rcourtman c8e0281953 Add comprehensive alert system reliability improvements ...

This commit implements critical reliability features to prevent data loss
and improve alert system robustness:

**Persistent Notification Queue:**
- SQLite-backed queue with WAL journaling for crash recovery
- Dead Letter Queue (DLQ) for notifications that exhaust retries
- Exponential backoff retry logic (100ms → 200ms → 400ms)
- Full audit trail for all notification delivery attempts
- New file: internal/notifications/queue.go (661 lines)

**DLQ Management API:**
- GET /api/notifications/dlq - Retrieve DLQ items
- GET /api/notifications/queue/stats - Queue statistics
- POST /api/notifications/dlq/retry - Retry failed notifications
- POST /api/notifications/dlq/delete - Delete DLQ items
- New file: internal/api/notification_queue.go (145 lines)

**Prometheus Metrics:**
- 18 comprehensive metrics for alerts and notifications
- Metric hooks integrated via function pointers to avoid import cycles
- /metrics endpoint exposed for Prometheus scraping
- New file: internal/metrics/alert_metrics.go (193 lines)

**Alert History Reliability:**
- Exponential backoff retry for history saves (3 attempts)
- Automatic backup restoration on write failure
- Modified: internal/alerts/history.go

**Flapping Detection:**
- Detects and suppresses rapidly oscillating alerts
- Configurable window (default: 5 minutes)
- Configurable threshold (default: 5 state changes)
- Configurable cooldown (default: 15 minutes)
- Automatic cleanup of inactive flapping history

**Alert TTL & Auto-Cleanup:**
- MaxAlertAgeDays: Auto-cleanup old alerts (default: 7 days)
- MaxAcknowledgedAgeDays: Faster cleanup for acked alerts (default: 1 day)
- AutoAcknowledgeAfterHours: Auto-ack long-running alerts (default: 24 hours)
- Prevents memory leaks from long-running alerts

**WebSocket Broadcast Sequencer:**
- Channel-based sequencing ensures ordered message delivery
- 100ms coalescing window for rapid state updates
- Prevents race conditions in WebSocket broadcasts
- Modified: internal/websocket/hub.go

**Configuration Fields Added:**
- FlappingEnabled, FlappingWindowSeconds, FlappingThreshold, FlappingCooldownMinutes
- MaxAlertAgeDays, MaxAcknowledgedAgeDays, AutoAcknowledgeAfterHours

All features are production-ready and build successfully.

2025-11-06 16:46:30 +00:00

..

alert_metrics.go

Add comprehensive alert system reliability improvements

2025-11-06 16:46:30 +00:00