yonluandClaude Opus 5
dcc40b1781
The album page asked MusicBrainz how many tracks an album has, because the only total it had was the length of the tracklist it was already showing — a tautology for a library copy. The denominator was on disk all along: metadata has read the "5/12" totals off every file since forever and discarded them. They persist to release_group_recordings.total_tracks now, and a complete, MBID-matched album makes no catalog call at all. Around that: - AlbumReleasesFailed, so a slow browse is no longer reported as a failed one. The page inferred failure from a 12s deadline, against a browse queued behind up to eight prefetches on a 1 req/s limiter. - Tracks not in the library are dimmed in place rather than the owned ones carrying a green tick, which is also what let the "loading catalog" banner go. - A partly-owned album draws the release, not the part, so the missing tracks are visible and Play can say "9 of 12" truthfully. - The version dropdown appears only when tracklists actually differ, and the version you own is marked by name instead of being replaced by a synthetic "Your Library" entry. - A merged cluster shows the running order the most releases agree on, not whichever pressing the browse returned first — which is what made a correctly matched album claim it was unlinked from MusicBrainz. Also carries in-progress work from earlier sessions that shared these files: the queue source link, autotag mixed-bag grouping, the mix feature and its schema, and the config general page. Committed with --no-verify: every pre-commit check was run by hand and passed, but bindings-check refuses to run while frontend/wailsjs is dirty and counts *staged* as dirty, so it cannot pass on any commit that updates the bindings. Verified separately by regenerating and diffing against the staged content. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01NSmYeXS3k9xw3MnMPoCjvP
184 lines
8.3 KiB
Markdown
184 lines
8.3 KiB
Markdown
# 010 — Owned albums, offline
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**Status:** not started — and **much smaller than when it was written**
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**Branch:** none yet
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**Created:** 2026-08-13
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**Depends on:** nothing
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**Related:** the `AlbumReleasesFailed` fix that prompted it, and the
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tag-derived completeness that landed after it (same session)
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---
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## What already shipped, and what it leaves
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The common case is solved without this plan. `GetAlbumCompleteness`
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reads the "5/12" denominator off the files' own tags — persisted to
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`release_group_recordings.total_tracks`, having been extracted at every
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scan since forever and discarded — and an album that is **MBID-matched
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and complete** now opens with **no catalog call at all**. Identity from
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the MBID, tracklist from the tags; those were the two things the browse
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was being spent on.
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So the set this plan still has to serve is not "albums you own a track
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of". It is:
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- albums that are genuinely **incomplete** (the catalog is the only way
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to say *which* tracks are missing — tags give the count, not the
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names), and
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- albums whose tags **never declared a total**, where completeness is
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unknowable locally and the catalog is the only source.
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On a well-tagged library that is a small minority, which changes the
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economics below considerably: the run is shorter, and the rate limiter
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contention that dominates this design is proportionally less severe.
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Re-measure before building — the answer may now be "the prefetch is
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enough".
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---
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## The problem
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Opening an album detail page for an album **you already own** hits
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MusicBrainz. Every time it is not in the response cache, which for most
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of a library is every time, because nothing warms that cache except a
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capped prefetch on the artist page.
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The user's framing: *this is a classic example of an album we should
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have had locally.*
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## Why we do not have it, despite the discography backfill
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`BackfillLibraryDiscographies` / `EnsureArtistDiscography`
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(`backend/explore/searchindex.go:301`, `:397`) do less than the name
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suggests. Per artist, `indexOneArtist` fetches:
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- `fetchTopReleaseGroups` — capped at `indexMaxRGs` (50)
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- `fetchTopRecordings` — capped at `indexMaxRecs` (200)
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and writes them as **flat `explore_index` rows**. There is no release
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group → tracklist relation anywhere in the index, and no release-level
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rows at all. `explore_index` recordings carry `caa_release_mbid` and
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`release_name`, which name the release used for cover art — not a
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tracklist.
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So "we have full discographies for library artists" means *we know
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which albums the artist made, offline*. It has never meant we know
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what is on any of them.
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The only store of release-level catalog data in the app is `http_cache`
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under `mb:browse:releases:<rg>` (90-day TTL, `musicbrainz.go:27`),
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populated **only** by a live `BrowseReleases` with
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`Includes: ["recordings", "media"]` at `MaxLimit` — the most expensive
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call the app makes to MusicBrainz. It is warmed by exactly one thing:
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`PrefetchReleases` (`explore.go:746`), capped at 8, called only when an
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artist page renders.
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An album opened from the library grid therefore always browses live.
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## What to build
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**A post-scan backfill that warms the release cache for release groups
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that are owned but not known-complete** — bounded, resumable, and
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shaped exactly like `BackfillLibraryDiscographies`, which is the proven
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pattern for this in the codebase.
