bvandeusen
7cfaafd360
Closes the last deferred follow-up from #357. The library_changes table is the append-only change log that drives /api/library/sync's delta semantics — every mutation (scanner upsert, like, playlist edit, track delete) writes one row. Without a retention policy the table grows unbounded; the original migration (0025) called out the follow-up explicitly. New goroutine: sync.Compactor runs daily, deletes rows where changed_at < now - 30 days. Logs a row count when non-zero so operators can see compaction activity in the journal. First tick fires on startup so a process that hasn't been compacted in a while catches up immediately. 30-day retention matches the offline-mode spec (docs/superpowers/specs/2026-05-09-flutter-offline-mode-design.md). Clients with a cursor older than that hit the existing 410 fallback path and resync from scratch. Imported as syncpkg in main.go to follow the existing convention (see internal/library/scanner.go). Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
86 lines
2.8 KiB
Go
86 lines
2.8 KiB
Go
// Periodic compactor for the library_changes log (#357 deferred
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// follow-up). Every mutation in the library writes one row, so the
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// table grows unbounded without a retention policy. This worker
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// trims rows older than CompactorRetention on a daily tick.
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//
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// Why daily / 30 days: Flutter clients track a per-app cursor and
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// pull deltas from the last seen id. As long as a client checks in
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// at least once per retention window, it never sees the cursor go
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// stale. Clients that drop offline longer than that hit the /api/
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// library/sync 410 fallback and do a full resync. 30 days is the
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// established norm for similar offline-cache delta logs and matches
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// the spec at docs/superpowers/specs/2026-05-09-flutter-offline-mode-design.md.
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package sync
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import (
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"context"
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"log/slog"
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"time"
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"github.com/jackc/pgx/v5/pgtype"
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"github.com/jackc/pgx/v5/pgxpool"
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"git.fabledsword.com/bvandeusen/minstrel/internal/db/dbq"
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)
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// CompactorRetention is the age past which library_changes rows are
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// dropped. Mutable for tests; production runs should not change it
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// without considering the corresponding client cursor-stale fallback.
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var CompactorRetention = 30 * 24 * time.Hour
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// CompactorInterval is how often the worker checks. Daily is enough —
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// the table grows on the order of a few thousand rows/day for an
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// active library, well below a size where intra-day trimming matters.
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var CompactorInterval = 24 * time.Hour
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// Compactor is a background worker that periodically deletes
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// library_changes rows older than CompactorRetention.
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type Compactor struct {
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pool *pgxpool.Pool
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logger *slog.Logger
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interval time.Duration
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}
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// NewCompactor builds a compactor with production defaults.
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func NewCompactor(pool *pgxpool.Pool, logger *slog.Logger) *Compactor {
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return &Compactor{
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pool: pool,
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logger: logger,
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interval: CompactorInterval,
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}
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}
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// Run blocks until ctx is cancelled, ticking every c.interval.
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// Fires one tick immediately on startup so a long-running process
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// that hasn't been compacted in a while catches up.
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func (c *Compactor) Run(ctx context.Context) {
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c.tickOnce(ctx)
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t := time.NewTicker(c.interval)
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defer t.Stop()
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for {
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select {
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case <-ctx.Done():
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return
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case <-t.C:
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c.tickOnce(ctx)
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}
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}
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}
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// tickOnce deletes rows older than CompactorRetention and logs the
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// row count. Errors are logged at WARN; we never abort the loop on
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// transient DB failures.
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func (c *Compactor) tickOnce(ctx context.Context) {
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cutoff := pgtype.Timestamptz{Time: time.Now().Add(-CompactorRetention), Valid: true}
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rows, err := dbq.New(c.pool).DeleteOldLibraryChanges(ctx, cutoff)
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if err != nil {
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c.logger.Warn("library_changes compactor: delete failed", "err", err)
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return
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}
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if rows > 0 {
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c.logger.Info("library_changes compactor: trimmed rows",
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"count", rows, "older_than", CompactorRetention)
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}
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}
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