The #142 burst throttle (5/10s) misses a device flapping every 3-5s (~2-3/10s) — yet
each cycle is an expensive register+build+acks and one status_log row (the spiral
trigger). Now that Item A ends the restart loop that used to wipe in-memory throttle
state every ~40s, an in-memory sustained limiter can finally bite.
- lib/device-identity.js: SNAT-safe identity resolution — device_id -> fingerprint
(map via device_fingerprints -> device_id, else raw fp) -> device_token -> ONE bounded
global anon bucket. NEVER IP (the fleet SNATs to 10.10.10.1). An unidentifiable client
is still bucketed (collectively) so an anon flood is capped, never unthrottled.
- lib/flap-limiter.js: per-identity connect-frequency over a long window
(CONNECT_RATE_WINDOW_MS=5min, CONNECT_RATE_MAX=20; anon bucket cap 60). Over the rate
-> refuse + disconnect (cheap). Bounded by an idle sweep (anon bucket never swept).
Optional auto-quarantine: a device_id-resolved hard flapper -> blocked=1.
- Wired at the device:register gate BEFORE fingerprint tracking/throttle/DB/build,
skipping same-socket playlist refreshes. Sweep started in server.js.
Tests: 4s-flapper refused after the window max; 60s-normal never; two device_ids
independent (never IP); device_id-less bucketed by fingerprint; neither id nor
fingerprint capped via global anon; idle sweep preserves the anon bucket. Suite 254/254.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
