100 lines
2.9 KiB
Go
100 lines
2.9 KiB
Go
package origin
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import (
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"context"
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"time"
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)
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// Redeclare time functions so they can be overridden in tests.
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var (
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timeNow = time.Now
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timeAfter = time.After
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)
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// BackoffHandler manages exponential backoff and limits the maximum number of retries.
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// The base time period is 1 second, doubling with each retry.
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// After initial success, a grace period can be set to reset the backoff timer if
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// a connection is maintained successfully for a long enough period. The base grace period
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// is 2 seconds, doubling with each retry.
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type BackoffHandler struct {
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// MaxRetries sets the maximum number of retries to perform. The default value
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// of 0 disables retry completely.
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MaxRetries uint
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// RetryForever caps the exponential backoff period according to MaxRetries
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// but allows you to retry indefinitely.
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RetryForever bool
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// BaseTime sets the initial backoff period.
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BaseTime time.Duration
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retries uint
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resetDeadline time.Time
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}
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func (b BackoffHandler) GetBackoffDuration(ctx context.Context) (time.Duration, bool) {
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// Follows the same logic as Backoff, but without mutating the receiver.
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// This select has to happen first to reflect the actual behaviour of the Backoff function.
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select {
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case <-ctx.Done():
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return time.Duration(0), false
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default:
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}
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if !b.resetDeadline.IsZero() && timeNow().After(b.resetDeadline) {
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// b.retries would be set to 0 at this point
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return time.Second, true
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}
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if b.retries >= b.MaxRetries && !b.RetryForever {
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return time.Duration(0), false
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}
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return time.Duration(b.GetBaseTime() * 1 << b.retries), true
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}
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// BackoffTimer returns a channel that sends the current time when the exponential backoff timeout expires.
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// Returns nil if the maximum number of retries have been used.
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func (b *BackoffHandler) BackoffTimer() <-chan time.Time {
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if !b.resetDeadline.IsZero() && timeNow().After(b.resetDeadline) {
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b.retries = 0
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b.resetDeadline = time.Time{}
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}
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if b.retries >= b.MaxRetries {
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if !b.RetryForever {
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return nil
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}
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} else {
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b.retries++
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}
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return timeAfter(time.Duration(b.GetBaseTime() * 1 << (b.retries - 1)))
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}
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// Backoff is used to wait according to exponential backoff. Returns false if the
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// maximum number of retries have been used or if the underlying context has been cancelled.
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func (b *BackoffHandler) Backoff(ctx context.Context) bool {
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c := b.BackoffTimer()
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if c == nil {
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return false
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}
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select {
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case <-c:
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return true
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case <-ctx.Done():
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return false
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}
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}
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// Sets a grace period within which the the backoff timer is maintained. After the grace
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// period expires, the number of retries & backoff duration is reset.
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func (b *BackoffHandler) SetGracePeriod() {
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b.resetDeadline = timeNow().Add(time.Duration(b.GetBaseTime() * 2 << b.retries))
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}
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func (b BackoffHandler) GetBaseTime() time.Duration {
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if b.BaseTime == 0 {
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return time.Second
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}
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return b.BaseTime
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}
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// Retries returns the number of retries consumed so far.
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func (b *BackoffHandler) Retries() int {
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return int(b.retries)
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}
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