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125 lines
2.9 KiB
Go
125 lines
2.9 KiB
Go
package tb
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import (
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"math"
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"sync"
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"time"
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)
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// Throttler is a thread-safe wrapper around a map of buckets and an easy to
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// use API for generic throttling.
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type Throttler struct {
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mu sync.RWMutex
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freq time.Duration
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buckets map[string]*Bucket
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closing chan struct{}
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}
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// NewThrottler returns a Throttler with a single filler go-routine for all
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// its Buckets which ticks every freq.
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// The number of tokens added on each tick for each bucket is computed
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// dynamically to be even accross the duration of a second.
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//
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// If freq <= 0, the filling go-routine won't be started.
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func NewThrottler(freq time.Duration) *Throttler {
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th := &Throttler{
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freq: freq,
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buckets: map[string]*Bucket{},
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closing: make(chan struct{}),
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}
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if freq > 0 {
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go th.fill(freq)
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}
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return th
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}
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// Bucket returns a Bucket with rate capacity, keyed by key.
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//
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// If a Bucket (key, rate) doesn't exist yet, it is created.
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//
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// You must call Close when you're done with the Throttler in order to not leak
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// a go-routine and a system-timer.
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func (t *Throttler) Bucket(key string, rate int64) *Bucket {
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t.mu.Lock()
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defer t.mu.Unlock()
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b, ok := t.buckets[key]
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if !ok {
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b = NewBucket(rate, -1)
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b.inc = int64(math.Floor(.5 + (float64(b.capacity) * t.freq.Seconds())))
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b.freq = t.freq
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t.buckets[key] = b
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}
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return b
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}
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// Wait waits for n amount of tokens to be available.
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// If n tokens are immediatelly available it doesn't sleep. Otherwise, it sleeps
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// the minimum amount of time required for the remaining tokens to be available.
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// It returns the wait duration.
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//
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// If a Bucket (key, rate) doesn't exist yet, it is created.
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// If freq < 1/rate seconds, the effective wait rate won't be correct.
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//
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// You must call Close when you're done with the Throttler in order to not leak
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// a go-routine and a system-timer.
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func (t *Throttler) Wait(key string, n, rate int64) time.Duration {
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return t.Bucket(key, rate).Wait(n)
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}
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// Halt returns a bool indicating if the Bucket identified by key and rate has
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// n amount of tokens. If it doesn't, the taken tokens are added back to the
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// bucket.
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//
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// If a Bucket (key, rate) doesn't exist yet, it is created.
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// If freq < 1/rate seconds, the results won't be correct.
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//
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// You must call Close when you're done with the Throttler in order to not leak
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// a go-routine and a system-timer.
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func (t *Throttler) Halt(key string, n, rate int64) bool {
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b := t.Bucket(key, rate)
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if got := b.Take(n); got != n {
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b.Put(got)
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return true
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}
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return false
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}
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// Close stops filling the Buckets, closing the filling go-routine.
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func (t *Throttler) Close() error {
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close(t.closing)
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t.mu.RLock()
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defer t.mu.RUnlock()
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for _, b := range t.buckets {
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b.Close()
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}
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return nil
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}
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func (t *Throttler) fill(freq time.Duration) {
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ticker := time.NewTicker(freq)
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defer ticker.Stop()
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for _ = range ticker.C {
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select {
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case <-t.closing:
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return
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default:
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}
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t.mu.RLock()
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for _, b := range t.buckets {
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b.Put(b.inc)
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}
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t.mu.RUnlock()
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}
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}
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