Matteo Scandolo | a428586 | 2020-12-01 18:10:10 -0800 | [diff] [blame^] | 1 | /* |
| 2 | Copyright 2015 The Kubernetes Authors. |
| 3 | |
| 4 | Licensed under the Apache License, Version 2.0 (the "License"); |
| 5 | you may not use this file except in compliance with the License. |
| 6 | You may obtain a copy of the License at |
| 7 | |
| 8 | http://www.apache.org/licenses/LICENSE-2.0 |
| 9 | |
| 10 | Unless required by applicable law or agreed to in writing, software |
| 11 | distributed under the License is distributed on an "AS IS" BASIS, |
| 12 | WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| 13 | See the License for the specific language governing permissions and |
| 14 | limitations under the License. |
| 15 | */ |
| 16 | |
| 17 | package flowcontrol |
| 18 | |
| 19 | import ( |
| 20 | "sync" |
| 21 | "time" |
| 22 | |
| 23 | "k8s.io/apimachinery/pkg/util/clock" |
| 24 | "k8s.io/utils/integer" |
| 25 | ) |
| 26 | |
| 27 | type backoffEntry struct { |
| 28 | backoff time.Duration |
| 29 | lastUpdate time.Time |
| 30 | } |
| 31 | |
| 32 | type Backoff struct { |
| 33 | sync.RWMutex |
| 34 | Clock clock.Clock |
| 35 | defaultDuration time.Duration |
| 36 | maxDuration time.Duration |
| 37 | perItemBackoff map[string]*backoffEntry |
| 38 | } |
| 39 | |
| 40 | func NewFakeBackOff(initial, max time.Duration, tc *clock.FakeClock) *Backoff { |
| 41 | return &Backoff{ |
| 42 | perItemBackoff: map[string]*backoffEntry{}, |
| 43 | Clock: tc, |
| 44 | defaultDuration: initial, |
| 45 | maxDuration: max, |
| 46 | } |
| 47 | } |
| 48 | |
| 49 | func NewBackOff(initial, max time.Duration) *Backoff { |
| 50 | return &Backoff{ |
| 51 | perItemBackoff: map[string]*backoffEntry{}, |
| 52 | Clock: clock.RealClock{}, |
| 53 | defaultDuration: initial, |
| 54 | maxDuration: max, |
| 55 | } |
| 56 | } |
| 57 | |
| 58 | // Get the current backoff Duration |
| 59 | func (p *Backoff) Get(id string) time.Duration { |
| 60 | p.RLock() |
| 61 | defer p.RUnlock() |
| 62 | var delay time.Duration |
| 63 | entry, ok := p.perItemBackoff[id] |
| 64 | if ok { |
| 65 | delay = entry.backoff |
| 66 | } |
| 67 | return delay |
| 68 | } |
| 69 | |
| 70 | // move backoff to the next mark, capping at maxDuration |
| 71 | func (p *Backoff) Next(id string, eventTime time.Time) { |
| 72 | p.Lock() |
| 73 | defer p.Unlock() |
| 74 | entry, ok := p.perItemBackoff[id] |
| 75 | if !ok || hasExpired(eventTime, entry.lastUpdate, p.maxDuration) { |
| 76 | entry = p.initEntryUnsafe(id) |
| 77 | } else { |
| 78 | delay := entry.backoff * 2 // exponential |
| 79 | entry.backoff = time.Duration(integer.Int64Min(int64(delay), int64(p.maxDuration))) |
| 80 | } |
| 81 | entry.lastUpdate = p.Clock.Now() |
| 82 | } |
| 83 | |
| 84 | // Reset forces clearing of all backoff data for a given key. |
| 85 | func (p *Backoff) Reset(id string) { |
| 86 | p.Lock() |
| 87 | defer p.Unlock() |
| 88 | delete(p.perItemBackoff, id) |
| 89 | } |
| 90 | |
| 91 | // Returns True if the elapsed time since eventTime is smaller than the current backoff window |
| 92 | func (p *Backoff) IsInBackOffSince(id string, eventTime time.Time) bool { |
| 93 | p.RLock() |
| 94 | defer p.RUnlock() |
| 95 | entry, ok := p.perItemBackoff[id] |
| 96 | if !ok { |
| 97 | return false |
| 98 | } |
| 99 | if hasExpired(eventTime, entry.lastUpdate, p.maxDuration) { |
| 100 | return false |
| 101 | } |
| 102 | return p.Clock.Since(eventTime) < entry.backoff |
| 103 | } |
| 104 | |
| 105 | // Returns True if time since lastupdate is less than the current backoff window. |
| 106 | func (p *Backoff) IsInBackOffSinceUpdate(id string, eventTime time.Time) bool { |
| 107 | p.RLock() |
| 108 | defer p.RUnlock() |
| 109 | entry, ok := p.perItemBackoff[id] |
| 110 | if !ok { |
| 111 | return false |
| 112 | } |
| 113 | if hasExpired(eventTime, entry.lastUpdate, p.maxDuration) { |
| 114 | return false |
| 115 | } |
| 116 | return eventTime.Sub(entry.lastUpdate) < entry.backoff |
| 117 | } |
| 118 | |
| 119 | // Garbage collect records that have aged past maxDuration. Backoff users are expected |
| 120 | // to invoke this periodically. |
| 121 | func (p *Backoff) GC() { |
| 122 | p.Lock() |
| 123 | defer p.Unlock() |
| 124 | now := p.Clock.Now() |
| 125 | for id, entry := range p.perItemBackoff { |
| 126 | if now.Sub(entry.lastUpdate) > p.maxDuration*2 { |
| 127 | // GC when entry has not been updated for 2*maxDuration |
| 128 | delete(p.perItemBackoff, id) |
| 129 | } |
| 130 | } |
| 131 | } |
| 132 | |
| 133 | func (p *Backoff) DeleteEntry(id string) { |
| 134 | p.Lock() |
| 135 | defer p.Unlock() |
| 136 | delete(p.perItemBackoff, id) |
| 137 | } |
| 138 | |
| 139 | // Take a lock on *Backoff, before calling initEntryUnsafe |
| 140 | func (p *Backoff) initEntryUnsafe(id string) *backoffEntry { |
| 141 | entry := &backoffEntry{backoff: p.defaultDuration} |
| 142 | p.perItemBackoff[id] = entry |
| 143 | return entry |
| 144 | } |
| 145 | |
| 146 | // After 2*maxDuration we restart the backoff factor to the beginning |
| 147 | func hasExpired(eventTime time.Time, lastUpdate time.Time, maxDuration time.Duration) bool { |
| 148 | return eventTime.Sub(lastUpdate) > maxDuration*2 // consider stable if it's ok for twice the maxDuration |
| 149 | } |