服务器启动后如何在http.Handle（）中更改处理程序？

Question

I am using socketio "github.com/googollee/go-socket.io" in Go. For some reason, I have to make a new *socketio.server and register it to "/static/" which is already been registered with the old *socketio.server.

It means that I have to replace the handler ioserver in http.Handle("/socket.io/", ioserver) after the server has been started.

Below is part of my code, when something happens, I will create a new ioserver. I want the new ioserver to be the handler in http.Handle("/socket.io/", ioserver)

ioserver, _ = socketio.NewServer(nil)
http.Handle("/socket.io/", ioserver)
log.Fatal(http.ListenAndServe(":81", nil))

Answer 1

An application cannot swap handlers in the mux, but it can write a handler that swaps between other handlers:

type swapper struct {
    mu sync.Mutex
    h http.Handler
}

func (s *swapper) setHandler(h http.Handler) {
    s.mu.Lock()
    s.h = h
    s.mu.Unlock()
}

func (w *swapper) ServeHTTP(w http.ResponseWriter, r *http.Request) {
    s.mu.Lock()
    h := s.h
    s.mu.Unlock()
    h.ServeHTTP(w, r)
}

Register it like this:

ioserver, _ = socketio.NewServer(nil)
s := &swapper{}
s.setHandler(ioserver)
http.Handle("/socket.io/", s)
log.Fatal(http.ListenAndServe(":81", nil))

At any time, the application can call s.setHandler to swap in a new handler.