95 lines
2.0 KiB
Go
95 lines
2.0 KiB
Go
package backoff
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import (
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"context"
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"sync"
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"time"
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)
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// Ticker holds a channel that delivers `ticks' of a clock at times reported by a BackOff.
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//
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// Ticks will continue to arrive when the previous operation is still running,
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// so operations that take a while to fail could run in quick succession.
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type Ticker struct {
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C <-chan time.Time
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c chan time.Time
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b BackOff
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ctx context.Context
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timer Timer
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stop chan struct{}
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stopOnce sync.Once
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}
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// NewTicker returns a new Ticker containing a channel that will send
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// the time at times specified by the BackOff argument. Ticker is
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// guaranteed to tick at least once. The channel is closed when Stop
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// method is called or BackOff stops. It is not safe to manipulate the
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// provided backoff policy (notably calling NextBackOff or Reset)
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// while the ticker is running.
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func NewTicker(b BackOff) *Ticker {
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return NewTickerWithTimer(b, &defaultTimer{})
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}
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// NewTickerWithTimer returns a new Ticker with a custom timer.
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// A default timer that uses system timer is used when nil is passed.
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func NewTickerWithTimer(b BackOff, timer Timer) *Ticker {
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c := make(chan time.Time)
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t := &Ticker{
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C: c,
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c: c,
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b: b,
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ctx: getContext(b),
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timer: timer,
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stop: make(chan struct{}),
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}
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t.b.Reset()
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go t.run()
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return t
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}
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// Stop turns off a ticker. After Stop, no more ticks will be sent.
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func (t *Ticker) Stop() {
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t.stopOnce.Do(func() { close(t.stop) })
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}
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func (t *Ticker) run() {
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c := t.c
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defer close(c)
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// Ticker is guaranteed to tick at least once.
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afterC := t.send(time.Now())
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for {
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if afterC == nil {
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return
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}
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select {
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case tick := <-afterC:
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afterC = t.send(tick)
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case <-t.stop:
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t.c = nil // Prevent future ticks from being sent to the channel.
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return
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case <-t.ctx.Done():
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return
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}
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}
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}
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func (t *Ticker) send(tick time.Time) <-chan time.Time {
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select {
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case t.c <- tick:
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case <-t.stop:
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return nil
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}
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next := t.b.NextBackOff()
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if next == Stop {
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t.Stop()
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return nil
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}
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t.timer.Start(next)
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return t.timer.C()
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}
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