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// Copyright 2016 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package gensupport
import (
// BackoffStrategy defines the set of functions that a backoff-er must
// implement.
type BackoffStrategy interface {
// Pause returns the duration of the next pause and true if the operation should be
// retried, or false if no further retries should be attempted.
Pause() (time.Duration, bool)
// Reset restores the strategy to its initial state.
// ExponentialBackoff performs exponential backoff as per
// The initial pause time is given by Base.
// Once the total pause time exceeds Max, Pause will indicate no further retries.
type ExponentialBackoff struct {
Base time.Duration
Max time.Duration
total time.Duration
n uint
// Pause returns the amount of time the caller should wait.
func (eb *ExponentialBackoff) Pause() (time.Duration, bool) {
if > eb.Max {
return 0, false
// The next pause is selected from randomly from [0, 2^n * Base).
d := time.Duration(rand.Int63n((1 << eb.n) * int64(eb.Base))) += d
return d, true
// Reset resets the backoff strategy such that the next Pause call will begin
// counting from the start. It is not safe to call concurrently with Pause.
func (eb *ExponentialBackoff) Reset() {
eb.n = 0 = 0