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bucket.go
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bucket.go
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package ioshape
import (
"sync"
"sync/atomic"
"time"
)
type bucketTokenRequest struct {
count int64
callback chan int64
priority int
}
type bucketTokenReturn struct {
count int64
}
// Bucket shapes traffic by given rate, burst and Reader/Writer priorities.
type Bucket struct {
tokens int64
n int64
k int64
b int64
m int64
setMu sync.RWMutex
ticker *time.Ticker
ticks int64
stopCh chan struct{}
stopped int32
tokenRequests chan *bucketTokenRequest
tokenReturns chan *bucketTokenReturn
}
// NewBucket returns a new Bucket.
func NewBucket() (bu *Bucket) {
bu = &Bucket{}
bu.ticker = time.NewTicker(time.Second / freq)
bu.stopCh = make(chan struct{}, 1)
bu.tokenRequests = make(chan *bucketTokenRequest)
bu.tokenReturns = make(chan *bucketTokenReturn)
go bu.timer()
return
}
// NewBucketRate returns a new Bucket and sets rate.
func NewBucketRate(rate int64) (bu *Bucket) {
bu = NewBucket()
bu.SetRate(rate)
return
}
func (bu *Bucket) timer() {
var n, k, b, m int64
for {
select {
case <-bu.stopCh:
atomic.StoreInt32(&bu.stopped, 1)
time.Sleep(10 * time.Millisecond)
for ok := true; ok; {
select {
case tokenRequest := <-bu.tokenRequests:
tokenRequest.callback <- tokenRequest.count
default:
ok = false
}
}
return
case <-bu.ticker.C:
bu.setMu.RLock()
n = bu.n
k = bu.k
b = bu.b
m = bu.m
bu.setMu.RUnlock()
bu.tokens += n
if bu.ticks%freq < k {
bu.tokens++
}
if bu.tokens > b {
bu.tokens = b
}
bu.ticks++
if bu.ticks > freq {
bu.ticks = 0
}
case tokenRequest := <-bu.tokenRequests:
count := tokenRequest.count
if count > bu.tokens {
count = bu.tokens
}
if count > m {
count = m
}
if tokenRequest.priority > int((priorityScale*bu.ticks/freq)%priorityScale) {
count = 0
}
tokenRequest.callback <- count
bu.tokens -= count
case tokenReturn := <-bu.tokenReturns:
count := tokenReturn.count
bu.tokens += count
if bu.tokens > b {
bu.tokens = b
}
}
}
}
// Stop turns off a bucket. After Stop, bucket won't shape traffic. Stop
// must be call to free resources, after the bucket doesn't be needing.
func (bu *Bucket) Stop() {
bu.ticker.Stop()
select {
case bu.stopCh <- struct{}{}:
default:
}
}
// Set sets buckets rate and burst in bytes per second. The burst should be
// greater or equal than the rate. Otherwise burst will be equal rate.
func (bu *Bucket) Set(rate, burst int64) {
if rate < 0 {
return
}
bu.setMu.Lock()
defer bu.setMu.Unlock()
if rate > burst {
burst = rate
}
bu.n = rate / freq
bu.k = rate % freq
bu.b = burst + bu.n
bu.m = bu.n / chunkDiv
if bu.m == 0 {
bu.m = 1
}
}
// SetRate sets rate and burst to the rate in bytes per second.
func (bu *Bucket) SetRate(rate int64) {
bu.Set(rate, 0)
}
func (bu *Bucket) getTokens(count int64, priority int) int64 {
callback := make(chan int64)
if count > 0 && bu.stopped == 0 {
bu.tokenRequests <- &bucketTokenRequest{
count: count,
callback: callback,
priority: priority}
return <-callback
}
return count
}
func (bu *Bucket) giveTokens(count int64) {
bu.tokenReturns <- &bucketTokenReturn{
count: count}
}