From aaafafbdfe07754b771b824c71034f65c77cc76e Mon Sep 17 00:00:00 2001 From: Dimitri Sokolyuk Date: Wed, 25 Jul 2018 09:18:08 +0200 Subject: add title caching --- vendor/github.com/hashicorp/golang-lru/2q.go | 223 +++++++++++++++++++++++++++ 1 file changed, 223 insertions(+) create mode 100644 vendor/github.com/hashicorp/golang-lru/2q.go (limited to 'vendor/github.com/hashicorp/golang-lru/2q.go') diff --git a/vendor/github.com/hashicorp/golang-lru/2q.go b/vendor/github.com/hashicorp/golang-lru/2q.go new file mode 100644 index 0000000..e474cd0 --- /dev/null +++ b/vendor/github.com/hashicorp/golang-lru/2q.go @@ -0,0 +1,223 @@ +package lru + +import ( + "fmt" + "sync" + + "github.com/hashicorp/golang-lru/simplelru" +) + +const ( + // Default2QRecentRatio is the ratio of the 2Q cache dedicated + // to recently added entries that have only been accessed once. + Default2QRecentRatio = 0.25 + + // Default2QGhostEntries is the default ratio of ghost + // entries kept to track entries recently evicted + Default2QGhostEntries = 0.50 +) + +// TwoQueueCache is a thread-safe fixed size 2Q cache. +// 2Q is an enhancement over the standard LRU cache +// in that it tracks both frequently and recently used +// entries separately. This avoids a burst in access to new +// entries from evicting frequently used entries. It adds some +// additional tracking overhead to the standard LRU cache, and is +// computationally about 2x the cost, and adds some metadata over +// head. The ARCCache is similar, but does not require setting any +// parameters. +type TwoQueueCache struct { + size int + recentSize int + + recent simplelru.LRUCache + frequent simplelru.LRUCache + recentEvict simplelru.LRUCache + lock sync.RWMutex +} + +// New2Q creates a new TwoQueueCache using the default +// values for the parameters. +func New2Q(size int) (*TwoQueueCache, error) { + return New2QParams(size, Default2QRecentRatio, Default2QGhostEntries) +} + +// New2QParams creates a new TwoQueueCache using the provided +// parameter values. +func New2QParams(size int, recentRatio float64, ghostRatio float64) (*TwoQueueCache, error) { + if size <= 0 { + return nil, fmt.Errorf("invalid size") + } + if recentRatio < 0.0 || recentRatio > 1.0 { + return nil, fmt.Errorf("invalid recent ratio") + } + if ghostRatio < 0.0 || ghostRatio > 1.0 { + return nil, fmt.Errorf("invalid ghost ratio") + } + + // Determine the sub-sizes + recentSize := int(float64(size) * recentRatio) + evictSize := int(float64(size) * ghostRatio) + + // Allocate the LRUs + recent, err := simplelru.NewLRU(size, nil) + if err != nil { + return nil, err + } + frequent, err := simplelru.NewLRU(size, nil) + if err != nil { + return nil, err + } + recentEvict, err := simplelru.NewLRU(evictSize, nil) + if err != nil { + return nil, err + } + + // Initialize the cache + c := &TwoQueueCache{ + size: size, + recentSize: recentSize, + recent: recent, + frequent: frequent, + recentEvict: recentEvict, + } + return c, nil +} + +// Get looks up a key's value from the cache. +func (c *TwoQueueCache) Get(key interface{}) (value interface{}, ok bool) { + c.lock.Lock() + defer c.lock.Unlock() + + // Check if this is a frequent value + if val, ok := c.frequent.Get(key); ok { + return val, ok + } + + // If the value is contained in recent, then we + // promote it to frequent + if val, ok := c.recent.Peek(key); ok { + c.recent.Remove(key) + c.frequent.Add(key, val) + return val, ok + } + + // No hit + return nil, false +} + +// Add adds a value to the cache. +func (c *TwoQueueCache) Add(key, value interface{}) { + c.lock.Lock() + defer c.lock.Unlock() + + // Check if the value is frequently used already, + // and just update the value + if c.frequent.Contains(key) { + c.frequent.Add(key, value) + return + } + + // Check if the value is recently used, and promote + // the value into the frequent list + if c.recent.Contains(key) { + c.recent.Remove(key) + c.frequent.Add(key, value) + return + } + + // If the value was recently evicted, add it to the + // frequently used list + if c.recentEvict.Contains(key) { + c.ensureSpace(true) + c.recentEvict.Remove(key) + c.frequent.Add(key, value) + return + } + + // Add to the recently seen list + c.ensureSpace(false) + c.recent.Add(key, value) + return +} + +// ensureSpace is used to ensure we have space in the cache +func (c *TwoQueueCache) ensureSpace(recentEvict bool) { + // If we have space, nothing to do + recentLen := c.recent.Len() + freqLen := c.frequent.Len() + if recentLen+freqLen < c.size { + return + } + + // If the recent buffer is larger than + // the target, evict from there + if recentLen > 0 && (recentLen > c.recentSize || (recentLen == c.recentSize && !recentEvict)) { + k, _, _ := c.recent.RemoveOldest() + c.recentEvict.Add(k, nil) + return + } + + // Remove from the frequent list otherwise + c.frequent.RemoveOldest() +} + +// Len returns the number of items in the cache. +func (c *TwoQueueCache) Len() int { + c.lock.RLock() + defer c.lock.RUnlock() + return c.recent.Len() + c.frequent.Len() +} + +// Keys returns a slice of the keys in the cache. +// The frequently used keys are first in the returned slice. +func (c *TwoQueueCache) Keys() []interface{} { + c.lock.RLock() + defer c.lock.RUnlock() + k1 := c.frequent.Keys() + k2 := c.recent.Keys() + return append(k1, k2...) +} + +// Remove removes the provided key from the cache. +func (c *TwoQueueCache) Remove(key interface{}) { + c.lock.Lock() + defer c.lock.Unlock() + if c.frequent.Remove(key) { + return + } + if c.recent.Remove(key) { + return + } + if c.recentEvict.Remove(key) { + return + } +} + +// Purge is used to completely clear the cache. +func (c *TwoQueueCache) Purge() { + c.lock.Lock() + defer c.lock.Unlock() + c.recent.Purge() + c.frequent.Purge() + c.recentEvict.Purge() +} + +// Contains is used to check if the cache contains a key +// without updating recency or frequency. +func (c *TwoQueueCache) Contains(key interface{}) bool { + c.lock.RLock() + defer c.lock.RUnlock() + return c.frequent.Contains(key) || c.recent.Contains(key) +} + +// Peek is used to inspect the cache value of a key +// without updating recency or frequency. +func (c *TwoQueueCache) Peek(key interface{}) (value interface{}, ok bool) { + c.lock.RLock() + defer c.lock.RUnlock() + if val, ok := c.frequent.Peek(key); ok { + return val, ok + } + return c.recent.Peek(key) +} -- cgit v1.2.3