英文:
Write pipe reading into http response in golang
问题
以下是翻译好的内容：
这是架构：
客户端发送一个POST请求给服务器A
服务器A处理请求并发送一个GET请求给服务器B
服务器B通过服务器A将响应发送给客户端
我认为最好的方法是创建一个管道，读取GET请求的响应，并将其写入POST请求的响应中，但是我遇到了很多类型问题。
func main() {
r := mux.NewRouter()
r.HandleFunc("/test/{hash}", testHandler)
log.Fatal(http.ListenAndServe(":9095", r))
}
func handleErr(err error) {
if err != nil {
log.Fatalf("%s\n", err)
}
}
func testHandler(w http.ResponseWriter, r *http.Request){
fmt.Println("FIRST REQUEST RECEIVED")
vars := mux.Vars(r)
hash := vars["hash"]
read, write := io.Pipe()
// 在没有读取器的情况下进行写入会导致死锁，因此在goroutine中进行写入
go func() {
write, _ = http.Get("http://localhost:9090/test/" + hash)
defer write.Close()
}()
w.Write(read)
}
当我运行这段代码时，我得到以下错误：
./ReverseProxy.go:61: cannot use read (type *io.PipeReader) as type []byte in argument to w.Write
有没有办法将io.PipeReader格式正确地插入到http响应中？
或者我完全错了吗？
英文:
Here is the schema :
Client sends a POST request to server A
server A process this and sends a GET to server B
server B sends a response through A to the client
I though the best idea was to make a pipe which would read the response of the GET, and write into the response of the POST, but I got many types problems.
func main() {
r := mux.NewRouter()
r.HandleFunc("/test/{hash}", testHandler)
log.Fatal(http.ListenAndServe(":9095", r))
}
func handleErr(err error) {
if err != nil {
log.Fatalf("%s\n", err)
}
}
func testHandler(w http.ResponseWriter, r *http.Request){
fmt.Println("FIRST REQUEST RECEIVED")
vars := mux.Vars(r)
hash := vars["hash"]
read, write := io.Pipe()
// writing without a reader will deadlock so write in a goroutine
go func() {
write, _ = http.Get("http://localhost:9090/test/" + hash)
defer write.Close()
}()
w.Write(read)
}
When I run this I get the following error:
./ReverseProxy.go:61: cannot use read (type *io.PipeReader) as type []byte in argument to w.Write
Is there a way, to properly insert a io.PipeReader format into an http response?
Or am I doing this in a totally wrong way?
答案1
得分: 8
你实际上并没有写入它，而是替换了管道的写入部分。
大致如下：
func testHandler(w http.ResponseWriter, r *http.Request) {
fmt.Println("FIRST REQUEST RECEIVED")
vars := mux.Vars(r)
hash := vars["hash"]
read, write := io.Pipe()
// 在没有读取器的情况下进行写入会导致死锁，因此在 goroutine 中进行写入
go func() {
defer write.Close()
resp, err := http.Get("http://localhost:9090/test/" + hash)
if err != nil {
return
}
defer resp.Body.Close()
io.Copy(write, resp.Body)
}()
io.Copy(w, read)
}
虽然如此，我同意 @JimB 的观点，对于这种情况，甚至不需要使用管道，像这样的代码应该更高效：
```go
func testHandler(w http.ResponseWriter, r *http.Request) {
vars := mux.Vars(r)
hash := vars["hash"]
resp, err := http.Get("http://localhost:9090/test/" + hash)
if err != nil {
// 处理错误
return
}
defer resp.Body.Close()
io.Copy(w, resp.Body)
}
英文:
You are not actually writing to it, you're replacing the pipe's write.
Something along the lines of:
func testHandler(w http.ResponseWriter, r *http.Request) {
fmt.Println("FIRST REQUEST RECEIVED")
vars := mux.Vars(r)
hash := vars["hash"]
read, write := io.Pipe()
// writing without a reader will deadlock so write in a goroutine
go func() {
defer write.Close()
resp, err := http.Get("http://localhost:9090/test/" + hash)
if err != nil {
return
}
defer resp.Body.Close()
io.Copy(write, resp.Body)
}()
io.Copy(w, read)
}
Although, I agree with @JimB, for this instance, the pipe isn't even needed, something like this should be more efficient:
func testHandler(w http.ResponseWriter, r *http.Request) {
vars := mux.Vars(r)
hash := vars["hash"]
resp, err := http.Get("http://localhost:9090/test/" + hash)
if err != nil {
// handle error
return
}
defer resp.Body.Close()
io.Copy(w, resp.Body)
}
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