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cache.go
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cache.go
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package collection
import (
"container/list"
"sync"
"sync/atomic"
"time"
"github.com/hduhelp/go-zero/core/logx"
"github.com/hduhelp/go-zero/core/mathx"
"github.com/hduhelp/go-zero/core/syncx"
)
const (
defaultCacheName = "proc"
slots = 300
statInterval = time.Minute
// make the expiry unstable to avoid lots of cached items expire at the same time
// make the unstable expiry to be [0.95, 1.05] * seconds
expiryDeviation = 0.05
)
var emptyLruCache = emptyLru{}
type (
// CacheOption defines the method to customize a Cache.
CacheOption func(cache *Cache)
// A Cache object is an in-memory cache.
Cache struct {
name string
lock sync.Mutex
data map[string]interface{}
expire time.Duration
timingWheel *TimingWheel
lruCache lru
barrier syncx.SingleFlight
unstableExpiry mathx.Unstable
stats *cacheStat
}
)
// NewCache returns a Cache with given expire.
func NewCache(expire time.Duration, opts ...CacheOption) (*Cache, error) {
cache := &Cache{
data: make(map[string]interface{}),
expire: expire,
lruCache: emptyLruCache,
barrier: syncx.NewSingleFlight(),
unstableExpiry: mathx.NewUnstable(expiryDeviation),
}
for _, opt := range opts {
opt(cache)
}
if len(cache.name) == 0 {
cache.name = defaultCacheName
}
cache.stats = newCacheStat(cache.name, cache.size)
timingWheel, err := NewTimingWheel(time.Second, slots, func(k, v interface{}) {
key, ok := k.(string)
if !ok {
return
}
cache.Del(key)
})
if err != nil {
return nil, err
}
cache.timingWheel = timingWheel
return cache, nil
}
// Del deletes the item with the given key from c.
func (c *Cache) Del(key string) {
c.lock.Lock()
delete(c.data, key)
c.lruCache.remove(key)
c.lock.Unlock()
c.timingWheel.RemoveTimer(key)
}
// Get returns the item with the given key from c.
func (c *Cache) Get(key string) (interface{}, bool) {
value, ok := c.doGet(key)
if ok {
c.stats.IncrementHit()
} else {
c.stats.IncrementMiss()
}
return value, ok
}
// Set sets value into c with key.
func (c *Cache) Set(key string, value interface{}) {
c.SetWithExpire(key, value, c.expire)
}
// SetWithExpire sets value into c with key and expire with the given value.
func (c *Cache) SetWithExpire(key string, value interface{}, expire time.Duration) {
c.lock.Lock()
_, ok := c.data[key]
c.data[key] = value
c.lruCache.add(key)
c.lock.Unlock()
expiry := c.unstableExpiry.AroundDuration(expire)
if ok {
c.timingWheel.MoveTimer(key, expiry)
} else {
c.timingWheel.SetTimer(key, value, expiry)
}
}
// Take returns the item with the given key.
// If the item is in c, return it directly.
// If not, use fetch method to get the item, set into c and return it.
func (c *Cache) Take(key string, fetch func() (interface{}, error)) (interface{}, error) {
if val, ok := c.doGet(key); ok {
c.stats.IncrementHit()
return val, nil
}
var fresh bool
val, err := c.barrier.Do(key, func() (interface{}, error) {
// because O(1) on map search in memory, and fetch is an IO query
// so we do double check, cache might be taken by another call
if val, ok := c.doGet(key); ok {
return val, nil
}
v, e := fetch()
if e != nil {
return nil, e
}
fresh = true
c.Set(key, v)
return v, nil
})
if err != nil {
return nil, err
}
if fresh {
c.stats.IncrementMiss()
return val, nil
}
// got the result from previous ongoing query
c.stats.IncrementHit()
return val, nil
}
func (c *Cache) doGet(key string) (interface{}, bool) {
c.lock.Lock()
defer c.lock.Unlock()
value, ok := c.data[key]
if ok {
c.lruCache.add(key)
}
return value, ok
}
func (c *Cache) onEvict(key string) {
// already locked
delete(c.data, key)
c.timingWheel.RemoveTimer(key)
}
func (c *Cache) size() int {
c.lock.Lock()
defer c.lock.Unlock()
return len(c.data)
}
// WithLimit customizes a Cache with items up to limit.
func WithLimit(limit int) CacheOption {
return func(cache *Cache) {
if limit > 0 {
cache.lruCache = newKeyLru(limit, cache.onEvict)
}
}
}
// WithName customizes a Cache with the given name.
func WithName(name string) CacheOption {
return func(cache *Cache) {
cache.name = name
}
}
type (
lru interface {
add(key string)
remove(key string)
}
emptyLru struct{}
keyLru struct {
limit int
evicts *list.List
elements map[string]*list.Element
onEvict func(key string)
}
)
func (elru emptyLru) add(string) {
}
func (elru emptyLru) remove(string) {
}
func newKeyLru(limit int, onEvict func(key string)) *keyLru {
return &keyLru{
limit: limit,
evicts: list.New(),
elements: make(map[string]*list.Element),
onEvict: onEvict,
}
}
func (klru *keyLru) add(key string) {
if elem, ok := klru.elements[key]; ok {
klru.evicts.MoveToFront(elem)
return
}
// Add new item
elem := klru.evicts.PushFront(key)
klru.elements[key] = elem
// Verify size not exceeded
if klru.evicts.Len() > klru.limit {
klru.removeOldest()
}
}
func (klru *keyLru) remove(key string) {
if elem, ok := klru.elements[key]; ok {
klru.removeElement(elem)
}
}
func (klru *keyLru) removeOldest() {
elem := klru.evicts.Back()
if elem != nil {
klru.removeElement(elem)
}
}
func (klru *keyLru) removeElement(e *list.Element) {
klru.evicts.Remove(e)
key := e.Value.(string)
delete(klru.elements, key)
klru.onEvict(key)
}
type cacheStat struct {
name string
hit uint64
miss uint64
sizeCallback func() int
}
func newCacheStat(name string, sizeCallback func() int) *cacheStat {
st := &cacheStat{
name: name,
sizeCallback: sizeCallback,
}
go st.statLoop()
return st
}
func (cs *cacheStat) IncrementHit() {
atomic.AddUint64(&cs.hit, 1)
}
func (cs *cacheStat) IncrementMiss() {
atomic.AddUint64(&cs.miss, 1)
}
func (cs *cacheStat) statLoop() {
ticker := time.NewTicker(statInterval)
defer ticker.Stop()
for range ticker.C {
hit := atomic.SwapUint64(&cs.hit, 0)
miss := atomic.SwapUint64(&cs.miss, 0)
total := hit + miss
if total == 0 {
continue
}
percent := 100 * float32(hit) / float32(total)
logx.Statf("cache(%s) - qpm: %d, hit_ratio: %.1f%%, elements: %d, hit: %d, miss: %d",
cs.name, total, percent, cs.sizeCallback(), hit, miss)
}
}