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// Copyright 2011, 2012, 2013 Canonical Ltd.
// Licensed under the AGPLv3, see LICENCE file for details.
package utils
import (
"time"
)
// The Attempt and AttemptStrategy types are copied from those in launchpad.net/goamz/aws.
// AttemptStrategy represents a strategy for waiting for an action
// to complete successfully.
type AttemptStrategy struct {
Total time.Duration // total duration of attempt.
Delay time.Duration // interval between each try in the burst.
Min int // minimum number of retries; overrides Total
}
type Attempt struct {
strategy AttemptStrategy
last time.Time
end time.Time
force bool
count int
}
// Start begins a new sequence of attempts for the given strategy.
func (s AttemptStrategy) Start() *Attempt {
now := time.Now()
return &Attempt{
strategy: s,
last: now,
end: now.Add(s.Total),
force: true,
}
}
// Next waits until it is time to perform the next attempt or returns
// false if it is time to stop trying.
// It always returns true the first time it is called - we are guaranteed to
// make at least one attempt.
func (a *Attempt) Next() bool {
now := time.Now()
sleep := a.nextSleep(now)
if !a.force && !now.Add(sleep).Before(a.end) && a.strategy.Min <= a.count {
return false
}
a.force = false
if sleep > 0 && a.count > 0 {
time.Sleep(sleep)
now = time.Now()
}
a.count++
a.last = now
return true
}
func (a *Attempt) nextSleep(now time.Time) time.Duration {
sleep := a.strategy.Delay - now.Sub(a.last)
if sleep < 0 {
return 0
}
return sleep
}
// HasNext returns whether another attempt will be made if the current
// one fails. If it returns true, the following call to Next is
// guaranteed to return true.
func (a *Attempt) HasNext() bool {
if a.force || a.strategy.Min > a.count {
return true
}
now := time.Now()
if now.Add(a.nextSleep(now)).Before(a.end) {
a.force = true
return true
}
return false
}
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