143 lignes
3 Kio
Go
143 lignes
3 Kio
Go
package native
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import (
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"container/list"
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"sync"
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"time"
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"github.com/NyaaPantsu/nyaa/common"
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"github.com/NyaaPantsu/nyaa/model"
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)
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const expiryTime = time.Minute
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// NativeCache implements cache.Cache
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type NativeCache struct {
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cache map[common.SearchParam]*list.Element
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ll *list.List
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totalUsed int
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mu sync.Mutex
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// Size sets the maximum size of the cache before evicting unread data in MB
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Size float64
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}
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// New Creates New Native Cache instance
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func New(sz float64) *NativeCache {
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return &NativeCache{
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cache: make(map[common.SearchParam]*list.Element, 10),
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Size: sz,
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ll: list.New(),
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}
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}
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// Key stores the ID of either a thread or board page
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type Key struct {
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LastN uint8
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Board string
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ID uint64
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}
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// Single cache entry
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type store struct {
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sync.Mutex // Controls general access to the contents of the struct
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lastFetched time.Time
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key common.SearchParam
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data []model.Torrent
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count, size int
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n *NativeCache
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}
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// Check the cache for and existing record. If miss, run fn to retrieve fresh
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// values.
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func (n *NativeCache) Get(key common.SearchParam, fn func() ([]model.Torrent, int, error)) (
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data []model.Torrent, count int, err error,
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) {
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s := n.getStore(key)
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// Also keeps multiple requesters from simultaneously requesting the same
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// data
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s.Lock()
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defer s.Unlock()
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if s.isFresh() {
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return s.data, s.count, nil
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}
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data, count, err = fn()
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if err != nil {
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return
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}
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s.update(data, count)
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return
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}
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// Retrieve a store from the cache or create a new one
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func (n *NativeCache) getStore(k common.SearchParam) (s *store) {
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n.mu.Lock()
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defer n.mu.Unlock()
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el := n.cache[k]
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if el == nil {
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s = &store{key: k, n: n}
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n.cache[k] = n.ll.PushFront(s)
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} else {
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n.ll.MoveToFront(el)
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s = el.Value.(*store)
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}
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return s
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}
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// Clear the cache. Only used for testing.
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func (n *NativeCache) ClearAll() {
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n.mu.Lock()
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defer n.mu.Unlock()
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n.ll = list.New()
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n.cache = make(map[common.SearchParam]*list.Element, 10)
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}
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// Update the total used memory counter and evict, if over limit
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func (n *NativeCache) updateUsedSize(delta int) {
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n.mu.Lock()
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defer n.mu.Unlock()
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n.totalUsed += delta
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for n.totalUsed > int(n.Size)<<20 {
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e := n.ll.Back()
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if e == nil {
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break
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}
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s := n.ll.Remove(e).(*store)
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delete(n.cache, s.key)
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s.Lock()
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n.totalUsed -= s.size
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s.Unlock()
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}
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}
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// Return, if the data can still be considered fresh, without querying the DB
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func (s *store) isFresh() bool {
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if s.lastFetched.IsZero() { // New store
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return false
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}
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return s.lastFetched.Add(expiryTime).After(time.Now())
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}
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// Stores the new values of s. Calculates and stores the new size. Passes the
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// delta to the central cache to fire eviction checks.
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func (s *store) update(data []model.Torrent, count int) {
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newSize := 0
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for _, d := range data {
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newSize += d.Size()
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}
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s.data = data
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s.count = count
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delta := newSize - s.size
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s.size = newSize
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s.lastFetched = time.Now()
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// In a separate goroutine, to ensure there is never any lock intersection
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go s.n.updateUsedSize(delta)
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}
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