SSE fan-out slows Files writes under open streams #189

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opened 2026-09-26 15:19:46 +00:00 by kayg · 1 comment
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Finding from the local real-server adversarial run on 2026-09-26.

tests/adversarial/attack2.py accepted 64 SSE streams for one user. With those streams open, 20 POST /api/v1/files/mkdir requests took 7.2 seconds. The probe reported SSE fan-out: 20 mkdirs took 7.2s with open streams without a SLOW classification.

The shared host load average was around 45–48 during this check, with several Calternal servers and adversarial jobs active. Reproduce this on a quiet host and determine whether SSE fan-out blocks unrelated Files writes under concurrent load.

Finding from the local real-server adversarial run on 2026-09-26. `tests/adversarial/attack2.py` accepted 64 SSE streams for one user. With those streams open, 20 `POST /api/v1/files/mkdir` requests took 7.2 seconds. The probe reported `SSE fan-out: 20 mkdirs took 7.2s with open streams` without a SLOW classification. The shared host load average was around 45–48 during this check, with several Calternal servers and adversarial jobs active. Reproduce this on a quiet host and determine whether SSE fan-out blocks unrelated Files writes under concurrent load.
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Duplicate evidence: #216 reports the same tests/adversarial/attack2.py scenario: 64 SSE streams for one User, then 20 POST /api/v1/files/mkdir writes. This issue records 7.2 seconds and #216 records 8.5 seconds; both runs had shared-host load. Recommend linking #216 here and combining the measurements before deciding if a product change is needed.

Duplicate evidence: #216 reports the same tests/adversarial/attack2.py scenario: 64 SSE streams for one User, then 20 POST /api/v1/files/mkdir writes. This issue records 7.2 seconds and #216 records 8.5 seconds; both runs had shared-host load. Recommend linking #216 here and combining the measurements before deciding if a product change is needed.
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kayg/calternal#189
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