VladRodionov opened a new pull request, #8501:
URL: https://github.com/apache/hbase/pull/8501
### Summary
This PR adds a construction path for creating a topology-backed
`CacheAccessService`
from existing L1 and L2 `BlockCache` instances.
The pluggable block cache architecture now has the basic components needed
for
topology-backed cache access:
* `CacheEngine`
* `CacheTopology`
* `CachePlacementAdmissionPolicy`
* `CacheAccessService`
* `TieredExclusiveTopology`
* `TopologyBackedCacheAccessService`
* `BlockCacheBackedCacheEngine`
This PR wires those pieces together for the current CombinedBlockCache-style
L1/L2
model. Existing `BlockCache` instances are adapted to `CacheEngine` using
`BlockCacheBackedCacheEngine`, assembled into a `TieredExclusiveTopology`,
and exposed
through `TopologyBackedCacheAccessService`.
### Changes
* Adds `TopologyBackedCacheAccessServices`, a small helper class for
constructing
topology-backed cache access services.
* Adds `fromTieredExclusiveBlockCaches(...)` for creating a
`TopologyBackedCacheAccessService` from existing L1 and L2 `BlockCache`
instances.
* Adds tests verifying that the constructed service uses:
* `BlockCacheBackedCacheEngine` for L1 and L2 adaptation
* `TieredExclusiveTopology`
* the supplied `CachePlacementAdmissionPolicy`
* Adds behavior tests for CombinedBlockCache-compatible exclusive tier
behavior:
* L1 hit
* L2 hit
* miss
* L2-to-L1 promotion
* rejected cache insertion
* cache insertion into policy-selected tiers
* eviction from both tiers
* shutdown propagation
### Why this is needed
The current production L1/L2 block cache model is represented by
`CombinedBlockCache`,
typically coordinating `LruBlockCache` as L1 and `BucketCache` as L2.
The new architecture models this as:
```text
CacheAccessService
-> CacheTopology
-> CacheEngine(s)
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