mirror of
https://github.com/VictoriaMetrics/VictoriaMetrics.git
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48dda17e36
While at it, decrease -prevCacheRemovalPercent from 0.2 to 0.1 and increase -cacheExpireDuration from 20 minutes to 30 minutes. This is needed for https://github.com/VictoriaMetrics/VictoriaMetrics/issues/3343
459 lines
12 KiB
Go
459 lines
12 KiB
Go
package workingsetcache
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import (
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"flag"
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"sync"
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"sync/atomic"
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"time"
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"github.com/VictoriaMetrics/VictoriaMetrics/lib/bytesutil"
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"github.com/VictoriaMetrics/VictoriaMetrics/lib/cgroup"
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"github.com/VictoriaMetrics/fastcache"
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)
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var (
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prevCacheRemovalPercent = flag.Float64("prevCacheRemovalPercent", 0.1, "Items in the previous caches are removed when the percent of requests it serves "+
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"becomes lower than this value. Higher values reduce memory usage at the cost of higher CPU usage. See also -cacheExpireDuration")
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cacheExpireDuration = flag.Duration("cacheExpireDuration", 30*time.Minute, "Items are removed from in-memory caches after they aren't accessed for this duration. "+
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"Lower values may reduce memory usage at the cost of higher CPU usage. See also -prevCacheRemovalPercent")
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)
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// Cache modes.
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const (
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split = 0
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switching = 1
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whole = 2
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)
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// Cache is a cache for working set entries.
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//
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// The cache evicts inactive entries after the given expireDuration.
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// Recently accessed entries survive expireDuration.
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type Cache struct {
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curr atomic.Value
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prev atomic.Value
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// csHistory holds cache stats history
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csHistory fastcache.Stats
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// mode indicates whether to use only curr and skip prev.
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//
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// This flag is set to switching if curr is filled for more than 50% space.
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// In this case using prev would result in RAM waste,
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// it is better to use only curr cache with doubled size.
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// After the process of switching, this flag will be set to whole.
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mode uint32
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// The maxBytes value passed to New() or to Load().
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maxBytes int
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// mu serializes access to curr, prev and mode
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// in expirationWatcher, prevCacheWatcher and cacheSizeWatcher.
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mu sync.Mutex
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wg sync.WaitGroup
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stopCh chan struct{}
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}
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// Load loads the cache from filePath and limits its size to maxBytes
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// and evicts inactive entries in 20 minutes.
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//
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// Stop must be called on the returned cache when it is no longer needed.
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func Load(filePath string, maxBytes int) *Cache {
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return loadWithExpire(filePath, maxBytes, *cacheExpireDuration)
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}
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func loadWithExpire(filePath string, maxBytes int, expireDuration time.Duration) *Cache {
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curr := fastcache.LoadFromFileOrNew(filePath, maxBytes)
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var cs fastcache.Stats
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curr.UpdateStats(&cs)
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if cs.EntriesCount == 0 {
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curr.Reset()
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// The cache couldn't be loaded with maxBytes size.
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// This may mean that the cache is split into curr and prev caches.
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// Try loading it again with maxBytes / 2 size.
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// Put the loaded cache into `prev` instead of `curr`
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// in order to limit the growth of the cache for the current period of time.
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prev := fastcache.LoadFromFileOrNew(filePath, maxBytes/2)
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curr := fastcache.New(maxBytes / 2)
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c := newCacheInternal(curr, prev, split, maxBytes)
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c.runWatchers(expireDuration)
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return c
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}
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// The cache has been successfully loaded in full.
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// Set its' mode to `whole`.
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// There is no need in runWatchers call.
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prev := fastcache.New(1024)
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return newCacheInternal(curr, prev, whole, maxBytes)
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}
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// New creates new cache with the given maxBytes capacity.
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//
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// Stop must be called on the returned cache when it is no longer needed.
