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transcache.go
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transcache.go
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/*
TransCache is released under the MIT License <http://www.opensource.org/licenses/mit-license.php
Copyright (C) ITsysCOM GmbH. All Rights Reserved.
TransCache is a bigger version of Cache with support for multiple Cache instances and transactions
*/
package ltcache
import (
"crypto/rand"
"errors"
"fmt"
"io"
"reflect"
"sync"
"time"
)
const (
AddItem = "AddItem"
RemoveItem = "RemoveItem"
RemoveGroup = "RemoveGroup"
DefaultCacheInstance = "*default"
)
var (
ErrNotFound = errors.New("not found")
ErrNotClonable = errors.New("not clonable")
)
func GenUUID() string {
b := make([]byte, 16)
io.ReadFull(rand.Reader, b)
b[6] = (b[6] & 0x0F) | 0x40
b[8] = (b[8] &^ 0x40) | 0x80
return fmt.Sprintf("%x-%x-%x-%x-%x", b[:4], b[4:6], b[6:8], b[8:10],
b[10:])
}
// Cloner is an interface for objects to clone themselves into interface
type Cloner interface {
Clone() (interface{}, error)
}
type transactionItem struct {
verb string // action which will be executed on cache
cacheID string // cache instance identifier
itemID string // item itentifier
value interface{} // item value
groupIDs []string // attach item to groups
}
type CacheConfig struct {
MaxItems int
TTL time.Duration
StaticTTL bool
OnEvicted func(itmID string, value interface{})
}
// NewTransCache instantiates a new TransCache
func NewTransCache(cfg map[string]*CacheConfig) (tc *TransCache) {
if _, has := cfg[DefaultCacheInstance]; !has { // Default always created
cfg[DefaultCacheInstance] = &CacheConfig{MaxItems: -1}
}
tc = &TransCache{
cache: make(map[string]*Cache),
cfg: cfg,
transactionBuffer: make(map[string][]*transactionItem),
}
for cacheID, chCfg := range cfg {
tc.cache[cacheID] = NewCache(chCfg.MaxItems, chCfg.TTL, chCfg.StaticTTL, chCfg.OnEvicted)
}
return
}
// TransCache is a bigger cache with transactions and multiple Cache instances support
type TransCache struct {
cache map[string]*Cache // map[cacheInstance]cacheStore
cfg map[string]*CacheConfig // map[cacheInstance]*CacheConfig
cacheMux sync.RWMutex // so we can apply the complete transaction buffer in one shoot
transactionBuffer map[string][]*transactionItem // Queue tasks based on transactionID
transBufMux sync.Mutex // Protects the transactionBuffer
transactionMux sync.Mutex // Queue transactions on commit
}
// cacheInstance returns a specific cache instance based on ID or default
func (tc *TransCache) cacheInstance(chID string) (c *Cache) {
var ok bool
if c, ok = tc.cache[chID]; !ok {
c = tc.cache[DefaultCacheInstance]
}
return
}
// BeginTransaction initializes a new transaction into transactions buffer
func (tc *TransCache) BeginTransaction() (transID string) {
transID = GenUUID()
tc.transBufMux.Lock()
tc.transactionBuffer[transID] = make([]*transactionItem, 0)
tc.transBufMux.Unlock()
return transID
}
// RollbackTransaction destroys a transaction from transactions buffer
func (tc *TransCache) RollbackTransaction(transID string) {
tc.transBufMux.Lock()
delete(tc.transactionBuffer, transID)
tc.transBufMux.Unlock()
}
// CommitTransaction executes the actions in a transaction buffer
func (tc *TransCache) CommitTransaction(transID string) {
tc.transactionMux.Lock()
tc.transBufMux.Lock()
tc.cacheMux.Lock() // apply all transactioned items in one shot
for _, item := range tc.transactionBuffer[transID] {
switch item.verb {
case AddItem:
tc.Set(item.cacheID, item.itemID, item.value, item.groupIDs, true, transID)
case RemoveItem:
tc.Remove(item.cacheID, item.itemID, true, transID)
case RemoveGroup:
if len(item.groupIDs) >= 1 {
tc.RemoveGroup(item.cacheID, item.groupIDs[0], true, transID)
}
}
}
tc.cacheMux.Unlock()
delete(tc.transactionBuffer, transID)
tc.transBufMux.Unlock()
tc.transactionMux.Unlock()
}
//Get returns the value of an Item
func (tc *TransCache) Get(chID, itmID string) (interface{}, bool) {
tc.cacheMux.RLock()
defer tc.cacheMux.RUnlock()
return tc.cacheInstance(chID).Get(itmID)
}
// Set will add/edit an item to the cache
