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load_balance.go
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/
load_balance.go
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/*
* Copyright 2022 CECTC, Inc.
*
* 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 lb
import (
"bytes"
"context"
"fmt"
"math/rand"
"strings"
"time"
"github.com/pkg/errors"
"go.uber.org/atomic"
)
var counter = atomic.NewInt64(0)
type LoadBalanceAlgorithm int32
const (
Random LoadBalanceAlgorithm = iota
RoundRobin
RandomWeight
)
func (l *LoadBalanceAlgorithm) UnmarshalText(text []byte) error {
if l == nil {
return errors.New("can't unmarshal a nil *ProtocolType")
}
if !l.unmarshalText(bytes.ToLower(text)) {
return fmt.Errorf("unrecognized protocol type: %s", text)
}
return nil
}
func (l *LoadBalanceAlgorithm) unmarshalText(text []byte) bool {
alg := string(text)
if strings.EqualFold(alg, "Random") {
*l = Random
return true
}
if strings.EqualFold(alg, "RoundRobin") {
*l = RoundRobin
return true
}
if strings.EqualFold(alg, "RandomWeight") {
*l = RandomWeight
return true
}
return false
}
type Weighting interface {
Counting() bool
Weight(ctx context.Context) int
}
type Interface interface {
Add(Weighting)
Next(ctx context.Context) Weighting
}
type RandomAlgorithm struct {
items []Weighting
}
func (r *RandomAlgorithm) Add(item Weighting) {
r.items = append(r.items, item)
}
func (r *RandomAlgorithm) Next(ctx context.Context) Weighting {
var items []Weighting
for _, item := range r.items {
if item.Counting() {
items = append(items, item)
}
}
total := len(items)
index := rand.New(rand.NewSource(time.Now().UnixNano())).Intn(total)
return items[index]
}
type RoundRobinAlgorithm struct {
items []Weighting
}
func (r *RoundRobinAlgorithm) Add(item Weighting) {
r.items = append(r.items, item)
}
func (r *RoundRobinAlgorithm) Next(ctx context.Context) Weighting {
var items []Weighting
for i := 0; i < len(r.items); i++ {
item := r.items[i]
if item.Counting() {
items = append(items, item)
}
}
total := len(items)
counter.Add(1)
count := counter.Load()
index := count % int64(total)
return items[index]
}
type RandomWeightAlgorithm struct {
items []Weighting
}
func (r *RandomWeightAlgorithm) Add(item Weighting) {
r.items = append(r.items, item)
}
func (r *RandomWeightAlgorithm) Next(ctx context.Context) Weighting {
var (
items []Weighting
totalWeight = 0
weightSum = 0
)
for i := 0; i < len(r.items); i++ {
item := r.items[i]
if item.Counting() {
items = append(items, item)
totalWeight += item.Weight(ctx)
}
}
index := rand.New(rand.NewSource(time.Now().UnixNano())).Intn(totalWeight)
for i := 0; i < len(items); i++ {
if index >= weightSum && index < weightSum+items[i].Weight(ctx) {
return items[i]
}
weightSum += items[i].Weight(ctx)
}
return nil
}
func New(alg LoadBalanceAlgorithm) (Interface, error) {
switch alg {
case Random:
return &RandomAlgorithm{}, nil
case RoundRobin:
return &RoundRobinAlgorithm{}, nil
case RandomWeight:
return &RandomWeightAlgorithm{}, nil
default:
return nil, errors.Errorf("unsupported load balance algorithm %d", alg)
}
}