# Router Heartbeat and Health Monitoring

## Module
Gateway

## Status
IMPLEMENTED

## Description
Heartbeat protocol with configurable intervals, `HealthMonitorService` for stale instance detection, ping latency tracking with exponential moving average, Draining health status for graceful shutdown, and automatic instance removal on missed heartbeats.

## Implementation Details
- **Health monitor service**: `src/Gateway/StellaOps.Gateway.WebService/Services/GatewayHealthMonitorService.cs` -- stale instance detection, heartbeat tracking
- **Health check middleware**: `src/Gateway/StellaOps.Gateway.WebService/Middleware/HealthCheckMiddleware.cs` -- health endpoint processing
- **Gateway metrics**: `src/Gateway/StellaOps.Gateway.WebService/Services/GatewayMetrics.cs` -- latency tracking, connection metrics
- **Gateway hosted service**: `src/Gateway/StellaOps.Gateway.WebService/Services/GatewayHostedService.cs` -- connection lifecycle management
- **Options**: `src/Gateway/StellaOps.Gateway.WebService/Configuration/GatewayOptions.cs` -- configurable heartbeat intervals
- **Source**: batch_51/file_23.md

## E2E Test Plan
- [ ] Verify heartbeat protocol detects stale instances
- [ ] Test configurable heartbeat intervals
- [ ] Verify Draining status for graceful shutdown
- [ ] Test automatic instance removal on missed heartbeats