128 lines
2.9 KiB
Go
128 lines
2.9 KiB
Go
package cache
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import (
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"log"
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"strings"
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"time"
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"github.com/hashicorp/golang-lru"
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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 *lru.Cache
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postFlushFn func()
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maxKeys int
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maxValueSize int
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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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postFlushFn: func() {},
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maxKeys: 1000,
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maxValueSize: 0,
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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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// OnEvicted called automatically for expired and manually deleted
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res.bytesCache, _ = lru.New(res.maxKeys)
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log.Printf("[DEBUG] create lru cache, maxKeys=%d, maxValueSize=%d", 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.Add(key, data)
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}
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return data, nil
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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.Purge()
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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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for _, k := range lc.bytesCache.Keys() {
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key := k.(string)
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if inScope(key) {
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matchedKeys = append(matchedKeys, key)
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}
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}
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for _, mkey := range matchedKeys {
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lc.bytesCache.Remove(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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return true
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}
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