Deprecate LRU use just map[string]interface{} and call it intelligent 'cache'

pkg/storage/drivers/memory/memory_intelligent.go

@@ -0,0 +1,151 @@
+/*
+ * Minimalist Object Storage, (C) 2015 Minio, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package memory
+
+import (
+	"sync"
+	"time"
+)
+
+var zeroExpiration = time.Duration(0)
+
+// Intelligent holds the required variables to compose an in memory cache system
+// which also provides expiring key mechanism and also maxSize
+type Intelligent struct {
+	// Mutex is used for handling the concurrent
+	// read/write requests for cache
+	sync.Mutex
+
+	// items hold the cached objects
+	items map[string]interface{}
+
+	// createdAt holds the time that related item's created At
+	createdAt map[string]time.Time
+
+	// expiration is a duration for a cache key to expire
+	expiration time.Duration
+
+	// gcInterval is a duration for garbage collection
+	gcInterval time.Duration
+
+	// maxSize is a total size for overall cache
+	maxSize uint64
+
+	// currentSize is a current size in memory
+	currentSize uint64
+
+	// OnEvicted - callback function for eviction
+	OnEvicted func(a ...interface{})
+
+	// totalEvicted counter to keep track of total evictions
+	totalEvicted uint64
+}
+
+// Stats current cache statistics
+type Stats struct {
+	Bytes     uint64
+	Items     uint64
+	Evictions uint64
+}
+
+// NewIntelligent creates an inmemory cache
+//
+// maxSize is used for expiring objects before we run out of memory
+// expiration is used for expiration of a key from cache
+func NewIntelligent(maxSize uint64, expiration time.Duration) *Intelligent {
+	return &Intelligent{
+		items:      map[string]interface{}{},
+		createdAt:  map[string]time.Time{},
+		expiration: expiration,
+		maxSize:    maxSize,
+	}
+}
+
+// Stats get current cache statistics
+func (r *Intelligent) Stats() Stats {
+	return Stats{
+		Bytes:     r.currentSize,
+		Items:     uint64(len(r.items)),
+		Evictions: r.totalEvicted,
+	}
+}
+
+// ExpireObjects expire objects in go routine
+func (r *Intelligent) ExpireObjects(gcInterval time.Duration) {
+	r.gcInterval = gcInterval
+	go func() {
+		for range time.Tick(gcInterval) {
+			for key := range r.items {
+				r.Lock()
+				if !r.isValid(key) {
+					r.Delete(key)
+				}
+				r.Unlock()
+			}
+		}
+	}()
+}
+
+// Get returns a value of a given key if it exists
+func (r *Intelligent) Get(key string) (interface{}, bool) {
+	r.Lock()
+	defer r.Unlock()
+	value, ok := r.items[key]
+	return value, ok
+}
+
+// Set will persist a value to the cache
+func (r *Intelligent) Set(key string, value interface{}) {
+	r.Lock()
+	// remove random key if only we reach the maxSize threshold,
+	// if not assume infinite memory
+	if r.maxSize > 0 {
+		for key := range r.items {
+			for (r.currentSize + uint64(len(value.([]byte)))) > r.maxSize {
+				r.Delete(key)
+			}
+			break
+		}
+	}
+	r.items[key] = value
+	r.currentSize += uint64(len(value.([]byte)))
+	r.createdAt[key] = time.Now()
+	r.Unlock()
+	return
+}
+
+// Delete deletes a given key if exists
+func (r *Intelligent) Delete(key string) {
+	r.currentSize -= uint64(len(r.items[key].([]byte)))
+	delete(r.items, key)
+	delete(r.createdAt, key)
+	r.totalEvicted++
+	if r.OnEvicted != nil {
+		r.OnEvicted(key)
+	}
+}
+
+func (r *Intelligent) isValid(key string) bool {
+	createdAt, ok := r.createdAt[key]
+	if !ok {
+		return false
+	}
+	if r.expiration == zeroExpiration {
+		return true
+	}
+	return createdAt.Add(r.expiration).After(time.Now())
+}