Routine subscription polls walked the entire post history every tick
even when nothing had changed, because gallery-dl's default `skip: True`
continues iterating archived posts. A creator with ~550 archived posts
(Knuxy patreon) saturates the 870s wall-clock cap before completing,
even with zero downloads needed. Plus, a tier-limited run that
downloaded hundreds of files but ran out the clock should be a
warning, not an error.
Two coupled changes, both operator-flagged 2026-06-01:
* **Tick mode (default, cron polls).** New `TICK_SKIP_VALUE = "exit:20"`
asks gallery-dl to exit after 20 contiguous archived items. Fresh
subscriptions + new-content cases still walk normally; established
subscription with zero new content exits in ~30s of HEAD requests
instead of pegging the timeout. 20 (not 5) gives headroom against
paywall warnings interleaving with archived items.
* **Backfill mode (explicit, operator-triggered).** Sticky for N runs
via new `Source.backfill_runs_remaining` (alembic 0031). While > 0,
downloads use `skip: True` + 1800s timeout. Auto-decrements per run
with early-reset to 0 when a clean run finds zero files (queue
drained). N defaults to 3 — multiple runs give the system enough
budget to finish a deep walk across timeout boundaries. New
`POST /api/sources/{id}/backfill` arms the source; "Deep scan"
button on each SourceRow (chip shows remaining count) wires it.
Plus partial-success classifier: non-zero gallery-dl exit + ≥1 file
downloaded + no source-level error fires `ErrorType.PARTIAL`, which
download_service maps to `status=\"ok\"`. The run did real work; the
next tick continues via gallery-dl's archive. No more red events for
"timed out mid-walk after downloading 300 files."
Retires `SourceConfig.skip_existing` — skip value is now derived from
the source state and passed as a separate `skip_value` parameter
through download() / _build_config_for_source(). `GD_DEFAULTS` drops
the now-dead key (was inert data after this refactor).
Tests cover:
* tick + backfill skip-value emission in _build_config_for_source
* PARTIAL classifier branch + TIER_LIMITED-wins-over-PARTIAL ordering
* SourceService.set_backfill_runs validation + persistence
* /api/sources/{id}/backfill 200/400/404 paths
* download_service auto-decrement / auto-reset / tick-mode-no-touch
* PARTIAL → status=ok in the orchestrator (no consecutive_failures bump)
Three coupled operator-reported pains from the 2026-05-31 download
event audit:
1. `[patreon][warning] Not allowed to view post N` was bubbling up as
an error event, bumping consecutive_failures and parking the source
in "needs attention." The classifier's tier-gated branch was gated
on `return_code in (1, 4)`. Gallery-dl returns a different exit
code for mixed-failure runs (e.g. paywall warnings + a missing
yt-dlp dep flipping the exit bits), so the branch never fired and
the path fell through to UNKNOWN_ERROR. Widen the gate: when no
source-level error fired AND tier-gated warnings are present,
classify as TIER_LIMITED regardless of return code.
2. Knuxy event #38275 (2026-05-31) ran 30 min and finalized with
"stranded by recovery sweep (no terminal status after time_limit)"
+ empty stdout/stderr. Root cause: subprocess.run timeout (900s)
and Celery soft_time_limit (900s) raced; when Celery won, SIGKILL
wiped the in-memory captured output and the DownloadEvent ended up
empty-logged 18 minutes later when the sweep finalized it. Drop
gallery-dl's default subprocess timeout to 870s — a 30s margin
shy of Celery's soft limit — so subprocess.TimeoutExpired always
wins the race and captures the partial stdout/stderr via the
existing handler.
3. `[downloader.ytdl][error] Cannot import yt-dlp or youtube-dl` was
firing on every video attachment, causing per-item download
failures that masked legitimate tier-gated classification.
Add yt-dlp>=2025.1 to requirements.txt. Once it's in the image,
video posts download normally and the per-item failure noise
disappears.
Tests added:
- pure tier-gated stderr with exit code 128 → TIER_LIMITED + success
- mixed tier-gated + yt-dlp + per-item failures → still TIER_LIMITED
Operator-flagged 2026-05-30: "the fail state of timeouts doesn't show
anything other than that the task timedout and was cleaned up. I can't
tell why it ran over or if it was stuck failed or there was just that
much to get."
The TimeoutExpired branch was returning a DownloadResult with no stdout,
no stderr, no files_downloaded, and a generic "Download timed out after
N seconds" message — even though subprocess.TimeoutExpired carries the
partial output gallery-dl emitted before being killed.
Now:
- Capture e.stdout / e.stderr (coerced str if bytes; "" if None).
- Count files_downloaded from partial stdout via _count_downloaded_files.
- Surface a tail-of-stderr hint in error_message so the UI summary tells
the operator at a glance whether it was "lots of content" (high count,
clean stderr), "stuck retrying" (any count, 429-spam stderr), or "hung
silent" (zero count, "no stderr output").
- Promote error_type to RATE_LIMITED when the partial stderr matches
RATE_LIMIT_PATTERNS — gallery-dl spinning on retries through the whole
900s window is the timeout-shaped tail of a real rate limit, and the
platform cooldown should kick in for the same reason.
Existing test_download_timeout strengthened to also assert empty-partial
case stays correctly TIMEOUT-classified with no preserved output.
New test_download_timeout_preserves_partial_output_and_classifies covers
the rich-partial-output → RATE_LIMITED promotion path.
DownloadEvent.metadata already flows stdout/stderr/run_stats from
DownloadResult via _phase3_persist — no UI change needed; the existing
DownloadDetailModal will surface the captured output automatically once
the build redeploys.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
bvandeusen