---
phase: 08-observability-stack
plan: 01
subsystem: infra
tags: [prometheus, prom-client, servicemonitor, metrics, kubernetes, helm]

# Dependency graph
requires:
  - phase: 06-deployment
    provides: Helm chart structure and Kubernetes deployment
provides:
  - Prometheus-format /metrics endpoint
  - ServiceMonitor for Prometheus Operator discovery
  - Default Node.js process metrics (CPU, memory, heap, event loop)
affects: [08-02, 08-03, observability]

# Tech tracking
tech-stack:
  added: [prom-client]
  patterns: [metrics-endpoint, servicemonitor-discovery]

key-files:
  created:
    - src/lib/server/metrics.ts
    - src/routes/metrics/+server.ts
    - helm/taskplaner/templates/servicemonitor.yaml
  modified:
    - package.json
    - helm/taskplaner/values.yaml

key-decisions:
  - "Use prom-client default metrics only (no custom metrics for initial setup)"
  - "ServiceMonitor enabled by default in values.yaml"

patterns-established:
  - "Metrics endpoint: server-side only route returning registry.metrics() with correct Content-Type"
  - "ServiceMonitor: conditional on metrics.enabled, uses selectorLabels for pod discovery"

# Metrics
duration: 4min
completed: 2026-02-03
---

# Phase 8 Plan 1: TaskPlanner /metrics endpoint and ServiceMonitor Summary

**Prometheus /metrics endpoint with prom-client and ServiceMonitor for Prometheus Operator scraping**

## Performance

- **Duration:** 4 min
- **Started:** 2026-02-03T21:04:03Z
- **Completed:** 2026-02-03T21:08:00Z
- **Tasks:** 2
- **Files modified:** 5

## Accomplishments

- /metrics endpoint returns Prometheus-format text including process_cpu_seconds_total, nodejs_heap_size_total_bytes
- ServiceMonitor template renders correctly with selector matching TaskPlanner service
- Metrics enabled by default in Helm chart (metrics.enabled: true)

## Task Commits

Each task was committed atomically:

1. **Task 1: Add prom-client and create /metrics endpoint** - `f60aad2` (feat)
2. **Task 2: Add ServiceMonitor to Helm chart** - `f2a2893` (feat)

## Files Created/Modified

- `src/lib/server/metrics.ts` - Prometheus registry with default Node.js metrics
- `src/routes/metrics/+server.ts` - GET handler returning metrics in Prometheus format
- `helm/taskplaner/templates/servicemonitor.yaml` - ServiceMonitor for Prometheus Operator
- `helm/taskplaner/values.yaml` - Added metrics.enabled and metrics.interval settings
- `package.json` - Added prom-client dependency

## Decisions Made

- Used prom-client default metrics only (CPU, memory, heap, event loop) - no custom application metrics needed for initial observability setup
- ServiceMonitor enabled by default since metrics endpoint is always available

## Deviations from Plan

None - plan executed exactly as written.

## Issues Encountered

None - all verification checks passed.

## User Setup Required

None - no external service configuration required. The ServiceMonitor will be automatically discovered by Prometheus Operator once deployed via ArgoCD.

## Next Phase Readiness

- /metrics endpoint ready for Prometheus scraping
- ServiceMonitor will be deployed with next ArgoCD sync
- Ready for Phase 8-02: Promtail to Alloy migration

---
*Phase: 08-observability-stack*
*Completed: 2026-02-03*