bwlimit

Go net.Conn bandwidth limiter.

Only depends on the standard library.

Usage

go get github.com/linkdata/bwlimit

Ticker must be created with bwlimit.NewTicker(). The zero-value Ticker is not supported. Limits are enforced in 100ms slices with fractional carry-over between slices, so very low limits are accurate over time but can still be bursty at slice boundaries. After calling Limiter.Stop(), bandwidth metrics (Count and Rate) are no longer updated.

Example

import (
	"fmt"
	"io"
	"net/http"
	"net/http/httptest"
	"time"

	"github.com/linkdata/bwlimit"
)

func main() {
	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		w.Write([]byte("Hello world!"))
	}))
	defer srv.Close()

	// limit reads to 100 bytes/sec, unlimited writes
	lim := bwlimit.NewLimiter(100, 0)
	defer lim.Stop()

	// clone the default transport so this change is local to this client
	tp := http.DefaultTransport.(*http.Transport).Clone()
	tp.DialContext = lim.Wrap(nil).DialContext
	client := &http.Client{Transport: tp}

	// make a request and time it
	now := time.Now()
	resp, err := client.Get(srv.URL)
	elapsed := time.Since(now)

	if err == nil {
		defer resp.Body.Close()
		var body []byte
		if body, err = io.ReadAll(resp.Body); err == nil {
			fmt.Printf("%v %v %q\n", elapsed >= time.Second, lim.Reads.Count.Load() > 100, string(body))
		}
	}
}