Limiting bandwidth of http get

问题:

I'm a beginner to golang.

Is there any way to limit golang's http.Get() bandwidth usage? I found this: http://godoc.org/code.google.com/p/mxk/go1/flowcontrol, but I'm not sure how to piece the two together. How would I get access to the http Reader?

回答1:

There is an updated version of the package on github

You use it by wrapping an io.Reader

Here is a complete example which will show the homepage of Google veeeery sloooowly.

This wrapping an interface to make new functionality is very good Go style, and you'll see a lot of it in your journey into Go.

package main

import (
    "io"
    "log"
    "net/http"
    "os"

    "github.com/mxk/go-flowrate/flowrate"
)

func main() {
    resp, err := http.Get("http://google.com")
    if err != nil {
        log.Fatalf("Get failed: %v", err)
    }
    defer resp.Body.Close()

    // Limit to 10 bytes per second
    wrappedIn := flowrate.NewReader(resp.Body, 10)

    // Copy to stdout
    _, err = io.Copy(os.Stdout, wrappedIn)
    if err != nil {
        log.Fatalf("Copy failed: %v", err)
    }
}

回答2:

Thirdparty packages have convenient wrappers. But if you interested in how things work under the hood - it's quite easy.

package main

import (
    "io"
    "net/http"
    "os"
    "time"
)

var datachunk int64 = 500       //Bytes
var timelapse time.Duration = 1 //per seconds

func main() {
    responce, _ := http.Get("http://google.com")
    for range time.Tick(timelapse * time.Second) {
        _, err :=io.CopyN(os.Stdout, responce.Body, datachunk)
        if err!=nil {break}
    }
}

Nothing magic.