databendlabs / openraft / 23290677096

86%

Build Type

push

github

Committed by drmingdrmer

Commit Message

feat: add DeterministicRng to make a runtime deterministic

Replaces the global AtomicU64 seed with per-instance seed stored in
task-local storage. Each DeterministicRng instance owns its seed counter,
set via set_seed() and propagated into block_on() via sync_scope.

Seed derivation uses two SplitMix64 bijective mixers with different
additive constants (golden ratio vs sqrt(2)) to prevent collisions
in the spawn tree: child.seed = f(parent.seed), parent.seed = g(parent.seed).
This ensures parent, child, and sibling tasks all get independent
deterministic RNG sequences.

Suite::test_all() is now sync — creates its own runtime internally,
simplifying callers to just Suite::<Rt>::test_all().

Changes:
- Add DeterministicRng<RT> with per-instance Cell<u64> seed
- Add splitmix64() mixer, derive_spawn_seed(), advance_seed()
- spawn() wraps child future in DETSIM_SEED.scope() with derived seed
- Add DetsimSuite with 4 determinism tests (self-contained block_on)
- Change Suite::test_all() from async to sync
- Change ThreadLocalRng bound from RngCore to Rng

- Part of: #639

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2 existing lines in 2 files now uncovered.

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