Severity: Low
Observation
DownloadFilesAsync emits a cloudfetch.download_slot_acquired event every time a download slot is acquired from the parallelism pool. Under CloudFetchStressTests (24-file / 241MB downloads) the event fires 252 times.
But the event carries no wait_duration_ms tag — so it's impossible to tell whether a slot was acquired immediately or whether the call blocked waiting for another download to finish. Under high parallelism, this is exactly the metric you'd want to diagnose "downloads are slow because they're queued."
Suggested fix
Capture Stopwatch around slot.WaitAsync() and add wait_duration_ms tag to the cloudfetch.download_slot_acquired event. Also consider queue_depth (count of pending downloads).
Evidence
Traces.CloudFetchStressTests.20260527_154205/ — 252 cloudfetch.download_slot_acquired events, none with wait_duration- Tier 1 finding: CloudFetchMemoryBufferManager has no dedicated span / event for back-pressure either
Severity: Low
Observation
DownloadFilesAsyncemits acloudfetch.download_slot_acquiredevent every time a download slot is acquired from the parallelism pool. UnderCloudFetchStressTests(24-file / 241MB downloads) the event fires 252 times.But the event carries no
wait_duration_mstag — so it's impossible to tell whether a slot was acquired immediately or whether the call blocked waiting for another download to finish. Under high parallelism, this is exactly the metric you'd want to diagnose "downloads are slow because they're queued."Suggested fix
Capture
Stopwatcharoundslot.WaitAsync()and addwait_duration_mstag to thecloudfetch.download_slot_acquiredevent. Also considerqueue_depth(count of pending downloads).Evidence
Traces.CloudFetchStressTests.20260527_154205/— 252cloudfetch.download_slot_acquiredevents, none with wait_duration