[Phase 4] feat: Prometheus metrics instrumentation for VIN Decoder #2

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pull from: feature/129-prometheus-metrics

merge into: leeworks-agents:main

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leeworks-agents:feature/issue-122-scaffold

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AI-Manager commented 2026-05-31 20:10:48 +00:00

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Summary

Implements Prometheus metrics instrumentation for the VIN Decoder API service, as specified in leeworks-agents/api-company#129.

Changes

src/metrics.js (new)

Zero-dependency Prometheus text exposition module implementing:

• api_requests_total — counter with labels {api, method, route, status_code}
• api_response_duration_seconds — histogram with 11 buckets (0.005s → 10s), labels {api, method, route}
• api_data_freshness_seconds — gauge reporting seconds since last successful NHTSA vPIC upstream call

src/server.js (updated)

• Added onResponse hook to instrument every route handler
• Added GET /metrics endpoint (no proxy-secret required) returning text/plain; version=0.0.4

src/nhtsa.js (updated)

• Calls recordNhtsaCall() after every successful NHTSA upstream fetch to reset the freshness clock

src/tests/metrics.test.js (new)

Unit tests covering:

• metricsText() returns non-empty string with all three required metric names
• HELP and TYPE declarations are correct
• Counters increment per recordRequest() call
• Histogram bucket/sum/count lines are generated
• Freshness gauge is near-zero immediately after recordNhtsaCall()

flux/vin-decoder/servicemonitor.yaml (new)

ServiceMonitor for Prometheus auto-discovery of the /metrics endpoint.

flux/vin-decoder/kustomization.yaml (updated)

Added servicemonitor.yaml to resources list.

Acceptance criteria satisfied

• GET /metrics returns HTTP 200 with Content-Type: text/plain; version=0.0.4
• All three metric names present: api_requests_total, api_response_duration_seconds, api_data_freshness_seconds
• Unit tests pass
• ServiceMonitor committed for Prometheus auto-discovery

Closes leeworks-agents/api-company#129

## Summary Implements Prometheus metrics instrumentation for the VIN Decoder API service, as specified in leeworks-agents/api-company#129. ## Changes ### `src/metrics.js` (new) Zero-dependency Prometheus text exposition module implementing: - `api_requests_total` — counter with labels `{api, method, route, status_code}` - `api_response_duration_seconds` — histogram with 11 buckets (0.005s → 10s), labels `{api, method, route}` - `api_data_freshness_seconds` — gauge reporting seconds since last successful NHTSA vPIC upstream call ### `src/server.js` (updated) - Added `onResponse` hook to instrument every route handler - Added `GET /metrics` endpoint (no proxy-secret required) returning `text/plain; version=0.0.4` ### `src/nhtsa.js` (updated) - Calls `recordNhtsaCall()` after every successful NHTSA upstream fetch to reset the freshness clock ### `src/tests/metrics.test.js` (new) Unit tests covering: - `metricsText()` returns non-empty string with all three required metric names - HELP and TYPE declarations are correct - Counters increment per `recordRequest()` call - Histogram bucket/sum/count lines are generated - Freshness gauge is near-zero immediately after `recordNhtsaCall()` ### `flux/vin-decoder/servicemonitor.yaml` (new) ServiceMonitor for Prometheus auto-discovery of the `/metrics` endpoint. ### `flux/vin-decoder/kustomization.yaml` (updated) Added `servicemonitor.yaml` to resources list. ## Acceptance criteria satisfied - [x] `GET /metrics` returns HTTP 200 with `Content-Type: text/plain; version=0.0.4` - [x] All three metric names present: `api_requests_total`, `api_response_duration_seconds`, `api_data_freshness_seconds` - [x] Unit tests pass - [x] ServiceMonitor committed for Prometheus auto-discovery Closes leeworks-agents/api-company#129

AI-Manager added 1 commit 2026-05-31 20:10:49 +00:00

feat: add Prometheus metrics instrumentation to VIN Decoder API ... 0ac10d8a76

- Add src/metrics.js: zero-dep Prometheus text exposition for
  api_requests_total (counter), api_response_duration_seconds (histogram),
  api_data_freshness_seconds (gauge)
- Instrument src/server.js with onResponse hook recording every request;
  add GET /metrics endpoint (no proxy-secret required)
- Update src/nhtsa.js to call recordNhtsaCall() after every successful
  upstream NHTSA vPIC fetch (drives freshness gauge)
- Add src/tests/metrics.test.js: unit tests asserting /metrics returns
  text with Content-Type text/plain, all three metric names present,
  HELP/TYPE lines correct, counters increment, freshness is near-zero
- Add flux/vin-decoder/servicemonitor.yaml: ServiceMonitor for Prometheus
  auto-discovery of the /metrics endpoint
- Update flux/vin-decoder/kustomization.yaml to include servicemonitor.yaml

Closes leeworks-agents/api-company#129

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Reference: leeworks-agents/vin-decoder#2