fix: chase on admission, and never delete a snapshot over an RPC blip - #49
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…blip Two silent state-loss bugs found on the production 5chan seeder, which served a divergent tally on two topics for 13 days. `makeRootChaser`'s skip predicate was wired to blockstore membership, but admission lives in the CRDT. The two disagree exactly on the node that most needs the chase: one whose persistent blockstore outlived the state keyed on it. Such a node decoded every peer's checkpoint successfully (all blocks resolve locally!), skipped every bundle in it, admitted nothing, and could never converge again — restarting did not help, since the cold-start pull feeds the same chaser. The dep is now `isAdmitted`, wired to the engine's `#checks` map (the same admission map `#restoreSnapshot` consults). Closes #44. `#restoreSnapshot` wrapped the decode AND the per-bundle admission in one try/catch whose catch assumed a corrupt blob and deleted it — but the admission path reads the gating chain, so one rate-limit window during a seeder's boot burst (64 topics restoring at once) permanently discarded a topic's persisted votes. The decode is now the whole of the corruption test; admission runs in `#admitRestored`, where each bundle is independent and a transient failure (a throwing head read, a head that has not reached the bundle's sample bucket) backlogs it for a retry instead of dropping it. A non-empty backlog suppresses the snapshot write, so a partial view can never overwrite the good blob. And none of it is silent any more: a discarded blob, an incomplete restore and a write that keeps failing all surface as a `SnapshotError` on the contest's `error` event — which meant registering the view's engine listeners BEFORE the join, since the restore runs inside it. Closes #45. Regression tests pin both at the voter level: a node holding every block of a served checkpoint (bundle block included) still admits it, and a restore interrupted by a 429 keeps its blob, reports itself incomplete, refuses to overwrite the blob with the partial view, and admits the votes on retry.
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📝 WalkthroughWalkthroughThe voter now distinguishes corrupt snapshots from transient restore failures, retries incomplete restores, reports persistent snapshot errors, and suppresses unsafe writes. The chase now checks CRDT admission state instead of blockstore presence. ChangesSnapshot resilience
Estimated code review effort: 4 (Complex) | ~45 minutes Merge Risk: 🔵 Low · up to An expired restored bundle can leave stale admission state, potentially delaying snapshot persistence or convergence. The fix is localized, but should be addressed or explicitly accepted before merging. Sequence Diagram(s)sequenceDiagram
participant ContestView
participant VoterEngine
participant SnapshotStore
participant RPC
participant CRDT
ContestView->>VoterEngine: join()
VoterEngine->>SnapshotStore: load snapshot
VoterEngine->>RPC: evaluate restored bundle
RPC-->>VoterEngine: transient failure or evaluable state
VoterEngine->>CRDT: admit evaluable bundle
VoterEngine->>SnapshotStore: retain, retry, or write snapshot
VoterEngine-->>ContestView: SnapshotError on persistent failure
🚥 Pre-merge checks | ✅ 4 | ❌ 1❌ Failed checks (1 warning)
✅ Passed checks (4 passed)
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In `@src/client/voter.ts`:
- Line 1735: Update the join-time prune flow to remove each restored CID’s
`#checks` entry and invoke `#forgetOwnBundle`, matching computeTally() cleanup so
isAdmitted() and snapshot writes reflect the CID’s removal; add a regression
test covering an expired restored bundle.
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AGENTS.mdDESIGN.mdREADME.mdbenchmark/RESULTS.mdsrc/client/voter.test.tssrc/client/voter.tssrc/errors.tssrc/test-fixtures.tssrc/transport/chase.test.tssrc/transport/chase.tssrc/transport/integration/harness.ts
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`computeTally`'s prune deleted each removed CID's `#checks` entry and own-bundle tracking; `join()`'s prune discarded the returned CIDs. The asymmetry was harmless while `#checks` was only bookkeeping, but it now decides two things: `#hasUnsettledChecks` (an orphaned pending entry suppresses every snapshot write for the contest) and the chase's `isAdmitted` (an orphan makes it skip a bundle we no longer hold). Both prunes now run one method. Reachable in one restart: `verifyOffline` is deliberately expiry-blind, so a snapshot older than the expiry window restores its bundles and the join-time prune drops them again moments later. The tally refresh's own prune usually cleans up first — but only when an update listener is registered, which a publish-driven join has none of, and the regression test joins that way. Reported by CodeRabbit on #49.
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Fixes the two silent state-loss bugs behind the 5chan seeder's 13-day divergent tally on
/po/and/wsg/.Closes #44. Closes #45.
#44 — the chase skipped bundles it held blocks for but had never admitted
makeRootChaser's skip predicate was wired to blockstore membership, while admission lives in the CRDT. The two disagree on exactly the node that most needs the chase: one whose persistent blockstore outlived the state keyed on it (a restart that lost the snapshot, an eviction, a prune). Such a node decoded every peer's checkpoint perfectly — every block resolved locally — skipped every bundle, admitted nothing, and was permanently wedged: restarting did not help, because the cold-start pull feeds the same chaser, and nothing on that path logs.The dep is now
isAdmitted, wired to the engine's#checksmap — the same admission map#restoreSnapshotconsults, dropped in lockstep with the CRDT's membership. Erring this way is cheap by construction: the bytes were just decoded, so re-verifying a locally-held block costs no network, and it restores the re-verification the chase otherwise guarantees.#45 — a transient RPC failure during the restore deleted the snapshot
#restoreSnapshotwrapped the decode and the per-bundle admission in one try/catch whose catch assumed a corrupt blob and deleted it. But admission reads the gating chain, so one rate-limit window during a seeder's boot burst (64 topics restoring at once) permanently discarded a topic's persisted votes — and the node came up empty on a topic every other peer still served. The selection effect is the cruel part: topics whose voters republish on schedule self-heal within days, so the visible casualties are precisely the ballots of voters who went offline — the ones persistence exists to protect.#admitRestored, per bundle: an offline-check refusal drops that bundle only (a verdict on the bundle, no retry changes it); a transient failure (a throwing head read, a head that has not reached the bundle's sample bucket) goes to a backlog retried on exponential backoff (30 s → 10 min) while joined.SnapshotErroron the contest'serrorevent. That meant registering the reactive view's engine listeners before the join, since the restore runs inside it — errors emitted duringjoin()were previously unobservable.Tests
Regression coverage at the voter level, each verified to fail without its fix:
npm test(514),npm run test:integration(12), all four typechecks pass.Benchmark
BENCH_HOST=… npm run bench:cold-joinre-run (transport changed), median of 3, with a back-to-back master control on the same link window:START→TALLY3.18 / 3.12 / 3.13 / 3.28 / 5.82 s for N=1…1000 vs control 3.14 / 3.12 / 3.13 / 3.37 / 5.61 s — every column within jitter. Neither fix touches the measured path (the joiner starts empty). Recorded inbenchmark/RESULTS.md.Summary by CodeRabbit