The scan fingerprints only bytes it has not seen, so everything imported
before fingerprinting existed, and any row derived by an older
fingerprintVersion, needs a pass of its own.
That pass is a background worker, not a stage in RunScan. RunScan runs
at boot and then every 12h, and an in-flight scan older than an hour is
reaped and a second started beside it. A stage would have to stop inside
the hour: a few hundred decodes a run, so about a month for a 50k-track
library. It would also hold the run in flight and answer manual
rescans with 409 while it worked.
FingerprintBackfillWorker runs once at start, then hourly. Nothing a
pass does (error or panic) can stop the next tick. A pass walks tracks
with no fingerprint or a stale version, skipping missing tracks,
keyset-paged on id. The cursor is what lets a pass end: an inconclusive
attempt writes no row, so a file that keeps timing out would otherwise
be re-listed and retried forever. Two decodes at a time, deliberately:
they compete with transcoding for CPU and with streaming for the mount.
storeFingerprint is now one package function shared by the scan and
the worker, and reports whether the attempt was fingerprinted,
rejected, inconclusive or failed to store.
Progress is a live gauge on the Admin scan card, served by
GET /api/admin/library/fingerprints: fingerprinted / rejected / pending
of total, with missing tracks excluded so it can reach the end.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01SQ31KQpYbStyK5y58UmPLH
Two identities per track, because they answer different questions:
- audio_stream_sha256: SHA-256 of the ENCODED audio packets
(ffmpeg -map 0:a -c:a copy -f hash). Equal means identical audio
whatever the tags say. Measured against the #3885 pair: the two WWW
files hash identically here and differently as whole files. Packets
rather than decoded samples, so an ffmpeg upgrade cannot silently
change every stored hash, and nothing is decoded.
- chromaprint: fpcalc -raw -signed. The same recording at another
bitrate or codec, for the acoustic tier.
fpcalc ships in the image (libchromaprint-tools); shelled out because
CGO_ENABLED=0 rules out bindings.
Stored in a track_fingerprints table rather than on tracks: eight
queries read tracks with SELECT *, including album pages, search and
the Subsonic surface, and a ~4 KB array there would be de-TOASTed on
every one of them.
The scan fingerprints only bytes it has not seen (a new path, or mtime
past the row's). A tag-repair pass leaves fingerprints alone, and
unchanged files with no fingerprint are the backfill's job (#3908).
Folding that into the skip check would re-decode the whole library on
the first scan after upgrade and push a sync change per track.
A failure that says nothing about the file (timeout, cancelled scan,
tool not installed) is never stored, and on changed bytes it removes
the old row. A tool that rejects the file stores NULL at the current
version, so the backfill does not retry it every boot.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01SQ31KQpYbStyK5y58UmPLH