README
¶
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.
}
Authors
Documentation
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Index ¶
Constants ¶
This section is empty.
Variables ¶
This section is empty.
Functions ¶
This section is empty.
Types ¶
type RateLimiter ¶
type RateLimiter struct {
// contains filtered or unexported fields
}
A RateLimiter limits the rate at which an action can be performed. It applies neither smoothing (like one could achieve in a token bucket system) nor does it offer any conception of warmup, wherein the rate of actions granted are steadily increased until a steady throughput equilibrium is reached.
func New ¶
func New(limit int, interval time.Duration) *RateLimiter
New creates a new rate limiter for the limit and interval.
func (*RateLimiter) Try ¶
func (r *RateLimiter) Try() (ok bool, remaining time.Duration)
Try returns true if under the rate limit, or false if over and the remaining time before the rate limit expires.
func (*RateLimiter) Wait ¶
func (r *RateLimiter) Wait()
Wait blocks if the rate limit has been reached. Wait offers no guarantees of fairness for multiple actors if the allowed rate has been temporarily exhausted.
Source Files