Metrics

timeserver exposes Prometheus metrics at /metrics using the prom-client library.

Scraping

curl http://localhost:8888/metrics

The endpoint returns metrics in Prometheus text exposition format.

Default metrics

prom-client collects default Node.js process metrics automatically:

Metric	Description
process_cpu_user_seconds_total	CPU time in user mode
process_cpu_system_seconds_total	CPU time in kernel mode
process_resident_memory_bytes	RSS memory usage
nodejs_heap_size_used_bytes	V8 heap used
nodejs_eventloop_lag_seconds	Event loop lag
nodejs_active_handles_total	Open handles

HTTP metrics

Custom HTTP duration histogram tracking all requests:

http_request_duration_seconds_bucket{le="0.05",route="/api/v1/time",method="GET",status_code="200"} 12
http_request_duration_seconds_bucket{le="0.1",...} 42
http_request_duration_seconds_sum{...} 1.234
http_request_duration_seconds_count{...} 42

Labels: route, method, status_code.

Grafana dashboard

A pre-built Grafana dashboard JSON is included at grafana/dashboard.json. Import it into any Grafana instance connected to your Prometheus datasource to visualize:

• Request rate (req/s)
• P50 / P95 / P99 latency
• Error rate (4xx / 5xx)
• Node.js heap and event loop lag

Prometheus scrape config

Add this to your prometheus.yml to scrape the server:

scrape_configs:
  - job_name: timeserver
    static_configs:
      - targets: ['localhost:8888']

When running in Kubernetes, use the pod annotations approach or a ServiceMonitor (Prometheus Operator).