72 lines
1.9 KiB
Markdown
72 lines
1.9 KiB
Markdown
|
# Rate Limiting
|
||
|
|
|
||
|
|
To limit the rate of operations per unit time, use a [time.Ticker](https://pkg.go.dev/time/#NewTicker).
|
||
|
|
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](https://pkg.go.dev/golang.org/x/time/rate) (also search pkg.go.dev for
|
||
|
|
[rate limit](http://pkg.go.dev/search?q=rate+limit)).
|
||
|
|
|
||
|
|
```go
|
||
|
|
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:
|
||
|
|
```go
|
||
|
|
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(ctx context.Context, client Client, payloads []*Payload, burstLimit int) {
|
||
|
|
throttle := make(chan time.Time, burstLimit)
|
||
|
|
|
||
|
|
ctx, cancel := context.WithCancel(ctx)
|
||
|
|
defer cancel()
|
||
|
|
|
||
|
|
go func() {
|
||
|
|
ticker := time.NewTicker(rateLimit)
|
||
|
|
defer ticker.Stop()
|
||
|
|
for t := range ticker.C {
|
||
|
|
select {
|
||
|
|
case throttle <- t:
|
||
|
|
case <-ctx.Done():
|
||
|
|
return // exit goroutine when surrounding function returns
|
||
|
|
}
|
||
|
|
}
|
||
|
|
}()
|
||
|
|
|
||
|
|
for _, payload := range payloads {
|
||
|
|
<-throttle // rate limit our client calls
|
||
|
|
go client.Call(payload)
|
||
|
|
}
|
||
|
|
}
|
||
|
|
```
|