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