Vladimir Rodionov created HBASE-30305:
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Summary: 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
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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