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repartition.go
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repartition.go
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package node
import (
"container/list"
"sync"
"time"
)
// RepartitionResolver is implemented to support repartition when item added or removed
// in the consistent hash ring.
type RepartitionResolver interface {
Get(key uint64) (string, bool)
Put(key uint64, value string)
}
type noopRepartitionResolver struct{}
func (r *noopRepartitionResolver) Get(key uint64) (string, bool) { return "", false }
func (r *noopRepartitionResolver) Put(key uint64, value string) {}
type partitionInfo struct {
key uint64
node string
deadline time.Time
}
type SimpleRepartitionResolver struct {
key2Items sync.Map
items *list.List
ttl time.Duration
mu sync.Mutex
}
func NewSimpleRepartitionResolver(ttl time.Duration) *SimpleRepartitionResolver {
return &SimpleRepartitionResolver{
items: list.New(),
ttl: ttl,
}
}
func (r *SimpleRepartitionResolver) Get(key uint64) (string, bool) {
value, ok := r.key2Items.Load(key)
if !ok {
return "", false
}
r.mu.Lock()
defer r.mu.Unlock()
item := value.(*list.Element)
info := item.Value.(partitionInfo)
now := time.Now()
// passively check expiration
if info.deadline.Before(now) {
r.items.Remove(item)
r.key2Items.Delete(key)
return "", false
}
// update expiration
info.deadline = now.Add(r.ttl)
item.Value = info
r.items.MoveToBack(item)
return info.node, true
}
func (r *SimpleRepartitionResolver) Put(key uint64, value string) {
r.mu.Lock()
defer r.mu.Unlock()
r.gc()
info := partitionInfo{
key: key,
node: value,
deadline: time.Now().Add(r.ttl),
}
if value, ok := r.key2Items.Load(key); ok {
// update item value
item := value.(*list.Element)
item.Value = info
r.items.MoveToBack(item)
} else {
// add new item
item := r.items.PushBack(info)
r.key2Items.Store(key, item)
}
}
// gc removes the expired items.
func (r *SimpleRepartitionResolver) gc() {
now := time.Now()
for {
front := r.items.Front()
if front == nil {
break
}
info := front.Value.(partitionInfo)
if info.deadline.After(now) {
break
}
r.items.Remove(front)
r.key2Items.Delete(info.key)
}
}