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func New(maxBytes int) *Cache {
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return newWithExpire(maxBytes, *cacheExpireDuration)
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}
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func newWithExpire(maxBytes int, expireDuration time.Duration) *Cache {
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curr := fastcache.New(maxBytes / 2)
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prev := fastcache.New(1024)
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c := newCacheInternal(curr, prev, split, maxBytes)
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c.runWatchers(expireDuration)
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return c
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}
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func newCacheInternal(curr, prev *fastcache.Cache, mode, maxBytes int) *Cache {
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var c Cache
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c.maxBytes = maxBytes
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c.curr.Store(curr)
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c.prev.Store(prev)
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c.stopCh = make(chan struct{})
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c.setMode(mode)
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return &c
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}
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func (c *Cache) runWatchers(expireDuration time.Duration) {
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c.wg.Add(1)
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go func() {
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defer c.wg.Done()
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c.expirationWatcher(expireDuration)
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}()
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c.wg.Add(1)
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go func() {
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defer c.wg.Done()
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c.prevCacheWatcher()
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}()
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c.wg.Add(1)
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go func() {
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defer c.wg.Done()
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c.cacheSizeWatcher()
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}()
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}
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func (c *Cache) expirationWatcher(expireDuration time.Duration) {
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expireDuration += timeJitter(expireDuration / 10)
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t := time.NewTicker(expireDuration)
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defer t.Stop()
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for {
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select {
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case <-c.stopCh:
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return
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case <-t.C:
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}
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c.mu.Lock()
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if atomic.LoadUint32(&c.mode) != split {
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// Stop the expirationWatcher on non-split mode.
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c.mu.Unlock()
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return
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}
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// Reset prev cache and swap it with the curr cache.
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prev := c.prev.Load().(*fastcache.Cache)
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curr := c.curr.Load().(*fastcache.Cache)
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c.prev.Store(curr)
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var cs fastcache.Stats
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prev.UpdateStats(&cs)
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updateCacheStatsHistory(&c.csHistory, &cs)
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prev.Reset()
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c.curr.Store(prev)
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c.mu.Unlock()
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}
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}
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func (c *Cache) prevCacheWatcher() {
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p := *prevCacheRemovalPercent / 100
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if p <= 0 {
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// There is no need in removing the previous cache.
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return
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}
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minCurrRequests := uint64(1 / p)
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// Watch for the usage of the prev cache and drop it whenever it receives
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// less than prevCacheRemovalPercent requests comparing to the curr cache during the last 60 seconds.
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checkInterval := 60 * time.Second
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checkInterval += timeJitter(checkInterval / 10)
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t := time.NewTicker(checkInterval)
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defer t.Stop()
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prevGetCalls := uint64(0)
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currGetCalls := uint64(0)
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for {
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select {
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case <-c.stopCh:
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return
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case <-t.C:
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}
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c.mu.Lock()
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if atomic.LoadUint32(&c.mode) != split {
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// Do nothing in non-split mode.
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c.mu.Unlock()
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return
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}
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prev := c.prev.Load().(*fastcache.Cache)
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curr := c.curr.Load().(*fastcache.Cache)
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var csCurr, csPrev fastcache.Stats
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curr.UpdateStats(&csCurr)
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prev.UpdateStats(&csPrev)
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currRequests := csCurr.GetCalls
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if currRequests >= currGetCalls {
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currRequests -= currGetCalls
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}
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prevRequests := csPrev.GetCalls
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if prevRequests >= prevGetCalls {
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prevRequests -= prevGetCalls
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}
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currGetCalls = csCurr.GetCalls
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prevGetCalls = csPrev.GetCalls
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if currRequests >= minCurrRequests && float64(prevRequests)/float64(currRequests) < p {
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// The majority of requests are served from the curr cache,
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// so the prev cache can be deleted in order to free up memory.
