Get size of http.Request

ghz 8months ago ⋅ 147 views

In my application, I would like to register how many bytes are transferred down the wire by my HTTP client, to keep this metric under control.

I could not find a way to accomplish this easily. The http.Request objects have a convenient method Write which fills a buffer with the HTTP packet that would travel over the network, but if I call this then the body gets close, and calling http.Client.Do on this request does not send the right packet. Cloning the request did not help.

So here is my question: how can I obtain the size (in bytes) of the request I'm about to send (or that I just sent)? Is it possible to do this also for HTTPS connections?

Answers

To obtain the size (in bytes) of the HTTP request you're about to send or that you just sent, you can use the httptrace package in Go, which provides hooks for tracing events during HTTP requests. Specifically, you can use the httptrace.ClientTrace type to trace events such as when the request is written and when the response is received.

Here's an example of how you can use httptrace to track the size of the request:

package main

import (
	"fmt"
	"io/ioutil"
	"net/http"
	"net/http/httptrace"
)

func main() {
	// Create a new HTTP request
	req, err := http.NewRequest("GET", "https://example.com", nil)
	if err != nil {
		fmt.Println("Error creating request:", err)
		return
	}

	// Create a ClientTrace to trace events
	trace := &httptrace.ClientTrace{
		WroteRequest: func(info httptrace.WroteRequestInfo) {
			fmt.Println("Bytes written in the request:", info.Written)
		},
	}

	// Attach the trace to the request's context
	req = req.WithContext(httptrace.WithClientTrace(req.Context(), trace))

	// Send the request
	resp, err := http.DefaultClient.Do(req)
	if err != nil {
		fmt.Println("Error sending request:", err)
		return
	}
	defer resp.Body.Close()

	// Read the response body
	body, err := ioutil.ReadAll(resp.Body)
	if err != nil {
		fmt.Println("Error reading response body:", err)
		return
	}

	// Print the response body
	fmt.Println("Response body:", string(body))
}

In this example:

  1. We create an HTTP request using http.NewRequest.
  2. We create a httptrace.ClientTrace object and set the WroteRequest hook function to track the number of bytes written in the request.
  3. We attach the trace to the request's context using httptrace.WithClientTrace.
  4. We send the request using http.DefaultClient.Do.
  5. When the request is written, the WroteRequest hook function is called, and we print the number of bytes written.
  6. We read and print the response body.

This approach allows you to track the size of the request before it's sent and also works for HTTPS connections.

#go