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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