[Performance] Thread Pool Size Limits Segment Upload Throughput

[filthyrake]

Summary

The ThreadPoolExecutor for segment I/O only has 16 workers for ALL segment uploads across all streams.

Impact

Severity: HIGH

Throughput calculation:

• 50 concurrent streams × 3 qualities = 150 segments/10s = 15 segments/sec
• Each segment write takes ~200ms (50MB at 250MB/s NAS)
• 15 seg/sec × 0.2s = 3 workers busy on average
• Current capacity: 16 workers = 80 seg/sec max

This is acceptable for 200 concurrent streams but becomes a hard bottleneck at 500+ streams.

Files Affected

• /api/live_ingest.py (line 66)

Recommended Fix

1. Increase max_workers to 64 for write-heavy workloads
2. Consider using os.O_DIRECT flag to bypass page cache for large segments (reduces memory pressure)
3. Monitor thread pool queue depth with metrics

_io_executor = ThreadPoolExecutor(max_workers=64, thread_name_prefix="live_io")

Scaling Characteristics

• Current: 80 seg/sec max (hard limit)
• After fix: 320 seg/sec max

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🤖 Generated by automated performance review