net/http: allow concurrent requests with different Transport proxy

[windzhu0514]

What version of Go are you using (go version)?

$ go version
go version go1.12 windows/amd64

Does this issue reproduce with the latest release?

yes

What operating system and processor architecture are you using (go env)?

go env Output

$ go env
set GOARCH=amd64
set GOOS=windows

What did you do?

there is one transport in my program
several goroutine send get request with same url
when one request return 403 , i change the proxy

What did you expect to see?

every goroutine can use it own proxy
it seems transport.Proxy is not safe for concurrent

What did you see instead?

the proxy in other goroutine request is also change

example code

package main

import (
	"io/ioutil"
	"log"
	"net"
	"net/http"
	"net/url"
	"os"
	"os/signal"
	"syscall"
	"time"
)

func main() {
	log.SetFlags(log.Lshortfile | log.Ldate | log.Ltime)
	client := &http.Client{
		Transport: &http.Transport{
			//Proxy: http.ProxyFromEnvironment,
			DialContext: (&net.Dialer{
				Timeout:   5 * time.Second,
				KeepAlive: 30 * time.Second,
			}).DialContext,
			MaxIdleConns:          100,
			IdleConnTimeout:       90 * time.Second,
			TLSHandshakeTimeout:   10 * time.Second,
			ExpectContinueTimeout: 1 * time.Second,
		},
	}

	go func() {
		req, _ := http.NewRequest(http.MethodGet, "https://www.google.com", nil)
		client.Transport.(*http.Transport).Proxy = func(request *http.Request) (url *url.URL, e error) {
			return url.Parse("http://10.101.32.12")
		}
		response, err := client.Do(req)
		if err != nil {
			log.Println(err)
			return
		}

		defer response.Body.Close()
		data, _ := ioutil.ReadAll(response.Body)
		log.Println(string(data))
	}()

	go func() {
		req, _ := http.NewRequest(http.MethodGet, "https://www.google.com", nil)
		client.Transport.(*http.Transport).Proxy = func(request *http.Request) (url *url.URL, e error) {
			return url.Parse("http://10.101.32.13")
		}
		response, err := client.Do(req)
		if err != nil {
			log.Println(err)
			return
		}

		defer response.Body.Close()
		data, _ := ioutil.ReadAll(response.Body)
		log.Println(string(data))

	}()

	chOver := make(chan os.Signal, 1)
	signal.Notify(chOver, syscall.SIGINT, syscall.SIGTERM)
	<-chOver
}

i want each request use it's own proxy

[andybons]

Can you show example code?

@bradfitz

[windzhu0514]

i have add some example code @bradfitz

[bradfitz]

Correct; you cannot set Transport.Proxy from two concurrent goroutines, just like how you can't set anything else concurrently from two concurrent goroutines.

Your Transport.Proxy function should be set before any concurrent use and then it should consult its request *http.Request input to make its routing decision.

[sinylei]

@windzhu0514 , Hi, buddy, I met exactly the same issue, I have a proxy pool, for each http request I will choose one proxy from the pool. With only one HttpClient, proxy is not concurrent safe.
Have you found any solution? Use different HttpClient for each Proxy?

[windzhu0514]

@sinylei the solution i found is writing youself Proxy select func and set transport.Proxy before before any concurrent use.
erery new request will call the proxy select func