github.com/aclisp/heapster@v0.19.2-0.20160613100040-51756f899a96/Godeps/_workspace/src/k8s.io/kubernetes/pkg/util/flowcontrol/backoff.go (about)

     1  /*
     2  Copyright 2015 The Kubernetes Authors All rights reserved.
     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/kubernetes/pkg/util"
    24  	"k8s.io/kubernetes/pkg/util/integer"
    25  )
    26  
    27  type backoffEntry struct {
    28  	backoff    time.Duration
    29  	lastUpdate time.Time
    30  }
    31  
    32  type Backoff struct {
    33  	sync.Mutex
    34  	Clock           util.Clock
    35  	defaultDuration time.Duration
    36  	maxDuration     time.Duration
    37  	perItemBackoff  map[string]*backoffEntry
    38  }
    39  
    40  func NewFakeBackOff(initial, max time.Duration, tc *util.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:           util.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.Lock()
    61  	defer p.Unlock()
    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.Lock()
    94  	defer p.Unlock()
    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.Now().Sub(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.Lock()
   108  	defer p.Unlock()
   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  }