Don't let telemetry/logging cook the loop under a storm.
- lib/log-coalescer.js: dedup+count high-frequency lines, flush ONE summarized line per
key per window ("[loop-lag] band=critical (x47 in 30s)"). Bounded buffer (auto-flush
at MAX_KEYS). Applied to the loop-lag "still loaded" line (band CHANGES stay immediate),
the per-request OTA check line, and "Device reconnected".
- loop-lag: event_loop_lag rows are BUFFERED and batch-inserted on a flush interval
(was a synchronous INSERT per sample); the buffer is bounded (drop-oldest). Its
retention prune now rides the Item-A chunkedDelete so this table can never repeat the
status_log bloat-then-freeze. /api/status still reads in-memory current (real-time
band unaffected).
- Bounded the previously un-evicted per-device Maps: content-ack limiter gets an idle
sweep (started in server.js); status-log-writer.lastWritten is capped (drop-oldest;
it only suppresses a redundant consecutive row, so eviction is safe).
Tests: N identical lines -> one counted line; single line verbatim; coalescer buffer
bounded under a distinct-key flood; content-ack Map swept of idle buckets.
loop-lag-integration updated for the batched-insert cadence. Suite 266/266.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Gates genuine reconnects PER DEVICE before the heavy register work (DB writes +
playlist build) runs, so a single flapping device can no longer saturate the
event loop and take down the server.
- Actuator is per-device, keyed on device_id (modeled on lastPlayLogAt). A device
is flagged only when it exceeds reconnectBaseMax genuine reconnects per window.
Same-socket playlist refreshes (isPlaylistRefresh) are exempt.
- Load-awareness is BANDED (normal/elevated/critical from the step-2 lag signal),
not a continuous controller. The band only MULTIPLIES an already-flagged
device's backoff; global lag never gates a healthy device.
- Hysteresis: escalate immediately while storming (tighten fast); decay one level
per reconnectReleaseMs of calm (release slow).
- HARD CEILING per device, independent of band and warm-up — a slow-ramp attacker
can't train through it.
- COLD START: for reconnectWarmupMs after boot, force the normal band and apply
only the hard ceiling, so a full-fleet reconnect after a deploy doesn't throttle
healthy screens. State is in-memory, resets on restart.
- Observability: every throttle engagement logs device, band, observed vs allowed
rate, and backoff. Throttled device gets device:throttled + a deferred disconnect.
Tests (api.test.js style):
- unit: healthy-never-throttled, storm-throttled-with-growing-backoff, band
multiplies backoff, hard-ceiling-even-in-warmup, warm-up leniency, neighbor
isolation, slow release.
- integration GATE (the required one): full-fleet reconnect right after restart
throttles NO healthy device; a single device storming IS throttled; a neighbor
stays unaffected while another storms.
- also fixes pre-existing test PORT collisions (my new integration files clashed
with totp.test.js:3979 and totp-keyrotation.test.js:3980 -> moved to 3982/3983);
full suite now green serially AND in parallel.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Continuously samples event-loop delay via perf_hooks.monitorEventLoopDelay()
(C++-backed histogram; cheap). Each window persists mean/p50/p99/max to a new
event_loop_lag table and recomputes a coarse load band (normal/elevated/critical)
from the window p99. Standalone value: current lag is exposed on /api/status and
band changes are logged, so site lag is diagnosable independent of throttling.
The band feeds the #142 reconnect throttle (next commit) but ships first as its
own subsystem.
- event_loop_lag is bounded from day one: indexed on sampled_at + scheduled prune
(LAG_TELEMETRY_RETENTION_DAYS, small default) modeled on the play_logs prune.
Deliberately NOT another unbounded-growth table.
- Band transitions are asymmetric: jump up immediately (tighten fast), release one
level at a time after N calm samples below a deadband (release slow, no flap).
Pure nextBand() function, unit-tested deterministically.
- config: LAG_SAMPLE_INTERVAL_MS, LAG_RESOLUTION_MS, LAG_TELEMETRY_RETENTION_DAYS,
LAG_PRUNE_INTERVAL_MS, LAG_ELEVATED_MS, LAG_CRITICAL_MS, LAG_RELEASE_SAMPLES.
- tests: band-transition unit tests; integration proves sampling persists, stays
bounded under the prune, and surfaces on /api/status.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
