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A simple golang web server with basic logging, tracing, health check, graceful shutdown and zero dependencies
package main
import (
"context"
"flag"
"fmt"
"log"
"net/http"
"os"
"os/signal"
"sync/atomic"
"time"
)
type key int
const (
requestIDKey key = 0
)
var (
listenAddr string
healthy int32
)
func main() {
flag.StringVar(&listenAddr, "listen-addr", ":5000", "server listen address")
flag.Parse()
logger := log.New(os.Stdout, "http: ", log.LstdFlags)
logger.Println("Server is starting...")
router := http.NewServeMux()
router.Handle("/", index())
router.Handle("/healthz", healthz())
nextRequestID := func() string {
return fmt.Sprintf("%d", time.Now().UnixNano())
}
server := &http.Server{
Addr: listenAddr,
Handler: tracing(nextRequestID)(logging(logger)(router)),
ErrorLog: logger,
ReadTimeout: 5 * time.Second,
WriteTimeout: 10 * time.Second,
IdleTimeout: 15 * time.Second,
}
done := make(chan bool)
quit := make(chan os.Signal, 1)
signal.Notify(quit, os.Interrupt)
go func() {
<-quit
logger.Println("Server is shutting down...")
atomic.StoreInt32(&healthy, 0)
ctx, cancel := context.WithTimeout(context.Background(), 30*time.Second)
defer cancel()
server.SetKeepAlivesEnabled(false)
if err := server.Shutdown(ctx); err != nil {
logger.Fatalf("Could not gracefully shutdown the server: %v\n", err)
}
close(done)
}()
logger.Println("Server is ready to handle requests at", listenAddr)
atomic.StoreInt32(&healthy, 1)
if err := server.ListenAndServe(); err != nil && err != http.ErrServerClosed {
logger.Fatalf("Could not listen on %s: %v\n", listenAddr, err)
}
<-done
logger.Println("Server stopped")
}
func index() http.Handler {
return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
if r.URL.Path != "/" {
http.Error(w, http.StatusText(http.StatusNotFound), http.StatusNotFound)
return
}
w.Header().Set("Content-Type", "text/plain; charset=utf-8")
w.Header().Set("X-Content-Type-Options", "nosniff")
w.WriteHeader(http.StatusOK)
fmt.Fprintln(w, "Hello, World!")
})
}
func healthz() http.Handler {
return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
if atomic.LoadInt32(&healthy) == 1 {
w.WriteHeader(http.StatusNoContent)
return
}
w.WriteHeader(http.StatusServiceUnavailable)
})
}
func logging(logger *log.Logger) func(http.Handler) http.Handler {
return func(next http.Handler) http.Handler {
return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
defer func() {
requestID, ok := r.Context().Value(requestIDKey).(string)
if !ok {
requestID = "unknown"
}
logger.Println(requestID, r.Method, r.URL.Path, r.RemoteAddr, r.UserAgent())
}()
next.ServeHTTP(w, r)
})
}
}
func tracing(nextRequestID func() string) func(http.Handler) http.Handler {
return func(next http.Handler) http.Handler {
return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
requestID := r.Header.Get("X-Request-Id")
if requestID == "" {
requestID = nextRequestID()
}
ctx := context.WithValue(r.Context(), requestIDKey, requestID)
w.Header().Set("X-Request-Id", requestID)
next.ServeHTTP(w, r.WithContext(ctx))
})
}
}
@wvh
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wvh commented Aug 25, 2020

if i started this server from the commandline like go run server.go, how do you stop it?

Ctrl-C (sigint), or use kill to send the process a signal.

@Sen10001
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Sen10001 commented Oct 8, 2020

how to stop the server once it started?

@marcandcheese
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marcandcheese commented Nov 18, 2020

Anyone know how I can also log GET and POST arguments? Like for example printing out "index.php?firstname=John&lastname=Smith". Would be much appreciated!

@wvh
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wvh commented Nov 26, 2020

Anyone know how I can also log GET and POST arguments? Like for example printing out "index.php?firstname=John&lastname=Smith". Would be much appreciated!

If you are interested in the GET query parameters, check the other fields and methods of URL, such as RequestURI, RawQuery or even just calling String() on URL itself.

If you also want the POST variables, you need to check out Request.Form and Request.ParseForm(). Note it's usually a bad idea to log POST request variables as they might be rather large or contain sensitive information such as passwords.

@rexlx
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rexlx commented May 17, 2021

I added a -d option to specify a directory to serve out, but im no good with forking and pull requests. I think I might have removed some useful functionality in the process :)) but if you like that flag, you can find the repo pinned to my github and hack away at it

@andrew-werdna
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andrew-werdna commented Jun 21, 2021

This is cash-money awesome! Thank you for sharing this!

@rpeets
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rpeets commented Jul 11, 2021

Any pointers on how to include the http.statuscode in logs, please?

@titaneric
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titaneric commented Feb 11, 2022

Thanks for sharing

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