如何在net/http中取消注册处理程序？

Question

我正在编写一个Web服务器,我需要在运行时注册处理程序.例如,"/ create"将为所有URL创建一个新的处理程序,如"/ 123/*"等.我需要一个相应的"/ destroy/123"来取消注册"/ 123/*"的处理程序.

这是处理"/ create"的代码

package main
import (
    "fmt"
    "net/http"
)

type MyHandler struct {
    id int
}
func (hf *MyHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
    fmt.Fprintln(w, r.URL.Path)
}

// Creates MyHandler instances and registers them as handlers at runtime
type HandlerFactory struct {
    handler_id int
}
func (hf *HandlerFactory) ServeHTTP(w http.ResponseWriter, r *http.Request) {
    hf.handler_id++
    handler := MyHandler{hf.handler_id}
    handle := fmt.Sprintf("/%d/", hf.handler_id)
    http.Handle(handle, &handler)
}

func main() {
    factory := HandlerFactory{0}
    http.Handle("/create", &factory)
    http.ListenAndServe("localhost:8080", nil)
}

我尝试通过嵌入实现我自己的多路复用器,http.ServeMux但它在私有变量(ServeMux.m)中保持其模式到处理程序的映射

Answer 1

我要做的是创建一个自定义ServerMux.复制代码GOROOT/src/pkg/net/http/server.go.它从837行开始,到939结束.

自定义ServerMux需要一种取消注册的方法.这应该很容易实现.只需抓住锁和del()地图条目即可.例如(所有代码未经测试):

// TODO: check if registered and return error if not.
// TODO: possibly remove the automatic permanent link between /dir and /dir/.
func (mux *MyMux) Deregister(pattern string) error {
    mux.mu.Lock()
    defer mux.mu.Unlock()
    del(mux.m, pattern)
    return nil
}

为了使用这个新的多路复用器,你可以这样做:

mux := newMux()
mux.Handle("/create", &factory)

srv := &http.Server {
    Addr: localhost:8080
    Handler: mux,
}
srv.ListenAndServe()

通过deregister()从另一个goroutine 调用来修改mux 是完全安全的,并将修改ListenAndServe()路由消息的方式.

Answer 2

看来你已经接受了答案,但我想提出一个替代解决方案.

我怀疑是否需要添加自定义多路复用器.在这个例子中,我使用的是gorilla muxer,但这仅仅是因为我熟悉它的模式匹配.理论上,您可以匹配传入URL中的模式,而无需替换默认的muxer.

我的代码在map中维护处理函数(string:handler name => function literal)...这适用于使用默认的muxers HandleFunc方法.

样本输入/输出:

GET/register/123

GET/123
hello from123.

GET/destroy/123

GET/123
[nothing]

package main

import (
    "code.google.com/p/gorilla/mux"
    "flag"
    "log"
    "net/http"
)

// Wraps server muxer, dynamic map of handlers, and listen port.
type Server struct {
    Dispatcher *mux.Router
    Urls       map[string]func(w http.ResponseWriter, r *http.Request)
    Port       string
}

// May the signal never stop.
func main() {
    //Initialize Server
    server := &Server{Port: "3000", Dispatcher: mux.NewRouter(), Urls: make(map[string]func(w http.ResponseWriter, r *http.Request))}

    var port = flag.String("port", "3000", "Default: 3000; Set the port for the web-server to accept incoming requests")
    flag.Parse()

    server.Port = *port
    log.Printf("Starting server on port: %s \n", server.Port)

    server.InitDispatch()
    log.Printf("Initializing request routes...\n")

    server.Start() //Launch server; blocks goroutine.
}

func (s *Server) Start() {

    http.ListenAndServe(":"+s.Port, s.Dispatcher)
}

// Initialize Dispatcher's routes.
func (s *Server) InitDispatch() {
    d := s.Dispatcher

    // Add handler to server's map.
    d.HandleFunc("/register/{name}", func(w http.ResponseWriter, r *http.Request) {
        //somewhere somehow you create the handler to be used; i'll just make an echohandler
        vars := mux.Vars(r)
        name := vars["name"]

        s.AddFunction(w, r, name)
    }).Methods("GET")

    d.HandleFunc("/destroy/{name}", func(w http.ResponseWriter, r *http.Request) {
        vars := mux.Vars(r)
        name := vars["name"]
        s.Destroy(name)
    }).Methods("GET")

    d.HandleFunc("/{name}", func(w http.ResponseWriter, r *http.Request) {
        //Lookup handler in map and call it, proxying this writer and request
        vars := mux.Vars(r)
        name := vars["name"]

        s.ProxyCall(w, r, name)
    }).Methods("GET")
}

func (s *Server) Destroy(fName string) {
    s.Urls[fName] = nil //remove handler
}

func (s *Server) ProxyCall(w http.ResponseWriter, r *http.Request, fName string) {
    if s.Urls[fName] != nil {
        s.Urls[fName](w, r) //proxy the call
    }
}

func (s *Server) AddFunction(w http.ResponseWriter, r *http.Request, fName string) {
    f := func(w http.ResponseWriter, r *http.Request) {
        w.Write([]byte("hello from" + fName))
    }

    s.Urls[fName] = f // Add the handler to our map
}