move cache2 package to cache (#14921)

Co-authored-by: Mattermod <mattermod@users.noreply.github.com>

services/cache/lru.go

@@ -0,0 +1,197 @@
+// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
+// See LICENSE.txt for license information.
+
+package cache
+
+import (
+	"container/list"
+	"sync"
+	"time"
+
+	"github.com/vmihailenco/msgpack/v5"
+)
+
+// LRU is a thread-safe fixed size LRU cache.
+type LRU struct {
+	name                   string
+	size                   int
+	evictList              *list.List
+	items                  map[string]*list.Element
+	lock                   sync.RWMutex
+	defaultExpiry          time.Duration
+	invalidateClusterEvent string
+	currentGeneration      int64
+	len                    int
+}
+
+// LRUOptions contains options for initializing LRU cache
+type LRUOptions struct {
+	Name                   string
+	Size                   int
+	DefaultExpiry          time.Duration
+	InvalidateClusterEvent string
+}
+
+// entry is used to hold a value in the evictList.
+type entry struct {
+	key        string
+	value      []byte
+	expires    time.Time
+	generation int64
+}
+
+// NewLRU creates an LRU of the given size.
+func NewLRU(opts *LRUOptions) Cache {
+	return &LRU{
+		name:                   opts.Name,
+		size:                   opts.Size,
+		evictList:              list.New(),
+		items:                  make(map[string]*list.Element, opts.Size),
+		defaultExpiry:          opts.DefaultExpiry,
+		invalidateClusterEvent: opts.InvalidateClusterEvent,
+	}
+}
+
+// Purge is used to completely clear the cache.
+func (l *LRU) Purge() error {
+	l.lock.Lock()
+	defer l.lock.Unlock()
+
+	l.len = 0
+	l.currentGeneration++
+	return nil
+}
+
+// Set adds the given key and value to the store without an expiry. If the key already exists,
+// it will overwrite the previous value.
+func (l *LRU) Set(key string, value interface{}) error {
+	return l.SetWithExpiry(key, value, 0)
+}
+
+// SetWithDefaultExpiry adds the given key and value to the store with the default expiry. If
+// the key already exists, it will overwrite the previoous value
+func (l *LRU) SetWithDefaultExpiry(key string, value interface{}) error {
+	return l.SetWithExpiry(key, value, l.defaultExpiry)
+}
+
+// SetWithExpiry adds the given key and value to the cache with the given expiry. If the key
+// already exists, it will overwrite the previoous value
+func (l *LRU) SetWithExpiry(key string, value interface{}, ttl time.Duration) error {
+	l.lock.Lock()
+	defer l.lock.Unlock()
+	return l.set(key, value, ttl)
+}
+
+// Get the content stored in the cache for the given key, and decode it into the value interface.
+// return ErrKeyNotFound if the key is missing from the cache
+func (l *LRU) Get(key string, value interface{}) error {
+	l.lock.Lock()
+	defer l.lock.Unlock()
+	return l.get(key, value)
+}
+
+// Remove deletes the value for a key.
+func (l *LRU) Remove(key string) error {
+	l.lock.Lock()
+	defer l.lock.Unlock()
+
+	if ent, ok := l.items[key]; ok {
+		l.removeElement(ent)
+	}
+	return nil
+}
+
+// Keys returns a slice of the keys in the cache.
+func (l *LRU) Keys() ([]string, error) {
+	l.lock.RLock()
+	defer l.lock.RUnlock()
+
+	keys := make([]string, l.len)
+	i := 0
+	for ent := l.evictList.Back(); ent != nil; ent = ent.Prev() {
+		e := ent.Value.(*entry)
+		if e.generation == l.currentGeneration {
+			keys[i] = e.key
+			i++
+		}
+	}
+	return keys, nil
+}
+
+// Len returns the number of items in the cache.
+func (l *LRU) Len() (int, error) {
+	l.lock.RLock()
+	defer l.lock.RUnlock()
+	return l.len, nil
+}
+
+// GetInvalidateClusterEvent returns the cluster event configured when this cache was created.
+func (l *LRU) GetInvalidateClusterEvent() string {
+	return l.invalidateClusterEvent
+}
+
+// Name returns the name of the cache
+func (l *LRU) Name() string {
+	return l.name
+}
+
+func (l *LRU) set(key string, value interface{}, ttl time.Duration) error {
+	var expires time.Time
+	if ttl > 0 {
+		expires = time.Now().Add(ttl)
+	}
+
+	buf, err := msgpack.Marshal(value)
+	if err != nil {
+		return err
+	}
+
+	// Check for existing item, ignoring expiry since we'd update anyway.
+	if ent, ok := l.items[key]; ok {
+		l.evictList.MoveToFront(ent)
+		e := ent.Value.(*entry)
+		e.value = buf
+		e.expires = expires
+		if e.generation != l.currentGeneration {
+			e.generation = l.currentGeneration
+			l.len++
+		}
+		return nil
+	}
+
+	// Add new item
+	ent := &entry{key, buf, expires, l.currentGeneration}
+	entry := l.evictList.PushFront(ent)
+	l.items[key] = entry
+	l.len++
+
+	if l.evictList.Len() > l.size {
+		l.removeElement(l.evictList.Back())
+	}
+	return nil
+}
+
+func (l *LRU) get(key string, value interface{}) error {
+	if ent, ok := l.items[key]; ok {
+		e := ent.Value.(*entry)
+
+		if e.generation != l.currentGeneration || (!e.expires.IsZero() && time.Now().After(e.expires)) {
+			l.removeElement(ent)
+			return ErrKeyNotFound
+		}
+
+		l.evictList.MoveToFront(ent)
+
+		return msgpack.Unmarshal(e.value, value)
+	}
+	return ErrKeyNotFound
+}
+
+func (l *LRU) removeElement(e *list.Element) {
+	l.evictList.Remove(e)
+	kv := e.Value.(*entry)
+	if kv.generation == l.currentGeneration {
+		l.len--
+	}
+	delete(l.items, kv.key)
+}