Three prod-observed download bugs, root-caused from a frozen prod queue with the
worker pinned at 100% CPU:
- ReDoS in normalize_title: _TRAILING_HASHTAGS had two overlapping unbounded
quantifiers around the required letter, so a Facebook title with a long hashtag
cluster that is NOT at the end ("... #a #b #c | Page") backtracked catastrophically.
It runs inside the yt-dlp progress hook holding the GIL, so one such download froze
the whole worker (and could stall feed enrichment too - sync/videos.py calls it).
Rewrite with a zero-width "has a letter" lookahead + a possessive tag body: one
unambiguous split, nothing to backtrack. 40-tag stress case: ~0.1ms.
- Reddit download killed by a cosmetic thumbnail convert: yt-dlp's
FFmpegThumbnailsConvertor runs "-bsf:v mjpeg2jpeg" on a JPEG-served-under-a-.png-name
(Reddit) and fails; being a postprocessor, it failed the WHOLE download even though
the media was fine. Drop it and produce the <base>.jpg poster/og:image ourselves via
editmod.thumbnail_to_jpg (plain ffmpeg decode->mjpeg, best-effort -> ensure_poster
cuts a frame on failure). The FB Messenger / MS Teams share preview keeps working
(posters verified as real JPEGs).
- classify: map "authentication is required" (Reddit's auth wall) to login_required
instead of unknown, so the UI explains it rather than offering a pointless retry.
Tests: ReDoS-timing + numeric-marker regression, the Reddit classify case, and
thumbnail_to_jpg (real JPEG out / None on bad input, never raises).
- redownload now ALWAYS rebuilds into a fresh private asset instead of ever reusing a shared
cached file: the cache sig is salted with job_id + current asset_id, so the fork is distinct
from both the dedup pool and the job's own current asset. This resolves the co-held silent
no-op (finding #1) — a shared asset is left intact for its other holders while THIS job
re-fetches its own copy. Resolving the fork BEFORE releasing the old hold (and the unique
salted key) also removes the IntegrityError-rollback-after-file-delete window (finding #2).
- format_sig gains an optional `salt` for that fork identity.
- titles: don't consume the space after `|`, so a "stats | #hashtags" remainder keeps the
leading whitespace _TRAILING_HASHTAGS needs — and fall back to the prefix+hashtag-stripped
text, so neither the stats nor the SEO hashtags are resurrected when a title empties (#3).
- worker: early-fill asset.title falls back to the video id so a title that cleaned to empty
doesn't show a blank card while downloading (#5).
- Tests for the salt fork and the hashtag-remainder case.
(Finding #4 — quota on re-download — intentionally not changed: a re-download reuses the
existing job and re-fetches ~the same bytes, so calling check_enqueue would wrongly reject on
the job-count cap while footprint is unchanged.)
- redownload: never clobber a co-held (deduped) asset. Drop the force-reset-to-pending;
_release_asset already deletes+recreates a solo asset (genuine re-fetch), while a shared
ready asset is left intact and the re-queued job re-points to it via _finish_from_cache —
so one user's re-download can't delete another's file mid-serve (finding #1).
- redownload: reset queue_pos to the tail so a re-download doesn't front-run newer queued
jobs on the worker's `ORDER BY queue_pos` claim (finding #3). Made service.next_queue_pos public.
- formats: video-only mp4 selector prefers every video-only option before any progressive
`best`, so a "Video only" download stays audio-free whenever a video-only stream exists (#2).
- titles: a title that is only the engagement prefix no longer resurrects the stripped stats
(return the stripped text / empty, not the raw) (#4).
- worker: probe the file's duration when yt-dlp gave none, so a long re-encode shows real
progress instead of a frozen 0% (#5); tighten the ensure_browser_playable docstring to its
actual mp4-profile scope (#6).
Mini-epic "Downloads correctness & UX" (S1–S3), on top of the iOS-AV1 + 720p fixes.
S1 — naming & titles:
- ASCII-fold on-disk dir/file names AND the served (Content-Disposition) filename: no
spaces (underscore-joined), no accents (á→a, ő→o, ß→ss), pure ASCII — portable and free
of the `?` mojibake accented names show in non-UTF-8 tools. (Forward-only; existing files
clean up via re-download.)
- Strip a leading social engagement prefix ("1.6M views · 66K reactions | …") from titles.
S2 — universal browser playability (generalizes the iOS re-encode):
- ensure_browser_playable guarantees the stored file is H.264 + AAC/MP3 in mp4 — the only
combo every browser decodes. Re-encode just the offending stream(s) (video for AV1/VP9/HEVC,
audio for Opus/etc), or remux when only the container is wrong. Gated on the mp4 compat
profile (an explicit vcodec / non-mp4 custom profile opts out).
S3 — force re-download (preserves share links):
- POST /downloads/{job_id}/redownload keeps the job row so its public DownloadLink survives
and resolves to the freshly-downloaded file; deletes the old file and re-fetches under the
current rules. A failed re-download leaves the job in error (the intended broken-link case).
- Library "Re-download" action (icon + confirm), api method, hu/en strings.
Tests: naming/title-strip (test_naming), browser_transcode_flags matrix; existing
download_filename expectation updated for the underscore policy.
Noisy YouTube titles are cleaned for display + storage, raw kept in videos.original_title:
- app/titles.normalize_title: strip emoji/symbols (keep accents), remove trailing SEO hashtag
clusters (keep numeric #3 episode markers), context-aware de-shout (mostly-ALL-CAPS titles ->
Title Case with an acronym whitelist + function-word lowercasing; otherwise only long all-caps
words), collapse repeated punctuation
- applied at enrichment (sync/videos.py) and in the download worker (ad-hoc yt-dlp titles);
catalog downloads inherit the normalized title automatically
- migration 0039: add original_title, preserve raw, rewrite title (generated search_vector
regenerates); reversible via original_title
Backfill on localdev: 122115/273417 titles normalized in ~2 min. Verified in the feed + on
real messy samples (emoji/de-shout/hashtags), accents + acronyms (PS5/AI/USA/PC) preserved.
peter