How to log response body in gin while I redirect the initial request

Question

I'm trying to log the response body of a request that has been redirected.

func main() {
 r := gin.Default()

 eanAPI := api.NewEanAPI()

  v1 := r.Group("/v1")
 v1.POST("/*action", eanAPI.Redirect, middleware.SaveRequest())
  
  
 port := os.Getenv("PORT")
 if len(port) == 0 {
  port = "8000"
 }
 r.Run(":" + port)
}

func (api *eanAPI) Redirect(ctx *gin.Context) {
 forwardToHost := "https://jsonplaceholder.typicode.com"
 url := ctx.Request.URL.String()
 ctx.Redirect(http.StatusTemporaryRedirect, forwardToHost)
}

type bodyLogWriter struct {
 gin.ResponseWriter
 body *bytes.Buffer
}

func (w bodyLogWriter) Write(b []byte) (int, error) {
 w.body.Write(b)
 return w.ResponseWriter.Write(b)
}

func SaveRequest() gin.HandlerFunc {
 return func(c *gin.Context) {
  c.Next()
  blw := &bodyLogWriter{body: bytes.NewBufferString(""), ResponseWriter: c.Writer}
  c.Writer = blw
  c.Next()
  statusCode := c.Writer.Status()
  fmt.Println("status: ", statusCode)
  if statusCode <= 400 {
   //ok this is an request with error, let's make a record for it
   // now print body (or log in your preferred way)
   fmt.Println("Response body: " + blw.body.String())
  }
 }

Unfortunately, the body response is always empty. Maybe the redirection or the middleware is messing with my body response

When I tried with postman I can see the body response coming! You can try it by a POST on https://jsonplaceholder.typicode.com/posts. It should return a payload with an id in the body response

What am I doing wrong here?

Thanks in advance

score 3 · Accepted Answer · answered Sep 14 '18 at 13:51

The response body you're seeing in the browser/postman is from the page you're being redirected to. The page doing the actual redirecting likely has no response body, just a status and a Location header. This is the expected behavior of a redirect. If you want to try to capture the body of the page you're redirecting to, you can't actually use redirects for that (the redirect handler isn't involved in the final request); you'd have to fully proxy the request rather than redirecting it. Proxying is very different from redirecting though, so make sure that's really the behavior you're after.

How to log response body in gin while I redirect the initial request

1 Answers1