Monitoring

Observability ประกอบด้วย: Metrics, Logging, และ Tracing

Prometheus Metrics

go get github.com/prometheus/client_golang/prometheus
go get github.com/prometheus/client_golang/prometheus/promhttp

package main

import (
    "net/http"

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

var (
    // Counter
    requestsTotal = prometheus.NewCounterVec(
        prometheus.CounterOpts{
            Name: "http_requests_total",
            Help: "Total number of HTTP requests",
        },
        []string{"method", "path", "status"},
    )

    // Histogram
    requestDuration = prometheus.NewHistogramVec(
        prometheus.HistogramOpts{
            Name:    "http_request_duration_seconds",
            Help:    "HTTP request duration in seconds",
            Buckets: prometheus.DefBuckets,
        },
        []string{"method", "path"},
    )

    // Gauge
    activeConnections = prometheus.NewGauge(
        prometheus.GaugeOpts{
            Name: "active_connections",
            Help: "Number of active connections",
        },
    )
)

func init() {
    prometheus.MustRegister(requestsTotal)
    prometheus.MustRegister(requestDuration)
    prometheus.MustRegister(activeConnections)
}

func main() {
    // Expose metrics endpoint
    http.Handle("/metrics", promhttp.Handler())

    http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
        w.Write([]byte("Hello!"))
    })

    http.ListenAndServe(":8080", nil)
}