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lru.go
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lru.go
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package rueidis
import (
"container/list"
"context"
"sync"
"sync/atomic"
"time"
"unsafe"
)
const (
entrySize = int(unsafe.Sizeof(entry{})) + int(unsafe.Sizeof(&entry{}))
keyCacheSize = int(unsafe.Sizeof(keyCache{})) + int(unsafe.Sizeof(&keyCache{}))
elementSize = int(unsafe.Sizeof(list.Element{})) + int(unsafe.Sizeof(&list.Element{}))
stringSSize = int(unsafe.Sizeof(""))
entryBaseSize = (keyCacheSize + entrySize + elementSize + stringSSize*2) * 3 / 2
entryMinSize = entryBaseSize + messageStructSize
moveThreshold = uint64(1024 - 1)
)
type cache interface {
GetOrPrepare(key, cmd string, now time.Time, ttl time.Duration) (v RedisMessage, entry *entry)
Update(key, cmd string, value RedisMessage, pttl int64)
Cancel(key, cmd string, err error)
Delete(keys []RedisMessage)
GetTTL(key string) time.Duration
FreeAndClose(err error)
}
type entry struct {
err error
ch chan struct{}
kc *keyCache
cmd string
val RedisMessage
size int
}
func (e *entry) Wait(ctx context.Context) (RedisMessage, error) {
if ch := ctx.Done(); ch == nil {
<-e.ch
} else {
select {
case <-ch:
return RedisMessage{}, ctx.Err()
case <-e.ch:
}
}
return e.val, e.err
}
type keyCache struct {
ttl time.Time
cache map[string]*list.Element
key string
hits uint64
miss uint64
}
var _ cache = (*lru)(nil)
type lru struct {
store map[string]*keyCache
list *list.List
mu sync.RWMutex
size int
max int
}
func newLRU(max int) *lru {
return &lru{
max: max,
store: make(map[string]*keyCache),
list: list.New(),
}
}
func (c *lru) GetOrPrepare(key, cmd string, now time.Time, ttl time.Duration) (v RedisMessage, e *entry) {
var ok bool
var kc *keyCache
var kcTTL time.Time
var ele, back *list.Element
c.mu.RLock()
if kc, ok = c.store[key]; ok {
kcTTL = kc.ttl
if ele, ok = kc.cache[cmd]; ok {
e = ele.Value.(*entry)
v = e.val
back = c.list.Back()
}
}
c.mu.RUnlock()
if e != nil && (v.typ == 0 || kcTTL.After(now)) {
hits := atomic.AddUint64(&kc.hits, 1)
if ele != back && hits&moveThreshold == 0 {
c.mu.Lock()
if c.list != nil {
c.list.MoveToBack(ele)
}
c.mu.Unlock()
}
return v, e
}
v = RedisMessage{}
e = nil
c.mu.Lock()
if kc, ok = c.store[key]; !ok {
if c.store == nil {
goto miss
}
kc = &keyCache{cache: make(map[string]*list.Element, 1), key: key, ttl: now.Add(ttl)}
c.store[key] = kc
}
if ele, ok = kc.cache[cmd]; ok {
if e = ele.Value.(*entry); e.val.typ == 0 || kc.ttl.After(now) {
atomic.AddUint64(&kc.hits, 1)
v = e.val
c.list.MoveToBack(ele)
} else {
c.list.Remove(ele)
c.size -= e.size
e = nil
}
}
if e == nil {
atomic.AddUint64(&kc.miss, 1)
c.list.PushBack(&entry{
cmd: cmd,
kc: kc,
ch: make(chan struct{}, 1),
})
kc.ttl = now.Add(ttl)
kc.cache[cmd] = c.list.Back()
}
miss:
c.mu.Unlock()
return v, e
}
func (c *lru) Update(key, cmd string, value RedisMessage, pttl int64) {
var ch chan struct{}
c.mu.Lock()
if kc, ok := c.store[key]; ok {
if pttl >= 0 {
// server side ttl should only shorten client side ttl
if ttl := time.Now().Add(time.Duration(pttl) * time.Millisecond); ttl.Before(kc.ttl) {
kc.ttl = ttl
}
}
if ele, ok := kc.cache[cmd]; ok {
if e := ele.Value.(*entry); e.val.typ == 0 {
e.val = value
e.val.setTTL(kc.ttl.Unix())
e.size = entryBaseSize + 2*(len(key)+len(cmd)) + value.approximateSize()
c.size += e.size
ch = e.ch
}
ele = c.list.Front()
for c.size > c.max && ele != nil {
if e := ele.Value.(*entry); e.val.typ != 0 { // do not delete pending entries
kc := e.kc
if delete(kc.cache, e.cmd); len(kc.cache) == 0 {
delete(c.store, kc.key)
}
c.list.Remove(ele)
c.size -= e.size
}
ele = ele.Next()
}
}
}
c.mu.Unlock()
if ch != nil {
close(ch)
}
}
func (c *lru) Cancel(key, cmd string, err error) {
var ch chan struct{}
c.mu.Lock()
if kc, ok := c.store[key]; ok {
if ele, ok := kc.cache[cmd]; ok {
if e := ele.Value.(*entry); e.val.typ == 0 {
e.err = err
ch = e.ch
if delete(kc.cache, cmd); len(kc.cache) == 0 {
delete(c.store, key)
}
c.list.Remove(ele)
}
}
}
c.mu.Unlock()
if ch != nil {
close(ch)
}
}
func (c *lru) GetTTL(key string) (ttl time.Duration) {
c.mu.Lock()
if kc, ok := c.store[key]; ok && len(kc.cache) != 0 {
ttl = kc.ttl.Sub(time.Now())
}
if ttl <= 0 {
ttl = -2
}
c.mu.Unlock()
return
}
func (c *lru) purge(key string, kc *keyCache) {
if kc != nil {
for cmd, ele := range kc.cache {
if e := ele.Value.(*entry); e.val.typ != 0 { // do not delete pending entries
if delete(kc.cache, cmd); len(kc.cache) == 0 {
delete(c.store, key)
}
c.list.Remove(ele)
c.size -= e.size
}
}
}
}
func (c *lru) Delete(keys []RedisMessage) {
c.mu.Lock()
if keys == nil {
for key, kc := range c.store {
c.purge(key, kc)
}
} else {
for _, k := range keys {
c.purge(k.string, c.store[k.string])
}
}
c.mu.Unlock()
}
func (c *lru) FreeAndClose(err error) {
c.mu.Lock()
for _, kc := range c.store {
for _, ele := range kc.cache {
if e := ele.Value.(*entry); e.val.typ == 0 {
e.err = err
close(e.ch)
}
}
}
c.store = nil
c.list = nil
c.mu.Unlock()
}