Task 8 of 10 complete. Exposes read-only scheduler health data including:
- Queue depth and distribution by instance type
- Dead-letter queue inspection (top 25 tasks with error details)
- Circuit breaker states (instance-level)
- Staleness scores per instance
New API endpoint:
GET /api/monitoring/scheduler/health (requires authentication)
New snapshot methods:
- StalenessTracker.Snapshot() - exports all staleness data
- TaskQueue.Snapshot() - queue depth & per-type distribution
- TaskQueue.PeekAll() - dead-letter task inspection
- circuitBreaker.State() - exports state, failures, retryAt
- Monitor.SchedulerHealth() - aggregates all health data
Documentation updated with API spec, field descriptions, and usage examples.
Adds freshness metadata tracking for all monitored instances:
- StalenessTracker with per-instance last success/error/mutation timestamps
- Change hash detection using SHA1 for detecting data mutations
- Normalized staleness scoring (0-1 scale) based on age vs maxStale
- Integration with PollMetrics for authoritative last-success data
- Wired into all poll functions (PVE/PBS/PMG) via UpdateSuccess/UpdateError
- Connected to scheduler as StalenessSource implementation
Task 4 of 10 complete. Ready for adaptive interval logic.
