A new enabled source is armed for run-until-done backfill (#693) but would sit
idle until the next scheduler tick (~60s). create_source now enqueues the first
walk right away (pending DownloadEvent + download_source.delay), skipping only
when the platform is in a rate-limit cooldown (the scheduler picks it up when
that clears). Disabled sources still don't dispatch.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Two concurrent Patreon walks could trip the server rate limit even with each
source pacing its own requests. The platform-cooldown handled the aftermath of
a 429; this adds the preventive half — a per-platform Redis lock so only one
Patreon walk runs at a time. Different platforms still run concurrently up to
the worker concurrency; only a second walk on the SAME serialized platform
waits.
download_source acquires fc:download_lock:<platform> (non-blocking) before the
run. On contention it re-enqueues itself with a short countdown (the pending
event stays — no new event, no log spam), bounded to ~15 min then runs uncapped
as a safety valve. The lock TTL sits just past the hard kill so a SIGKILL'd
worker auto-releases; a backfill chunk only holds it ~10 min, well under the
30-min DownloadEvent recovery sweep. A broker hiccup degrades to uncapped
(prior behaviour) rather than stalling downloads. SERIALIZED_PLATFORMS={patreon};
gallery-dl platforms are left uncapped (self-pacing subprocesses).
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
bvandeusen