/
ratelimit.go
112 lines (97 loc) · 2.58 KB
/
ratelimit.go
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package ratelimit
import (
"context"
"math"
"sync/atomic"
"time"
)
// equals to -1
var minusOne = ^uint32(0)
// Limiter allows a burst of request during the defined duration
type Limiter struct {
maxCount atomic.Uint32
count atomic.Uint32
ticker *time.Ticker
tokens chan struct{}
ctx context.Context
// internal
cancelFunc context.CancelFunc
}
func (limiter *Limiter) run(ctx context.Context) {
defer close(limiter.tokens)
for {
if limiter.count.Load() == 0 {
<-limiter.ticker.C
limiter.count.Store(limiter.maxCount.Load())
}
select {
case <-ctx.Done():
// Internal Context
limiter.ticker.Stop()
return
case <-limiter.ctx.Done():
limiter.ticker.Stop()
return
case limiter.tokens <- struct{}{}:
limiter.count.Add(minusOne)
case <-limiter.ticker.C:
limiter.count.Store(limiter.maxCount.Load())
}
}
}
// Take one token from the bucket
func (limiter *Limiter) Take() {
<-limiter.tokens
}
// CanTake checks if the rate limiter has any token
func (limiter *Limiter) CanTake() bool {
return limiter.count.Load() > 0
}
// GetLimit returns current rate limit per given duration
func (limiter *Limiter) GetLimit() uint {
return uint(limiter.maxCount.Load())
}
// GetLimit returns current rate limit per given duration
func (limiter *Limiter) SetLimit(max uint) {
limiter.maxCount.Store(uint32(max))
}
// GetLimit returns current rate limit per given duration
func (limiter *Limiter) SetDuration(d time.Duration) {
limiter.ticker.Reset(d)
}
// Stop the rate limiter canceling the internal context
func (limiter *Limiter) Stop() {
if limiter.cancelFunc != nil {
limiter.cancelFunc()
}
}
// New creates a new limiter instance with the tokens amount and the interval
func New(ctx context.Context, max uint, duration time.Duration) *Limiter {
internalctx, cancel := context.WithCancel(context.TODO())
maxCount := &atomic.Uint32{}
maxCount.Store(uint32(max))
limiter := &Limiter{
ticker: time.NewTicker(duration),
tokens: make(chan struct{}),
ctx: ctx,
cancelFunc: cancel,
}
limiter.maxCount.Store(uint32(max))
limiter.count.Store(uint32(max))
go limiter.run(internalctx)
return limiter
}
// NewUnlimited create a bucket with approximated unlimited tokens
func NewUnlimited(ctx context.Context) *Limiter {
internalctx, cancel := context.WithCancel(context.TODO())
limiter := &Limiter{
ticker: time.NewTicker(time.Millisecond),
tokens: make(chan struct{}),
ctx: ctx,
cancelFunc: cancel,
}
limiter.maxCount.Store(math.MaxUint32)
limiter.count.Store(math.MaxUint32)
go limiter.run(internalctx)
return limiter
}