mirror of
https://github.com/superseriousbusiness/gotosocial
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4920229a3b
* start moving some database stuff around * continue moving db stuff around * more fiddling * more updates * and some more * and yet more * i broke SOMETHING but what, it's a mystery * tidy up * vendor ttlcache * use ttlcache * fix up some tests * rename some stuff * little reminder * some more updates
308 lines
7.8 KiB
Go
308 lines
7.8 KiB
Go
package ttlcache
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import (
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"sync"
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"time"
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)
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// CheckExpireCallback is used as a callback for an external check on item expiration
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type checkExpireCallback func(key string, value interface{}) bool
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// ExpireCallback is used as a callback on item expiration or when notifying of an item new to the cache
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type expireCallback func(key string, value interface{})
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// Cache is a synchronized map of items that can auto-expire once stale
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type Cache struct {
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mutex sync.Mutex
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ttl time.Duration
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items map[string]*item
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expireCallback expireCallback
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checkExpireCallback checkExpireCallback
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newItemCallback expireCallback
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priorityQueue *priorityQueue
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expirationNotification chan bool
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expirationTime time.Time
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skipTTLExtension bool
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shutdownSignal chan (chan struct{})
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isShutDown bool
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}
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func (cache *Cache) getItem(key string) (*item, bool, bool) {
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item, exists := cache.items[key]
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if !exists || item.expired() {
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return nil, false, false
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}
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if item.ttl >= 0 && (item.ttl > 0 || cache.ttl > 0) {
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if cache.ttl > 0 && item.ttl == 0 {
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item.ttl = cache.ttl
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}
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if !cache.skipTTLExtension {
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item.touch()
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}
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cache.priorityQueue.update(item)
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}
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expirationNotification := false
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if cache.expirationTime.After(time.Now().Add(item.ttl)) {
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expirationNotification = true
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}
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return item, exists, expirationNotification
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}
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func (cache *Cache) startExpirationProcessing() {
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timer := time.NewTimer(time.Hour)
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for {
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var sleepTime time.Duration
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cache.mutex.Lock()
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if cache.priorityQueue.Len() > 0 {
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sleepTime = time.Until(cache.priorityQueue.items[0].expireAt)
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if sleepTime < 0 && cache.priorityQueue.items[0].expireAt.IsZero() {
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sleepTime = time.Hour
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} else if sleepTime < 0 {
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sleepTime = time.Microsecond
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}
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if cache.ttl > 0 {
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sleepTime = min(sleepTime, cache.ttl)
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}
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} else if cache.ttl > 0 {
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sleepTime = cache.ttl
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} else {
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sleepTime = time.Hour
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}
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cache.expirationTime = time.Now().Add(sleepTime)
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cache.mutex.Unlock()
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timer.Reset(sleepTime)
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select {
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case shutdownFeedback := <-cache.shutdownSignal:
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timer.Stop()
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cache.mutex.Lock()
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if cache.priorityQueue.Len() > 0 {
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cache.evictjob()
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}
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cache.mutex.Unlock()
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shutdownFeedback <- struct{}{}
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return
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case <-timer.C:
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timer.Stop()
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cache.mutex.Lock()
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if cache.priorityQueue.Len() == 0 {
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cache.mutex.Unlock()
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continue
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}
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cache.cleanjob()
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cache.mutex.Unlock()
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case <-cache.expirationNotification:
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timer.Stop()
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continue
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}
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}
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}
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func (cache *Cache) evictjob() {
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// index will only be advanced if the current entry will not be evicted
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i := 0
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for item := cache.priorityQueue.items[i]; ; item = cache.priorityQueue.items[i] {
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cache.priorityQueue.remove(item)
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delete(cache.items, item.key)
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if cache.expireCallback != nil {
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go cache.expireCallback(item.key, item.data)
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}
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if cache.priorityQueue.Len() == 0 {
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return
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}
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}
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}
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func (cache *Cache) cleanjob() {
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// index will only be advanced if the current entry will not be evicted
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i := 0
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for item := cache.priorityQueue.items[i]; item.expired(); item = cache.priorityQueue.items[i] {
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if cache.checkExpireCallback != nil {
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if !cache.checkExpireCallback(item.key, item.data) {
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item.touch()
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cache.priorityQueue.update(item)
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i++
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if i == cache.priorityQueue.Len() {
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break
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}
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continue
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}
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}
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cache.priorityQueue.remove(item)
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delete(cache.items, item.key)
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if cache.expireCallback != nil {
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go cache.expireCallback(item.key, item.data)
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}
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if cache.priorityQueue.Len() == 0 {
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return
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}
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}
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}
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// Close calls Purge, and then stops the goroutine that does ttl checking, for a clean shutdown.
