Rate limiter

Dead simple distributed redis-based rate limiter.

Uses redis ZSET structure for storing events.

Basically the algorithm does this:

1. Remove events older than window time interval with ZREMRANGEBYSCORE.
2. Count elements with ZCARD.
3. If the number of elements is less than limit, than add event (allow it). Otherwise - deny.

See full lua script in the source code.

Usage

import "github.com/tetafro/rate"

// 1000 events per second
limit := NewLimit("localhost:6379", "rate-limiter", 1000)

for event := range events {
    if !limit.Allow() {
        continue // denied
    }
    doSomething() // allowed
}