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