002355ba40c02a4188d00d49e89c2214ae8bdbe8
2 Commits
| Author | SHA1 | Message | Date | |
|---|---|---|---|---|
fabi
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9666d74a46 |
fix(export): close all 13 findings from the multi-agent review
A 6-lens multi-agent review (103 agents; every finding adversarially verified by three
refute-by-default skeptics) confirmed the epoch redesign is sound — the core invariant
holds — and found 13 real defects around it. All are fixed here.
The redesign's invariant was re-verified and stands: an accepted upload is always in the
keepsake, and a downloadable keepsake always reflects the most recent release.
But a WEAKER adjacent invariant did NOT hold — "a downloadable keepsake reflects the
current content" — and that is the theme of the biggest fixes.
CONTENT REMOVAL NOW ALWAYS REACHES THE KEEPSAKE
Regeneration was wired only to host deletes. Ban, unban, guest self-delete and guest
comment-delete did not trigger it — yet the export query filters `is_banned = FALSE`,
so the pipeline already agreed that content must not be there. Ban someone for abusive
content after release and every guest kept downloading an archive containing it.
All five removal paths now invalidate and rebuild. `query_comments` also gained the
banned/hidden filter it was missing entirely (the ZIP had it; the viewer did not).
Each removal is now ATOMIC with its invalidation (one tx, models made executor-generic).
Previously the delete committed in its own tx and the regeneration in a second: a dropped
handler future between them left the taken-down photo permanently downloadable, and
nothing could notice — the keepsake still looked complete and the host could no longer
even find the upload to retry.
NO MORE TAKEDOWN STORM
Every removal spawned two uncancellable full exports. A superseded worker was INERT, not
STOPPED: it still ran every ffmpeg spawn and image resize and wrote a whole archive before
discovering it had lost. Five deletes left ten workers alive, each holding a
full-gallery-sized temp, in a 1 GB container.
Now: a debounce before `claim_job` (a superseded worker fails its claim and does ZERO
work, collapsing a burst into one export), plus `update_progress` — which already ran
exactly the right liveness predicate and threw the answer away — returning it so both file
loops bail the instant they are retired. Moderating a comment no longer rebuilds the
multi-GB ZIP either: the ZIP is media-only, so it is carried forward, with prune taught to
protect any file a live row still references.
AN ESCAPE HATCH
A failed export was terminal at runtime: release_gallery refuses an already-released event,
recovery only runs at boot, and there was no retry route — the only outs were restarting the
container or reopening uploads to every guest. Added POST /host/export/rebuild. Also widened
mark_failed's guard to `status IN ('running','pending')`: when claim_job itself ERRORED, the
row was still `pending`, so the failure was never recorded and the job sat at 0% forever.
SILENT INVALIDATION
Retiring the epoch 404s the download instantly, but nothing told the clients — guests kept
seeing an enabled download button through the whole rebuild. Now broadcasts an invalidation.
And the download was a top-level <a href>: a 404 (or a 429 from the per-IP export limit that
everyone on the venue WiFi shares) NAVIGATED THE USER OUT OF THE PWA onto raw JSON. It now
targets a hidden iframe, so an error response is harmless.
ALSO
- The HTML export still had the exists()-then-open TOCTOU the ZIP path was fixed to remove,
at three sites, two with a hard `?` that failed the ENTIRE viewer. It is reachable: the
compression worker hard-deletes an original when a transcode fails and can still be running
when the gallery is released.
- Crash-orphaned .tmp files were immortal (prune deliberately skips .tmp). Swept at boot,
where it is unambiguously safe.
- export_status read the epoch in one statement and used it in the next; now one query.
- DiskCache::snapshot IGNORED its path argument on a cache hit, returning whatever filesystem
was measured last. Latent only because both callers pass media_path — it would have silently
misreported the moment anyone measured the exports volume. Now keyed by path.
- Corrected two comments that asserted safety properties the code does not have (claim_job
does NOT prevent a retired-epoch claim — retirement is enforced at READ time; and a
multi-replica reap is NOT contained, it can corrupt the keepsake). Added a rollback runbook
to migration 014, the repo's first destructive migration.
TESTS
The regression guard for the headline FOR SHARE fix was probabilistic — it could pass on
broken code if the interleaving fell the wrong way. It is now STRUCTURAL: the upload is held
open mid-body with its pre-flight check already passed, so the release provably lands inside
the exact window. Verified 5/5 FAILING (201 instead of 403) with the fix reverted, 5/5
passing with it.
