Streaming responses to a client: possible?

[Siddharth Mathur]

Hi Elazar and others,

Any tips on how to stream a response to a client? Specifically, once I have an HTML response within GoProxy from the origin server, I would like to start sending partial modified HTML content to the client (say a browser) as soon as I have something ready. Currently the API only supports sending a fully formed http.Response object. Is my interpretation correct? 

FuncRespHandler(func(resp *http.Response, ctx *ProxyCtx) *http.Response

In proxy.go, we appear to process all the filters installed, and then do a memcopy into a actual response sent to the client. Seems I can't be writing to a HttpResponseWriter  in one of my RespHandlers and doing a Flush() when the situation demands ? Or is there a way that I am missing? :) 

         resp = proxy.filterResponse(resp, ctx)

ctx.Logf("Copying response to client %v [%d]", resp.Status, resp.StatusCode)

if origBody != resp.Body {

resp.Header.Del("Content-Length")

}

copyHeaders(w.Header(), resp.Header)

w.WriteHeader(resp.StatusCode)

nr, err := io.Copy(w, resp.Body)

if err := resp.Body.Close(); err != nil {

ctx.Warnf("Can't close response body %v", err)

}

Thanks much!

Siddharth

[Elazar Leibovich]

Hi,

What you should do, is to create an http.Response object whose body is a streaming writer.

This is not ideal, and we should support creating http responses easily through goproxy. I need to think through what's the best way to expose that through the API.

For example:

package main

import (

"flag"

"io"

"log"

"net/http"

"time"

"github.com/elazarl/goproxy"

)

func main() {

addr := flag.String("addr", ":8080", "proxy listen address")

flag.Parse()

proxy := goproxy.NewProxyHttpServer()

proxy.Verbose = true

proxy.OnRequest().DoFunc(func(req *http.Request, ctx *goproxy.ProxyCtx) (*http.Request, *http.Response) {

resp := goproxy.NewResponse(req, "text/plain", http.StatusAccepted, "")

resp.ContentLength = -1

//resp.TransferEncoding = []string{"chunked"}

pr, pw := io.Pipe()

go func() {

io.WriteString(pw, "hello\n")

io.WriteString(pw, "world\n")

for i := 0; i < 10; i++ {

for j := 0; j < 100; j++ {

io.WriteString(pw, "1234567890")

}

io.WriteString(pw, "\n")

time.Sleep(1 * time.Second)

log.Println("sleeping", i)

}

pw.Close()

}()

resp.Body = pr

println("RETURNING")

return nil, resp

})

log.Fatal(http.ListenAndServe(*addr, proxy))

}

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[Siddharth Mathur]

Thanks much Elazar, using a PipeReader and PipeWriter would certainly do the trick! Great stuff. 

For the same use case, how would implement the ability to flush the partial response down the network pipe? 

http://golang.org/pkg/net/http/#Flusher

Thanks much for your time and software.

Siddharth