Instead of trying to restart the server, switch the handler:
package main
import (
"fmt"
"io/ioutil"
"log"
"net/http"
"strconv"
)
// Some state so we can show the old handler is in effect...
type Foo struct {
SomeVar int
}
func (f *Foo) ServeHTTP(w http.ResponseWriter, r *http.Request) {
fmt.Printf("In handler wrapper, f = %p\n", f)
w.Write([]byte(strconv.Itoa(f.SomeVar)))
}
type switchable struct {
h http.Handler
}
func (s *switchable) ServeHTTP(w http.ResponseWriter, r *http.Request) {
s.h.ServeHTTP(w, r)
}
func main() {
log.SetFlags(log.Lshortfile)
f1 := &Foo{SomeVar: 1}
f2 := &Foo{SomeVar: 2}
handler := &switchable{f1}
go func() {
log.Fatalln(http.ListenAndServe("0.0.0.0:8090", handler))
}()
fmt.Println(doRequest())
handler.h = f2
fmt.Println(doRequest())
}
func doRequest() string {
client := &http.Client{}
req, err := http.NewRequest("GET", "http://0.0.0.0:8090";, nil)
if err != nil {
log.Fatalln(err)
}
resp, err := client.Do(req)
if err != nil {
log.Fatalln(err)
}
bytes, err := ioutil.ReadAll(resp.Body)
if err != nil {
log.Fatalln(err)
}
return string(bytes)
}
Output:
$ go run main.go
In handler wrapper, f = 0xc420060fa0
1
In handler wrapper, f = 0xc420060fa8
2
I'm not sure if there is a race condition here or not...
On Tuesday, April 18, 2017 at 7:02:17 AM UTC+2, Ken Simon wrote:
>
> Hello golang-nuts!
>
> I have some code that creates a short-lived HTTP server, and I'm trying to
> write tests for it. I'm hitting a case where HTTP handlers seem to stick
> around even though I'm creating a brand new `http.ServeMux`, `http.Server`,
> and `net.Listener` objects. How do I get rid of old handlers?
>
> Here's a semi-simple reproducible case:
>
> package main
>
> import (
> "fmt"
> "io/ioutil"
> "net"
> "net/http"
> "os"
> "strconv"
> "time"
> )
>
> // Some state so we can show the old handler is in effect...
> type Foo struct {
> SomeVar int
> }
>
> func (f *Foo) Serve(addr string) (net.Listener, error) {
> l, err := net.Listen("tcp", addr)
> if err != nil {
> return nil, err
> }
> mux := http.NewServeMux()
> mux.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
> fmt.Printf("In handler wrapper, f = %p\n", f)
> w.Write([]byte(strconv.Itoa(f.SomeVar)))
> })
> srv := &http.Server{
> Handler: mux,
> }
>
> go srv.Serve(l)
> return l, nil
> }
>
> func main() {
> f1 := &Foo{SomeVar: 1}
> f2 := &Foo{SomeVar: 2}
>
> l, err := f1.Serve("0.0.0.0:8090")
> if err != nil {
> fmt.Println(err)
> os.Exit(1)
> }
> fmt.Println(doRequest())
> l.Close()
> // Ok it didn't actually close, wait a bit or it'll show the address as
> // already in use...
> time.Sleep(1 * time.Second)
>
> l, err = f2.Serve("0.0.0.0:8090")
> if err != nil {
> fmt.Println(err)
> os.Exit(1)
> }
> fmt.Println(doRequest())
> l.Close()
> }
>
> func doRequest() string {
> client := &http.Client{}
> req, _ := http.NewRequest("GET", "http://0.0.0.0:8090";, nil)
> resp, _ := client.Do(req)
> bytes, _ := ioutil.ReadAll(resp.Body)
> return string(bytes)
> }
>
> Output:
>
> $ go run main.go
> In handler wrapper, f = 0xc42000d200
> 1
> In handler wrapper, f = 0xc42000d200
> 1
>
> Note the pointer to the method receiver is the same in both cases,
> indicating the old ServeMux is still handling the new request... (boy did
> it take me a long time to figure out what was going on in a non-trivial
> codebase...)
>
> What's happening here? Is the old http.Server still "attached" to the
> tcp.Listener? What can I do to fix this?
>
> Thanks so much!
>
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