music_library/backlog/completed/ml-169.1 - Phase-3-Concurrent-state-change-safety-audit.md

id, title, status, assignee, created_date, updated_date, labels, dependencies, references, modified_files, parent_task_id, priority, ordinal

id	title	status	assignee	created_date	updated_date	labels	dependencies	references	modified_files	parent_task_id	priority	ordinal
ML-169.1	Phase 3: Concurrent state change safety audit	Done		2026-05-08 08:59	2026-05-19 08:50	audit ready		lib/music_library/worker/ lib/music_library/records.ex lib/music_library_web/components/record_form.ex	docs/audits/phase3-concurrent-state-safety/doc-26 - Audit-Report-Concurrent-State-Change-Safety-Phase-3.md	ML-169	medium	4000

Description

Audit whether background Oban worker record mutations are safely reflected in LiveView state without data corruption or stale UI.

Key risks to investigate:

1. Worker-broadcast consistency: do all record-modifying workers call Records.notify_update/1?
2. Form edit + background update race: editing in RecordForm modal while worker updates record
3. Double-update handling: two workers updating same record simultaneously

Acceptance Criteria

• #1 Every record-modifying Oban worker audited for notify_update/1 call after success (RefreshCover, PopulateGenres, GenerateRecordEmbedding, RecordRefreshMusicBrainzData, ImportFromMusicbrainzRelease, ImportFromMusicbrainzReleaseGroup, all RecordAll* batch workers)
• #2 Workers that do NOT modify records confirmed as correctly NOT broadcasting (PruneAssets, ApplyScrobbleRules, all ArtistRefresh*, etc.)
• #3 Form edit + background update race evaluated: trace what happens when RecordForm holds stale @record assign while worker broadcasts {:update, record} to parent Show page
• #4 Double-update race evaluated: confirm both handle_info calls apply safely (workers touch different fields, second wins)
• #5 ArtistLive.Show confirmed as intentionally not handling {:update, record} (artist updates use ArtistLive.Form → {:saved, artist_info} path)
• #6 Findings report written as a Backlog.md document with file:line references, severity ratings, and fix recommendations

Implementation Notes

Audit complete. Report written at docs/audits/phase3-concurrent-state-safety/doc-26.

Key findings:

• All 8 record-modifying workers correctly broadcast notify_update or broadcast_index_changed
• 18 non-record workers confirmed as correctly NOT broadcasting
• MEDIUM finding: form edit + background update race — handle_info({:update, record}) overwrites @record during :edit. Recommended fix: add live_action guard to both Show LiveViews.
• Double-update race is SAFE: Ecto changesets only UPDATE SET changed fields, SQLite serializes writes
• ArtistLive.Show confirmed intentionally not handling {:update, record}