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Merged
kixelated merged 1 commit into from
Oct 10, 2026
Merged

quest: plan the cluster burst overrun flake #5161

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1 change: 1 addition & 0 deletions quest/m1/test-flakes-2/README.md
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Expand Up @@ -36,4 +36,5 @@ Public API: none. Wire: none.
- [Import catalog finish](/quest/m1/test-flakes-2/import-catalog-finish.md) - `moq-cli`'s subprocess EOF catalog-finish test holds up under load with event-based fixture coordination
- [Relay restart rebind](/quest/m1/test-flakes-2/relay-restart-rebind.md) - the crash drill restarts on its original UDP address under concurrent load
- [Impaired handshake](/quest/m1/test-flakes-2/impaired-handshake.md) - the impaired cluster drills' clients never time out while connecting
- [Cluster burst overrun](/quest/m1/test-flakes-2/cluster-burst-overrun.md) - the impaired cluster burst drill always overruns its bottleneck, so it always exercises it
- [Media audio tone](/quest/m1/media-audio-tone.md) - the `just test media` audio-tone check passes under load, fixed at its cause
20 changes: 20 additions & 0 deletions quest/m1/test-flakes-2/cluster-burst-overrun.md
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# [S] Cluster burst drill always overruns its bottleneck

## Goal

`bursts_cross_a_cluster::impaired` (`rs/moq-relay/tests/drills.rs`) always
exercises its bottleneck: every run has at least one burst that overruns
the 100 kbit/s link, so its "no burst overran a bottleneck, so none was
exercised" precondition never fails.

## Plan

Found in #5160's loaded runs (2026-10-09): 5 of about 450 runs of the drills
binary at load average 40-60 failed that precondition. Decided 2026-10-09:
keep the precondition, since a run that never overruns tests nothing. Find
why a burst sometimes fits (for example, pacing that lets the shaper drain
between frames under load), then size or schedule the bursts from the
shaper's capacity so the overrun is guaranteed. No retry, and no lowering
of what counts as an overrun.

Public API: none. Wire: none.
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