fix: deduplicate concurrent sync state requests

[ryokun6]

Problem

Multiple duplicate GET /api/sync/state?domain=... requests are fired concurrently for the same domain. From the server logs, the same domain (e.g. calendar, songs, contacts) was being fetched 3–5 times simultaneously:

08:54:52 → GET /api/sync/state?domain=calendar   ×3
08:54:52 → GET /api/sync/state?domain=songs      ×3
08:54:52 → GET /api/sync/state?domain=contacts   ×3
08:55:05 → GET /api/sync/state?domain=videos     ×5
08:55:05 → GET /api/sync/state?domain=calendar   ×5

Root causes

1. No in-flight deduplication on fetchRedisStateDomainSnapshot: When the batch check (checkRemoteUpdates), the realtime Pusher handler (handleRealtimeDomainUpdate), and upload pre-merge reads (uploadRedisStateDomain) all request the same domain concurrently, each fires a separate HTTP request.

2. Rapid-fire requestCloudSyncCheck() from component mounts: Multiple components (Calendar, Stickies, Contacts) call requestCloudSyncCheck() synchronously on mount, each triggering the sync check listener.

Fix

1. In-flight request deduplication for fetchRedisStateDomainSnapshot (cloudSync.ts)

Added a Map<RedisSyncDomain, Promise> that caches in-flight requests. When multiple callers request the same domain concurrently, they share a single HTTP request. The cache is cleared when the request settles (success or error), so subsequent calls get fresh data.

2. Debounce requestCloudSyncCheck() (cloudSyncEvents.ts)

Replaced the synchronous dispatch with a setTimeout(fn, 0) coalescing pattern. All requestCloudSyncCheck() calls within the same event-loop tick are batched into a single listener notification.

Testing

• bun run build — compiles successfully
• bun run test:unit — all 89 tests pass

  

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Last updated at: 2026-03-15 09:18:35 CET