在Golang中将管道读取写入HTTP响应

Question

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
", 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?

Answer 1

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)
}