forked from grafana/loki
/
evicting_queue.go
93 lines (70 loc) · 1.51 KB
/
evicting_queue.go
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package util
import (
"errors"
"sync"
)
type EvictingQueue struct {
sync.RWMutex
capacity int
entries []interface{}
onEvict func()
}
func NewEvictingQueue(capacity int, onEvict func()) (*EvictingQueue, error) {
if err := validateCapacity(capacity); err != nil {
return nil, err
}
queue := &EvictingQueue{
onEvict: onEvict,
entries: make([]interface{}, 0, capacity),
}
err := queue.SetCapacity(capacity)
if err != nil {
return nil, err
}
return queue, nil
}
func (q *EvictingQueue) Append(entry interface{}) {
q.Lock()
defer q.Unlock()
if len(q.entries) >= q.capacity {
q.evictOldest()
}
q.entries = append(q.entries, entry)
}
func (q *EvictingQueue) evictOldest() {
q.onEvict()
start := (len(q.entries) - q.Capacity()) + 1
q.entries = append(q.entries[:0], q.entries[start:]...)
}
func (q *EvictingQueue) Entries() []interface{} {
q.RLock()
defer q.RUnlock()
return q.entries
}
func (q *EvictingQueue) Length() int {
q.RLock()
defer q.RUnlock()
return len(q.entries)
}
func (q *EvictingQueue) Capacity() int {
return q.capacity
}
func (q *EvictingQueue) SetCapacity(capacity int) error {
if err := validateCapacity(capacity); err != nil {
return err
}
q.capacity = capacity
return nil
}
func (q *EvictingQueue) Clear() {
q.Lock()
defer q.Unlock()
q.entries = q.entries[:0]
}
func validateCapacity(capacity int) error {
if capacity <= 0 {
// a queue of 0 (or smaller) capacity is invalid
return errors.New("queue cannot have a zero or negative capacity")
}
return nil
}