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if csPrev.EntriesCount > 0 {
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updateCacheStatsHistory(&c.csHistory, &csPrev)
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prev.Reset()
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}
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}
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c.mu.Unlock()
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}
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}
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func (c *Cache) cacheSizeWatcher() {
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checkInterval := 1500 * time.Millisecond
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checkInterval += timeJitter(checkInterval / 10)
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t := time.NewTicker(checkInterval)
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defer t.Stop()
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var maxBytesSize uint64
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for {
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select {
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case <-c.stopCh:
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return
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case <-t.C:
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}
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if c.loadMode() != split {
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continue
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}
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var cs fastcache.Stats
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curr := c.curr.Load().(*fastcache.Cache)
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curr.UpdateStats(&cs)
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if cs.BytesSize >= uint64(0.9*float64(cs.MaxBytesSize)) {
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maxBytesSize = cs.MaxBytesSize
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break
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}
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}
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// curr cache size exceeds 90% of its capacity. It is better
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// to double the size of curr cache and stop using prev cache,
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// since this will result in higher summary cache capacity.
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//
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// Do this in the following steps:
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// 1) switch to mode=switching
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// 2) move curr cache to prev
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// 3) create curr cache with doubled size
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// 4) wait until curr cache size exceeds maxBytesSize, i.e. it is populated with new data
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// 5) switch to mode=whole
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// 6) drop prev cache
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c.mu.Lock()
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c.setMode(switching)
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prev := c.prev.Load().(*fastcache.Cache)
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curr := c.curr.Load().(*fastcache.Cache)
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c.prev.Store(curr)
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var cs fastcache.Stats
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prev.UpdateStats(&cs)
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updateCacheStatsHistory(&c.csHistory, &cs)
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prev.Reset()
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// use c.maxBytes instead of maxBytesSize*2 for creating new cache, since otherwise the created cache
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// couldn't be loaded from file with c.maxBytes limit after saving with maxBytesSize*2 limit.
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c.curr.Store(fastcache.New(c.maxBytes))
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c.mu.Unlock()
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for {
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select {
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case <-c.stopCh:
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return
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case <-t.C:
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}
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var cs fastcache.Stats
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curr := c.curr.Load().(*fastcache.Cache)
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curr.UpdateStats(&cs)
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if cs.BytesSize >= maxBytesSize {
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break
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}
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}
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c.mu.Lock()
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c.setMode(whole)
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prev = c.prev.Load().(*fastcache.Cache)
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c.prev.Store(fastcache.New(1024))
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cs.Reset()
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prev.UpdateStats(&cs)
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updateCacheStatsHistory(&c.csHistory, &cs)
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prev.Reset()
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c.mu.Unlock()
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}
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// Save saves the cache to filePath.
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func (c *Cache) Save(filePath string) error {
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curr := c.curr.Load().(*fastcache.Cache)
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concurrency := cgroup.AvailableCPUs()
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return curr.SaveToFileConcurrent(filePath, concurrency)
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}
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// Stop stops the cache.
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//
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// The cache cannot be used after the Stop call.
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func (c *Cache) Stop() {
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close(c.stopCh)
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c.wg.Wait()
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c.Reset()
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}
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// Reset resets the cache.
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func (c *Cache) Reset() {
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var cs fastcache.Stats
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prev := c.prev.Load().(*fastcache.Cache)
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prev.UpdateStats(&cs)
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prev.Reset()
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curr := c.curr.Load().(*fastcache.Cache)
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curr.UpdateStats(&cs)
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updateCacheStatsHistory(&c.csHistory, &cs)
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curr.Reset()
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// Reset the mode to `split` in the hope the working set size becomes smaller after the reset.
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c.setMode(split)
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}
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func (c *Cache) setMode(mode int) {
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atomic.StoreUint32(&c.mode, uint32(mode))
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}
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func (c *Cache) loadMode() int {
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return int(atomic.LoadUint32(&c.mode))
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}
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// UpdateStats updates fcs with cache stats.
