Make some networking parts deterministic - #21
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Introduce minimal, production-behaviour-preserving seams so the PeerManager networking subsystem can be tested deterministically, mirroring the sync subsystem's TestRig approach. Time seam: - Thread an injectable `now: Instant` through the heartbeat / score-decay / ban-expiry path: `PeerManager::heartbeat_at(now)` -> `PeerDB::update_scores_at(now)` -> `PeerInfo::score_update_at(now)` -> `Score::update_at(now)` -> `RealScore::update_at(now)`. - The production poll loop still calls `heartbeat()`, which delegates to `heartbeat_at(Instant::now())`, so production behaviour is identical. RNG seam: - Replace the single unseeded `rand::rng()` call in the prune-candidate selection with an injectable RNG field on `PeerManager`. Production uses an OS-seeded `StdRng` (Send-safe, equivalent randomness to the previous ThreadRng); tests can install a seeded `ChaCha20Rng` via `set_rng`. Tests (new `deterministic_tests` module + `PeerManagerRig` harness): - fatal_action_bans_immediately - downscores_transition_healthy_disconnect_banned - mid_tolerance_downscores_eventually_ban - ban_decays_after_logical_time_advance (uses the logical-time seam, no sleeps) - same_seed_produces_identical_outcomes Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Extend the injectable-time seam from Tier A (scoring) to the RPC rate
limiter and self-limiter, the other big source of behavioural
non-determinism in the network stack. Production behaviour is identical:
production entry points pass `Instant::now()`.
rate_limiter.rs:
- The inner `Limiter` already takes `time_since_start` as a parameter and was
fully time-injectable. The only wall-clock entry was
`RPCRateLimiter::{allows,prune}` via `self.init_time.elapsed()`.
- Add `allows_at(now)` / `prune_at(now)` (pub(crate)) that compute
`now.saturating_duration_since(self.init_time)`; keep `allows` / `prune` as
thin wrappers passing `Instant::now()`.
- Add a `#[cfg(test)] init_time()` accessor so tests can express logical time
as offsets from the limiter's creation instant.
self_limiter.rs:
- Thread an injectable `now: Instant` through `try_send_request` (used by both
`allows` and `next_peer_request_ready`) so the inner rate limiter is driven
via `allows_at(now)`. Public `allows` and `next_peer_request_ready` keep
their signatures and pass `Instant::now()`.
- Add a `#[cfg(test)] next_peer_request_ready_at(now)` and a
`rate_limiter_init_time()` accessor for deterministic tests.
- `timestamp_now()` (SystemTime) is left as-is: it only feeds `queued_at`
bookkeeping / an idling metric and does not drive any allow/reject decision.
handler.rs is intentionally untouched: its `Instant::now()` uses are debug-log
duration measurements only and do not affect limiter behaviour.
Tests added (deterministic, no real sleeps):
- partial_refill_after_partial_interval: token-bucket refill-math edge case
(4T/2s -> exactly 2 tokens back after 1.0s).
- rpc_rate_limiter_deterministic::allows_up_to_capacity_then_rejects
- rpc_rate_limiter_deterministic::refills_after_logical_time_advance
- rpc_rate_limiter_deterministic::prune_at_respects_logical_time
- self_limiter test_next_peer_request_ready_deterministic: queued requests
become ready only after logical time passes the replenish interval.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
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