music_library/backlog/completed/ml-169.3 - Phase-2-PubSub-subscription-lifecycle-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-169.3	Phase 2: PubSub subscription lifecycle audit	Done		2026-05-08 08:59	2026-05-19 08:50	audit ready		lib/music_library/records.ex lib/music_library/listening_stats.ex lib/music_library_web/live_helpers/record_actions.ex	docs/audits/phase2-pubsub-lifecycle/doc-25 - Audit-Report-PubSub-Subscription-Lifecycle-Phase-2.md	ML-169	medium	5000

Description

Audit all PubSub subscribe/unsubscribe pairs for correctness. Verify no stale subscriptions or double-subscription risks.

Pre-flagged concern: ListeningStats.subscribe() is called in mount by StatsLive.Index and ScrobbledTracksLive.Index but never unsubscribed. Phoenix.PubSub monitors PID for auto-cleanup, but double-subscription on LiveView reconnect is possible and needs verification.

Acceptance Criteria

• #1 Records.subscribe/1 and Records.unsubscribe/1 call sites audited — confirmed only called via manage_subscription/2 in Show LiveViews
• #2 manage_subscription/2 verified correct across all navigation paths (direct URL, browser back/forward, push_navigate, push_patch)
• #3 ListeningStats.subscribe() double-subscription risk on reconnect evaluated — either confirmed safe by PID monitoring or flagged with fix
• #4 Termination cleanup verified: Phoenix.PubSub auto-cleans on PID death confirmed; any manual unsubscribe gaps documented
• #5 Records.notify_update/1 broadcast sites audited against intended behavior (coordinates with Phase 3 worker audit)
• #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/phase2-pubsub-lifecycle/doc-25.

Key findings:

• 27 call sites across subscribe, unsubscribe, broadcast, and consumer handle_info verified
• All 8 subscribe sites have cleanup coverage (explicit unsubscribe or PID-death auto-clean)
• Pre-flagged ListeningStats.subscribe() double-subscription risk is a false positive: Phoenix.PubSub MapSet deduplicates per PID, and LiveView reconnect reuses the same PID within grace period
• No code changes required