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least_loaded.go
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/
least_loaded.go
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package p2c
import (
"math/rand"
"sync"
"sync/atomic"
"time"
"github.com/hnlq715/go-loadbalance"
"github.com/hnlq715/go-loadbalance/internal"
"google.golang.org/grpc/balancer"
)
type leastLoadedNode struct {
item interface{}
inflight int64
weight float64
}
type leastLoaded struct {
items []*leastLoadedNode
mu sync.Mutex
rand *rand.Rand
}
func NewLeastLoaded() loadbalance.Picker {
return &leastLoaded{
items: make([]*leastLoadedNode, 0),
rand: rand.New(rand.NewSource(time.Now().Unix())),
}
}
func (p *leastLoaded) Add(item interface{}, weight float64) {
p.items = append(p.items, &leastLoadedNode{item: item, weight: weight})
}
func (p *leastLoaded) Reset() {
p.items = p.items[:0]
}
func (p *leastLoaded) Next() (interface{}, func(balancer.DoneInfo)) {
var sc, backsc *leastLoadedNode
switch len(p.items) {
case 0:
return nil, internal.EmptyDoneFunc
case 1:
sc = p.items[0]
default:
// rand needs lock
p.mu.Lock()
a := p.rand.Intn(len(p.items))
b := p.rand.Intn(len(p.items) - 1)
p.mu.Unlock()
if b >= a {
b++
}
sc, backsc = p.items[a], p.items[b]
// choose the least loaded item based on inflight and weight
scInflight := atomic.LoadInt64(&sc.inflight)
backscInflight := atomic.LoadInt64(&backsc.inflight)
if float64(scInflight)*backsc.weight > float64(backscInflight)*sc.weight {
sc, backsc = backsc, sc
}
}
atomic.AddInt64(&sc.inflight, 1)
return sc.item, func(balancer.DoneInfo) {
atomic.AddInt64(&sc.inflight, -1)
}
}