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minio/pkg/storage/drivers/memory/memory_intelligent.go

155 lines
3.7 KiB

/*
* 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{}
// updatedAt holds the time that related item's updated at
updatedAt 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{}{},
updatedAt: 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) {
r.Lock()
for key := range r.items {
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]
if !ok {
return nil, false
}
r.updatedAt[key] = time.Now()
return value, true
}
// 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.updatedAt[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.updatedAt, key)
r.totalEvicted++
if r.OnEvicted != nil {
r.OnEvicted(key)
}
}
func (r *Intelligent) isValid(key string) bool {
updatedAt, ok := r.updatedAt[key]
if !ok {
return false
}
if r.expiration == zeroExpiration {
return true
}
return updatedAt.Add(r.expiration).After(time.Now())
}