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entry.go
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entry.go
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package lazy
import (
"errors"
"sync"
"sync/atomic"
"time"
"github.com/moderntv/lazy-cache/internal/utils"
)
type cachedEntry[T any] struct {
nextReload atomic.Int64 // timestamp of next reload in milliseconds
accessed atomic.Bool // true if entry data was accessed since last (re)load
value atomic.Pointer[T] // nil when not found
mu sync.Mutex
}
// set sets value and nextReload (when it make sense) and returns new TTL
// If TTL has negative value, it should be ignored (was not affected by this set)
func (e *cachedEntry[T]) set(value *T, err error, nowMillis int64, timeouts *Timeouts, init bool) (ttl time.Duration) {
ttl = -1
if err != nil {
// skip any error except NotFound
if !errors.Is(err, ErrNotFound) {
// in case of first load, set error TTL
if init {
ttl = utils.RandomizeDuration(timeouts.ErrorTTL, timeouts.Randomizer)
}
goto end
}
// when record is not found, we want to keep this information in cache for desired time
ttl = utils.RandomizeDuration(timeouts.NotFoundTTL, timeouts.Randomizer)
if e.value.Load() != nil {
e.value.Store(nil)
}
goto end
}
ttl = utils.RandomizeDuration(timeouts.TTL, timeouts.Randomizer)
e.value.Store(value)
// set `accessed` and `nextReload` every time and AFTER value is stored
// (if they are set before `value`, cache can in some circumstances read old value
// because it seems that entry value was updated)
end:
if e.accessed.Load() {
e.accessed.Store(false)
}
e.nextReload.Store(nowMillis + utils.RandomizeDuration(timeouts.ReloadInterval, timeouts.Randomizer).Milliseconds())
return
}
func (e *cachedEntry[T]) get() *T {
if !e.accessed.Load() {
e.accessed.Store(true)
}
return e.value.Load()
}
// func (e *cachedEntry[T]) memSize() uint64 {
// value := e.value.Load()
// if value == nil {
// return 0
// }
// return memsize.Entry(value)
// }