screentinker/server/ws
ScreenTinker dbac699854 fix(#143): content-ack flood control — per-device rate budget + loop-lag valve
#142's content-ack dedup is insufficient: a device cycling 2-4 content IDs makes
every ack look unique so dedup never fires, while aggregate volume from ~30 devices
saturates the event loop (the #142 reconnect throttle kept the server responsive,
which is how this was even observable).

Folded ONE control on the content-ack path (no competing limiters; reconnect-
throttle.js untouched) in lib/content-ack-limiter.js:
- Step 1 — per-device RATE budget: caps TOTAL non-duplicate acks per device per
  window regardless of differing content_id (the case dedup misses). Over budget =
  DROP silently (the per-ack log+emit is the cost); log ONCE per device per window
  when shedding starts. Keeps the #142 dedup (dedup'd repeats don't consume budget).
  Per-device, in-memory, resets on restart (modeled on lastPlayLogAt; does NOT reuse
  reconnect-throttle's ban-semantics bucket).
  Env (TUNING GUESSES, validate vs Bold's fleet): CONTENT_ACK_MAX_PER_WINDOW=20,
  CONTENT_ACK_RATE_WINDOW_MS=10000 (=2/s, above legit ~<=1/s, below the flood).
- Step 2 — global pressure valve: reuses the #142 loop-lag band (+ its hysteresis,
  no second control loop). Under CRITICAL band, shed content-acks even for an
  in-budget device; reconnects + dashboard/HTTP are ALWAYS processed; a healthy
  device in a non-critical band is never touched by the valve. Valve open/close
  logged once at the band edge in services/loop-lag.js (not per shed message).

Tests (unique ports 3985/3986, not the 3982/3983/3984 set):
- unit: the #143 regression (cycling ids evading dedup IS rate-limited), under/over
  budget, dedup still works + doesn't consume budget, valve sheds in-budget under
  critical while normal is untouched, rate precedence, window reset, per-device
  isolation.
- integration: socket flood is capped to budget with a single shed-start log;
  under-budget passes every ack; valve OPEN sheds content-acks while a reconnect +
  /api/status still succeed.
Full suite green serial AND parallel (208 tests).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
2026-06-27 22:21:57 -05:00
..
dashboardSocket.js fix(socket): offline debounce + truthful single-device command feedback 2026-05-14 13:11:40 -05:00
deviceSocket.js fix(#143): content-ack flood control — per-device rate budget + loop-lag valve 2026-06-27 22:21:57 -05:00
index.js Initial open source release 2026-04-08 12:14:53 -05:00