Implement notification system that works even when database is unavailable.
Problem:
- When Uptime Kuma's database (external MariaDB/SQLite) becomes unavailable,
UK stops functioning and cannot send notifications about its own failure.
- Users are not alerted when UK itself is having database connectivity issues.
Solution:
- Added notification cache system that stores all active notification configs
in memory when database is available
- Implemented database error detection in both monitor.js and server.js
error handlers to catch EHOSTUNREACH, ECONNREFUSED, and other DB errors
- Added sendDatabaseDownNotification() method that uses cached notifications
to send alerts when database connection fails
- Cache automatically refreshes periodically (every 30 minutes) and when
notifications are added/updated/deleted
- Prevents duplicate notifications for the same database down event
Changes:
- server/notification.js: Added cache system and database down notification
- server/server.js: Enhanced error handler to detect DB errors and trigger
notifications, refresh cache on startup
- server/model/monitor.js: Added DB error detection in safeBeat error handler
- server/jobs.js: Added periodic cache refresh job (every 30 minutes)
- test/backend-test/test-database-down-notification.js: Comprehensive test
suite covering cache, notifications, error handling
This ensures users are always notified when UK itself is having database
connectivity issues, even if the database is completely unavailable.
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