154 lines
3.7 KiB
Go
154 lines
3.7 KiB
Go
package cache
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import (
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"log"
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"strings"
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"sync"
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"time"
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"github.com/patrickmn/go-cache"
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"github.com/pkg/errors"
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)
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// LoadingCache defines interface for caching
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type LoadingCache interface {
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Get(key string, ttl time.Duration, fn func() ([]byte, error)) (data []byte, err error)
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Flush(scopes ...string)
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}
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// Key makes full key from primary key and scopes
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func Key(key string, scopes ...string) string {
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return strings.Join(scopes, "$$") + "@@" + key
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}
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func parseKey(fullKey string) (key string, scopes []string, err error) {
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elems := strings.Split(fullKey, "@@")
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if len(elems) != 2 {
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return "", nil, errors.Errorf("can't parse cache key %s", key)
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}
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scopes = strings.Split(elems[0], "$$")
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if len(scopes) == 1 && scopes[0] == "" {
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scopes = []string{}
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}
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key = elems[1]
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return key, scopes, nil
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}
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// loadingCache implements LoadingCache interface on top of cache.Cache (go-cache)
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type loadingCache struct {
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bytesCache *cache.Cache
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postFlushFn func()
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defaultExpiration time.Duration
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cleanupInterval time.Duration
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maxKeys int
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maxValueSize int
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activeKeys map[string]struct{} // keep all current cached keys
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lock sync.Mutex
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}
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// NewLoadingCache makes loadingCache implementation
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func NewLoadingCache(options ...Option) LoadingCache {
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res := loadingCache{
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defaultExpiration: time.Hour,
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cleanupInterval: 5 * time.Minute,
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postFlushFn: func() {},
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maxKeys: 0,
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maxValueSize: 0,
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activeKeys: map[string]struct{}{},
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}
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for _, opt := range options {
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if err := opt(&res); err != nil {
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log.Printf("[WARN] failed to set cache option, %v", err)
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}
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}
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res.bytesCache = cache.New(res.defaultExpiration, res.cleanupInterval)
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// OnEvicted called automatically for expired and manually deleted
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res.bytesCache.OnEvicted(func(key string, _ interface{}) {
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res.withLock(func() { delete(res.activeKeys, key) })
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})
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log.Printf("[DEBUG] create cache with cleanupInterval=%s, maxKeys=%d, maxValueSize=%d",
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res.cleanupInterval, res.maxKeys, res.maxValueSize)
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return &res
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}
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// Get is loading cache method to get value by key or load via fn if not found
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func (lc *loadingCache) Get(key string, ttl time.Duration, fn func() ([]byte, error)) (data []byte, err error) {
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if b, ok := lc.bytesCache.Get(key); ok {
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return b.([]byte), nil
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}
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if data, err = fn(); err != nil {
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return data, err
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}
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if lc.allowed(data) {
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lc.bytesCache.Set(key, data, ttl)
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lc.withLock(func() { lc.activeKeys[key] = struct{}{} })
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}
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return data, nil
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}
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func (lc *loadingCache) withLock(fn func()) {
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lc.lock.Lock()
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fn()
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lc.lock.Unlock()
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}
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// Flush clears cache and calls postFlushFn async
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func (lc *loadingCache) Flush(scopes ...string) {
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if len(scopes) == 0 {
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lc.bytesCache.Flush()
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lc.withLock(func() { lc.activeKeys = map[string]struct{}{} })
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go lc.postFlushFn()
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return
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}
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// check if fullKey has matching scopes
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inScope := func(fullKey string) bool {
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for _, s := range scopes {
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_, keyScopes, err := parseKey(fullKey)
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if err != nil {
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return false
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}
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for _, ks := range keyScopes {
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if ks == s {
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return true
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}
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}
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}
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return false
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}
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// all matchedKeys should be collected first
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// we can't delete it from locked section, it will lock on eviction callback
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matchedKeys := []string{}
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lc.withLock(func() {
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for k := range lc.activeKeys {
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if inScope(k) {
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matchedKeys = append(matchedKeys, k)
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}
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}
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})
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for _, mkey := range matchedKeys {
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lc.bytesCache.Delete(mkey)
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}
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if lc.postFlushFn != nil {
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go lc.postFlushFn()
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}
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}
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func (lc *loadingCache) allowed(data []byte) bool {
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if lc.maxValueSize > 0 && len(data) >= lc.maxValueSize {
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return false
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}
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if lc.maxKeys > 0 && lc.bytesCache.ItemCount() >= lc.maxKeys {
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return false
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}
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return true
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}
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