Golang golang-gracefulstoppablehttpd (snippet)

Go programming example 'golang-gracefulstoppablehttpd'

golang-gracefulstoppablehttpd

Golang beginners example: golang-gracefulstoppablehttpd

package main

import (
    "fmt"
    "log"
    "net"
    "net/http"
    "strconv"
    "strings"
    "sync"
    "time"
)

var listener net.Listener
var requestcounter int
var stopvar bool

type handler struct {
    wg sync.WaitGroup
    *http.ServeMux
}

func (h *handler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
    h.wg.Add(1)
    defer h.wg.Done()
    h.ServeMux.ServeHTTP(w, r)

    w.(http.Flusher).Flush()
}

func restart(w http.ResponseWriter, r *http.Request) {
    listener.Close()
    w.Write([]byte("listener restarted"))
}

func stop(w http.ResponseWriter, r *http.Request) {
    stopvar = true
    listener.Close()
    w.Write([]byte("listener stoped"))
}

func normal(w http.ResponseWriter, r *http.Request) {
    url := r.URL.Path
    if r.URL.RawQuery != "" {
        url = strings.Join([]string{url, "?", r.URL.RawQuery}, "")
    }
    fmt.Fprintf(w, "Hello World\nYou requested: %s\n", url)
    time.Sleep(4 * time.Second)
    fmt.Fprintf(w, "this is request number %s\n", strconv.Itoa(requestcounter))
    log.Println(url)
    requestcounter++
}

func main() {
    log.Printf("started program")
    var err error
    var ler string
    for !stopvar {
        listener, err = net.Listen("tcp", ":8080")

        if err == nil {
            log.Printf("started listener on port 8080 with counter: %v\n", requestcounter)
            h := &handler{ServeMux: http.NewServeMux()}

            h.ServeMux.HandleFunc("/", normal)
            h.ServeMux.HandleFunc("/stop", stop)
            h.ServeMux.HandleFunc("/restart", restart)

            http.Serve(listener, h)

            h.wg.Wait()
        } else {
            if fmt.Sprintf("%v", err) != ler {
                ler = fmt.Sprintf("%v", err)
                fmt.Println(ler)
            }
        }
    }
}

Useful links

• Learn Go: https://golangr.com
• Download Go: https://golang.org