80 lines
1.6 KiB
Go
80 lines
1.6 KiB
Go
|
package backoff
|
||
|
|
|
||
|
|
import (
|
||
|
|
"runtime"
|
||
|
|
"sync"
|
||
|
|
"time"
|
||
|
|
)
|
||
|
|
|
||
|
|
// Ticker holds a channel that delivers `ticks' of a clock at times reported by a BackOff.
|
||
|
|
//
|
||
|
|
// Ticks will continue to arrive when the previous operation is still running,
|
||
|
|
// so operations that take a while to fail could run in quick succession.
|
||
|
|
type Ticker struct {
|
||
|
|
C <-chan time.Time
|
||
|
|
c chan time.Time
|
||
|
|
b BackOff
|
||
|
|
stop chan struct{}
|
||
|
|
stopOnce sync.Once
|
||
|
|
}
|
||
|
|
|
||
|
|
// NewTicker returns a new Ticker containing a channel that will send the time at times
|
||
|
|
// specified by the BackOff argument. Ticker is guaranteed to tick at least once.
|
||
|
|
// The channel is closed when Stop method is called or BackOff stops.
|
||
|
|
func NewTicker(b BackOff) *Ticker {
|
||
|
|
c := make(chan time.Time)
|
||
|
|
t := &Ticker{
|
||
|
|
C: c,
|
||
|
|
c: c,
|
||
|
|
b: b,
|
||
|
|
stop: make(chan struct{}),
|
||
|
|
}
|
||
|
|
go t.run()
|
||
|
|
runtime.SetFinalizer(t, (*Ticker).Stop)
|
||
|
|
return t
|
||
|
|
}
|
||
|
|
|
||
|
|
// Stop turns off a ticker. After Stop, no more ticks will be sent.
|
||
|
|
func (t *Ticker) Stop() {
|
||
|
|
t.stopOnce.Do(func() { close(t.stop) })
|
||
|
|
}
|
||
|
|
|
||
|
|
func (t *Ticker) run() {
|
||
|
|
c := t.c
|
||
|
|
defer close(c)
|
||
|
|
t.b.Reset()
|
||
|
|
|
||
|
|
// Ticker is guaranteed to tick at least once.
|
||
|
|
afterC := t.send(time.Now())
|
||
|
|
|
||
|
|
for {
|
||
|
|
if afterC == nil {
|
||
|
|
return
|
||
|
|
}
|
||
|
|
|
||
|
|
select {
|
||
|
|
case tick := <-afterC:
|
||
|
|
afterC = t.send(tick)
|
||
|
|
case <-t.stop:
|
||
|
|
t.c = nil // Prevent future ticks from being sent to the channel.
|
||
|
|
return
|
||
|
|
}
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
func (t *Ticker) send(tick time.Time) <-chan time.Time {
|
||
|
|
select {
|
||
|
|
case t.c <- tick:
|
||
|
|
case <-t.stop:
|
||
|
|
return nil
|
||
|
|
}
|
||
|
|
|
||
|
|
next := t.b.NextBackOff()
|
||
|
|
if next == Stop {
|
||
|
|
t.Stop()
|
||
|
|
return nil
|
||
|
|
}
|
||
|
|
|
||
|
|
return time.After(next)
|
||
|
|
}
|