Way too many events allowed when burst is not 1

[zikaeroh]

Run:

package main

import (
	"log"
	"time"

	"github.com/go-redis/redis/v7"
	"github.com/go-redis/redis_rate/v8"
)

func main() {
	const (
		perPeriod = 17
		period    = 30 * time.Second
	)

	rdb := redis.NewClient(&redis.Options{
		Addr: "localhost:6379",
	})
	defer rdb.Close()

	limiter := redis_rate.NewLimiter(rdb, &redis_rate.Limit{
		Burst:  perPeriod,
		Rate:   perPeriod,
		Period: period,
	})

	allowed := 0
	start := time.Now()

	for i := 0; i < 30; i++ {
		r, _ := limiter.Allow("key")
		if r.Allowed {
			allowed++
		}

		time.Sleep(time.Second / 4)

		r, _ = limiter.Allow("key")
		if r.Allowed {
			allowed++
		}

		time.Sleep(3 * time.Second / 4)
	}

	log.Printf("Allowed %d in %v, expected %d", allowed, time.Since(start), perPeriod)
}

And I get:

2019/08/31 18:25:53 Allowed 32 in 30.073504489s, expected 17

The rate was set to 17 per 30 seconds, but each run allows much more than 17. Change burst to 1:

2019/08/31 18:28:47 Allowed 18 in 30.079242485s, expected 17

Which makes a little more sense. If you make the burst go even higher, then you can end up allowing every event, but I'm assuming a burst above the rate is not a correct configuration.

[zikaeroh]

Perhaps I'm just not understanding how this new algorithm operates. I guess the burst is the initial token count and you can have any number of them, such that the use rate won't match the actual rate limit set. Unfortunately not the way I was hoping this package would work...

[zikaeroh]

I guess I'll close this; I was hoping it'd behave like a rolling window rate limiter, but that isn't the case. Just wrote my own with sorted sets of timestamps instead. 😛

[vmihailenco]

Do you have a link to share? :)

I guess the burst is the initial token count and you can have any number of them, such that the use rate won't match the actual rate limit set.

Yeah, you may think of it as the bucket size with is re-filled at the given rate.

[zikaeroh]

If you mean a link to my code, not yet, no.