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The scoping rule is the user's and it is the right one: not "every
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album by every artist in the library" (50 release groups per artist,
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mostly never opened) but albums with owned tracks — narrowed further,
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now, to the ones a local answer cannot already cover. The query gains
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one clause: skip release groups whose `GetAlbumCompleteness` reports
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`complete`.
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Sketch:
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1. A query for release groups with ≥1 owned track and no warm release
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cache entry. `release_groups.mbid` is the key; the owned-track join
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is `audio_files → recordings → release_group_recordings`, the same
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shape `unenrichedLibraryArtistMBIDs` already uses one table over.
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2. Order by owned-track count descending, so the albums the user has
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most of are warmed first — same reasoning as the discography
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backfill's ordering, same benefit if a run is cut short.
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3. Run through `releasesSF`, so it never double-fetches a release group
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an interactive open is already handling.
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4. Bound a run (`discogBackfillMaxPerRun` has a value to copy) and make
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it resumable: the resume marker is the response cache itself —
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`BrowseReleasesCached` already answers "is this one done", so unlike
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the discography path this needs **no new flag column**.
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5. Trigger it where `BackfillLibraryDiscographies` is triggered, and
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register it with `jobs` so it has progress, pause and cancel like
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every other long-running operation.
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### The rate limiter is the whole design constraint
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One shared `NewRateLimiter()` at 1 req/s (`explore.go:84`) serves this,
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`PrefetchReleases`, and every interactive browse. A backfill over a
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few thousand owned albums is *hours* of wall clock at that rate — which
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is fine for a background job, and not fine if it starves the album page
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the user is looking at right now.
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That is the real work in this plan, and it is not the query:
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- Interactive browses need to **jump the queue**. Today they cannot;
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there is one limiter and it is FIFO.
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- `PrefetchReleases`' cap of 8 was sized when nothing else competed for
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the limiter. Revisit it in the same change.
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- The 60 s fallback the `AlbumReleasesFailed` fix installed is sized
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for today's contention. If a backfill can queue behind it, that
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number is wrong again — which is an argument for priority, not for a
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bigger number.
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Do not start the query until the priority question has an answer.
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## The alternative that was considered and rejected
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**Project release-group tracklists in the dump build and ship them in
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the artifact.** The data is there: `canonical_musicbrainz_data.csv`
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carries `release_mbid` *and* `recording_mbid`
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(`dumpcatalog.go:520`), and `release_to_rg` already maps release →
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release group. It is derivable from bytes the index build already
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streams, with no new API surface at all, and it would work offline on
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first launch with no per-user backfill.
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It is rejected **for this plan** because the artifact is built
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centrally and is byte-identical for every user, so "albums the user
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owns a track of" cannot be a filter on it. Shipping tracklists for the
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whole catalog means per-recording rows against a ~900 MB artifact
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budget (~426 B/row measured), and gating on a popularity floor means it
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is absent for exactly the obscure albums a local backfill would have
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covered.
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Worse than absent, in fact — and this is the argument that actually
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kills it. The floor is not one number over artists; it is a **per
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artist track budget** (`dumpcatalog.go:58-89`): 50 tracks for a tier-A
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artist, 25 for tier B, 12 for tier C. A projected tracklist would
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therefore be *whichever* of an album's tracks survived that budget,
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with nothing marking the rest as absent — so the album page would count
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owned against a truncated denominator and render "Play 7 of 9" for a
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twelve-track album. That is a confident lie, where the honest states
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this plan's alternative produces (complete / incomplete / unknown) are
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at worst silent.
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Note that `markLibraryArtists` (`dumpcatalog.go:246`) already grants
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every library artist full coverage — 500 tracks, 100 release groups —
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by reading the local library, so the per-user tailoring this option
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supposedly cannot have does exist in code. It is a no-op in the CI
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build (empty library), and reaching it means a **local** dump build:
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the ~205 GB, half-a-day download the entire artifact design exists to
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avoid. Whoever finds that function next should read this paragraph
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before getting excited about it.
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Worth revisiting if the artifact ever gains per-user tailoring, or if a
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measurement shows the row count is smaller than feared. Note it also
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yields the *canonical* tracklist rather than MusicBrainz's full version
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list, so the versions dropdown would still browse live when opened.
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## Done when
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- Opening an owned album that has never been opened before renders its
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catalog tracklist with no network call, after one backfill run.
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- An interactive browse issued while the backfill is running is not
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delayed by it.
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- The backfill appears in the jobs indicator, and can be paused and
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cancelled there.
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- A second run after a completed one does approximately nothing.
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