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package retry
import (
"math"
"time"
"github.com/aws/aws-sdk-go-v2/internal/rand"
"github.com/aws/aws-sdk-go-v2/internal/timeconv"
)
// ExponentialJitterBackoff provides backoff delays with jitter based on the
// number of attempts.
type ExponentialJitterBackoff struct {
maxBackoff time.Duration
// precomputed number of attempts needed to reach max backoff.
maxBackoffAttempts float64
randFloat64 func() (float64, error)
}
// NewExponentialJitterBackoff returns an ExponentialJitterBackoff configured
// for the max backoff.
func NewExponentialJitterBackoff(maxBackoff time.Duration) *ExponentialJitterBackoff {
return &ExponentialJitterBackoff{
maxBackoff: maxBackoff,
maxBackoffAttempts: math.Log2(
float64(maxBackoff) / float64(time.Second)),
randFloat64: rand.CryptoRandFloat64,
}
}
// BackoffDelay returns the duration to wait before the next attempt should be
// made. Returns an error if unable get a duration.
func (j *ExponentialJitterBackoff) BackoffDelay(attempt int, err error) (time.Duration, error) {
if attempt > int(j.maxBackoffAttempts) {
return j.maxBackoff, nil
}
b, err := j.randFloat64()
if err != nil {
return 0, err
}
// [0.0, 1.0) * 2 ^ attempts
ri := int64(1 << uint64(attempt))
delaySeconds := b * float64(ri)
return timeconv.FloatSecondsDur(delaySeconds), nil
}
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