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retry.go
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retry.go
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package pubsub
import (
"math/rand"
"sync"
"time"
)
var (
jitterRandLock sync.Mutex
jitterRand = rand.New(rand.NewSource(time.Now().UnixNano()))
)
const (
multiplier = 1.6
jitter = 0.2
)
// A RetryPolicy configures how messages in the queue should be retried.
type RetryPolicy struct {
MaxAttempts int
MinBackoff, MaxBackoff time.Duration
}
// BackoffDuration returns the backoff duration for the given number of retries.
func (retryPolicy *RetryPolicy) BackoffDuration(retries int) time.Duration {
if retries == 0 {
return 0
}
backoff, max := float64(retryPolicy.MinBackoff), float64(retryPolicy.MaxBackoff)
for backoff < max && retries > 0 {
backoff *= multiplier
retries--
}
if backoff > max {
backoff = max
}
// Randomize backoff delays so that if a cluster of requests start at
// the same time, they won't operate in lockstep.
jitterRandLock.Lock()
r := jitterRand.Float64()
jitterRandLock.Unlock()
backoff *= 1 + jitter*(r*2-1)
if backoff < 0 {
return 0
}
return time.Duration(backoff)
}