| /* |
| Copyright 2016 The Kubernetes Authors. |
| |
| Licensed under the Apache License, Version 2.0 (the "License"); |
| you may not use this file except in compliance with the License. |
| You may obtain a copy of the License at |
| |
| http://www.apache.org/licenses/LICENSE-2.0 |
| |
| Unless required by applicable law or agreed to in writing, software |
| distributed under the License is distributed on an "AS IS" BASIS, |
| WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| See the License for the specific language governing permissions and |
| limitations under the License. |
| */ |
| |
| package cache |
| |
| import ( |
| "sync" |
| "time" |
| |
| "github.com/hashicorp/golang-lru" |
| ) |
| |
| // Clock defines an interface for obtaining the current time |
| type Clock interface { |
| Now() time.Time |
| } |
| |
| // realClock implements the Clock interface by calling time.Now() |
| type realClock struct{} |
| |
| func (realClock) Now() time.Time { return time.Now() } |
| |
| // LRUExpireCache is a cache that ensures the mostly recently accessed keys are returned with |
| // a ttl beyond which keys are forcibly expired. |
| type LRUExpireCache struct { |
| // clock is used to obtain the current time |
| clock Clock |
| |
| cache *lru.Cache |
| lock sync.Mutex |
| } |
| |
| // NewLRUExpireCache creates an expiring cache with the given size |
| func NewLRUExpireCache(maxSize int) *LRUExpireCache { |
| return NewLRUExpireCacheWithClock(maxSize, realClock{}) |
| } |
| |
| // NewLRUExpireCacheWithClock creates an expiring cache with the given size, using the specified clock to obtain the current time. |
| func NewLRUExpireCacheWithClock(maxSize int, clock Clock) *LRUExpireCache { |
| cache, err := lru.New(maxSize) |
| if err != nil { |
| // if called with an invalid size |
| panic(err) |
| } |
| return &LRUExpireCache{clock: clock, cache: cache} |
| } |
| |
| type cacheEntry struct { |
| value interface{} |
| expireTime time.Time |
| } |
| |
| // Add adds the value to the cache at key with the specified maximum duration. |
| func (c *LRUExpireCache) Add(key interface{}, value interface{}, ttl time.Duration) { |
| c.lock.Lock() |
| defer c.lock.Unlock() |
| c.cache.Add(key, &cacheEntry{value, c.clock.Now().Add(ttl)}) |
| } |
| |
| // Get returns the value at the specified key from the cache if it exists and is not |
| // expired, or returns false. |
| func (c *LRUExpireCache) Get(key interface{}) (interface{}, bool) { |
| c.lock.Lock() |
| defer c.lock.Unlock() |
| e, ok := c.cache.Get(key) |
| if !ok { |
| return nil, false |
| } |
| if c.clock.Now().After(e.(*cacheEntry).expireTime) { |
| c.cache.Remove(key) |
| return nil, false |
| } |
| return e.(*cacheEntry).value, true |
| } |
| |
| // Remove removes the specified key from the cache if it exists |
| func (c *LRUExpireCache) Remove(key interface{}) { |
| c.lock.Lock() |
| defer c.lock.Unlock() |
| c.cache.Remove(key) |
| } |
| |
| // Keys returns all the keys in the cache, even if they are expired. Subsequent calls to |
| // get may return not found. It returns all keys from oldest to newest. |
| func (c *LRUExpireCache) Keys() []interface{} { |
| c.lock.Lock() |
| defer c.lock.Unlock() |
| return c.cache.Keys() |
| } |