docs(adr): concurrency-core decisions 0002-0005 (closes #24, #31, #33, #36)#169
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ADR-0002 shared-nothing thread-per-core (#24): shard k=HASH(KEY)%N, one owner per shard, no hot-path shared state; rejects KeyDB shared-dict spinlock, Redis single command thread, and tokio work-stealing. ADR-0003 design for determinism (#31): single-thread-per-shard + a controllable Env seam so seeded replay is byte-identical. ADR-0004 reclamation backbone (#33): none on the owned hot path, crossbeam-epoch for the rare shared structure, custom drain-list deferred to #64. ADR-0005 per-shard unsynchronized hashbrown map (#36); concurrent map only a documented fallback. Updates INDEX/OPEN/QUESTIONS. Closes #24 Closes #31 Closes #33 Closes #36 Signed-off-by: Zeke <ezequiel.lares@outlook.com>
- ADR-0004: document that this overrides issue #33's drain-list recommendation (its concurrent-reader premise collapses under single-owner shared-nothing); state the epoch-vs-custom contest is deferred to #64, not resolved here; fix citation [faster-hash-bucket-layout] -> [faster-epoch-protection]. - QUESTIONS.md: the #32 skew benchmark is filed as #170 (was wrongly marked already-filed). - ADR-0002/0005: add [valkey-io-threads-offload-scope], [keydb-spinlock-low-contention-claim]; precise dashmap/papaya wording. refs #33, refs #170 Signed-off-by: Zeke <ezequiel.lares@outlook.com>
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The architectural root: four ADRs that everything else inherits.
What
Envseam for byte-identical seeded replay (DST).crossbeam-epochfor rare shared structures; custom drain-list deferred to [DESIGN]: HybridLog storage engine with in-place hot-set updates #64.hashbrown::HashMap; concurrent map only a documented fallback.Review focus
Closes #24. Closes #31. Closes #33. Closes #36. Part of M0: Vision and Scope.