简单的 Go 网络服务器，在客户端看不到响应
我正在学习 Go，并且正在编写一个简单的 Web 服务器，它使用一个通道来限制并发请求的数量。服务器在控制台打印日志条目，显示它正在接收请求并处理它们，但是客户端浏览器不显示任何输出。我试过添加响应编写器的冲洗，但没有帮助。
作为菜鸟，我错过了什么？感谢您提供任何提示/指示。
这是代码：
package main
import (
"fmt"
"html"
"net/http"
"time"
)
// define a type to be used with our request channel
type clientRequest struct {
r *http.Request
w http.ResponseWriter
}
const (
MaxRequests int = 10
)
// the request channel, to limit the number of simultaneous requests being processed
var reqChannel chan *clientRequest
func init() {
reqChannel = make(chan *clientRequest, MaxRequests)
}
func main() {
// create the server's handler
var ServeMux = http.NewServeMux()
ServeMux.HandleFunc("/", serveHandler)
// start pool of request handlers, all reading from the same channel
for i := 0; i < MaxRequests; i++ {
go processRequest(i)
}
// create the server object
s := &http.Server{
Addr: ":8080",
Handler: ServeMux, // handler to invoke, http.DefaultServeMux if nil
ReadTimeout: 10 * time.Second, // maximum duration before timing out read of the request
WriteTimeout: 10 * time.Second, // maximum duration before timing out write of the response
MaxHeaderBytes: 1 << 20, // maximum size of request headers, 1048576 bytes
}
// start the server
err := s.ListenAndServe()
if err != nil {
fmt.Println("Server failed to start: ", err)
}
}
func serveHandler(w http.ResponseWriter, r *http.Request) {
var newRequest = new(clientRequest)
newRequest.r = r
newRequest.w = w
reqChannel <- newRequest // send the new request to the request channel
fmt.Printf("Sent request to reqChannel for URL: %q\n", html.EscapeString(r.URL.Path))
}
慕田峪73311742回答
-
ibeautiful
服务器在serveHandler返回时关闭响应。一种解决方法是阻塞serveHandler直到请求被处理。在以下代码中，worker 关闭done以表示请求已完成。处理程序等待done关闭。type clientRequest struct { r *http.Request w http.ResponseWriter done chan struct{} // <-- add this line}func serveHandler(w http.ResponseWriter, r *http.Request) { var newRequest = new(clientRequest) newRequest.r = r newRequest.w = w newRequest.done = make(chan struct{}) reqChannel <- newRequest // send the new request to the request channel fmt.Printf("Sent request to reqChannel for URL: %q\n", html.EscapeString(r.URL.Path)) <-newRequest.done // wait for worker goroutine to complete}func processRequest(instanceNbr int) { fmt.Printf("processRequest started for instance #%d\n", instanceNbr) for theRequest := range reqChannel { // receive requests from the channel until it is closed fmt.Printf("Got request from reqChannel for URL: %q\n", html.EscapeString(theRequest.r.URL.Path)) fmt.Fprintf(theRequest.w, "processRequest instance #%d: URL is %q", instanceNbr, html.EscapeString(theRequest.r.URL.Path)) if f, ok := theRequest.w.(http.Flusher); ok { f.Flush() } close(theRequest.done) // signal handler that request is complete }}如果目标是限制活动处理程序的数量，那么您可以使用通道作为计数信号量来限制活动处理程序 goroutine 的数量：var reqChannel = make(chan struct{}, MaxRequests)func serveHandler(w http.ResponseWriter, r *http.Request) { reqChannel <- struct{}{} // handle the request <-reqChannel}请注意，服务器在每个连接的 goroutine 中运行处理程序。更简单的是只编写一个处理程序。大多数服务器不需要限制请求处理程序的并发性。 -
慕的地6264312
您的答案在net/http 代码的这一部分： // HTTP cannot have multiple simultaneous active requests.[*] // Until the server replies to this request, it can't read another, // so we might as well run the handler in this goroutine. // [*] Not strictly true: HTTP pipelining. We could let them all process // in parallel even if their responses need to be serialized. serverHandler{c.server}.ServeHTTP(w, w.req) if c.hijacked() { return } w.finishRequest()后ServeHTTP返回时，请求完成。所以你有几个解决方案：放弃你的工人模式并完成工作 serveHandler在完成之前等待请求被完全处理serveHandler，如下所示：（在我的本地测试）type clientRequest struct { r *http.Request w http.ResponseWriter done chan struct{}}func serveHandler(w http.ResponseWriter, r *http.Request) { var newRequest = new(clientRequest) newRequest.r = r newRequest.w = w newRequest.done = make(chan struct{}) reqChannel <- newRequest // send the new request to the request channel fmt.Printf("Sent request to reqChannel for URL: %q\n", html.EscapeString(r.URL.Path)) <-newRequest.done // wait for the worker to finish}func processRequest(instanceNbr int) { fmt.Printf("processRequest started for instance #%d\n", instanceNbr) for theRequest := range reqChannel { // receive requests from the channel until it is closed fmt.Printf("Got request from reqChannel for URL: %q\n", html.EscapeString(theRequest.r.URL.Path)) // xxx this isn't working: fmt.Fprintf(theRequest.w, "processRequest instance #%d: URL is %q", instanceNbr, html.EscapeString(theRequest.r.URL.Path)) if f, ok := theRequest.w.(http.Flusher); ok { f.Flush() } theRequest.done <- struct{}{} }}
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