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// The cache is no longer cleaning up after the first call to Close, repeated calls are safe though.
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func (cache *Cache) Close() {
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cache.mutex.Lock()
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if !cache.isShutDown {
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cache.isShutDown = true
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cache.mutex.Unlock()
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feedback := make(chan struct{})
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cache.shutdownSignal <- feedback
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<-feedback
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close(cache.shutdownSignal)
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} else {
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cache.mutex.Unlock()
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}
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cache.Purge()
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}
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// Set is a thread-safe way to add new items to the map
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func (cache *Cache) Set(key string, data interface{}) {
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cache.SetWithTTL(key, data, ItemExpireWithGlobalTTL)
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}
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// SetWithTTL is a thread-safe way to add new items to the map with individual ttl
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func (cache *Cache) SetWithTTL(key string, data interface{}, ttl time.Duration) {
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cache.mutex.Lock()
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item, exists, _ := cache.getItem(key)
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if exists {
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item.data = data
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item.ttl = ttl
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} else {
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item = newItem(key, data, ttl)
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cache.items[key] = item
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}
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if item.ttl >= 0 && (item.ttl > 0 || cache.ttl > 0) {
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if cache.ttl > 0 && item.ttl == 0 {
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item.ttl = cache.ttl
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}
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item.touch()
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}
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if exists {
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cache.priorityQueue.update(item)
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} else {
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cache.priorityQueue.push(item)
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}
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cache.mutex.Unlock()
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if !exists && cache.newItemCallback != nil {
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cache.newItemCallback(key, data)
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}
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cache.expirationNotification <- true
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}
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// Get is a thread-safe way to lookup items
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// Every lookup, also touches the item, hence extending it's life
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func (cache *Cache) Get(key string) (interface{}, bool) {
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cache.mutex.Lock()
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item, exists, triggerExpirationNotification := cache.getItem(key)
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var dataToReturn interface{}
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if exists {
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dataToReturn = item.data
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}
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cache.mutex.Unlock()
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if triggerExpirationNotification {
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cache.expirationNotification <- true
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}
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return dataToReturn, exists
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}
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func (cache *Cache) Remove(key string) bool {
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cache.mutex.Lock()
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object, exists := cache.items[key]
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if !exists {
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cache.mutex.Unlock()
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return false
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}
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delete(cache.items, object.key)
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cache.priorityQueue.remove(object)
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cache.mutex.Unlock()
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return true
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}
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// Count returns the number of items in the cache
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func (cache *Cache) Count() int {
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cache.mutex.Lock()
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length := len(cache.items)
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cache.mutex.Unlock()
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return length
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}
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func (cache *Cache) SetTTL(ttl time.Duration) {
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cache.mutex.Lock()
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cache.ttl = ttl
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cache.mutex.Unlock()
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cache.expirationNotification <- true
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}
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// SetExpirationCallback sets a callback that will be called when an item expires
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func (cache *Cache) SetExpirationCallback(callback expireCallback) {
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cache.expireCallback = callback
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}
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// SetCheckExpirationCallback sets a callback that will be called when an item is about to expire
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// in order to allow external code to decide whether the item expires or remains for another TTL cycle
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func (cache *Cache) SetCheckExpirationCallback(callback checkExpireCallback) {
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cache.checkExpireCallback = callback
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}
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// SetNewItemCallback sets a callback that will be called when a new item is added to the cache
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func (cache *Cache) SetNewItemCallback(callback expireCallback) {
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cache.newItemCallback = callback
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}
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// SkipTtlExtensionOnHit allows the user to change the cache behaviour. When this flag is set to true it will
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// no longer extend TTL of items when they are retrieved using Get, or when their expiration condition is evaluated
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// using SetCheckExpirationCallback.
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func (cache *Cache) SkipTtlExtensionOnHit(value bool) {
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cache.skipTTLExtension = value
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}
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// Purge will remove all entries
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func (cache *Cache) Purge() {
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cache.mutex.Lock()
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cache.items = make(map[string]*item)
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cache.priorityQueue = newPriorityQueue()
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cache.mutex.Unlock()
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}
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// NewCache is a helper to create instance of the Cache struct
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func NewCache() *Cache {
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shutdownChan := make(chan chan struct{})
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cache := &Cache{
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items: make(map[string]*item),
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priorityQueue: newPriorityQueue(),
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expirationNotification: make(chan bool),
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expirationTime: time.Now(),
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shutdownSignal: shutdownChan,
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isShutDown: false,
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}
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go cache.startExpirationProcessing()
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return cache
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}
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func min(duration time.Duration, second time.Duration) time.Duration {
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if duration < second {
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return duration
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}
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return second
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}
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