheConfig / BlockCacheFactory construction so CacheAccessService
> for combined
> L1/L2 cache uses TopologyBackedCacheAccessService.
> * Reuse
> TopologyBackedCacheAccessServices.fromTieredExclusiveBlockCaches(...).
> * Keep LruBlockCache and BucketCache as existing BlockCache implementations
> underneath.
> * Keep CombinedBlockCache class in the source tree.
> * Keep any existing BlockCache-returning APIs working if they still need to
> expose a
> CombinedBlockCache or legacy BlockCache view.
> * Add tests proving the CacheAccessService path no longer wraps
> CombinedBlockCache when
> L1/L2 combined cache is enabled.
> * Add compatibility tests proving the old BlockCache view, if still exposed,
> remains usable.
> h3. Out of scope
> * Do not delete CombinedBlockCache.
> * Do not migrate LruBlockCache or BucketCache to implement CacheEngine
> directly yet.
> * Do not remove BlockCacheBackedCacheAccessService.
> * Do not migrate JSP/admin diagnostics yet unless required by compilation.
> * Do not remove CombinedBlockCache tests yet.
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