RateLimiting

Rate Limiting

To limit the rate of operations per unit time, use a time.Ticker. This works well for rates up to tens of operations per second. For higher rates, prefer a token bucket rate limiter such as golang.org/x/time/rate.Limiter (also search godoc.org for rate limit).

import "time"

const rateLimit = time.Second / 10  // 10 calls per second

// Client is an interface that calls something with a payload.
type Client interface {
  Call(*Payload)
}

// Payload is some payload a Client would send in a call.
type Payload struct {}

// RateLimitCall rate limits client calls with the payloads.
func RateLimitCall(client Client, payloads []*Payload) {
  throttle := time.Tick(rateLimit)

  for _, payload := range payloads {
    <-throttle  // rate limit our client calls
    go client.Call(payload)
  }
}

To allow some bursts, add a buffer to the throttle:

import "time"

const rateLimit = time.Second / 10  // 10 calls per second

// Client is an interface that calls something with a payload.
type Client interface {
  Call(*Payload)
}

// Payload is some payload a Client would send in a call.
type Payload struct {}

// BurstRateLimitCall allows burst rate limiting client calls with the
// payloads.
func BurstRateLimitCall(client Client, payloads []*Payload, burstLimit int) {
  ticker := time.NewTicker(rateLimit)
  defer ticker.Stop()

  throttle := make(chan time.Time, burstLimit)

  go func() {
    for t := range ticker.C {
      throttle <- t
    }  // for loop will complete the range after tick.Stop() closes tick.C
  }()

  for _, payload := range payloads {
    <-throttle  // rate limit our client calls
    go client.Call(payload)
  }
}