Building an Observability Dashboard with Prometheus & Grafana

Prometheus Exporter

This lesson explains the main concept clearly with beginner-friendly examples and background so you can learn why the code works.

Expose metrics via /metrics endpoint.

import (
    "github.com/prometheus/client_golang/prometheus"
    "github.com/prometheus/client_golang/prometheus/promhttp"
)

var (
    requestCount = prometheus.NewCounterVec(prometheus.CounterOpts{Name: "http_requests_total", Help: "Total HTTP requests"}, []string{"handler"})
)

func init() { prometheus.MustRegister(requestCount) }

func metricsMiddleware(next http.Handler) http.Handler {
    return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
        requestCount.WithLabelValues(r.URL.Path).Inc()
        next.ServeHTTP(w, r)
    })
}

func main() {
    mux := http.NewServeMux()
    // … register app handlers …
    mux.Handle("/metrics", promhttp.Handler())
    log.Fatal(http.ListenAndServe(":8080", metricsMiddleware(mux))
}

Grafana

• Add Prometheus as a data source (http://localhost:9090).
• Create a dashboard visualizing http_requests_total.