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package ratecounter
import (
"strconv"
"sync/atomic"
"time"
)
// A RateCounter is a thread-safe counter which returns the number of times
// 'Incr' has been called in the last interval
type RateCounter struct {
counter Counter
interval time.Duration
resolution int
partials []Counter
current int32
running int32
}
// NewRateCounter Constructs a new RateCounter, for the interval provided
func NewRateCounter(intrvl time.Duration) *RateCounter {
ratecounter := &RateCounter{
interval: intrvl,
running: 0,
}
return ratecounter.WithResolution(20)
}
// WithResolution determines the minimum resolution of this counter, default is 20
func (r *RateCounter) WithResolution(resolution int) *RateCounter {
if resolution < 1 {
panic("RateCounter resolution cannot be less than 1")
}
r.resolution = resolution
r.partials = make([]Counter, resolution)
r.current = 0
return r
}
func (r *RateCounter) run() {
if ok := atomic.CompareAndSwapInt32(&r.running, 0, 1); !ok {
return
}
go func() {
ticker := time.NewTicker(time.Duration(float64(r.interval) / float64(r.resolution)))
for range ticker.C {
current := atomic.LoadInt32(&r.current)
next := (int(current) + 1) % r.resolution
r.counter.Incr(-1 * r.partials[next].Value())
r.partials[next].Reset()
atomic.CompareAndSwapInt32(&r.current, current, int32(next))
if r.counter.Value() == 0 {
atomic.StoreInt32(&r.running, 0)
ticker.Stop()
return
}
}
}()
}
// Incr Add an event into the RateCounter
func (r *RateCounter) Incr(val int64) {
r.counter.Incr(val)
r.partials[atomic.LoadInt32(&r.current)].Incr(val)
r.run()
}
// Rate Return the current number of events in the last interval
func (r *RateCounter) Rate() int64 {
return r.counter.Value()
}
func (r *RateCounter) String() string {
return strconv.FormatInt(r.counter.Value(), 10)
}
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