go-rate
go-rate is a rate limiter designed for a range of use cases,
including server side spam protection and preventing saturation of APIs you
consume.
It is used in production at
LangTrend to adhere to the GitHub
API rate limits.
Usage
Import github.com/beefsack/go-rate and create a new rate limiter with
the rate.New(limit int, interval time.Duration) function.
The rate limiter provides a Wait() and a Try() (bool, time.Duration) method
for both blocking and non-blocking functionality respectively.
API documentation available at godoc.org.
Examples
Blocking rate limiting
This example demonstrates limiting the output rate to 3 times per second.
package main
import (
"fmt"
"time"
"github.com/beefsack/go-rate"
)
func main() {
rl := rate.New(3, time.Second) // 3 times per second
begin := time.Now()
for i := 1; i <= 10; i++ {
rl.Wait()
fmt.Printf("%d started at %s\n", i, time.Now().Sub(begin))
}
// Output:
// 1 started at 12.584us
// 2 started at 40.13us
// 3 started at 44.92us
// 4 started at 1.000125362s
// 5 started at 1.000143066s
// 6 started at 1.000144707s
// 7 started at 2.000224641s
// 8 started at 2.000240751s
// 9 started at 2.00024244s
// 10 started at 3.000314332s
}
Blocking rate limiting with multiple limiters
This example demonstrates combining rate limiters, one limiting at once per
second, the other limiting at 2 times per 3 seconds.
package main
import (
"fmt"
"time"
"github.com/beefsack/go-rate"
)
func main() {
begin := time.Now()
rl1 := rate.New(1, time.Second) // Once per second
rl2 := rate.New(2, time.Second*3) // 2 times per 3 seconds
for i := 1; i <= 10; i++ {
rl1.Wait()
rl2.Wait()
fmt.Printf("%d started at %s\n", i, time.Now().Sub(begin))
}
// Output:
// 1 started at 11.197us
// 2 started at 1.00011941s
// 3 started at 3.000105858s
// 4 started at 4.000210639s
// 5 started at 6.000189578s
// 6 started at 7.000289992s
// 7 started at 9.000289942s
// 8 started at 10.00038286s
// 9 started at 12.000386821s
// 10 started at 13.000465465s
}
Non-blocking rate limiting
This example demonstrates non-blocking rate limiting, such as would be used to
limit spam in a chat client.
package main
import (
"fmt"
"time"
"github.com/beefsack/go-rate"
)
var rl = rate.New(3, time.Second) // 3 times per second
func say(message string) {
if ok, remaining := rl.Try(); ok {
fmt.Printf("You said: %s\n", message)
} else {
fmt.Printf("Spam filter triggered, please wait %s\n", remaining)
}
}
func main() {
for i := 1; i <= 5; i++ {
say(fmt.Sprintf("Message %d", i))
}
time.Sleep(time.Second / 2)
say("I waited half a second, is that enough?")
time.Sleep(time.Second / 2)
say("Okay, I waited a second.")
// Output:
// You said: Message 1
// You said: Message 2
// You said: Message 3
// Spam filter triggered, please wait 999.980816ms
// Spam filter triggered, please wait 999.976704ms
// Spam filter triggered, please wait 499.844795ms
// You said: Okay, I waited a second.
}