func (tc *TransCache) Set(chID, itmID string, value interface{},
groupIDs []string, commit bool, transID string) {
if commit {
if transID == "" { // Lock locally
tc.cacheMux.Lock()
defer tc.cacheMux.Unlock()
}
tc.cacheInstance(chID).Set(itmID, value, groupIDs)
} else {
tc.transBufMux.Lock()
tc.transactionBuffer[transID] = append(tc.transactionBuffer[transID],
&transactionItem{cacheID: chID,
verb: AddItem, itemID: itmID,
value: value, groupIDs: groupIDs})
tc.transBufMux.Unlock()
}
}
// RempveItem removes an item from the cache
func (tc *TransCache) Remove(chID, itmID string, commit bool, transID string) {
if commit {
if transID == "" { // Lock per operation not transaction
tc.cacheMux.Lock()
defer tc.cacheMux.Unlock()
}
tc.cacheInstance(chID).Remove(itmID)
} else {
tc.transBufMux.Lock()
tc.transactionBuffer[transID] = append(tc.transactionBuffer[transID],
&transactionItem{cacheID: chID, verb: RemoveItem, itemID: itmID})
tc.transBufMux.Unlock()
}
}
func (tc *TransCache) HasGroup(chID, grpID string) (has bool) {
tc.cacheMux.RLock()
has = tc.cacheInstance(chID).HasGroup(grpID)
tc.cacheMux.RUnlock()
return
}
// GetGroupItems returns all items in a group. Nil if group does not exist
func (tc *TransCache) GetGroupItemIDs(chID, grpID string) (itmIDs []string) {
tc.cacheMux.RLock()
itmIDs = tc.cacheInstance(chID).GetGroupItemIDs(grpID)
tc.cacheMux.RUnlock()
return
}
// GetGroupItems returns all items in a group. Nil if group does not exist
func (tc *TransCache) GetGroupItems(chID, grpID string) (itms []interface{}) {
tc.cacheMux.RLock()
itms = tc.cacheInstance(chID).GetGroupItems(grpID)
tc.cacheMux.RUnlock()
return
}
// RemoveGroup removes a group of items out of cache
func (tc *TransCache) RemoveGroup(chID, grpID string, commit bool, transID string) {
if commit {
if transID == "" { // Lock locally
tc.cacheMux.Lock()
defer tc.cacheMux.Unlock()
}
tc.cacheInstance(chID).RemoveGroup(grpID)
} else {
tc.transBufMux.Lock()
tc.transactionBuffer[transID] = append(tc.transactionBuffer[transID],
&transactionItem{cacheID: chID, verb: RemoveGroup, groupIDs: []string{grpID}})
tc.transBufMux.Unlock()
}
}
// Remove all items in one or more cache instances
func (tc *TransCache) Clear(chIDs []string) {
tc.cacheMux.Lock()
if chIDs == nil {
chIDs = make([]string, len(tc.cache))
i := 0
for chID := range tc.cache {
chIDs[i] = chID
i += 1
}
}
for _, chID := range chIDs {
tc.cacheInstance(chID).Clear()
}
tc.cacheMux.Unlock()
}
// GetCloned returns a clone of an Item if Item is clonable
func (tc *TransCache) GetCloned(chID, itmID string) (cln interface{}, err error) {
tc.cacheMux.RLock()
origVal, hasIt := tc.cacheInstance(chID).Get(itmID)
tc.cacheMux.RUnlock()
if !hasIt {
return nil, ErrNotFound
}
if origVal == nil {
return
}
if _, canClone := origVal.(Cloner); !canClone {
return nil, ErrNotClonable
}
retVals := reflect.ValueOf(origVal).MethodByName("Clone").Call(nil) // Call Clone method on the object
errIf := retVals[1].Interface()
var notNil bool
if err, notNil = errIf.(error); notNil {
return
}
return retVals[0].Interface(), nil
}
// GetItemIDs returns a list of item IDs matching prefix
func (tc *TransCache) GetItemIDs(chID, prfx string) (itmIDs []string) {
tc.cacheMux.RLock()
itmIDs = tc.cacheInstance(chID).GetItemIDs(prfx)
tc.cacheMux.RUnlock()
return
}
// GetItemExpiryTime returns the expiry time of an item, ok is false if not found
func (tc *TransCache) GetItemExpiryTime(chID, itmID string) (exp time.Time, ok bool) {
tc.cacheMux.RLock()
defer tc.cacheMux.RUnlock()
return tc.cacheInstance(chID).GetItemExpiryTime(itmID)
}
// HasItem verifies if Item is in the cache
func (tc *TransCache) HasItem(chID, itmID string) (has bool) {
tc.cacheMux.RLock()
has = tc.cacheInstance(chID).HasItem(itmID)
tc.cacheMux.RUnlock()
return
}
// GetCacheStats returns on overview of full cache
func (tc *TransCache) GetCacheStats(chIDs []string) (cs map[string]*CacheStats) {
cs = make(map[string]*CacheStats)
tc.cacheMux.RLock()
if len(chIDs) == 0 {
for chID := range tc.cache {
chIDs = append(chIDs, chID)
}
}
for _, chID := range chIDs {
cs[chID] = tc.cacheInstance(chID).GetCacheStats()
}
tc.cacheMux.RUnlock()
return
}