"curator unreachable" was printed for every transient error, hiding whether a
single file's transfer stalled (ReadTimeout — curator is up, that stream is slow)
or curator itself is down (ConnectTimeout/ConnectionError) or errored (HTTP 5xx).
Those need completely different fixes, and we've been diagnosing the download
slowness blind.
Add _transient_reason(exc) → a specific label (HTTP <code>, else the exception
class: ReadTimeout / ConnectTimeout / ConnectionError / …) and use it in both
transient paths:
- downloader: "fetch failed job <id> (image <id>, ReadTimeout) — released, backing off"
- consumer: "submit failed job <id> (<reason>) — released, re-lease later"
Now the logs say which failure it actually is (and which image), so we can tell a
slow/stalled transfer apart from an unreachable curator. Build marker 2026-07-01.5.
Refs issue #1225.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Ttrj5P7upUTueSfoJcxEqa
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