caply

Caply is rate limiter - cheap and yet efficient way of securing your API against basic attacks or malicious overuse. Fixed Time Window rate limiter (also known as fixed window counter) is one of many known algorithms. This algo counts a number of operations per given period and returns true when limiter has enough capacity.

How to use

import "github.com/arkadyb/caply"

Create rate limiter

Use ratelimiter.NewFixedTimeWindowRateLimiter function to create new rate limiter. Function takes three arguments - maximum allowed number of operations, counter period and reference to store.Store. Where store.Store is data storage used to hold number of operations for given time window.

cp := caply.NewCaply(100, 1*time.Second, myStore) 

Store

You are free to introduce your own store by implementing store.Store interface or use one i created for Redis. If you decide to create your own, make sure all desired operations are atomic.

To create redis store, use NewRedisStore function. It takes one argument - redis.Pool.

Use rate limiter

Rate limiter exposes only one function - LimitExceeded(opName string). It takes one argument only - operation name. It then checks its defined capacity for given operation and returns true or false as for whether operation may be run or not.

Operation name may be for example user IP address or license key.

exceeded, err := cp.Exceeded("my-key")
if exceeded {
	// no capacity at the moment, try again later
} else {
	// all good, operation can run
}

License

The MIT License (MIT)