vendor/google.golang.org/api/gensupport/backoff.go

   1 // Copyright 2016 The Go Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style
   3 // license that can be found in the LICENSE file.
   4
   5 package gensupport
   6
   7 import (
   8         "math/rand"
   9         "time"
  10 )
  11
  12 // BackoffStrategy defines the set of functions that a backoff-er must
  13 // implement.
  14 type BackoffStrategy interface {
  15         // Pause returns the duration of the next pause and true if the operation should be
  16         // retried, or false if no further retries should be attempted.
  17         Pause() (time.Duration, bool)
  18
  19         // Reset restores the strategy to its initial state.
  20         Reset()
  21 }
  22
  23 // ExponentialBackoff performs exponential backoff as per https://en.wikipedia.org/wiki/Exponential_backoff.
  24 // The initial pause time is given by Base.
  25 // Once the total pause time exceeds Max, Pause will indicate no further retries.
  26 type ExponentialBackoff struct {
  27         Base  time.Duration
  28         Max   time.Duration
  29         total time.Duration
  30         n     uint
  31 }
  32
  33 // Pause returns the amount of time the caller should wait.
  34 func (eb *ExponentialBackoff) Pause() (time.Duration, bool) {
  35         if eb.total > eb.Max {
  36                 return 0, false
  37         }
  38
  39         // The next pause is selected from randomly from [0, 2^n * Base).
  40         d := time.Duration(rand.Int63n((1 << eb.n) * int64(eb.Base)))
  41         eb.total += d
  42         eb.n++
  43         return d, true
  44 }
  45
  46 // Reset resets the backoff strategy such that the next Pause call will begin
  47 // counting from the start. It is not safe to call concurrently with Pause.
  48 func (eb *ExponentialBackoff) Reset() {
  49         eb.n = 0
  50         eb.total = 0
  51 }