Fix race condition causing syncing loaders to get stuck #2412

2025-06-26T03:16:15+08:00

zachgoll commented

2025-06-26 03:16:15 +08:00

(Migrated from github.com)

Problem

The sync status monitor was experiencing a race condition that caused syncing loaders to appear stuck even after syncs completed.

Root Cause

The issue occurred because:

When a sync changed state, handle_transition would update family.latest_sync_activity_at
This timestamp is used in the cache key for SyncStatusMonitor
However, the timestamp update happened inside the database transaction
Other connections could read the old timestamp value before the transaction committed
This caused them to use a stale cache key and retrieve outdated sync status

Solution

Move the timestamp update to an after_commit callback. This ensures:

The sync state change is fully committed and visible to all database connections
The timestamp is updated only after the commit
Any subsequent cache reads will see the new timestamp and invalidate properly

This eliminates the race condition while maintaining all existing functionality that depends on these timestamps for cache invalidation.

## Problem The sync status monitor was experiencing a race condition that caused syncing loaders to appear stuck even after syncs completed. ## Root Cause The issue occurred because: 1. When a sync changed state, `handle_transition` would update `family.latest_sync_activity_at` 2. This timestamp is used in the cache key for `SyncStatusMonitor` 3. However, the timestamp update happened inside the database transaction 4. Other connections could read the old timestamp value before the transaction committed 5. This caused them to use a stale cache key and retrieve outdated sync status ## Solution Move the timestamp update to an `after_commit` callback. This ensures: - The sync state change is fully committed and visible to all database connections - The timestamp is updated only after the commit - Any subsequent cache reads will see the new timestamp and invalidate properly This eliminates the race condition while maintaining all existing functionality that depends on these timestamps for cache invalidation.

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Reference: gavin/maybe#2412