[jira] [Created] (HBASE-30018) Pluggable HBase Block Cache System

["Vladimir Rodionov (Jira)" <ji...@apache.org>]

Vladimir Rodionov created HBASE-30018:
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             Summary: Pluggable HBase Block Cache System
                 Key: HBASE-30018
                 URL: https://issues.apache.org/jira/browse/HBASE-30018
             Project: HBase
          Issue Type: Umbrella
          Components: BlockCache
            Reporter: Vladimir Rodionov
            Assignee: Vladimir Rodionov


This umbrella tracks work to refactor the HBase block cache into a pluggable architecture with clear separation of:
	•	cache storage (engine)
	•	cache topology (L1/L2 orchestration)
	•	placement and admission policy

The current design tightly couples these concerns (BlockCache, CombinedBlockCache, BucketCache), making it difficult to introduce new cache implementations and evolve cache behavior.

In addition, existing implementations (e.g., BucketCache) incur significant metadata overhead at large scale (e.g., ~9GB for ~1.6TB cache with 64KB blocks), reducing effective cache capacity.

This effort introduces:
	•	BlockCacheEngine (storage abstraction)
	•	CacheTopology (tier orchestration)
	•	CachePlacementPolicy (admission, placement, promotion)
	•	explicit cache admission control on write/put path
	•	CacheAccessService for read/write path integration

The work will be implemented incrementally:
	•	Phase 1: introduce internal APIs (no behavior change)
	•	Phase 2: refactor existing topology (CombinedBlockCache)
	•	Phase 3: adapt BucketCache to new interfaces
	•	Phase 4: enable new engines (e.g., CarrotCache)

This umbrella groups the individual tasks required to deliver this functionality.

RFC design doc: https://docs.google.com/document/d/1DOoRfqdDzC-Nz9zfCzSed8vbhRe5BMz8/edit?usp=sharing&ouid=107898024699489289958&rtpof=true&sd=true



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