# StellaRouter Performance Testing Pipeline (k6 + Prometheus + Correlation IDs)

## Module
Gateway

## Status
VERIFIED

## Description
Performance testing pipeline with k6 load test scenarios (A-G), correlation ID instrumentation, Prometheus-compatible metrics, and Grafana dashboards for performance curve modeling.

## Implementation Details
- **k6 load tests**: `src/Gateway/__Tests/load/gateway_performance.k6.js` -- 7 scenarios A-G (511 lines)
- **Performance metrics**: `src/Gateway/StellaOps.Gateway.WebService/Services/GatewayPerformanceMetrics.cs` -- Prometheus counters/histograms + scenario config models (318 lines)
- **Correlation ID middleware**: `src/Gateway/StellaOps.Gateway.WebService/Middleware/CorrelationIdMiddleware.cs` -- correlation ID propagation with validation (64 lines)
- **Gateway metrics**: `src/Gateway/StellaOps.Gateway.WebService/Services/GatewayMetrics.cs` -- base Prometheus metrics
- **Health monitoring**: `src/Gateway/StellaOps.Gateway.WebService/Services/GatewayHealthMonitorService.cs`
- **Grafana dashboard**: `devops/telemetry/dashboards/stella-ops-gateway-performance.json`
- Source: Feature matrix scan

## E2E Test Plan
- [x] Verify k6 scenarios A-G exist and cover the required traffic patterns
- [x] Test correlation ID propagation overhead measurement
- [x] Verify Prometheus metrics are exposed correctly
- [x] Verify Grafana dashboard exists

## Verification
- **Run ID**: run-002
- **Date**: 2026-02-09
- **Method**: Tier 1 code review + Tier 2d integration tests
- **Build**: PASS (0 errors, 0 warnings)
- **Tests**: PASS (202/202 gateway tests pass)
- **Code Review**:
  - k6 script (511 lines): All 7 scenarios verified: A (health baseline), B (OpenAPI under load), C (routing throughput), D (correlation ID overhead), E (rate limit boundary), F (connection ramp/saturation), G (sustained soak).
  - GatewayPerformanceMetrics (318 lines): Prometheus counters (requests, errors, rate-limits), histograms (request/auth/transport/routing durations), scenario config models with PerformanceCurvePoint.
  - GatewayPerformanceMetricsTests (418 lines, 20+ tests): Verify scenario configs, curve point computed properties, threshold violations, observation recording.
  - CorrelationIdMiddlewareTests (71 lines, 4 tests): ID generation, echo, TraceIdentifier sync.
  - Note: Feature file's "What's Missing" section is STALE -- k6 scripts and Grafana dashboard DO exist.
- **Verdict**: PASS