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fix(protocol): keep subscriptions receiving deltas when a publish rings before registration - #334
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… a publication rung before registration cannot silence it The hub puts a new subscriber's doorbell on its view as soon as it attaches, but the connection registers the subscriber only when the `.subscribe` reply is released. A publication in between rang the doorbell; the connection took that wake-up for an unknown subscriber and dropped it without answering, so the doorbell stayed marked queued and swallowed every later ring. The client got its snapshot and then nothing, with no error. Registering now answers the doorbell and rings again when the view published since the subscriber's starting point. Answering before loading the cell keeps the existing sequentially consistent handshake: a concurrent publication is either seen by the check or rings an answered doorbell. No lock is added, and delivery is unchanged. Tests force the race deterministically on new and shared views, check a registration with nothing new queues no wake-up, stress registrations during a write burst (23 of 24 subscriptions froze at their snapshot without the fix), and check over /ws that subscriptions sent during a write burst get every delta with gapless seq.
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Intent
I want you to really hyper focus on making the symbolic engine, you know, crisp and really truly production ready. (Context: the adversarial audit, ~/firstmate/data/engine-prod-audit/report.md, found a P0 (code-confirmed): a subscription can silently stop receiving deltas forever: a publish that rings its doorbell before finish_subscribe registers the subscriber is dropped without answer() (src/protocol/subscription/connection.rs:251, publication.rs:104), so 'queued' stays true and no later publish is delivered.)
What Changed
Subscriber::resume(), which answers the subscriber's doorbell and rings it again if the view published after the subscriber's starting point. Before this, a wake-up rung ahead of registration was dropped as stale without an answer. The doorbell stayed marked as queued, so it ignored every later ring and the subscription stopped getting deltas for good.finish_subscribeinconnection.rsnow builds the subscriber and callsresume()before adding it to the connection's subscriber map. The comment on the stale wake-up path now explains that registering resumes the doorbell.resume(), covering a wake-up rung before registration and the case with nothing new. Also added connection tests: a ring before registration for both a new view and a shared view, a registration with nothing new that queues no wake-up, and subscriptions registered during a write burst that converge.Risk Assessment
✅ Low: The fix is small and fully closes the P0 lost-wakeup sequence. It resets the doorbell's queued flag, then re-rings if the cell moved past the attachment's publication. The calls are ordered answer, then load, then ring, so a publish either is observed or rings an answered doorbell. finish_subscribe and deliver run on the same &mut connection task, so the re-ring is only consumed after registration. advance() keeps the publication number, so it never causes a spurious ring. Construction in finish_subscribe is the only Subscriber registration path. The regression tests exercise the real behavior rather than reading source.
Testing
Ran the targeted subscription unit tests with and without the fix. The three new connection-level regression tests fail when
resume()is disabled and pass with it. Then I started the real inputlayer-server in an isolated temp directory and drove it over /ws with a Node client. In 5 stress runs, 80 subscriptions opened during a 400-write burst all ended at the exact current result, with no seq gaps and the final write delivered to every one. An idle subscription got no spurious pushes, and the next write gave exactly one delta with seq 1. Two early driver bugs (stale rows left in the relation by an earlier run; counting non-subscription notifications) were fixed and the checks re-run. The server and temp data were torn down. The live stress run can't by itself prove the race was hit; the deterministic unit tests are what reproduce the bug.git diff fe9ffe2a HEAD --stat -- testscame back empty.Evidence: Regression tests fail with the fix disabled
Evidence: Regression tests pass with the fix
Evidence: Live /ws write-burst subscription convergence (5 runs)
Evidence: Live /ws idle subscription: no spurious push, then one delta
snapshot [[1]] {"subscription":"watch","generation":1,"revision":2429} pushes after 1.5s idle: 0 pushes after one write: [{"type":"subscription_delta","seq":1,"inserted":[[2]],"retracted":[]}]Pipeline
Updates from git push no-mistakes
✅ **intent** - passed
✅ No issues found.
✅ **Rebase** - passed
✅ No issues found.
✅ **Review** - passed
✅ No issues found.
🔧 **Test** - 1 issue found → auto-fixed ✅
tests/standing_query_tests/main.rs:418- The new integration test test_subscriptions_registered_during_a_write_burst_get_every_delta (tests/standing_query_tests/main.rs) passed 5/5 times on pre-fix source, so it does not reliably reproduce the lost wake-up. My external /ws stress drivers also never triggered it on the pre-fix binary. The regression guard really rests on the deterministic connection-level unit tests, which do fail before the fix. The author should decide whether to keep the integration test as a smoke test or tighten it.cargo test --lib protocol::subscription::(82 passed on HEAD, including the new connection/subscriber regression tests)cargo test --test standing_query_tests(28 passed on HEAD, including test_subscriptions_registered_during_a_write_burst_get_every_delta)Pre-fix check: reverted src/protocol/subscription/{connection,subscriber}.rs to fe9ffe2a, thencargo test --lib protocol::subscription::connection::tests: a_wake_up_before_registration_does_not_silence_a_new_view, ..._shared_view and subscriptions_registered_during_a_write_burst_converge FAIL; sources restoredPre-fix check:cargo test --test standing_query_tests test_subscriptions_registered_during_a_write_burstx5 on pre-fix source (passed all 5 times, so this integration test does not reliably reproduce the bug)Builtcargo build --release --bin inputlayer-serverfor HEAD and for the pre-fix source; ran each with a disposable config/data dir under /tmp on a loopback portLive: drive.py, 10 rounds x 32.subscribeover /ws during a sequential write burst, fixed binaryLive: drive.py, 8 rounds x 64 subscriptions with 8 concurrent writer connections (~1850 commits/round), fixed and pre-fix binariesLive: shared_race.py: second subscriber joins a slow shared view mid re-evaluation, then a later commit must reach it (fixed x3, pre-fix x7)Live: race.py:.subscribepipelined behind a 2.5s query while another client commits, then a later commit must reach it (fixed and pre-fix)🔧 Fix applied.
✅ Re-checked - no issues remain.
git diff fe9ffe2a HEAD --stat -- testscame back empty.cargo test --lib protocol::subscription(82 passed with the fix)Disabledregistered.resume()in src/protocol/subscription/connection.rs and rancargo test --lib protocol::subscription::connection: 3 new regression tests FAILED (new view, shared view, write-burst convergence); restored withgit checkoutcargo test --lib protocol::subscription::connectionwith the fix: 13 passedBuiltinputlayer-serverand ran it on 127.0.0.1:18931 with a throwaway --data-dir and config under /tmp (removed afterwards)Live Node WebSocket driver, 5 runs, each on a fresh relation: 4 connections × 20.subscribeframes, each sent right behind an earlier query on the same connection, during a 400-write burst from a separate connection, followed by one final write; each subscription's snapshot plus deltas compared to a live?rel(X)queryLive idle check:.subscribewith no further writes saw 0 subscription pushes in 1.5s, then a single write gave exactly onesubscription_deltawith seq 1git diff fe9ffe2a HEAD --stat -- testsis empty, confirming the integration test was removed as decided in round 1✅ **Document** - passed
✅ No issues found.
✅ **Lint** - passed
✅ No issues found.
✅ **Push** - passed
✅ No issues found.