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func (c *Cache) UpdateStats(fcs *fastcache.Stats) {
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updateCacheStatsHistory(fcs, &c.csHistory)
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var cs fastcache.Stats
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curr := c.curr.Load().(*fastcache.Cache)
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curr.UpdateStats(&cs)
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updateCacheStats(fcs, &cs)
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prev := c.prev.Load().(*fastcache.Cache)
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cs.Reset()
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prev.UpdateStats(&cs)
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updateCacheStats(fcs, &cs)
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}
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func updateCacheStats(dst, src *fastcache.Stats) {
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dst.GetCalls += src.GetCalls
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dst.SetCalls += src.SetCalls
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dst.Misses += src.Misses
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dst.Collisions += src.Collisions
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dst.Corruptions += src.Corruptions
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dst.EntriesCount += src.EntriesCount
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dst.BytesSize += src.BytesSize
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dst.MaxBytesSize += src.MaxBytesSize
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}
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func updateCacheStatsHistory(dst, src *fastcache.Stats) {
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atomic.AddUint64(&dst.GetCalls, atomic.LoadUint64(&src.GetCalls))
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atomic.AddUint64(&dst.SetCalls, atomic.LoadUint64(&src.SetCalls))
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atomic.AddUint64(&dst.Misses, atomic.LoadUint64(&src.Misses))
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atomic.AddUint64(&dst.Collisions, atomic.LoadUint64(&src.Collisions))
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atomic.AddUint64(&dst.Corruptions, atomic.LoadUint64(&src.Corruptions))
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// Do not add EntriesCount, BytesSize and MaxBytesSize, since these metrics
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// are calculated from c.curr and c.prev caches.
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}
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// Get appends the found value for the given key to dst and returns the result.
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func (c *Cache) Get(dst, key []byte) []byte {
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curr := c.curr.Load().(*fastcache.Cache)
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result := curr.Get(dst, key)
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if len(result) > len(dst) {
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// Fast path - the entry is found in the current cache.
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return result
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}
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if c.loadMode() == whole {
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// Nothing found.
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return result
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}
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// Search for the entry in the previous cache.
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prev := c.prev.Load().(*fastcache.Cache)
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result = prev.Get(dst, key)
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if len(result) <= len(dst) {
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// Nothing found.
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return result
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}
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// Cache the found entry in the current cache.
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curr.Set(key, result[len(dst):])
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return result
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}
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// Has verifies whether the cache contains the given key.
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func (c *Cache) Has(key []byte) bool {
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curr := c.curr.Load().(*fastcache.Cache)
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if curr.Has(key) {
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return true
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}
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if c.loadMode() == whole {
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return false
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}
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prev := c.prev.Load().(*fastcache.Cache)
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if !prev.Has(key) {
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return false
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}
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// Cache the found entry in the current cache.
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tmpBuf := tmpBufPool.Get()
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tmpBuf.B = prev.Get(tmpBuf.B, key)
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curr.Set(key, tmpBuf.B)
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tmpBufPool.Put(tmpBuf)
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return true
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}
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var tmpBufPool bytesutil.ByteBufferPool
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// Set sets the given value for the given key.
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func (c *Cache) Set(key, value []byte) {
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curr := c.curr.Load().(*fastcache.Cache)
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curr.Set(key, value)
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}
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// GetBig appends the found value for the given key to dst and returns the result.
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func (c *Cache) GetBig(dst, key []byte) []byte {
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curr := c.curr.Load().(*fastcache.Cache)
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result := curr.GetBig(dst, key)
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if len(result) > len(dst) {
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// Fast path - the entry is found in the current cache.
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return result
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}
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if c.loadMode() == whole {
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// Nothing found.
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return result
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}
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// Search for the entry in the previous cache.
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prev := c.prev.Load().(*fastcache.Cache)
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result = prev.GetBig(dst, key)
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if len(result) <= len(dst) {
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// Nothing found.
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return result
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}
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// Cache the found entry in the current cache.
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curr.SetBig(key, result[len(dst):])
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return result
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}
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// SetBig sets the given value for the given key.
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func (c *Cache) SetBig(key, value []byte) {
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curr := c.curr.Load().(*fastcache.Cache)
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curr.SetBig(key, value)
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}
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func timeJitter(d time.Duration) time.Duration {
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n := float64(time.Now().UnixNano()%1e9) / 1e9
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return time.Duration(float64(d) * n)
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}
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