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261 lines
5.8 KiB
261 lines
5.8 KiB
package cache
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import (
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"fmt"
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"runtime"
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"time"
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uuid "github.com/satori/go.uuid"
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)
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// Expired returns true if the item has expired
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func (item Item) Expired() bool {
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if item.Expiration == 0 {
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return false
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}
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return time.Now().UnixNano() > item.Expiration
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}
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// NewCache returns a simple in-memory cache
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func NewCache(defaultExp, cleanupInterval time.Duration) *Cache {
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items := make(map[uuid.UUID]Item)
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return newCacheWithJanitor(defaultExp, cleanupInterval, items)
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}
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func newCacheWithJanitor(defaultExp, cleanupInterval time.Duration, items map[uuid.UUID]Item) *Cache {
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cache := newCache(defaultExp, items)
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Cache := &Cache{cache}
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if cleanupInterval > 0 {
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runJanitor(cache, cleanupInterval)
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runtime.SetFinalizer(Cache, stopJanitor)
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}
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return Cache
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}
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func newCache(de time.Duration, m map[uuid.UUID]Item) *cache {
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if de == 0 {
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de = -1
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}
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c := &cache{
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defaultExpiration: de,
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items: m,
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}
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return c
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}
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// Add an item to the cache, replacing any existing item. If the duration is 0
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// (DefaultExpiration), the cache's default expiration time is used. If it is -1
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// (NoExpiration), the item never expires.
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func (c *cache) Set(k uuid.UUID, x interface{}, d time.Duration) {
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// "Inlining" of set
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var e int64
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if d == DefaultExpiration {
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d = c.defaultExpiration
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}
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if d > 0 {
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e = time.Now().Add(d).UnixNano()
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}
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c.mu.Lock()
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c.items[k] = Item{
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Object: x,
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Expiration: e,
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}
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// TODO: Calls to mu.Unlock are currently not deferred because defer
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// adds ~200 ns (as of go1.)
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c.mu.Unlock()
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}
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func (c *cache) set(k uuid.UUID, x interface{}, d time.Duration) {
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var e int64
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if d == DefaultExpiration {
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d = c.defaultExpiration
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}
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if d > 0 {
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e = time.Now().Add(d).UnixNano()
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}
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c.items[k] = Item{
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Object: x,
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Expiration: e,
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}
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}
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// Add an item to the cache, replacing any existing item, using the default
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// expiration.
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func (c *cache) SetDefault(k uuid.UUID, x interface{}) {
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c.Set(k, x, DefaultExpiration)
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}
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// Add an item to the cache only if an item doesn't already exist for the given
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// key, or if the existing item has expired. Returns an error otherwise.
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func (c *cache) Add(k uuid.UUID, x interface{}, d time.Duration) error {
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c.mu.Lock()
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_, found := c.get(k)
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if found {
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c.mu.Unlock()
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return fmt.Errorf("Item %s already exists", k)
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}
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c.set(k, x, d)
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c.mu.Unlock()
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return nil
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}
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// Set a new value for the cache key only if it already exists, and the existing
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// item hasn't expired. Returns an error otherwise.
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func (c *cache) Replace(k uuid.UUID, x interface{}, d time.Duration) error {
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c.mu.Lock()
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_, found := c.get(k)
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if !found {
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c.mu.Unlock()
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return fmt.Errorf("Item %s doesn't exist", k)
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}
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c.set(k, x, d)
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c.mu.Unlock()
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return nil
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}
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// Get an item from the cache. Returns the item or nil, and a bool indicating
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// whether the key was found.
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func (c *cache) Get(k uuid.UUID) (interface{}, bool) {
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c.mu.RLock()
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// "Inlining" of get and Expired
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item, found := c.items[k]
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if !found {
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c.mu.RUnlock()
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return nil, false
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}
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if item.Expiration > 0 {
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if time.Now().UnixNano() > item.Expiration {
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c.mu.RUnlock()
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return nil, false
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}
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}
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c.mu.RUnlock()
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return item.Object, true
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}
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// GetWithExpiration returns an item and its expiration time from the cache.
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// It returns the item or nil, the expiration time if one is set (if the item
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// never expires a zero value for time.Time is returned), and a bool indicating
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// whether the key was found.
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func (c *cache) GetWithExpiration(k uuid.UUID) (interface{}, time.Time, bool) {
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c.mu.RLock()
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// "Inlining" of get and Expired
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item, found := c.items[k]
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if !found {
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c.mu.RUnlock()
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return nil, time.Time{}, false
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}
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if item.Expiration > 0 {
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if time.Now().UnixNano() > item.Expiration {
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c.mu.RUnlock()
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return nil, time.Time{}, false
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}
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// Return the item and the expiration time
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c.mu.RUnlock()
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return item.Object, time.Unix(0, item.Expiration), true
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}
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// If expiration <= 0 (i.e. no expiration time set) then return the item
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// and a zeroed time.Time
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c.mu.RUnlock()
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return item.Object, time.Time{}, true
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}
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func (c *cache) get(k uuid.UUID) (interface{}, bool) {
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item, found := c.items[k]
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if !found {
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return nil, false
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}
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// "Inlining" of Expired
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if item.Expiration > 0 {
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if time.Now().UnixNano() > item.Expiration {
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return nil, false
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}
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}
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return item.Object, true
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}
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func (c *cache) delete(k uuid.UUID) (interface{}, bool) {
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if c.onEvicted != nil {
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if v, found := c.items[k]; found {
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delete(c.items, k)
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return v.Object, true
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}
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}
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delete(c.items, k)
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return nil, false
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}
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type keyAndValue struct {
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key uuid.UUID
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value interface{}
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}
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// Delete all expired items from the cache.
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func (c *cache) DeleteExpired() {
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var evictedItems []keyAndValue
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now := time.Now().UnixNano()
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c.mu.Lock()
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for k, v := range c.items {
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// "Inlining" of expired
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if v.Expiration > 0 && now > v.Expiration {
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ov, evicted := c.delete(k)
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if evicted {
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evictedItems = append(evictedItems, keyAndValue{k, ov})
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}
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}
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}
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c.mu.Unlock()
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for _, v := range evictedItems {
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c.onEvicted(v.key, v.value)
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}
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}
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// Sets an (optional) function that is called with the key and value when an
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// item is evicted from the cache. (Including when it is deleted manually, but
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// not when it is overwritten.) Set to nil to disable.
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func (c *cache) OnEvicted(f func(uuid.UUID, interface{})) {
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c.mu.Lock()
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c.onEvicted = f
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c.mu.Unlock()
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}
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// Delete all items from the cache.
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func (c *cache) Flush() {
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c.mu.Lock()
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c.items = map[uuid.UUID]Item{}
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c.mu.Unlock()
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}
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type janitor struct {
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Interval time.Duration
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stop chan bool
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}
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func (j *janitor) Run(c *cache) {
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ticker := time.NewTicker(j.Interval)
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for {
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select {
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case <-ticker.C:
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c.DeleteExpired()
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case <-j.stop:
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ticker.Stop()
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return
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}
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}
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}
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func stopJanitor(c *Cache) {
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c.janitor.stop <- true
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}
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func runJanitor(c *cache, ci time.Duration) {
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j := &janitor{
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Interval: ci,
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stop: make(chan bool),
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}
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c.janitor = j
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go j.Run(c)
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}
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