ratelim
ratelim is a Go module for managing rate limiters, particularly for use by an http.Client within a
custom http.RoundTripper to rate limit outgoing requests.
Usage
A common use case is to create an http.RoundTripper which will apply a rate limiter per target origin:
package main
import (
"fmt"
"log"
"net/http"
"sync"
"github.com/milo-minderbinder/ratelim"
)
func main() {
// Create a client with a 10.0 request/second rate limit per origin, with a 2 request burst limit:
client := http.Client{
Transport: ratelim.PerOriginRoundTripper(10.0, 2, http.DefaultTransport),
}
reqs := make([]*http.Request, 5)
for i := 0; i < 5; i++ {
req, err := http.NewRequest(http.MethodGet, fmt.Sprintf("http://example.com/%d", i), nil)
if err != nil {
log.Fatalln(err)
}
reqs = append(reqs, req)
}
// Start sending all requests concurrently but cap the actual request rate according to the configured rate limiter:
var wg sync.WaitGroup
for i := range reqs {
wg.Add(1)
go func(i int) {
defer wg.Done()
resp, err := client.Do(reqs[i])
if err != nil {
fmt.Println(err)
}
fmt.Printf("%s %s\n", resp.Status, resp.Request.URL.String())
}(i)
}
wg.Wait()
}