Proxy middleware - unreachable, could not forward: net/http: HTTP/1.x transport connection broken

[ddhvn]

Issue Description

Use function Skipper in middleware.ProxyConfig{} to skip the middleware with some conditions, It does not work when getting value from request body of echo.Context.

Checklist

• Dependencies installed
• No typos
• Searched existing issues and docs

Expected behaviour

The request is forwarded to targets when using request body of echo.Context

Working code to debug

e.Use(middleware.ProxyWithConfig(middleware.ProxyConfig{
		Skipper: func(c echo.Context) bool {
			if c.Request().URL.Path != "/api/order/create" {
				return true
			}
			serviceID := c.FormValue("service_id") // if this line is removed, the proxy works, otherwise got the error below
			// check condition with serviceID...
		
			return false
		},
		Balancer: middleware.NewRoundRobinBalancer(targets),
		Rewrite: map[string]string{
			"/api/order/create": "/api/saas/order/create",
		},
	}))

Got Error

"internal": "code=502, message=remote order-wrapper(http://localhost:9091) unreachable, could not forward: net/http: HTTP/1.x transport connection broken: http: ContentLength=1750 with Body length 0",

Version/commit

Echo version: github.com/labstack/echo/v4 v4.1.17
Go version: 1.14

[aldas]

Just guessing. I assume problem is here that by calling FormValue you are reading request body and after that underlying request writer (body) is not usable anymore by Go standard library reverse proxy.

See https://stackoverflow.com/questions/43021058/golang-read-request-body-multiple-times

[ddhvn]

Thanks for your guess @aldas, I've solved the issue by reading request body by ioutil.ReadAll then restore c.Request().Body by ioutil.NopCloser

  body, err := ioutil.ReadAll(c.Request().Body)
  if err != nil {
     log.Panicf("Failed to read request body, %v", err)
  }
  // Restore the io.ReadCloser to its original state
  c.Request().Body = ioutil.NopCloser(bytes.NewBuffer(body))

[aldas]

note: this means that you are buffering whole request body into memory - this will impact your application memory consumption. It would be probably best to check request content type header before your read everything into buffer so at least requests that are not form posts could be proxied more efficiently