github.com/timstclair/heapster@v0.20.0-alpha1/Godeps/_workspace/src/k8s.io/kubernetes/pkg/util/cache.go (about) 1 /* 2 Copyright 2014 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 util 18 19 import ( 20 "sync" 21 ) 22 23 const ( 24 shardsCount int = 32 25 ) 26 27 type Cache []*cacheShard 28 29 func NewCache(maxSize int) Cache { 30 cache := make(Cache, shardsCount) 31 for i := 0; i < shardsCount; i++ { 32 cache[i] = &cacheShard{ 33 items: make(map[uint64]interface{}), 34 maxSize: maxSize / shardsCount, 35 } 36 } 37 return cache 38 } 39 40 func (c Cache) getShard(index uint64) *cacheShard { 41 return c[index%uint64(shardsCount)] 42 } 43 44 // Returns true if object already existed, false otherwise. 45 func (c *Cache) Add(index uint64, obj interface{}) bool { 46 return c.getShard(index).add(index, obj) 47 } 48 49 func (c *Cache) Get(index uint64) (obj interface{}, found bool) { 50 return c.getShard(index).get(index) 51 } 52 53 type cacheShard struct { 54 items map[uint64]interface{} 55 sync.RWMutex 56 maxSize int 57 } 58 59 // Returns true if object already existed, false otherwise. 60 func (s *cacheShard) add(index uint64, obj interface{}) bool { 61 s.Lock() 62 defer s.Unlock() 63 _, isOverwrite := s.items[index] 64 s.items[index] = obj 65 if len(s.items) > s.maxSize { 66 var randomKey uint64 67 for randomKey = range s.items { 68 break 69 } 70 delete(s.items, randomKey) 71 } 72 return isOverwrite 73 } 74 75 func (s *cacheShard) get(index uint64) (obj interface{}, found bool) { 76 s.RLock() 77 defer s.RUnlock() 78 obj, found = s.items[index] 79 return 80 }