Matthias Andreas Benkard | 832a54e | 2019-01-29 09:27:38 +0100 | [diff] [blame] | 1 | /* |
| 2 | Copyright 2016 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 cache |
| 18 | |
| 19 | import ( |
| 20 | "sync" |
| 21 | "time" |
| 22 | |
| 23 | "github.com/hashicorp/golang-lru" |
| 24 | ) |
| 25 | |
| 26 | // Clock defines an interface for obtaining the current time |
| 27 | type Clock interface { |
| 28 | Now() time.Time |
| 29 | } |
| 30 | |
| 31 | // realClock implements the Clock interface by calling time.Now() |
| 32 | type realClock struct{} |
| 33 | |
| 34 | func (realClock) Now() time.Time { return time.Now() } |
| 35 | |
| 36 | // LRUExpireCache is a cache that ensures the mostly recently accessed keys are returned with |
| 37 | // a ttl beyond which keys are forcibly expired. |
| 38 | type LRUExpireCache struct { |
| 39 | // clock is used to obtain the current time |
| 40 | clock Clock |
| 41 | |
| 42 | cache *lru.Cache |
| 43 | lock sync.Mutex |
| 44 | } |
| 45 | |
| 46 | // NewLRUExpireCache creates an expiring cache with the given size |
| 47 | func NewLRUExpireCache(maxSize int) *LRUExpireCache { |
| 48 | return NewLRUExpireCacheWithClock(maxSize, realClock{}) |
| 49 | } |
| 50 | |
| 51 | // NewLRUExpireCacheWithClock creates an expiring cache with the given size, using the specified clock to obtain the current time. |
| 52 | func NewLRUExpireCacheWithClock(maxSize int, clock Clock) *LRUExpireCache { |
| 53 | cache, err := lru.New(maxSize) |
| 54 | if err != nil { |
| 55 | // if called with an invalid size |
| 56 | panic(err) |
| 57 | } |
| 58 | return &LRUExpireCache{clock: clock, cache: cache} |
| 59 | } |
| 60 | |
| 61 | type cacheEntry struct { |
| 62 | value interface{} |
| 63 | expireTime time.Time |
| 64 | } |
| 65 | |
| 66 | // Add adds the value to the cache at key with the specified maximum duration. |
| 67 | func (c *LRUExpireCache) Add(key interface{}, value interface{}, ttl time.Duration) { |
| 68 | c.lock.Lock() |
| 69 | defer c.lock.Unlock() |
| 70 | c.cache.Add(key, &cacheEntry{value, c.clock.Now().Add(ttl)}) |
| 71 | } |
| 72 | |
| 73 | // Get returns the value at the specified key from the cache if it exists and is not |
| 74 | // expired, or returns false. |
| 75 | func (c *LRUExpireCache) Get(key interface{}) (interface{}, bool) { |
| 76 | c.lock.Lock() |
| 77 | defer c.lock.Unlock() |
| 78 | e, ok := c.cache.Get(key) |
| 79 | if !ok { |
| 80 | return nil, false |
| 81 | } |
| 82 | if c.clock.Now().After(e.(*cacheEntry).expireTime) { |
| 83 | c.cache.Remove(key) |
| 84 | return nil, false |
| 85 | } |
| 86 | return e.(*cacheEntry).value, true |
| 87 | } |
| 88 | |
| 89 | // Remove removes the specified key from the cache if it exists |
| 90 | func (c *LRUExpireCache) Remove(key interface{}) { |
| 91 | c.lock.Lock() |
| 92 | defer c.lock.Unlock() |
| 93 | c.cache.Remove(key) |
| 94 | } |
| 95 | |
| 96 | // Keys returns all the keys in the cache, even if they are expired. Subsequent calls to |
| 97 | // get may return not found. It returns all keys from oldest to newest. |
| 98 | func (c *LRUExpireCache) Keys() []interface{} { |
| 99 | c.lock.Lock() |
| 100 | defer c.lock.Unlock() |
| 101 | return c.cache.Keys() |
| 102 | } |