wasilak/go-hello-world

package gorilla

import (
    "fmt"
    "net/http"
    "strings"
    "time"

    "log/slog"

    "github.com/gorilla/mux"
    "github.com/prometheus/client_golang/prometheus"
    "github.com/prometheus/client_golang/prometheus/promauto"
    "github.com/wasilak/go-hello-world/utils"
)

var (
    httpDuration = promauto.NewHistogramVec(prometheus.HistogramOpts{
        Name: fmt.Sprintf("%s_http_duration_seconds", strings.ReplaceAll(utils.GetAppName(), "-", "_")),
        Help: "Duration of HTTP requests.",
    }, []string{"path"})

    requestCounter = promauto.NewCounterVec(prometheus.CounterOpts{
        Name: fmt.Sprintf("%s_requests_count_total", strings.ReplaceAll(utils.GetAppName(), "-", "_")),
        Help: "HTTP requests count.",
    }, []string{"path", "host"})
)

// Middleware type
type Middleware func(http.HandlerFunc) http.HandlerFunc

// Chain applies middlewares to a http.HandlerFunc
func chain(f http.HandlerFunc, middlewares ...Middleware) http.HandlerFunc {
    for _, m := range middlewares {
        f = m(f)
    }
    return f
}

// Logging logs all requests with its path and the time it took to process
func logging() Middleware {

    // Create a new Middleware
    return func(f http.HandlerFunc) http.HandlerFunc {

        // Define the http.HandlerFunc
        return func(w http.ResponseWriter, r *http.Request) {

            // Do middleware things
            start := time.Now()
            defer func() {
                slog.InfoContext(r.Context(), "request", "path", r.URL.Path, "time", time.Since(start))
            }()

            // Call the next middleware/handler in chain
            f(w, r)
        }
    }
}

// prometheusMiddleware implements mux.MiddlewareFunc.
func prometheusMiddleware(next http.Handler) http.Handler {
    return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
        route := mux.CurrentRoute(r)
        path, _ := route.GetPathTemplate()
        timer := prometheus.NewTimer(httpDuration.WithLabelValues(path))
        requestCounter.With(prometheus.Labels{"path": path, "host": r.Host}).Inc()
        next.ServeHTTP(w, r)
        timer.ObserveDuration()
    })
}