The previous run pinned the production failure to "82/100 frames at 20 ms cadence
two-users, all 18 trailing groups lost; publisher.send returned true for every
frame". To narrow the cause the next run needs to vary one dimension at a time
and dump rich per-frame data, so we can attribute the loss to:
- QUIC stream-credit (RTT-bound) vs absolute count cap
- Per-stream-creation cost vs per-byte cost
- Listener-side buffer overflow vs relay-side drop
- Steady-state vs initial-burst behaviour
- Shared end-of-stream FIN flush race vs prod-only loss
SendTraceScenario.kt: shared per-frame instrumented pump driver. Records
publisher.send Boolean per frame, send latency, endGroup exceptions,
arrivals per subscriber with wall-clock timing, missing-objectId run
lengths, send-latency p50/p99/max + count of >1ms sends. Verbose logging
(InteropDebug.checkpoint) emits one line per tx and one per rx so the
JUnit XML system-out doubles as a timing trace.
Sweep methods (mirrored prod-mode and harness-mode):
- baseline 100×20ms (reproduce known cliff)
- cadence sweep: 5 / 10 / 40 / 80 / 200 ms (RTT-dependent?)
- burst (no cadence) 100 frames (max inflight)
- frame-count sweep: 50 / 200 / 400
- payload sweep: 1 KB / 4 KB / 16 KB
- frames-per-group: 5 / 20 / 100 (uni-stream vs bytes)
- late subscribe at frame 25, frame 50 (from-latest semantics)
- mid-pump 5 s pause after frame 50
- 2-, 3-subscriber fan-out
- 50 ms slow-consumer listener (per-subscription buffer overflow)
- long-run 30 s and 120 s (steady-state)
Each test method is a one-line Scenario literal; setup helpers
withProdSpeakerAndListeners / withHarnessSpeakerAndListeners build
publisher + N listeners, run the scenario, and tear down in order.
Smoke-tested against the local kixelated/moq reference relay: every
scenario except framesPerGroup=100 reproduces the same trailing-frame
artifact (received=99/100, missing=[99]) the original test surfaced.
framesPerGroup=100 receives every frame, confirming the local issue is
specifically per-uni-stream FIN flushing — independent of the production
82/100 cliff.
Claude
2da1885975