concurrency - 并发http请求没有响应

Question

我正在尝试使用 Go，但遇到了一个我无法解决的问题。

以下代码是最不可能重现我的问题的代码。目标原始代码的一部分是将 http 请求委托(delegate)给 goroutines。每个协程进行一些繁重的图像计算并应该做出响应。

package main

import (
    "fmt"
    "runtime"
    "net/http"
)

func main() {
    http.HandleFunc("/", handle)
    http.ListenAndServe(":8080", nil)
}

func handle(w http.ResponseWriter, r *http.Request) {

    // the idea is to be able to handle several requests
    // in parallel

    // the "go" is problematic
    go delegate(w)
}

func delegate(w http.ResponseWriter) {

    // do some heavy calculations first

    // present the result (in the original code, the image)
    fmt.Fprint(w, "hello")
}

在 go delegate(w) 的情况下，没有 go 就没有响应效果很好。

谁能解释一下这是怎么回事？非常感谢!

Answer 1

ListenAndServe 已经启动了 goroutines 来调用你的处理函数，所以你不应该自己做。

这是 the relevant functions from the package source 的代码:

1089    func ListenAndServe(addr string, handler Handler) error {
1090        server := &Server{Addr: addr, Handler: handler}
1091        return server.ListenAndServe()
1092    }


1010    func (srv *Server) ListenAndServe() error {
1011        addr := srv.Addr
1012        if addr == "" {
1013            addr = ":http"
1014        }
1015        l, e := net.Listen("tcp", addr)
1016        if e != nil {
1017            return e
1018        }
1019        return srv.Serve(l)
1020    }


1025    func (srv *Server) Serve(l net.Listener) error {
1026        defer l.Close()
1027        var tempDelay time.Duration // how long to sleep on accept failure
1028        for {

1057            go c.serve()
1058        }
1059        panic("not reached")
1060    }


579 // Serve a new connection.
580 func (c *conn) serve() {
581     defer func() {
582         err := recover()

669         handler.ServeHTTP(w, w.req)

所以你的代码应该是

func handle(w http.ResponseWriter, r *http.Request) {
    // the idea is to be able to handle several requests
    // in parallel
    // do some heavy calculations first

    // present the result (in the original code, the image)
    fmt.Fprint(w, "hello")
}