RateLimiter for Go, use TokenBucket algorithm, base on both Memory and Redis.

It's transformed from clj-rate-limiter in clojure

and it use functional-options-style API.

go get github.com/lysu/go-rate-limiter

Create an in-memory rate limiter with maximum 100 requsts in 1 seconds:

import (
  limiter "github.com/lysu/go-rate-limiter"
)

allow := limiter.RateLimiter(limiter.UseMemory(), limiter.BucketLimit(1*time,Second, 100))()
fmt.Println(allow("key1"))
fmt.Println(allow("key2"))

The limiter.UseMemory() let limiter use memory storge, limiter.BucketLimit(1*time,Second, 100) sets the time window size and the maximum requests in the window. After the limiter is created, you can use allow("key") to test if the request can be passed.The string key is present the type of the request.A group requests of the same key are rate limited by the limiter.

In a cluster, you can choose use redis as backend storage, and we choose redigo as reids client

var redisPool = &redis.Pool{
        MaxIdle:     3,
    IdleTimeout: 240 * time.Second,
    Dial: func() (redis.Conn, error) {
	    c, err := redis.Dial("tcp", "127.0.0.1:6379")
	    if err != nil {
		    return nil, err
	    }
	    return c, err
    },
    TestOnBorrow: func(c redis.Conn, t time.Time) error {
	    _, err := c.Do("PING")
	    return err
    },
}
allow := limiter.RateLimiter(limiter.UseRedis(redisPool), limiter.BucketLimit(1*time,Second, 100))()
fmt.Println(allow("key1"))
fmt.Println(allow("key2"))

You can set min period between two requests, by use MinPeriod option.

allow := limiter.RateLimiter(limiter.UseRedis(redisPool), limiter.MinPeriod(10*time.Millisecond))()
fmt.Println(allow("key1"))
fmt.Println(allow("key2"))

The rate limiter will still add the request to backend storage even if the requests are too many. It may consume too much memory in backend storage,so i provide a option FloodThreshold for such situation.

If you set FloodThreshold,when current requests number in storage is greater or equalt to FloodThreshold * MaxInInterval, then the limiter will not add the new request to backend storage until next time window.

allow := limiter.RateLimiter(limiter.UseRedis(redisPool), limiter.BucketLimit(1000*time.Millisecond, 10), limiter.FloodThreshold(5))()

more usage can see UnitTest