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least_loaded.go
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/
least_loaded.go
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// Copyright 2020 Douyu
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package leastloaded
import (
"math/rand"
"sync"
"sync/atomic"
"time"
"github.com/douyu/jupiter/pkg/util/xp2c"
"google.golang.org/grpc/balancer"
)
type leastLoadedNode struct {
item interface{}
inflight int64
}
type leastLoaded struct {
items []*leastLoadedNode
mu sync.Mutex
rand *rand.Rand
}
func New() xp2c.P2c {
return &leastLoaded{
items: make([]*leastLoadedNode, 0),
rand: rand.New(rand.NewSource(time.Now().Unix())),
}
}
func (p *leastLoaded) Add(item interface{}) {
p.items = append(p.items, &leastLoadedNode{item: item})
}
func (p *leastLoaded) Next() (interface{}, func(balancer.DoneInfo)) {
var sc, backsc *leastLoadedNode
switch len(p.items) {
case 0:
return nil, func(balancer.DoneInfo) {}
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 = b + 1
}
sc, backsc = p.items[a], p.items[b]
// choose the least loaded item based on inflight
if sc.inflight > backsc.inflight {
sc, backsc = backsc, sc
}
}
atomic.AddInt64(&sc.inflight, 1)
return sc.item, func(balancer.DoneInfo) {
atomic.AddInt64(&sc.inflight, -1)
}
}