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// Package ratelimiter implements the Leaky Bucket ratelimiting algorithm with memcached and in-memory backends.
package ratelimiter
import (
"time"
)
type LeakyBucket struct {
Size uint16
Fill float64
LeakInterval time.Duration // time.Duration for 1 unit of size to leak
Lastupdate time.Time
Now func() time.Time
}
func NewLeakyBucket(size uint16, leakInterval time.Duration) *LeakyBucket {
bucket := LeakyBucket{
Size: size,
Fill: 0,
LeakInterval: leakInterval,
Now: time.Now,
Lastupdate: time.Now(),
}
return &bucket
}
func (b *LeakyBucket) updateFill() {
now := b.Now()
if b.Fill > 0 {
elapsed := now.Sub(b.Lastupdate)
b.Fill -= float64(elapsed) / float64(b.LeakInterval)
if b.Fill < 0 {
b.Fill = 0
}
}
b.Lastupdate = now
}
func (b *LeakyBucket) Pour(amount uint16) bool {
b.updateFill()
var newfill float64 = b.Fill + float64(amount)
if newfill > float64(b.Size) {
return false
}
b.Fill = newfill
return true
}
// The time at which this bucket will be completely drained
func (b *LeakyBucket) DrainedAt() time.Time {
return b.Lastupdate.Add(time.Duration(b.Fill * float64(b.LeakInterval)))
}
// The duration until this bucket is completely drained
func (b *LeakyBucket) TimeToDrain() time.Duration {
return b.DrainedAt().Sub(b.Now())
}
func (b *LeakyBucket) TimeSinceLastUpdate() time.Duration {
return b.Now().Sub(b.Lastupdate)
}
type LeakyBucketSer struct {
Size uint16
Fill float64
LeakInterval time.Duration // time.Duration for 1 unit of size to leak
Lastupdate time.Time
}
func (b *LeakyBucket) Serialise() *LeakyBucketSer {
bucket := LeakyBucketSer{
Size: b.Size,
Fill: b.Fill,
LeakInterval: b.LeakInterval,
Lastupdate: b.Lastupdate,
}
return &bucket
}
func (b *LeakyBucketSer) DeSerialise() *LeakyBucket {
bucket := LeakyBucket{
Size: b.Size,
Fill: b.Fill,
LeakInterval: b.LeakInterval,
Lastupdate: b.Lastupdate,
Now: time.Now,
}
return &bucket
}
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