blob: e41084b0eff94364e0c40333dede3f1594b46207 [file] [log] [blame]
package backoff
import (
// 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 BackOffContext
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. It is not safe to manipulate the
// provided backoff policy (notably calling NextBackOff or Reset)
// while the ticker is running.
func NewTicker(b BackOff) *Ticker {
c := make(chan time.Time)
t := &Ticker{
C: c,
c: c,
b: ensureContext(b),
stop: make(chan struct{}),
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)
// Ticker is guaranteed to tick at least once.
afterC := t.send(time.Now())
for {
if afterC == nil {
select {
case tick := <-afterC:
afterC = t.send(tick)
case <-t.stop:
t.c = nil // Prevent future ticks from being sent to the channel.
case <-t.b.Context().Done():
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 {
return nil
return time.After(next)