Verified: backend 40 tests, svelte-check 0 errors, e2e typecheck clean,
e2e 160 passed / 1 skipped on chromium-desktop.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
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fabi
|
8e906d7866 |
refactor(export): single epoch authority; fix upload-path TOCTOU losing photos
A deep investigative review of the export concurrency (four parallel adversarial
reviewers) found that three rounds of race fixes had been chasing the wrong bug, and
that the model itself was the root cause. This replaces the model and fixes the real
data loss.
THE ACTUAL BUG (upload path, not the state machine)
`upload` checked `uploads_locked_at` BEFORE streaming the body — minutes, for a large
video — then committed the row without re-checking. A release landing mid-upload let the
row commit AFTER the export snapshot: the photo appeared in the live feed and was
PERMANENTLY missing from the keepsake, with nothing to regenerate it. release_gallery's
comment claims to prevent exactly this; it never did. Every prior round fixed the DB
state machine, and the leak was upstream of it.
Fix: re-assert the lock under `SELECT ... FOR SHARE` INSIDE the commit tx. That row lock
conflicts with release_gallery's `UPDATE event`, so either the upload commits first (and
the release — hence the snapshot — is ordered after it) or the release wins and the
upload is rejected as `uploads_locked` (reversible; the client keeps the blob).
Regression test verified NON-VACUOUS: with the fix reverted it fails, reporting accepted
uploads missing from the keepsake.
THE MODEL (migration 014)
"Which generation is current?" had no single answer: it was assembled from three
separately-written pieces across two tables (`export_released_at`, a per-job
`release_seq`, and cached `export_{zip,html}_ready` flags). Keeping them in agreement
took ~10 hand-written guards; each review round found one more path that slipped through.
Now: ONE monotonic `event.export_epoch`, bumped in the same UPDATE as any change to
`export_released_at`. Each job carries a copy. Downloadable IFF
`released AND job.epoch = event.export_epoch AND status = 'done'` — readiness DERIVED,
never stored. A retired-epoch worker is INERT BY CONSTRUCTION: losing a race can no
longer corrupt state, only waste work.
Deleted: both ready-flag columns, both ready-flip blocks, `if ready { continue }`, the
reopen seq-bump, open_event's transaction, and the cross-table claim guard.
That last one was also UNSOUND: under READ COMMITTED, a blocked UPDATE re-evaluates its
WHERE against the updated target row but answers subqueries on OTHER tables from the
original snapshot — so the previous `EXISTS (SELECT ... FROM event ...)` claim guard
could admit a claim against an already-reopened event while RETURNING the post-bump seq.
Every guard is now same-row (`epoch = $n`), which EPQ re-evaluates correctly.
OTHER REAL DEFECTS FIXED
- release_gallery committed the release and THEN awaited the enqueue inside the handler
future. Axum drops that future on client disconnect → event released, uploads locked,
ZERO export_job rows, host unable to retry ("bereits freigegeben"), restart-only
recovery. Now one tx; workers spawn (detached) after commit.
- No flush/fsync before the tmp→final rename. async_zip's close() never flushes the inner
file and tokio's File drop DISCARDS write errors — so a full disk silently produced a
truncated archive that was then marked done and published, after which the last good
generation was pruned. Now flush + sync_all, which also surfaces ENOSPC.
- Download read the ready flag and the file path in TWO queries; a reopen between them
served a keepsake that should 404. Now one read through the `export_current` view.
- `if !src.exists() { continue }` then `open()?` — a TOCTOU that turned a tolerated gap
into a hard failure of the ENTIRE keepsake (unretryable while released). Now open-first,
warn, and skip.
- Recovery was flag-driven and never checked the disk: a `done` row whose archive was gone
was a permanent dead end needing manual DB surgery. Now verifies the file and re-arms.
- Temp files/dirs leaked on every error path (the leak is what fills the disk that
corrupts the next archive). Now cleaned up.
- Export archives were not event-scoped (`viewer_tmp_` already was), so a second event
would collide on paths and one event's prune would delete another's live keepsake.
- Host deletes after release never regenerated the keepsake — a photo removed on request
lived on in the archive forever. Now bumps the epoch and rebuilds without it.
- claim_job swallowed DB errors as "someone else won", stranding a job pending at 0%.
- export_status reported retired-epoch rows (a progress bar that never moves).
- The startup sweep's single-instance assumption is now documented, not hidden.
Verified: backend 40 tests, svelte-check 0 errors, e2e typecheck clean,
e2e 160 passed / 1 skipped on chromium-desktop (incl. 2 new regressions; the
upload-acceptance one confirmed to fail without the fix).
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
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